The pine twigs which were present in the F₁ sample were about 2½-yr-old and probably fell during previous winter. Two features must be highlighted. First, decay was in an advanced stage, under the joint activity of animals and fungi. Second, basidiomycetes, which had not been observed in pine twigs in the two overlying layers, now invaded all twigs found in F₁. For some of them, this was also the case for the ascomycete *Cenococcum geophilum*.

Decay processes observed in bark and wood seemed quite independent of each other, thus they will be studied apart although these superposed tissues pertained to the same twig fragments.

## Wood

* Penetration by basidiomycetes without any attack of lignified walls

I observed several fungi at the inside of tracheids: a basidiomycete with thin smooth hyphae, which could be *Hyphodontia sp.* (associated with orange-brown mycorrhizae), a basidiomycete with smooth larger hyphae, which could be the one associated with pink mycorrhizae, and *Cenococcum geophilum*. Previous infestations were attested by the presence of empty melanised hyphae in vascular rays, a stage of fungal succession which was described in L₁ (Fig. 37), and pycnidia and acervuli in the peripheral bark.

* Penetration by fungi and bacteria with soft-rot attack

About half of the studied twigs showed signs of soft-rot attack, as attested by typical features (Fig. 252) which have been described by many authors (Bailey & Vestal, 1937; Courtois, 1963; Corbett & Levy, 1963; Corbett, 1965; Casagrande & Ouellette, 1971; Nilsson, 1973, 1974). Cavities were formed in cell walls of metaxylem tracheids, following the orientation of fibres, optically crossing at acute angle between adjacent tracheids (Fig. 252). Constricted micro-hyphae were sometimes observed out of abovementioned cavities. Some wood microbiologists asked why cavities were preferentially formed in some places, not in others. The answer lies in structural irregularities of tracheid walls, as exemplified in Figure 253, showing a portion of pine twig wood still not attacked by soft-rot fungi: micro-fibres (not visible at the used magnification) are assembled in fascicles, which are separated from each other at some places, and are joined at others. I hypothesize that soft-rot fungi preferentially used these open spaces for initiating the formation of cavities through external enzymic activity.

Pine twigs which exhibited features of soft-rot attack showed also an abundant development of other microorganisms, such as the three 'mycorrhizal' fungi already noted in the absence of soft-rot, and many bacteria which coexisted with fungi in the lumen of tracheids (Fig. 253). No faunal activity was registered at the inside of pine twigs, thereby indicating some delay in their decomposition, when compared with needles.
<figure><img src="image_37.png" /><figcaption>Fig. 253: Decaying pine twig, longitudinal section showing fungi and bacteria at the inside of wood tracheids (BMSL); Fig. 254: Idem, showing cortical tissues invaded by a fungus forming white rhizomorphs (CP); Fig. 255: Idem, showing a micro-site with bacteria in bark (CP); Fig. 256: Idem, showing the pseudoparenchyma of *Cenococcum geophilum* at the surface of bark (CP); Fig. 257: Idem, optical section of a thin bark fragment showing the mycelium of *Cenococcum geophilum* embedding it (CP); Fig. 258: Idem, section in a thick bark fragment showing bacterial development in a bark crevice (CP); Fig. 259: Idem, section showing holes of fungal origin in a cell wall piece (arrow) (CP); Fig. 260: Pine seed wing, optical section showing intracellular fungal hyphae (stained blue) and pigment deposits (opaque to natural light) (BMSL)</figcaption></figure>

CP = phase contrast; BMSL = methyl blue-Sudan III-lactophenol coloration; length of segment = 50 µm
## Bark

White rhizomorphs were often observed protruding from the bark of pine twigs. When sectioned (Fig. 254), cortical tissues appeared invaded by an unidentified fungus and host cells were transformed into a pulp, quite similar to pine needles penetrated by *Marasmius androsaceus* (Fig. 80). Only resin subsisted within this cellular pulp, in which limits of fungal cells were hardly visible. Despite of the fact that clamp connections were not observed, the basidiomycete nature of the fungus was highly probable.

Numerous micro-sites harboured bacterial colonies (Fig. 255). Protozoa, in particular cyst amoebae such as *Nebela collaris*, were frequently observed in micro-sites colonised by bacteria.

Pine twig bark was the seat of an intense activity of box mites [*Rhysotritia duplicata* (Michael), *Phthiracarus* sp., see below the chapter devoted to fauna], which deposited their faeces either in surface cavities (directly visible from the outside) or at the inside of bark tissues (visible only in sections). Enchytraeid faeces accumulated between bark and wood: their microscopic observation revealed the presence of pieces of resin, as this had been already observed in L₂ (Figs. 125, 147 & 163). Enchytraeids did not seem to be able to tunnel through bark, which was probably tough, too much for their soft mouth parts, limiting their penetration to liber and spaces between bark layers. Rotifers were found in the midst of enchytraeid faeces accumulated between bark and wood, but the observation of their gut contents did not reveal any other items than their intestinal microflora (Fig. 291).

The surface of bark was often covered by a dense network of melanised hyphae of *Cenococcum geophilum*, which in some places may form a pseudoparenchyma (Fig. 256), quite similar to the mantle of jet-black ectomycorrhizae.

Contrary to wood, the bark of pine twigs was the seat of an intense bacterial and faunal activity.

## Pine bark

### Notice

Pine bark means fragments of bark which fell detached from trunk of branches of pine, not bark still present around pine twigs, which had been studied above.

### Thin bark fragments
These fragments correspond to the detachment of stem epidermis, which may fall on the ground together with some bark sheets still attached to it. They were characterised by the development of the mycelium of *Cenococcum geophilum* (Fig. 257), or that of *Hyphodontia sp.*, which embedded them in a fungal 'mantle', but the internal development of these fungi was never observed. Traces of previous fungal development were still visible (pycnidia, acervuli) but these fructifications were empty and could not be used to identify previous colonisers. However, I want to notice the presence of a melanised imperfect fungus with septate conidiophores and numerous dictyospores (septate conidia), which could be *Spadicoides xylogenum* (A.L. Smith) (Roquebert, personal communication). Below this fungus 'mantle' and in crevices of bark layers there was an intense bacterial development (Fig. 258).

Some bark fragments were covered with mucus, let after the passage of slugs or earthworms. Mucus was strongly transformed, showing numerous senesced or dead fungal hyphae (Fig. 281) and bacteria (Fig. 282). Naked amoebae were also often observed. Mucus was embedded in the abovementioned fungal network, a feature indicating its ancientness. Earthworm faeces (type C) were also observed tightly appressed against bark pieces. White rhizomorphs were present in contact with bark, but no penetration was observed, contrary to pine twigs.

No sign of biological activity (whether faunal or microbial) was found at the inside of thin bark pieces (when sectioned), contrary to surface (in particular mucus deposits) and crevices.

## Thick bark fragments

An intense bacterial development was observed at the surface, quite similar to that observed on thin bark pieces. Bacteria were never found at the inside but traces of past fungal activity were still present. Cell walls were degraded, only debris being visible, with ancient holes due to the passage of fungal hyphae (Fig. 259). This was reminiscent of soft-rot activity, although this term was used only for wood. Dead and living hyaline hyphae were present, as ascertained by phase contrast (Frankland, 1974). More often, pieces of resin were still present among remnants of pulverised debris of ancient suberised cell walls.

It could be questioned why bacteria were so abundant at the surface of bark pieces and in bark crevices and were near absent at the inside of the same fragments. It is possible that resin and other chemical compounds which impregnate bark exert an antibiotic activity against bacteria but are tolerated by some fungal strains. Updegraff & Grant (1975) showed that, among 200 microbial strains isolated from the bark of *Pinus radiata* after previous enrichment, only 36 fungi imperfecti were able to grow on culture medium added with bark extract. Most of these fungi were able to degrade phenolic compounds which comprised a prominent part of bark (39% dry weight for phenolic acids, 60% when all ethanol-extractable compounds are taken into account). Not any bacteria or yeast was able to grow in such conditions.

## Pine euphylls
Most euphylls showed zones browsed by fauna, with oribatid mite faeces deposited at their surface, thereby indicating the animal group responsible for faunal attacks. The microscopic examination of these faeces indicated that euphylls had been ingested. The epidermis was often the only remnant of euphyll tissues observed in browsed areas. The three 'ectomycorrhizal' fungi which had been repeatedly observed embedding decaying plant material were present as hyphae running at the surface of pine euphylls. Apart from their local consumption by oribatid mites, pine euphylls found in $F_1$ did not differ to a great extent from those found in $L_2$ (Figs. 113 & 114), which was probably due to their penetration through $L_1$ and $L_2$ till $F_1$. This might indicate that the fact that this substrate was ingested by animals in $F_1$ but not in $L_2$ was not due to insufficient conditioning by microflora in $L_2$ but rather to ecophysiological requirements of soil invertebrates, which were only fulfilled in the deeper $F_1$ layer where most of them were living (see Table 8 and compare with Tables 3 & 5).

## Male flowers of pine

Most flowers and pollen grains found in $F_1$ were seemingly intact or only poorly decayed. In particular, pollen grains, which were often aggregated, were devoid of any bacteria or fungi. This was probably due to their drop through $L_1$ and $L_2$, as for pine euphylls. Most flower bracts showed cells with strong granulation but some cells were penetrated by tiny fungal hyphae, indicating incipient fungal colonisation. Such bracts starting to decay were generally embedded in an abundant fungal mycelium, at the inside of which bacteria were seen, but no bacterial development was seen at the inside of bracts.

It should be noticed that many pollen grains were observed at the inside of type C (earthworm) faeces, indicating that the activity of these animals in the $F_1$ layer mainly took place in last spring-early summer (June-July). On the contrary, pollen grains were not observed in faeces of type A (slugs?) and B (woodlice?), the deposition of which occurred probably in winter or early spring.

## Miscellaneous pine material

Other pine remains were found in $F_1$, although only in weak amounts. Among them, bud scales most probably dropped through overlying moss and pine needles after they fell in April-May. Such tender material was nibbled by oribatids, which deposited their faeces below the external epidermis which subsisted after consumption of more tender tissues.

Pine seeds were also found. They were probably dispersed by wind, since no female cone of fragment of cone was found in their vicinity. Only seed tegument was still present, the albumen being entirely ingested by fauna. The microscopic observation of the tegument was made difficult by the presence of opaque brown-red pigments in some cells. The internal surface of the tegument was covered by numerous bacteria and actinomycetes. The very fine seed wing (made of a monocellular layer) could be observed by transparency and showed a network of intracellular fungal hyphae, some of them were senescent (Fig. 260).
## Leafy shoots of moss (*Pseudoscleropodium purum*)

### Preliminary remarks

Moss stems and leaves were always abundantly covered by a mixed mycelium made of hyaline encrusted hyphae of *Hyphodontia sp.* and melanised hyphae of *Cenococcum geophilum*, the latter fungus being sometimes observed alone.

### Leaves

* Attack of soft-rot type

Thin elongated moss cells were invaded by fungal hyphae (without any clamp connection) which often filled them near entirely (Fig. 261). They were connected from a cell to another by micro-hyphae. This stage of fungal colonisation evolved either towards (i) a bacterial attack of fungal hyphae, the cytoplasm of which disappeared (lack of methyl blue staining), most cells being invaded by numerous bacterial rods (Fig. 262), or (ii) fragmentation and condensation of fungal cytoplasm (Fig. 263). The attack of moss cell walls was particularly visible when they were thicker (Fig. 264).

* Attack of white-rot type

Moss cells were invaded by basidiomycetous hyphae with clamp connections. Moss cell walls were thinned and became highly transparent (Fig. 265). No bacterial development was visible. Under the dissecting microscope, such leaves seemed strongly transformed, having lost rigidity and planar form.

From the beginning of the study, this was the first time moss cell walls appeared to be microbially attacked. However, it must be noticed that at this stage most leafy shoots of moss had lost their leaves, which had been ingested by fauna, leaf insertions still remaining well visible along stems. In this case, the decay of moss leaves followed another processing chain (see below, studies on fauna).

### Stems
<figure><img src="image_38.png" /><figcaption>Fig. 261: Decaying moss leaf, detail showing fungal hyphae filling the inside of cells (BMSL); Fig. 262: Idem, showing cells invaded by rod bacteria (BMSL); Fig. 263: Idem, showing fragmentation and condensation of fungal cytoplasm (BMSL); Fig. 264: Idem, showing the irregular attack of moss cell walls (BMSL); Fig. 265: Idem, showing continuously thinned transparent cell walls and basidiomycetous hyphae at the inside (BMSL); Fig. 266: Decaying moss stem, detail showing dead (empty) basidiomycetous hyphae at the inside of moss cells (CP); Fig. 267: Idem, showing a living basidiomycetous hypha penetrating a moss cell through a pit (CP); Fig. 268: Idem, showing cysts of naked amoeba at the inside of moss cells (CP)</figcaption></figure>

CP = phase contrast; BMSL = methyl blue-Sudan III-lactophenol coloration; length of segment = 50 µm
* Notice

The internal anatomy of moss stems, which I studied through the observation of sections, showed an external layer of thick-walled cells, of collenchyma type, ensuring rigidity of the stem. The internal parenchyma was made of cells with much thinner walls. Pits corresponding to local thinning of the wall were observed (Figs. 267 & 269). A variety of decay stages of stem parenchyma could be observed in the F₁ layer.

* Cells with cell contents still present

The content of parenchymatous cells was granular, sometimes displaying remains of chloroplasts. This resembled what had been observed at the inside of male flower bracts. This was probably due to an autolytic process without any microbial involvement, at least at the beginning. However, it must be noticed that at this incipient stage cell walls became brown in the central part of the stem.

* Penetration of fungal hyphae

Moss stems were penetrated by basidiomycetes, the presence of which was attested, most often by empty fungal hyphae (Fig. 266), but sometimes hyphae were still living at the time of sampling, passing from a cell to another through pits, i.e. circular zones where the wall of moss cells was much thinner (Fig. 267). Moss cell contents (granulation) disappeared following fungal colonisation but at this stage walls did not seem to be affected at all. This decay stage might coexist with the previous stage, either in another part of the same stem or in the same part but in different cells. Living fungal hyphae were only found in the latter case, pointing to a succession between both stages even though all cells or stem parts did not evolve to the same rate. From their diameter and ramification type, basidiomycetous hyphae resembled those of the pink mycorrhizal fungus, but without any due certitude, morphological convergence being possible in the absence of more specific characters.

* Penetration of microfauna

Several types of microfauna were seen at the inside of internal parenchymatous tissues of moss stems. Their penetration was made possible through the numerous breaks caused by the activity of macrofauna. The presence of numerous type C (earthworm) faeces appressed against stem fragments and the abundance of moss material within them showed that the ingestion of moss by earthworms was prominent at this stage. Nematodes (bacteriophagous Plectidae were identified) were
observed in the central lumen and cells were penetrated by naked amoebae, the presence of which was
attested by cysts (Fig. 268) and trophozoits (Fig. 269). It is possible that pits could be used by these
tiny animals to pass from a cell to another, like fungi did (Fig. 267), but this was not supported by any
definite observation. The colonisation of moss stems by microfauna was accompanied by bacterial
(Fig. 270) and algal (cyanobacterial) development (Fig. 271) at the inside of parenchymatous cells.
These stems, when observed under a dissecting microscope, exhibited a definite change of colour,
passing from yellow to red, which could not be perceived on mounted sections. It should also be
noticed that the penetration of hyphae of *Cenococcum geophilum* was observed in the central lumen of
some decaying stems.

* Hollow moss stems

Some stems exhibited the total disappearance of their parenchymatous tissues, probably
because they had been ingested by microfauna or mesofauna, but no deposition of faeces was
observed, letting the question unsolved. Only the external layer of thick-walled cells remained intact,
taking a brown colour which was well visible on the slides. Some remnants of parenchymatous cells
were still attached to the internal side of this tough tissue. A rhizomorph-like fungal tissue, made of
cemented empty hyphae, was often observed. Stems belonging to this decay stage were typically light-
brown and transparent.

* Concluding remarks

There was an analogy between successional stages observed during the decay of moss stems
and those of pine needles, although the former process seemed to be delayed and condensed: the whole
variety of decay stages observed on pine needles from L₁ to F₁ were observed on moss stems in the
only F₁ layer. Rather than a succession from canopy fungi colonising senescent needles
(*Lophodermium pinastri*) to litter-dwelling saprophytes colonising dead needles (*Verticicladium trifidum*),
‘ectomycorrhizal’ basidiomycetes arrived directly at the inside of dead moss stems. The
external collenchyma-like supporting tissue played a role similar to the epidermis-hypodermis external
envelope of pine needles, allowing these ‘tubes’ to be voided by soil animals before complete
disappearance. In both cases, bacterial development followed penetration by fauna and played only a
secondary role in decomposition, at least concerning the physical disappearance of plant material.

## Bracken fronds (*Pteridium aquilinum*)

*Bracken leaflets*
<figure><img src="image_39.png" /><figcaption>Fig. 269: Decaying moss stem, detail showing a trophozoit of naked amoeba (CP); Fig. 270: Idem, showing bacterial development (CP); Fig. 271: Idem, showing development of Cyanophyceae (CP); Fig. 272: Decaying bracken leaflet, detail showing upper epidermis still subsisting between veins (CP); Fig. 273: Idem, showing bacterial development in epidermal and stomatal guard cells (BMSL); Fig. 274: Idem, showing empty fungal hyphae (CP); Fig. 275: Idem, showing melanised hyphae of *Cenococcum geophilum* penetrating epidermal cells (LN); Fig. 276: Idem, showing lack of melanisation (LN)</figcaption></figure>

CP = phase contrast; BMSL = methyl blue-Sudan III-lactophenol coloration; LN = natural light without coloration; length of segment = 50 µm
Most leaflets were reduced to their network of veins, with the upper epidermis often subsisting (Fig. 272). This resulted from the browsing activity of fauna, as attested by the deposition of faeces of oribatid mites, as will be seen below. In some particular cases, leaflet limbs were still preserved: this was the case when several leaflets were tightly packed in bundles into which they were firmly appressed against each other. It can be hypothesized that in this case some leaflets were out of reach of soil animals, in particular of mesofauna. More generally, decaying leaflets or bundles of leaflets were embedded in a mycelial weft formed by 'ectomycorrhizal' fungi, in particular encrusted hyphae of *Hyphodontia sp.* Abundant and varied microfauna were observed at the surface of bracken leaflets: nematodes, naked amoebae, cyst amoebae. Observations on the internal colonisation were made by transparency, without any need to section bracken leaflets. Two decay stages were observed, independently of the consumption of leaflet limbs by soil invertebrates.

* Bacterial stage

Epidermal and stomatal guard cells were invaded by bacterial colonies (Fig. 273). Previous colonisation by fungi was attested by the presence of empty hyphae (Fig. 274).

* *Cenococcum* stage

This fungus, which normally pertained to the mycelium embedding leaflets, in the company of *Hyphodontia sp.*, was seen penetrating epidermal cells (Figs. 275 & 276). The penetration of plant cells was accompanied by partial (Fig. 275) or total (Fig. 276) lack of melanisation. This morphological change of melanised hyphae was even more pronounced than during the colonisation of pine needles (Figs. 237 & 238) where host cells were not penetrated at all by this fungus. Haustoria (enlarged hyphae) were always formed before crossing a plant cell wall (Figs. 275 & 276). Other fungi were also observed in the company of *Cenococcum geophilum*, in particular an unidentified basidiomycete with clamp connections.

## *Rachises*

Only fragments of secondary and tertiary rachises were found in the studied sample, without any true petiole (primary rachis). However, given that decay patterns did not differ in all fragments studied, whatever their size, it is highly probable that results of the present study may apply to bracken petioles, too. I always observed the partial or total disappearance of parenchyma, due to the intense tunnelling activity of mesofauna, as attested by their gut contents (see below). Microfauna were observed on plant sections, in particular the cyst amoebae *Corythion dubium*, and to a lesser extent *Nebela collaris*. Numerous cysts of protozoa were also observed. Invertebrate activity was characterized by the formation of cavities, in which animals were still present, together with plant and
fungal cell remains invaded by bacteria. Outside cavities, the parenchyma was invaded by bacteria (Fig. 277) and other microorganisms (algae, fungi?) which could not be identified (Fig. 278). Plant cell walls showed signs of ancient fungal attacks of soft-rot type (Fig. 279). Scalariform tracheids showed empty hyphae of the same basidiomycete described in L₂ (Fig. 143). The inner part of bracken rachises, often totally excavated by fauna, was colonised by the three 'ectomycorrhizal' fungi, *Cenococcum geophilum*, *Hyphodontia sp.* and the basidiomycete with wide hyphae which was associated with pink ectomycorrhizae. The latter fungus was also observed at the inside of scalariform tracheids, although it had not been observed in pine tracheids, maybe due to their much thinner section.

## Birch (Betula pubescens Ehrh.)

Plant material of birch origin was but poorly represented: it was comprised of seeds (achenes) and small fragments of foliar limbs.

### Leaves

Fragments of foliar limbs were thinned down and discoloured. Veins were intact, as well as the upper epidermis. Other leaf tissues had disappeared, probably eaten by invertebrates, to the exception of some remnants of palissadic parenchyma. Stomata were scarcely encountered, since most of them pertained to the lower epidermis, which has been lost (consumed). Traces of past intense fungal development were observed in the epidermis and in parenchymatous remains, in the form of empty hyphae and fructifications (ascocarps? pycnidia?) nibbled by fauna. Bacteria were present but not abundant. Birch leaf fragments were embedded by 'ectomycorrhizal' fungi in the same way as other plant litter debris. It seemed that the decomposition of birch leaves was arrested (when not consumed by fauna) at a stage where plant and fungal cytoplasm had totally disappeared but cell walls still remained untouched.

### Achenes

Some achenes seemed intact and were probably viable. Others showed signs of recent fungal attacks (little penetration, living hyphae). From these features I hypothesized that birch achenes fell recently to the ground and rapidly crept down to the F₁ layer under the influence of summer rains. Decay of achenes started by the development of hyaline and melanised hyphae (*Cenococcum geophilum*) at the surface of the wings (Fig. 280). When sectioned, some seeds showed a few melanised hyphae (*Cenococcum geophilum?*) but bacteria were never found.
<figure><img src="image_40.png" /></figure>

Fig. 277: Bracken rachis, section showing parenchyma invaded by bacteria (CP); Fig. 278: Idem, showing unidentified microorganisms in parenchymatous cells (CP); Fig. 279: Idem, showing ancient soft-rot type attacks of plant cell walls (arrow = living micro-hypha in transversal section, stained blue) (BMSL); Fig. 280: Birch achene, hyaline hyphae of fungi imperfecti and melanised hyphae of *Cenococcum geophilum* at the surface of seed wing (BMSL); Fig. 281: Mucus, detail showing living hyaline hyphae (CP); Fig. 282: Idem, showing pullulating bacteria in the peripheral part of mucus deposit (CP); Fig. 283: Idem, zone with melanised hyphae (CP); Fig. 284: Idem, hyaline hyphae in way to be degraded (CP)

CP = phase contrast; BMSL = methyl blue-Sudan III-lactophenol coloration; length of segment = 50 µm
Mucus

Preliminary remarks

Mucus was deposited either by slugs or by earthworms against a piece of plant material (more generally pine bark), along which animals crept. Mucus deposits where the seat of intense microbial development, but two stages were identified. In every case, they were embedded in melanised hyphae of *Cenococcum geophilum* (most often with encrusted walls as in Figure 242) and in hyaline hyphae of *Hyphodontia sp*. Many bacteria and green algae (Chlorophyceae) were seen at the surface of mucus deposits.

Fungal development

This fungus could not be identified, since it did not resemble any of the other mycelia found in the studied profile. Its irregular hyaline hyphae formed a dense felt (Fig. 281). They were living, as attested by their opacity in phase contrast. At the inside of this felt, there were zones where hyphae of the same fungus became melanised and fragmented, indicating incipient sporulation (Fig. 283). Bacteria pullulated in the peripheral part of mucus deposits (Fig. 282).

Decay of the fungus

Hyphal contours became fuzzy and fungal cytoplasm lost its opacity under phase contrast (Fig. 284). Echinulate arthrospores accumulated in melanised zones (Fig. 285). At this stage, mucus deposits were colonised by hyphae of *Cenococcum geophilum* and the whole material was invaded by bacteria (Fig. 285). However, it must be noticed that dense networks of decaying hyaline hyphae (Fig. 284) remained devoid of bacteria. I suggest that the incipient decay of hyaline hyphae was the result of an autogenic process and thus was not microbially mediated: bacterial invasion occurred only after fungal death. Mucus seemed an attractive, although selective substrate for microorganisms.

Rhizomorphs

White rhizomorphs were also observed protruding from bark fragments, twigs, and macroinvertebrate faeces. In transversal section (Fig. 286) no differentiation appeared between external and internal hyphae, contrary to brown rhizomorphs of *Marasmius androsaceus* in L₂ (Fig. 79). The presence of clamp connections and oxalic-acid excreting cystidia of particular form (Fig. 287) allowed identifying this fungus as *Odontia bicolor* (Alb. & Schwein.) according to Nobles (1953, 1965). Given that
<figure><img src="image_41.png" /><figcaption>Fig. 285: Mucus, detail showing arthrospores, melanised encrusted hyphae of *Cenococcum geophilum* and bacteria (CP); Fig. 286: White rhizomorph protruding from pine bark, transversal section (CP); Fig. 287: Rhizomorph of *Odontia bicolor* with cystidia (arrow = cystidia having lost its oxalate crystals) (CP); Fig. 288: Spider silk cocoon (CP); Fig. 289: Shells of golden algae and bacteria carried on a springtail antenna (CP); Fig. 290: Trophozoit of naked amoeba in the mycelium embedding enchytraeid faeces (BMSL); Fig. 291: Cyst of *Phryganella acropodia* (Thecamoeba) in an enchytraeid intestine (CP); Fig. 292: Cyst of *Nebela collaris* (Thecamoeba) in an enchytraeid intestine</figcaption></figure>

CP = phase contrast; BMSL = methyl blue-Sudan III-lactophenol coloration; length of segment = 50 µm
cystidia and clamp connections were not found on rhizomorphs of similar aspect and anatomy, all white rhizomorphs present in the same sample cannot be attributed with certitude to *Odontia bicolor*. In the same way, hyphae of *Odontia bicolor* resembled to a great extent to the mycelium of pink mycorrhizae, but no connection was observed between both mycelia and no cystidia of similar morphology were found around the mycorrhiza, letting the problem unsolved.

## Quartz grains

Quartz grains were observed from place to place. Most of them were probably transported by soil animals. In comparison with L₂, more and bigger (sand size) quartz particles were found in F₁, thereby indicating prominent macrofaunal activity (mainly of earthworms). These grains were clean, indicating they provided mainly from the leached A₁₂ horizon (Table 1). No particular deposit was registered at the surface of quartz grains. Many sand grains were also present in animal faeces with mineral content as will be seen below.

## Spider cocoons

Wefts made of non-cellular threads without any microbial colonisation (Fig. 288) were interpreted as empty spider cocoons.

## Colonies of Chrysophyceae (golden algae)

I often observed gelatinous masses rich in bacteria, which revealed themselves, once mounted under a light microscope, to be palmelloid colonies of encysted golden algae or Chrysophyceae (Fig. 289). Each cyst was made of a rigid shell with a plug-like appendix. I was unable to identify them with certainty, but they probably pertained to primitive forms such as *Chrysapis* according to Hollande (1952). Such gelatinous masses were often encountered on the antennae of springtails, but cysts of golden algae were also found at the surface of pine bark fragments.

## Fauna

*Inventory*
Table 8 classifies all living specimens which were found free in the environment or after dissecting pine needles and miscellaneous debris. Nematodes (many specimens of which were found when sectioning plant material) and probably also rotifers were largely underestimated, as this has been already noticed. Protozoa were not searched for at all, although they were frequently encountered in microscopic slides. At last, some specimens of mesofauna were probably not recovered in entirety, such as oribatid box mites of the genus *Phthiracarus*, most larval development of which took place at

<table><caption>**Table 8.** Taxonomic name, abundance and estimated biovolume of living animals found in the F₁ layer</caption><thead><tr><th>Taxonomic groups and species</th><th>Abundance</th><th>Upper estimate of biovolume (µL)</th><th>Lower estimate of biovolume (µL)</th></tr></thead><tbody><tr><td>Rotifers</td><td>3</td><td>0.82 10<sup>-3</sup></td><td>0.21 10<sup>-3</sup></td></tr><tr><td>Nematodes</td><td>42</td><td>0.19 10<sup>-1</sup></td><td>0.49 10<sup>-2</sup></td></tr><tr><td>Eudorylaimus sp.</td><td>26</td><td>0.11 10<sup>-1</sup></td><td>0.29 10<sup>-2</sup></td></tr><tr><td>Prionchulus punctatus</td><td>10</td><td>0.8 10<sup>-2</sup></td><td>0.2 10<sup>-2</sup></td></tr><tr><td>Dorylaimus sp.</td><td>3</td><td>0.21 10<sup>-3</sup></td><td>0.52 10<sup>-4</sup></td></tr><tr><td>Anaplectus sp.</td><td>2</td><td>0.18 10<sup>-3</sup></td><td>0.44 10<sup>-4</sup></td></tr><tr><td>Cephalobus sp.</td><td>1</td><td>0.53 10<sup>-4</sup></td><td>0.13 10<sup>-4</sup></td></tr><tr><td>Enchytraeids</td><td>83</td><td>4.6</td><td>1.1</td></tr><tr><td>Oribatid mites</td><td>58</td><td>11</td><td>2.8</td></tr><tr><td>Rhysotritia duplicata</td><td>14</td><td>3.5</td><td>0.88</td></tr><tr><td>Phthiracarus sp.</td><td>10</td><td>7.2</td><td>1.8</td></tr><tr><td>Oppia subpectinata</td><td>9</td><td>0.17 10<sup>-1</sup></td><td>0.44 10<sup>-2</sup></td></tr><tr><td>Oppiella nova</td><td>7</td><td>0.57 10<sup>-2</sup></td><td>0.14 10<sup>-2</sup></td></tr><tr><td>Nothrus sylvestris</td><td>5</td><td>0.37</td><td>0.92 10<sup>-1</sup></td></tr><tr><td>Nanhermannia nana</td><td>3</td><td>0.3 10<sup>-1</sup></td><td>0.75 10<sup>-2</sup></td></tr><tr><td>Suctobelba subcornigera</td><td>3</td><td>0.16 10<sup>-2</sup></td><td>0.39 10<sup>-3</sup></td></tr><tr><td>Oppiidae (nymphs)</td><td>3</td><td>0.76 10<sup>-3</sup></td><td>0.19 10<sup>-3</sup></td></tr><tr><td>Oribatula tibialis</td><td>2</td><td>0.14 10<sup>-1</sup></td><td>0.35 10<sup>-2</sup></td></tr><tr><td>Ceratozetes sp.</td><td>1</td><td>0.18 10<sup>-2</sup></td><td>0.46 10<sup>-3</sup></td></tr><tr><td>Odontocephalus elongatus</td><td>1</td><td>0.58 10<sup>-2</sup></td><td>0.15 10<sup>-2</sup></td></tr><tr><td>Miscellaneous mites</td><td>38</td><td>0.41</td><td>0.1</td></tr><tr><td>Actinedida</td><td>17</td><td>0.18 10<sup>-1</sup></td><td>0.45 10<sup>-2</sup></td></tr><tr><td>Uropodina</td><td>9</td><td>0.76 10<sup>-1</sup></td><td>0.19 10<sup>-1</sup></td></tr><tr><td>Acaridida</td><td>7</td><td>0.26 10<sup>-2</sup></td><td>0.66 10<sup>-3</sup></td></tr><tr><td>Gamasina</td><td>5</td><td>0.31</td><td>0.77 10<sup>-1</sup></td></tr><tr><td>Spiders</td><td>1</td><td>0.1</td><td>0.26 10<sup>-1</sup></td></tr><tr><td>Woodlice</td><td>1</td><td>0.65 10<sup>-1</sup></td><td>0.16 10<sup>-1</sup></td></tr><tr><td>Trichoniscus sp.</td><td></td><td>0.65 10<sup>-1</sup></td><td>0.16 10<sup>-1</sup></td></tr><tr><td>Springtails</td><td>67</td><td>0.2</td><td>0.5 10<sup>-1</sup></td></tr><tr><td>Folsomia manolachei</td><td>23</td><td>0.28 10<sup>-1</sup></td><td>0.7 10<sup>-2</sup></td></tr><tr><td>Parisotoma notabilis</td><td>15</td><td>0.24 10<sup>-1</sup></td><td>0.61 10<sup>-2</sup></td></tr><tr><td>Pseudosinella terricola</td><td>8</td><td>0.92 10<sup>-1</sup></td><td>0.23 10<sup>-1</sup></td></tr><tr><td>Willemia anophthalma</td><td>8</td><td>0.31 10<sup>-2</sup></td><td>0.78 10<sup>-3</sup></td></tr><tr><td>Isotomiella minor</td><td>4</td><td>0.54 10<sup>-2</sup></td><td>0.14 10<sup>-2</sup></td></tr><tr><td>Lepidocryptus lanuginosus</td><td>4</td><td>0.26 10<sup>-1</sup></td><td>0.65 10<sup>-2</sup></td></tr><tr><td>Entomobrya sp.</td><td>2</td><td>0.71 10<sup>-2</sup></td><td>0.18 10<sup>-2</sup></td></tr><tr><td>Megalothorax minimus</td><td>2</td><td>0.21 10<sup>-2</sup></td><td>0.52 10<sup>-3</sup></td></tr><tr><td>Pogonognathellus flavescens</td><td>1</td><td>0.11 10<sup>-1</sup></td><td>0.28 10<sup>-2</sup></td></tr><tr><td>Fly larvae</td><td>14</td><td>1.4</td><td>0.36</td></tr><tr><td>Sciaridae</td><td>13</td><td>1.4</td><td>0.36</td></tr><tr><td>Cecidomyidae</td><td>1</td><td>0.16 10<sup>-2</sup></td><td>0.41 10<sup>-3</sup></td></tr><tr><td>Beetle larvae</td><td>1</td><td>0.14 10<sup>-1</sup></td><td>0.34 10<sup>-2</sup></td></tr><tr><td>Cantharidae</td><td>1</td><td>0.14 10<sup>-1</sup></td><td>0.34 10<sup>-2</sup></td></tr><tr><td>Fly nymphs</td><td>2</td><td>0.42</td><td>0.1</td></tr><tr><td>Insect imagos</td><td>1</td><td>0.47 10<sup>-2</sup></td><td>0.12</td></tr><tr><td>Thripsidae</td><td>1</td><td>0.47 10<sup>-2</sup></td><td>0.12</td></tr></tbody></table>
the inside of pine needles. Only part of pine material was dissected, letting this group underestimated,
too.

Within these limits, some comparisons could be done with overlying layers. Enchytraeids
were still the dominant group in number in F₁, like they were in L₂ (Table 5), but this was no longer
true in biovolume, because of the large size of box mites (*Phthiracarus sp.*, *Rhysotritia duplicata*), the
reason why oribatid mites became the dominant group in biovolume in F₁. Enchytraeids and oribatids
showed a contrasted evolution according to depth in the three studied litter layers. Enchytraeids
showed a continuous increase with depth in density (7, 39 then 83 specimens) and biovolume (0.22,
2.6 then 4.6 µL for the upper estimate), while oribatids showed a trough in L₂ both in density (46, 12
then 58 specimens) and biovolume (0.95, 0.092 then 11 µL), with a considerable shift in species
composition in F₁ (see below). The second more important group in density (although poorly
represented in biovolume) was Collembola (springtails). They were more and more numerous with
depth (9, 12 then 67 specimens). Although largely underestimated, nematodes increased in abundance
(1, 21 then 42 specimens). Fly larvae were a little more abundant in F₁ (14 specimens) compared to L₂
(12 specimens) but their biovolume dramatically increased (1.4 against 0.33µL) because of the lower
contribution of small-sized cecidomyids. More generally whole fauna increased with depth both in
density (76, 106 then 311) and biovolume (1.96, 3.4 then 18 µL), but also in diversity, in particular at
a lower taxonomic level.

Protozoa

This taxonomic group could not be explored in its entirety, because of its small size, transparency and
concealed way of life. However, many protozoa could be observed while sectioning and mounting
decaying plant material.

Trophozoits of naked amoebae were observed at the inside of decaying plant material, in
particular pine needles, but also at the inside of pine bark and moss stems (Fig. 269), and more rarely
at the surface of plant material (bracken leaflets, pine bark) and in the mycelium embedding plant
debris and enchytraeid faeces (Fig. 290). It should be noticed that naked amoebae seemed absent from
animal corpses.

Cyst amoebae (in the form of empty cysts or, more rarely, of living specimens) occupied a
variety of environments. They were frequently observed, both at the inside and at the outside of
decaying material. However, different thecamoeban species did not seem to occupy the same niches.
*Phryganella acropodia* (Fig. 291) was abundantly and exclusively found in arthropod corpses (mostly
in oribatid mites) while other abundant species, such as *Nebela collaris* (Fig. 292), *Euglypha sp.*, and
*Corythion dubium* (Fig. 293) colonised indifferently plant debris and corpses. It should be noticed that
*Nebela collaris* was most often seen at the inside of decaying plant material (pine needles, bracken
veins, bark). Other species, such as *Pseudodifflugia gracilis* var. *aerophila* Bonnet & Thomas, *Nebela
militaris* Penard, and *Trinema complanatum* var. *aerophila* (Decloître), were found too infrequently
for discerning their preferences. All these species were actively consumed by enchytraeids.

Among flagellates, colonies of chrysomonadins (also called Chrysophyceae or golden algae
when classified among algae), with many encysted specimens, were found on springtail antennae (Fig.
<figure><img src="image_42.png" /><figcaption>Fig. 293: Cyst of *Corythion dubium*, with bacterial colonies, at the inside of an enchytraeid intestine (CP); Fig. 294: Rotifer observed by transparency, showing its intestinal microflora (CP); Fig. 295: Enchytraeid gut contents observed by transparency, moss leaf fragments showing cell walls in way to be degraded (CP); Fig. 296: Idem, pine tracheid areolae in aggregates and empty basidiomycetous hyphae (CP); Fig. 297: Idem, hyaline hyphae in way to be degraded (CP); Fig. 298: Idem, oxalate crystals in aggregates, coming from hyphae of *Hyphodontia sp.* (CP); Fig. 299: Idem, bacterial colony in way to be degraded (CP); Fig. 300: Idem, cyst of *Trinema sp.* in way to be degraded</figcaption></figure>

CP = phase contrast; length of segment = 50 µm
289) and at the surface of pine bark. Gregarines were present in the form of dense masses of sporocysts at the inside of some living animals, in particular enchytraeids, but a gregarine colony was also observed at the inside of an arthropod leg (corpse). Infections by gregarines have been frequently observed in soil invertebrates and were well described by Purrini (1983).

Protozoan cysts, which could not be identified at a lower taxonomic level, were observed at the inside of decaying plant material, such as bracken veins and moss stems (Fig. 268).

### Rotifers

Although this group was but badly recovered in studied samples, rotifers were observed during sorting under the dissecting microscope (three specimens in enchytraeid faeces between bark and wood in a pine twig), in sections done in the decaying material (inside of a pine needle, surface of a type A excrement) and at the inside of a *Phthiracarus* corpse. The observation of gut contents did not reveal anything else than the intestinal microflora (Fig. 294), which was present in all collected specimens.

### Nematodes

Dorylaimidae (*Eudorylaimus* and *Dorylaimus*) were dominant. The same dominant group had been registered in L₂ (Table 5) but here much more specimens were collected, either under the dissecting microscope (26 specimens, against 8 in L₂) or under the light microscope (two specimens in arthropod corpses). The observation under phase contrast of dorylaimid intestines did not reveal any other contents than bacterial masses, often in way to be degraded (fuzzy contour, lack of opacity), thereby supporting what had been observed in L₂. The bacteriophagous behaviour of Dorylaimidae in an environment favourable to fungi is worth to notice, inasmuch as this group was not considered to have specialised food requirements (Arpin, personal communication). However, I cannot discard the possibility that they also used their buccal stylet to perforate fungal hyphae, swallowing bacteria being only part of their food habits.

The mononchid *Prionchulus punctatus* came in second position, both in density and in volume. I saw in its gut small more or less digested nematodes (*Cephalobus*, unidentified Tylenchinae) and chitinous fragments of unknown animal origin, thereby testifying for predatory activity (Arpin 1980). As in L₁ (Figs. 58-60), bacterial colonies in way to be degraded were observed in its gut, confirming observations in electron microscopy by Arpin & Kilbertus (1981), which established that the food habits of this 'predatory' nematode had a bacteriophagous component.

Other nematodes not indicated in Table 8, not found during scrutiny of the whole material under the dissecting microscope (and thus not measurable), were observed while mounting corpses during investigations in light microscopy: one Cephalobinae, one Acrobelinae and three unidentified specimens. A Tylenchinae (mycophagous species-group) was found appressed to the mantle of an orange-brown ectomycorrhiza which had been sectioned and stained.

Infestations of nematodes by bacteria and flagellates were observed, too.
## Enchytraeid worms

* Preliminary remarks

Enchytraeids were extremely abundant in the F₁ layer. In addition to entire specimens, many fragments, issued from the asexual reproduction of adults, were found. Fragmentation seems to be the rule in *Cognettia sphagnetorum* (Standen 1973), which was probably the dominant species in the studied site. Shortest specimens issued from fragmentation had not fully achieved their regeneration and thus were still starving. Over the 83 enchytraeid specimens studied, only 2 seemed to pertain to another species: they were slender, with a straight intestine, contrary to the dominant species (Figs. 145 & 146), and they harboured a different intestinal microflora.

* Generalities

The food diet of *Cognettia sphagnetorum* was highly variegated, although some choice could be evidenced. Table 9 shows the frequency of the 10 food categories which were found in the 61 non-starving specimens studied, expressed as per cent individuals showing the category in their intestine. Plant material (pine, moss, miscellaneous) was made of fragments of plant tissues, which may occupy a large volume in the intestine, while bacteria could be frequently ingested without making a significant contribution to the food bolus. Estimates of ingested volumes could not be done with means at my disposal, unfortunately. Within these limits, it can be said that the food diet of this species was shared between plant material (⅓ non-starving specimens had it in their gut) and microbial material (mainly fungi, bacteria to a weaker extent, algae still less present).

<table><caption>**Table 9.** Percent occurrence of main food categories ingested by *Cognettia sphagnetorum* in the F₁ layer</caption><thead><tr><td>Food categories</td><td>Frequency (%)</td></tr></thead><tbody><tr><td>Fungi</td><td>90</td></tr><tr><td>Bacteria</td><td>66</td></tr><tr><td>Plant material (pine)</td><td>34</td></tr><tr><td>Plant material (moss)</td><td>34</td></tr><tr><td>Cysts of Thecamoeba</td><td>31</td></tr><tr><td>Pine pollen grains</td><td>28</td></tr><tr><td>Quartz grains</td><td>8</td></tr><tr><td>Mesofaunal faeces</td><td>8</td></tr><tr><td>Algae (including cyanobacteria)</td><td>5</td></tr><tr><td>Miscellaneous plant material</td><td>3</td></tr></tbody></table>
Upon reading Table 9 it appeared that thecamoeban cysts (impossible to know whether cyst amoebae had been ingested dead or alive) and pollen exines (same incertitude as for cyst amoebae) were overrepresented in enchytraeid guts, and thus were probably actively searched in the environment. On the opposite side, animal faeces seemed neglected, at least those of mesofauna, the only ones which could be identified as such: plant material was poorly transformed in macrofaunal faeces, as will be seen below, thus it could not be distinguished from the material directly ingested by enchytraeids. However, it must be highlighted that enchytraeids were never found tunnelling through faeces of macroinvertebrates, while they abounded in pine needles, pine twigs and moss stems.

* Moss material

Moss tissues were frequently encountered in enchytraeid intestines, to the same extent as pine material, which was a novelty compared to the L₂ layer. It is worth to notice that moss material was consumed in L₁, where moss was living (green, meaning herbivory), was neglected in L₂, where moss was dead but with its internal tissues still not processed by fungi, and was consumed again in F₁, where moss cells were colonised by fungi and their walls attacked incipiently (microbivory and saprophagy). This can be explained if only cytoplasm (whether of plant or microbial origin) was attractive to these animals. Moss tissues observed by transparency in the gut of enchytraeids showed some degradation of cell walls, wall contours appearing fuzzy under phase contrast (Fig. 295). Fungal hyphae, which were present at the inside of moss cells (Figs. 266 & 267), were no longer visible. It can be suspected that enchytraeid worms were able to digest cytoplasmic contents, mainly responsible for attractiveness of food, but also fungal cell walls and, at least partly, moss cell walls. However, concerning the latter substrate, it should be highlighted that its attack has been largely prepared beforehand by fungi (see above) and thus is only in progress in enchytraeid intestines. Observations done in L₁ did not show any sign of attack of cell walls in the ingested moss fragments (Fig. 52).

* Pine tissues

Ingested tissues were of varying origin, as this had been already observed in L₂ (Figs. 161-163). The following tissues could be identified in F₁, thanks to their recalcitrant biochemical composition: epidermis, hypodermis, stomatal guard cells, tracheids with bordered pits, pieces of resin. Cell walls were still intact, except in cases where a severe microbial attack occurred before ingestion. Figure 296 shows an aggregation of areolae (from pitted cells of transfusion tissue) in the midst of a half-digested network of basidiomycetous hyaline hyphae. Given that the only recognizable remains of pine tissues were hard lignified structures, it is highly probable (but without any certitude) that enchytraeids were able to digest mesophyll cells and parenchymatous cells of transfusion tissue.

* Fungal material
Like in L₁ (Fig. 53) and L₂ (Figs. 148-153), enchytraeids ingested in F₁ a mixture of hyaline hyphae (mostly coming from basidiomycetous rhizomorphs and mycelia) and melanised hyphae (mostly from the ascomycete *Cenococcum geophilum*). Melanised hyphae seemed intact, except in abovementioned cases where they had been previously attacked by bacteria and fauna. However, hyaline material was always in way to be degraded (Fig. 297). During digestion, hyphal walls became thicker and took a fuzzy contour. In the case of *Hyphodontia sp.* associated with orange-brown ectomycorrhizae, hyphae of which were most often covered with minute oxalate crystals, aggregates of these crystals were observed, attesting for the total digestion of the hyaline fungal wall, to the exception of calcium oxalate (Fig. 298). It is thus highly probable that *Cognettia sphagnetorum* was able to digest fungal cell walls, to the exception of those impregnated with melanin.

* Bacteria

Bacterial colonies appeared in way to be degraded, according to current features observed under phase contrast such as fuzzy contours of their walls (Fig. 299).

* Thecamoeban cysts

Still intact cysts could be found in enchytraeid intestines (Figs. 291-293), but degradation patterns were observed in *Trinema sp.* (Fig. 300), *Euglypha sp.* (Fig. 301) and *Phryganella acropodia* (Fig. 302). In the latter case, quartz particles and miscellaneous debris, which were incorporated in the cyst, subsisted alone. Thorough scrutiny of the 63 specimens allowed attributing with certitude all quartz particles found in enchytraeid intestines to the digestion of cysts of *Phryganella acropodia* and not to the direct ingestion of mineral particles.

* Pine pollen

Pollen exine was sometimes still recognizable, in particular the sculptured exine of lateral bladders (Fig. 303), but most time only granular masses were observed (Fig. 304), indicating at least partial digestion of sporopollenin.

* Mesofaunal faeces

Oribatid faeces (Fig. 305) kept intact their shape, contrary to other faeces (most probably of springtails) the content of which more or less dispersed in enchytraeid intestines (Fig. 306). In the latter case, bacteria, which abound in those faeces (see below), were in way to be degraded.
<figure><img src="image_43.png" /></figure>

Fig. 301: Enchytraeid gut contents observed by transparency, cyst of *Euglypha* sp. in way to be degraded (CP); Fig. 302: Idem, cyst of *Phryganella acropodia* in way to be degraded, with quartz particles standing in place (CP); Fig. 303: Idem, remains of a pollen pine, with exine still recognizable in bladders (CP); Fig. 304: Idem, granular mass issued from the degradation of pollen exine, with fragments of melanised hyphae of *Cenococcum geophilum* (CP); Fig. 305: Idem, mite faeces (CP); Fig. 306: Idem, other mesofaunal faeces dispersed in the intestine (CP); Fig. 307: Idem, viable colony of Chlorophyceae (CP); Fig. 308: Idem, intestinal microflora of a morphological type different from that found in *Cognettia sphagnetorum* (CP)

CP = phase contrast; length of segment = 50 µm
* Algae

Algae might be filamentous or unicellular Cyanophyceae (cyanobacteria), which were generally degraded in enchytraeid intestines, as observed in L₂ (Fig. 160), or Chlorophyceae, which seemed to remain viable, as ascertained by the opacity of their cytoplasm (Fig. 307). The poor digestibility of green algae had been already noted in L₂ (Fig. 157).

* Intestinal microflora

The intestinal microflora of *Cognettia sphagnetorum* was comprised of two morphological types which had been already described in L₂ (Figs. 170 & 171). The other enchytraeid species observed in F₁ displayed only one morphological type of intestinal microflora, at least judging from the only two specimens present in the sample (Fig. 308). This observation points to some kind of specificity in the bacteria hosted by enchytraeid intestines.

* Transport on the tegument

Few remarks have to be added to observations done in L₁ (Figs. 45-50) and L₂ (Fig. 154). The abundance of mineral particles on the tegument of enchytraeids, despite their organic-only diet (to the exception of cysts of *Phryganella acropodia*), points to the importance of vertical movements, probably of daily periodicity, exerted by these animals in the soil (Springett et al. 1970). Fungal spores were always actively transported on the tegument (Fig. 309), attesting for a prominent role of enchytraeid worms in the dissemination of fungal propagules.

### Oribatid mites

* Generalities

Oribatids were mostly represented by box mites, in abundance (41%) and even more in biovolume (97%). These animals feed mainly on plant material. They were absent from overlying layers, to the exception of a single specimen found in L₁. This holds true also for *Nothrus sylvestris* (Koch), which was absent in L₁ and L₂. Other species, for the main, had already been observed in overlying layers.
<figure><img src="image_44.png" /></figure>

Fig. 309: Fungal spores transported on the tegument of an enchytraeid (CP); Fig. 310: *Phthiracarus sp.*, detail of second-order faecal pellet showing crushed plant cell walls with neat contours and strong refringence (CP); Fig. 311: Idem, detail of the third-order faecal pellet, showing crushed plant cell walls with fuzzy contours and browning of most internal parts (CP); Fig. 312: *Folsomia manolachei*, intestine observed by transparency showing hyaline hyphae in way to be degraded and areolae from pine tracheids (CP); Fig. 313: *Parisotoma notabilis*, observation of the body by transparency showing septicemia (CP); Fig. 314: *Pseudosinella terricola*, intestine observed by transparency showing hyaline fungal hyphae (in way to be degraded) and fragmented melanised fungal hyphae (with intact walls) (CP); Fig. 315: Idem, melanised fungal spores, more or less broken (CP); Fig. 316: Idem, hyaline hyphae in way to be degraded and aggregates of oxalate crystals (CP)

CP = phase contrast; length of segment = 50 µm
* Box mites

This taxonomically (although not morphologically) heterogeneous group was represented by the genera *Rhysotritia* and *Phthiracarus*, which did not occupy the same micro-niches, at least when taking into account their ontogenetic stages or ‘stases’ (Table 10).

<table><caption>**Table 10.** Micro-niches occupied by box mites in the F1 layer</caption><thead><tr><th>Stase</th><th>Genus</th><th>Needle</th><th>Environment</th></tr></thead><tbody><tr><td>Larva</td><td><i>Phthiracarus</i></td><td>3</td><td></td></tr><tr><td>Nymph</td><td><i>Phthiracarus</i></td><td>2</td><td></td></tr><tr><td>Adult</td><td><i>Phthiracarus</i></td><td>1</td><td>4</td></tr><tr><td>Larva</td><td><i>Rhysotritia</i></td><td>2</td><td>9</td></tr><tr><td>Nymph</td><td><i>Rhysotritia</i></td><td></td><td>1</td></tr><tr><td>Adult</td><td><i>Rhysotritia</i></td><td></td><td>2</td></tr></tbody></table>

If adults of both genera were near always found outside of pine needles, this did not hold for larvae: while larvae of *Phthiracarus* (together with their nymphs) were always found at the inside of pine needles, those of *Rhysotritia duplicata* were mostly found in the environment. The presence of chorion debris around larvae of *Rhysotritia duplicata* found in the environment, sometimes still embedding their whole body, attested for hatching (and thus egg deposition) taking place outside of pine needles, penetration of pine needles occurring in a further step. A great number (13) of pre-larvae of this species were found in the environment: they were not accounted for in my census because they were not active. Eggs and pre-larvae of *Rhysotritia duplicata* were easy to recognize by their externally sculptured chorion. The differential ecology of *Phthiracarus* and *Rhysotritia* larvae was explained by the lack of chorion in *Phthiracarus* eggs, which are deposited in cavities created by females at the inside of pine needles, an observation firstly done by Grandjean (1940).

Feeding habits of box mites were based on the consumption of pine plant material. Larvae ground finely plant cells, thanks to the combined movement of rutellum and chelicerae (Dinsdale 1974b). The anatomical structure of pine tissues was no longer recognizable in larval guts, due to fine grinding of cell walls, but adults and nymphs, which ground more coarsely plant material, showed some recalcitrant remnants of pine tissues, such as tracheid areolae, attesting for the pine origin of gut contents. Fungal hyphae (basidiomycetous hyaline hyphae or melanised hyphae of *Cenococcum geophilum*) were sometime present, but only in little amount and in adults only. The presence of an intestinal microflora was detected only in *Rhysotritia duplicata*: however, it must be noticed that bacteria were found associated with post-colon microvilli of *Phthiracarus* sp. by Dinsdale (1974a, 1975).

An interesting phenomenon was the observed change in the aspect of the ingested plant material in the course of intestinal transit. As this is the rule in oribatid mites, two or three faecal
pellets can be seen to be moulded in the gut, as this has been observed in *Adoristes ovatus* feeding on
fungi in L₁ (Fig. 63). Anatomical reasons for this particular ontogenetic pattern have been detailed by
Woodring & Cook (1962), Hoebel-Mävers (1967) and Tarman (1968). The last faecal pellet, located in
the rectum and ready to be excreted, was always more compact and darker than the preceding one,
which was still located either in the colon or in the mesenteron. Compaction of the food bolus in the
colon has been described by Dinsdale (1974a, 1975). Comparative observations on second- and third-
order faecal pellets showed that plant cell wall debris were still intact in the second faecal pellet while
their contours became fuzzy in the third pellet, and that the more when observing inner parts (Figs.
310 & 311). Thus changes similar to what had been observed during ageing of faeces made of
melanised fungal material, i.e. fuzzy contour of cell debris and darkening (Figs. 210 & 211), occurred
at the inside of mite guts filled with cellulosic plant material. The transformation of plant organic
matter into a dark amorphous mass strongly suggests that the formation of humus, i.e. inherited humin
in the sense of Duchaufour (1977), occurs in the intestine of box mites.

* *Nothrus sylvestris*

The particular abundance of fungal hyphae of *Cenococcum geophilum* was noticeable: hyphae
were cut into small pieces. Encrusted hyaline hyphae of *Hyphodontia sp.* were present, too, although
in smaller amounts and always in the company of *Cenococcum geophilum*, as well as some debris of
cell walls which could come from pine roots. It could be hypothesized that *Nothrus sylvestris* browsed
the fungal mantle of jet-black ectomycorrhizae formed by *Cenococcum geophilum*, and ingested
accidentally some cortical tissue. The attractiveness of the root system of pine for this species could
explain why *Nothrus sylvestris* was absent from L₁ and L₂ where fungal mycelia abounded but roots
were absent. Gut contents of *Nothrus sylvestris* in F₁ resembled those of *Platynothrus peltifer*, another
Camisiidae, in L₁ (Fig. 62). The vertical segregation observed between these two species, which were
phylogenetically related and had similar feeding habits, was reminiscent of the segregation observed
between *Nothrus sylvestris* and *Hermaniella granulata* (Nicolet), which had been experimentally
reproduced by Anderson (1978).

Contrary to *Platynothrus peltifer*, no intestinal microflora was observed in *Nothrus sylvestris*.
A particular phenomenon needs to be noted. Encrusted hyaline hyphae of *Hyphodontia sp.* remained
always intact (at least their walls) while melanised hyphae of *Cenococcum geophilum* appeared to be
degraded. This unexpected result shows that the enzymic armature of soil animals, in particular of
oribatid mites, may vary to a great extent according to the food ingested. Stefaniak & Seniczak (1976,
1981, 1983) and Seniczak & Stefaniak (1978) showed on several oribatid species that individuals
selected in their gut associated bacterial strains which varied according to the food to which they had
been accustomed in culture.

* Oppiidae

*Oppiella nova* (Oudemans) fed on the encrusted hyaline basidiomycete *Hyphodontia sp.*
which was associated with orange-brown ectomycorrhizae. Hyphae were cut into small pieces and
agglomerated, then degraded in the digestive tract. Melanised hyphae, probably coming from *Cenococcum geophilum*, were sometimes present, but their walls remained intact. In one case, I observed melanised fungal material in a highly degraded state, but the concomitant abundance of bacteria let me suppose that faecal material had been ingested.

Feeding habits of *Oppia subpectinata* (Oudemans) did not differ to a great extent from those of *Oppiella nova*, with similar degradation of hyphae of *Hyphodontia sp.* and recalcitrance of *Cenococcum geophilum*. However, the latter fungus was more abundant, which could be explained by the larger size of *Oppia subpectinata* and associated mouth parts, making more easy for these animals to cut thick recalcitrant hyphae of *Cenococcum geophilum*.

Nymphs of Oppiidae displayed the same strictly mycophagous feeding habits, with degradation of hyaline hyphae. Observations done on Oppiidae in F₁ strongly support those done on the genus *Oppia* in L₂ (Fig. 174).

* Other species

If I except *Suctobelba subcornigera* (Oudemans), which did not display any gut contents, other studied species, *Oribatula tibialis* (Nicolet), *Nanhermannia nana*, *Odontocepheus elongatus* (Michael) and *Ceratozetes sp.*, fed on a mixture of hyphae of *Hyphodontia sp.* and *Cenococcum geophilum*. It should be noticed that the degradation of hyaline hyphae was observed in *Ceratozetes sp.* and that melanised hyphae were dominant in *Oribatula tibialis*.

* Conclusions

At the inside of the oribatid group, box mites seemed original with their ‘macrophytophagous’ feeding habits in the sense of Luxton (1972). Hayes (1963) showed that different species of box mites could prefer different stages of pine needle decomposition, which was not confirmed in the present study, at least concerning *Phthiracarus* and *Rhysotritia*. However present results confirmed observations by Hayes (1963) that this animal group exhibited a clear preference for more advanced stages of pine needle decomposition, which might explain its absence from L₁ and L₂ layers. Other species were mycophagous, i.e. ‘microphytophagous’ in the sense of Luxton (1972), or exhibited a definite preference for fungi when and where they were abundant. The transfer from non-exclusive phytophagy to mycophagy when fungal material is abundant in the environment has been observed to affect a great number of oribatid species (Hartenstein, 1962a, b; Luxton, 1972; Haq, 1981; Behan-Pelletier & Hill, 1983).

*Miscellaneous mites and spiders*
Other mites and spiders did not possess any solid matter in their gut, which did not indicate their feeding habits. However, near all of them are known as predators which did not swallow their prey but rather suck their haemolymph and some internal tissues (after pre-oral digestion in the case of spiders). A unique specimen of Acaridida showed fragments of basidiomycetous hyphae and bacteria in its gut.

## Woodlice

Two juvenile specimens of *Trichoniscus* were observed, tentatively identified as *Trichoniscus pusillus* (Dallens, personal communication). Their gut contents appeared to be composite and highly degraded: fungal material (broken spores, long hyphal fragments of *Cenococcum geophilum*), mineral material (quartz grains), animal material (fragments of arthropod cuticles, broken cysts of Thecamoeba) and amorphous organic matter. This was reminiscent of enchytraeid variegated feeding habits and I hypothesized that these specimens had fed on enchytraeid faeces. The composition of their gut contents strongly differed from the composition of type B faeces (Fig. 224), which were made of fragmented but poorly transformed pine needles (see below).

## Springtails

Isotomidae were the dominant family, at least from the point of view of densities. *Folsomia manolachei*, *Parisotoma notabilis* and *Isotomiella minor* (Schäffer) were represented by 23, 15 and 4 specimens, respectively, totalling 42 specimens among the 67 springtails collected in $F_1$. *Folsomia manolachei* dominated the community in density, as in the overlying $L_2$ layer, but it was accompanied by a much higher number of species. The presence of poduromorph species, such as *Willemia anophthalma* Börner, a species typical of very acid humus (Ponge, 1980, 1983; Pozo, 1986), and of neelid species such as *Megalothorax minimus* (Willem), was noticeable, as was that of the acidophilic entomobryid *Pseudosinella terricola* Gisin. These species were absent from overlying layers, indicating a shift towards a deeper-living community (Ponge 1980). However, some epigeic species were still present, such as juveniles of *Entomobrya sp.*, and *Pogonognathellus flavescens*.

*Folsomia manolachei* ingested mainly a mixture of hyaline and melanised fungal hyphae, cut in small irregular pieces and mixed with numerous bacteria. Hyaline encrusted hyphae of *Hyphodontia sp.* displayed a variety of degradation stages, some hyphae becoming hardly discernible. Less frequently, tracheid areolae attested for the consumption of pine tissues, probably issuing from needles (Fig. 312). As for observations done in $L_2$ (see above), the interpretation was that *Folsomia manolachei* ingested invertebrate faeces (mite or more probably enchytraeid faeces because of the irregular size of hyphal fragments) which had been invaded by bacteria previous to ingestion. The direct ingestion of strongly decayed pine needles was not supported, because fragments of needle epidermis and hypodermis and melanised stromata of *Verticicladium trifidum* should be present in addition to tracheid areolae. The observation of enchytraeid faeces, which were accumulating in the $F_1$ layer (see below), let me suppose that hyaline basidiomycetous hyphae and bacteria which colonised these faeces were the main food resource of *Folsomia manolachei*, in addition to miscellaneous degradation products which could be present in enchytraeid faeces, too.
Quite similar observations were done in *Isotomiella minor*, which exhibited pine areolae mixed with highly transformed fungal and bacterial material. Gut contents of *Parisotoma notabilis* were similarly comprised of bacteria and highly transformed fungal fragments, but the high proportion of starving specimens (12 among 15, i.e. 80%) should be noticed, together with several specimens which were seriously infected by bacteria (Fig. 313). This indicated that the population of *Parisotoma notabilis* was in a bad condition and poorly active trophically. I was unable to explain this phenomenon, but I want to note that cultures of this species were submitted to wide fluctuations (personal observations).

Feeding habits of *Pseudosinella terricola* were quite different. This species, which was dominant in volume within the springtail group, belongs to the *terricola-mauli* species group (Ponge 1980, 1983). It fed exclusively on fungi, like the congeneric *Pseudosinella alba* (Packard) (Arpin et al., 1980; Ponge & Charpentié, 1981). Contrary to the three abovementioned isotomid species *Pseudosinella terricola* ingested only fungal material, without any bacteria in admixture: hyaline and melanised hyphae, cut regularly in small pieces (Fig. 314), and spores (Fig. 315). Melanised hyphae kept their walls intact, contrary to hyaline hyphae (Figs. 314 & 316). In the case of hyaline hyphae with encrusted walls, oxalate crystals remained and agglomerated once fungal walls had been degraded (Fig. 316), as this had been observed in enchytraeids (Fig. 298). When the digestive process was incipient, well delimited zones could be found in the intestine where fungal hyphae were degraded while the rest of the food bolus was still intact (Fig. 317). Humbert (1974) showed the coexistence of zones with strongly different pH values in the mesenteron, where the food bolus remains a long time, the passage from a zone to another shifting forward during digestion. This could explain transitional patterns such as that depicted in Figure 317. The biggest spores (basidiospores?) appeared to be broken, but their wall was not degraded. In this case only fungal cytoplasm was digested, probably as it happens in *Pseudosinella alba* (Ponge & Charpentié, 1981).

Feeding habits of *Willemia anophthalma*, a species living in very acid and waterlogged soils (Ponge, 1980, 1983; Pozo, 1986), did not differ to a great extent from the previous species, being exclusively mycophagous. However, some differences deserve to be highlighted. Dematiaceous (melanised) material was absent, only fragments of hyaline basidiomycetous hyphae being found (Fig. 318). Contrary to *Pseudosinella terricola*, oxalate crystals seemed to have been dissolved in the gut, as this had been observed in *Oppia sp.* in L₂ (Fig. 174). In the course of the digestion of basidiomycete hyphae, intra-hyphal septa seemed to resist more than external walls (Fig. 318). At last, another difference with *Pseudosinella terricola* was the presence of bacteria in the gut of *Willemia anophthalma* (Fig. 319). These bacteria were in way to be degraded and were absent from starving specimens, thus they did not belong to symbiotic microflora and should be considered as a food resource.

Food habits of *Lepidocyrtus lanuginosus* (Gmelin), a species belonging to a genus brother to *Pseudosinella*, were mainly based on unicellular Chlorophyceae, mixed or not with fungi but always dominant (Fig. 320). However, observations on gut contents could only be made on two specimens, the other two being starved. The cytoplasm of algal cells generally disappeared (no opacity in phase contrast) and some walls appeared in way to be degraded. Thus the enzymic equipment of this species seemed to be adapted to an algal diet, even if algae were not the only food resource used by these animals, contrary to most animal groups prospected.

Observing two specimens belonging to the genus *Entomobrya* showed that their gut contents were comprised of melanised fungal spores, broken when of a big size, mixed with bacteria, and pine
<figure><img src="image_45.png" /><figcaption>Fig. 317: *Pseudosinella terricola*, intestine observed by transparency showing the passage from a zone with degraded hyphal walls (centre) to two zones with intact walls (right and left) (CP); Fig. 318: *Willemia anophthalma*, intestine observed by transparency showing hyaline basidiomycetous hyphae in way to be degraded (CP); Fig. 319: Idem, bacteria in way to be degraded (CP); Fig. 320: *Lepidocytus lanuginosus*, intestine observed by transparency showing Chlorophyceae (empty walls) mixed with bacteria (CP); Fig. 321: *Megalothorax minimus*: intestine observed by transparency showing faecal pellets in way to be moulded in the intestine (CP); Fig. 322: *Parisotoma notabilis*, bacteria transported on a leg (CP); Fig. 323: Sciarid larvae, intestine observed by transparency showing pine material (see areolae) in way to be degraded (CP); Fig. 324: Faeces of minute oribatid mites at the inside of a corpse of *Phthiracarus sp*. (CP)</figcaption></figure>

CP = phase contrast; length of segment = 50 µm
pollen grains, broken in small pieces. The absence of fungal hyphae, although dominant in the environment, was remarkable.

*Megalothorax minimus* was particular, because of the presence of several faeces in formation in the intestine (Fig. 321), resembling what had been observed in oribatid mites (Fig. 63), but without any browning and compaction of the food bolus. Gut contents were comprised of bacteria and minute unidentifiable debris. This species, which belongs to a group (Neelidae) which is quite original by its anatomical features within the Class Collembola (Massoud, 1971; Dallai, 1979), was unique in feeding only on food items of micrometric size. By its feeding habits, this minute springtail pertains rather to microfauna than to mesofauna.

The unique specimen observed belonging to *Pogonognathellus flavescens* showed hyaline hyphae (in way to be degraded) and melanised hyphae (with intact walls) in its gut. They were cut into pieces and mixed with bacteria.

A great variety of feeding habits was thus observed in Collembola, but without any definite sharing of food resources. Apart from typified feeding behaviour of *Pseudosinella alba*, *Willemia anophthalma*, *Lepidocyrtus lanuginosus* and *Megalothorax minimus*, other species displayed a diet made of a mixture of fungal and bacterial material, probably issued from the consumption of invertebrate faeces (coprophagy). Fungal material and bacteria were degraded, melanised items (hyphae, spores) being either cut into pieces or broken but without any apparent degradation of cell walls. Many authors, faced to the strongly degraded aspect of collembolan gut contents, spoke of humified or ‘amorphous’ organic matter (Poole, 1959; Knight & Angel, 1967; Gilmore & Raffensperger, 1970; Bödvarsson, 1970; Marshall, 1978). The comparative study of all types of animal faeces and gut contents found in the sample gives weight to coprophagy as the dominant feeding behaviour in Collembola, a hypothesis which has been already emitted by Poole (1959). The great amount of starving individuals (29%, if one discards the particular case of *Parisotoma notabilis*) is worth to notice, too. This is special to springtails and is explained by repetitive moulting all along the life of these non-metamorphosing animals (Singh, 1964; Joosse, 1975).

Among items transported on the tegument of Collembola, in addition to already described chrysomonadin colonies (Fig. 289), the mucilage of which favoured the development of bacteria, numerous bacterial colonies were seen adhering to antennae and legs (Fig. 322). Carrying and dispersal of microbial propagules, even though of lesser extent than in enchytraeids, is thus another aspect of the role of springtails in the biological functioning of the soil.

*Insect larvae*

Even though the total number of fly larvae did not change to a great extent when compared to L₂ (14 in F₁ against 12 in L₂), the community change which had been already mentioned in L₂ still continued in F₁, i.e. Cecidomyidae were replaced by Sciaridae as far as litter became more aged. There was practically no longer Cecidomyidae in F₁ (1 against 13 Sciaridae). It was a pity that the absence of any solid matter in cecidomyid guts prevented me to discern their favoured food, which could have explained, at least partly, the niche segregation observed within fly larvae. Chironomidae were totally absent from F₁, but they were also poorly represented in the overlying layers.
Sciaridae ingested a noticeable amount of plant tissues issuing from pine needles. It must be mentioned that two specimens were directly picked off from the inside of pine needles while dissecting them. The fungal material seemed intact, at least concerning hyphal walls, whether hyaline or melanised, as this had been already observed in $L_1$ (Fig. 67) and $L_2$ (Figs. 178 & 179). Contrary to fungal material, plant material (pine tissues) was strongly degraded in sciarid intestines (Fig. 323). This contrast is remarkable, inasmuch as it seems to be the contrary of what has been observed in most other groups, where hyphal walls (at least those of hyaline hyphae) were more easily digested than recalcitrant lignocellulosic pine cell walls. Quite similar to enchytraeids (see above), a revival of macrophytophagous feeding behaviour was observed in sciarid larvae: mosses were consumed in $L_1$, pine needles in $F_1$, but plant material was abandoned in the intermediate layer $L_2$ to the benefit of fungi. However, and contrary to enchytraeids, only very few moss material was consumed by sciarid larvae in $F_1$. Other food items must be noticed, too, such as pine pollen grains, bacteria, cysts of Thecamoeba (*Euglypha* spp., *Nebela collaris*), sometimes but very rarely quartz grains. Ingested items, in particular fungal hyphae, were of a greater length than in microarthropods (springtails, oribatid mites) but of a shorter length than in enchytraeid worms.

The other two families of insect larvae, Cecidomyidae (1 specimen) for fly larvae, Cantharidae (1 specimen) for beetle larvae, did not possess any particulate matter in their intestines, thus nothing can be said about their food regime. However, it should be noticed that Cantharidae are known to be carnivorous (Paulian, 1949).

## Animal corpses

### Preliminary remarks

Table 11 shows densities and nature of the different corpses and animal fragments which were found when sorting litter components under the dissecting microscope. Among miscellaneous arthropod fragments there were many isolated insect legs or wings, which could come from the amputation of living imagos. In the ignorance of their living or dead origin they were counted as corpses. No arthropod exuviae were found at all.

There was a dramatic increase in the number of corpses compared to the overlying layer. This increase was much higher than that of living specimens (4, 15 then 336 corpses against 75, 85 then 226 living specimens in $L_1$, $L_2$ then $F_1$, respectively, to the exclusion of microfauna). This means that accumulation took place, mainly in the form of oribatid exoskeletons (74% of censused corpses). Springtail corpses were totally absent from the $F_1$ layer, despite of a dramatic increase in abundance. Most oribatid corpses were of adults, suggesting that this group was not submitted to a high level of predation, in particular at adult stage: long duration of life and low reproduction rates are known in this group (Norton, 1985). However, this author mentioned the existence of external and internal parasites in adults, which might result in the production of intact exoskeletons when adults die from parasitism, while younger stages are swallowed by predators and do not accumulate exoskeletons.
<table><caption>**Table 11.** Number of animal corpses and corpse fragments found under the binocular microscope in the F₁ layer</caption><tbody><tr><td><strong>Enchytraeids</strong></td><td>13</td></tr><tr><td><strong>Oribatid mites</strong></td><td>248</td></tr><tr><td>Rhysotritia duplicata</td><td>50</td></tr><tr><td>Platynothrus peltifer</td><td>35</td></tr><tr><td>Phthiracarus sp.</td><td>29</td></tr><tr><td>Oribatula tibialis</td><td>23</td></tr><tr><td>Ceratoppia bipilis</td><td>21</td></tr><tr><td>Chamobates sp.</td><td>21</td></tr><tr><td>Oppia ornata</td><td>11</td></tr><tr><td>Oppia subpectinata</td><td>11</td></tr><tr><td>Unidentified Oppiidae</td><td>10</td></tr><tr><td>Oppiella nova</td><td>5</td></tr><tr><td>Micreremus brevipes</td><td>4</td></tr><tr><td>Nanhermannia nana</td><td>3</td></tr><tr><td>Adoristes ovatus</td><td>3</td></tr><tr><td>Unidentified oribatid mites</td><td>3</td></tr><tr><td>Nothrus sylvestris</td><td>2</td></tr><tr><td>Parachipteria punctata</td><td>2</td></tr><tr><td>Suctobelba group sarekensis</td><td>2</td></tr><tr><td>Oppiella obsoleta</td><td>2</td></tr><tr><td>Unidentified Pelopsidae</td><td>1</td></tr><tr><td>Suctobelba group trigona</td><td>1</td></tr><tr><td>Suctobelba group nasalis</td><td>1</td></tr><tr><td>Scheloribates latipes</td><td>1</td></tr><tr><td><strong>Miscellaneous mites</strong></td><td>40</td></tr><tr><td>Gamasina</td><td>24</td></tr><tr><td>Uropodina</td><td>12</td></tr><tr><td>Actinedida</td><td>3</td></tr><tr><td>Acaridida</td><td>1</td></tr><tr><td><strong>Spiders</strong></td><td>2</td></tr><tr><td>Miscellaneous arthropod fragments</td><td>29</td></tr><tr><td>Eggs (dead)</td><td>4</td></tr></tbody></table>

Enchytraeid worms

Dead enchytraeid worms were in the form of brown fragments, the inside of which was hard to observe because of the opacity of animal tissues. They appeared to be tanned (mummified), without any trace of microorganisms. Given their small size and the intensity of fragmentation in the F₁ layer of the dominant species, *Cognettia sphagnetorum*, I hypothesized they were unregenerate, non-viable fragments.

Oribatid mites
Box mites were dominant (79 specimens, i.e. 32% of oribatid corpses), which was expected given the numerical dominance of this group. However, *Platynothrus peltifer* corpses were abundant in F₁ while this species was numerically dominant in L₁. This witnessed the past history of the F₁ layer, which was in a more superficial position and at a lesser advanced stage of decomposition during previous winter or spring. The presence of *Micreremus brevipes* (Michael) is worth to notice, since this species had not been found as living specimens in the three layers investigated. Corpses of *Micreremus brevipes* probably fell from tree foliage, where this species is known to live (Travé, 1963).

It was not possible to discern differences in the fate of corpses belonging to different species. However, an observed relationship between adult mortality and larval development should be noticed. A majority (80%) of corpses of *Rhysotritia duplicata* harboured one, two or more rarely three eggs which were seemingly intact, often with pre-larvae at the inside, sometimes reduced to an empty chorion. Such a phenomenon was not retrieved in *Phthiracarus*, where only one corpse was seen with an egg at the inside. Larvae or larval exuviae were retrieved in some corpses of *Ceratoppia bipilis* and more rarely in *Oribatula tibialis*. From these observations it can be concluded that ecdysis (hatching) occurred once female mother was dead or that it caused its death. In this case the plant or fungal material which had been ingested by the female before it died could offer a food resource for the young larvae which hatched in its body. It was not uncommon to see the food bolus, normally in the form of two or three big pellets, pulverised in numerous much smaller pellets of similar size, seemingly excreted by oribatid larvae (Fig. 324) or enchytraeids (Fig. 325) which penetrated the dead body of an adult oribatid. Larvae of *Rhysotritia duplicata* were never retrieved at the inside of dead female bodies, only an empty chorion being observed. It is highly probable that mortality was at a high rate in egg-carrying females, or more exactly in females carrying pre-larvae, as observed by Grandjean (1940). In this case hatching occurs at the inside of mother body if pre-larval development was achieved, larvae soon coming out from the corpse of their parent. This stage could be protracted in *Ceratoppia bipilis* and *Oribatula tibialis*, being seemingly achieved at the following moult only. These hypotheses, coherent with my personal observations, need to be verified in culture, which is out of the scope of the present study.

Corpses observed in the F₁ layer displayed a variety of decay patterns, without any general or specific trend which could be discerned. Similarly, no successional trend between fungi and bacteria was discernable. However, it should be remarked that the most advanced stage of decomposition of corpses was a complete cleaning by animals which penetrated at the inside, either enchytraeids (Fig. 325) or oribatids (Fig. 324), which were identified by the typical shape and size of their faeces, when present. In this case, there were no longer microorganisms in the cleaned corpses, to the exception of a film on the inner side of the cuticle.

The inside of corpses was colonised by several fungi, which were often seen to cohabitate. An unidentified hyphomycete was repeatedly encountered, which had not been observed in decaying plant material or in faeces. It was present as a network of hyaline hyphae, weakly septate (Fig. 326), part of which could be dead (empty hyphae or 'ghosts') and mixed with bacteria (Fig. 327). Mycorrhizal fungi were also present. *Cenococcum geophilum* was often present, alone (Fig. 328) or in the company of bacteria (Fig. 329). This fungus attacked the cuticle, too. Its melanised hyphae could be seen running at the surface of the cuticle, with a decay zone a few µm wide on both sides of hyphae (Fig. 330). The attack of the cuticle was also observed to be caused by other unidentified fungi imperfecti (Fig. 331). *Hyphodontia sp.*, the basidiomycete associated with orange-brown mycorrhizae, was also
<figure><img src="image_46.png" /><figcaption>Fig. 325: Faeces of enchytraeid worms at the inside of a corpse of *Chamobates* sp. (CP); Fig. 326: Living hyaline hyphae at the inside of a
corpse of *Oppia subjectinata* (CP); Fig. 327: Living and dead hyaline hyphae at the inside of a corpse of *Platynothrus peltifer* (CP);
Fig. 328: Melanised hyphae of *Cenococcum geophilum* at the inside of a leg from a corpse of *Rhysotritia duplicata* (CP); Fig. 329: Melanised
hyphae of *Cenococcum geophilum* and bacteria at the inside of a corpse of *Rhysotritia duplicata* (CP); Fig. 330: Corpse of *Oribatula tibialis*,
attack of the cuticle by hyphae of *Cenococcum geophilum* (CP); Fig. 331: Corpse of *Chamobates* sp., attack of the cuticle by hyaline hyphae;
Fig. 332: Development of basidiomycetous hyphae of *Hyphodontia* sp. at the inside of a corpse of *Rhysotritia duplicata*</figcaption></figure>

CP = phase contrast; length of segment = 50 µm
seen penetrating oribatid corpses (Fig. 332). I found cystidia of this fungus, quite similar to those already described in L₂ (Figs. 120 & 121) and F₁ (Fig. 241), at the inside of two oribatid corpses, further attesting for the variegated way of life of *Hyphodontia sp.* Ectomycorrhizal fungi were also observed embedding corpses, as they did for the rest of decaying material.

Bacteria living at the inside of oribatid corpses were curiously similar to those living symbiotically in living specimens (intestinal microflora), as for example in *Platynothrus peltifer* (Fig. 333). Actinomycetes were also observed (Fig. 334), although less frequently.

Many animals seemed to live, at least temporarily, in oribatid corpses. Enchytraeids and oribatids (larvae and adults of small species) deposited faeces and, in the case of enchytraeids, pollen grains and quartz particles transported on the tegument. In addition, numerous cyst amoebae were observed, most of them (62%) being *Phryganella acropodia*, as mentioned above. Nematodes and rotifers were also observed, although less frequently.

## Other arthropods

The colonisation of other arthropod corpses did not differ from that of oribatid mites. Fungal development, mostly of ectomycorrhizal fungi, was observed outside and inside decaying bodies. The basidiomycete associated with velvety pink ectomycorrhizae was observed at the inside of a gamasid leg (Fig. 335). The more corpses or fragments of legs were of a big size, the more frequently I observed traces of the passage of miscellaneous invertebrates: nematodes, cyst amoebae, mites, enchytraeid worms.

## Animal faeces

### Type A faeces (slugs?)

The examination of type A faeces under the dissecting microscope (Fig. 223) revealed that they were comprised of long fragments of pine needles, without any apparent change in their aspect. The microscopic examination of sections confirmed that point, showing unaltered fragile tissues such as mesophyll (Fig. 336). Fungal hyphae could be seen, attesting from previous fungal colonisation of pine needles, but all cells, whether of pine or fungi, were devoid of cytoplasm. Microbial development was only rarely observed and was localised to some micro-sites: bacteria (Fig. 337), chroococcal Cyanophyceae (Fig. 338), and very rarely fungi. These faeces, which have been tentatively attributed to slugs, did not seem to offer good conditions for the development of microflora, probably because of the absence of any plant or fungal cytoplasm. As a consequence, the pine material which was present at the inside of type A faeces seemed to be arrested at an earlier stage of decay than that of other pine needles found in F₁.
<figure><img src="image_47.png" /><figcaption>Fig. 333: Bacteria at the inside of a corpse of *Platynothrus peltifer*, resembling those of intestinal microflora (CP); Fig. 334: *Oribatula tibialis*, actinomycetes on the inner surface of the cuticle (CP); Fig. 335: Hyphae with clamp connections of the basidiomycete associated with pink ectomycorrhizae, at the inside of a gamasid corpse (CP); Fig. 336: Section through type A excrement (slug?), detail showing pine needle mesophyll with empty cells but intact walls (CP); Fig. 337: Idem, showing bacteria in a micro-site (CP); Fig. 338: Idem, showing Cyanophyceae (cyanobacteria) in a micro-site (CP); Fig. 339: Section through type B excrement (woodlouse?), detail showing Chlorophyceae in a micro-site (CP); Fig. 340: Idem, detail showing oribatid faeces in a cavity (CP)</figcaption></figure>

CP = phase contrast; length of segment = 50 µm
### Type B faeces (woodlice?)

Although fragments of pine needles found in type B faeces (Fig. 224) were shorter than in type A, they exhibited similar features when sectioned and examined under the light microscope: plant and fungal cell walls were intact, cytoplasm was absent, bacterial and algal colonies (Fig. 339) were limited to some micro-sites. It should be highlighted that micro-sites with microbial colonies were more abundant when not far from the surface of type B faeces, pointing to difficulties for colonising internal parts of faeces. Reasons for this limitation could be manifold: absence of interconnected pores, absence of vectors (fauna), anaerobic conditions. The same hypotheses have been already erected to explain particular features of soil micro-aggregates (Kilbertus, 1980). However, faeces of type B were penetrated by mesofauna, as attested by the deposition of oribatid faeces in some cavities (Fig. 340). The question thus remains quite open.

There was a great variation in the density of micro-sites colonised by bacteria from faeces to faeces. Decay of bacteria (fuzzy contour under phase contrast) was observed in some faeces which exhibited a high number of micro-sites (Fig. 341). This was interpreted as an indication of ageing.

The ingested material (pine needles) could be mixed with faecal material from animals having previously browsed the ingested pine needles. For instance, Figure 342 shows in a section the abrupt passage from transfusion tissue to a mass of finely ground plant material. This was interpreted as the presence of faecal material (probably from type C, i.e. earthworm faeces) applied against a pine needle which had been nibbled up to the central cylinder.

As in the previous case (type A faeces) the absence of any penetration by ectomycorrhizal fungi was remarkable. The absence of any moss material should be highlighted, too, indicating a clear trophic choice.

### Type C faeces (earthworms)

Two major differences with the previous two types of macroinvertebrate faeces (types A and B) should be noted. First, type C faeces were comprised of small, although irregular particles (Fig. 343). This resulted from the ingested material being ground in the muscular gizzard of earthworms, hence the irregular size of particles, contrary to arthropods which cut the material with their mouthparts before swallowing it. Second, the content of type C faeces was composite, being an intimate mixture of plant cells, fungal hyphae and stromata, pollen grains, resin and oribatid faeces (Fig. 344). The fact that oribatid faeces were retrieved intact was indicative of their strong cohesion. Some quartz grains were found but only scarcely. Fungal hyphae, mostly represented by *Hyphodontia* sp., the basidiomycete associated with orange-brown ectomycorrhizae, were abundant, which was not the case in faecal types A and B. The variegated nature of type C faeces strongly suggested the absence of definite trophic choice from the part of the earthworms which produced them.

When they were free in the environment (not attached to a plant substrate) type C faeces did not exhibit any intense bacterial and algal development. As in type B faeces, micro-sites filled with micro-organisms, such as chroococcal Cyanophyceae, were observed (Fig. 345). Sometimes bacterial
<figure><img src="image_48.png" /></figure>

Fig. 341: Section through type B excrement (woodlice?), detail showing a bacteria colony in way to be degraded (CP); Fig. 342: Idem, detail showing the passage from transfusion tissue from pine needles (right side) to finely ground plant material from earthworm faeces (CP); Fig. 343: Section through type C excrement (earthworms), detail showing finely but irregularly ground pine tissues (CP); Fig. 344: Idem, detail showing an oribatid excrement (CP); Fig. 345: Idem, detail showing a micro-site with chroococcal Cyanophyceae (CP); Fig. 346: Idem, detail showing bacterial development at the surface of the excrement (CP); Fig. 347: Idem, detail showing box mite faeces deposited in a gallery (CP); Fig. 348: Idem, detail showing hyaline hyphae in way to be degraded (CP)

CP = phase contrast; length of segment = 50 µm
development occurred at the surface of excrements (Fig. 346). However, type C faeces were intensely penetrated by fungi, either *Cenococcum geophilum* (Fig. 230) or basidiomycetous rhizomorphs. These faeces were also penetrated by animals, such as box mites, which bore galleries (Fig. 347). The tunnelling activity of an adult *Rhysotritia duplicata* was ascertained through the deposition among its faeces of an egg with a typical chorion in a gallery.

A great number of type C faeces were tightly appressed again fragments of plant organs (pine needles or bark, moss stems, etc...) or squashed between two distinct plant debris. Movements of animals were thought responsible for such deformation of freshly deposited lumbricid faecal material. Bacterial development was more intense than in free faeces and reached the inner part of the excrement, in addition to still colonised micro-sites. The external origin of microbial colonisation was attested by the more advanced stage of decomposition in the periphery of the faeces, in particular concerning hyaline fungal hyphae (Fig. 348). Several hypotheses were erected to explain differences in bacterial development between free and appressed type C faeces, none of them being fully supported by observations, (i) differences in ageing state, free faeces being more recent than appressed ones (but the latter were penetrated by slow-growing fungi such as *Cenococcum geophilum*), (ii) further contamination by animal movements, (iii) alleviation of anaerobiosis, etc...

It must be noticed that type C faeces, which were attributed to earthworms, did not exhibit any sign of mixing of mineral with organic matter. I hypothesized that they were produced by epigeic earthworms. Only one species was collected in the study site (Bouché, personal communication): *Dendrobaena octaedra*, an epigeic earthworm associated to very acid humus (Satchell, 1967; Bouché, 1972; Martinucci & Sala, 1979).

## Mineral faeces

* Preliminary remarks

A weak number of faeces, instable when manipulated with forceps, exhibited a mineral content which attested for the deeper origin of their content. Their size and aspect was reminiscent of type C (earthworm) faeces, although *Dendrobaena octaedra* was classified as an epigeic. However, Martinucci & Sala (1979) considered this species as a weak burrower, not living exclusively in litter. It might be supposed that this animal moved down, probably for physiological reasons (diapause or quiescent stage), at some periods of the year (Satchell, 1967). I did not observe any mixing of mineral with organic matter, since the uppermost majority of earthworm faeces were purely organic, while a minority was purely or near-purely mineral.

* White mineral faeces
Their content probably came from the A₁₂ horizon (see Table 1) which was very poor in organic matter. They were comprised of quartz grains (of sand size), silt and clay particles. Traces of microflora (probably issued from deeper horizons) were observed: bacteria at the surface of quartz grains (Fig. 349), and empty and collapsed hyaline hyphae aggregating mineral masses (Fig. 350). These hyaline hyphae seemed to have a strong aggregative power: they were often seen covered with clay and silt mineral particles (Fig. 351). It has been verified experimentally that fungi were able to synthesize organic compounds with a high aggregative power for fine (< 50µm) particles (Martin et al., 1959).

* Grey mineral faeces

In addition to colonising hyaline hyphae which had been described in white mineral faeces, grey mineral faeces displayed fragments of empty sclerotia and hyphae of *Cenococcum geophilum* (Fig. 352) and opaque dark brown organic fragments (humus) of unknown origin. Despite the grey colour of these faeces, which was due to the admixture of small organic debris (melanised fungal material, humified organic matter), quartz grains seemed clean, not covered with organic matter, if I except bacteria as depicted in while mineral faeces (Fig. 349). Grey mineral faeces came probably from the A₁₁ horizon, which was richer in organic matter and dark-coloured (see Table 1).

*Enchytraeid faeces*

These faeces were assembled in light-brown masses, free in the environment, at the inside of pine needles (Fig. 222) or between bark and wood in fallen branches and twigs of pine. Faeces were agglomerated by a dense network of fungal hyphae, which ensured the cohesion of faecal assemblages (Fig. 353). The composition of enchytraeid faeces was quite similar to their gut contents, plant material (mostly from pine) being dominant. Fungal material, which had been probably near totally digested (Fig. 297), was no longer observed in the excrements. On the contrary, plant cell walls were still intact. No bacterial development was visible, but faecal masses were abundantly colonised by hyphae of ectomycorrhizal fungi: *Cenococcum geophilum*, *Hyphodontia sp.*, encrusted (Fig. 354) or not, and the basidiomycete associated with pink ectomycorrhizae (Fig. 355). Filamentous hormogonal (*Nostoc*-like) Cyanophyceae with heterocysts were often observed in the mycelium embedding enchytraeid faeces (Fig. 354). Cyst amoebae were very abundant, as well as naked amoebae (Fig. 290). Colonies of chroococcal Cyanophyceae were scarcely observed, too (Fig. 356).

*Oribatid faeces*

Whether they were found at the inside of pine needles (Fig. 221), bark, faeces of macroinvertebrates (Figs. 340 & 347) or free in the environment, most oribatid faeces were comprised of plant material, the pine origin of which was deduced from the presence of areolae. Sometimes some amount of fungal
<figure><img src="image_49.png" /></figure>

Fig. 349: Mineral faeces, detail showing bacteria at the surface of a quartz grain (CP); Fig. 350: Idem, detail showing empty hyaline hyphae aggregating mineral particles (CP); Fig. 351: Idem, detail showing the agglutination of clay and silt particles around dead hyphae (CP); Fig. 352: Idem, fragment of hypha of *Cenococcum geophilum* (CP); Fig. 353: Enchytraeid faeces embedded in the secondary mycelium of *Hyphodontia sp.* (CP); Fig. 354: Idem, detail showing encrusted hyphae of *Hyphodontia sp.* and filamentous Cyanophyceae (CP); Fig. 355: Idem, detail showing hyphae of the basidiomycete associated with pink ectomycorrhizae in the mycelium embedding enchytraeid faeces (CP); Idem, detail showing a colony of chroococcal Cyanophyceae (BMSL)

CP = phase contrast; BMSL = methyl blue-Sudan III-lactophenol coloration; length of segment = 50 µm
material was visible, only hyphae of *Cenococcum geophilum* being still recognizable (Fig. 357). Given their plant content, the majority of oribatid faeces observed in the F₁ layer came from box mites, smaller faeces being attributed to larvae, faeces of intermediate size to nymphs and larger faeces to adults. The degree to which pine material was ground differed according to the size of excrements and thus to ‘stases’ of the species, as explained above. There was always a contrast between the outer and the inner part of the excrement (Fig. 358), the outer part being lightly coloured while the inner part was of a brown colour. Observations on large faeces, where the plant material was coarsely ground (Fig. 359), showed transparent, refringent cell remains in the periphery while the inner part was made of an amorphous mass, brown opaque, without any recognizable item. It had been previously observed that this phenomenon was not due to ageing of faeces, but could be followed at the inside of oribatid guts (Fig. 311). Brown spherules, which had been already observed at the inside of pine needles (Fig. 235), were retrieved intact in oribatid faeces (Fig. 360). They can be suspected to be highly resistant to digestive enzymes, whether of microbial or animal origin.

Microbial colonisation of oribatid faeces was feeble in the F₁ layer, being often limited to the surface of excrements, where bacterial and algal development could be observed (Fig. 361). However, some faeces, of small size and lightly coloured, maybe older (?), displayed an intense bacterial development over their whole thickness (Fig. 362).

### *Sciarid faeces*

Sciarid faeces were identified as such when larvae were still present among their own faeces, otherwise they were not classified. Their content was variegated. Consumption of pine needles was attested by the presence of epidermic remains (Fig. 363) or xylem tracheids, the same for bracken fern, but fungal material was largely dominant: hyphal walls of *Cenococcum geophilum* or *Hyphodontia sp.*, fragments of sclerotia or of fungal mantles. Moss fragments were also found. However, the absence of soft tissues of pine (transfusion tissue, mesophyll, root cortex) and bracken (fundamental parenchyma), and the observation of living specimens (Fig. 323), let me suppose that most soft plant tissues were entirely digested, cell walls comprised. However, fungal walls remained intact, hence the apparent dominance of fungal material.

Bacterial development was never observed at the inside of sciarid faeces, only chroococcal cyanobacteria (Cyanophyceae) were observed at the surface of some faeces (Fig. 324).

### Conclusions about the F₁ layer

Compared to L₁ and L₂, it must be noticed that faunal activity dramatically increased in the F₁ layer. Several zoological groups, phylogenetically remote, participated to the fragmentation of pine needles: earthworms (Annelida), woodlice (Crustacea), slugs (Mollusca) for macrofauna, enchytraeids (Annelida), box mites (Arachnida) and sciarid larvae (Insecta) for mesofauna. Microfauna were also involved in the internal colonisation of pine needles: cyst and naked amoebae (Protozoa), nematodes (Nematoda), rotifers (Rotifera). Among these groups, the feeding activity of earthworms and box
<figure><img src="image_50.png" /><figcaption>Fig. 357: Oribatid faeces, detail showing persistence of hyphae of *Cenococcum geophilum* (CP); Fig. 358: Idem, overview of a small excrement showing browning of finely ground pine material in the inner part (CP); Fig. 359: Idem, detail of a large excrement showing more coarsely ground pine material (CP); Fig. 360: Idem, detail showing the persistence of brown spherules from pine needle tissues (CP); Fig. 361: Development of chroococcal Cyanophyceae at the periphery of an oribatid excrement (CP); Fig. 362: Bacterial development at the inside of a small oribatid excrement (CP); Fig. 363: Sciarid faeces, detail showing remains of pine epidermis (stomatal guard cells) (CP); Fig. 364: Idem, detail showing chroococcal Cyanophyceae at the periphery (CP)</figcaption></figure>

CP = phase contrast; length of segment = 50 µm
mites was dominant. Both groups did not process pine needles in the same manner. While earthworms incorporated pine needle material with moss, pollen, and fungal material (among others) in their faeces, which were deposited in the environment, box mites accumulated their faeces at the inside of pine needles, only internal tissues being consumed.

There was a neat impact of animals on cytoplasms, whether of plant or microbial origin. This was not the case for cell walls. Hyaline fungal walls were digested by all animals groups, to the exception of sciarid larvae, but plant cell walls were degraded only by sciarid larvae and box mites. Hydrolysis of cellulose could be suspected to occur in sciarid larvae, but box mites transformed cellulose by another process, without solubilising it. In the latter case cellulose became brown and lost its transparency and refringence, but did not disappear as solid matter. Since this was the result of observations, without any dosage or chemical characterisation, it cannot be concluded definitely that there was digestion of cellulose in the former case (sciarids) and humification in the latter case (oribatids), although this was highly probable. Anyhow, a strong impact of both groups on cellulosic cell walls by is beyond of doubt. Concerning melanised fungal walls (*Cenococcum geophilum* for the main) it should be noted that only a limited array of oribatid mites belonging to the Camisiidae family (*Platynothrus peltifer*, *Nothrus sylvestris*) were able to transform this highly recalcitrant material.

Despite of the fact that animal activity was much higher in F₁ than in the overlying layer L₂, it should be noted that most plant debris, when not consumed by soil animals, did not change further. Most transformations of the plant material took place in animal guts and faeces. A great variety of microorganisms was observed (bacteria, algae, fungi), with an accumulation of empty fungal walls, whether hyaline or melanised. However, most microbial development was that of ectomycorrhizal fungi of pine. Bacteria were in lower numbers in F₁, and animal faeces did not seem to be a favourable micro-habitat for them. Concerning algae, Cyanophyceae were in lower numbers compared to overlying layers, but this decrease was less pronounced for Chlorophyceae. A negative impact of ectomycorrhizal fungi on bacterial populations could be suspected from their concomitant increase and decrease with depth, respectively.

## ACKNOWLEDGEMENTS

This work could not have been achieved without the participation of several colleagues who helped me to identify faunal and microbial specimens. In particular, I want to acknowledge Georges Wauthy, who identified oribatid mites, the most species-rich animal group. Many thanks are also devoted to Marie-Madeleine Coûteaux, Marie-France Roquebert and Jacques Boidin for their precious help. Many others were acknowledged directly in the text.
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