# Can subfossil insects complement pedoanthracology in reconstructing the past trajectories of old-growth forests? A study case from the Northern Central Pyrenees (France)

Sarah Parrilla, Mélanie Saulnier, Laurent Larrieu, Lionel Valladares, Valentina Pescini, Pierre Moret, Vanessa Py-Saragaglia

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## ► To cite this version:

Sarah Parrilla, Mélanie Saulnier, Laurent Larrieu, Lionel Valladares, Valentina Pescini, et al. Can subfossil insects complement pedoanthracology in reconstructing the past trajectories of old-growth forests? A study case from the Northern Central Pyrenees (France). Journal of Archaeological Science: Reports, 2026, 69, pp.105495. 10.1016/j.jasrep.2025.105495. hal-05381697

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https://hal.science/hal-05381697v1

Submitted on 25 Nov 2025

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# Can subfossil insects complement pedoanthracology in reconstructing the past trajectories of old-growth forests? A study case from the Northern Central Pyrenees (France)☆

Sarah Parrilla<sup>a,b,c,*</sup> ID, Mélanie Saulnier<sup>b</sup>, Laurent Larrieu<sup>d,e</sup>, Lionel Valladares<sup>d</sup>, Valentina Pescini<sup>f</sup>, Pierre Moret<sup>a</sup>, Vanessa Py-Saragaglia<sup>g</sup>

## ARTICLE INFO

### Keywords:

- Old-growth forest soils
- Insect death assemblages
- Cuticle degradation
- Absolute and relative dating
- Holocene forest trajectories

## ABSTRACT

The presence of insect remains preserved in soils has the potential to serve as a complementary proxy to charcoal, facilitating the reconstruction of Holocene forest trajectories at high spatial resolution. Six pits were dug at three old-growth forest sites (two per site) in the Central Pyrenees (France). Insect remains and charcoal were collected in each soil layer, following the pedoanthracological method usually conducted in similar mountain contexts. Radiocarbon dating was performed on a selection of both insects and charcoal, and a time-since-death index was developed to evaluate the degradation stage and relative age of the insect remains. Insect remains were present in most layers, but were more abundant in the upper ones, as with charcoal. Whereas radiocarbon dating did not work on individual insect remains, the time-since-death index showed a consistent relationship between increasing degradation and increasing depth. Saproxylic beetles, which are key indicators of the maturity of old-growth forests, were poorly preserved in the soils studied, but some of the other beetles identified at genus or species level provided useful information on past forest openness.

## 1. Introduction

Old-growth forests (OGFs) are attracting new interest because of the major role they play in mitigating climate change (Colangelo et al., 2021), thanks to their carbon storage capacity (Luyssaert et al., 2008; Stephenson et al., 2014) and their rich biodiversity (Di Marco et al., 2019), particularly related to deadwood and tree-related microhabitats, which are key resources for thousands of forest-dwelling species (Stokland et al., 2012; Larrieu et al., 2018). Currently, OGFs represent a small part of the European forest cover, less than 3 %, mainly concentrated in boreal and mountain areas (Sabatini et al., 2018, 2021). New interdisciplinary approaches have recently been implemented to better understand the long-term history of OGFs, characterising the natural

processes and the role of past societies in the formation of these unique ecosystems (Latalowa et al., 2015; Py-Saragaglia et al., 2020; Larrieu et al., 2023; Py-Saragaglia et al., 2025). Presently, the predominant approach for conducting Holocene reconstructions of vegetation at very high spatial resolution entails the examination of charcoal preserved within soils (also called “pedoanthracology”) (e.g. Talon, 2010; Cunill et al., 2015; Py-Saragaglia et al., 2017; Saulnier et al., 2020). Soil charcoal are inherited from Holocene fires whose regime has a variable and non-continuous frequency depending on climatic oscillations, vegetation changes and also human activity mainly from the last 3000 years (Rius et al., 2011). Consequently, the use of soil charcoal analyses to reconstruct the local vegetation history is not feasible on a continuous basis. Therefore, it is necessary to identify a complementary proxy that

<footnote><sup>a</sup> TRACES UMR 5608, Université de Toulouse, France</footnote>

<footnote><sup>b</sup> GEODE, UMR 5602, CNRS, Université de Toulouse, France</footnote>

<footnote><sup>c</sup> LASA-Université degli studi di Genova, Italy</footnote>

<footnote><sup>d</sup> DYNAFOR UMR 1201, PURPAN, Université de Toulouse, France</footnote>

<footnote><sup>e</sup> CNPF-CRPF Occitanie, France</footnote>

<footnote><sup>f</sup> ICAC-Institut Català d'Arqueologia Clàssica, Tarragona, Spain</footnote>

<footnote><sup>g</sup> IRAMAT-LMC, UMR 7065, CNRS, Université de Technologie Belfort-Monbéliard, France</footnote>

<footnote>* This article is part of a special issue entitled: ‘ANTHRACO’ published in Journal of Archaeological Science: Reports.</footnote>

<footnote>* Corresponding author at: TRACES UMR 5608, Université de Toulouse, France.</footnote>

<footnote>E-mail address: sarahparrilla.pro@gmail.com (S. Parrilla).</footnote>
<figure><img src="image_5.png" /><figcaption>Fig. 1. Location of the study areas and the pits discussed in this paper (author: S. Ladet). Black triangles indicate ancient charcoal-kiln terraces; red crosses indicate soil-sampling pits; green dots indicate pastoral huts. Dark-green areas represent forested zones, and light-green areas represent agro-pastoral zones.</figcaption></figure>

can fill in the gaps.

Insects constitute an important component of forest biodiversity (Samways, 2020). They occupy all strata of the forest, from the ground to the canopy, and their assemblages can be used to characterise local environmental conditions. They provide information on forest composition, tree density, amount of wood and bark debris, or natural/anthropogenic disturbances (Hill, 1993; Lindbladh et al., 2013; Schafstall et al., 2020a). Saproxylic taxa, in particular, are valuable indicators of the degree of maturity of the stand (Hill, 1993; Harding and Rose, 1995). Assemblage composition can vary greatly depending on canopy cover, particularly among the ground beetle family (Carabidae), due to the ecological specialisation of most species (Rainio and Niemelä, 2003).

Subfossil insect remains preserved in non-waterlogged soils have

been rarely studied, as the destructive action of fungi and bacteria within oxidized sediments impairs their preservation (Coope, 2004; Kenward, 2009; Elias, 2010). However, depending on environmental factors, fragments of dead insects, albeit often in small numbers, can be preserved for extended periods in ancient soils. Previous research conducted in the central French Pyrenees has provided sufficient quantities of insect remains from soils to allow joint analysis with charcoal (Moret et al., 2022). In the Apennines, radiocarbon dating was performed on beetle remains found in a mountain soil at a depth of 0.7 m (Compostella et al., 2013). In addition, at low altitudes in Oceania, ancient insect remains have been recovered from soils (Liebherr and Porch, 2015; Porch et al., 2009).

This research field, however, is nascent and exploratory in nature,
<table><caption>**Table 1**
General informations about the sampling pits and layers.</caption><thead><tr><th>Site</th><th>Pit</th><th>Area</th><th>Code</th><th>Coordinate</th><th>Alt. masl</th><th>Slope</th><th>Hydr.</th><th>Layer</th><th>pH</th><th>Deep</th><th>Wet weight (g)</th></tr></thead><tbody><tr><td rowspan="12">Barrada</td><td rowspan="3">1</td><td rowspan="3">Near pastoral zone</td><td rowspan="3">BARP1</td><td rowspan="3">N 42°48'35.413" E 0°1'50.721"</td><td rowspan="3">1600</td><td rowspan="3">75</td><td>0</td><td>I</td><td></td><td>0-25 cm</td><td>2610</td></tr><tr><td>0</td><td>II</td><td>4.9</td><td>10-45 cm</td><td>4348</td></tr><tr><td>0</td><td>III</td><td></td><td>15-80 cm</td><td>4420</td></tr><tr><td rowspan="5">2</td><td rowspan="5">Heart of the stand</td><td rowspan="5">BARP2</td><td rowspan="5">N 42°48'35.384" E 0°1'57.792"</td><td rowspan="5">1600</td><td rowspan="5">60</td><td>6</td><td>IV</td><td></td><td>50-110 cm</td><td>3862</td></tr><tr><td>0</td><td>I</td><td></td><td>0-27.5 cm</td><td>1847</td></tr><tr><td>0</td><td>II</td><td>5.2</td><td>10-50 cm</td><td>4484</td></tr><tr><td>0</td><td>III</td><td></td><td>35-95 cm</td><td>4504</td></tr><tr><td>0</td><td>IV</td><td></td><td>50-130 cm</td><td>2956</td></tr><tr><td rowspan="12">Bois-Neuf</td><td rowspan="3">1</td><td rowspan="3">Heart of the stand</td><td rowspan="3">BOIP1</td><td rowspan="3">N 42°45'24.926" E 0°38'7.331"</td><td rowspan="3">1700</td><td rowspan="3">65</td><td>0</td><td>I</td><td></td><td>0-15 cm</td><td>1381</td></tr><tr><td>0</td><td>II</td><td>3.9</td><td>10-25 cm</td><td>2221</td></tr><tr><td>0</td><td>III</td><td></td><td>12.5-65 cm</td><td>2571</td></tr><tr><td rowspan="5">2</td><td rowspan="5">Near pastoral zone</td><td rowspan="5">BOIP2</td><td rowspan="5">N 42°45'28.523" E 0°38'52.159"</td><td rowspan="5">1700</td><td rowspan="5">35</td><td>0</td><td>IV</td><td></td><td>50-90 cm</td><td>3079</td></tr><tr><td>0</td><td>I</td><td></td><td>0-2.5 cm</td><td>756</td></tr><tr><td>0</td><td>II</td><td>4</td><td>2.5-5 cm</td><td>2390</td></tr><tr><td>0</td><td>III</td><td></td><td>5-15 cm</td><td>2466</td></tr><tr><td>0</td><td>IV</td><td></td><td>10-40 cm</td><td>3946</td></tr><tr><td rowspan="12">Burat</td><td rowspan="3">1</td><td rowspan="3">Near pastoral zone</td><td rowspan="3">BURP1</td><td rowspan="3">N 42°52'8.08" E 0°39'56.084"</td><td rowspan="3">1400</td><td rowspan="3">30</td><td>10</td><td>I</td><td></td><td>0-5 cm</td><td>349</td></tr><tr><td>10</td><td>II</td><td>3.7</td><td>5-15 cm</td><td>2100</td></tr><tr><td>3</td><td>III</td><td></td><td>15-25 cm</td><td>4757</td></tr><tr><td rowspan="5">2</td><td rowspan="5">Heart of the stand</td><td rowspan="5">BURP2</td><td rowspan="5">N 42°52'24.182" E 0°39'55.274"</td><td rowspan="5">1200</td><td rowspan="5">75</td><td>10</td><td>IV</td><td></td><td>25-50 cm</td><td>5612</td></tr><tr><td>5</td><td>V-1</td><td></td><td>50-65 cm</td><td>5346</td></tr><tr><td>5</td><td>V-2</td><td></td><td>65-80 cm</td><td>5541</td></tr><tr><td>0</td><td>I</td><td></td><td>0-5 cm</td><td>3168</td></tr><tr><td>0</td><td>II</td><td>4.2</td><td>0-30 cm</td><td>3643</td></tr><tr><td>0</td><td>III</td><td></td><td>5-50 cm</td><td>3815</td></tr><tr><td>0</td><td>IV</td><td></td><td>45-90 cm</td><td>4634</td></tr></tbody></table>

largely due to preservation biases related to the uneven degradation of insect cuticles under variable soil conditions. One of the key aspects to be clarified concerns establishing whether insect remains preserved in

soils are truly ancient. The complexity of this archive also lies in the effects of bioturbation, which compromises the stratigraphic integrity of soils and makes an assemblage-based analysis impossible. Radiocarbon

<figure><img src="image_6.png" /><figcaption>**Fig. 2.** Profiles of the six pits excavated in the three OGFs.</figcaption></figure>
dating of insect remains is also challenging in this context. Previous studies have resorted to radiocarbon dating on groups of individuals originating from a single stratigraphic level (Elias & Toolin, 1990; Tripp et al., 2004) or from the same soil layer (Compostella et al., 2013), which conveys the risk of dating together non-contemporaneous individuals. Dating individual remains appears more suitable in a soil context, but it has rarely been applied, and its results are inconsistent (Panagiotakopulu et al., 2015), due to the very low amount of carbon preserved in fossil cuticles (Haines et al., 2023; Thil et al., 2024).

This exploratory study aims to adapt methodological protocols to the specific nature of subfossil insect remains and to assess the potential of combining them with charcoal to improve reconstructions of long-term OGF dynamics. Since insect presence is not linked to fire events, it offers an independent line of evidence that can complement charcoal-based reconstructions of local vegetation dynamics, particularly for the last few centuries, which are often poorly documented by soil charcoal. We therefore investigated soil insect remains from pedoanthracological pits at three OGF sites on the northern slope of the central Pyrenees, with the aim of: (i) assessing the occurrence and preservation state of insect remains across different soil layers; (ii) evaluating the potential of specific taxa as indicators of past vegetation cover; and (iii) testing several approaches to estimate the age of the remains, including absolute radio-carbon dating using the AMS method (applied to individual sclerites and pooled samples) and relative age estimation based on the degree of post-mortem degradation of the cuticular structures.

## 2. Materials and methods

### 2.1. Study area

This study was carried out in three well-preserved old-growth fir-beech forest sites located on the northern slope of the central Pyrenees: Barrada (45.9 ha, Gèdre-Gavarnie, Hautes-Pyrénées), Bois-Neuf (133 ha, Saint-Mamet, Haute-Garonne) and Burat (286 ha, Marignac, Haute-Garonne). All these forests are located close to active grazing lands whose use may have ecological effects in the forest contact area (Fig. 1).

The three forest sites encompass the montane fir-beech forest belt and the lower subalpine fir forest belt. Probably because of their northern exposure and altitude, but also because of their forest history, the three sites are currently composed of silver fir-dominated (Abies alba Mill.) stands with sparse beech (Fagus sylvatica L.) and few pioneer and

post-pioneer trees as birch (Betula spp.), mountain ash (Sorbus aucuparia L.), and maple (Acer spp., etc.). Some archaeological sites have been identified just near the pits: 20 ancient Charcoal Kiln terraces (CK, 18 of which have been dated from 1262-1061 cal BP to the contemporary period and 4 undated pastoral huts (Fig. 1)) (Py-Saragaglia et al., 2025).

Two pedoanthracological pits were dug in each forest, one from the heart of the OGFs, another just below an open pastoral active zone, and also for Barrada and Bois-Neuf a small altitudinal variance, more important at the Burat site (Py-Saragaglia et al., 2025). Bearing in mind that the overall slope of the sites is very steep, we have chosen as flat an area as possible. BURP1 is located on a small flat area (30% slope) at 1,400 m above sea level (hereafter masl) and 60 m away from a large open area. BURP2 is located at 1,200 masl on a relatively steep slope (75% slope). Four CKs have been found near BURP1 (Fig. 1). BOIP1 was dug on a steep slope area (65% slope) at 1,700 masl and BOIP2 in a flat area (35% slope) at 1,700 masl and 60 m away from the pastoral zone; three CKs have been found near the BOIP2 (Fig. 1). BARP1, at an altitude of 1,600 masl, and BARP2, at an altitude of 1,600 masl, were also dug on steep slopes of 75% and 60% respectively. BARP1 is the closest to the pastoral zone (350 m). Four CKs have been found near BARP1 and one near BARP2 (more details about these archaeological sites and current vegetation in Py-Saragaglia et al., 2025) (Fig. 1).

The pits were dug and described following the pedoanthracological method applied in lowland and mountain forest contexts (Saulnier et al., 2020; Robin et al., 2021). In each pit, depending on the layer thickness, about 0.5 to 5 kg of soil were taken per sampling layer, corresponding to a homogeneous soil layer (description of each sampling layer in Py-Saragaglia et al., 2025) (Table 1, Fig. 2).

The Barrada pits contain the longest soil sequences and also the highest concentration of large rocks, particularly in BARP2 (Fig. 2). BOIP2 contains medium rocks throughout its sequence. Medium rocks are also found in the uppermost layer of BOIP1 (Fig. 2). Soil materials are predominantly silty and/or clayey. Additionally, many layers exhibit fluffy or bio-microstructured structures. These structures make the soil particularly loose, enhancing aeration and drainage. All sampled soils, even those within the same stand, are developed on different substrates.

Hydromorphy varies between the pits in the OGFs (Table 1). BARP2, BOIP1, BOIP2, and BURP2 show no evidence of hydromorphy, unlike BARP1 and BURP1 (Table 1). In addition, the pH of all the layer II for each pit was measured in a laboratory. All the layers II have an acidic pH, ranging from 3.7 (BURP1) to 4.9 (BARP1) (Table 1).

<caption>**Table 2**</caption>

TSD Indicators for Coleoptera remains in forest contexts. (+) presence, (−) absence, (−/+) indiscriminate, (++) strong alteration.

<table><thead><tr><th></th><th>Stage 0</th><th>Stage 1</th><th>Stage 2</th><th>Stage 3</th></tr></thead><tbody><tr><td>1. Disaggregation of the exoskeleton</td><td></td><td></td><td></td><td></td></tr><tr><td>1.1. Segment disconnection</td><td>−/+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>1.2. Sclerite disconnection</td><td>−/+</td><td>−/+</td><td>+</td><td>+</td></tr><tr><td>2. Loss of delicate organs</td><td></td><td></td><td></td><td></td></tr><tr><td>2.1. Disappearance of tarsi and article of the antennae</td><td>−</td><td>−/+</td><td>+</td><td>+</td></tr><tr><td>2.2. Loss of bristles</td><td>−</td><td>−</td><td>+</td><td>+</td></tr><tr><td>2.3. Disappearance of eyes and mouth parts</td><td>−</td><td>−</td><td>+</td><td>+</td></tr><tr><td>2.4. Squamulae fall off</td><td>−</td><td>−</td><td>+</td><td>++</td></tr><tr><td>3. Colour alteration</td><td></td><td></td><td></td><td></td></tr><tr><td>3.1. Loss of metallic reflections</td><td>−</td><td>−</td><td>+</td><td>++</td></tr><tr><td>3.2. Colour change (e.g. from brown to yellow)</td><td>−</td><td>−</td><td>+</td><td>++</td></tr><tr><td>4. Cuticle altération</td><td></td><td></td><td></td><td></td></tr><tr><td>4.1. Deformation of the teguments</td><td>−</td><td>−</td><td>−/+</td><td>+</td></tr><tr><td>4.2. Loss of tegument rigidity</td><td>−</td><td>−</td><td>−/+</td><td>+</td></tr><tr><td>4.3. Scratches on cuticle</td><td>−/+</td><td>−/+</td><td>+</td><td>++</td></tr><tr><td>4.4. Punctures on cuticle</td><td>−</td><td>−</td><td>+</td><td>++</td></tr><tr><td>4.5. Circular and linear markings</td><td>−</td><td>−</td><td>−</td><td>+</td></tr></tbody></table>

### 2.2. Laboratory treatment and identification

Soil samples were weighed still wet before being wet-sieved (maintaining the original moist and cool conditions of the sediment is essential for the preservation of insect remains) using a column of sieves with 4-, 2- and 0.8-mm mesh (Saulnier et al., 2020). To calculate the original dry weight of the soil samples, required to calculate anthracomasses, we first collected a small portion of soil (c. 50 g) and dried it. For ease of comparison of the two proxies, it was decided not to use a finer mesh (0.3 mm; Elias, 2010) for the entomofauna remains, because those extracted in the 0.8 mesh were already highly fragmented and hard to identify to genus. After sieving, the remaining organic fraction was observed under a binocular microscope (Leica MZ 125) to extract insect pieces and charcoal (for more details about charcoal analysis, see Py-Saragaglia et al., 2025).

Sufficiently preserved insect remains (i.e. those retaining morphological features) were identified using the entomological collection of Toulouse University (TRACES laboratory). In most cases, insect remains have been identified down to the genus level, with the exception of Carabidae, whose identification has often led to species determination. Then, we calculated the minimal number of individuals (MNI) of each pit based on the calculation of lateralized anatomical elements (Morlan and Matthews, 1983; Buckland, 2000; Schafstall et al., 2020b).
<figure><img src="image_7.png" /><figcaption>**Fig. 3.** Example of indicators on ancient insects remains. A) short, superficial scratches, B) and C) numerous deep scratches, D) oval-circular marks, E) pre-punctures, F) punctures, G) linear marks, H) low number of pre-punctures, I) very numerous pre-punctures, J) very numerous punctures, and colour alterations.</figcaption></figure>

## 2.3. Indicators of insect cuticle degradation

To classify the degradation of insect remains, we used a time since death (TSD) index. This TSD is based on the taphonomic observation of

previous studies (Carrott et al., 1996; Duncan et al., 2003; Lindroth, 1948; Kenward and Large, 1998; Morlan and Matthews, 1983; Plotnick, 1986). We did not use the well-developed grid proposed by Kenward and Large (1998) because it was designed for insect assemblages from
archaeological contexts and was unsuitable for our purpose. We established four stages of degradation (0–3), based on indicators of the postmortem degradation of the insect body: (i) disarticulation of the exoskeleton; (ii) loss of delicate organs; (iii) colour alteration; (iv) cuticle alteration.

At stage 0 (S0), the body is fully preserved or, if partly fragmented, the segments still possess fragile organs as antennae and setae. In the case of ground-dwelling species, slight scratches due to their way of life (burrowing habit) may be observed, which can be easily distinguished from post-mortem scratches. In these cases, death is inferred to be very recent (a few months to a few years ago) (Table 2).

Stage 1 (S1) is characterised by incipient segment disconnection caused by the disappearance of muscles and soft tissues. Loss of delicate organs like the tarsi and articles of the antennae can be observed. Sensory bristles can still be present. At this stage, the death of the insect is inferred to be relatively recent (Table 2).

At stage 2 (S2), the exoskeleton has lost all its connections as well as delicate organs like bristles and eyes. Colour alterations are observed, due to a loss of pigments contained in the cuticle, which is altered (Fig. 3). Some insect remains with a metallic sheen may not be affected by this criterion because their colour is structural and not pigmentary. Pre-punctures can be found (Fig. 3); they are due to well-drained sediments (Lindroth, 1948; Morlan and Matthews, 1983). At this stage, post-mortem scratches can also be found (Table 2, Fig. 3). The death of the insect is inferred to be relatively ancient.

Stage 3 (S3) is defined by a generally patinated appearance of the sclerite, loss of material, total alteration of colour and presence of punctures covering the whole remain (Fig. 3). Generally, at this stage the sclerite is fragmented and extremely fragile. Broad and deep post-mortem scratches are frequent. Due to the presence of ectomycorrhizal fungi in a forest context, signs of enzymatic degradation (circular and linear marking) are observed (Santos-Silva et al., 2011) (Table 2, Fig. 3). The death of the insect is inferred to be ancient.

## 2.4. Radiocarbon dating

Nineteen charcoal fragments and eleven individual insect remains were selected for radiocarbon dating at the Poznan laboratory, focusing preferentially on remains extracted from deep layers. When possible, insect and charcoal remains were extracted from the same sampling layers.

Palaeoecological and archaeological studies typically gather several insect remains together to have enough carbon material to achieve radiocarbon dating. Even though small quantities of material may lead to dating errors (Hodgins et al., 2001), we attempted to radiocarbon date individual insect remains using the AMS method. Due to insufficient carbon in the heavily degraded remains, we only selected insect remains that were not heavily degraded for dating purposes.

To mitigate potential biases associated with radiocarbon dating of individual sclerites, a composite sample consisting of several insect remains was also radiocarbon dated. We are aware that the aggregation of several insects introduces substantial interpretation biases, but this test was only performed to assess whether the insects were contemporary or relatively old, in case of unsuccessful results on individual remains. We selected insect sclerites showing a high degree of degradation (TSD stage 2 or 3), probably resulting from prolonged burial within the soil. We determined that the remains from layer III of BURP1 would be the most suitable for this analysis, as it contained a majority of TSD stage 2 specimens, with a few stage 3 specimens. The selected specimens included Carabidae (Pterostichus pumilio and Harpalus sp.) and Curculionidae, chosen for their thick cuticle, which provides sufficient carbon for radiocarbon dating. A total of about twenty sclerites were pooled for radiocarbon dating.

<caption>**Table 3**</caption>

Pits and number of remains found in each layer (a = determinable remains, b = non determinable remains).

<table><thead><tr><th>Pit</th><th>Layer</th><th>a</th><th>b</th></tr></thead><tbody><tr><td rowspan="4">BURP1 (75% slope)</td><td>I</td><td>15</td><td>2</td></tr><tr><td>II</td><td>5</td><td>0</td></tr><tr><td>III</td><td>1</td><td>0</td></tr><tr><td>IV</td><td>0</td><td>0</td></tr><tr><td rowspan="4">BURP2 (60% slope)</td><td>I</td><td>71</td><td>45</td></tr><tr><td>II</td><td>26</td><td>10</td></tr><tr><td>III</td><td>1</td><td>0</td></tr><tr><td>IV</td><td>2</td><td>0</td></tr><tr><td rowspan="4">BOIP1 (65% slope)</td><td>I</td><td>40</td><td>9</td></tr><tr><td>II</td><td>35</td><td>10</td></tr><tr><td>III</td><td>0</td><td>3</td></tr><tr><td>IV</td><td>0</td><td>0</td></tr><tr><td rowspan="5">BOIP2 (35% slope)</td><td>I</td><td>57</td><td>34</td></tr><tr><td>II</td><td>45</td><td>47</td></tr><tr><td>III</td><td>18</td><td>0</td></tr><tr><td>IV</td><td>29</td><td>6</td></tr><tr><td>V</td><td>2</td><td>0</td></tr><tr><td rowspan="5">BURP1 (30% slope)</td><td>I</td><td>21</td><td>13</td></tr><tr><td>II</td><td>56</td><td>82</td></tr><tr><td>III</td><td>105</td><td>94</td></tr><tr><td>IV</td><td>7</td><td>1</td></tr><tr><td>V</td><td>1</td><td>0</td></tr><tr><td rowspan="4">BURP2 (75% slope)</td><td>I</td><td>70</td><td>101</td></tr><tr><td>II</td><td>26</td><td>6</td></tr><tr><td>III</td><td>16</td><td>12</td></tr><tr><td>IV</td><td>5</td><td>8</td></tr></tbody></table>

# 3. Results

## 3.1. Amount and distribution of insects remains and charcoal

We found a total of 1137 insect remains in the 6 pits. The abundance of insect remains is higher in the pits located in the flattest areas (i.e. BURP1 and BOIP2), compared to pits dug on steep slopes (i.e. BARP1, BARP2, BOIP1 and BURP2). The superficial layers contained more insect remains than the deeper layers. The number of insect remains decreases notably from layer II downwards in all pits except for BOIP2 (layer III) and BURP1 (layer IV) (Table 3).

The vertical distribution of insect remains within the pits and across the sampling layers aligns with the distribution of the charcoal expressed in anthracomasses per layer (mg of charcoal per kg of dry sediment) (Fig. 4). In general, the top three layers have yielded higher concentrations of charcoal than the lower ones. BOIP1 provided a particularly large amount of charcoal concentrated in the second top layer. Given the small volume of sediment sampled from layers I and II in BURP1, the low quantity of insect and charcoal is likely underestimated and should be interpreted with appropriate caution (Table 1).

## 3.2. Identified insect taxa

Due to the high rate of fragmentation of the remains, only 656 remains (out of 1137, 58%) were identified from the family down to the species level (Tables 4–6, Fig. 5). A total of 42 taxa were identified, mostly Coleoptera that represent 97% of the dataset, with two dominant families: Curculionidae and Carabidae, respectively representing 54 % and 36% of the Coleoptera data set. The dataset is clearly dominated by phytophagous forest taxa living in the canopy or in the forest vegetation, mostly weevils (Otiorhynchus and Barynotus) both identified to genus, and by ground-active predators in all pits (mostly Carabidae as Pterostichus pumilio (MNI = 70) (Table 4–6)). We also found Triplax rufipes (MNI = 2) (Erotylidae), a specialist species living on deciduous tree saproxylic fungi (Fomes fomentarius or Pleurotus sp.) in BOIP2 (Table 5).

Only a few remains of saproxylic beetles have been found (n = 23,8% of MNI), mainly in layers I and II (only *Quedius* sp. was found in a layer III), while we expected to find them in a more significant number due to
<figure><img src="image_8.png" /><figcaption>Fig. 4. Anthracomasses found in the six pits of the three OGFs.</figcaption></figure>

<table><caption>**Table 4**
Insect taxa collected in BARP1 and BARP2, with R = number of remains.</caption><thead><tr><th rowspan="3"></th><th colspan="4">BARP1</th><th colspan="4">BARP2</th></tr><tr><th colspan="2">I</th><th colspan="2">II</th><th colspan="2">III</th><th colspan="2">IV</th></tr><tr><th>R</th><th>MNI</th><th>R</th><th>MNI</th><th>R</th><th>MNI</th><th>R</th><th>MNI</th></tr></thead><tbody><tr><td><strong>Coleoptera</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>Carabidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Abox parallelepipedus</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Carabus splendens</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td></tr><tr><td>Pterostichus amoenus</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td></tr><tr><td>Pterostichus pumilio</td><td>2</td><td>2</td><td>3</td><td>2</td><td>/</td><td>/</td><td>5</td><td>1</td></tr><tr><td>Carabidae undeter.</td><td>2</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Cerambycidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Cerambycidae undeter.</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Curculionidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Barynotus sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>7</td><td>4</td></tr><tr><td>Otiorhynchus sp.</td><td>1</td><td>1</td><td>1</td><td>1</td><td>/</td><td>/</td><td>18</td><td>3</td></tr><tr><td>Polydrusus sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td></tr><tr><td>Curculionidae undeter.</td><td>3</td><td>1</td><td>/</td><td>/</td><td>1</td><td>/</td><td>26</td><td>2</td></tr><tr><td><strong>Elateridae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Ampedus sp.</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Athous sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>2</td><td>2</td></tr><tr><td><strong>Staphylinidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Ocupus olens</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Trogossidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Thymalus limbatus</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td></tr><tr><td><strong>Diptera</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Muscidae undeter.</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>7</td><td>7</td></tr><tr><td><strong>Hymenoptera</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Apocrita undeter.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td></tr><tr><td><strong>Formicidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Formica rufa</td><td>2</td><td>2</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Formicidae undeter.</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Total</td><td>15</td><td>11</td><td>5</td><td>4</td><td>1</td><td>0</td><td>70</td><td>24</td></tr></tbody></table>

the high maturity of the forest studied. They can be split into two groups (Bouget et al., 2019): saproxylic, with *Ampedus* identified to genus (Elateridae, BARP1), *Dasycerus sulcatus* (Staphylinidae, BURP2), *Hylastes* identified to genus (Curculionidae, BOIP2), and *Rhyncolus* identified to genus (Curculionidae, BOIP1), *Thymalus limbatus* (Trogossidae, BARP2), and micro-predators with *Quedius* (Staphylinidae, BURP1) and *Scydmaenus* (Staphylinidae, BURP2) both identified to

genus.

### 3.3. Identified tree taxa (Table 7)

Soil charcoal were predominantly dominated by fir (*Abies alba* Mill.) and Gymnosperma, with the frequent presence, even in layers with very low anthracomasses, of pioneering and post-pioneering species and
<table><caption>**Table 5**
Insect taxa collected in BOIP1 and BOIP2, with R = number of remains.</caption><thead><tr><th rowspan="3"></th><th colspan="4">BOIP1</th><th colspan="4">BOIP2</th></tr><tr><th colspan="2">I</th><th colspan="2">II</th><th colspan="2">III</th><th colspan="2">IV</th></tr><tr><th>R</th><th>MNI</th><th>R</th><th>MNI</th><th>R</th><th>MNI</th><th>R</th><th>MNI</th></tr></thead><tbody><tr><td><strong>Coleoptera</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>Carabidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Notiophilus biguttatus</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>2</td><td>1</td></tr><tr><td>Pterostichus amoenus</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Pterostichus pumilio</td><td>10</td><td>5</td><td>5</td><td>3</td><td>/</td><td>/</td><td>19</td><td>10</td></tr><tr><td>Pterostichus sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Carabidae undeter.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>/</td></tr><tr><td><strong>Chrysomelidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Alticinae undeter.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Curculionidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Barynotus sp.</td><td>3</td><td>2</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Hylastes sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Otiorhynchus sp.</td><td>8</td><td>2</td><td>17</td><td>3</td><td>/</td><td>/</td><td>5</td><td>2</td></tr><tr><td>Rhyncolus sp.</td><td>7</td><td>7</td><td>2</td><td>2</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Strophosoma melanogrammum</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>5</td><td>4</td></tr><tr><td>Curculionidae undeter.</td><td>5</td><td>1</td><td>6</td><td>1</td><td>/</td><td>/</td><td>6</td><td>1</td></tr><tr><td><strong>Elateridae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Athous sp.</td><td>1</td><td>1</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Elateridae undeter.</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Erotylidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Triplax rufipes</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Geotrupidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Anoplotrupes stercorosus</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>11</td><td>1</td></tr><tr><td><strong>Latridiidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Latridiidae undeter.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td></tr><tr><td><strong>Scarabaeidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Aphodius sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td></tr><tr><td>Scarabaeidae undeter.</td><td>1</td><td>1</td><td>1</td><td>1</td><td>/</td><td>/</td><td>3</td><td>1</td></tr><tr><td><strong>Staphylinidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Staphylinidae undeter.</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td></tr><tr><td><strong>Tenebrionidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Tenebrionidae undeter.</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Diptera</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Muscidae undeter.</td><td>2</td><td>2</td><td>/</td><td>/</td><td>/</td><td>/</td><td>2</td><td>2</td></tr><tr><td><strong>Hymenoptera</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>Formicidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Formicidae undeter.</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td></tr><tr><td>Total</td><td>40</td><td>23</td><td>35</td><td>14</td><td>0</td><td>0</td><td>56</td><td>24</td></tr></tbody></table>

associated shrublands, such as maple (Acer), birch (Betula), hazel (Cor- ylus) and Ericaceae (cf. *Rhododendron ferrugineum* L./Vaccinium) (Table 7). Mountain Ericaceae are particularly abundant and well rep- resented in the deeper layers of BURP1. They also occur in BARP2 and BOIP2. Surprisingly, beech charcoal remains were poorly represented, except in BARP2. Deciduous oak (*Quercus*) has been identified twice in BURP2 and ash tree (*Fraxinus*) once in BOIP2.

### 3.4. Preservation of insect remains and decay stages

We applied the TSD index to all the insect remains, including the unidentified ones, in order to observe the global distribution of the different degradation stages in the pits. The pits can be grouped into two main groups based on this decay index: group A, for pits containing almost only stage 1 remains, represented by BARP1, BARP2 and BOIP1; and group B, for pits containing S1 remains in superficial layers and S2 and S3 in the deepest layers, represented by BOIP2, BURP1 and BURP2 (Fig. 6).

In group A, BARP1 and BARP2 contained very few S2 remains (first visible traces of cuticle damage) and some S3 (badly altered cuticle). S2 was found in superficial layers, while the dataset is clearly dominated by S1 (unaltered cuticle and connection). In BOIP1, there are more insect remains classified in S2 and S3 than in the other pits of the group A, again in the upper layers (Fig. 6).

In group B, the upper layers are dominated by S1 remains, with few S0 (unaltered cuticle, connection and fragile organs still present) in BURP1 and BURP2. S1 decreased gradually with depth while S2 and S3

increased. This shift is well evidenced in BOIP2, from layer II down- wards (Fig. 6).

Overall, S3 is mainly represented in the deepest layers and is hardly observed in the most superficial layer. The few S1 elements found in the deeper layers are mainly small heads of *Pterostichus* and *Otiorhynchus* beetles. The S0 remains we found were two complete *Pterostichus pumilio* (one in BARP2 and another in BOIP1), probably collected alive during sampling or representing very recent deaths, and four larvae (which have burrowing habits), two of which are *Elateridae* (*Athous* sp.) (Table 4, Fig. 6).

### 3.5. Radiocarbon dating results

The carbon amount extracted from individual insect remains ranged from 0.023 to 0.441 mgC. Most of the eleven radiocarbon dates, all at stages S1 and S2 of cuticular degradation, fell within the contemporary period (Table 8). Only two insect remains yielded older dates: a *Pter- ostichus pumilio* (Carabidae) (TSD S2) from layer III of BURP1 (475–310 cal BP) and an *Otiorhynchus* sp. (Curculionidae) (TSD S2) from layer III of BOIP2 (470–302 cal BP).

The pooled sample of approximately twenty sclerites yielded a cali- brated age ranging from 495 to 315 cal BP, corresponding to the 15th- 17th centuries AD, with a carbon amount of 0.7 mgC.

Radiocarbon dates of charcoal remains covered the entire Holocene period, from 10550-10340 cal BP to 257–33 cal BP (Table 8). The three charcoal fragments which were radiocarbon dated to the early Holocene are identified as *Acer* sp., *Rhododendron ferrugineum* and a deciduous
<table><caption>**Table 6**
Insect taxa collected in BURP1 and BURP2, with R = number of remains.</caption><thead><tr><th rowspan="3"></th><th colspan="12">BURP1</th><th colspan="12">BURP2</th></tr><tr><th colspan="2">I</th><th colspan="2">II</th><th colspan="2">III</th><th colspan="2">IV</th><th colspan="2">V</th><th colspan="2">I</th><th colspan="2">II</th><th colspan="2">III</th><th colspan="2">IV</th></tr><tr><th>R</th><th>MNI</th><th>R</th><th>MNI</th><th>R</th><th>MNI</th><th>R</th><th>MNI</th><th>R</th><th>MNI</th><th>R</th><th>MNI</th><th>R</th><th>MNI</th><th>R</th><th>MNI</th><th>R</th><th>MNI</th></tr></thead><tbody><tr><td><strong>Coleoptera</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>Brentidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Apionini undeter.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Brentidae undeter.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>4</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Carabidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Abax parallelepipedus</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Bembidion sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>2</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Harpalus sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>11</td><td>7</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Leistus nitidus</td><td>/</td><td>/</td><td>/</td><td>/</td><td>3</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>2</td><td>2</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Pterostichus amoenus</td><td>4</td><td>2</td><td>2</td><td>1</td><td>24</td><td>13</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Pterostichus pumilio</td><td>5</td><td>2</td><td>9</td><td>7</td><td>16</td><td>10</td><td>4</td><td>1</td><td>/</td><td>/</td><td>15</td><td>12</td><td>1</td><td>1</td><td>1</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Pterostichus sp.</td><td>2</td><td>1</td><td>6</td><td>5</td><td>14</td><td>14</td><td>3</td><td>3</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Carabidae undeter.</td><td>1</td><td>/</td><td>4</td><td>/</td><td>7</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>4</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Chrysomelidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Chrysomelidae undeter.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>2</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Curculionidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Barynotus sp.</td><td>/</td><td>/</td><td>2</td><td>1</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Hylastes sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Otiorhynchus sp.</td><td>7</td><td>3</td><td>12</td><td>3</td><td>10</td><td>3</td><td>/</td><td>/</td><td>/</td><td>/</td><td>23</td><td>4</td><td>19</td><td>8</td><td>5</td><td>4</td><td>5</td><td>2</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Polydrusus sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>16</td><td>4</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Curculionidae undeter.</td><td>2</td><td>1</td><td>19</td><td>/</td><td>12</td><td>2</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>/</td><td>4</td><td>/</td><td>3</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Elateridae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Elateridae undeter.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Scarabaeidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Aphodius sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Scarabaeidae undeter.</td><td>/</td><td>/</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Staphylinidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Dasycerus sulcatus</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Heterothops sp.</td><td>/</td><td>/</td><td>1</td><td>1</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Quedius sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>2</td><td>2</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Scydmaenus sp.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>2</td><td>2</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Staphylinidae undeter.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Diptera</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Muscidae undeter.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>3</td><td>2</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td><strong>Hymenoptera</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>Formicidae</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Formicidae undeter.</td><td>/</td><td>/</td><td>/</td><td>/</td><td>1</td><td>1</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr><tr><td>Total</td><td>21</td><td>9</td><td>56</td><td>18</td><td>105</td><td>57</td><td>7</td><td>4</td><td>1</td><td>1</td><td>69</td><td>31</td><td>27</td><td>11</td><td>16</td><td>8</td><td>5</td><td>2</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td><td>/</td></tr></tbody></table>

Quercus, while during the modern period we identified *Fagus sylvatica* and *Acer* sp. Most charcoal pieces (14) were radiocarbon dated to the period from the Bronze Age to the Middle Age, including ten *Abies alba*, two *Fagus sylvatica* and two *Acer* sp.

# 4. Discussion

## 4.1. Chronological issues

Most of the radiocarbon dates obtained from insect sclerites submitted individually fall within the radiocarbon plateau spanning the modern and contemporary periods (zone Ia of Taylor et al., 1996). Three older dates (two from sclerites and one from a mixed assemblage) are situated on the plateau associated with the modern period (zone Ib of Taylor et al., 1996). These circumstances complicate the interpretation of the results due to the wide resulting calibrated age ranges.

By contrast, charcoal samples from the same pits and sampling layers span the entire Holocene. For example, in the deepest layer of Burat (V), charcoal radiocarbon dates range from 9884 to 8650 cal BP, while the associated sclerite yielded a much more recent date between 264 and 25 cal BP. Similarly, in layer III of Burat, insect remains were dated between 475 and 35 cal BP, whereas charcoal from the same layer ranged from 3063 to 1394 cal BP.

Discrepancies in radiocarbon dates of plant macrofossils, humic fractions, and insects have already been reported in the literature, including in stratified contexts (e.g., older in Elias & Toolin, 1990; Child & Wermer, 1999; younger in Hodgins et al., 2001; Walker et al., 2001).

However, the divergences observed have never reached the amplitude recorded in our study. Insect chitin is a molecule that exhibits marked instability (Elias, 2010) and high sensitivity to contamination, whether post-depositional or post-sampling (Panagiotakopulu et al., 2015; Wohlfarth et al., 1998). Hodgins et al. (2001) have shown that taphonomic processes and local depositional conditions influence such results. Another potential source of contamination lies in pre-sieving storage, although current pre-treatment procedures help reduce this bias (Panagiotakopulu et al., 2015; Tripp et al., 2004).

We consider it likely that the radiocarbon dates obtained are rejuvenated. Tripp & Higham (2010) recommend that reliable dating of insect chitin, with AMS, be performed on at least 1 mgC, which is substantially higher than the carbon mass yielded by the grouped remain sample (0.7 mgC), and much higher than the carbon obtained from individual remains (0.02 to 0.44 mgC). The date derived from the grouped sample is the oldest in our dataset, yet it cannot be regarded as fully reliable, as the carbon mass contained in an individual remain is greater the more recent it is, and consequently the overall date of the group of sclerites may be biased towards the date of the most recent individuals. This problem may similarly affect the results obtained by Compostella et al. (2013).

However, despite the overall inaccuracy of these radiocarbon dating results, most likely due to a systematic age underestimation (Haines et al., 2023; Holden et al., 2017), three dates obtained from individual remains (BURP1, layer III, 475–310 cal BP; BOIP2, layer III, 470–302 cal BP), and from the mixed assemblage (BURP1, layer III, 495–310 cal BP), suggest that sclerites of insects that died at least several centuries ago
<figure><img src="image_9.png" /><figcaption>**Fig. 5.** Some woodland species identified in the pits. A) *Abax parallelepipedus* (Piller & Mitterpacher, 1783) (Carabidae), B) *Carabus splendens* (Olivier, 1790) (Carabidae), C) *Leistus nitidus* (Duftschmid, 1812) (Carabidae), D) *Pterostichus amoenus* (Dejean, 1828) (Carabidae), E) *Pterostichus pumilio* (Dejean, 1828) (Carabidae), F) *Dasycerus sulcatus* (Brongniart, 1800) (Staphylinidae).</figcaption></figure>

(between the mid-15th and early 17th centuries) can be preserved in forest soils. On the other hand, there is little doubt that very recent dates obtained from upper layers on remains with a low degree of degradation (TSD grade S1) are correct and correspond to insects that were superficially buried by bioturbation.

Regarding relative chronology, the TSD index appears to substantiate a correlation between the extent of cuticle degradation and the depth of the layers where the remains were found. The deepest layers exhibit the highest amount of the most degraded insect remains (higher TSD values), which may indicate that they belong to older assemblages. Conversely, the least altered insect remains are concentrated in the uppermost layers of the sampling pits, probably reflecting recent assemblages. This index can therefore serve as a relative-age tool rather than an absolute dating method, particularly adapted to forest soils with good archiving conditions, i.e. advanced soils located on gentle slopes with low erosion and colluviation processes, somewhat analogous to stratigraphic contexts where similar indices have been implemented for archaeo-entomological purposes (Kenward & Large, 1998).

## 4.2. Differential preservation of insect taxa due to the burial and taphonomic processes

Studies performed in temperate lowlands have shown that good preservation of insect remains depends on the presence and maintenance of optimum conditions throughout and after the burial processes. Kenward (2009) described a dynamic process consisting in two stages: firstly, insect remains must be incorporated into the soil; secondly, the remains have to withstand the processes of soil dynamics and the action of time and taphonomic processes (Plotnick, 1986). Surface biological activity and run-off play an important role in the record of insect death assemblages. The same applies to the biological activity of the litter, which varies from one forest to another, but in general terms forest canopy limits the action of wind, moderates temperature fluctuations, and helps maintain ambient humidity.

Mountain forest soils are subject to two major phenomena: bioturbation and chemical degradation. Bioturbation involves top-down soil movements that can disrupt the stratigraphic integrity of
<figure><img src="image_10.png" /><figcaption>Fig. 6. Proportion (%) of insect fragments at different stages of degradation in each pit and sampling layer, along with the corresponding number of remains.</figcaption></figure>

result from greater mechanical pressure on the sclerites of large insects than in the case of small insects (fracturing the remains or making them easier to transport) or from increased predation on the living insect or its remains (Plotnick, 1986).

Surprisingly, only a few insect remains could be assigned to sap-
roxylic taxa, and they were all found in superficial layers. Because they
host a large amount of different types of dead wood at different stages of
decay, OGFs provide a wide range of resources for many saproxylic in-
sects (Stokland et al., 2012). However, they are not preserved in medium
and deep layers of the soil archive. Future studies will be needed to
investigate the factors underlying this absence.

4.3. Potential contribution of subfossil insects to palaeoecological reconstructions

As seen before, the study of soil-preserved insects faces many limi-
tations, thereby precluding their use as a standalone palaeoecological
proxy. Nonetheless, in contexts where insect remains are sufficiently
abundant and well preserved, they can complement charcoal data by
providing additional perspectives on forest dynamics, although not on
the same chronological scale, particularly at sites presenting pH condi-
tions that exclude bioturbation by earthworms, such as Burat (BURP1)
and Bois-Neuf (BOIP2).

At BURP1, charcoal data indicate long-term forest cover and open-
ing, while insect remains, though less securely dated, point to local

canopy openings consistent with this signal. While the charcoal provides
a reconstruction extending throughout the Holocene, the insect record,
as seen above, is less certain and most likely reflects the recent Holocene,
with a broader chronological uncertainty than charcoal data. Based on
charcoal, most of the canopy opening events mainly occurred during the
transition from the Bronze Age to the Iron Age and during the Middle
Ages, periods known for their high levels of anthropisation and human
activity in mountain areas. However, charcoal also provides evidence of
open landscape phases well before these periods, based on the presence,
in layer V of BURP1, of rhododendron and maple charcoal, both woody
species requiring a lot of light, which were dated to the early post-glacial
period (Mesolithic) (Py-Saragaglia et al., 2025). In the same layer, the
presence of an elytron of *Harpalus* sp., could be consistent with an open
phase. *Harpalus* is a carabid genus characteristic of open or semi-open
environments, although some individuals can occasionally be
observed within forested environments or at forest edges. At Burat, ac-
cording to a recent pitfall sampling of the current fauna, *Harpalus* are
absent inside the forest, though present in low numbers at the forest
edge (unpublished data).

In layer III of BURP1, which covers at least 2000 years (3063–1394 cal BP), the charcoal assemblage includes *Abies alba* and *Fagus sylvatica*, both characteristic of closed canopy conditions, but a phase of forest opening is evidenced by the presence of *Acer* sp., a post-pioneer taxon, which suggests a disturbance occurring before the transition between the Bronze Age and the Iron Age. In this period, human activity
<table><caption>**Table 8**
Radiocarbon dates from insects (name of taxa in bold) and charcoal remains.</caption><thead><tr><th>Pit</th><th>Lab. Code</th><th>Layer</th><th>Deep</th><th>Species</th><th>Date</th><th>Cal BP</th><th>Out of range</th><th>mgC</th><th>TSD</th></tr></thead><tbody><tr><td rowspan="3">BARP1</td><td>Poz-146896</td><td>II</td><td>10-45 cm</td><td>Pterostichus pumilio</td><td>113.99 ± 0.51</td><td>258-32</td><td>Yes</td><td>0.127</td><td>S1</td></tr><tr><td>Poz-157308</td><td>II</td><td>10-45 cm</td><td>Abies alba</td><td>3150 ± 30</td><td>3449-3263</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-156561</td><td>III</td><td>15-80 cm</td><td>Abies alba</td><td>1630 ± 30</td><td>1568-1409</td><td>No</td><td>–</td><td>/</td></tr><tr><td rowspan="3">BARP2</td><td>Poz-159551</td><td>II</td><td>10-50 cm</td><td>Fagus sylvatica</td><td>55 ± 30</td><td>257-33</td><td>Yes</td><td>–</td><td>/</td></tr><tr><td>Poz-157307</td><td>II</td><td>10-50 cm</td><td>Fagus sylvatica</td><td>111.42 ± 0.36</td><td>257-33</td><td>Yes</td><td>–</td><td>/</td></tr><tr><td>Poz-157261</td><td>II</td><td>10-50 cm</td><td>Abies alba</td><td>2435 ± 30</td><td>2700-2355</td><td>No</td><td>–</td><td>/</td></tr><tr><td rowspan="8">BOIP1</td><td>Poz-160042</td><td>I</td><td>0-15 cm</td><td>Fagus sylvatica</td><td>1380 ± 30</td><td>1349-1192</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-160041</td><td>I</td><td>0-15 cm</td><td>Abies alba</td><td>1435 ± 30</td><td>1371-1295</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-146894</td><td>II</td><td>10-25 cm</td><td>Elateridae</td><td>126.07 ± 0.38</td><td>261-27</td><td>Yes</td><td>0.441</td><td>S1</td></tr><tr><td>Poz-146895</td><td>II</td><td>10-25 cm</td><td>Curculionidae</td><td>106.55 ± 0.31</td><td>255-33</td><td>Yes</td><td>0.368</td><td>S1</td></tr><tr><td>Poz-148017</td><td>II</td><td>10-25 cm</td><td>Acer sp.</td><td>1950 ± 30</td><td>1986-1750</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-147651</td><td>II</td><td>10-25 cm</td><td>Abies alba</td><td>1355 ± 30</td><td>1340-1176</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-148018</td><td>III</td><td>12,5-65 cm</td><td>Abies alba</td><td>1215 ± 30</td><td>1262-1061</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-159552</td><td>III</td><td>12,5-65 cm</td><td>Acer sp.</td><td>2940 ± 35</td><td>3209-2966</td><td>No</td><td>–</td><td>/</td></tr><tr><td rowspan="8">BOIP2</td><td>Poz-157309</td><td>II</td><td>2,5-5 cm</td><td>Fraxinus sp.</td><td>275 ± 30</td><td>441-154</td><td>Yes</td><td>–</td><td>/</td></tr><tr><td>Poz-156505</td><td>III</td><td>5-15 cm</td><td>Abies alba</td><td>2525 ± 30</td><td>2740-2493</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-157251</td><td>III</td><td>5-15 cm</td><td>Otiorhynchus sp.</td><td>315 ± 35</td><td>470-302</td><td>No</td><td>0.123</td><td>S1</td></tr><tr><td>Poz-157095</td><td>IV</td><td>10-40 cm</td><td>Pterostichus pumilio</td><td>101.51 ± 1.43</td><td>254-39</td><td>Yes</td><td>0.045</td><td>S2</td></tr><tr><td>Poz-157263</td><td>V</td><td>30-60 cm</td><td>Pterostichus pumilio</td><td>100.61 ± 1.74</td><td>254-40</td><td>Yes</td><td>0.027</td><td>S2</td></tr><tr><td>Poz-157254</td><td>V</td><td>30-60 cm</td><td>Abies alba</td><td>2075 ± 30</td><td>2121-1942</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-146849</td><td>II</td><td>5-15 cm</td><td>Curculionidae</td><td>115.42 ± 0.32</td><td>259-31</td><td>Yes</td><td>0.328</td><td>S1</td></tr><tr><td>Poz-157310</td><td>II</td><td>5-15 cm</td><td>Abies alba</td><td>1085 ± 30</td><td>1059-930</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-146847</td><td>III</td><td>15-25 cm</td><td>Curculionidae</td><td>103.34 ± 0.35</td><td>255-35</td><td>Yes</td><td>0.141</td><td>S1</td></tr><tr><td>Poz-146848</td><td>III</td><td>15-25 cm</td><td>Pterostichus pumilio</td><td>335 ± 30</td><td>475-310</td><td>No</td><td>0.164</td><td>S2</td></tr><tr><td>Poz-745476</td><td>III</td><td>15-25 cm</td><td>Pool insect</td><td>360 ± 30</td><td>495-315</td><td>No</td><td>0.7</td><td>S2/S3</td></tr><tr><td>Poz-147649</td><td>III</td><td>15-25 cm</td><td>Acer sp.</td><td>2655 ± 30</td><td>2848-2736</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-148015</td><td>III</td><td>16-25 cm</td><td>Abies alba</td><td>2850 ± 30</td><td>3063-2873</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-147650</td><td>III</td><td>17-25 cm</td><td>Fagus sylvatica</td><td>1580 ± 30</td><td>1530-1394</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-159480</td><td>V-1</td><td>50-65 cm</td><td>Cf. Rhododendron</td><td>8590 ± 50</td><td>9681-9486</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-160040</td><td>V-1</td><td>50-65 cm</td><td>Betula sp.</td><td>8030 ± 50</td><td>9077-8650</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-148016</td><td>V-1</td><td>50-65 cm</td><td>Cf. Rhododendron</td><td>8580 ± 80</td><td>9884-9429</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-157258</td><td>V-2</td><td>65-80 cm</td><td>Harpalus sp.</td><td>130.27 ± 3.5</td><td>264-25</td><td>Yes</td><td>0.023</td><td>S3</td></tr><tr><td rowspan="8">BURP1</td><td>Poz-157247</td><td>III</td><td>5-50 cm</td><td>Pterostichus amoenus</td><td>104.88 ± 2.91</td><td>258-32</td><td>Yes</td><td>0.023</td><td>S1</td></tr><tr><td>Poz-153156</td><td>III</td><td>5-50 cm</td><td>Abies alba</td><td>3310 ± 30</td><td>3618-3453</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-159481</td><td>III</td><td>5-50 cm</td><td>Corylus sp.</td><td>6250 ± 40</td><td>7261-7015</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-153672</td><td>IV</td><td>45-90 cm</td><td>Fagus sylvatica</td><td>1990 ± 30</td><td>1995-1834</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-153672</td><td>IV</td><td>45-90 cm</td><td>Quercus sp.</td><td>6095 ± 35</td><td>7157-6802</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-153675</td><td>IV</td><td>45-90 cm</td><td>Acer sp.</td><td>9390 ± 50</td><td>10750-10440</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-160038</td><td>IV</td><td>45-90 cm</td><td>Abies alba</td><td>3160 ± 35</td><td>3545-3264</td><td>No</td><td>–</td><td>/</td></tr><tr><td>Poz-160039</td><td>IV</td><td>45-90 cm</td><td>Abies alba</td><td>3270 ± 30</td><td>3565-3405</td><td>No</td><td>–</td><td>/</td></tr></tbody></table>

increased in some areas of the mountain belt zone, probably related to local silvopastoral practices using fire (Saulnier et al., 2020). Evidence from entomological remains of the same layer also suggest similar conditions, as they present a mixed assemblage of taxa associated with forest cover, such as the ground beetles *Pterostichus pumilio* (Ponel et al., 1999) (MNI = 10; one at TSD stage S3 and nine at S2) and *Leistus nitidus* (MNI = 1; at S2), and of taxa that prefer open environments, *Harpalus* (MNI = 7; one at TSD stage S3 and six at S2). Independent evidence for past openings near BURP1 comes from ancient charcoal records and historical archives documenting substantial forest clearing in the upper part of the current Burat forest near BURP1 (Borde, 2024).

In BOIP2, layer IV contains no evidence of fire activity, creating a gap in the reconstruction of the site's forest development trajectory. Pedoanthracological data indicate a forested environment from at least the Iron Age, with the presence of *Abies alba* in layer III (2740-2493 cal BP). The fire disturbance recorded at that time is likely of anthropogenic origin, probably related to agro-silvo-pastoral practices (Py-Saragaglia et al., 2017). Phases of canopy opening are also detected through pedoanthracology, with the presence of *Fraxinus* (a post-pioneer taxon) dated to the Modern Period (441-154 cal BP), as well as *Sorbus* cf. *S. aucuparia* in layer II and Ericaceae in layer III. The underrepresentation of broadleaf species is likely due to their poor preservation. Entomological data are consistent with a sustained forest cover, without implying that they are contemporaneous with the charcoal recovered from the same pit, notably marked by the presence of *Pterostichus pumilio* (layer I: MNI = 10, all in S1; layer II: MNI = 3, one in S1, two in S3; layer IV: MNI = 8, two in S1, one in S2, five in S3; layer V: MNI = 1, in S2). Additional forest indicators from the Curculionidae family support this

signal, including *Hylastes* sp. (layer II: MNI = 7, all in S2), and *Strophosoma melanogrammum* (layer I: MNI = 4, all in S1; layer II: MNI = 2, all in S2). No open markers were found in this pit.

Additionally, in layers IV to II, remains of *Aphodius* (identified to genus, S3) were recovered. Members of this genus are coprophagous or saprophagous, but they require animal dung for their development (Ponel et al., 1992; Robinson, 1978). Their high dispersal capacity implies that their presence may reflect dung from either nearby or more distant sources. The likelihood that these remains were passively transported by wind is low, due to the protective effect of the forest canopy. While their presence could be related to wild ungulates in a forest environment, several lines of evidence support a connection to pastoral activities: (1) the remains were found less than 20 m from two undated archaeological structures likely associated with pastoral use (Py-Saragaglia et al., 2025); (2) pollen data from Lake d'Espingo, located less than 12 km away, indicate agro-pastoral practices during the Middle Ages (Py-Saragaglia et al., 2025); (3) historical sources report the introduction of livestock into this part of the forest in the 19th century (Py-Saragaglia et al., 2025). Taken together, these observations suggest that the *Aphodius* remains may reflect pastoral activity in the area, although this cannot be confirmed without more precise identification to genus or species level.

## 5. Conclusion

This study represents an exploratory attempt to assess the potential contribution of insect remains to palaeoenvironmental reconstructions in contexts that are generally considered unfavourable for their
preservation (forest soils subject to bioturbation). The primary objective was to evaluate how the insect proxy could complement information derived from charcoal analysis. Several limitations emerged, including generally poor preservation of insect sclerites, differential preservation biases, the absence of saproxylic species (key species in OGFs), and difficulties in radiocarbon dating due to low carbon content, likely resulting in rejuvenated ages. Despite these limitations, our results indicate that insect remains may provide complementary insights into past forest dynamics, particularly when combined with charcoal data. Their contribution, however, lies primarily in the ecological dimension (e.g., taxa indicative of canopy openings or pastoral activity) rather than in establishing a robust chronological framework. To address part of this limitation, we developed a Time Since Death (TSD) index, which provides a relative measure of degradation stages and, by extension, the likely relative age of the remains, on the assumption that S3 specimens are older than S1 within the same depositional context. This approach makes it possible to exclude from the study the most recent insect remains (S0 and S1 stages), potentially intrusive, thereby helping to reduce the biases introduced by vertical bioturbation. We fully acknowledge that the contemporaneity between the insect remains and charcoal fragments cannot be firmly established, especially since individual stratigraphic layers may encompass charcoal deposits accumulated over several millennia.

Nevertheless, some promising patterns emerged: both proxies indicate canopy openings in certain layers; insect assemblages, in addition, highlight possible agro-sylvo-pastoral activities and offer ecological perspectives compatible with the long-term continuity of forest cover inferred from charcoal. These ecological signals should be understood as complementary rather than synchronous. Looking ahead, the development of advanced dating techniques, such as AMS (accelerator mass spectrometry), Gas-AMS (gas-ion source AMS), and micro-scale graphite targets, holds promise for improving the chronological reliability of insect remains. Consolidating and clarifying this combined approach will require further testing in other mountain contexts (e.g., high-altitude meadows) and across different climatic settings.

The consolidation and clarification of this combined approach and the results that can be drawn from it need to be systematised in other mountain contexts (e.g. high altitude meadows) or in other climates.

## CRediT authorship contribution statement

**Sarah Parrilla:** Writing – original draft. **Mélanie Saulnier:** Writing – original draft. **Laurent Larrieu:** Writing – review & editing. **Lionel Valladares:** Writing – review & editing. **Valentina Pescini:** Writing – review & editing. **Pierre Moret:** Writing – original draft. **Vanessa Py-Saragaglia:** Writing – original draft.

## Acknowledgements

This study was financially supported by a Vinci grant (2020-2023) and the JCJC ANR project "BENDYS" (2019-2024, ANR-19-CE03-0010), coordinated by Vanessa Py-Saragaglia. It also received financial support from TRACES UMR 5608 laboratory (Toulouse). Pescini acknowledges funding from the Ramón y Cajal Programme no. RYC2021-034621-I. This project was made possible thanks to the support of the LASA laboratory in Genoa, directed by Anna Stagno. We would also like to thank Sandrine Buscaino for her help with sample preparation (sorting), Théo Maisonhaute for his help in the field (sampling) and with sample analysis (charcoal), Magali Philippe and Sylvain Burri for their help in the field, Sylvie Ladet for map production using BENDYS data. We also want to thank Tomasz Goslar, Poznan laboratory and Christine Oberlin, for their precious help for interpreting the carbon results, and their recommendations.

## Data availability

Data used are in the paper

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