bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of quadrat size and data measurement on the detection of boundaries
Authors: Fortin Marie‐Josée
Published: May 2006

Abstract. With sampled field data, the accuracy of delineation of ecotones is directly related to the resolution of the data (i.e. spatial and measurement type) and to the edge detection algorithm used. In the present study the reliability is investigated of an edge detection algorithm (lattice‐wombling) to delimit vegetation boundaries when different spatial resolutions (quadrat sizes) are used. To quantify whether the edge detection algorithm is robust, it was applied to data from woody species in a second‐growth woodland measured at different spatial resolutions with different data types. Boundaries were found at similar locations using any reasonable quadrat size (ca. 200 m2) but there were some slight differences when using different vegetation measures (density versus presence/absence data).
Changes in the canopy structure of the Mediterranean shrub Lavandula stoechas after disturbance
Authors: Díaz Barradas M.C. , Mateos M.A. , Orellana R. , Zunzunegui M. , García Novo F.
Published: May 2006

Abstract. This study attempts to show the dynamics of the canopy structure of the Mediterranean pioneer shrub Lavandula stoechas after man‐made perturbation (i.e. grazing). The development of the vertical structure of the shrub was studied by harvesting the canopy of plants of 2–6 yr old in horizontal layers. The supportive biomass of the canopy was concentrated near the base at all ages. Leaf biomass was evenly distributed all over the vertical profile in 2‐ and 3‐yr old plants. In 4‐yr old plants it presented a maximum near the top of the canopy. For 5‐yr old plants a structural transition started with leaf profiles showing a bimodal distribution. Leaf biomass predominated near the base in 6‐yr old plants, suggesting that the transition was completed.

Three canopy stages in the growth processes of the plant were recognized after the first year of growth: in the first one (from 2 to 3 yr old) both leaf and supportive biomass increased; in the second one (from 3 to 4 yr) leaf biomass remained stable and there was an increase in supportive biomass until the plants reached a ‘mature stage’, in 4‐yr old plants; finally, in 5‐ and 6‐yr old plants there was a decrease both in leaf and supportive biomass and plant structure showed evidence of senescence. Early transitions from seedling to 1‐yr old plant and from this to 2‐ to 3‐yr old plants were less obvious.

The leaf/supportive biomass ratio always decreased with plant age, from 1.88 in seedlings to 0.01 in 6‐yr old plants. Biomass density followed the pattern of supportive biomass, with an increase from 1.7 g/dm3 (2‐yr old plants) to 2.4 g/dm3 (4‐yr old plants). Thereafter, biomass density decreased to 0.6 g/dm3 (6‐yr old plants).
Plant communities and landscape diversity along a Canadian Arctic river
Authors: Gould William A. , Walker Marilyn D.
Published: May 2006

Abstract. We analysed the structure and diversity of the vegetation along an Arctic river to determine the relationship between species richness and plant community structure. We examined whether variation in species richness along the corridor is structured as (1) an increase in the number of communities due to increasing landscape heterogeneity, (2) an increase in the floristic distinctiveness (β‐diversity) of communities, or (3) an increase in within‐community richness (α‐diversity) as species‐poor communities are replaced by species‐rich communities.

We described 24 community types and analysed the relationship between site vascular species richness (γ‐diversity) and β‐diversity, α‐diversity, site environmental heterogeneity, and the number of distinct plant communities. We also measured diversity patterns of vascular, bryophyte, and lichen species within communities and examined their relationship to community‐level estimates of environmental factors.

We found that an increase in site species richness correlated with an increase in the number of communities (r2= 0.323, P= 0.0173) and β‐diversity (r2= 0.388, P= 0.0075), rather than an increase in the α‐diversity of individual communities. Moisture and pH controlled most of the differences in composition between communities. Measures of species richness and correlations with moisture and pH within communities differed among vascular, bryophyte, and lichen species. Bryophyte richness was positively correlated with moisture (r2= 0.862, P= 0.0010) and lichen richness was negatively correlated with moisture (r2= 0.809, P= 0.0031). Vascular plants had a peak in richness at pH 6.5 (r2= 0.214, P < 0.0001).

We conclude that site variation in vascular richness in this region is controlled by landscape heterogeneity, and structured as variation in the number and distinctiveness of recognizable plant communities.
Effects of grazing by re‐introduced Equus hemionus on the vegetation in a Negev desert erosion cirque
Authors: Ward David , Saltz David , Rowen Mary , Schmidt Iris
Published: May 2006

Abstract. Asiatic wild asses, Equus hemionus, were driven to extinction in Israel in the early 20th century. In 1983, a herd of these animals was re‐introduced to the wild in Makhtesh Ramon, a large erosion cirque in the central Negev desert, Israel. The population has grown steadily ever since and now numbers some 100 animals. In order to determine whether the wild asses are having a significant impact on the vegetation, we have monitored the plant communities in Makhtesh Ramon since 1992, using McAuliffe's log‐series survey method. Our study involves 11 pairs of plots along the length of the altitudinal gradient in Makhtesh Ramon. The altitudinal gradient results in a rainfall gradient from an average of 95 mm rain per year to an average of about 40 mm per year. Each pair of plots consists of: (1) an unfenced plot, and (2) a fenced plot that excludes wild asses but not the other large mammalian herbivore, the dorcas gazelle Gazella dorcas. The wild asses have not had a significant impact on vegetation cover, species richness, diversity or dominance. Three plant species showed significant increases in percentage cover in fenced plots, while one species showed a significant increase in percentage cover in unfenced plots. Furthermore, eight plant species invaded fenced plots, three species invaded unfenced plots and one species disappeared from unfenced plots during the study. Using Detrended Correspondence Analysis, we found that the major differences among plots are due to position along the altitudinal gradient. The Detrended Correspondence Analyses indicated that the wild asses have had no significant effect on vegetation community structure.
Tornado damage and initial recovery in three adjacent, lowland temperate forests in Missouri
Authors: Peterson Chris J. , Rebertus Alan J.
Published: May 2006

Abstract. We surveyed tornado damage 14 months after disturbance in three adjacent forest sites in southeastern Missouri, USA: upland, an occasionally‐flooded lowland and a frequently flooded swamp. We analysed three 0.09‐ha plots in the swamp, and three 0.04‐ha plots in the other sites and recorded the herbaceous‐layer in five 1‐m2 quadrats per plot.

Overall, 30 % of the individuals and 64 % of the basal area of these sites was blown down. However, mortality was less than structural damage: 20 % of the trees were dead 14 months post‐disturbance, an intermediate level of mortality relative to other wind disturbances. Damage varied widely among species, sites and tree sizes, but large trees of all species were most likely to be damaged and least likely to resprout.

While damage was greatest in the wettest site, we attribute the increase to larger tree sizes and lower density there, rather than to inherent rooting instability. This study suggests that different forest composition and structure may be sufficient to cause differential damage, without topographic effects. Herbaceous‐layer response was more rapid than in a previously reported tornado windthrow in Pennsylvania, and was dominated by fast‐growing, shade‐intolerant forbs.
Comparison of root distributions of species in North American grasslands using GIS
Authors: Sun Guowei , Coffin Debra P. , Lauenroth William K.
Published: May 2006

Abstract. We quantified the spatial distribution of roots of individual plants using detailed drawings from the literature of species of grasses, forbs, and shrubs in the Central Great Plains grasslands of North America. We scanned each two‐dimensional drawing electronically and used ARC/INFO, a Geographic Information System, to calculate root length (cm) and density (cm root length/cm soil) with depth in the soil profile. We then selected one of three mathematical models that best fit the data, and classified each species as either shallow‐, medium‐ or deep‐rooted. 66 root drawings from 55 species were evaluated. Most plants were shallow‐rooted with largest root densities occurring at depths < 20 cm; most maximum rooting depths were > 1m. Grasses had the shallowest maximum depth and shrubs the deepest. Deep‐rooted forbs had the smallest root densities by depth. Most plants had two sections to their distribution of root density: an initial increase from the soil surface followed by a decrease in density with increasing depth. Our results suggest that the abundance and importance of different species and growth forms in North American grasslands is related to similarities and differences in the spatial distributions of their root systems. Our approach provides quantitative information on root distributions to be used for comparisons among species, and in simulation modeling analyses that could not be done with conventional methods that are qualitative in nature.
Population strategies in severe environments: alpine plants in the northwestern Caucasus
Authors: Onipchenko Vladimir G. , Semenova Galina V. , van der Maarel Eddy
Published: May 2006

Abstract. This study attempts to show a differentiation into strategy types among plant species of four alpine communities in the northwestern Caucasus, Russia. Four groups of population characteristics (traits) were examined: above‐ground biomass, seed size, seed yield and occurrence of a persistent seed bank. In addition, values for relative growth rate and a morphology index were estimated. Agglomerative Cluster Analysis and Principal Component Analysis were applied to a data set with 42 species from these communities and six species characteristics. In the Geranium gymnocaulon meadow, the most productive community, large gaps occur created by wild boars and bears. Here, the response of 13 species to disturbance was also analysed.

Strategy types were approached both according to Grime: ‘competitive’, ‘ruderal’, ‘stress‐tolerating’ and according to Ramensky, Rabotnov and Romanovsky: ‘violent’ ≈ dominant (V), ‘explerent’ ≈ explorative (E) and ‘patient’ ≈ endurant (P). Differentiation into strategy types was more obvious in productive alpine grasslands than in lichen heaths and snowbed communities. The grassland dominants Festuca varia, Geranium gymnocaulon and Hedysarum caucasicum showed a more or less ‘violent’ strategy. Species approaching an Estrategy, e.g. Matricaria caucasica, Sibbaldia procumbens and Gnaphalium supinum, were also found in the grasslands but prevailed in the snowbed communities. Species with a ‘patient’ strategy prevailed in the lichen heaths.

We conclude that plant strategy types are well‐differentiated, this is also seen in plant communities occurring under severe high‐mountain conditions. We also suggest that the approaches by Grime and Ramensky/Rabotnov/Romanovsky are not so similar as has been assumed earlier and that the R/R/R types are better differentiated and ecologically better interpretable.

We emphasize the gradient character of strategy ‘types’ and would characterize plant species by the degree of adaptation to conditions: (1) from small seed size and large persistent seed bank to large seed size and absence of a seed bank; (2) from high to low biomass and seed production, with relative growth rate as a less important partially correlated trait.
Dynamics of Salix caprea L. populations during forest regeneration after strong herbivore pressure
Authors: Faliński Janusz Bogdan
Published: May 2006

Abstract. Broadleaved forest communities degenerated through strong pressure from large herbivores. Relief of this pressure led to regeneration, in particular of Salix caprea and other light‐seeded pioneer trees: Populus tremula, Betula pendula and B. pubescens. This regeneration proceeded following conservation protection of degenerate stands in a nature reserve and later in Biaowiéza National Park. The emergence and development of the Salix caprea population proceeded following the expansion of Picea abies, which coincided with the period of enhanced animal pressure on the broadleaved forest. Salix caprea filled all the gaps in the tree stand after the destruction of trees and undergrowth by herbivores (in the years 1892–1915). The species also appeared abundantly in old, at the time unforested, clearings and felled areas.

Here, S. caprea developed large populations with certain trees in good condition, with a growth form typical of forest trees and attaining considerable heights. The majority of trees were 50 ‐ 60 yr old at the time of death, although some individuals reached 74 yr of age. The process of extinction of the Salix population — observed over 19 yr on permanent plots with marked trees — proceeded very quickly, especially in the first decade of observation. It led to the almost complete disappearance of S. caprea from the forest communities of Biaowiéza National Park. The death of individual trees is preceded by impairment of their health and reduced annual increments in the last 4–9 years of their life.

The development of populations of permanent constituents of the forest, notably Carpinus betulus, Tilia cordata, Acer platanoides and Ulmus glabra, under the canopy of light‐seeded trees, and the absence of a new generation of pioneer trees points to the end of the process of regeneration in the forest communities of BiaHwiéza National Park.
Relationships among the seed rain, seed bank and vegetation of a Hawaiian forest
Authors: Drake Donald R.
Published: May 2006

Abstract. Hawaiian ecosystems are prone to invasion by alien plant species. I compared the seed rain, seed bank, and vegetation of a native Hawaiian forest to examine the potential role that seed ecology plays in allowing alien species to invade native forest. Absolute cover of seed plants in the forest was 126 %, annual seed rain was 5 713 seeds m‐2 yr‐1, and the mean density of seedlings emerging from the seed bank averaged across four seasons was 1 020/m2. The endemic tree Metrosideros polymorpha was the most abundant species in the vegetation, seed rain and winter seed bank. Overall, native seed plants comprised 95 % of the relative cover in the vegetation and 99 % of the seeds in the seed rain, but alien species comprised 67 % of the seeds in the seed bank. Alien species tended to form persistent seed banks while native species formed transient or pseudo‐persistent seed banks. Dominance of the seed bank by alien species with persistent seed banks suggests that aliens are favorably placed to increase in abundance in the vegetation if the forest is disturbed.
Tree and grass rooting patterns in an African humid savanna
Authors: Mordelet Patrick , Menaut Jean‐Claude , Mariotti André
Published: May 2006

Abstract. Spatial and temporal soil partitioning between roots of the two savanna plant components, i.e. trees and grasses, were investigated in a West African humid savanna. Vertical root phytomass distribution was described for grass roots, large (> 2 mm) and fine (< 2 mm) tree roots, in open sites and beneath tree canopies. These profiles were established monthly over one year of vegetation growth. Natural 13C abundance measurement was used to determine the woody/herbaceous phytomass ratio in root samples. Tree and grass root distributions widely overlapped and both were mostly located in the top 20 cm of the soil. Grass root phytomass decreased with depth whereas woody root phytomass peaked at about 10 cm depth. No time partitioning was detected. These structural results do not support the hypothesis of soil resource partitioning between trees and grasses and are thus consistent with functional results previously reported.
Influence of sugar beet breeding on populations of Beta vulgaris ssp. maritima in Italy
Authors: Bartsch Detlef , Schmidt Marion
Published: May 2006

Abstract. It is highly probable that transgenic cultivars of sugar beet may influence wild beets in the seed‐production‐area of northern Italy. For this reason a survey of the local wild beet populations and their habitat characteristics was conducted in 1994/1995, i.e. before transgenic beets and their off spring could have become established. Wild beets (Beta vulgaris ssp. maritima) were found at 21 locations between Trieste and Cesenatico, as part of the natural littoral vegetation classified as Atriplicetum tatarici (Cakiletea maritimae) and Crithmetum (Crithmo‐Staticetea). The analysis of phenotypic attributes leads to a division into three different sub‐populations. Greenhouse studies on the morphology and life‐cycle attributes demonstrated actual gene flow between conventional seed beet and the examined wild beet population.
The effects of treefall gaps on understory vegetation in New York State
Authors: Goldblum David
Published: May 2006

Abstract. Treefalls are a common form of disturbance in northeastern United States forests. The resultant gaps contribute to a high degree of environmental heterogeneity in the understory of these forests. Plant density, plant cover, and species richness in understory plant communities were monitored for three years during the growing season, May ‐ September. Differences between treefall gap and closed canopy vegetation were less pronounced early in the growing season for plant density and leaf cover. Species richness was significantly greater within treefall gaps during the entire growing season. Eight species were found in greater abundance within treefall gaps (i.e., gap‐phase species), while one species was found more commonly under closed canopy. Ordination results suggest that time since gap creation and treefall gap size marginally affect the species composition of vegetation found within treefall gaps.
On the sensitivity of ordination and classification methods to variation in the input order of data
Authors: Podani János
Published: May 2006

Abstract. This paper is a reflection on a recent study on input order sensitivity of data analysis methods commonly used in vegetation science. It is pointed out that variability of results is due to some arbitrary element in the method, either in its algorithm or in its computer program. Many methods produce unique results theoretically; this implies that the source of uncertainty can only be the algorithm or its computer implementation. It is stressed that the prerequisite of meaningful comparisons is that these causes have been identified previously. Whenever the method is known to be input‐order sensitive, such as the unweighted pair group clustering technique, the use of algorithms and programs which disregard this sensitiveness should be avoided.
Recruitment of Quercus agrifolia in central California: the importance of shrub‐dominated patches
Authors: Callaway Ragan M. , Davis Frank W.
Published: May 2006

Abstract. Many perennial plants strongly enhance the survival of seedlings of other species. We studied patterns of long‐term recruitment of Quercus agrifolia (Coastal live oak) associated with shrub‐dominated communities by counting Q. agrifolia recruits on a time sequence of historical aerial photographs and comparing recruitment among mapped patches of coastal sage scrub, chaparral, and grassland in an 1120‐ha landscape. Because we could not identify new recruits in existing woodlands with aerial photographs, we studied the recruitment of Q. agrifolia in this vegetation type indirectly by comparing population size structures and the spatial relationships between shrubs and recruits among woodlands that varied in understory community type. At the landscape scale, recruitment was higher in coastal sage scrub vegetation than predicted by the extent of its coverage, commensurate with the spatial coverage of chaparral, and very low in grassland. Recruitment within woodland communities also varied considerably. In woodland communities on sheltered, north‐oriented topography with understories dominated by shrubs, there were large numbers of small Q. agrifolia, and recruits were not significantly spatially associated with shrubs within plots. In woodlands with herbaceous understories there were few individuals in the small size classes, and recruits were strongly spatially associated with shrubs within plots. Woodlands with shrub‐dominated understories have population structures that appear to be stable, but woodlands with herbaceous understories exhibit size structures associated with declining populations. Quercus recruitment into shrub‐dominated patches corresponds with previous documentation of facilitative relationships between shrubs and oak seedlings, and suggests the occurrence of an unusual form of patch dynamics in these landscapes.
BOOK REVIEWS
Authors: Walck Jeffrey L.
Published: May 2006

Book reviewed in this article:

de Kroon, Hans & van Groenendael, Jan (eds.) 1997. The ecology and evolution of clonal plants. xii + 453 pp. Backhuys Publishers, Leiden. ISBN 90‐73348‐73‐0. Price (paper): NLG 120.00/USD 67.00.

Günter, Gundula. 1997. Populationsbiologie selterner Segetalarten. Scripta Geobotanica 22, 220 pp. Verlag Erich Goltze, Göttingen. ISBN 3‐88452‐522‐0. Price: DEM 55.‐.

Vernet, Jean‐Louis. 1997. L'homme et la forět méditerranéenne de la Préhistoire à nos jours. 248 pp. Editions Errance. ISBN 2 87772 137 X. Price FRF 240.‐.

Grabherr, Georg. 1997. Farbatlas Ökosysteme der Erde. 364 pp., 430 colour photographs, 11 colour distribution maps. Verlag Eugen Ulmer, Stuttgart. ISBN 3‐8001‐3489‐6. Price: DEM 44.‐.

Kutschera, Ulrich. 1998. Grundpraktikum zur Pflanzen‐physiologie. UTB 2026. 160 pp. Quelle & Meyer Verlag, Wiesbaden. ISBN 3‐494‐02245‐3. Price: DEM 36.80.

Randlane, Tiina & Saag, Andres. 1998. Lichens in Estonia and in the rest of the world. Papers dedicated to Hans Trass on his 70th birthday. Folia Cryptogamica Estonica, Fasc. 32, 160 pp. Estonian Naturalists' Society. ISSN 1406‐2070; ISBN 9985‐50‐211‐6. Price not indicated. To be obtained at the address of the Society, 2 Struve Street, EE 2400 Tartu, Estonia.
Structural dynamics of a natural mixed deciduous forest in western Thailand
Authors: Marod Dokrak , Kutintara Utis , Yarwudhi Chanchai , Tanaka Hiroshi , Nakashisuka Tohru
Published: May 2006

Abstract. Structural dynamics of a natural tropical seasonal – mixed deciduous – forest were studied over a 4‐yr period at Mae Klong Watershed Research Station, Kanchanaburi Province, western Thailand, with particular reference to the role of forest fires and undergrowth bamboos. All trees > 5 cm DBH in a permanent plot of 200 m × 200 m were censused every two years from 1992 to 1996. The forest was characterized by a low stem density and basal area and relatively high species diversity. Both the bamboo undergrowth and frequent forest fires could be dominant factors that prevent continuous regeneration. Recruitment, mortality, gain (growth of survival tree plus ingrowth) and loss in basal area (by tree death) during the four years were 6.70%/yr, 2.91%/yr, 1.22%/yr and 1.34%/yr, respectively. Mortality was size dependent; middle size trees (30–50 cm) had the lowest mortality, while the smallest (5–10 cm) had the highest mortality. Tree recruitment was observed particularly in the first two years, mostly in the area where die‐back of undergrowth bamboo occurred. The bias of the spatial distribution of recruitment to the area of bamboo die‐back was significant and stronger than that to the forest canopy gaps. Successful regeneration of trees which survive competition with other herbs and trees after dieback of bamboo could occur when repeated forest fires did not occur in subsequent years. It is suggested that both the fire disturbance regime and bamboo life‐cycle greatly influence the structure and dynamics of this seasonal tropical forest.
Dynamics of forests with Araucariaceae in the western Pacific
Authors: Enright N.J. , Ogden J. , Rigg L.S.
Published: May 2006

Abstract. Several species of Araucaria and Agathis (Araucariaceae) occur as canopy emergents in rain forests of the western pacific region, often representing major components of total stand biomass. New data from permanent forest plots (and other published work) for three species (Araucaria hunsteinii from New Guinea, A. laubenfelsii from New Caledonia, and Agathis australis from New Zealand) are used to test the validity of the temporal stand replacement model proposed by Ogden (1985) and Ogden & Stewart (1995) to explain the structural and compositional properties of New Zealand rain forests containing the conifer Agathis australis. Here we propose the model as a general one which explains the stand dynamics of rain forests with Araucariaceae across a range of sites and species in the western Pacific.

Forest stands representing putative stages in the model were examined for changes through time in species recruitment, growth and survivorship, and stand richness, density and basal area. Support for the model was found on the basis of: 1. Evidence for a phase of massive conifer recruitment following landscape‐scale disturbances (e.g. by fire at the Huapai site, New Zealand for Agathis australis); 2. Increasing species richness of angiosperm trees in the pole stage of forest stand development (i.e. as the initial cohort of conifers reach tree size; >10 cm DBH); 3. A high turnover rate for angiosperms (<100 yr), and low turnover for conifers (≥ 100 yr) in the pole stage, but similar turnover rates for both components (50–100 yr) as forests enter the mature to senescent phase for the initial conifer cohort; 4. Very low rates of recruitment for conifers within mature stands, and projected forest compositions which show increasing dominance by angiosperm tree species; 5. A low probability of conifer recruitment in large canopy gaps created by conifer tree falls during the initial cohort senescent phase, which could produce a second generation low density stand in the absence of landscape scale disturbance; 6. Evidence that each of the three species examined required open canopy conditions (canopy openness > 10 %) for successful recruitment.

The evidence presented here supports the temporal stand replacement model, but more long‐term supporting data are needed, especially for the phase immediately following landscape level disturbance.
Density‐dependence and co‐existence of conifer and broad‐leaved trees in a Japanese northern mixed forest
Authors: Hiura Tsutom , Fujiwara Koichiro
Published: May 2006

Abstract. The growth and survival of coniferous trees (particularly Abies sachalinensis) and broad‐leaved trees (particularly Quercus crispula) were followed over a 15‐yr period in a 15.5‐ha area in a northern mixed forest in Japan, and the coexistence of the two groups was simulated by a density‐dependent projection matrix model. The density‐dependent model assumes that the density effect of mother trees due to one‐sided competition for light on smaller‐sized tree regulates the demographic functions. The mother tree densities of conifers and broad‐leaved trees have stronger negative effects on the recruitment and survival of seedlings of their own group than of the other group. These results support the idea of reciprocal replacement for conifer and broad‐leaved trees. Simulations using the density‐dependent model showed that the two groups will co‐exist within a particular range of recruitment rates. However, the density of both groups did not affect the growth rate of any tree, and equilibrium DBH‐distributions from density‐dependent matrices were quite different from present distributions both for conifers and broad‐leaved trees. On the other hand, equilibrium DBH‐distributions of conifer and broad‐leaved trees from density‐independent matrices were quite distinct from each other, reflecting different survivorship curves of the two dominants. These results suggest that density‐dependent processes are not so important for shaping population structures in this northern mixed forest.
Cryptogams on decaying wood in old‐growth forests of southern coastal British Columbia
Authors: Qian Hong , Klinka Karel , Song Xianghou
Published: May 2006

Abstract. We studied the floristic composition of lignicolous cryptogams (i.e. bryophytes and lichens inhabiting decaying wood) in the old‐growth coniferous forests of southern coastal British Columbia. The composition of the cryptogams was related to forest communities (described by vegetation units using forest floor cryptogams and vascular plants) and regional climates (described by biogeoclimatic zones). The study is based on a total of 247 sample plots, each of 0.04 ha in size. The plots were located in three different biogeoclimatic zones and were classified into 12 alliances and four orders in a previous study. We used indicator species analysis to determine cryptogam indicator species for each vegetation unit and biogeoclimatic zone, and used similarity analysis and multi‐variate analyses (discriminant analysis and detrended correspondence analysis) to detect differences in the floristic composition of the cryptogams among sample plots, vegetation units, and biogeoclimatic zones. Most of the cryptogams in this study had a narrow distribution, and only < 5% of the species were present across all the vegetation units and biogeoclimatic zones. The overall means of Jaccard coefficients between two sample plots from the same vegetation unit (alliance or order) or biogeoclimatic zone were significantly higher (P < 0.05) than those from different vegetation units or biogeoclimatic zones. The difference in the mean Jaccard coefficients within‐ and between‐units was highest for zones. The results of detrended correspondence analysis and discriminant analysis suggest that the composition of lignicolous cryptogams changes with the change in the floristic composition of forest floor vegetation. When the first axes of detrended correspondence analysis were compared, the Pearson's correlation coefficients between the first axes of lignicolous cryptogams and forest floor vascular plants and between the first axes of lignicolous cryptogams and forest floor cryptogams were 0.78 and 0.87, respectively. The degree of correspondence in the composition of lignicolous cryptogams and forest floor vegetation increased from alliance to order to biogeoclimatic zone. This trend suggests that the floristic composition of lignicolous cryptogams is influenced at the community level mainly by edaphic conditions and at the regional level by climatic conditions.
Wetland development in early stages of volcanic succession
Authors: Tsuyuzaki Shiro
Published: May 2006

Abstract. Wetland vegetation developed in the crater of Mount Usu, northern Japan, soon after the 1977–1978 eruptions which destroyed the vegetation. The cover of each species was measured in 1994 in 118 50 cm × 50 cm plots situated in transects and related to environmental factors (elevation, water depth, soil texture, soil compaction, soil organic matter, and soil pH) to clarify vegetation development. Five vegetation types were recognized dominated by Eleocharis kamtschatica, Equisetum arvense, Lythrum salicaria, Juncus fauriensis and Phragmites australis respectively. Sedge/grass marsh and reed swamp dominated deep‐water sites; willow swamp and wet meadow vegetation characterized shallow‐water sites, indicating that vegetation zonation developed soon after the eruption. Since those wetland plants were derived neither from seed banks nor from vegetative propagules, they had to immigrate from outside the summit areas. However, except for willows, most species lack the ability for long‐distance dispersal. Late successional species, such as P. australis established in the early stages of the primary succession. The water depth varied by 27.5 cm among the plots. Coarse soil particles accumulated, and pH (5.22–6.55) was low on the elevated sites. Organic matter ranged from 2.8 % to 19.1 %, and was high on the elevated sites. Water depth was responsible for the establishment of large‐scale vegetation patterns, while edaphic factors, i.e. soil compaction, pH, and organic matter, were determinants of small‐scale vegetation patterns. Among the edaphic factors, soil compaction appeared to have a strong influence on vegetation development.
Effects of germination inhibition on the dynamics of Quercus ilex stands
Authors: Li Junqing , Romane Francois J.
Published: May 2006

Abstract. Germination of Quercus ilex L. in coppice stands of this species in the western Mediterranean Basin was examined and a germination inhibitory process is proposed to explain some germination traits. Germination rate and seedling biomass of Q. ilex were greatly modified by watering acorns with various concentrations of aqueous soil extracts from a Q. ilex coppice stand but also when the acorns were sown in soil from Q. ilex coppice stands. In the aqueous extract experiment, Q. ilex germination and seedling weight both decreased as the aqueous extract concentration increased. In the soil type experiment, Q. ilex soil decreased the Q. ilex germination rate. Comparative studies with Q. pubescens germination (this species, replaced by Q. ilex around 5 000 B.P., is assumed to form the climax vegetation of the region) revealed that Q. pubescens was less sensitive to the aqueous extracts and soils of Q. ilex coppice stands.

Inhibition of Q. ilex seed germination could be a major reason for the poor seed regeneration and suggested a possible comeback of Q. pubescens.
Simulated responses to hypothetical fundamental niches
Authors: Malanson George P.
Published: May 2006

Abstract. Two graphical models of plant competition, the ‘ghost of competition past’ and the ‘hierarchical’ model are compared using a greatly simplified individual‐based forest dynamics simulation. Assumed fundamental niche shapes are used to determine the basic growth responses of the species, but competition alters the realized niche. Differences in the two models, amount of niche overlap, disturbance, and removal and invasion of species are examined in simulation experiments. Without disturbance, the realized niche responses reveal abrupt boundaries between species in all cases, and thus the responses are generally platykurtic to rectangular with little overlap. In some cases overlap through the extension of abundance of weaker competitors into the area of greater resources — dominated by better competitors but still within their fundamental niche — creates skewed distributions, as have been observed and simulated in the past. When species are removed or invade, the abrupt boundaries and the lack of difference in final response shape indicate that past removals may be difficult to detect. This difficulty may be important because former species may be influencing the responses that are observed in common non‐equilibrium distributions. Even when assumptions favor the illustration of a competitive hierarchy, actual distributions and dynamics do not differentiate between it and a model of the ghost of competition past.
Canopy and age structures of some old sub‐boreal Picea stands in British Columbia
Authors: Kneeshaw D.D. , Burton P.J.
Published: May 2006

Abstract. 14 old, unlogged, Picea‐dominated stands in the moist cool Sub‐Boreal Spruce biogeoclimatic subzone of central British Columbia, Canada, were sampled to describe canopy heterogeneity, regeneration patterns and tree population age structures. These stands are composed of Picea engelmannii × glauca hybrids, Abies lasiocarpa and lesser amounts of Pinus contorta and Populus tremuloides, and had survived 124–343 yr since the last stand‐destroying wildfire. Canopy cover was patchy and highly variable (ranging from 30.5 % to 86.4 %) but was not significantly related to stand age. Vertical canopy structure was less variable, reflecting the shade‐tolerance and live crown ratios (length of live canopy expressed relative to tree height) of component species: 18.8 % for Populus, 20.2 % for Pinus, 46.7 % for Picea and 51.4 % for Abies. Individual stands varied considerably in their population structures and in their stand development trajectories, yet some patterns are evident. Survivors of the initial post‐disturbance cohort of trees took 51 to 118 yr (mean = 80, s.d. = 20) to establish. Some stands had all tree species present during stand initiation, while other stands indicated early successional roles for Populus and Pinus, or a late successional role for Abies. Abies recruitment, while often slow in the beginning, occurs uniformly throughout the history of most stands, reflecting the high shade‐tolerance of this species. Picea is often recruited in high densities early in stand development, and then (after long periods of exclusion) may be displaced by Abies in some stands but maintains itself in others. Minor, single‐tree disturbances (due to bark beetles, root rot, and windthrow) were important in accelerating the reinitiation of Picea in the understory. Results thus suggest that stands from this region can be self‐perpetuating in the absence of fire. Yet, post‐fire tree populations still clearly dominate these spruce‐fir forests, for only the oldest stand had greater basal area in the replacement cohort than in the initial cohort.
Impacts of secondary seed dispersal and herbivory on seedling survival in Aesculus turbinata
Authors: Hoshizaki Kazuhiko , Suzuki Wajirou , Sasaki Satohiko
Published: May 2006

Abstract. Aesculus turbinata is a tree species with large seeds (6.2 g mean dry weight). We studied the demography of its seeds and seedlings in a temperate deciduous forest in northern Japan to elucidate the ecological significance of large seeds with special reference to herbivory and secondary dispersal. Both seed and seedling stages suffered greatly from herbivores. Seedling herbivory was important judged from experiments with shoot clipping and hypogeal cotyledon removal. However, some seedlings survived through re‐sprouting after herbivory. Survival rate and percentage resprouting seedlings were lower than those with remaining cotyledons, though seedling size was not affected. This suggests that stored resources in hypogeal cotyledons are working as a kind of ‘risk hedge’ against severe aboveground shoot clipping experienced by A. turbinata. The spatial distribution of seedlings was expanded via seed scatter‐hoarding by rodents. Seedling survival rate was higher within canopy gaps than under closed canopy, indicating that canopy gaps are safe sites for establishment, and was negatively correlated with seedling density. Therefore, secondary seed dispersal in this species seems to be effective in ‘finding’ safe sites and in ‘escaping’ density‐dependent mortality. The large seeds and seedlings of A. turbinata are attractive to herbivores, but the high resistance of seedlings to herbivory due to large reserves and the effective secondary dispersal appear to mitigate these disadvantages.
To fix or not to fix the species limits, that is the ecological question: Response to Jari Oksanen
Authors: Austin M.P. , Nicholls A.O.
Published: May 2006

Abstract. We respond to Oksanen's recent comments in “Why the beta‐function cannot be used to estimate skewness of species responses”. We agree with Oksanen's criticisms concerning correlated parameters when fitting beta‐functions. We argue that response functions can be reasonably estimated using beta‐functions only for those species whose range limits obviously fall within the observed length of an environmental gradient and our original description included explicit recognition of this need. The simulated data used by Oksanen contains only one species that would meet our criteria for defining the limits and the shape of this species is recovered by fitting a beta‐function.

Beta‐functions are shown to recover reasonable approximations of the true shapes when fitted to simulated data, generated without error, and representing species with either skewed or symmetrical response shapes if using realistic estimates of the species limits. When arbitrary limits are imposed then distorted shapes result. Using similar data from 500 simulated data sets generated under the assumption of a Poisson error structure, beta‐functions gave conservative estimates of the degree of skewness for those data sets representing skewed species and no evidence of skewness for those data sets representing symmetrical species.

We conclude that despite Oksanen's concerns the conclusions drawn by the current authors and colleagues with respect to the degree of skewness shown by species response functions along a common gradient are robust to the fitting procedures used. While we agree that the fitting of beta‐functions is not the best approach to modelling skewed responses we argue that it will not mislead the user as to the presence or extent of skewness if used with reasonable and data driven estimates of the species limits.
Temporal and spatial changes in a mountainous area of central Italy
Authors: Peroni Patrizia , Ferri Fernando , Avena Gian Carlo
Published: May 2006

Abstract. In this paper we present an application of aerial remote sensing to the analysis of spatial information in a mountainous area of central Italy by applying texture measures and landscape indices. Land cover data acquired in different time periods are used to calculate measures of landscape pattern and structure at pixel level (tone and texture variables) and patch‐level (landscape indices). Images of the patches from the 1950s, 1980s and 1990s have been derived from the tone‐texture classification of scanned black‐and‐white photographs. Multitemporal analysis of landscape indices has been performed to detect changes of landscape elements and related effects on vegetation dynamics due to the reduction of human impact.
Vegetation of the woodland‐steppe transition at the southeastern edge of the Inner Mongolian Plateau
Authors: Liu Hongyan , Cui Haiting , Pott Richard , Speier Martin
Published: May 2006

Abstract. The vegetation of the woodland‐steppe transition in southeastern Inner Mongolia, where the East Asian monsoon climate reaches its northwestern edge, is described and analysed in this paper. The communities are classified in a phytocoenological way. 12 major types of woodland, shrubland, meadow, fen, open woodland and steppe are differentiated and described on the basis of 133 phytosociological relevés. Detrended Correspondence Analysis shows that precipitation plays a crucial role in the distribution of grassland communities while woodland and shrubland communities are controlled by both warmth and humidity conditions.

Four vegetation zones can be distinguished. From the woodland to the woodland‐grassland zone, the temperature decreases and the precipitation increases with increasing altitude, which leads to the conditions suitable for the meadow and fen communities. In the direction of the woodland‐steppe zone the temperature increases while the precipitation decreases with the gradual lowering of the altitude; the steppe communities form a matrix while the woodlands have a patchy distribution. From the woodland‐steppe to the steppe zone, the precipitation rather than temperature decreases; as a result the woodland communities disappear gradually. On a local scale, geomorphologic conditions determine the vegetation pattern of the study area. Due to the existence of a sandy substrate different woodland types occur together in the woodland‐steppe transition. The local distribution of woodland and steppe communities is dependent on slope conditions. In addition, human disturbance has also influenced the composition of plant communities.
Understorey vegetation development in North Finnish Picea forests after disturbance: re‐analysis of Sirén's data
Authors: Økland Rune Halvorsen
Published: May 2006

Abstract. Sirén (1955) studied understorey species composition, tree stand properties and humus‐layer thickness in 64 unlogged forest stands on topographically and pedologically comparable sites. The stands were of even age (6 – 300 yr), stocked with the first or second tree generation after wildfire. The view of Sirén and several authors after him, that the vegetation of old‐growth boreal Picea forests is homogeneous on a broad scale, was examined by applying, in parallel, the partial variants of two ordination methods (DCA and PCA) to Sirén's vegetation data. Two main vegetation gradients were found: a major gradient running from recently burnt plots with prominence of pioneer species to plots with stand age > 100 yr, a well stocked tree layer and a thick humus layer, dominance of feather‐mosses and ample occurrence of shade‐tolerant as well as light‐preferring vascular plant species, and a second gradient along which first‐ and second‐generation plots segregate. The more prominent element of Betula trees in first‐ than in second‐generation stands < 100 yr contributed to the latter. A minor third gradient related to humus‐layer thickness was recovered by partial DCA only. The main vegetation gradient reappeared in separate ordinations of data from 47 mature forest stands (> 100 yr), but without being correlated with forest age. Variation among mature‐forest stands in the importance of pioneer species is considered mainly to be brought about by fine‐scale disturbance processes such as tree uprooting. Increasing importance of factors operating on within‐stand scales [development of a varied gap structure and stronger gradients in tree influence (radiation at ground level), soil moisture, soil depth and nutrient availability] with time is also reflected in the second and third mature‐forest ordination axes. Possible implications of the results for conservation of biological diversity and monitoring of changes in boreal forests are discussed.
Vegetation and environment of a New Zealand raised bog
Authors: McQueen Amelia A.M. , Wilson J. Bastow
Published: May 2006

Abstract. The vegetation of a mire in a medium‐high rainfall area of South Island, New Zealand is described. The central part of the bog is raised 6 m above the surroundings, suggesting that it is ombrotrophic, and the species present are those of apparently ombrotrophic bogs elsewhere in New Zealand. pH of < 4.0 and Ca/Mg molar quotient of < 1.0 also indicates ombrotrophic conditions. Within the mire, these criteria provide effective discrimination between the fen (rheotrophic) and bog (ombrotrophic) communities. A bimodal distribution of ordination scores suggests that the change in pH and in Ca/Mg quotients cause a switch to operate.
Two Senators under Constantine
Authors: Barnes T. D.
Published: May 2006

A handbook of astrology seems an improbable source of information about Constantine's dealings with the Roman Senate. Yet if the work were contemporary, and if both author and addressee were senators, then a few passages might betray a hint of transactions either not otherwise attested or not elsewhere documented in any detail. Such is in fact the case with the Mathesis of Julius Firmicus Maternus Junior v.c., of which one passage in particular can be made to disclose specific facts of some historical importance. Maternus discusses the horoscope of a man, whose father was exiled after twice being ordinary consul, and whose own career advanced from exile to the urban prefecture of Rome. Neither is named; they were familiar to both the author and the addressee of his work.