Cover Of Shrub Layer Research Articles

Green tree retention as a conservation tool for the black woodpecker in managed forests

The black woodpecker, Dryocopus martius, a creator of tree cavities, is considered a keystone species and a priority in terms of forest biodiversity conservation. The aim of this paper was to understand how the structure of managed forests impacts the choice of tree for excavating cavities of the black woodpecker. The study was conducted in an extensive forest complex in northeastern Poland dominated by the pine Pinus sylvestris. The parameters of the cavity trees and surrounding forest were analyzed on different levels to determine what trees and stand types were selected by the black woodpecker. In the period from 2018 to 2021, analyses were carried out for 367 cavities excavated in trees growing in forest areas from 0 to 225 years old. The most numerous cavity trees were between 121 and 160 years old. Cavity trees were found in the stands (62%), in the residual forest patches (19%) and in the single trees remaining after logging (19%). Forty-four percent of all cavities were excavated in dead trees. Black woodpecker nesting stands were characterized by lower canopy closures and low understory and shrub layer cover. We did not find a difference between the diameters or the heights of cavity entrances among the black woodpecker nesting trees growing in different habitat types. The black woodpecker is capable of nesting in small fragments of an old stand and even in single old trees growing in clearcut areas. This is due to the high proportion of dead trees in these habitats, which are preferred by woodpeckers for excavating cavities. Leaving patches of old-growth stands in commercial forests positively affects the habitat formation of the black woodpecker and perhaps, as a consequence, that of other animal species that depend on it.

Plants, soil properties and microbes directly and positively drive ecosystem multifunctionality in a plantation chronosequence

AbstractChinese fir (Cunninghamia lanceolata) is the main plantation species in the subtropical region of China. However, the shift in ecosystem multifunctionality with stand development remains largely unexplored for these plantations. This study used a chronosequence to investigate the variations of ecosystem multifunctionality by employing individual functions and identified its driving factors in Chinese fir plantations. The findings provide strong evidence that the individual functions of carbon stocks, water regulation and wood production increased with stand ages, but the tradeoff of individual functions did not significantly increase ecosystem multifunctionality. Soil microbial parameters (the abundances of bacteria, fungi and actinomycete), soil properties (soil moisture, total carbon and total nitrogen), and plant parameters (the shrub layer cover and total understory cover) exhibited positive correlations with ecosystem multifunctionality. The structural equation model revealed that plants, soil properties and microbes pathways explained 83% of the total variance in ecosystem multifunctionality. Results showed that plants, soil microbes and properties directly and significantly affected ecosystem multifunctionality with path coefficients of 0.404, 0.487 and 0.334, respectively. Soil microbes were identified as the top direct predictor for ecosystem multifunctionality, while plant and soil properties had strong direct and positive effects on ecosystem multifunctionality. These results verified that soil microbes, plants and soil properties directly and positively regulated ecosystem multifunctionality. Our findings demonstrate that ecosystem multifunctionality should be considered as a comprehensive ecological indicator for ecosystem services and functions, and sustainable plantation management. This study highlights the importance of conserving soil microbes for maintaining multifunctionality in Chinese fir plantations.

Effects of Increasing Fire Frequency on Conservation Values in Eucalyptus Grassy Woodland in the Process of Invasion by Allocasuarina verticillata

Woody thickening is a widespread phenomenon in the grassy woodlands of the world, often with deleterious effects on nature conservation values. We aimed to determine whether increasing the frequency of planned fire prevented woody thickening and improved conservation values in a Eucalyptus viminalis grassy woodland in the process of invasion by Allocasuarina verticillata (henceforth Allocasuarina) in Hobart, Tasmania, Australia. We used a before–after control intervention design. Ten plots from which detailed vegetation data were collected in 2018 (before the burns), 2019 (between burns), 2020 (between burns) and 2021 (after the burns) were randomly located in each of four blocks. Two of the blocks were burned in both 2018 and 2021. One block was burned only in 2021, and another was not burned at all. Mechanical thinning of Allocasuarina took place in 2021 in six plots in one unburned block and in three twice-burned plots. The fires were low intensity and patchy, reflecting the reality of planned burns in this environment. Thus, there were unburned plots mixed with burned plots in each of the three burned blocks. We compared changes in vegetation and cover attributes between a preburn survey in 2018 and a postburn survey in 2021, between five fire history/thinning classes (unburned, no thinning; unburned, thinning; twice burned; burned in 2018 only; burned in 2021 only). Fires in both 2018 and 2021 resulted in lower litter cover and higher exotic species richness than one fire in 2021. Exotic species richness increase between 2018 and 2021 was greater after fires in 2018 and 2021 than after a fire in 2021 alone. Exotic species richness was lowest six years after fire and highest one to three years after fire. The basal area of Allocasuarina was, counter-intuitively, less reduced by two fires in four years than by one. Mechanical thinning reduced shrub layer cover, which largely consisted of small trees, but did not affect basal area. Our data suggested that grass cover increased until five years after a fire, declining back to a low level by eight years. The implications of the results for conservation management are that the mechanical removal of young Allocasuarina may be successful in preventing its thickening and that burning at a five-year interval is likely to best maintain understorey conservation values. The counter-intuitive results related to Allocasuarina basal area emphasise the importance of understanding cumulative effects of fire regimes on fuel cycles and the consequent effects on tree mortality.

Deer and invasive plants in suburban forests: assessing variation in deer pressure and herbivory

ABSTRACT Fragmented suburban forests of the northeastern US are challenged by abundant white-tailed deer and nonindigenous plant invasions. Deer browsing/grazing pressure varies among sites, potentially affecting herbivory on nonindigenous plants and their invasion success. We aimed to identify a useful deer pressure indicator for suburban forests and then use it to relate deer pressure to grazing on and abundance of two herbaceous invaders, Microstegum vimineum and Alliaria petiolata. We compared three indicators: fecal pellet accumulation rate, deer browse on indigenous woody plants, and indigenous shrub layer cover. The pellet method produced estimates generally far below the region’s known deer density. Browse rates and shrub layer cover were negatively correlated, and correlations of the three indicators with evidence of deer pressure from a subsequent 6.5-year exclosure experiment supported shrub layer cover as the better choice. Using that measure in 10 forests, we detected a weak pattern of more grazed stands under greater deer pressure, but few plants per stand were grazed; any negative influence of deer on these species was limited to individuals, without population effects. Alliaria petiolata abundance was unrelated to deer pressure, but M. vimineum abundance was greater in forests with more deer pressure, suggesting facilitation of its invasion.

Large standard trees and deadwood promote functional divergence in the understory of beech coppice forests

How species assemble in a community is still an unresolved question in ecology, especially in forest ecosystems. In temperate forests, the understory layer includes most of the plant diversity and significantly contributes to ecosystem functions. Understory communities are susceptible to changes in environmental conditions linked to forest structural features. Understanding how understory assemblages respond to these features can provide useful suggestions for sustainable forest management. We selected 68 abandoned coppice-with-standards beech forest stands in central Italy. We recorded plant species presence and abundance and several structural variables, including total stem density, height and basal area of standard trees, the abundance of lying deadwood, and shrub layer cover. Different plant traits informative on key ecological functions were attributed to understory plants to calculate the single- and multi-trait functional diversity (FD) expressed as Rao's quadratic entropy. Linear-mixed models were used to assess the relationship between structural parameters and single- and multi-trait FD. We found that the size of standard trees and lying deadwood were the main structural drivers of trait-based understory assemblages. Larger standards and a higher amount of lying deadwood contributed to reduce multi-trait convergent patterns or to shift patterns from convergence to divergence (for reproductive height, seed mass, specific leaf area, and leaf area), probably due to modulation of resource amount and heterogeneity (i.e., light and nutrients). Our results feed the debate on the sustainable management of coppice forests. We suggest that the understory functional diversity of montane beech forests could be enhanced if forest management practices allow the release of larger standards (height > 19 m; basal area > 35 m2/ha) and the accumulation of deadwood (cover > 7%).

Disentangling the Ecological Determinants of Species and Functional Trait Diversity in Herb-Layer Plant Communities in European Temperate Forests

Forest herb-layer vegetation responds sensitively to environmental conditions. This paper compares drivers of both taxonomic, i.e., species richness, cover and evenness, and functional herb-layer diversity, i.e., the diversity of clonal, bud bank and leaf-height-seed plant traits. We investigated the dependence of herb-layer diversity on ecological determinants related to soil properties, climatic parameters, forest stand characteristics, and topographic and abiotic and biotic factors associated with forest floor structure. The study was conducted in different forest types in Slovenia, using vegetation and environmental data from 50 monitoring plots (400 m2 each) belonging to the ICP Forests Level I and II network. The main objective was to first identify significant ecological predictors and then quantify their relative importance. Species richness was strongly determined by forest stand characteristics, such as richness of the shrub layer, tree layer shade-casting ability as a proxy for light availability and tree species composition. It showed a clear positive relation to soil pH. Variation in herb-layer cover was also best explained by forest stand characteristics and, to a lesser extent, by structural factors such as moss cover. Species evenness was associated with tree species composition, shrub layer cover and soil pH. Various ecological determinants were decisive for the diversity of below-ground traits, i.e., clonal and bud bank traits. For these two trait groups we observed a substantial climatic signal that was completely absent for taxonomy-based measures of diversity. In contrast, above-ground leaf-height-seed (LHS) traits were driven exclusively by soil reaction and nitrogen availability. In synthesis, local stand characteristics and soil properties acted as the main controlling factors for both species and trait diversity in herb-layer communities across Slovenia, confirming many previous studies. Our findings suggest that the taxonomic and functional facets of herb-layer vegetation are mainly influenced by a similar set of ecological determinants. However, their relative importance varies among individual taxonomy- and functional trait-based diversity measures. Integrating multi-faceted approaches can provide complementary information on patterns of herb-layer diversity in European forest plant communities.

Stand attributes or soil micro-environment exert greater influence than management type on understory plant diversity in even-aged oak high forests

Understanding the determinants of forest understory diversity provides a theoretical basis for sustainable management practices. Our study aimed to identify the dominant factors determining understory diversity in temperate forests among three potentially important factors: management type (managed vs unmanaged), stand attributes (basal area by species and by diameter class, shrub layer cover) and soil micro-environment (soil compaction and soil moisture). Understory diversity was represented by the richness and abundance of plant ecological groups based on life form crossed with successional status, light and moisture requirements. We selected 50 stands in five French national forests, half of which were managed and half unmanaged. After model comparison, our results showed that, depending on the ecological groups studied, basal area and micro-environment rather than management type were the best explanatory models for understory diversity. Our magnitude analyses showed that understory diversity did not differ much between managed and unmanaged forests. Basal area, which had ecologically important effects, negatively correlated with understory diversity. For two ecological groups (mature-forest and shade-tolerant woody species), diversity was better explained by basal area in interaction with management type than by the sole effect of basal area. Soil micro-environment, which had ecologically important effects, mostly showed positive relationships with understory diversity; e.g. hygrophilous and intermediate-light herbaceous species positively correlated to soil moisture, while heliophilous herbaceous species were positively correlated to soil compaction. Our study indicated that forest management abandonment after 20–40 years did not induce higher understory diversity than in managed forests; abandonment’s role in understory diversity was weak compared to basal area or soil environment. Whether such results persist after longer periods of abandonment remains unknown.

How Forest Gap and Elevation Shaped Abies faxoniana Rehd. et Wils. Regeneration in a Subalpine Coniferous Forest, Southwestern China

Focusing on the underlying ecological mechanisms of dominant species regeneration in forest gaps at a landscape scale can provide detailed understanding for gap-based forest management. The individual effects of forest gaps or elevation on the regeneration of Abies faxoniana Rehd. et Wils. are well known, although elucidating how gap characteristics and elevation concurrently influence regeneration remains an important challenge. In this paper, we present an explorative study using structural equation models (SEMs) to assess the direct and indirect effects of forest gaps and elevation on Abies faxoniana Rehd. et Wils. regeneration. Four of the predicted SEMs showed the following results: (1) Temperature, photosynthetic photon flux density (PPFD), soil total carbon, gap openness, shrub layer cover, herb layer cover, and moss layer thickness in forest gaps were associated with Abies faxoniana regeneration along an elevation gradient in subalpine coniferous forest. (2) Elevation had a generally negative and indirect effect on Abies faxoniana regeneration. Forest gaps positively affected regeneration when compared with non-gap plots and gap size was positively related to small tree regeneration density and the ratio of height to diameter at breast height (HD ratio) of the tallest Abies faxoniana small trees but was negatively related to Abies faxoniana sapling regeneration density. (3) In forest gaps, the Abies faxoniana sapling density and HD ratio of the tallest Abies faxoniana small trees were mainly indirectly influenced by elevation, and Abies faxoniana small tree regeneration density was directly associated with the dominance of the sapling regeneration density. In summary, Abies faxoniana regeneration was negatively and largely affected by elevation (total effect), although forest gaps enhanced Abies faxoniana regeneration by multiple pathways (direct and indirect effects).

Tree species identity outweighs the effects of tree species diversity and forest fragmentation on understorey diversity and composition

Background & aim : In general, biodiversity has positive effects on ecosystem functioning. In forests, understorey vegetation is influenced by both the composition and species richness of the overstorey through species-specific effects on environmental conditions at the forest floor. Forest fragmentation is also known to influence understorey vegetation composition and richness. However, the combined effects of tree species diversity and forest fragmentation have not been studied yet. With the TREEWEB research platform, consisting of 53 forest plots along a tree species diversity and forest fragmentation gradient, we aim to unravel the combined effects of tree species diversity, tree species identity and forest fragmentation on the understorey composition and diversity. Methods : The TREEWEB platform includes forest plots of three tree species richness levels, containing all possible species combinations of Quercus robur, Quercus rubra and Fagus sylvatica. Complete dilution is avoided in the design, allowing separation between tree species identity and diversity effects. Vegetation surveys were conducted in all plots to investigate the species richness, species diversity, compositional turnover and cover of the herb layer as well as the shrub layer cover. Key results : Within the TREEWEB platform, overstorey-understorey diversity relationships were mainly characterised by tree species identity effects. No clear effects of tree species diversity and forest fragmentation on understorey composition and diversity were found. Conclusion : Tree species identity effects were most important in explaining the observed patterns in the understorey vegetation. Further in-depth research will allow us to disentangle which mechanisms underlie these patterns and whether effects of fragmentation are more pronounced at higher trophic levels.

Forest structure as a determinant of grouse brood occurrence – An analysis linking LiDAR data with presence/absence field data

Forest-dwelling grouse, and especially their broods, are highly dependent on forest and vegetation structure. In countries with intense forest management, it follows that the quality of their habitats is directly affected by forestry operations. Therefore, we must know which structural features of forests define a good grouse habitat and how the abundance of these features is affected by the forestry operations. Nowadays, airborne lidar (light detection and ranging) is being frequently used for forest inventories and terrain mapping. These data is becoming more and more publicly available and it holds detailed information about the forests and the vegetation structure; a key component of wildlife habitats.In this study, we integrated lidar data with grouse brood presence/absence data. Through GLMM modelling, we aimed (1) to identify the structural features of forests that mostly determine grouse brood occurrence and (2) to assess how they are affected by forest management. The three species assessed were capercaillie, hazel grouse and black grouse. Depending on species, the brood presence was positively (and significantly) affected by denser shrub layer cover, denser canopy cover, higher canopies, or all of these features. The results indicate that grouse broods are highly susceptible to changes in forest structure.In countries like Finland, game management is almost always implemented in managed forests, which in the light of our results creates a need to integrate habitat management into forest management. Our results suggest that when managing grouse brood habitats, attention should be given to maintain both, protective canopy cover and a good understorey cover. It is fair to assume that the removal of these components will significantly decrease brood occurrence. Further, the study showed that a dataset (lidar) collected more for the purposes of forestry can also be used to study wildlife habitats occurring often in the same forests.

Interactions between overstorey and understorey vegetation along an overstorey compositional gradient

AbstractQuestionsWhat is the nature of the interactions between higher vegetation strata (overstorey) and lower strata (understorey vegetation) and among understorey vegetation layers in closed canopy forests? How does the abundance or richness of one vegetation layer affect the abundance or richness of the other?LocationBoreal mixed‐wood forests ofOntario andQuebec,Canada.MethodsWe sampled fire‐origin stands of varying overstorey composition from broad‐leaf‐dominated to mixed to conifer‐dominated stands on mesic sites inOntario and subhydric sites inQuebec. Overstorey tree species composition and understorey shrub, herb, bryophyte and lichen species cover and richness were estimated within 400‐m2circular plots. In addition, soil nutrients, coarse woody debris and light conditions were measured. Overstorey composition was expressed as the percentage basal area of broad‐leaf tree species. Path analysis was used to examine interactions among the forest layers.ResultsOverstorey broad‐leaf composition had positive effects on shrub and herb layer cover and herb layer richness, and negative effects on bryophyte and lichen species cover and richness. Shrub layer cover had no effect on herb layer cover, but shrub layer richness had a positive effect on herb layer richness. Herb layer cover and richness had negative effects on bryophyte species cover and richness. Bryophyte cover had no effect on lichen cover, but its richness was positively related to lichen richness. In both regions, soil pH, total nitrogen, total phosphorus and cation exchange capacity of the forest floor were positively correlated with overstorey broad‐leaf composition and with shrub layer cover and herb layer cover.ConclusionsIncreasing overstorey broad‐leaf composition, through its influence on soil nutrients, promotes shrub and herb layer species, but limits bryophyte and lichen species. In the overstorey‐controlled understorey resource environment, cover and richness of shrub and herb layers increase with resource availability, whereas bryophytes and lichens show positive associations with abundance of coarse woody debris.

A functional analysis of vegetation dynamics in abandoned and restored limestone grasslands

AbstractQuestion: How do various plant functional groups and types are related to regeneration of limestone grasslands and to temporal changes in cover of trees and shrubs? Which mechanisms are responsible for changes in differently treated grasslands?Location: Southern Poland, 50° 01'N, 19° 50'E.Methods: A 12‐year restoration experiment after the clearing of a 35‐yr‐old secondary pine wood developed on limestone grassland, and a parallel observation of succession in neighbouring abandoned grassland were carried out. Changes in cover of species with different functional traits and established strategies in relation to time and cover of shrub layer were analysed using multiple linear regression.Results: Over 12 years the composition and cover of species changed in the studied grasslands, but significant differences still occurred between the old grassland and the grassland restored in former wood gaps and that developed in former closed wood. Despite the very close proximity of the old grassland, the composition of restored grasslands was still much determined by initial conditions. In these grasslands, the cover of Festuco‐Brometea species was significantly lower than in the old grassland. In all sites, the cover of species with large leaves and with leaves distributed regularly along the stem, and the cover of CS strategists increased. With increasing shrub cover in restored grasslands, the cover of annuals and biennials, tall species, and R and CS strategists decreased.Conclusions: Limited availability of seeds seems the principal reason for the weak regeneration of xerothermic limestone grasslands. Trees and shrubs inhibit the developed of both early successional species and perennials occurring in established communities. They significantly hinder regeneration of grasslands and should be cut every five or six years.

A functional analysis of vegetation dynamics in abandoned and restored limestone grasslands

Question: How do various plant functional groups and types are related to regeneration of limestone grasslands and to temporal changes in cover of trees and shrubs? Which mechanisms are responsible for changes in differently treated grasslands? Location: Southern Poland, 50° 01'N, 19° 50'E. Methods: A 12-year restoration experiment after the clearing of a 35-yr-old secondary pine wood developed on limestone grassland, and a parallel observation of succession in neighbouring abandoned grassland were carried out. Changes in cover of species with different functional traits and established strategies in relation to time and cover of shrub layer were analysed using multiple linear regression. Results: Over 12 years the composition and cover of species changed in the studied grasslands, but significant differences still occurred between the old grassland and the grassland restored in former wood gaps and that developed in former closed wood. Despite the very close proximity of the old grassland, the composition of restored grasslands was still much determined by initial conditions. In these grasslands, the cover of Festuco-Brometea species was significantly lower than in the old grassland. In all sites, the cover of species with large leaves and with leaves distributed regularly along the stem, and the cover of CS strategists increased. With increasing shrub cover in restored grasslands, the cover of annuals and biennials, tall species, and R and CS strategists decreased. Conclusions: Limited availability of seeds seems the principal reason for the weak regeneration of xerothermic limestone grasslands. Trees and shrubs inhibit the developed of both early successional species and perennials occurring in established communities. They significantly hinder regeneration of grasslands and should be cut every five or six years.

Variation of soil and site parameters on extensively and intensively grazed hillslopes in semiarid Cuba

In mountainous semiarid southeastern Cuba, livestock is mainly kept on freely accessible state land. In one of these areas, intensively and extensively grazed hillslope areas were investigated. Four transects were laid along toposequences distinguishing six different slope positions. Soil parameters and soil depth were analysed, and covers of herb and shrub layer were estimated as well. Besides the toposequence analyses, four small-scale transects were laid across two shrub and two cacti investigating microtopography and soil depth. Lower parts of the slopes were generally found to be more degraded compared to upper parts. Organic C and total N at intensively and extensively grazed areas as well as cover of herb and shrub layer at intensively grazed areas decreased down the slope, whereas soil depth increased. However, higher vegetation cover at upper slope parts seemed not to be able to impede soil erosion as lower soil depths at upper parts indicated. Upslope and downslope of shrubs and cacti, greater soil depth was found compared to areas without shrubs or cacti due to reduced soil erosion. In general, higher average values of the parameters analysed were found for the extensively compared to the intensively grazed areas, but only few differences were significant for the different slope positions. Significant changes along the toposequences for organic C, total N, CaCO 3, cover of shrub layer and cover of stones, which were almost exclusively found for intensively grazed areas show that higher grazing pressure increased differences along the slope.

Relative importance of resource quantity, isolation and habitat quality for landscape distribution of a monophagous butterfly

Fragmentation of food resources is a major cause of species extinction. We tested the effects of habitat area, isolation and quality for the occurrence and population density of the endangered butterfly Polyommatus coridon. Polyommatus coridon larvae are monophagous on the plant Hippocrepis comosa, and both species are specialised on calcareous grassland, which is an endangered and highly fragmented habitat type in Germany.In 2001 we surveyed all known calcareous grasslands (n=298) around the city of Göttingen (Germany) to map the population size of H. comosa in these habitats. Further, habitat isolation (between‐patch distance: 70–7220 m) and habitat quality (cover of flowering plants, height of herb layer, percent bare ground, cover of shrub layer, wind protection, inclination) were quantified. Hippocrepis comosa occurred on only 124 fragments, which were then surveyed by 20 min transect counts for adult P. coridon in 2001 and 2002.Occurrence and population density of P. coridon were largely determined by the population size of its larval food plant, which was correlated with grassland area. Effects of habitat isolation and habitat quality on P. coridon populations contributed only little to the explanation.In conclusion, this monophagous habitat specialist depended on large habitats with large food plant populations to exist in viable populations. Habitat isolation and quality appear to contribute to occurrence and density patterns only in landscapes where these factors shift towards extremes, therefore general recommendations for conservation programs are difficult as they depend on regional distinctions.

Landscape occupancy and local population size depends on host plant distribution in the butterfly Cupido minimus

We tested whether the landscape occupancy and local population size of the monophagous butterfly Cupido minimus can be predicted by patch size and isolation of its host plant or by other habitat characteristics. C. minimus and its larval food plant Anthyllis vulneraria are classified as rare and endangered in northern Germany. Adults of C. minimus are ranked as the most sedentary butterfly species in northern Europe. Around the city of Göttingen (Germany), we checked all known locations of A. vulneraria ( n=70) in June 2002 for butterfly eggs (in blooming flowerheads) and adult butterflies (within 20-min transects). We found eggs of C. minimus or a high number of adults (>7) in all habitats with A. vulneraria (which are calcareous grasslands) even when isolated up to 2–4 km. In multiple regression analyses, local population size of adult butterflies was positively related to the cover of its larval food plant A. vulneraria explaining 65% of variance. Cover of A. vulneraria increased with increasing habitat area and increasing cover of plant species in flower and decreased with increasing cover of shrub layer. Habitat isolation and further factors describing habitat quality were not related to C. minimus population size or cover of its larval food plant. The results suggest that dispersal ability of C. minimus is greater than expected and that management should focus to increase A. vulneraria patches. For conservation, low impact grazing once a year and removing of excessive shrubs in winter seems to be the most appropriate strategies.

Habitat selection by barbastelle bats (Barbastella barbastellus) in the Swiss Alps (Valais)

AbstractRecent faecal analyses have shown that barbastelle bats Barbastella barbastellus are highly specialized moth predators. The predominance of moths (> 99% by volume) in their diet both in wooded areas of the Swiss Alps and in denuded steppe areas of Central Asia further suggests that this narrow diet does not stem from a highly specialized habitat selection, but merely from peculiar species‐specific foraging constraints. Non‐opportunistic predators relying on a few prey types must find areas providing their basic prey in abundance. Using radiotracking, habitat selection was investigated in a population of barbastelle bats inhabiting xeric forests in the Swiss Alps. In particular, I tested the prediction that the biologically most productive areas within the forest are exploited in priority. Eleven individuals were radiotracked from June through to October 1992, and in June 1993. The home range (59 ha) of the overall radiotracked population was divided in 236 cell units of 0.25 ha each. Within each cell, habitat and vegetation structure was described using 19 environmental variables. Habitat selection by the bats was investigated through stepwise regression analysis, which retained 11 variables showing a significant positive relationship with habitat use. The four variables accounting for 31% of the overall variance were: litter thickness, percentage of shrub layer cover, percentage of pine tree cover, and circumference of oak trunks. The results showed a clear preference by barbastelles bats for richly structured forests, and an avoidance of open woodland on stony outcrops and rocky slopes. This confirms that the biologically most productive parts of the forest were exploited in priority.

Habitat selection by barbastelle bats (Barbastella barbastellus) in the Swiss Alps (Valais)

Recent faecal analyses have shown that barbastelle bats Barbastella barbastellus are highly specialized moth predators. The predominance of moths (> 99% by volume) in their diet both in wooded areas of the Swiss Alps and in denuded steppe areas of Central Asia further suggests that this narrow diet does not stem from a highly specialized habitat selection, but merely from peculiar species-specific foraging constraints. Non-opportunistic predators relying on a few prey types must find areas providing their basic prey in abundance. Using radiotracking, habitat selection was investigated in a population of barbastelle bats inhabiting xeric forests in the Swiss Alps. In particular, I tested the prediction that the biologically most productive areas within the forest are exploited in priority. Eleven individuals were radiotracked from June through to October 1992, and in June 1993. The home range (59 ha) of the overall radiotracked population was divided in 236 cell units of 0.25 ha each. Within each cell, habitat and vegetation structure was described using 19 environmental variables. Habitat selection by the bats was investigated through stepwise regression analysis, which retained 11 variables showing a significant positive relationship with habitat use. The four variables accounting for 31% of the overall variance were: litter thickness, percentage of shrub layer cover, percentage of pine tree cover, and circumference of oak trunks. The results showed a clear preference by barbastelles bats for richly structured forests, and an avoidance of open woodland on stony outcrops and rocky slopes. This confirms that the biologically most productive parts of the forest were exploited in priority.

Distribution of seedlings and saplings of Quercus robur in a grazed deciduous forest

AbstractSeedling and sapling distribution of the deciduous tree Quercus robur was, studied in a grazed, partly open forest, ca. 20 km S of Linkoping, Sweden. Numbers of seedlings and saplings were compared between open and shaded parts of the forest. Cover values for the shrub and tree layers, proportion of bare ground and of stones and soil water content were determined. Q. robur was shown to germinate equally well in open and shaded parts of the forest; however, most saplings were found in the shade. No correlation was found between seedlings or saplings and cover of shrub layer or proportion of stones in the soil surface or with soil water content.

Local distribution of two species of Apodemus in Kyushu

Local distributions of two species ofApodemus, A. argenteus andA. speciosus, were studied by the correct estimation of peak density of mice and the detailed description of the habitat. Multiple regression analysis is applied to these distributional data setting with four variables as altitude, forest type, relative cover of shrub layer and age of forest. The local densities of both species and the percentage abundance ofA. argenteus can be completely predicted by use of the regression coefficients. The density ofA. speciosus correlates with the altitude of habitats, and that ofA. argenteus does with the age of forest. The mean relative cover of shrub layer influences the dominancy ofA. argenteus when both species occur sympatrically.