The effects of stand structure on ground-floor bryophyte assemblages in temperate mixed forests

The effect of tree species composition, stand structure characteristics and substrate availability on ground-floor bryophyte assemblages was studied in mixed deciduous forests of Western Hungary. Species composition, species richness and cover of bryophytes occurring on the soil and logs were analysed as dependent variables. The whole assemblage and functional groups defined on the basis of substrate preference were investigated separately. Substrate availability (open soil, logs) was the most prominent factor in determining species composition, cover and diversity positively, while the litter of deciduous trees had a negative effect on the occurrence of forest floor bryophytes. Besides, bryophyte species richness increased with tree species and stand structural diversity, and for specialist epiphytic and epixylic species log volume was essential. Sapling density and light heterogeneity were influential on bryophyte cover, especially for the dominant terricolous species. Many variables of the forest floor bryophyte community can be estimated efficiently by examining stand structure in the studied region. Selective cutting increasing tree species diversity, stand structural heterogeneity and dead wood volume can maintain higher bryophyte diversity in this region than the shelter-wood system producing even-aged, monodominant, structurally homogenous stands.     

Environmental drivers of the bryophyte propagule bank and its comparison with forest-floor assemblage in Central European temperate mixed forests

Species richness, composition and abundance of the bryophyte diaspore bank of Central European temperate mixed forests were compared with the forest-floor bryophyte assemblage. The impact of environmental variables and anthropogenic disturbances, including tree species composition, stand structure, microclimate, light conditions, soil and litter properties, management history, and landscape properties, potentially influencing bryophyte diaspore bank assemblages were explored. Thirty-four, 70–100 years old mixed stands with differing tree species composition were examined in the ?rség National Park, Western Hungary. The diaspore bank was studied by soil collection and cultivation, and data were analysed by multivariate methods. Contrary to the forest-floor bryophyte assemblage, where substrate availability, tree species composition and stand structure were the most influential environmental variables, the composition and abundance of the diaspore bank was mainly affected by site conditions (microclimate, litter and soil properties). Species richness of the bryophyte diaspore bank was lower than that of the forest-floor bryophyte assemblage. Short-lived mosses (colonists, short-lived shuttles) were dominant in the diaspore bank, as opposed to the forest-floor bryophyte community, where perennial mosses dominated. In the studied forests, the importance of the bryophyte diaspore bank was relatively low in the regeneration and maintenance of the forest-floor bryophyte vegetation.     

Forest biodiversity gradients and the human impact in Annapurna Conservation Area, Nepal

Patterns of biodiversity, environment and human impact were studied in 57 sample plots in an 1,178 ha forest area in a rural mountain area of Nepal that is administrated by the Annapurna Conservation Area Project. Alpha-, beta- and gamma-diversity was measured or estimated for six groups of organisms: trees, shrubs, climbers, herbs, polypores and mycorrhizal fungi, and the recorded patterns were correlated with a set of environmental variables. Human impact in terms of fuelwood collection, selective cutting and grazing was found to influence species diversity patterns in all organism groups. Species richness of trees, climbers and polypores at plot level (alpha-diversity) generally responded negatively to human impact, whereas species richness of herbs and shrubs showed a positive relation. Species turnover (beta-diversity), measured as length of the DCA first axis, was significantly correlated to distance to village for all species groups. This indicates that the human impact is very important for the biodiversity patterns in the study area, and that biodiversity connected to undisturbed forest habitats are potentially threatened in the area. The results are discussed in the context of practical conservation. A proposal for future management zones addressing protection of biodiversity without limiting the local use of the forest resource is put forward.     

The effects of habitat edges and trampling on understorey vegetation in urban forests in Helsinki,Finland

Question: How do habitat edges and trampling affect mesic (Myrtillus type) understorey vegetation in fragmented urban forests, and what are the relative strengths and spatial extent of these effects? Location: The city of Helsinki, southern Finland. Methods: Vegetation sample plots were placed at different distances from the forest edge. At each distance we selected plots on, next to and away from paths of different levels of wear, and the covers and frequencies of plant species were sampled. We used generalized linear mixed models and ordination techniques to test our hypotheses. Results: The effect of the edge penetrated up to 50 m into the forest interior. Only light effects of trampling were found in seemingly untrampled areas, in addition to the direct effects of trampling on the paths. Both trampling and edge effects changed the forest understorey species composition. Trampling changed plant species composition locally on paths, and provided opportunities for new species to establish in previously unbroken forest vegetation. Urban forest edges were characterised by species better adapted to sunny, warm and dry conditions. These species, such as grasses, replaced more sensitive forest species, such as dwarf shrubs and mosses. We observed a large number of light demanding deciduous trees at the edges, which may be one of the factors increasing soil fertility and consequently promoting the high abundance of fast growing species, such as grasses and herbs related to more fertile site types. Conclusions: We recommend that urban forest fragments left within urban development should be at least 2–3 ha in size and that the shape of the patch and the number of potential recreational users should be taken into account when preserving true forest understorey vegetation from the effects of edges and trampling.     

Upward migration of vascular plants following a climate warming trend in the Alps

The aim of this study was to understand (1) whether warmer climatic conditions affected the vascular plant species composition, (2) the magnitude and rate of altitudinal changes in species distributions, and (3) whether an upward migration of alpine plants is connected to wind dispersal of diaspores. We compared historical records (1954–1958) with results from recent plant surveys (2003–2005) from alpine to nival ecosystems in the Rhaetian Alps, N-Italy. The presence of all vascular plant species and their maximum altitude were recorded along a continuous altitudinal transect of 730 m. An increase in species richness from 153 to 166 species was observed. Moreover, 52 species were recorded from altitudes 30–430 m higher than their 1950s limits, which corresponds to a median migration rate of 23.9 m/decade. In order to explain the observed migrations, the species wind-dispersal ability (diaspore weight and morphology) and the air temperature variation from 1926 to 2003 were considered. Species with more pronounced altitudinal shifts possess lighter diaspores. The highest increase in species richness was found between 2800 and 3100 m a.s.l.; this appears to be related to an estimated shift of the permafrost limit by +240 m during the last 50 years. The mean air temperature in the region rose by +1.6 °C in summer and by +1.1 °C in winter within this period. Climate warming is therefore considered as a primary cause of the observed upward migration of high mountain plants. Calculated altitudinal migration rates, however, varied remarkably among species. This would imply differential abilities of species to persist in an increasingly warmer climate. Species-specific conservation measures, including ex situ conservation, may therefore be required.     

Changes in plant species richness over the last century in the eastern Swiss Alps: elevational gradient, bedrock effects and migration rates

Areas of 2,800–3,000 m a.s.l. represent the alpine-nival ecotone in the Alps. This transition zone connecting the closed swards of the alpine belt and the scattered vegetation of the nival belt may show particularly strong climate warming driven fluctuations in plant species richness compared to the nival belt. To test this hypothesis, 12 summits within this range were investigated in the canton of Grisons, Switzerland in 2004. Complete lists of vascular plant species consisting of 5–70 species were collected on each summit and the elevation of the uppermost occurrence of each species was recorded. These data were compared to historical records over 120 years in age. Within this time, vascular plant species richness increased by 11% per decade on summits in the alpine-nival ecotone. Despite this considerable change, a comparison with nival summits did not support the hypothesis that species richness increase at the alpine-nival ecotone is higher than in the nival belt. A general trend of upward migration in the range of several metres per decade could be observed. Anemochorous species were more often found to be migrating than zoochorous or autochorous species and migration was higher on calcareous than on siliceous bedrock. A comparison between the summits with the adjacent slopes in our study revealed that changes in species number could be used as an indicator for climate-induced changes—if at all—only for the narrow summit areas.     

Climate and landscape explain richness patterns depending on the type of species’ distribution data

Understanding the patterns of species richness and their environmental drivers, remains a central theme in ecological research and especially in the continental scales where many conservation decisions are made. Here, we analyzed the patterns of species richness from amphibians, reptiles and mammals at the EU level. We used two different data sources for each taxon: expert-drawn species range maps, and presence/absence atlases. As environmental drivers, we considered climate and land cover. Land cover is increasingly the focus of research, but there still is no consensus on how to classify land cover to distinct habitat classes, so we analyzed the CORINE land cover data with three different levels of thematic resolution (resolution of classification scheme ˗ less to more detailed). We found that the two types of species richness data explored in this study yielded different richness maps. Although, we expected expert-drawn range based estimates of species richness to exceed those from atlas data (due to the assumption that species are present in all locations throughout their region), we found that in many cases the opposite is true (the extreme case is the reptiles where more than half of the atlas based estimates were greater than the expert-drawn range based estimates). Also, we detected contrasting information on the richness drivers of biodiversity patterns depending on the dataset used. For atlas based richness estimates, landscape attributes played more important role than climate while for expert-drawn range based richness estimates climatic variables were more important (for the ectothermic amphibians and reptiles). Finally we found that the thematic resolution of the land cover classification scheme, also played a role in quantifying the effect of land cover diversity, with more detailed thematic resolution increasing the relative contribution of landscape attributes in predicting species richness.     

A survey method for assessing the richness of epiphytic lichens using growth forms

The species richness of epiphytic lichens is continuously decreasing by degradation and loss of habitat. Considering that taxonomic identification of all species is time and resource consuming, rapid assessment methods to extrapolate the total number of species are needed for practical conservation. This paper describes an alternative method using the correlation between lichens growth forms and species richness. The study was conducted in 406 forest stands located in Central Spain, covering a wide range of mediterranean-climate ecosystem regions, management intensity levels, canopy cover conditions, and tree sizes. The presence/absence of epiphytic lichens was determined in 6090 trees, which were dominated by oak species (Quercus ilex, Q. faginea, and Q. pyrenaica). In all type of forests, the diversity of growth forms was positively correlated with the total epiphytic lichen richness. In all cases, species richness increased in non-managed forest stands with dense canopies. Thus, we propose the use of lichen growth forms as a helpful surrogate of species richness to detect potentially conservation priority areas in the Mediterranean region.     

Empirical methodology for predicting changes in species range extension and richness associated with climate warming

Species richness and extent of geographical range for North American freshwater amphipods and crayfish are strongly correlated with mean annual absolute, or range of, temperature, respectively. Such spatially based relationships are shown to be useful for predicting the biological consequences arising through scenarios of temporal climate warming.     

Fertilization with nitrogen and phosphorus increases abundance of non-native species in Hawaiian montane forests

Weexamined the effects of fertilization on the diversity, abundance, and cover ofthe understory plant community of two montane wet forests in Hawaii. One siteoccupies a young substrate, where aboveground tree growth is limited bynitrogen(N), while the other site is on an older substrate, where aboveground treegrowth is limited by phosphorus (P). Both sites contained an on-going,long-termfactorial fertilization experiment in which plots were fertilized semi-annuallywith N, P, or N and P in combination. In each fertilization treatment, wemeasured density of species 0.5 m tall and percent cover ofspecies <0.5 m tall. Fertilization with N reducedspeciesrichness at the young, N-limited site, but none of the nutrient additionsaltered species richness at the older, P-limited site. Species diversity andevenness were not affected by fertilization at either site. At the site withlowN availability, plots fertilized with NP had higher densities of the non-nativeginger Hedychium gardnerianum, and at the site with lowP-availability, densities of the exotic shrub Rubusargutuswere higher in P- and NP-fertilized plots. Other effects included declines inmoss cover with fertilization at both sites, and reduced abundance of nativeseedlings in response to N and NP addition at the N-limited site. Continuedlong-term fertilization could lead to greater dominance of non-native speciesbyencouraging their growth at the expense of native species, which may sufferdecreased recruitment as fertilization and increased abundance of thenon-nativespecies may reduce suitable substrates for seedling establishment.     

Plant species diversity in abandoned coppice forests in a temperate deciduous forest area of central Japan

We investigated plant species diversity as it related to stand structure and landscape parameters in abandoned coppice forests in a temperate, deciduous forest area of central Japan, where Fagus crenata was originally dominant. The species occurring in the study plots were classified into habitat types based on a statistical analysis of their occurrence bias in particular habitats (e.g., primary forest, coniferous plantation) in the landscape studied. The relationships between stand structure, which reflected the gradient of management, and forest floor plant species diversity (H and J) and richness (number of species per unit area) were not significant. However, these factors did influence the forest floor plant composition of the different types of habitat. According to the multiple regression analysis, species diversity and the richness of forest floor plants was affected by landscape parameters rather than by stand structure. For trees, species richness was mainly affected by the relative dominance of F. crenata, which is one of the stand structure parameters that decreases with intensive management. This is probably because many of the tree species that are characteristic of coppice forests increase after F. crenata have been eliminated by management; these species are not dominant in the original forest, where they are suppressed by F. crenata, the shade-tolerant dominant species. The species diversity (H and J) of trees was positively correlated with some landscape parameters, including the road density around the study plot, which may be associated with the intensity of management activity. The number of disturbance-tolerant species increased with increasing road density. Stand structure mainly affected disturbance-intolerant forest floor plant species and disturbance-tolerant tree species. Thus, the species diversity responses differed between forest floor plants and trees. The impact of forest management on species diversity was more prominent for forest floor plants.     

Climate and vegetation structure determine plant diversity in Quercus ilex woodlands along an aridity and human-use gradient in Northern Algeria

We studied the influence of environmental factors relating to climate, soil and vegetation cover on total species richness, species richness of different life-forms and species composition of plant communities occurring in Quercus ilex woodlands, across a 450-km long transect in Northern Algeria constituting a gradient of aridity and human use. We sampled vegetation and collected environmental data in 81 10 m × 10 m plots in five zones representing the largest Q. ilex woodlands throughout the study area, analysing them within an a priori hypothesis framework with the use of Path Analysis. Changes in plant diversity were mainly influenced by environmental factors related to precipitation and temperature regimes, as well as by total plant cover. In particular, changes in species composition were determined by factors associated with the temperature regime through their influence on both woody and annual herbaceous plant richness, and by factors related to the precipitation regime through their influence on perennial herbaceous plant richness, likely due to the differential tolerances of these functional groups to cold and water stress. Our results emphasize the importance of differences in environmental adaptability of the most important life-forms with regard to explaining compositional change (beta diversity) along aridity gradients, and the mediator role of total plant cover in relation to the effects of soil conditions on plant diversity.     

南岭国家级自然保护区不同保护条件下林分的组成和立木结构

研究了在南岭国家级自然保护区中不同程度的保护条件下(试验区中的群落Ⅰ、缓冲区中的群落Ⅱ、核心区中的群落Ⅲ)3种群落类型的组成和立木结构.结果表明,3种群落的区系成分相似,都是以泛热带分布、热带亚洲(印度-马来西亚)分布、东哑和北美洲间断分布为主.群落Ⅰ的优势度在3种群落中最为明显.经F检验表明3种群落的丰富度和立木胸径都有极显著差异(P<0.001).受保护程度最低的群落Ⅰ的丰富度和平均胸径都最小,中等保护程度的群落Ⅱ的平均立木胸径和受保护程度最高的群落Ⅲ在丰富度和区系成分上表现出优势.频繁的人类活动的干扰对群落的丰富度、结构和区系成分的负面影响是明显的,但并非保护程度越高,群落的组成和结构越好.自然保护区的管理必须考虑到该地区的可持续性,结合当地的自然社会经济条件,控制好人为干扰的程度,以维持林分群落较高的丰富度和高大的乔木,禁止对森林造成破坏的人为干扰.     

中国跳鼠总科物种系统发育与分布格局

中国分布有跳鼠总科(Dipodoidea)动物3科12属22种,是世界上跳鼠总科物种丰富度最高的国家之一.近年来,随着新种的发现和分类地位的修正,我国跳鼠总科物种的系统发育关系和分布格局也亟待更新.本文通过GenBank下载12个特定基因,串联构建基因矩阵,以贝叶斯法和最大似然法重建22个物种的系统发育树,明确了我国跳...