Study on Plant Species Composition and Richness of the Mountain Coniferous Forests in Xinjiang

Decline of grassland diversity throughout Europe within the last decades is threatening biological diversity and is a major conservation problem. There is an urgent need to determine the underlying factors that control vascular plant species richness and composition in managed grasslands. In this study, 117 grasslands were sampled using standardised methods. Explanatory variables were recorded for each grassland site, reflecting the local field management, site-specific environmental conditions and large-scale spatial trends. Using variation partitioning methods, we determined the pure and shared effects of these three sets of explanatory variables on the plant species richness and composition in grasslands. Most of the explained variation in plant species richness was related to the joint effect of local field management and environmental variables. However, the applied variation partitioning approach revealed that the pure effect of spatial variables contributed relatively little to explaining variation in both the plant species richness and species composition. The largest fractions of explained variation in plant species composition were accounted for by the pure effects of environmental and local field management variables. Moreover, the results revealed that the main mechanisms by which these sets of explanatory variables affect plant species vary according to the type of management regime under study. From our findings we could conclude that particularly a reduction of nitrogen fertilisation on meadows and grazing at a low stocking rate on pastures can help to conserve biodiversity.

The present study assessed the impact of invasive alien species on plant species composition, richness, and diversity in the lower montane forest of Kilimanjaro National Park. The study area was categorized into four sites: the first three dominated by non-native species, namely Black Wattle (Acacia mearnsii), Mexican weeping pine (Pinus patula), and Eucalyptus (Eucalyptus spp.), and the fourth zone comprised natural forests. Sixty plots, each measuring 20 m × 50 m, were established at each site for vegetation sampling. A total of 168 plant species representing 135 genera and 64 families were identified and recorded from the study area. The highest plant species diversity was recorded in the natural forest with a mean plant species number of 13.8 ± 1.7, followed by Eucalyptus spp. A. mearnsii, and P. patula with 10.3 ± 1.2, 10.13 ± 1.1, and 7.33 ± 1.1, respectively. The plant species richness was significantly higher in the natural forest than in the areas invaded with non-native plant species (p < .05). Natural forest had the highest tree density of native trees with 774 ± 111 stems/ha and the lowest was observed in the P. patula site with a mean density of 12.7 ± 6.9. The reduction in plant species diversity and density in areas invaded with invasive alien species highlights the negative impact these species have on native plant communities. Sustainable forest management focusing on the protection of natural forests, the control of invasive species, and forest enrichment is highly recommended.

Large mammals, such as hippopotamuses (Hippopotamus amphibius), can significantly alter the landscape, vegetation composition, and structure in savannas through their grazing habits and ecosystem engineering effects, especially around rivers. However, livestock grazing can strongly change these effects, as seen in the Kenyan Maasai Mara Ecosystem. In this region, the increasing intensity of livestock grazing along local rivers, resulting from the transition of Maasai pastoralists from a semi-nomadic lifestyle to one based on pastoral ranches near the Maasai Mara National Reserve, may alter the impact of hippo grazing on riparian vegetation. We investigated the differences in vegetation structure, plant species richness and composition between landscapes predominantly grazed by hippopotami and livestock. We studied 25 transects, each measuring 5 km and having 13 sampling plots of 10 × 10 m2 located at varying distances from rivers in the reserve (n = 16) and pastoral ranches (n = 9). We measured the height and estimated the percent cover of grasses, forbs, shrubs, and bare ground, as well as plant species composition and richness and grazing intensity. Our results show that the riverine areas were more intensely and homogeneously grazed in the pastoral ranches than in the reserve, and in the dry than in the wet season in both landscapes. In addition, grazing intensity decreased with distance from rivers in the reserve in both seasons, but only in the wet season in the pastoral ranches. The mean plant species richness was similar in both landscapes and decreased linearly with distance from rivers, but varied with grazing intensity due to differences in forb and shrub species. However, plant species composition differed significantly between the reserve and the pastoral ranches. Furthermore, species similarity indices declined with increasing distance from water. These results suggest that the effects of livestock and hippo grazing intensity on vegetation structure and spatial heterogeneity interact, and vary with landscape and season. While both hippopotamus and livestock grazing can modify riparian vegetation, livestock grazing impact on plant species composition, vegetation structure, and spatial heterogeneity appears to be more persistent, declining less rapidly with increasing distance from water. Consequently, hippo and livestock differentially impact landscape heterogeneity.

Global warming has been strongly accelerating in the last decades. Climate models tell us that this trend will continue in the future, accompanied by a marked decline in precipitation in Southern Europe, whereas the Alps will likely receive more winter and less summer precipitation. Climate factors and additionally nitrogen deposition and land-use changes have been identified as global change factors posing threats on high-mountain biodiversity, ecosystem stability and services. On the other hand, the characteristic micro-topographic variability of high mountain ecosystems may buffer them against global change impacts. Monitoring data from European mountain peaks show that changes in biodiversity patterns are closely related to rising temperatures. However, the effects of climate change on plant biodiversity differ significantly between temperate and Mediterranean biomes with species richness increases synchronously with warming in the former and richness decreases in the latter. The MediAlps project aimed at disentangling anthropogenic and natural factors underlying differential changes in plant species composition and richness observed on mountain summits in the European Alps and the Mediterranean biome at the local and regional spatial scale. Changes in plant species richness and composition and present land-use impact based on systematic field observations were recorded on long-term monitoring plots on 23 summits. Soil temperature, water potential and local dry nitrogen deposition were measured in situ. Topographic parameters were recorded with photogrammetric methods. At the regional level, climate data and regional nitrogen deposition data from online resources (CHELSA, EMEP) were used and past land-use impact was assessed via guideline-aided semi-structured interviews. (Generalized) linear mixed-effects models and structural equation models (SEM) were employed to assess the impact of these drivers on biodiversity changes. Furthermore, spatio-temporal analyses based on satellite images were conducted. Climate change is and will probably continue to be the main driver of plant biodiversity, species composition and their changes on mountain summits in both biomes. However, there are biome-specific differences with precipitation playing an important role in the Mediterranean biome in addition to temperature, which clearly is the most important single factor in the temperate biome. These changes will likely lead to a further thermophilisation in both biomes. The upwards movement of species from lower elevations will likely also result in a biotic homogenization of the vegetation, exacerbated by the decline of high-elevation endemic species. Species richness will likely continue to increase in the temperate biome until the “pay-off” of extinction debts or threshold effects of population size on extinction risks set in. With decreasing precipitation species richness in the Mediterranean biome will probably decline in the long run, too. Nevertheless, other anthropogenic drivers have to be considered as well, although their influence is arguably much smaller than that of climate variables, namely nitrogen deposition with a negative influence on species richness change in the temperate biome and present land-use with a positive one in the Mediterranean biome. In addition to MediAlps’ main focus on comparing multiple anthropogenic ecological drivers in the Alps with the Mediterranean mountains, the project substantially contributed to a spatially larger scaled long-term observation effort in the frame of the GLORIA (Global Observation Research Initiative in Alpine Environments) program.

QuestionDo the effects of fire regimes on plant species richness and composition differ among floristically similar vegetation types?LocationBooderee National Park, south‐eastern Australia.MethodsWe completed floristic surveys of 87 sites in Sydney Coastal dry sclerophyll vegetation, where fire history records have been maintained for over 55 years. We tested for associations between different aspects of the recent fire history and plant species richness and composition, and whether these relationships were consistent among structurally defined forest, woodland and heath vegetation types.ResultsThe relationship between fire regime variables and plant species richness and composition differed among vegetation types, despite the three vegetation types having similar species pools. Fire frequency was positively related to species richness in woodland, negatively related to species richness in heath, and unrelated to species richness in forest. These different relationships were explained by differences in the associations between fire history and species traits among vegetation types. The negative relationship between fire frequency and species richness in heath vegetation was underpinned by reduced occurrence of resprouting species at high fire frequency sites (more than four fires in 55 years). However, in forest and woodland vegetation, resprouting species were not negatively associated with fire frequency.ConclusionsWe hypothesize that differing relationships among vegetation types were underpinned by differences in fire behaviour, and/or biotic and abiotic conditions, leading to differences in plant species mortality and post‐fire recovery among vegetation types. Our findings suggest that even when there is a high proportion of shared species between vegetation types, fires can have very different effects on vegetation communities, depending on the structural vegetation type. Both research and management of fire regimes may therefore benefit from considering vegetation types as separate management units.

Knowledge on the spatial distribution of plant species richness and its associated factors is crucial for addressing several ecological problems. Climate factors have long been used to explain species richness patterns across space and time. In this study, we investigated how water and energy variables shape species richness patterns on the alpine Tibetan plateau. An empirical study involving 800 plots of size 1 m2 on 80 different sites was conducted across two transects, covering the arid and semi‐arid alpine region of the western part of the Tibetan plateau to explore plant species composition and richness in relation to climatic factors at a regional scale. We performed detrended correspondence analysis and generalized linear models to explore the effect of energy and water variables on species composition and species richness, respectively. We used a generalized linear mixed model to investigate the interactive effect of energy variables and water variables on species richness. We found that both energy variables and water variables significantly influenced species richness and composition on the alpine Tibetan plateau and supported the water–energy dynamics (WED) hypothesis. Specificall, plant species richness increased with greater liquid water availability. However, it exhibited a unimodal relationship with potential evapotranspiration. Our results also showed that precipitation played a more substantial role in the model than potential evapotranspiration, but their interaction strengthened the model. In conclusion, this study highlights the dominant role of precipitation in explaining species composition and richness patterns on the alpine Tibetan plateau and suggests conducting research on additional environmental factors affecting water availability in this region.

To examine effects of local environmental conditions on the vegetation, measurements on the microhabitat level are highly relevant. Unlike most soil chemical variables, soil moisture is rarely considered in studies investigating the impact of local factors on plant species composition. Here, we conducted soil moisture measurements with TMS4 sensors over a two-month period in 25 deciduous forest plots in northern Germany, performed site-specific moisture calibrations and studied the quantitative effect of soil properties on the relationship between the TMS4 signal and gravimetric soil moisture. Moreover, we investigated the effect of measured microhabitat conditions (light availability, soil variables including soil moisture) on plant species richness and composition. We found that soil carbon significantly influenced the relationship between the TMS4 raw signal and gravimetric soil moisture. The number of herb layer species and ancient woodland indicators (AWI) increased with increasing soil moisture. For the herb layer, soil moisture and soil C/N ratio had an interactive effect: species richness increased more steeply with increasing soil moisture in plots with a low C/N ratio. AWI species richness was significantly higher in plots with a low C/N ratio. Herb layer species composition was shaped by two main gradients, reflecting (1) variation in C/N ratio and pH and (2) variation in soil moisture, other soil variables and light availability. Our findings indicate that soil carbon, a frequently measured variable in vegetation studies, could, with sufficiently good calibrations, be directly used to translate sensor raw signals into reliable soil moisture values for predicting plant species occurrence.

Agroforestry practices (AFPs) have the potential to improve species composition and the ecological integrity of various landscapes. However, site-specific studies on the role of AFPs in enhancing plant species composition, richness, and diversity are scarce. This study aimed to determine variations in useful plant species composition and diversity across five agroforestry practices: Boundary Planting Agroforestry Practice (BAP), Multiple Woody Perennial Agroforestry Practice (MWPAP), Agrosilvopastoral Practice (ASP), Coffee Intercropped Agroforestry Practice (CIAP), and Mixed Intercropping Agroforestry Practice (MAP). A 10 &times; 10 m plot size was used to assess plant species composition and richness. Four plant species life forms were identified: trees, shrubs, climbers, and herbs. Variations in plant species composition and diversity among the AFPs were statistically analysed using ANOVA in R software, while correlations between plant life forms were determined using Pearson product-moment analysis. A total of 58 tree species (61.6%), 20 shrub species (21.3%), 10 climber species (10.5%), and 6 herb species (6.6%) belonging to 40 families and 72 genera were identified. Fabaceae and Euphorbiaceae were the most represented families, with 13 and 9 species, respectively. The highest mean species richness for trees (39), shrubs (19), and herbs (6) was recorded in ASP, while the highest mean climber species richness (10) was observed in CIAP. MAP exhibited the highest mean diversity for tree and herb species, whereas shrub and climber species diversity was highest in MWPAP and CIAP, respectively. Tree, shrub, climber, and herb species richness and diversity differed significantly (p &lt; 0.001) across all AFPs. A significant positive correlation was observed between the species richness in trees, shrubs, and climbers in all practices (p &lt; 0.05). The ASP and MAP demonstrated higher potential for supporting plant species richness and diversity, as well as a greater number of plant life forms. These two systems should be prioritized for their ecological and socio-economic benefits. &nbsp; Key words: Plant life forms, agroforestry practices, useful, species diversity, species richness.

Anthropogenic warming and land‐use change are expected to accelerate global soil organic carbon (SOC) losses and change plant species composition and richness. However, how changes in plant composition and species richness mediate SOC responses to climate warming and land‐use change remains poorly understood. Using data from a 7‐year warming and clipping field experiment in an alpine meadow on the Qinghai–Tibetan Plateau, we examined the direct effects of warming and clipping on SOC storage versus their indirect effects mediated by plant functional type and species richness. We found that warming significantly increased SOC storage by 8.1% and clipping decreased it by 6.4%, which was closely correlated with the corresponding response of below‐ground net primary productivity (BNPP). We also found a negative correlation between SOC storage and species richness, which was ascribed to the increased BNPP via enhancing the dominance of grasses and decreasing species richness under warming. The lower SOC storage under clipping was caused by the clipping‐induced decrease in BNPP via weakening the dominance of grasses and increasing species richness. Our findings highlight that the SOC storage in this alpine meadow under climate warming and clipping was primarily governed by BNPP changes, which was mediated by changes in the dominance of grasses and species richness. Overall, our study demonstrates that shifting to the dominance of grasses and changing species richness would benefit soil C sequestration under climate warming, but this positive effect would be dampened by grazing or hay harvest. Read the free Plain Language Summary for this article on the Journal blog.

Plant species richness and composition are influenced by complex interactions between biotic and abiotic factors that operate on different spatial scales. Since spatial scales vary continuously in nature, it is expected that multiple factors simultaneously affect species richness and composition at an intermediate spatial scale (i.e., the mesoscale landscape level). Previous studies have shown that local topography and elevation are important factors for shaping intermediate spatial scale plant species richness; however, the relative importance of these factors has rarely been examined. Here, we used spatially explicit woody plant data to examine the factors that characterize the spatial pattern of primary evergreen forest biodiversity at the intermediate spatial scale. We found that the spatial pattern of species diversity in a predominantly warm temperate evergreen forest at the landscape level is mainly characterized by shifts in species composition along the elevation gradient. Our study also found that compositional shift along the elevational gradient was mainly caused by habitat specialization among congeneric species, suggesting that niche partitioning among closely-related species is a fundamentally important feature of the intermediate spatial scale species richness pattern. Furthermore, we found that specialization in a habitat of closely-related species can be established even within a limited environmental gradient. This suggests that biotic interactions among closely-related species may be an important factor driving habitat specialization, and biotic interactions may play an important role in shaping landscape-scale biodiversity patterns.

The present study aims to investigate the effect of soil physical and chemical variables on the species richness and the floristic composition in four sites (Alwaz, Alqan, Sharma and Zetah) of Tabuk region in the Northwestern part of Arabian Peninsula. Only organic matter (OM), pH and calcium (Ca) showed significant differences (P &lt; 0.05) amongst the four studied sites. Only magnesium and sodium were selected in the forward regression model and showed to be strong drivers of species richness of plants in Tabuk region (Adj-R2 = 0.438, F2,13 = 6.85, P = 0.009). The multivariate analysis of canonical correspondence analysis (CCA ) was applied to reveal the effect of the physical and chemical variables on the species composition of the plants. The CCA classifies the plant species into three groups based on their preference to the environmental variables. The first group of plant species (Group 1) is characterised by positive preference to the chloride (Cl) and negative relationship with OM and pH. The second group (Group 2) is positively correlated with most of the soil variables such as OM, calcium (Ca), potassium (K), bicarbonate (HCO3), electrical conductivity (EC), sulphate (SO4) and sodium (Na). The third group (Group 3) has positive relationship with carbonate (CO3) and negative relationship with EC and magnesium (Mg). The chloride, sodium, sulphate, EC and carbonate are the main environmental factors influencing the plant species composition in Tabuk region. The cluster analysis based on the Euclidian measure shows that Alqan and Zetah have closer species composition compared to Sharma.

AimThe impact of fragmentation on a eucalypt forest was investigated by examining the effects of fragment size, time since fragmentation, degree of anthropogenic disturbance to fragment interiors, and time since fire, on native and exotic plant species richness per unit area.LocationTwo areas of dry open‐forest were studied on the central coast of New South Wales in south‐eastern Australia. Fifty forest fragments were located at Tomago, an area progressively fragmented over the last 60 years, most recently by clearing for sand‐mining. Also at Tomago were six very large blocks of forest that were used as reference sites. The second area at Myall Lakes National Park (50 km north of Tomago) had four very large areas of intact forest that were also used as reference sites.MethodsFragments were allocated into (1) three size classes: small (&lt;1 ha), medium (1 to &lt;10 ha) and large (10 to &lt;100 ha); (2) two classes of age since fragmentation: young (up to 10 years) and old (10 years or more); (3) two classes of disturbance (minor, major) based on the degree and extent of human‐induced disturbance to the fragment interior; and (4) two classes of time since fire (between 5 and 6 years; 10 years or more). Reference sites belonged to a very large size class (&gt;100 ha). Mean plant species richness per 25 m2 area was determined for each fragment and analysed separately for native and exotic species.ResultsThe most significant effects observed resulted from anthropogenic disturbance. In fragments with major disturbance, native species richness per unit area was significantly reduced in small‐sized young and medium‐sized old fragments. A significant increase was also observed for exotic species richness in fragments with major disturbance. With minor disturbance, native species richness in small fragments declined significantly with time since fragmentation, in contrast to medium and large fragments. Among recently created fragments, those recently burned had significantly more native species per unit area than those burned 10 or more years ago.Main conclusionsAnthropogenic disturbance coupled with fragmentation had a stronger and more immediate effect in reducing native species richness and increasing exotic species richness than did fragmentation alone. In the absence of major disturbance, small fragments had fewer native species than larger size classes, but only after 10 or more years since fragmentation, confirming the importance of controlling for age of fragments when examining species–area relationships. This study has not tested whether differences in area were the direct cause of this loss of species over time; other factors that are correlated with area (such as edge effects) may also be involved. The increase in native species richness following fire was consistent with other studies of fire in unfragmented eucalypt forest. This study thus shows that in addition to the factors emphasized in classical island biogeography models, fragment age, disturbance and fire history are important in explaining species richness in fragmented eucalypt forests.

Ant and plant species richness in relation to grazing, fertilisation and topography

Summary&#13;\nConflicting evidence exists with respect to the putative effect of forest management on plant species diversity. Various published studies have concluded that primeval forests are not that species-rich and that forest management may increase species richness in certain cases. Yet, it appears that such conclusions have often been drawn from the comparison of production forests to reference forests with a management legacy, i.e. stands in which forest management ceased only a few decades ago. &#13;\nThe present study explores the impact of forest management on the diversity of vascular plants, bryophytes and lichens in Fagus sylvatica production forests in comparison to untouched primeval forests without any detectable management legacy in the western Carpathian Mountains, eastern Slovakia. This study in three production and three primeval forests also assesses the role of natural forest dynamics for species diversity and highlights the importance of height in the crown for the diversity and composition of epiphytic bryophyte and lichen communities. &#13;\nThe results demonstrate that forest management-related disturbances do not increase landscape-level vascular plant species richness in comparison to untouched primeval forests. Even though mean plot-level diversity (alpha-diversity) was higher in the production forests, rarefaction/extrapolation showed a similarly high landscape-level vascular plant diversity (gamma-diversity) in the primeval forests. Comparing the gamma-diversity of vascular plants in the initial, optimal and terminal stages with the production forests showed no significant differences between the three stages, and to the managed stands. In contrast, mean plot-level species richness of epiphytic cryptogams tended to be higher in the primeval forests. Rarefaction/extrapolation revealed an about 30 and 100 % higher bryophyte and lichen species richness (gamma-diversity) in the primeval forests, respectively. Comparing the epiphyte species diversity of the three stages with the production forests provided a significantly higher species richness in any stage of the forest development. Species turnover between plots (beta-diversity) was in the three systematic groups generally higher in the primeval forests, indicating a greater habitat heterogeneity and spatially more variable species composition of the communities. In addition to habitat diversity, habitat continuity is playing an essential role for maintaining a high higher species richness in the primeval forests. This is visible when comparing the epiphyte species richness on stems of a given stem diameter class between production und primeval forests. Epiphytic bryophyte and lichen diversity per stem size class was significantly higher in the primeval forests. This was attributed to the fact that trees with large diameters in the production stands rarely were older than 100 years, whereas the maximum age of large-sized beeches in the primeval forest was over 400 years. &#13;\nNatural forest dynamics affected the composition, but not the species richness, of the forest floor vegetation. Certain species showed a strong preference for either the initial, optimal or terminal stage, reflecting a high species turnover in primeval forests. Vascular species richness, however, did not differ between the three stages. In contrast to vascular plants, bryophyte and lichen species composition and richness on living trees and standing deadwood was strongly affected by natural forest dynamics. In general, epiphyte diversity increased from the initial to the terminal stage. Several bryophytes and lichens showed a distinct preference for one of the three stages, showing a close association with the ageing of trees and diameter growth. Of the detected bryophytes and lichens, 50 and 22 %, respectively, were significantly associated with large-diameter stems (≥70 cm). Bryophytes and lichens on lying deadwood were not affected by natural forest development, as no stage differences in the species richness were detectable.&#13;\nThe analysis of the epiphytic bryophyte and lichen vegetation from the tree base to the crown demonstrated that sampling only the lowermost 2 m results in a marked underestimation of total epiphyte species richness in temperate broadleaf forests. More specifically, about 10 % of the overall bryophyte and 48 % of the lichen species pool would have been missed. The vertical change in the epiphytic bryophyte and lichen flora reflects the increase in light intensity, decrease in atmospheric moisture and the growing input of acids and nitrogen compounds when moving from the trunk base to the canopy. The vertical change in microclimate and microsite conditions also leads to distinct compositional variations of both studied groups along the height gradient. &#13;\nThis study clearly shows that forest management markedly reduces overall plant diversity and strongly impacts on the species composition in managed forests in comparison to untouched primeval forests. The higher plant species richness in primeval forests is mainly due to the much longer habitat continuity and greater habitat heterogeneity in horizontal and vertical direction, as generated by the processes of natural forest development. The disappearance of the terminal stage of forest development and a principal reduction in forest structural heterogeneity in production forests promote the loss of many plant species with close association to primeval forest attributes. Protecting the last remaining temperate primeval forests is thus an important element of a global strategy to conserve the biodiversity on earth.

Terrestrial plant community responses to herbivory depend on resource availability, but the separate influences of different resources are difficult to study because they often correlate across natural environmental gradients. We studied the effects of excluding ungulate herbivores on plant species richness and composition, as well as available soil nitrogen (N) and phosphorus (P), across eight grassland sites in Serengeti National Park (SNP), Tanzania. These sites varied independently in rainfall and available soil N and P. Excluding herbivores decreased plant species richness at all sites and by an average of 5.4 species across all plots. Although plant species richness was a unimodal function of rainfall in both grazed and ungrazed plots, fences caused a greater decrease in plant species richness at sites of intermediate rainfall compared to sites of high or low rainfall. In terms of the relative or proportional decreases in plant species richness, excluding herbivores caused the strongest relative decreases at lower rainfall and where exclusion of herbivores increased available soil P. Herbivore exclusion increased among-plot heterogeneity in species composition but decreased coexistence of congeneric grasses. Compositional similarity between grazed and ungrazed treatments decreased with increasing rainfall due to greater forb richness in exclosures and greater sedge richness outside exclosures and was not related to effects of excluding herbivores on soil nutrients. Our results show that plant resources, especially water and P, appear to modulate the effects of herbivores on tropical grassland plant diversity and composition. We show that herbivore effects on soil P may be an important and previously unappreciated mechanism by which herbivores influence plant diversity, at least in tropical grasslands.