Forest/environment relationships in Yosemite National Park,California, USA

Forest compositional patterns in Yosemite National Park, California, were related to environmental factors through numerical classification of forest types, arrangement of forest types along elevational and topographic gradients, and development of regression models relating basal area of common tree species to environmental variables. The eight forest types are differentiated primarily by elevation zone and secondarily by topographic setting. Lower montane forests (1200–1900 m) were divided into the Abies concolor/Calocedrus type occurring primarily on mesic sites and the Pinus ponderosa/Calocedrus type predominantly on xeric sites. Upper montane forests (1900–2500 m) included the Abies concolor/Abies magnifica type on mesic sites, the Abies magnifica/Pinus type on somewhat more xeric sites, and Juniperus occidentalis/Pinus jeffreyi woodlands on granitic domes. Subalpine forests (2500–3300 m) embraced three types: Tsuga mertensiana/Pinus forests on mesic sites, monotypic Pinus contorta forests on drier sites, and Pinus albicaulis/Pinus contorta groves at treeline. Regression models consistently included elevation and soil magnesium content as explanatory variables of species basal area totals. The two Abies spp. were negatively correlated with soil magnesium levels, whereas other montane species (e.g. Calocedrus decurrens, Pinus lambertiana, and Pinus ponderosa) exhibited positive correlation with soil magnesium. Topography and soil physical properties were only infrequently incorporated into species regression models.Abbreviations DBH= diameter at breast height (1.4 m) - DCA= detrended correspondence analysis - TWINSPAN= two-way indicator species analysis     

Ground Layer Plant Species Turnover and Beta Diversity in Southern-European Old-Growth Forests

Different assembly processes may simultaneously affect local-scale variation of species composition in temperate old-growth forests. Ground layer species diversity reflects chance colonization and persistence of low-dispersal species, as well as fine-scale environmental heterogeneity. The latter depends on both purely abiotic factors, such as soil properties and topography, and factors primarily determined by overstorey structure, such as light availability. Understanding the degree to which plant diversity in old-growth forests is associated with structural heterogeneity and/or to dispersal limitation will help assessing the effectiveness of silvicultural practices that recreate old-growth patterns and structures for the conservation or restoration of plant diversity. We used a nested sampling design to assess fine-scale species turnover, i.e. the proportion of species composition that changes among sampling units, across 11 beech-dominated old-growth forests in Southern Europe. For each stand, we also measured a wide range of environmental and structural variables that might explain ground layer species turnover. Our aim was to quantify the relative importance of dispersal limitation in comparison to that of stand structural heterogeneity while controlling for other sources of environmental heterogeneity. For this purpose, we used multiple regression on distance matrices at the within-stand extent, and mixed effect models at the extent of the whole dataset. Species turnover was best predicted by structural and environmental heterogeneity, especially by differences in light availability and in topsoil nutrient concentration and texture. Spatial distances were significant only in four out of eleven stands with a relatively low explanatory power. This suggests that structural heterogeneity is a more important driver of local-scale ground layer species turnover than dispersal limitation in southern European old-growth beech forests.     

Structures determining bryophyte species richness in a managed forest landscape in boreo-nemoral Europe

Forest patches with high biological value are protected as woodland key habitats (WKH), which are identified by the presence of forest structures and indicator species. However, management for conservation needs to consider also managed forests as habitats for species. In this respect, there is a need to set quantitative targets for species and structures at different landscape scales. Due to non-intensive methods of forest management used prior to 1940 in Latvia, it might be expected that large areas of forest have developed structures that can support many species characteristic of natural forests. The aim of the study was to create a model that best described the richness of bryophyte species that are characteristic of natural forests, using forest structures as explanatory factors. The structures and bryophyte communities on living trees and coarse woody debris (CWD) were described in plots along transects blindly placed in areas dominated by State forests under commercial management. Explanatory variables related to tree species composition and tree size explained 54% of the variation in WKH indicator species richness on living trees. The best explanatory factors were maximum diameter of deciduous tree species and CWD. Low richness of total bryophyte and indicator species was found on dead wood, and the amount of variation in bryophyte species richness on CWD explained by explanatory variables was low. The study indicates the importance of deciduous tree substrate in managed forests in maintaining the spatial continuity of epiphytic species diversity. However, the forests in the managed forest landscape did not support high diversity of epixylic species, even in the WKHs, due to low diversity of suitable dead wood substrate.     

Patterns of climber distribution in the temperate forests of the Americas

Aims and Methods We propose a standard protocol at the landscape to continental scale for examining to what extent the range of ecological conditions found in temperate latitudes explains the variations in climber species richness and traits. The protocol was tested in forests of the two Americas. The data set included 151 climber species. We selected four categorical traits and grouped these species into six clusters with regard to these traits. Floristic records of American forests were first gathered into alliances, second combined with bioclimatic indices (rainfall, temperature, continentality). We obtained a total of 59 vegetational units in which we calculated values of climber species richness and proportion of clusters. Vegetational units were ultimately gathered into five forest formations (characterized by leaf longevity). Wetlands and uplands were considered separately.Important findings Our results emphasize clear trends in large-scale patterns of climber distribution, independently of taxonomy. Climber species richness (in particular woody climbers) peaks in moist and warm upland forests with oceanic climates, and where conifers are rare. In flooded areas, climber richness is also very high and peaks in seasonally flooded large floodplains. In ecological conditions of frost, dryness or lack of nutrients, climber species richness, abundance and trait diversity decline, resulting in the dominance of small, twining and deciduous life traits.     

Moderate disturbances accelerate forest transition dynamics under climate change in the temperate–boreal ecotone of eastern North America

Several temperate tree species are expected to migrate northward and colonize boreal forests in response to climate change. Tree migrations could lead to transitions in forest types, but these could be influenced by several non‐climatic factors, such as disturbances and soil conditions. We analysed over 10,000 forest inventory plots, sampled from 1970 to 2018 in meridional Québec, Canada, to identify what environmental conditions promote or prevent regional‐scale forest transitions. We used a continuous‐time multi‐state Markov model to quantify the probabilities of transitions between forest states (temperate, boreal, mixed, pioneer) as a function of climate (mean temperature and climate moisture index during the growing season), soil conditions (pH and drainage) and disturbances (severity levels of natural disturbances and logging). We further investigate how different disturbance types and severities impact forests' short‐term transient dynamics and long‐term equilibrium using properties of Markov transition matrices. The most common transitions observed during the study period were from mixed to temperate states, as well as from pioneer to boreal forests. In our study, transitions were mainly driven by natural and anthropogenic disturbances and secondarily by climate, whereas soil characteristics exerted relatively minor constraints. While major disturbances only promoted transitions to the pioneer state, moderate disturbances increased the probability of transition from mixed to temperate states. Long‐term projections of our model under the current environmental conditions indicate that moderate disturbances would promote a northward shift of the temperate forest. Moreover, disturbances reduced turnover and convergence time for all transitions, thereby accelerating forest dynamics. Contrary to our expectation, mixed to temperate transitions were not driven by temperate tree recruitment but by mortality and growth. Overall, our results suggest that moderate disturbances could catalyse rapid forest transitions and accelerate broad‐scale biome shifts.     

Climate more important than soils for predicting forest biomass at the continental scale

Above-ground biomass in forests is critical to the global carbon cycle as it stores and sequesters carbon from the atmosphere. Climate change will disrupt the carbon cycle hence understanding how climate and other abiotic variables determine forest biomass at broad spatial scales is important for validating and constraining Earth System models and predicting the impacts of climate change on forest carbon stores. We examined the importance of climate and soil variables to explaining above-ground biomass distribution across the Australian continent using publicly available biomass data from 3130 mature forest sites, in 6 broad ecoregions, encompassing tropical, subtropical and temperate biomes. We used the Random Forest algorithm to test the explanatory power of 14 abiotic variables (8 climate, 6 soil) and to identify the best-performing models based on climate-only, soil-only and climate plus soil. The best performing models explained ~50% of the variation (climate-only: R² = 0.47 ± 0.04, and climate plus soils: R² = 0.49 ± 0.04). Mean temperature of the driest quarter was the most important climate variable, and bulk density was the most important soil variable. Climate variables were consistently more important than soil variables in combined models, and model predictive performance was not substantively improved by the inclusion of soil variables. This result was also achieved when the analysis was repeated at the ecoregion scale. Predicted forest above-ground biomass ranged from 18 to 1066 Mg ha⁻¹, often under-predicting measured above-ground biomass, which ranged from 7 to 1500 Mg ha⁻¹. This suggested that other non-climate, non-edaphic variables impose a substantial influence on forest above-ground biomass, particularly in the high biomass range. We conclude that climate is a strong predictor of above-ground biomass at broad spatial scales and across large environmental gradients, yet to predict forest above-ground biomass distribution under future climates, other non-climatic factors must also be identified.     

The contribution of understory light availability and biotic neighborhood to seedling survival in secondary versus old-growth temperate forest

Seedling survival plays an important role in the maintenance of species diversity and forest dynamics. Although substantial gains have been made in understanding the factors driving patterns of seedling survival in forests, few studies have considered the simultaneous contribution of understory light availability and the local biotic neighborhood to seedling survival in temperate forests at different successional stages. Here, we used generalized linear mixed models to assess the relative importance of understory light availability and biotic neighborhood variables on seedling survival in secondary and old-growth temperate forest in north eastern China at two levels (community and guild). At the community level, biotic neighborhood effects on seedling survival were more important than understory light availability in both forests. In both the old-growth and secondary forests, conspecific basal area had a negative effect on seedling survival, consistent with negative conspecific density dependence. At guild levels, the relative importance of light and biotic neighborhood on seedling survival showed considerable variation among guilds in both forests. Available understory light tended to have positive effects on seedling survival for shrub and light-demanding species in the old-growth forest, but negative effects on survival of shade-tolerant seedlings in the secondary forest. For tree species and shade-tolerant species, the best fit models included neighborhood variables, but that was not the case for shrubs, light-demanding, or mid shade-tolerant species. Overall, our results demonstrate that the relative importance of understory light availability and biotic factors on seedling survival vary with species life-history strategy and forest successional stage.     

The influence of disturbance on driving carbon stocks and tree dynamics of riparian forests in Cerrado

Aims Riparian forests in the Brazilian Cerrado, also known as gallery forests, are very heterogeneous in structure, species composition and ecological features due to strong and abrupt variations of soil, hydrological and topographic properties. However, what are the variables driving forest carbon stock and productivity, mortality and recruitment in disturbed gallery forests?Methods We used 36 permanent plots data from a gallery forest in the Brazilian Cerrado. We investigated how tree community dynamics vary in a gallery forest on two contrasting disturbance levels—logged and non-logged—across a topographic gradient intrinsically related to differences in moisture conditions, edge effects, as well as soil fertility and texture.Important findings Soil variables were reduced into principal components and we used structural equation modelling to disentangle covarying variables. We also included carbon stocks as a determinant variable of dynamics rates. Logged forest had 50% higher productivity than non-logged forest and streamside forest had aboveground carbon stocks 70% higher than the forest edge. Both logging and natural disturbance drove variation in the carbon stocks which contributed to shaping productivity and recruitment rates. Distance from the river also drove mortality and carbon stock rates. Areas with high-carbon stocks favoured higher competition and lessened productivity and recruitment rates. Although soil fertility and texture are considered crucial components shaping forest dynamics, there was no clear influence of those variables on the present forest, probably because the strong effects of soil moisture, forest edge and disturbance disrupted the correlation between soil and forest dynamics.     

Tree species distribution in temperate forests is more influenced by soil than by climate

Knowledge of the ecological requirements determining tree species distributions is a precondition for sustainable forest management. At present, the abiotic requirements and the relative importance of the different abiotic factors are still unclear for many temperate tree species. We therefore investigated the relative importance of climatic and edaphic factors for the abundance of 12 temperate tree species along environmental gradients. Our investigations are based on data from 1,075 forest stands across Switzerland including the cold‐induced tree line of all studied species and the drought‐induced range boundaries of several species. Four climatic and four edaphic predictors represented the important growth factors temperature, water supply, nutrient availability, and soil aeration. The climatic predictors were derived from the meteorological network of MeteoSwiss, and the edaphic predictors were available from soil profiles. Species cover abundances were recorded in field surveys. The explanatory power of the predictors was assessed by variation partitioning analyses with generalized linear models. For six of the 12 species, edaphic predictors were more important than climatic predictors in shaping species distribution. Over all species, abundances depended mainly on nutrient availability, followed by temperature, water supply, and soil aeration. The often co‐occurring species responded similar to these growth factors. Drought turned out to be a determinant of the lower range boundary for some species. We conclude that over all 12 studied tree species, soil properties were more important than climate variables in shaping tree species distribution. The inclusion of appropriate soil variables in species distribution models allowed to better explain species' ecological niches. Moreover, our study revealed that the ecological requirements of tree species assessed in local field studies and in experiments are valid at larger scales across Switzerland.     

全球森林土壤微生物生物量碳氮磷化学计量的季节动态

土壤微生物生物量在森林生态系统中充当具有生物活性的养分积累和储存库。土壤微生物转化有机质为植物提供可利用养分, 与植物的相互作用维系着陆地生态系统的生态功能。同时, 土壤微生物也与植物争夺营养元素, 在季节交替过程和植物的生长周期中呈现出复杂的互利-竞争关系。综合全球数据对温带、亚热带和热带森林土壤微生物生物量碳(C)、氮(N)、磷(P)含量及其化学计量比值的季节动态进行分析, 发现温带和亚热带森林的土壤微生物生物量C、N、P含量均呈现夏季低、冬季高的格局。热带森林四季的土壤微生物生物量C、N、P含量都低于温带和亚热带森林, 且热带森林土壤微生物生物量C含量、N含量在秋季相对最低, 土壤微生物生物量P含量四季都相对恒定。温带森林的土壤微生物生物量C:N在春季显著高于其他两个森林类型; 热带森林的土壤微生物生物量C:N在秋季显著高于其他2个森林类型。温带森林土壤微生物生物量N:P和C:P在四季都保持相对恒定, 而热带森林土壤微生物生物量N:P和C:P在夏季高于其他3个季节。阔叶树的土壤微生物生物量C含量、N含量、N:P、C:P在四季都显著高于针叶树; 而针叶树的土壤微生物生物量P含量在四季都显著高于阔叶树。在春季和冬季时, 土壤微生物生物量C:N在阔叶树和针叶树之间都没有显著差异; 但是在夏季和秋季, 针叶树的土壤微生物生物量C:N显著高于阔叶树。对于土壤微生物生物量的变化来说, 森林类型是主要的显著影响因子, 季节不是显著影响因子, 暗示土壤微生物生物量的季节波动是随着植物其内在固有的周期变化而变化。植物和土壤微生物密切作用表现出来的对养分的不同步吸收是保留养分和维持生态功能的一种权衡机制。     

THE OCCURRENCE AND DISTRIBUTION OF ACRASIEAE IN FORESTS OF SUBTROPICAL AND TROPICAL AMERICA

Forests of the subtropical and tropical regions of North America harbor cellular slime molds not found in the soils of temperate deciduous forests investigated previously. However, most species found in the temperate forest are common in the tropics. Although the diversity of forms is greater in the soils of tropical forests the numbers of Acrasieae per unit of soil are comparable. Characteristic of tropical and subtropical forest soils are Acrasieae bearing crampon bases, of which four new species of Dictyostelium are presently known. Also present, but less frequently isolated, are two other new species of the genus Dictyostelium and two still undescribed species of the Guttulinaceae. Occasional isolates of D. purpureum and D. discoideum were found that produce macrocysts, which seem, also, to be confined to tropical and subtropical areas. Macro-cysts were previously known only in D. mucoroides and D. minutum isolated from temperate forest soils. The occurrence and distribution of Acrasieae in warm temperate desert and mesquite-scrub, in subtropical hammock, and in tropical thorn, deciduous, seasonal evergreen, rain, and cloud forests were investigated. Acrasieae were well represented in all of these forests except desert. The number of species and the total populations were largest in seasonal evergreen forests. The composition of the cellular slime mold populations and the dominant species within these populations could be related to the soil environment as expressed by the dominant vegetation.     

The effect of biodiversity on tree productivity: from temperate to boreal forests

Aim An important issue regarding biodiversity concerns its influence on ecosystem functioning. Experimental work has led to the proposal of mechanisms such as niche complementarity. However, few attempts have been made to confirm these in natural systems, especially in forests. Furthermore, one of the most interesting unresolved questions is whether the effects of complementarity on ecosystem functioning (EF) decrease in favour of competitive exclusions over an increasing productivity gradient. Using records from permanent forest plots, we asked the following questions. (1) Is tree productivity positively related to diversity? (2) Does the effect of diversity increase in less productive forests? (3) What metric of diversity (e.g. functional or phylogenetic diversity) better relates to tree productivity? Location Temperate, mixed and boreal forests of eastern Canada. Methods Over 12,000 permanent forest plots, from temperate to boreal forests, were used to test our hypotheses in two steps. (1) Stepwise regressions were used to identify the best explanatory variables for tree productivity. (2) The selected climatic and environmental variables, as well as density and biodiversity indices, were included in a structural equation model where links (paths) between covarying variables are made explicit, making structural equation modelling the best tool to explore such complicated causal networks. Results This is the first large‐scale demonstration of a strong, positive and significant effect of biodiversity on tree productivity with control for climatic and environmental conditions. Important differences were noted between the two forest biomes investigated. Main conclusions We show for the first time that complementarity may be less important in temperate forests growing in a more stable and productive environment where competitive exclusion is the most probable outcome of species interactions, whereas in the more stressful environment of boreal forests, beneficial interactions between species may be more important. The present work is also a framework for the analysis of large datasets in biodiversity–ecosystem functioning (B‐EF) research.     

Linking forest shade tolerance and soil moisture in North America

Increasing occurrence of droughts is a major environmental concern, however its consequences on forested ecosystems are not fully understood at the landscape level. Here we link the forest shade tolerance index to soil moisture in the North America using the U.S. and Quebec forest inventories. We report a significant decrease of shade tolerance index along the hydric–mesic–xeric soil transition in most of the area considered except three subtropical/tropical ecoregions of the Southeastern U.S. We conclude that droughts may alter forest succession, and in particular decrease the role of forest gap dynamics and dominance of the shade-tolerant species in mature forests.     

亚热带常绿阔叶林和暖温带落叶阔叶林叶片热值比较研究

植物干重热值(GCV)是衡量植物生命活动及组成成分的重要指标之一,反映了植物光合作用中固定太阳辐射的能力。利用氧弹量热仪测定了亚热带和暖温带两个典型森林生态系统常见的276种常见植物叶片的干重热值,探讨了亚热带和暖温带植物热值分布特征,以及不同生活型、乔木类型间植物热值的变化规律。实验结果发现:亚热带常绿阔叶林和暖温带落叶阔叶林叶片热值的平均值分别为17.83 k J/g(n=191)和17.21k J/g(n=85),整体表现为亚热带植物暖温带植物。不同地带性植被的植物叶片热值在不同生活型间表现出相似的规律,其中亚热带常绿阔叶林表现为:乔木(19.09 k J/g)灌木(17.87 k J/g)草本(16.65 k J/g);暖温带落叶阔叶林表现为:乔木(18.41 k J/g)灌木(17.94 k J/g)草本(16.53 k J/g);不同乔木类型间均呈现常绿乔木落叶乔木、针叶乔木阔叶乔木的趋势。落叶阔叶乔木表现为亚热带暖温带,而常绿针叶乔木则呈现亚热带暖温带的趋势。此外,我们对于两个分布区域内的4种针叶树种叶片热值进行了比较,发现华北落叶松(19.32 k J/g,暖温带)杉木(19.40 k J/g,亚热带)马尾松(19.82 k J/g,亚热带)油松(20.95 k J/g,暖温带)。亚热带常绿阔叶林和暖温带落叶阔叶林植物热值的特征及其变化规律,为森林生态系统的能量流动提供了理论基础。     

气候和林分类型对土壤团聚体有机碳的影响

该研究选择我国分布于亚热带、暖温带和寒温带的三个样点8种林分(包括阔叶林、混交林和针叶林)下表层0~20 cm的土壤为研究对象,利用干筛法进行大团聚体和微团聚体分级,测定了各团聚体组分的有机碳量和有机碳百分比,并分析他们与气候、植被和土壤环境变量之间的关系。结果表明:土壤大团聚体和微团聚体有机碳量都受到气候的显著影响,表现为土壤大团聚体和微团聚体有机碳量随年均温的增高而降低,经分析这与低温抑制土壤微生物分解活动有关。土壤团聚体有机碳百分比受到林分类型的影响显著,表现为阔叶林土壤团聚体有机碳百分比高于针叶林,这与林分凋落物的质量有关。此外,土壤pH值和土壤质地也影响土壤团聚体有机碳百分比。这表明气温上升和人为干扰导致的林分类型改变都可能引起土壤团聚体有机碳的下降,加剧气候变化。该研究结果有助于了解土壤团聚体有机碳的变异规律,为预测全球变化下土壤有机碳响应提供数据支持。     

Light heterogeneity affects understory plant species richness in temperate forests supporting the heterogeneity–diversity hypothesis

One of the most important drivers for the coexistence of plant species is the resource heterogeneity of a certain environment, and several studies in different ecosystems have supported this resource heterogeneity–diversity hypothesis. However, to date, only a few studies have measured heterogeneity of light and soil resources below forest canopies to investigate their influence on understory plant species richness. Here, we aim to determine (1) the influence of forest stand structural complexity on the heterogeneity of light and soil resources below the forest canopy and (2) whether heterogeneity of resources increases understory plant species richness. Measures of stand structural complexity were obtained through inventories and remote sensing techniques in 135 1‐ha study plots of temperate forests, established along a gradient of forest structural complexity. We measured light intensity and soil chemical properties on six 25 m² subplots on each of these 135 plots and surveyed understory vegetation. We calculated the coefficient of variation of light and soil parameters to obtain measures of resource heterogeneity and determined understory plant species richness at plot level. Spatial heterogeneity of light and of soil pH increased with higher stand structural complexity, although heterogeneity of soil pH did not increase in conditions of generally high levels of light availability. Increasing light heterogeneity was also associated with increasing understory plant species richness. However, light heterogeneity had no such effects in conditions where soil resource heterogeneity (variation in soil C:N ratios) was low. Our results support the resource heterogeneity–diversity hypothesis for temperate forest understory at the stand scale. Our results also highlight the importance of interaction effects between the heterogeneity of both light and soil resources in determining plant species richness.     

The role of landscape configuration in plant composition of floodplain forests across different physiographic areas

Questions: What is the relative importance of landscape variables compared to habitat quality variables in determining species composition in floodplain forests across different physiographic areas? How do species composition and species traits relate to effects of particular landscape variables? Do lowland and mountain areas differ in effects of landscape variables on species composition? Location: Southern Czech Republic. Methods: A total of 240 vegetation relevés of floodplain forests with measured site conditions were recorded across six physiographic areas. I tested how physiographic area, habitat quality variables and landscape variables such as current land‐cover categories, forest continuity, forest size and urbanization influenced plant species composition. I also compared how mountain and lowland areas differ in terms of the relative importance of these variables. To determine how landscape configuration affects the distribution of species traits, relationships of traits and species affinity with landscape variables were tested. Results: Among landscape variables, forest continuity, landscape forest cover and distance to nearest settlement altered the vegetation. These variables also influenced the distributions of species traits, i.e. life forms, life strategies, affinity to forest, dispersal modes, seed characteristics, flooding tolerance and Ellenberg indicator values for nitrogen, light, moisture and soil reaction. Nevertheless, physiographic area and habitat quality variables explained more variation in species composition. Landscape variables were more important in lowland areas. Forest continuity affected species composition only in lowlands. Conclusions: Although habitat quality and physiographic area explained more vegetation variability, landscape configuration was also a key factor influencing species composition and distribution of species traits. However, the results are dependent on forest geographical location, with lowland forests being more influenced by landscape variables compared to mountain forests.     

Global species–energy relationship in forest plots: role of abundance,temperature and species climatic tolerances

Aim To evaluate the strength of evidence for hypotheses explaining the relationship between climate and species richness in forest plots. We focused on the effect of energy availability which has been hypothesized to influence species richness: (1) via the effect of productivity on the total number of individuals (the more individuals hypothesis, MIH); (2) through the effect of temperature on metabolic rate (metabolic theory of biodiversity, MTB); or (3) by imposing climatic limits on species distributions. Location Global. Methods We utilized a unique ‘Gentry‐style’ 370 forest plots data set comprising tree counts and individual stem measurements, covering tropical and temperate forests across all six forested continents. We analysed variation in plot species richness and species richness controlled for the number of individuals by using rarefaction. Ordinary least squares (OLS) regression and spatial regressions were used to explore the relative performance of different sets of environmental variables. Results Species richness patterns do not differ whether we use raw number of species or number of species controlled for number of individuals, indicating that number of individuals is not the proximate driver of species richness. Productivity‐related variables (actual evapotranspiration, net primary productivity, normalized difference vegetation index) perform relatively poorly as correlates of tree species richness. The best predictors of species richness consistently include the minimum temperature and precipitation values together with the annual means of these variables. Main conclusion Across the world's forests there is no evidence to support the MIH, and a very limited evidence for a prominent role of productivity as a driver of species richness patterns. The role of temperature is much more important, although this effect is more complex than originally assumed by the MTB. Variation in forest plot diversity appears to be mostly affected by variation in the minimum climatic values. This is consistent with the ‘climatic tolerance hypothesis’ that climatic extremes have acted as a strong constraint on species distribution and diversity.     

Temperate forest termites: ecology,biogeography, and ecosystem impacts

1. Wood decomposition in temperate forests is dominated by termites, fungi, and some species of ants and beetles. Outside of urban areas, temperate termite ecology is largely unknown, particularly when compared to tropical termites and other temperate organisms in the functional guild of wood‐decomposing animals. 2. This review combines climate habitat modelling with knowledge of species physiology, behaviour, and community interactions to identify and prioritise future research on temperate termite ecology and biogeography. 3. Using a correlative climate model, the regional distributions of three common temperate forest termite species are shown to correlate with different aspects of climate (e.g. mean versus minimum monthly temperature), but that overall their distributions within temperate systems correlate more strongly with temperature variables than with precipitation variables. 4. Existing data are synthesised to outline how the subterranean, wood‐nesting behaviour of most temperate forest termite species links their activity to an additional set of non‐climate controls: wood type and tree species, soil depth, fungal activity, ant abundances and phenology, and competitive asymmetries among termite species. 5. Although fine‐scale estimates of temperate termite abundances are rare, we provide upper bounds on their ecosystem impacts and illustrate how their regional abundances may influence forest structure and habitat availability for other organisms. 6. This review highlights that rigorous ecological studies in non‐urban, intact ecosystems – with a particular focus on community interactions – are critically needed to accurately project future abundances, economic impacts, and ecosystem effects of temperate forest termites.     

DCA Ordination,Quantitative Classification and Environmental Interpretation of Plant Communities in Dongling Mountain

Basing on the detrended corespendenee analysis (DCA) , twb-way indicative species analysis (TWINSPAN) and environmental interpretation mathematical models and warm temperate deciduous-broad leaf forest community samples collected from Dongling mountain in Beijing, primary vegetation types and ecological gradients, and their quantitative relations with environmental factors of the region were studied. The data from 26 climate stations in this region were used to get the multivarient regression for estimating the climate information of various warm temperate deciduous-broad leaf forest according to longitude, latitude and altitude of each sample plot. It is shown that the vegetation types of warm temperate deciduous-broad leaf forest and their distribution are mainly determined by the thermal and moisture ( include soil fertility) gradients. In moisture gradients, in mid-montane from drier to moisture there are Spiraea trilobata shrubland-Vitex negundo shrubland-Prunus sibirica shrubland -manmade Pinus tabulaeformis forest-Quercus liaotungensis forest -mixed deciduous-broad leaf forest- Betula dahurica forest; In subalpine from drier to moisture there are meadow-Caragana jubata shrubland-Betula costata forest. In thermal gradients, from warm to cold there are manmade Pinus tabulaeformis forest-Virex negundo shrubland–Quercus liaotungensis forest -Betula dahurica forest-mixed deciduous-broad leaf forest -Spiraea trilobata shrubland -Prunus siberica shrubland -manmade Larix princips forest-Betula platyphylla forest - B. costata forest-subalpine meadow -Caragana jubata shrubiand . Vegetation of Dongling mountain exists 4 polars anal 2 centers, 4 polars are subalpine Caragana jubata shrubland ( drier and cold habitat), mid-low montane Virex negundo shrubland (drier and warm habitat), subalpine B. costata forest (moisture and cold habitat) and mid-montane B. dahurica forest (moisture and warm). Two centers are Quercus liaotungensis forest and mixed deciduous-broad leaf forest (actuality) , and subalpine coniferous forest (the spruce and larch forest, is the potential center). The dominant and indicative plant species are Aconitum sinomontanurn (cold and moisture), Poa botryoides , Dendrantherna zavadskii, Aconiturn kusnezoffii and Carex rigescencs (cold and drier), Maianthemurn bi foliurn and Corylus rnandshurica (warm and moisture) Spiraea trilobata and Prunus siberica (warm and drier). And these species could be indication species for succession, its would indicate the state of pioneer communities. The Plant-geographic mathematical model of DCA axles (1 and 2) and environment factors (climate and soil) have been set up.