Light and warming drive forest understorey community development in different environments

Plant community composition and functional traits respond to chronic drivers such as climate change and nitrogen (N) deposition. In contrast, pulse disturbances from ecosystem management can additionally change resources and conditions. Community responses to combined environmental changes may further depend on land‐use legacies. Disentangling the relative importance of these global change drivers is necessary to improve predictions of future plant communities. We performed a multifactor global change experiment to disentangle drivers of herbaceous plant community trajectories in a temperate deciduous forest. Communities of five species, assembled from a pool of 15 forest herb species with varying ecological strategies, were grown in 384 mesocosms on soils from ancient forest (forested at least since 1850) and postagricultural forest (forested since 1950) collected across Europe. Mesocosms were exposed to two‐level full‐factorial treatments of warming, light addition (representing changing forest management) and N enrichment. We measured plant height, specific leaf area (SLA) and species cover over the course of three growing seasons. Increasing light availability followed by warming reordered the species towards a taller herb community, with limited effects of N enrichment or the forest land‐use history. Two‐way interactions between treatments and incorporating intraspecific trait variation (ITV) did not yield additional inference on community height change. Contrastingly, community SLA differed when considering ITV along with species reordering, which highlights ITV’s importance for understanding leaf morphology responses to nutrient enrichment in dark conditions. Contrary to our expectations, we found limited evidence of land‐use legacies affecting community responses to environmental changes, perhaps because dispersal limitation was removed in the experimental design. These findings can improve predictions of community functional trait responses to global changes by acknowledging ITV, and subtle changes in light availability. Adaptive forest management to impending global change could benefit the restoration and conservation of understorey plant communities by reducing the light availability.     

Does taxonomic homogenization imply functional homogenization in temperate forest herb layer communities?

Biotic homogenization, the decrease in beta diversity among formerly distinct species assemblages, has been recognized as an important form of biotic impoverishment for more than a decade. Although researchers have stressed the importance of the functional dimension to understand its potential ecological consequences, biotic homogenization has mostly been studied at a taxonomic level. Here, we explore the relationship between taxonomic and functional homogenization using data on temperate forest herb layer communities in NW Germany, for which taxonomic homogenization has recently been demonstrated. We quantified beta diversity by partitioning Rao’s quadratic entropy. We found a general positive relationship between changes in taxonomic and functional beta diversity. This relationship was stronger if multiple functional traits were taken into account. Averaged across sites, however, taxonomic homogenization was not consistently accompanied by functional homogenization. Depending on the traits considered, taxonomic homogenization occurred also together with functional differentiation or no change in functional beta diversity. The species shifts responsible for changes in beta diversity differed substantially between taxonomic and functional beta diversity measures and also among functional beta diversity measures based on different traits. We discuss likely environmental drivers for species shifts. Our study demonstrates that functional homogenization must be explicitly studied as an independent phenomenon that cannot be inferred from taxonomic homogenization.     

Forest fragmentation drives Atlantic forest of northeastern Brazil to biotic homogenization

Aim To examine whether the tree flora of the Atlantic forest of northeastern Brazil has experienced detectable taxonomic homogenization via the proliferation of native pioneer species in response to habitat loss and fragmentation. Location Biotic homogenization (BH) was examined across the Atlantic forest of northeast Brazil, i.e. a 56,000 km² piece of tropical forest and a distinct centre of species endemism in South America. Methods We assessed a dataset consisting of 5122 tree records and compared the similarity of tree floras from 12 semi‐natural sub‐regions of the Atlantic forest between two time periods: pre‐1980 (plant records between 1902 and 1980), and post‐1980 (between 1981 and 2006). To understand the mechanisms leading to BH (1) tree floras were ordered (via non‐metric multidimensional scaling – NMDS) by date (pre/post 1980) based on species occurrence and frequency, (2) NMDS axes were regressed against the proportion of those species that increased their occurrence post‐1980 (i.e. the winner species), and (3) patterns of geographic distribution and frequency of particular life‐history traits were examined across winner species and a control group. Results Tree floras across the Atlantic forest became c. 20–40% more similar to each other post‐1980, but patterns of species similarity were also influenced by between‐plot geographical distance. NMDS ordination clearly segregated pre‐ and post‐1980 floras with a clear signal of floristic convergence. Furthermore, winner tree species were largely composed of short‐lived and small‐seeded pioneer species that exhibit wide geographic distributions. Main conclusions Our results suggest that tropical forest biotas are susceptible to taxonomic homogenization (i.e. increasing levels of similarity) in the context of severe human‐disturbance via the proliferation of particular groups of native species comprised mainly by ecologically‐plastic, generalist species. We are thus extending the concept of homogenization to address and highlight a pervasive biological shift in the structure of tropical forest communities currently taking place across hyper‐fragmented landscapes.     

环境因子对山西太岳山典型森林类型物种多样性及其功能多样性的影响

该研究采用典型样地法,调查群落内物种分布并测量植物功能性状(叶面积和植株高度),对山西太岳山不同坡位华北落叶松-白桦混交林以及辽东栎次生林物种多样性及其功能多样性进行比较分析,探究环境因子对不同群落层次(乔木、灌木、草本)物种多样性及其功能多样性的影响机制,以及环境因子与群落构建之间的联系,为森林生态系统多样性研究以及经营管理提供理论依据。结果显示:(1)华北落叶松-白桦混交林的物种分布更加均匀,物种多样性和功能多样性(乔木层)均显著高于辽东栎次生林。(2)华北落叶松-白桦混交林乔木层功能均匀度与功能分散指数显著高于辽东栎次生林,但灌木草本层低于辽东栎次生林。(3)不同群落层次的物种多样性与功能多样性均呈正相关关系,影响物种分布和性状分布的环境因子存在差异,物种多样性受多种环境因子的综合影响,而单个环境因子对功能多样性影响较大,环境解释力与林分类型和群落层次相关。(4)乔木层物种多样性主要受土壤pH、冠层结构(MLA、林分开度)以及光照影响,灌木层物种多样性与土壤pH和MLA密切相关,林下总辐射、土壤养分(SOC、STN)、土壤相对含水率是影响草本层物种分布的主要环境因子;冠层结构(MLA、林分开度)是影响乔木层功能多样性最主要的环境因子,土壤pH和坡位分别是华北落叶松-白桦混交林和辽东栎次生林灌木层功能多样性的主要影响因子,影响草本层功能多样性的主要环境因子是土壤相对含水率与LAI。研究表明,在垂直分层的森林生态系统中,不同群落层次竞争的主要环境资源存在差异,乔木层通过改变冠层结构和林内环境限制林下物种分布和性状分布。     

Long‐term colonization ecology of forest‐dwelling species in a fragmented rural landscape – dispersal versus establishment

Species colonization in a new habitat patch is an efficiency indicator of biodiversity conservation. Colonization is a two‐step process of dispersal and establishment, characterized by the compatibility of plant traits with landscape structure and habitat conditions. Therefore, ecological trait profiling of specialist species is initially required to estimate the relative importance of colonization filters. Old planted parks best satisfy the criteria of a newly created and structurally matured habitat for forest‐dwelling plant species. We sampled species in 230 ancient deciduous forests (source habitat), 74 closed‐canopy manor parks (target habitats), 151 linear wooded habitats (landscape corridors), and 97 open habitats (isolating matrix) in Estonia. We defined two species groups of interest: forest (107 species) and corridor specialists (53 species). An extra group of open habitat specialists was extracted for trait scaling. Differing from expectations, forest specialists have high plasticity in reproduction mechanisms: smaller seeds, larger dispersules, complementary selfing ability, and diversity of dispersal vectors. Forest specialists are shorter, less nutrient‐demanding and mycorrhizal‐dependent, stress‐tolerant disturbance‐sensitive competitors, while corridor specialists are large‐seeded disturbance‐tolerant competitors. About 40% of species from local species pools have immigrated into parks. The historic forest area, establishment‐related traits, and stand quality enhance the colonization of forest specialists. The openness of landscape and mowing in the park facilitate corridor specialists. Species traits in parks vary between a forest and corridor specialist, except for earlier flowering and larger propagules. Forest species are not dispersal limited, but they continue to be limited by habitat properties even in the long term. Therefore, the shady parts of historic parks should be appreciated as important forest biodiversity‐enhancing landscape structures. The habitat quality of secondary stands can be improved by nurturing a heterogeneous shrub and tree layer, and modest herb layer management.     

Individualistic responses of forest herb traits to environmental change

• Intraspecific trait variation (ITV; i.e. variability in mean and/or distribution of plant attribute values within species) can occur in response to multiple drivers. Environmental change and land‐use legacies could directly alter trait values within species but could also affect them indirectly through changes in vegetation cover. Increasing variability in environmental conditions could lead to more ITV, but responses might differ among species. Disentangling these drivers on ITV is necessary to accurately predict plant community responses to global change.
• We planted herb communities into forest soils with and without a recent history of agriculture. Soils were collected across temperate European regions, while the 15 selected herb species had different colonizing abilities and affinities to forest habitat. These mesocosms (384) were exposed to two‐level full‐factorial treatments of warming, nitrogen addition and illumination. We measured plant height and specific leaf area (SLA).
• For the majority of species, mean plant height increased as vegetation cover increased in response to light addition, warming and agricultural legacy. The coefficient of variation (CV) for height was larger in fast‐colonizing species. Mean SLA for vernal species increased with warming, while light addition generally decreased mean SLA for shade‐tolerant species. Interactions between treatments were not important predictors.
• Environmental change treatments influenced ITV, either via increasing vegetation cover or by affecting trait values directly. Species’ ITV was individualistic, i.e. species responded to different single resource and condition manipulations that benefited their growth in the short term. These individual responses could be important for altered community organization after a prolonged period.

     

Habitat fragmentation,EFN‐bearing trees and ant communities: Ecological cascades in Atlantic Forest of northeastern Brazil

Habitat fragmentation has a marked impact on the functional composition of tropical forest tree assemblages, and such change is likely to cascade through other trophic levels. Here, we investigate how habitat fragmentation affects extrafloral nectary (EFN)‐bearing plants and ant functional groups known to attend EFNs in a fragmented landscape of the Atlantic Forest. Extrafloral nectary‐bearing trees were identified in 50 0.1‐ha plots located in forest fragments, edge and interior patches. Ants were surveyed in 30 1‐m² litter samples in each of 17 forest fragments and in forest interior. Extrafloral nectary‐bearing plants accounted for 19.9% of individuals and 10.5% of species and included both pioneer and shade‐tolerant species similarly rich in the three habitat types. However, shade‐tolerant individuals accounted for >80% of EFN‐bearing plants in forest interior, compared with 2% in forest edge and 29% in fragments. Forest edge and fragment plots had a third fewer EFN‐bearing individuals and species compared with forest interior. This appeared to have important implications for local ant communities as the density of EFN‐bearing trees was the most important variable explaining the species richness of arboreal dominant ants. Our results show that plant loser–winner replacements promoted by forest fragmentation can cascade through higher trophic levels, with implications for forest dynamics and biodiversity conservation.     

Plant functional trait response to environmental drivers across European temperate forest understorey communities

• Functional traits respond to environmental drivers, hence evaluating trait‐environment relationships across spatial environmental gradients can help to understand how multiple drivers influence plant communities. Global‐change drivers such as changes in atmospheric nitrogen deposition occur worldwide, but affect community trait distributions at the local scale, where resources (e.g. light availability) and conditions (e.g. soil pH) also influence plant communities.
• We investigate how multiple environmental drivers affect community trait responses related to resource acquisition (plant height, specific leaf area (SLA), woodiness, and mycorrhizal status) and regeneration (seed mass, lateral spread) of European temperate deciduous forest understoreys. We sampled understorey communities and derived trait responses across spatial gradients of global‐change drivers (temperature, precipitation, nitrogen deposition, and past land use), while integrating in‐situ plot measurements on resources and conditions (soil type, Olsen phosphorus (P), Ellenberg soil moisture, light, litter mass, and litter quality).
• Among the global‐change drivers, mean annual temperature strongly influenced traits related to resource acquisition. Higher temperatures were associated with taller understoreys producing leaves with lower SLA, and a higher proportional cover of woody and obligate mycorrhizal (OM) species. Communities in plots with higher Ellenberg soil moisture content had smaller seeds and lower proportional cover of woody and OM species. Finally, plots with thicker litter layers hosted taller understoreys with larger seeds and a higher proportional cover of OM species.
• Our findings suggest potential community shifts in temperate forest understoreys with global warming, and highlight the importance of local resources and conditions as well as global‐change drivers for community trait variation.

     

中国典型森林生态系统乔木层群落物种多样性的空间分布格局及其影响因素

物种多样性地理分布格局及其成因是生物地理学和宏观生态学研究的核心问题之一,基于中国13个典型森林生态系统乔木层群落植物的调查数据,分析物种多样性随经纬度的变化规律,探讨物种多样性空间分布格局的影响因素。结果表明:(1) 13个典型森林生态系统的4个物种多样性指数均随经纬度上升而下降,其中物种丰富度变化更为显著,而Shannon-Wiener指数、Simpson指数和Pielou指数随经度上升变化不显著;(2)相关性分析结果显示,物种多样性指数与植物特性、能量和水分因子的单因素相关关系并不一致。其中,物种丰富度、Shannon-Wiener指数和Simpson指数与年均温、最冷月均温、温度年较差和潜在蒸散量的相关性最显著(P0.01),Pielou指数与年均温、最冷月均温、实际蒸散量、潜在蒸散量和郁闭度有显著相关关系(P0.05);(3)方差分解结果表明,能量和水分的共同作用对物种多样性指数空间分布格局的解释率最高,达到15%—42%;植物特性、能量和水分因子三者共同作用对物种多样性指数空间分布格局解释率次之,为14%—27%;植物特性与能量因子或水分因子两者之间的共同作用以及植物特性和水分因子独立作用对物种多样性指数空间分布格局的解释率较小,其中能量因子对物种多样性指数空间分布格局的单独解释率高于植物特性或水分因子。研究表明能量和水分共同作用是影响大尺度森林乔木层物种多样性空间分布格局形成的主要因素,但植物特性的差异对物种多样性空间分布格局影响也不可忽视。     

The species richness–productivity relationship in the herb layer of European deciduous forests

Aim In contrast to non‐forest vegetation, the species richness–productivity (SR‐P) relationship in forests still remains insufficiently explored. Several studies have focused on the diversity of the tree layer, but the species richness of temperate deciduous forests is mainly determined by their species‐rich herb layer. The factors controlling herb‐layer productivity may differ from those affecting tree layers or open herbaceous vegetation, and thus the SR‐P relationship and its underlying processes may differ. However, the few relevant studies have reported controversial results. Here we explore the SR‐P relationship in the forest herb layer across different areas from oceanic to continental Europe, and put the effect of habitat productivity on species richness into context with other key factors, namely soil pH and light availability. Location North‐western Germany, Czech Republic, Slovakia and southern Urals (Russia). Methods We measured herb‐layer species richness and biomass, soil pH and tree‐layer cover in 156 vegetation plots of 100 m² in deciduous forests. We analysed the SR‐P relationship and the relative importance of environmental variables using regression models for particular areas and separate forest types. Results We found a consistent monotonic increase in the herb‐layer species richness with productivity across all study areas and all forest types. Soil pH and light availability also affected species richness, but their relative importance differed among areas. Main conclusions We suggest that the monotonically increasing SR‐P relationship in the forest herb layer results from the fact that herb‐layer productivity is limited by canopy shading; competition within the herb layer is therefore not strong enough to exclude many species. This differs fundamentally from open herbaceous vegetation, which is not subject to such productivity limits and consequently exhibits a unimodal SR‐P relationship. We present a conceptual model that might explain the differences in the SR‐P relationship between the forest herb layer and open herbaceous vegetation.     

The interaction of gap age and microsite for herb layer species in a near‐natural spruce forest

Question: To what degree does the regeneration of understorey forest species depend on gaps of different age and on gap‐induced and non‐gap‐induced microsites? Do species preferences for a specific microsite change with the developmental stage of the gap? How do different species in the understorey interact over time? Location: Near‐natural spruce forest on Mt. Brocken in the Harz National Park, Germany. Methods: We established 90 study plots, stratified according to different gap age classes and undisturbed forest, and including subplots with three different gap‐induced types of microsites (logs, stumps and root plates) and two non‐gap‐induced microsites (moss‐covered rocks and ordinary forest ground). Results: Significant interactions of species were encountered with gap age as well as with microsite type, light availability and competition. While shoot densities of Vaccinium myrtillus were highest at intermediate gap age, Calamagrostis villosa and Trientalis europaea showed highest densities in the oldest gaps. The species preferred different microsites but had higher densities on non‐gap‐induced microsites, and their preferences changed over time. Unexpectedly, species shoot densities were not always negatively affected by densities of competing species. Conclusion: The results confirmed the importance of gaps for regeneration of forest herb layer species, but pointed to a much higher importance of microsites that were not induced by gaps compared to gap‐induced microsites. Niche differentiation between different herb layer species can be conceived as species‐specific preferences for microsite types that change with gap age, as a result of light conditions, degree of decay of logs and root plates and presence of competitors.     

广西凭祥不同年龄红椎林林下植物物种多样性及其环境解释

林下植被作为森林生态系统的重要组成部分,其在调控森林群落结构和功能上发挥着至关重要的作用。从揭示人工林林下植物物种组成的关键控制因素的目标出发,以不同年龄红椎林灌木层和草本层的植物群落作为研究对象,采用野外调查和室内分析相结合的方法,重点探究林下植物物种组成与环境因子之间的关系及其关键控制因子。研究结果表明:不同年龄红椎林的林下植物物种组成存在明显差异;RDA结果表明,胸高断面积是影响灌木层物种组成的最主要因子,胸高断面积、坡度和海拔能显著影响影响草本层的物种组成;方差分解结果表明,所调查的生物和非生物因子分别解释灌木层和草本层物种组成变异的63%和47%,微环境和植物之间的相互作用是影响林下植物群落物种变异的最主要因素,而土壤与微环境、土壤与植物两者之间,以及微环境、植物和土壤三者之间的相互作用对林下植物群落的物种组成的影响较小,甚至无影响,微环境的独立效应对林下植物物种组成的影响高于植物或土壤因素。     

Paying the colonization credit: converging plant species richness in ancient and post-agricultural forests in NE Germany over five decades

Massive historical land cover changes in the Central European lowlands have resulted in a forest distribution that now comprises small remnants of ancient forests and more recently established post-agricultural forests. Here, land-use history is considered a key driver of recent herb-layer community changes, where an extinction debt in ancient forest remnants and/or a colonization credit in post-agricultural forests are being paid over time. On a regional scale, these payments should in theory lead toward a convergence in species richness between ancient and post-agricultural forests over time. In this study, we tested this assumption with a resurvey of 117 semi-permanent plots in the well-studied deciduous forests of the Prignitz region (Brandenburg, NE Germany), where we knew that the plant communities of post-agricultural stands exhibit a colonization credit while the extinction debt in ancient stands has largely been paid. We compared changes in the species richness of all herb layer species, forest specialists and ancient forest indicator species between ancient and post-agricultural stands with linear mixed effect models and determined the influence of patch connectivity on the magnitude of species richness changes. Species richness increased overall, but the richness of forest specialists increased significantly more in post-agricultural stands and was positively influenced by higher patch connectivity, indicating a convergence in species richness between the ancient and post-agricultural stands. Furthermore, the richness of ancient forest indicator species only increased significantly in post-agricultural stands. For the first time, we were able to verify a gradual payment of the colonization credit in post-agricultural forest stands using a comparison of actual changes in temporal species richness.     

大兴安岭呼中地区3种林分的群落特征、物种多样性差异及其耦合关系

准确理解天然林林分群落特征及其与物种多样性耦合关系是提升天然林管理、达到多样性保护的关键。选择大兴安岭呼中地区典型落叶松林、杂木林、白桦落叶松林为研究对象,分别对乔木层、灌木层和草本层特征(高度、胸径、冠幅、盖度等)进行调查并计算丰富度指数、多样性指数和均匀度指数,旨在探究林分间差异及其耦合关系变化。结果表明:(1)乔木层的树高、枝下高表现出杂木林落叶松林白桦落叶松(P0.05);落叶松林的胸径比白桦落叶松林和杂木林的高出6%和11%;灌木层的高度、盖度、地径、冠幅和草本层多度、盖度、高度在森林类型间均未表现出显著差异。(2)3个森林类型的乔、灌、草丰富度指数R、Shannon-Wiener指数及Simpson指数均表现出杂木林最大,乔木层和草本层呈相同规律,即杂木林白桦落叶松林落叶松林,而灌木层表现出杂木林落叶松林白桦落叶松林;白桦落叶松林和杂木林的乔木层均匀度Pielou指数和Alatalo指数约为落叶松林的3倍左右,而在灌木层和草本层在森林类型间差异不显著(P0.05)。(3)典范对应分析(CCA)结果表明林分群落特征和生物多样性关系存在明显森林类型间差异。总体表现为灌木特征(冠幅、地径)、草本层特征(盖度、多度和高度)对多样性均有较大影响;白桦落叶松林和杂木林的胸径对多样性影响明显,而落叶松林的乔木高度(树高、枝下高)对多样性影响较大。杂木林随着灌木盖度、草本高度的增加,草本物种多样性降低、乔木多和灌木物种多样性增加;而落叶松林相同的多样性变化多伴随草本高度增加、多度和盖度变小。灌木层物种多样性增加多与乔木和草本物种多样性降低相伴随,在杂木林中同时伴随着乔木胸径和草本的盖度、多度增大、灌木冠幅变小,而白桦落叶松林则伴随灌木冠幅和草本多度盖度的减小。以上结果表明,林分群落特征与物种多样性存在耦合关系,上述解耦合结果为通过维持良好森林结构、多样性保护具有实践意义。     

杉木林改造成乡土阔叶林对林下植物物种组成和多样性的影响

把杉木林改造成乡土阔叶林,不仅能提供高价值木材,而且能够提升生态系统服务功能,是我国目前改造退化针叶林最常见的经营模式之一,但这些改变对其林下植物物种组成和多样性的影响及机制我们尚知之甚少。以南亚热带杉木林采伐迹地上重新种植的杉木林、红锥林和米老排林为研究对象,调查研究其灌木层和草本层植物物种组成和多样性,结果表明：（1）和杉木林相比,改造后的红锥林和米老排林灌木层的植物物种丰富度和多样性均呈极显著降低（P<0.01）,但其草本层植物只有物种丰富度极显著降低（P<0.01）,多样性均无显著变化（P>0.05）;（2）主成分分析（PCA）表明改造后的林分灌木层和草本层的植物物种组成发生明显的变化,冗余分析（RDA）确定导致林分灌木层植物物种组成发生变化的主要原因是杉木林改造成红锥林和米老排林后的冠层透光率、土壤碳氮比、土壤含水量和凋落物碳氮比的显著变化,而冠层透光率和土壤碳氮比的显著变化是导致其林下草本层植物物种组成发生明显变异的主要因子;（3）方差分解结果显示微地形、乔木特性和土壤理化性质的独立效应对灌木层和草本层植物物种组成的影响高于它们的交互效应。该研究为科学经营管理人工林和提高人工林生态系统多功能性提供科学依据。     

宝天曼地区栓皮栎林恢复过程中高等植物物种多样性变化

对宝天曼地区不同恢复阶段栓皮栎林的高等植物物种多样性特征进行了初步分析。结果表明,各层物种丰富度和多样性指数在不同恢复阶段栓皮栎林表现出草本层＞灌木层＞乔木层的趋势。乔木层物种丰富度和多样性指数基本上随恢复时间的增加而增加;灌木层在未破坏的栓皮栎林内较低,而在其他恢复阶段的栓皮栎林内基本相同;草本层在恢复５年、１５年和２５年的栓皮栎林中较高,而在恢复４５年和未破坏的栓皮栎林内较低。乔木层物种均匀度指数在未破坏的栓皮栎林中较高,在恢复２５年的栓皮栎林中较低;灌木层在恢复４５年的栓皮栎林中较高,在恢复１５年的栓皮栎林较低;草本层在恢复５年的栓皮栎林中较高,在恢复１５年的栓皮栎林中较低。不同恢复阶段栓皮栎林各层次间的物种多样性差异大多不显著,只有乔木层和草本层及灌木层和草本层之间的物种丰富度指数有显著差异。不同恢复阶段栓皮栎林在乔木层物种多样性特征上的差异最大,在灌木层物种多样性特征上有一定差异,在草本层物种多样性特征上没有明显的差异。     

额尔齐斯河流域垂枝桦林群落结构特征与物种多样性相关分析

为阐明植物群落结构特征和物种多样性之间的相互关系,选择额尔齐斯河流域白桦林国家森林公园的天然垂枝桦(Betula pendula)纯林、垂枝桦苦杨混交林、垂枝桦白柳混交林为研究对象,分林层调查群落的基本特征参数(高度、枝下高、冠幅、胸径、盖度等),计算物种重要值、丰富度指数、多样性指数、均匀度指数,并进行典范对应分析。结果表明:(1)垂枝桦白柳混交林的乔木层树高、枝下高和灌木层的地径、盖度均最高;3种群落的草本层特征参数(除基径)均具有显著差异;垂枝桦白柳林的盖度分别比垂枝桦苦杨林和垂枝桦纯林高19.1%和51.8%。(2)3种群落的乔木层重要值最高为垂枝桦,灌木层为疏花蔷薇(Rosa laxa)、阿尔泰山楂(Crataegus altaica),草本层为莎薹草(Carex bohemica)。(3)3种群落类型中乔木层的丰富度指数R、Simpson指数、Shannon-Wiener指数和灌木层的Pielou指数、Alatalo指数呈现出相同规律,即垂枝桦白柳混交林>垂枝桦苦杨混交林>垂枝桦纯林;草本层中除Alatalo指数之外,其他指数均呈现垂枝桦纯林>垂枝桦苦杨混交林>垂枝桦白柳混交林(P>0.05)。(4)CCA排序结果表明,不同垂枝桦林群落结构特征与物种多样性关系有差异。其中,垂枝桦纯林中,对物种多样性影响最大的是乔木枝下高、灌木株高、冠幅以及草本盖度;垂枝桦苦杨混交林中,对物种多样性影响最大的是乔木高度和冠幅、灌木冠幅和草本高度;垂枝桦白柳林中,对物种多样性影响最大的是乔木胸径、灌木冠幅、盖度以及草本高度。研究表明,乔木枝下高度、灌木冠幅、草本高度是影响3种群落类型物种多样性的主要因素。     

元江锥群落垂直结构的构建机制初探

基于功能性状探讨物种共存机制,已成为近年来群落生态学研究的热点内容。为探讨群落垂直结构构建的成因,该研究以昆明筇竹寺地区的半湿润常绿阔叶林为对象,调查乔木层、灌木层及草本层不同层次间植物叶片的功能性状。结果表明:(1)植物各功能性状均存在不同程度的随层次变化的趋势。(2)按照植物的生活型将元江锥群落分为乔木、灌木以及草本3层,与功能性状的聚类结果基本一致。(3)乔木、灌木和草本3个层次的S.E.S PW值均小于0,可知群落内物种的功能性状结构均呈现显著的发散。综上结果认为,植物群落不同物种的叶片功能特征对群落垂直方向上不同光照和水分条件组合的适应是群落垂直结构构成的主要影响因素,支持生境过滤是群落垂直结构构建的主要生态过程; 在不同层次内的物种具有不同的功能性状,同一层次内通过竞争排斥加大物种多样性; 群落垂直结构的形成是群落内垂直方向上环境因子发生变化的结果,对资源有不同需求的物种分布在不同空间高度上,群落垂直结构则是对资源的有效利用,增加了群落内物种多样性。     

东北阔叶红松林群落类型划分及物种多样性

运用TWINSPAN分类方法,对我国东北阔叶红松林群落类型进行划分,对乔木层树种进行聚类,并对东北地区长白山、大秃顶子山、平顶山和丰林保护区4个样点的物种多样性进行对比研究.结果表明:24个样地中共记录到维管束植物264种,隶属于64科147属.经过聚类,将阔叶红松林划分为3个群落类型组和7个群落类型;同时,将33个乔木树种间的关联性划分为8组.阔叶红松林群落的物种丰富度和多样性为草本层>灌木层>乔木层.在4个样点中,长白山的样地平均物种丰富度最高,为63.长白山和大秃顶子山乔木层和灌木层的物种多样性略高于平顶山和丰林保护区;丰林保护区草本层的物种多样性为2.83,高于其它3个样点.平顶山灌木层和长白山草本层的均匀度最低,分别为0.71和0.80.     

白龙江上游地区森林植物群落物种多样性的研究

 白龙江上游地区属长江防护林工程重点地区之一。根据36个样地的调查资料,分析了该地区森林植物群落物种多样性的特征：群落内各层物种丰富度指数的大小顺序为“灌木层>草本层>乔木层”;均匀度指数变化比较复杂,在杜鹃巴山冷杉（Rhododendron fastigiatum-Abies fargesii）林中为“草本层>灌木层>乔木层”,在苔藓巴山冷杉林中为“乔木层>灌木层>草本层”,其余群落中为“灌木层>草本层>乔木层”;多样性指数的大小顺序为“乔木层<灌木层和草本层”,而灌木层与草本层的多样性指数随林分郁闭度变化而变化,在郁闭度30%的杜鹃巴山冷杉林中,草本层大于灌木层,在郁闭度47%的箭竹巴山冷杉林中,草本层和灌木层相当,在郁闭度55%以上的各个群落内,灌木层大于草本层。同一海拔不同坡向群落的物种多样性表现为分布于阳坡的油松（Pinus tabulaeformis）林大于分布于阴坡的草类云杉（Picea asperata）林。物种多样性沿海拔梯度的变化表现为随海拔升高先降低后增加,从海拔2 400 m的栎类阔叶林,2 600 m的草类云杉林,2 800 m的箭竹(Sinarundinaria nitida)巴山冷杉林,到3 000 m的苔藓巴山冷杉林和3 200 m的杜鹃巴山冷杉林,物种多样性依次下降,到海拔3 400 m的高山杜鹃（Rhododendron fastigiatum）灌丛,物种多样性增加。物种多样性在紫果云杉(Picea purpurea)林的演替系列中表现为随群落演替发展而增加,后降低,在针阔混交林阶段达到最大。