Firescape ecology: how topography determines the contrasting distribution of fire and rain forest in the south‐west of the Tasmanian Wilderness World Heritage Area

Aim To test the hypothesis that ‘islands’ of fire‐sensitive rain forest are restricted to topographic fire refugia and investigate the role of topography–fire interactions in fire‐mediated alternative stable state models. Location A vegetation mosaic of moorland, sclerophyll scrub, wet sclerophyll eucalypt forest and rain forest in the rugged, fire‐prone landscapes of south‐west Tasmania, Australia. Methods We used geospatial statistics to: (1) identify the topographic determinants of rain forest distribution on nutrient‐poor substrates, and (2) identify the vegetation and topographic variables that are important in controlling the spatial pattern of a series of very large fires (> 40,000 ha) that were mapped using Landsat Thematic Mapper (TM) satellite imagery. Results Rain forest was more likely to be found in valleys and on steep south‐facing slopes. Fires typically burned within highly flammable treeless moorland and stopped on boundaries with less flammable surrounding vegetation types such as wet sclerophyll forest and rain forest. Controlling for the effect of vegetation, fires were most likely to burn on flats, ridges and steep north‐facing slopes and least likely to burn in valleys and on steep south‐facing slopes. These results suggest an antagonism between fire and rain forest, in which rain forest preferentially occupies parts of the landscape where fire is least likely to burn. Main conclusions The distribution of rain forest on nutrient‐poor substrates was clearly related to parts of the landscape that are protected from fire (i.e. topographic fire refugia). The relative flammability of vegetation types at the landscape scale offers support to the proposed hierarchy of fire frequencies (moorland > scrub > wet sclerophyll > rain forest) that underpins the ecological models proposed for the region. The interaction between fire occurrence and a range of topographic variables suggests that topography plays an important role in mediating the fire–vegetation feedbacks thought to maintain vegetation mosaics in south‐west Tasmania. We suggest that these fire–topography interactions should be included in models of fire‐mediated alternative stable vegetation states in other fire‐prone landscapes.     

复杂地形草地植被碳储量遥感估算研究进展

草地生态系统是我国最大的陆地生态系统,其植被碳储量的准确评估对维护国家生态安全和指导畜牧发展有重要作用。植被生物量和草地面积是草地植被碳储量估算的关键,随着遥感技术的发展,两者估算精度和效率显著提高,先后发展出多种草地生物量遥感估算模型和土地覆被产品,并已在平坦地区取的较好估算结果。然而,复杂地形区迥异于平地的几何形态和水热分布所产生的不均一的生态系统结构和功能,给草地生物量和草地面积的遥感估算带来诸多困难,影响对草地植被碳储量的准确判定。本文在回顾国内外草地植被碳储量遥感估算方法与所需关键参数的基础上,对遥感估算复杂地形草地植被碳储量过程中所面临“遥感影像地形效应的去除和尺度选择”、“植被指数与地形指标的选取”、“过程模型植被生长参数的率定”、“草地面积估算”以及“气象数据与复杂地形上微气候的匹配”等问题进行了总结并提出相应的解决思路,以期为草地植被碳储量遥感估算模型的合理构建以及估算精度的提高提供参考。     

Geographical ecology of the palms (Arecaceae): determinants of diversity and distributions across spatial scales

Background

The palm family occurs in all tropical and sub-tropical regions of the world. Palms are of high ecological and economical importance, and display complex spatial patterns of species distributions and diversity.

Scope

This review summarizes empirical evidence for factors that determine palm species distributions, community composition and species richness such as the abiotic environment (climate, soil chemistry, hydrology and topography), the biotic environment (vegetation structure and species interactions) and dispersal. The importance of contemporary vs. historical impacts of these factors and the scale at which they function is discussed. Finally a hierarchical scale framework is developed to guide predictor selection for future studies.

Conclusions

Determinants of palm distributions, composition and richness vary with spatial scale. For species distributions, climate appears to be important at landscape and broader scales, soil, topography and vegetation at landscape and local scales, hydrology at local scales, and dispersal at all scales. For community composition, soil appears important at regional and finer scales, hydrology, topography and vegetation at landscape and local scales, and dispersal again at all scales. For species richness, climate and dispersal appear to be important at continental to global scales, soil at landscape and broader scales, and topography at landscape and finer scales. Some scale–predictor combinations have not been studied or deserve further attention, e.g. climate on regional to finer scales, and hydrology and topography on landscape and broader scales. The importance of biotic interactions – apart from general vegetation structure effects – for the geographic ecology of palms is generally underexplored. Future studies should target scale–predictor combinations and geographic domains not studied yet. To avoid biased inference, one should ideally include at least all predictors previously found important at the spatial scale of investigation.     

Spatial relationships between NDVI and topographic factors at multiple scales in a watershed of the Minjiang River,China

Improvement in vegetation cover in the upper reaches of the Minjiang River protects major freshwater sources and constructs ecological barriers in the upstream of Yangtze River located in southwest China. However, the spatially varying relationships between normalized difference vegetation index (NDVI) and topographic factors at multiple scales remain unclear. In this study, the two-dimensional discrete wavelet transform (2D-DWT) and geographically weighted regression (GWR) were combined to build a framework for examining the complex spatial relationships between NDVI and topographic factors at multiple scales. Based on the gridded datasets of NDVI and digital elevation model (DEM) of a small watershed located in the upper reaches of the Minjiang River situated in southwest China, the influence of topographic factors on NDVI variation in each grid and which topographic variables correlated most with the NDVI at each location were analyzed in this study. The grid data were decomposed into smooth and detail components using 2D-DWT. The results revealed that elevation, slope, and aspect exhibited different scale effects on NDVI in different wavelet components. In the smooth components, the spatial correlation of NDVI with elevation, slope, and south-facing index (SFI) of aspect increased with the decomposition scale, whereas topographic factors had different degrees of influence on NDVI. Elevation was found to be the most important topographic factor that determined the spatial distribution of NDVI on both sides of the valley, and SFI exhibited the highest effect on NDVI when elevation was higher than 2500 m. In the detail components, the spatial distribution of the most important topographic factor affecting the NDVI was not evident at a smaller scale, whereas it became obvious at 480 m scale. SFI was found to be more important than elevation and slope at a larger scale. These results will help in understanding the complex relationship between NDVI and topographic factors and determining the appropriate topographic location for ecological restoration.     

Disentangling the Role of Climate,Topography and Vegetation in Species Richness Gradients

Environmental gradients (EG) related to climate, topography and vegetation are among the most important drivers of broad scale patterns of species richness. However, these different EG do not necessarily drive species richness in similar ways, potentially presenting synergistic associations when driving species richness. Understanding the synergism among EG allows us to address key questions arising from the effects of global climate and land use changes on biodiversity. Herein, we use variation partitioning (also know as commonality analysis) to disentangle unique and shared contributions of different EG in explaining species richness of Neotropical vertebrates. We use three broad sets of predictors to represent the environmental variability in (i) climate (annual mean temperature, temperature annual range, annual precipitation and precipitation range), (ii) topography (mean elevation, range and coefficient of variation of elevation), and (iii) vegetation (land cover diversity, standard deviation and range of forest canopy height). The shared contribution between two types of EG is used to quantify synergistic processes operating among EG, offering new perspectives on the causal relationships driving species richness. To account for spatially structured processes, we use Spatial EigenVector Mapping models. We perform analyses across groups with distinct dispersal abilities (amphibians, non-volant mammals, bats and birds) and discuss the influence of vagility on the partitioning results. Our findings indicate that broad scale patterns of vertebrate richness are mainly affected by the synergism between climate and vegetation, followed by the unique contribution of climate. Climatic factors were relatively more important in explaining species richness of good dispersers. Most of the variation in vegetation that explains vertebrate richness is climatically structured, supporting the productivity hypothesis. Further, the weak synergism between topography and vegetation urges caution when using topographic complexity as a surrogate of habitat (vegetation) heterogeneity.     

Relationship between topography and the distribution of matorral plant species in the Saharan Atlas: Case of Djebel Amour,Algeria

One of the primary goals in community ecology is to determine the relative importance of processes and mechanisms that control biodiversity. The reduced coverage of vegetation and the severe losses of biodiversity in semiarid matorrals have recently become serious concerns in the Saharan Atlas in southern Algeria. In terms of research, the control of the spatial distribution of vegetation by the topographic factors has not received the attention it merits in Djebel Amour's region. This study combined several multivariate analyses to assess quantitatively the extent and nature of the topographic influence on the distribution of matorral plant species. Thirty plots (20 m × 20 m) were selected according to their physiognomy for the field survey of vegetation and topography in a semiarid mountainous region. The distributions of vegetation differed significantly amongst topographies, indicating different environmental conditions and determine a turnover of important species. Most species colonize downslopes, and only some persist on steep-slopes and summits. The low coverage of vegetation (36.98%) on steep-slopes was due to the serious soil erosion and rockiness 66.5–83.1%. The low average richness in summits (39.67) was due to elevation and negative effect of trees. Elevation, then rockiness and slope were respectively the main topographic factors influencing the distribution of matorral plants. The relationship between topography and distribution could be described by a linear model. Seventeen linear models were built for eleven floristic variables with three topographic factors, elevation, rockiness and slope explained 26–83% of the variance in distribution, also four groups of plant species were listed according to topographic positions. The suitability of plant species to the topographic factors should be considered in the restoration of matorrals in the study area. The results of this study will be useful for selecting the appropriate species and the potential sites for seeding to improving damaged matorral ecosystems in this area. However, additional investigations on soils, water availability and microclimate are required to clarify the mechanism of distribution of plant species in these ecosystems.     

Elevational changes in vascular plants richness,diversity, and distribution pattern in Abune Yosef mountain range,Northern Ethiopia

The aim of this research is to investigate the patterns of vascular plant species richness,diversity,and distribution along an elevation gradient in the Abune Yosef mountain range,Ethiopia.Preferential systematic sampling was employed to collect vegetation and environmental data along the elevation gradient.We found that plant species richness declines monotonically from low to high elevations.Specifically,vascular plant species richness and diversity were lower in the Afroalpine grassland(high elevation)than in the Dry evergreen Afromontane forest and Ericaceous forest(low elevations).In contrast,endemic vascular plant richness was significantly higher in the Afroalpine grassland than in the Dry evergreen Afromontane forest and Ericaceous forest.Elevation showed a significant impact on the richness,diversity,and endemism of vascular plants.According to Sorensen's coefficient,the similarity between Dry evergreen Afromontane forest and Ericaceous forest vegetation types is higher(32%)than the similarity between Ericaceous forest and Afroalpine grassland(18%).Only 5%similarity was recorded between the Dry evergreen Afromontane forest and Afroalpine grassland.Growth forms showed different elevationai richness patterns.Trees and liana increased monotonically up to 3300 m.Shrub and herb richness patterns followed a hump-shaped and inverted hump-shaped pattern along the elevation gradient.The elevation patterns of vascular plant species richness,diversity,and growth form in the present study may be attributed to differences in management intensity,spatial heterogeneity,microclimatic variations,and anthropogenic disturbances.     

Determinants of Tree Assemblage Composition at the Mesoscale within a Subtropical Eucalypt Forest

A variety of environmental processes, including topography, edaphic and disturbance factors can influence vegetation composition. The relative influence of these patterns has been known to vary with scale, however, few studies have focused on environmental drivers of composition at the mesoscale. This study examined the relative importance of topography, catchment flow and soil in influencing tree assemblages in Karawatha Forest Park; a South-East Queensland subtropical eucalypt forest embedded in an urban matrix that is part of the Terrestrial Ecosystem Research Network South-East Queensland Peri-urban SuperSite. Thirty-three LTER plots were surveyed at the mesoscale (909 ha), where all woody stems ≥1.3 m high rooted within plots were sampled. Vegetation was divided into three cohorts: small (≥1–10 cm DBH), intermediate (≥10–30 cm DBH), and large (≥30 cm DBH). Plot slope, aspect, elevation, catchment area and location and soil chemistry and structure were also measured. Ordinations and smooth surface modelling were used to determine drivers of vegetation assemblage in each cohort. Vegetation composition was highly variable among plots at the mesoscale (plots systematically placed at 500 m intervals). Elevation was strongly related to woody vegetation composition across all cohorts (R²: 0.69–0.75). Other topographic variables that explained a substantial amount of variation in composition were catchment area (R²: 0.43–0.45) and slope (R²: 0.23–0.61). Soil chemistry (R²: 0.09–0.75) was also associated with woody vegetation composition. While species composition differed substantially between cohorts, the environmental variables explaining composition did not. These results demonstrate the overriding importance of elevation and other topographic features in discriminating tree assemblage patterns irrespective of tree size. The importance of soil characteristics to tree assemblages was also influenced by topography, where ridge top sites were typically drier and had lower soil nutrient levels than riparian areas.     

生态公益林补偿政策对植被覆盖时空格局的影响——以杭州市临安区为例

生态补偿政策绩效评价对完善政策调控和促进植被恢复具有重要意义。分析了临安2001—2015年植被覆盖的时空格局和变化,建立了植被退化地区土地利用变化矩阵。在Arc GIS软件中建立了临安地区归一化植被指数(NDVI)、国家级和省级公益林覆盖边界(重点生态公益林补偿边界)、道路、海拔、中心城镇用地边界、重点森林保护区、河流边界和地形湿度指数的多要素地理空间数据集。采用多元回归模型量化了重点生态公益林补偿政策、自然因素、城市化和其他人类活动对植被覆盖变化的影响。结果表明,2001—2015年间,临安大约有97%的林地呈现出不同程度的退化,其中中等退化程度的林地所占比例最高。多元线性回归模型的结果表明重点生态公益林补偿政策、海拔、河流距离、重点森林保护区距离和中心城镇距离对植被退化有抑制作用,道路和地形湿度指数对植被退化有促进作用。海拔在所有的外部影响因素中对植被退化的影响最大。政策覆盖地区的植被退化面积在每一个退化等级上都小于无政策覆盖地区。生态公益林补偿政策的实施对加强植被的保护,限制不合理的林地利用和改善区域环境质量具有十分重要的积极作用。     

Bioclimatic analysis in a region of southern Italy (Calabria)

In this study, an analysis of precipitation and temperature data has been performed over 67 series observed in a region of southern Italy (Calabria). At first, to detect possible trends in the time series, an analysis was performed with the Mann–Kendall non-parametric test applied at monthly and seasonal scale. An additional investigation, useful for checking the climate change effects on vegetation, has also been included analysing bioclimatic indicators. In particular, Emberger, Rivas-Martinez and De Martonne indices were calculated by using monthly temperature and precipitation data in the period 1916–2010. The spatial pattern of the indices has been evaluated and, in order to link the vegetation and the indices, different indices maps have been intersected with the land cover data, given by the Corine Land Cover map. Moreover, the temporal evolution of the indices and of the vegetation has been analysed. Results suggest that climate change may be responsible for the forest cover change, but, given also the good relationship between the various types of bioclimate and forest formations, human activities must be considered.     

Coastal dune topography as a determinant of abiotic conditions and biological community restoration in northern KwaZulu-Natal,South Africa

Topography is rarely considered as an independent goal of restoration. However, topography determines microenvironmental conditions and hence living conditions for species. Restoring topography may therefore be an important first step in ecological restoration. We aimed at establishing the relative importance of topography where coastal dunes destroyed by mining are rebuilt as part of a rehabilitation program. We assessed the response of (1) microclimatic and soil conditions, and (2) woody plant and millipede species richness and density, to location-specific topographic profiles. We enumerated the topographic profile using variables of dune morphology (aspect, elevation, and gradient) as well as relative position on a dune (crest, slope, and valley). Temperature, relative humidity, and light intensity varied with aspect, elevation, gradient, and position. However, regeneration age was a better predictor of soil nutrient availability than these topographic variables. Age also interacted with topographic variables to explain tree canopy density and species richness, as well as millipede species richness. The density of keeled millipedes (forest specialists) was best explained by topographic variables alone. The transient nature of these new-growth coastal dune forests likely masks topography-related effects on communities because age-related succession (increasing structural complexity) drives the establishment and persistence of biological communities, not habitat conditions modulated by topography. However, our study has shown that the microhabitats associated with topographic variability influence specialist species more than generalists.     

Vascular plant species richness along environmental gradients in a cool temperate to sub-alpine mountainous zone in central Japan

In order to clarify how vegetation types change along the environmental gradients in a cool temperate to sub-alpine mountainous zone and the determinant factors that define plant species richness, we established 360 plots (each 4 × 10 m) within which the vegetation type, species richness, elevation, topographic position index (TPI), slope inclination, and ground light index (GLI) of the natural vegetation were surveyed. Mean elevation, TPI, slope inclination, and GLI differed across vegetation types. Tree species richness was negatively correlated with elevation, whereas fern and herb species richness were positively correlated. Tree species richness was greater in the upper slope area than the lower slope area, whereas fern and herb species richness were greater in the lower slope area. Ferns and trees species richness were smaller in the open canopy, whereas herb species richness was greater in the open canopy. Vegetation types were determined firstly by elevation and secondary by topographic configurations, such as topographic position, and slope inclination. Elevation and topography were the most important factors affecting plant richness, but the most influential variables differed among plant life-form groups. Moreover, the species richness responses to these environmental gradients greatly differed among ferns, herbs, and trees.     

气候、植被和地形对大兴安岭林火烈度空间格局的影响

在北方森林中火干扰是森林景观变化的主导因素。林火烈度作为衡量林火动态的重要指标,较为直观地反映了火干扰对森林生态系统的破坏程度,其空间格局深刻地影响着森林景观中的多种生态过程(如树种组成、种子扩散以及植被的恢复)。解释林火烈度空间格局有助于揭示林火干扰后森林景观格局的形成机制,对预测未来林火烈度空间格局以及制定科学合理林火管理策略均有重要意义。基于LandsatTM/ETM遥感影像,将2000—2016年大兴安岭呼中林区的36场火的林火烈度划分为未过火、轻度、中度、重度4个等级。采用FRAGSTAT景观格局分析软件从类型水平上计算了斑块所占景观面积比、面积加权平均斑块面积、面积加权平均斑块分维数、面积加权边缘面积比、斑块密度5个景观指数,以对林火烈度空间格局进行了定量化描述。并且采用随机森林模型,分析了气候、地形、植被对林火烈度空间格局的影响及其边际效应。通过研究得出以下结果:(1)相对于未过火、轻度、以及中度火烧斑块,重度火烧斑块的面积更大、形状更简单;(2)海拔对重度火烧斑块的空间格局起着至关重要的作用,其次是坡向、坡度、植被覆盖度、相对湿度、温度等;(3)随着海拔的升高,面积加权平均斑块面积和面积加权平均斑块分维数的边际效应曲线呈上升趋势,而面积加权边缘面积比和斑块密度呈下降趋势;除了面积加权平均斑块面积外,都受到火前植被覆盖度的影响,且植被覆盖度为0.2—0.3范围内,重度火烧斑块在景观中所占比例最大。总的来看,2000—2016年大兴安岭呼中森林景观中重度火烧斑块与未过火、轻度以及中度火烧斑块存在显著差异性。相对于气候,地形和植被对于塑造重度火烧斑块空间格局具有重要作用。因此,应针对重度火烧区域进行可燃物处理,从景观层面上合理配置森林斑块,从而降低高烈度森林大火发生的风险。     

Ecotope mapping for landscape ecological assessment of habitat and ecosystem

An ecotope (spatial eco-space) map that considers topography and bio-organism-relevant variables emerges as an important basic framework when landscape-scale characteristics for ecosystem management and wildlife conservation are needed. A spatio-geoecological framework based on geographic information systems (GIS) and a vegetation survey were developed for wildlife habitat evaluation of national parks and applied to a representative rugged valley area of Mt. Sorak National Park in Korea. An ecotope map was classified into hundreds of types and dozens of groups by combining biological and geophysical variables. Variables included: forest vegetation type, topographic solar radiation, normalized difference vegetation index (NDVI), elevation, and anthropogenic factors, such as, streams and roads. Layers of GIS variables were produced by field surveys, modeling, satellite images, or digitalization. Vegetation surveys were carried out to identify finer-scale distribution of vegetation types in the rugged valley area. Digital forest vegetation maps from the Forestry Administrator were then modified using the field-surveyed vegetation maps. Topographic solar radiation was predicted with a daily topographic radiation model. The NDVI was calculated from the satellite imagery of a Landsat Thematic Mapper. A digital elevation model (DEM) was used and the other layers were digitized using topographical maps with a scale of 1:25000. The aim of this study is to determine the geoecological factors relating to the spatial pattern of plant community. It was cleared by the spatial pattern of environmental variables and vegetation characteristics by detrended correspondence analysis using plant species and the environmental variables of each plot. The ordination component value of the first axis shows significant regression to some environmental variables. A case study of habitat evaluation was carried out using the resultant ecotope map. The spatial distribution of potential goral habitat and vegetation characteristics were predicted and the impact of human trails on the neighboring vegetation was also examined for restoration planning. The GIS-based framework developed for wildlife habitat evaluation is useful for natural resource management and human activity control in national parks in Korea.     

Gradients within gradients: The mesoscale distribution patterns of palms in a central Amazonian forest

Questions: What are the relative contributions of environmental factors and geographic distance to palm community structure at the mesoscale, and how do they depend on the length of the environmental gradient covered? How do soil and topography affect variation of the canopy and understory palm community structure at the mesoscale? How does fine‐scale variation within the broad edaphic/topographic classes affect palm community composition? Location: Reserva Ducke, terra‐firme forest, Manaus, Brazil. Methods: Palms were sampled in 72 plots 250 m × 4 m, systematically distributed over an area of 100 km². Soil, topography and distance to watercourses were measured for all plots. The relationship between community structure axes, summarized by NMDS ordinations, and environmental predictors, was analysed with multivariate regressions. Matrix regressions were used to determine the proportions of variance explained by environmental and geographic predictors. Results: Floristic variation at the mesoscale was mostly related to environmental variation, and the proportion of variance explained depended on the amplitude of the environmental gradient. Soil was the main predictor of floristic change, but its effects differed between life forms, with the understory palm community structured within one of the edaphic/topographic classes, in association with distance to watercourses. Conclusions: Dispersal limitation does not explain palm composition at the mesoscale, and the amplitude of environmental gradients covered by the analysis can be as important as the scale of analysis, in determining the relative contributions of environmental and geographical components to community structure. Soil and topography can predict a large proportion of palm composition, but gradients differ in scale, with some environmental gradients being nested within others. Therefore, although all environmental gradients are nested within distance, they do not necessarily coincide.     

河北小五台山主要植被类型的分布与地形的关系：基于遥感信息的分析

小五台山是河北省最高峰,具有较完整的暖温带植被垂直带谱。本文通过野外群落植被调查,结合由TM遥感影像解译1：50000地形图制作的DEM数据而得到的植被图,分析了小五台山主要植被群落的分布状况及其与地形的关系。结果表明,小五台山从低海拔到高海拔,依次出现灌丛、阔叶林、针阔混交林、暗针叶林、矮林、灌丛、草甸等植被类型。森林景观的面积最大,占总面积的60．7％;平均斑块面积最大的是阔叶林和亚高山草甸,斑块破碎化最严重的是水体和针阔混交林。不同的植被类型在不同的地形条件下分布特点不同,林地在北坡所占面积比例(占总面积的75％)远大于南坡(46%),说明水分条件是小五台山森林分布的限制因子之一;灌丛和草甸与林地相反。随海拔高度的变化,不同植被类型的分布面积比例发生变化,出现替代现象,形成植被垂直带谱。由于坡度的影响,增加了带谱内植被组成的复杂性。     

The edge of two worlds: A new review and synthesis on Eurasian forest‐steppes

Aims

Eurasian forest‐steppes are among the most complex non‐tropical terrestrial ecosystems. Despite their considerable scientific, ecological and economic importance, knowledge of forest‐steppes is limited, particularly at the continental scale. Here we provide an overview of Eurasian forest‐steppes across the entire zone: (a) we propose an up‐to‐date definition of forest‐steppes, (b) give a short physiogeographic outline, (c) delineate and briefly characterize the main forest‐steppe regions, (d) explore forest‐steppe biodiversity and conservation status, and (e) outline forest‐steppe prospects under predicted climate change.

Location

Eurasia (29°–56°N, 16°–139°E).

Results and Conclusions

Forest‐steppes are natural or near‐natural vegetation complexes of arboreal and herbaceous components (typically distributed in a mosaic pattern) in the temperate zone, where the co‐existence of forest and grassland is enabled primarily by the semi‐humid to semi‐arid climate, complemented by complex interactions of biotic and abiotic factors operating at multiple scales. This new definition includes lowland forest–grassland macromosaics (e.g. in Eastern Europe), exposure‐related mountain forest‐steppes (e.g. in Inner Asia), fine‐scale forest–grassland mosaics (e.g. in the Carpathian Basin) and open woodlands (e.g. in the Middle East). Using criteria of flora, physiognomy, relief and climate, nine main forest‐steppe regions are identified and characterized. Forest‐steppes are not simple two‐phase systems, as they show a high level of habitat diversity, with forest and grassland patches of varying types and sizes, connected by a network of differently oriented edges. Species diversity and functional diversity may also be exceptionally high in forest‐steppes. Regarding conservation, we conclude that major knowledge gaps exist in determining priorities at the continental, regional, national and local levels, and in identifying clear target states and optimal management strategies. When combined with other threats, climate change may be particularly dangerous to forest‐steppe survival, possibly resulting in compositional changes, rearrangement of the landscape mosaic or even the latitudinal or altitudinal shift of forest‐steppes.     

黄土丘陵区地形、土壤水分与草地的景观格局

在黄土丘陵区,地形因素和土壤水分是决定草地景观格局的主要因素,同时草地景观格局在不同尺度上影响着景观中的流.地形因素、土壤水分和草地结构在不同尺度上有着密切的联系,研究它们之间的关系对于了解生态系统的过程十分重要.针对黄土高原异质化的草地群落结构,选取黄土丘陵区经过20多年自然封育形成的天然草地,从坡面尺度对景观格局进行了调查研究,在地形因素、土壤水分和草地结构中选取了有代表性的指标14个,用多元统计分析对选取的指标进行了主成分分析和聚类分析.聚类分析将样方分成3种植被类型,不同植被类型的海拔、坡度、20～140cm土壤含水量以及物种丰富度和生物多样性存在显著性差异.相关分析表明：海拔对0～300cm土壤含水量影响显著;海拔对草地群落盖度,坡位、坡向对草地群落的物种丰富度和生物多样性有着重要影响;而草地群落的物种丰富度和生物多样性与0～100cm土层的含水量关系密切.     

Variation in tree growth,mortality and recruitment among topographic positions in a warm temperate forest

Questions: Do the population dynamics of trees differ among topographic positions and, if so, how does topographic position affect the population dynamics of species that are distributed in a topography‐specific manner? Which is the most important life stage in determining vegetation patterns? Location: Primary and secondary warm temperate evergreen broad‐leaved forest (40 ‐ 280 m a.s.l.) on the western part of Yakushima Island, Japan. Methods: Mortality, recruitment, DBH growth and distribution of stems (= 5 cm DBH) in a 2.62‐ha plot were surveyed in 1992 and 2002 to determine the relationships between population parameters and (1) topography and (2) distribution patterns of 17 common tree species. Results: Common species (n = 17) were classified into three distribution pattern groups: group A, distributed mainly on convex slopes; group B, on concave slopes, and group C, not aggregated with respect to topographic position. Stem mortality, recruitment and DBH growth were greater in group A than in group B within each topographic class. The hierarchy of stem mortality among topographic classes for groups A and B was convex > planar > concave. Stem recruitment density was relatively high on the convex and concave slopes, respectively, for groups A and B. Conclusions The topographical positions of adult trees were not always most suited for adult survival and growth. For group A, the distribution pattern of adults was determined in the juvenile stage, while this was not the case for group B. Studies of juvenile stages are important for understanding the demographic basis of vegetation distribution patterns.     

Topographically controlled soil moisture drives plant diversity patterns within grasslands

Grasslands are recognized as biodiversity hotspots in Europe. However, protection and management of these habitats are currently constrained by a limited understanding of what determines local grassland plant diversity patterns. Here, we combined vegetation records (8,639 inventory plots) from 258 semi-natural grasslands with fine-resolution topographic data based on light detection and ranging technology to investigate the importance of topography—particularly topographically controlled soil moisture—for local and regional grassland plant diversity patterns across a 43,000 km² lowland region (Denmark). Specifically, we examined the relationships between five vegetation measures representing species composition and richness as well as functional composition (Ellenberg indicator values) and four functional topographic factors representing topographic wetness, potential solar radiation, heat balance and wind exposure. Topography emerged as an important determinant of diversity patterns in both wet and dry grasslands throughout the study region, with topographic wetness being the strongest correlate of the main local (within-site) and regional (among-sites) gradients in species composition and species’ average preferences for soil moisture. Accordingly, topography plays an important role in shaping grassland plant diversity patterns both locally and regionally throughout this lowland European region, with this role mainly driven by topographically controlled soil moisture. These findings suggest hydrology to be important to consider in the planning and management of European grasslands.