Climatic controls of vegetation vigor in four contrasting forest types of India—evaluation from National Oceanic and Atmospheric Administration’s Advanced Very High Resolution Radiometer datasets (1990–2000)

Ten-day advanced very high resolution radiometer images from 1990 to 2000 were used to examine spatial patterns in the normalized difference vegetation index (NDVI) and their relationships with climatic variables for four contrasting forest types in India. The NDVI signal has been extracted from homogeneous vegetation patches and has been found to be distinct for deciduous and evergreen forest types, although the mixed-deciduous signal was close to the deciduous ones. To examine the decadal response of the satellite-measured vegetation phenology to climate variability, seven different NDVI metrics were calculated using the 11-year NDVI data. Results suggested strong spatial variability in forest NDVI metrics. Among the forest types studied, wet evergreen forests of north-east India had highest mean NDVI (0.692) followed by evergreen forests of the Western Ghats (0.529), mixed deciduous forests (0.519) and finally dry deciduous forests (0.421). The sum of NDVI (SNDVI) and the time-integrated NDVI followed a similar pattern, although the values for mixed deciduous forests were closer to those for evergreen forests of the Western Ghats. Dry deciduous forests had higher values of inter-annual range (RNDVI) and low mean NDVI, also coinciding with a high SD and thus a high coefficient of variation (CV) in NDVI (CVNDVI). SNDVI has been found to be high for wet evergreen forests of north-east India, followed by evergreen forests of the Western Ghats, mixed deciduous forests and dry deciduous forests. Further, the maximum NDVI values of wet evergreen forests of north-east India (0.624) coincided with relatively high annual total precipitation (2,238.9 mm). The time lags had a strong influence in the correlation coefficients between annual total rainfall and NDVI. The correlation coefficients were found to be comparatively high (R²=0.635) for dry deciduous forests than for evergreen forests and mixed deciduous forests, when the precipitation data with a lag of 30 days was correlated against NDVI. Using multiple regression approach models were developed for individual forest types using 16 different climatic indices. A high proportion of the temporal variance (>90%) has been accounted for by three of the precipitation parameters (maximum precipitation, precipitation of the wettest quarter and driest quarter) and two of the temperature parameters (annual mean temperature and temperature of the coldest quarter) for mixed deciduous forests. Similarly, in the case of deciduous forests, four precipitation parameters and three temperature parameters explained nearly 83.6% of the variance. These results suggest differences in the relationship between NDVI and climatic variables based upon the time of growing season, time interval and climatic indices over which they were summed. These results have implications for forest cover mapping and monitoring in tropical regions of India.     

Forest ecosystems of east and southeast Asia in a global perspective

Owing to the influence of the Tibeto-Himalayan Highland, the east-and southeastcoastal zone of the Asian continent lacks the subtropical dry belt, which elsewhere in the world separates temperate forest areas from the humid tropics. Thus forest climates with sufficient rainfall cover coastal areas of the Western Pacific from subarctic eastern Siberia to equatorial SE Asia, giving rise to a sequence of five forest formations. The warmtemperate evergreen (lucidophyll) forest formation is peculiar to this region and represents the east-coast counterpart of Mediterranean sclerophyll forest, which develops under the west-coast climate with a different pattern of seasonal rainfall distribution. The characteristics of the five formations and their latitudinal distribution were briefly described as being related to climatic environments. Certain ecosystem properties such as floristic diversity and the rate of organic matter decomposition were found to be very sensitive to thermal gradients, whereas the responses of plant biomass, primary productivity, etc. to changes in thermal climate were less apparent.     

中国主要森林生态系统水文功能的比较研究(英文)

 基于中国不同区域生态站的观测资料,着重从降雨截留（林冠截留、枯枝落叶层截持和土壤蓄水）、调节径流和蒸散等3个方面对我国主要森林生态系统的水文生态功能进行了比较研究。各生态系统林冠年截留量在134～626 mm间变动,由大到小排列为：热带山地雨林,亚热带西部山地常绿针叶林,热带半落叶季雨林,温带山地落叶与常绿针叶林,寒温带、温带山地常绿针叶林,亚热带竹林,亚热带、热带东部山地常绿针叶林,寒温带、温带山地落叶针叶林,温带、亚热带落叶阔叶林,亚热带山区常绿阔叶林,亚热带、热带西南山地常绿针叶林,南亚热带常绿阔叶林,亚热带山地常绿阔叶林。枯落物持水量可以达到自身干重的2～5倍,但也因林型而异。土壤非毛管持水量变动在36～142 mm之间,平均89 mm。常绿阔叶林的非毛管持水量通常高于100 mm,而寒温带/温带落叶阔叶林和常绿针叶林通常低于100 mm. 土壤的非毛管持水量通常占生态系统中截持水量的90%,其次是枯落物和林冠层。这说明,森林土壤在调节降雨截留中占有重要地位,其水文功能的大小取决于土壤结构和空隙度,而这些恰恰又受枯落物和森林植被特征的影响。森林皆伐后,一般地表径流会显著地增加,而适当抚育措施则对地表径流影响不大。流域径流受诸多因素的影响,包括植被、土壤、气候、地形、地貌以及人类影响导致的流域景观变化,比较研究表明森林变化对流域径流的影响尚未得到一致的规律性的结果。通过对比研究不同森林的蒸散变化,发现随降雨量的增加,森林蒸散量略有增加,而相对蒸散率却在下降,相对蒸散率在40%～90%间变动。     

Effects of Historical Selective Logging on Anuran Communities in a Wet Evergreen Forest,South India

Vast areas of tropical evergreen forests have been selectively logged in the past, and many areas continue to be logged. The impacts of such logging on amphibians are poorly understood. I examined the response of anuran communities to historical selective logging in a wet evergreen forest in south India. Anuran assemblages in unlogged forest were compared with assemblages in selectively logged forest. Forty 10 m × 10 m quadrats in forest, riparian zones, and streams of unlogged and selectively logged forests were searched at night for anurans. Species richness did not appear to be affected by logging. However, anuran density varied significantly and was 42 percent lower in selectively logged forests compared to unlogged forests. Anuran densities also varied significantly across microhabitats, with highest densities in streams of both selectively logged and unlogged forests. Patterns of niche overlap varied with selective logging as niche breadth either expanded, contracted, or remained neutral for different species. Ordination analysis explained 95 percent of the variation in species assemblage across selectively logged and unlogged forests. The assemblage in selectively logged forest was nested within unlogged forest. Among the habitat characteristics, litter thickness and water depth had the highest influence on the assemblage. This was followed by litter/water temperature, air temperature, and lastly relative humidity. It appears that species richness and composition of anurans in selectively logged forests is converging with unlogged forests, but the effects of historical logging seem to persist on anuran densities and their niche characteristics even ca 40 yr since logging ceased.     

江西省大岗山主要森林类型降雨再分配特征

以江西大岗山地区杉木林、常绿阔叶林和毛竹林为研究对象,分析其对降水再分配过程的影响.结果表明: 2012年4-6月,研究区降水量为531.6 mm,以小到中雨为主,单次最大降雨量为61.7 mm.研究期间,毛竹林总穿透雨量最大,常绿阔叶林最小.降水量相同条件下,毛竹林与杉木林的穿透雨量相差不大;降水量较大且相同时,常绿阔叶林的穿透雨量明显小于另外两种林型;穿透雨在林内有明显的空间变异性.杉木林、常绿阔叶林和毛竹林的树干径流率分别为1.4%、8.9%和8.8%.杉木林树干径流与另外两种林型差异极显著(P<0.01).3种林型树干径流量均与前期降水条件有关,毛竹林相关程度最小,杉木林最大.3种林型林冠截留量大小依次为杉木林(30.5%)>阔叶林(25.5%)>毛竹林(19.2%).在该地区常见降雨条件下(小雨),杉木林截留率明显高于另外两种林型.     

Impact of a drier Early-Mid-Holocene climate upon Amazonian forests

This paper uses a palaeoecological approach to examine the impact of drier climatic conditions of the Early-Mid-Holocene (ca 8000-4000 years ago) upon Amazonia's forests and their fire regimes. Palaeovegetation (pollen data) and palaeofire (charcoal) records are synthesized from 20 sites within the present tropical forest biome, and the underlying causes of any emergent patterns or changes are explored by reference to independent palaeoclimate data and present-day patterns of precipitation, forest cover and fire activity across Amazonia. During the Early-Mid-Holocene, Andean cloud forest taxa were replaced by lowland tree taxa as the cloud base rose while lowland ecotonal areas, which are presently covered by evergreen rainforest, were instead dominated by savannahs and/or semi-deciduous dry forests. Elsewhere in the Amazon Basin there is considerable spatial and temporal variation in patterns of vegetation disturbance and fire, which probably reflects the complex heterogeneous patterns in precipitation and seasonality across the basin, and the interactions between climate change, drought- and fire susceptibility of the forests, and Palaeo-Indian land use. Our analysis shows that the forest biome in most parts of Amazonia appears to have been remarkably resilient to climatic conditions significantly drier than those of today, despite widespread evidence of forest burning. Only in ecotonal areas is there evidence of biome replacement in the Holocene. From this palaeoecological perspective, we argue against the Amazon forest 'dieback' scenario simulated for the future.     

哀牢山常绿阔叶林水源涵养功能及其在应对西南干旱中的作用

为了解云南哀牢山中山湿性常绿阔叶林在2010年初西南地区特大干旱中是否遭遇水分胁迫,及其水源涵养功能在应对干旱中的作用,测定了该森林土壤和主要树种在2010年旱季的水分状况,并对比研究了原生林和森林经砍伐烧垦后形成的毛蕨菜-玉山竹群丛的土壤持水、凋落物持水、水面蒸发和土壤水分季节动态。结果表明:常绿阔叶林主要树种在2010年初西南特大干旱中并未遭受水分胁迫(最旱月叶片凌晨水势高于-0.4 MPa)。虽然常绿阔叶林土壤含水量和地下水位在最旱月都达到了有观测以来的最低点,但主要根系分布区的土壤水势仍不低于-0.5 MPa,并高于毛蕨菜-玉山竹群丛。森林较好的水分状况和原生常绿阔叶林较好的水源涵养功能有关。常绿阔叶林的土壤总持水量尤其是非毛管持水量要显著大于毛蕨菜-玉山竹群丛,同时也大于云南地区的一些次生林和人工林。常绿阔叶林地表丰富的凋落物通过持水和抑制土壤蒸发也对水源涵养有一定作用。哀牢山常绿阔叶林良好的水源涵养功能,充足的土壤地下水储存弥补了旱季和特大干旱中降水的不足。结果指示原生林在水源涵养中不可替代的作用,以及加强原生林保护在提高区域抗干旱能力中的重要意义。     

Test of Fox's assembly rule for functional groups in lemur communities in Madagascar

This paper examines to what extent an assembly rule designed by Fox for small terrestrial mammal communities is also applicable to communities of arboreal lemurs in Madagascar. This approach extends the testing of Fox's assembly rule to a new biogeographic region and a different phylogenetic radiation. The rule operates on a functional rather than on the taxonomic level. It specifies that: "There is a much higher probability that each species entering a community will be drawn from a different functional group, until each group is represented before the cycle repeats" (Fox, 1987: 201). This rule was tested with lemur communities from 14 sites in evergreen rain forests and nine sites in dry deciduous forests of Madagascar. Lemur species were assigned to one of three different functional groups based on dietary preferences: omnivores, frugivores, folivores. The rule applies almost perfectly to extant lemur communities in evergreen rain forest. Present communities in dry deciduous forests are not ordered as perfectly as communities of the rain forest sites, but they also deviate from random assembly as generated by the null model. Including extinct species of the dry forest ecosystem indicates that the at present unfavoured composition of the lemur community has been derived from a favoured state through extinction of the large folivorous and frugivorous lemur species. In the lemur communities of the eastern Malagasy rain forest, the assembly went through at least four, and in the Holocene dry forest ecosystem through even five, cycles without failing. This assigns considerable significance to the underlying mechanisms (most likely interspecific competition) and indicates that they are still effective in the forests of Madagascar. The dry deciduous forests might have been subject to recent natural and anthropogenic changes which interfere with the operation of these deterministic processes.     

滇中常绿阔叶林及云南松林水文作用的初步研究

 本文研究了滇中地区山地常绿阔叶林及云南松林的林冠截留量,冠流和茎流量,地表水土流失量,林地枯枝落叶层持水量,土壤含水量以及雨水、冠流、茎流和地表迳流中营养元素(N、P、K、Ca和Mg)的含量,并分析比较了针、阔两类森林调节和涵养水分的作用和降水中林冠养分的淋溶、迁移特点,对了解滇中亚热带山地森林生态系统的功能和生产力的研究,对本区森林资源的保护,林业的合理经营,均有重要意义。     

基于阈值法的山区森林常绿、落叶特征遥感自动识别方法——以贡嘎山地区为例

森林的常绿、落叶特征是土地覆被产品的重要属性。由于山区地形复杂,地表遥感辐射信号地形效应明显,导致山区森林常绿、落叶特征遥感自动识别一直是难点。提出了一种基于阈值法的山区森林常绿、落叶特征遥感自动识别简单实用方法。该方法利用多源、多时相遥感影像,选择归一化植被指数(NDVI)为指标,通过统计参考样本的NDVI在生长季和非生长季的差异,自动找出区分常绿、落叶特征的阈值,基于判别规则识别山区森林常绿、落叶特征。以贡嘎山地区为例,分别以多时相Landsat TM影像(简称TM)、多时相环境减灾卫星影像(简称HJ)为单源数据,多时相的HJ、TM组合影像为多源数据,验证该方法的有效性。实验结果表明,该方法能够有效识别山区森林常绿、落叶特征,总体精度达到93.87%,Kappa系数为0.87。该方法适用于山区大面积森林常绿、落叶特征遥感自动提取,已被成功应用于"生态十年"专项西南地区土地覆被数据的生产。     

Deforestation rates in insular Southeast Asia between 2000 and 2010

Insular Southeast Asia experienced the highest level of deforestation among all humid tropical regions of the world during the 1990s. Owing to the exceptionally high biodiversity in Southeast Asian forest ecosystems and the immense amount of carbon stored in forested peatlands, deforestation in this region has the potential to cause serious global consequences. In this study, we analysed deforestation rates in insular Southeast Asia between 2000 and 2010 utilizing a pair of 250 m spatial resolution land cover maps produced with regional methodology and classification scheme. The results revealed an overall 1.0% yearly decline in forest cover in insular Southeast Asia (including the Indonesian part of New Guinea) with main change trajectories to plantations and secondary vegetation. Throughout the region, peat swamp forests experienced clearly the highest deforestation rates at an average annual rate of 2.2%, while lowland evergreen forests declined by 1.2%/yr. In addition, the analysis showed remarkable spatial variation in deforestation levels within the region and exposed two extreme concentration areas with over 5.0% annual forest loss: the eastern lowlands of Sumatra and the peatlands of Sarawak, Borneo. Both of these areas lost around half of their year 2000 peat swamp forest cover by 2010. As a whole this study has shown that deforestation has continued to take place on high level in insular Southeast Asia since the turn of the millennium. These on‐going changes not only endanger the existence of numerous forest species endemic to this region, but they further increase the elevated carbon emissions from deforested peatlands of insular Southeast Asia thereby directly contributing to the rising carbon dioxide concentration in the atmosphere.     

广州三种森林粗死木质残体（CWD）的储量与分解特征

粗死木质残体(Coarse Woody Debris, CWD)对森林生态系统的稳定性具有不可忽视的贡献.对广州3种森林CWD的储量与分解特征进行了调查分析,结果表明:(1)CWD储量及其与相应森林总生物量比值均表现为常绿阔叶林>针阔混交林>针叶林;枯立木与倒木为CWD的主要成分,其中,针叶CWD主要物种为马尾松(Pinus massonianai),阔叶CWD物种主要为荷木(Schima superba)与黄杞(Engelhardtia chrysolepis)等.(2)CWD径级主要集中在<10cm的范围内,存在状态主要为中级腐烂状态,干扰与竞争是3种森林CWD产生的主要因素.(3)针叶林、针阔混交林与常绿阔叶林CWD的分解常数k分别为0 0244、0.0407和0.0487,即分解速率为常绿阔叶林>混交林>针叶林;随着CWD的分解,N、P与木质素的含量逐渐升高,C、C/N与木质素/N呈降低趋势.     

Early Holocene chronology and environment of Ampasambazimba,A Malagasy subfossil lemur site

According to a traditional but hitherto untested reconstruction of Madagascar’s Holocene environment, continuous forest preceded the monotonous grassland formations that now cover most of the island’s interior. Preliminary analyses of pollen samples collected near¹⁴C-dated horizons at Ampasambazimba (central Madagascar) indicate that a mosaic of woodlands, bushlands, and savanna existed close to this important vertebrate subfossil site around 7000–8000 BP. Although most members of Madagascar’s recently extinct “subfossil” fauna are thought to have been forest dwellers, several may have preferred a more open habitat like the one inferred for the region of Ampasambazimba. Dry savanna-woodland burns more readily than does dense forest and may have been more severely affected by the forces which transformed the Malagasy environment during the later Holocene. If so, the loss of savanna-woodland, not dense forest, may have been an important factor in the subfossil extinctions.     

不同生境条件下紫茎泽兰化感作用的变化与入侵力关系的研究

 在紫茎泽兰(Eupatorium adenophorum)入侵地,草本层中的本地植物的多度和盖度与紫茎泽兰的多度和盖度具有显著的负相关关系,落叶阔叶林和公路边生境的紫茎泽兰相对多度和盖度为常绿阔叶林生境的3～5倍;而本地草本植物在组成种类、相对多度和盖度在落叶阔叶林和公路边生境比常绿阔叶林生境减少了30 %、50 % 和70 %。用生物检测的方法研究常绿阔叶林、落叶阔叶林、公路边——３个不同生境下的紫茎泽兰根和茎的水浸提液的化感作用表明：不同生境的紫茎泽兰茎和根的化感作用存在差异,即公路边>落叶阔叶林下>常绿阔叶林下,关联分析显示出不同生境条件下的化感作用力与本地植物的相对多度存在显著的相关关系,证明不同生境的化感作用的差异是紫茎泽兰的入侵效果的原因之一;在白菜(Brassica rapa)幼苗生物量生长抑制试验中,各样地的茎提取液处理的白菜幼苗生物量之间的差异大于各样地的根提取液处理之间的差异,说明对于不同样地的紫茎泽兰的入侵力,地上部分的化感作用比地下部分具有更大的贡献力。落叶阔叶林下和公路边的紫茎泽兰生长旺盛、现存单位面积生物量远远高于常绿阔叶林下,这将促使落叶阔叶林和公路边生境的单位面积上的紫茎泽兰种群的化感作用大于常绿阔叶林下的紫茎泽兰种群,使落叶阔叶林和公路边生境的本地植物群落比常绿阔叶林下的本地植物群落面临较大的竞争压力,加速落叶阔叶林下和公路边生境的本地植物群落的衰退。     

Variation in modern pollen from tropical evergreen forests and the monsoon seasonality gradient in SW India

Abstract. This study analyses the pollen signature of tropical lowland forests (< 1000 m a.s.l.) in the Asian monsoon climate. Its aim is to investigate how well the pollen data can reproduce the vegetation patterns in tropical India, and how the variations in the pollen composition are related to the gradient of decreasing plant moisture availability (measured by the ratio of actual over equilibrium evapotranspiration) that is associated with the strong seasonality of precipitation that characterizes the monsoon climate regime. We used canonical correspondence analysis (CCA) to relate the variations in the pollen composition of 71 surface soil samples from evergreen and semi‐evergreen forests distributed along the western coast of south India (8° 48’ N‐15° 08’ N), with the climate characteristics of the sampling sites. We show that variations in plant moisture availability strongly determine variations in the pollen composition; for example evergreen and semi‐evergreen forests can be distinguished on the basis of their pollen assemblages. Variations in the mean temperature of the coldest month associated with elevation also determine distinct pollen assemblages; for example evergreen forests above 800 m a.s.l. present different pollen signatures than those below this altitude/temperature limit. Variations in the relative abundance of some pollen taxa are strongly related to plant moisture availability and taxa indicators of climate can be identified. Hence, modern pollen assemblages from tropical forests in south India carry considerable information about vegetation patterns and climate. Paleoclimatic changes, notably in the monsoon season, could be quantified.     

中国土壤动物多样性监测: 探知土壤中的奥秘

土壤动物多样性变化及其对环境的指示作用已被学术界和政府决策部门高度关注。本文从土壤动物多样性监测的重要性及面临的挑战、国内外土壤动物多样性监测概况等方面进行了评述, 提出了未来、尤其是2016-2020年我国土壤动物多样性监测的目标、站点布局、样地设置、监测类群和指标等, 并讨论了在制定土壤动物多样性监测方案时需考虑的问题, 有助于在全国开展多点化土壤动物多样性及分布状况的监测工作, 建立标准统一、数据共享的土壤动物监测网, 提供完整的、可信的监测数据, 为国家生态文明建设提供科技支撑。     

Contrasting patterns of phylogenetic diversity across climatic zones of Western Ghats: A biodiversity hotspot in peninsular India

This study attempts to understand the biogeographic history of the Western Ghats forests by investigating decoupling between phylogenetic and taxonomic diversity. We specifically test whether the deciduous forests have been recently established, whether the southern region was a refuge, and whether the deciduous and evergreen forest species have disparate evolutionary histories. We used species composition data from 23 forest types along the Western Ghats for all woody angiosperms above 10‐cm diameter at breast height. Forests were broadly grouped as either evergreen or deciduous. Mean phylogenetic distances corrected for species richness and mean phylogenetic beta diversity corrected for shared species were assessed using z‐scores from null distributions. Null distributions were generated by randomizing the species relationships on the phylogeny. We found that all evergreen forests showed a greater phylogenetic diversity as compared with null expectations. Deciduous forests showed the inverse pattern. Within the evergreen belt, there was a decreasing phylogenetic diversity from south to north, as predicted by the southern refuge hypothesis. The phylogenetic beta diversity across evergreen–deciduous forests was lesser than the null expectation, whereas it was much higher across forests within the evergreen belt. This study provides the first phylogenetic evidence for the antiquity of evergreen forests as well as the southern refuge hypothesis in the Western Ghats. The deciduous forests species have shared evolutionary histories with the evergreen forest species, suggesting multiple shifts between evergreen and deciduous states through the lineages. Conversely, the evergreen species exhibited a disparate evolutionary history across these forests, possibly owing to sharper ecological or climatic gradients.     

Critical Analysis of Forest Degradation in the Southern Eastern Ghats of India: Comparison of Satellite Imagery and Soil Quality Index

India has one of the largest assemblages of tropical biodiversity, with its unique floristic composition of endemic species. However, current forest cover assessment is performed via satellite-based forest surveys, which have many limitations. The present study, which was performed in the Eastern Ghats, analysed the satellite-based inventory provided by forest surveys and inferred from the results that this process no longer provides adequate information for quantifying forest degradation in an empirical manner. The study analysed 21 soil properties and generated a forest soil quality index of the Eastern Ghats, using principal component analysis. Using matrix modules and geospatial technology, we compared the forest degradation status calculated from satellite-based forest surveys with the degradation status calculated from the forest soil quality index. The Forest Survey of India classified about 1.8% of the Eastern Ghats’ total area as degraded forests and the remainder (98.2%) as open, dense, and very dense forests, whereas the soil quality index results found that about 42.4% of the total area is degraded, with the remainder (57.6%) being non-degraded. Our ground truth verification analyses indicate that the forest soil quality index along with the forest cover density data from the Forest Survey of India are ideal tools for evaluating forest degradation.     

Seedling Traits Determine Drought Tolerance of Tropical Tree Species

Water availability is the most important factor determining tree species distribution in the tropics, but the underlying mechanisms are still not clear. In this study, we compared functional traits of 38 tropical tree species from dry and moist forest, and quantified their ability to survive drought in a dry‐down experiment in which wilting and survival were monitored. We evaluated how seedling traits affect drought survival, and how drought survival determines species distribution along the rainfall gradient. Dry forest species tended to have compound leaves, high stem dry matter content (stem dry mass/fresh mass), and low leaf area ratio, suggesting that reduction of transpiration and avoidance of xylem cavitation are important for their success. Three functional groups were identified based on the seedling traits: (1) drought avoiders with a deciduous leaf habitat and taproots; (2) drought resisters with tough tissues (i.e., a high dry matter content); and (3) light‐demanding moist forest species with a large belowground foraging capacity. Dry forest species had a longer drought survival time (62 d) than moist forest species (25 d). Deciduousness explained 69 percent of interspecific variation in drought survival. Among evergreen species, stem density explained 20 percent of the drought survival. Drought survival was not related to species distribution along the rainfall gradient, because it was mainly determined by deciduousness, and species with deciduous seedlings are found in both dry and moist forests. Among evergreen species, drought survival explained 28 percent of the variation in species position along the rainfall gradient. This suggests that, apart from drought tolerance, other factors such as history, dispersal limitation, shade tolerance, and fire shape species distribution patterns along the rainfall gradient.     

南亚热带三种主要森林降雨及其再分配过程中的养分差异规律

马尾松林、针阔叶混交林和季风常绿阔叶林是南亚热带鼎湖山地区由演替初期到成熟森林过程的典型代表,对3种林地的降雨量及其再分配过程进行观测,并测定该过程中养分(N、P、K、Ca、Mg)浓度。结果表明,大气降雨经过冠层再分配后,除Ca外,各养分浓度在穿透雨和树干流中都有所增加,树干流增加的幅度更大。穿透雨中Ca元素浓度低于大气降水,这一现象在3种林型均有表现。穿透雨和树干流中养分浓度在演替系列上没有显示出一致的规律,但比较不同演替阶段的输入量可以看出,树干流养分输入量随演替进行呈增加趋势。经过冠层作用后,雨水带来的养分输入量大于凋落物分解输入量,这种现象在马尾松林和混交林尤为明显。表明大气降雨不仅促使养分元素从冠层向地表迁移,而且提供了演替初期植物生长所需的重要养分。