喀斯特常绿落叶阔叶混交林物种多度与丰富度空间分布的尺度效应

物种多样性的空间分布格局及其尺度效应是生态学研究的重点,对于理解物种多样性的形成和维持机制以及生物多样性的管理和保护均具有重要意义。以贵州茂兰国家级自然保护区分布的亚热带原生性喀斯特常绿落叶阔叶混交林为研究对象,分析了2个1hm2(100m×100m)样地中物种多度和丰富度的空间分布特征及其与取样尺度的关系,采用方差和变异系数描述多度和丰富度在5个尺度(5m×5m,10m×10m,20m×20m,25m×25m,50m×50m)上的空间变异性。结果表明:(1)两个样地的物种多度和丰富度具有尺度依赖性特征;(2)由于多度具有叠加性,物种多度的方差随着尺度的增加呈线性增加,而变异系数呈线性下降;(3)丰富度的方差随尺度的增加表现出单峰分布的特征,在25 m×25 m尺度上达到最大值,变异系数则随取样尺度的增加而呈线性下降。研究表明,物种多度具有尺度推演规律,而丰富度却没有,因此,应慎重进行物种丰富度的尺度推演。在分析喀斯特森林物种多样性时,应注重尺度效应带来的影响。     

海南尖峰岭热带山地雨林不同空间尺度和径级水平的物种丰富度与个体密度关联

以海南尖峰岭热带山地雨林为研究对象, 基于尖峰岭原始林60 hm²大样地, 分析了7个不同空间尺度(5 m × 5 m、10 m × 10 m、20 m × 20 m、40 m × 40 m、60 m × 60 m、80 m × 80 m、100 m × 100 m)、3个不同径级(胸径(DBH) ≥ 1.0 cm、DBH ≥ 2.5 cm、DBH ≥ 7.5 cm)物种丰富度与个体密度之间的关联性, 以期为负密度制约效应等研究的尺度选择提供参考依据。研究结果表明, 物种丰富度和个体密度之间的关联性是基于空间尺度存在的, 并受分析植株径级大小的影响。DBH ≥ 1.0 cm时, 在4个空间尺度下(5 m × 5 m、10 m × 10 m、20 m × 20 m、40 m × 40 m), 物种丰富度随个体密度增加而增加, 但物种丰富度和个体密度两者间的相关性随取样空间尺度的增大而逐渐下降; 在其他3个空间尺度下(60 m × 60 m、80 m × 80 m、100 m × 100 m), 两者间没有显著相关性。当DBH ≥ 2.5 cm和DBH ≥ 7.5 cm时, 物种丰富度和个体密度间的相关性随空间尺度变化的趋势也与上述结果基本一致; 在60 m × 60 m的空间尺度上, DBH ≥ 1.0 cm时物种丰富度和个体密度相关性不显著, DBH ≥ 2.5 cm和DBH ≥ 7.5 cm两个径级的物种丰富度和个体密度表现出弱相关性。DBH ≥ 2.5 cm和DBH ≥ 7.5 cm时, 各空间尺度下物种丰富度和个体密度之间的决定系数几乎一致, 但高于DBH ≥ 1.0 cm时两者之间的决定系数, 说明大径级植株的个体密度和物种丰富度之间有更强的关联性, 负密度制约效应和自疏效应可能是产生这种现象的主要原因。     

南亚热带混交人工林树种丰富度与土壤微生物多样性和群落组成的关系

森林植被与土壤微生物作为森林生态系统的重要组成部分,它们之间的相互作用对维持森林生态系统功能和稳定性起着重要作用。以往多在天然草地和森林生态系统开展植物多样性与土壤微生物多样性关系的研究,但人工构建的多树种混交林生态系统中树种多样性对土壤微生物群落组成的影响及其机制尚不完全清楚。因此,以南亚热带人工块状造林后自然恢复形成的多树种混交森林生态系统为研究对象,利用高通量测序技术研究了随树种丰富度(1—10种)变化土壤细菌和真菌多样性的变化规律及主要影响因子。结果表明,随树种丰富度增加,土壤真菌α多样性显著提高,但土壤细菌α多样性差异不显著;不同树种丰富度梯度间土壤细菌和真菌的群落结构组成均差异显著;Pearson相关分析表明土壤细菌α多样性主要受土壤pH和土壤铵态氮影响,而土壤pH和有效磷是土壤真菌α多样性的主要影响因子。距离冗余分析(db-RDA)表明,对土壤细菌群落组成产生显著影响的环境因子分别为土壤pH、硝态氮和芳香碳组分,而土壤有机碳、硝态氮、细根生物量和氧烷基碳组分是影响土壤真菌群落组成的主要因子。本研究的结果说明了南亚热带人工林不同树种混交后形成多树种混交林生态系统的过程中,树...     

新疆喀纳斯树种丰富度垂直格局特征

采用样带调查法,通过直接梯度、变异函数和分形函数分析,对新疆喀纳斯旅游区内设置的3条样带的树种比例及树种丰富度沿海拔梯度的变异特征进行了研究。结果表明：直接梯度刻画的不同树种所占比例在海拔梯度上的变化趋势各异;树种丰富度在整个调查尺度范围内随海拔的升高呈现明显的下降态势（P＜0.01）;半方差分析揭示：树种丰富度在中小尺度范围内的空间异质性主要由空间自相关引起的变异组成;分维分析反映出树种丰富度的分形维数偏大,且在中小尺度范围内无拐点,说明树种丰富度受随机生态学过程的影响在相应尺度范围内具有很强的空间异质性。     

茂兰喀斯特森林植物物种丰富度的垂直分布特征及环境解释

茂兰喀斯特峰丛地貌森林是目前罕见的一类原生性强、人为干扰少的非地带性森林生态系统,与常态地貌地带性森林生态系统相比差异大。该研究采用典型样地调查方法对茂兰喀斯特森林海拔在620～910 m之间的垂直样带11个样方进行调查,分析研究区顶级群落物种丰富度的垂直梯度变化特征,并用冗余分析(RDA)法分析环境因子对物种丰富度的影响,以明确垂直梯度上物种丰富度与环境因子的关系,为喀斯特自然森林生态系统的维持与恢复、保护与管理提供理论基础。结果表明：(1)该调查茂兰喀斯特峰丛共记录有维管植物511种,隶属于124科272属。(2)单因素方差分析表明,该群落不同生活型的丰富度之间存在极显著差异(P<0.01);LSD多重比较分析表明,群落丰富度水平表现为总体>灌木层>草本层>乔木层。(3)随海拔梯度的升高,群落总物种丰富度和草本层物种丰富度与海拔呈显著负相关关系(P<0.05),乔木层丰富度和灌木层丰富度与海拔无明显规律。(4)冗余分析表明,土壤C/N/P的解释率达到58%,是影响物种丰富度的主要因素。     

次生林不同类型森林边缘的鸟类物种丰富度及个体多度比较

边缘效应对动物的分布及行为会产生一定的影响,在鸟类生态学研究中已证实某些鸟类在森林内部和森林边缘区域存在着物种丰富度和个体多度的差异。于1999至2001年的春夏季,在吉林省左家自然保护区对阔叶林/农田边缘、阔叶林/灌丛边缘及阔叶林/针叶林边缘3种不同类型边缘地带的鸟类物种丰富度及个体多度进行了比较研究。结果表明,不同年间鸟类物种丰富度无显著变化,但个体多度存在着一定的波动。不同类型森林边缘的鸟类物种丰富度存在着一定的差异,阔叶林/灌丛边缘的鸟类物种丰富度最高,而阔叶林/针叶林边缘的鸟类物种丰富度最低。鸟类个体多度的总体趋势在3种不同类型的边缘差异不显著,但存在种间差异,灰椋鸟、灰头啄木鸟和喜鹊在阔叶林/农田边缘的个体多度最高,斑啄木鸟、黄胸、三道眉草和日本树莺在阔叶林/灌丛边缘的个体多度最高,而沼泽山雀、冕柳莺和山在阔叶林/针叶林边缘的个体多度最高。     

阿尔泰山小东沟林区乔木物种丰富度空间分布规律

对一定区域内生物多样性的合理保护往往需要在景观水平上了解生物多样性分布的总体规律.借助于典型抽样调查和遥感及地理信息系统相结合的方法来预测物种丰富度是定量研究生物多样性宏观分布规律的重要途径.以阿尔泰山小东沟林区为对象,在外业调查的基础上,选取主要气象因子、地形因子和植被指数(NDVI)作为预测变量,利用主成分分析和多元回归分析分别提取主要环境信息和构建物种丰富度预测模型,借助ArcGIS9.1的空间分析功能,得到了阿尔泰山小东沟林区乔木物种丰富度空间分布预测图,并利用残差图评价其精度.将小东沟乔木物种丰富度预测图分别与坡度、坡向和海拔图叠加,分析不同地形条件下乔木物种丰富度的空间分布规律.结果表明:占总研究区面积70.28％的区域,其乔木物种丰富度在3到4种之间.坡度0-5°的地形条件下乔木物种丰富度出现频率最高的数值是3,其余坡度条件下,乔木物种丰富度出现频率最高的数值是4;乔木物种丰富度在西坡和西北坡出现频率最高的数值是3,其余坡向乔木物种丰富度出现频率最高的数值均是4;海拔梯度上,乔木物种丰富度出现频率最高的数值呈现先增加后减少的趋势.残差类型面积统计表明,较强预测水平面积和中等预测水平面积占研究区总面积的94.62％,表明预测效果较好.     

南亚热带森林演替过程生物量和生产力动态特征

以鼎湖山森林演替的空间系列及黑石顶天然次生林为研究对象,探讨了南亚热带森林群落生物量和生产力动态特征。研究结果表明,随着演替进程的发展,群落的生物量不断积累,但生物量的各用份的动态趋向并不一致,其中叶生物量的最高值出现在演替的中后期．在演替过程中生产力的动态与生物量变化相一致,随着演替的进展第一性生产力不断增加,但演替过程生产力的发展速率不是均匀的,生产力在群落的演变前期发展较侠,在中、后期则发展较慢。     

热带森林不同演替阶段蚂蚁巢穴的分布特征及其影响因素

为探明热带森林蚂蚁巢穴的分布特征及其影响因素, 采用样方法研究了西双版纳不同演替阶段热带森林定居巢穴蚂蚁的种类及其巢穴的密度、盖度和空间分布特征, 并分析了土壤理化环境与蚂蚁种类总数、巢穴密度及盖度的相关性。结果表明, 不同演替阶段热带森林蚂蚁种类总数、巢穴的密度及盖度大小顺序为: 小果野芭蕉 (Musa acuminata)群落>白背桐(Mallotus paniculatus)群落>思茅崖豆(Mellettia leptobotrya)群落, 并且热带森林的演替类型显著影响蚂蚁种类总数及巢穴密度, 而对巢穴盖度的影响未达到显著水平; 蚂蚁种类总数、巢穴密度与土壤总有机碳和水解氮显著正相关, 与土壤容重和土壤含水率显著负相关, 但所选择的土壤理化指标与巢穴盖度的相关性均未达到显著水平; 蚂蚁巢穴的空间分布呈随机分布格局。我们的数据表明, 不同演替阶段热带森林所形成的植被类型及土壤环境状况共同影响定居的蚂蚁种类总数与筑巢密度。     

浙江龙王山森林群落物种多度分布特征及其与海拔的关系

虽然大量研究已利用模型拟合的方法对植物群落的物种多度分布(SAD)进行了不同数学模型拟合,但对SAD形状(曲线的偏斜度)如何在环境梯度上连续变化的研究仍然不足; 尤其是森林群落,同一地区不同植被类型群落SAD的模型拟合和形状变化是否一致,仍无明确定论。该研究针对安吉小鲵国家级自然保护区中分布的主要森林植被类型,采用样方调查法,记录了28个20 m × 20 m样方中的物种组成及其个体多度。通过对数级数和对数正态模型对样方中的SAD曲线进行拟合,选择最优模型,并通过Gambin模型中的α值和Weibull模型中的η值反映SAD的形状,以及Weibull模型中λ值反映SAD的变化尺度(物种间个体多度的差异程度),分析海拔高度与SAD的形状和变化尺度之间的关系。结果表明:(1)该地区的森林群落物种多度分布主要符合对数级数模型。(2)当包含所有样方时,α值和η值与海拔高度无显著相关性,λ值与海拔呈显著正相关。(3)针对不同的植被类型,常绿与落叶阔叶混交林中α值和η值与海拔高度呈负相关,但在落叶阔叶林中λ值与海拔高度之间具有正相关关系,而α值和η值与海拔高度之间均无显著相关性。该研究结果表明,不同植被类型SAD的形状变化与海拔之间的关系存在差异,说明海拔对不同植被类型中各物种多度分布具有不同影响。因此,在关于植物群落的物种多度分布及其与影响因子关系的研究中,需要考虑区分不同的植被类型。     

Species Richness,Spatial Variation,and Abundance of the Soil Seed Bank of a Secondary Tropical Rain Forest1

Despite the importance of the soil seed bank in tropical forest regeneration, little is known about spatial variability in species composition and abundance of seeds stored in the soil. To develop sampling methods for comparative studies, we examined species richness, spatial variation, and abundance of germinants from the soil seed bank in a 16 year old secondary, tropical wet forest at La Selva Biological Station, Costa Rica. Surface soil (10 cm deep, 4.7 cm diameter) was collected at the intersection points of a gridded 1 ha plot (10 × 10-m grid, 121 samples) and in a nested 100 m² subplot (2 × 2-m grid, 36 samples). The 1 ha plot had a density of 4535 seeds/m² with 34 species observed. Based on a series of 100 randomized species accumulation curves, a Michaelis-Menten fit predicted a mean species richness of 36.3 species; the number of observed species was close to the predicted asymptote. A nonparametric, first-order jackknife species richness estimator predicted a species richness of 37.0 species. Eighty-five and 95 percent of the observed species richness is contained, on average, within 41 and 74 pooled samples, respectively. Within the 100 m² nested subplot, a density of 5476 seeds/m² was observed, comprising 26 species with an estimated species richness (Michaelis-Menten fit) of 29.1 species. The jackknife species richness estimator predicted a species richness of 36.7 species. For species richness and abundance of both plots, spatial autocorrelation statistics (Moran's I) were not significantly different from zero at lag distances from 2 to 100 m, indicating a random distribution at these spatial scales. For this site, accurate estimates of species composition depend upon the number of samples collected as well as the spatial distribution of sampling effort. Many small samples distributed over a large area provide greater accuracy and precision for estimating species richness of the soil seed bank.     

海南霸王岭热带山地雨林森林循环与树种多样性动态

通过对海南岛霸王岭热带山地雨林的调查 ,研究了热带山地雨林树种多样性特征随森林循环的动态变化规律。结果表明 :( 1 )热带山地雨林森林循环不同阶段斑块在森林景观中所占的面积比例分别是 :林隙阶段 ( G)占 38.5 0 % ,建立阶段 ( B)占 2 8.5 0 % ,成熟阶段 ( M)占 2 7.0 0 % ,衰退阶段 ( D)占 6 .0 0 %。 ( 2 )热带山地雨林中乔木树种的密度随森林循环的变化趋势是由 G→B→M呈现出逐渐增加的趋势 ,以成熟阶段达到最大 ,而到衰退阶段又趋于下降。灌木树种则表现出 G阶段斑块的密度最大 ,B阶段的最小 ,从 B到 M有所增加 ,到 D又稍有下降。 ( 3)热带山地雨林中不同高度级和不同径级的树木的密度在森林循环的不同阶段表现出不同的增减趋势 ,其随森林循环过程呈现出的动态变化可能与不同阶段斑块内的空间、环境及物种生物学特性有关。 ( 4 )热带山地雨林中树木的平均胸径、平均高、平均胸高断面积、平均单株材积随森林循环过程呈现出不断增加的趋势 ,其中平均胸径和平均高随森林循环的变化较为平缓 ,而平均胸高断面积和平均单株材积之变化较为陡急。 ( 5 )热带山地雨林森林循环不同阶段的物种多样性指数不同 ,其中 G和 B阶段的物种丰富度和多样性指数值较接近 ,M阶段的物种丰富度达到最大 ,D阶段则最小。     

Tree Diversity,Forest Structure and Productivity along Altitudinal and Topographical Gradients in a Species-Rich Ecuadorian Montane Rain Forest

We studied the spatial heterogeneity of tree diversity, and of forest structure and productivity in a highly diverse tropical mountain area in southern Ecuador with the aim of understanding the causes of the large variation in these parameters. Two major environmental gradients, elevation and topography, representing a broad range of climatic and edaphic site conditions, were analyzed. We found the highest species richness of trees in valleys <2100 m. Valleys showed highest values of basal area, leaf area index and tree basal area increment as well. Tree diversity also increased from ridges to valleys, while canopy openness decreased. Significant relationships existed between tree diversity and soil parameters (pH, total contents of Mg, K, Ca, N and P), and between diversity and the spatial variability of pH and Ca and Mg contents suggesting a dependence of tree diversity on both absolute levels and on the small-scale heterogeneity of soil nutrient availability. Tree diversity and basal area increment were positively correlated, partly because both are similarly affected by soil conditions. We conclude that the extraordinarily high tree species richness in the area is primarily caused by three factors: (1) the existence of steep altitudinal and topographic gradients in a rather limited area creating a small-scale mosaic of edaphically different habitats; (2) the intermingling of Amazonian lowland plant species, that reach their upper distribution limits, and of montane forest species; and (3) the geographical position of the study area between the humid eastern Andean slope and the dry interandean forests of South Ecuador.     

Enhanced Tree Recruitment Following Logging in Two Forest Reserves in Ghana

We tested if logging enhances the recruitment of tree species by comparing young tree density in areas disturbed by logging with areas unaffected by logging 6 mo after logging in two Forest Reserves in Ghana. Analysis of 46 commercial timber species showed significantly higher postlogging recruitment in felling gaps and skid trails than in areas unaffected by logging. New seedlings substantially exceeded those lost due to logging operations. Species richness was significantly greater in areas disturbed by logging.     

Potential Changes in Tree Species Richness and Forest Community Types following Climate Change

Potential changes in tree species richness and forest community types were evaluated for the eastern United States according to five scenarios of future climate change resulting from a doubling of atmospheric carbon dioxide (CO₂). DISTRIB, an empirical model that uses a regression tree analysis approach, was used to generate suitable habitat, or potential future distributions, of 80 common tree species for each scenario. The model assumes that the vegetation and climate are in equilibrium with no barriers to species migration. Combinations of the individual species model outcomes allowed estimates of species richness (from among the 80 species) and forest type (from simple rules) for each of 2100 counties in the eastern United States. Average species richness across all counties may increase slightly with climatic change. This increase tends to be larger as the average temperature of the climate change scenario increases. Dramatic changes in the distribution of potential forest types were modeled. All five scenarios project the extirpation of the spruce–fir forest types from New England. Outputs from only the two least severe scenarios retain aspen–birch, and they are largely reduced. Maple–beech–birch also shows a large reduction in area under all scenarios. By contrast, oak–hickory and oak–pine types were modeled to increase by 34% and 290%, respectively, averaged over the five scenarios. Although many assumptions are made, these modeled outcomes substantially agree with a limited number of predictions from researchers using paleoecological data or other models. Received 12 May 2000; accepted 20 October 2000.     

Vegetation Structure,Composition, and Species Richness Across a 56‐year Chronosequence of Dry Tropical Forest on Providencia Island,Colombia1

We compared vegetation structure and species richness across a 56‐yr chronosequence of six replicated age classes of dry tropical forest on the island of Providencia, Colombia, in the Southwest Caribbean. Stand age classes were determined using sequential, orthorectified panchromatic aerial photos acquired between 1944 and 1996 and Landsat 7 ETM + satellite imagery from 2000. Along the chronosequence we established 59 plots of 2 × 50 m (0.01 ha) to document changes in species richness, basal area, tree height, stem density, and sprouting ability. All woody trees and shrubs >2.5 cm diameter at breast height (DBH) were censused and measured. Although woody species density reached a peak in stands from 32 to 56 yr old, rarefaction analysis showed that species richness increased linearly with stand age and was highest in stands 56 yr old or greater. Nonparametric, abundance‐based estimators of species richness also showed positive and linear associations with age. Basal area and mean tree height were positively associated with age since abandonment, while sprouting ability showed a negative relationship. Our results indicate rapid recovery of woody species richness and structural characteristics along this tropical dry forest chronosequence.     

Effects of Climate Change on the Potential Species Richness of Mesoamerican Forests

The realized species richness of tropical forests cannot yet be reliably mapped at a regional scale due to lack of systematically collected data. An estimate of the potential species richness (PSR), however, can be produced through the use of species distribution modelling. PSR is interpretable as a climatically determined upper limit to observed species richness. We mapped current PSR and future PSR under climate change scenarios for Mesoamerica by combining the spatial distributions of 2000 tree species as predicted by generalized additive models built from herbaria records and climate layers. An explanatory regression tree was used to extract conditional rules describing the relationship between PSR and climate. The results were summarized by country, ecoregion and protected area status in order to investigate current and possible future variability in PSR in the context of regional biodiversity conservation. Length of the dry season was found to be the key determinant of PSR. Protected areas were found to have higher median PSR values than unprotected areas in most of the countries within the study area. Areas with exceptionally high PSR, however, remain unprotected throughout the region. Neither changes in realized species richness nor extinctions will necessarily follow changes in modelled PSR under climate change. However model output suggests that an increase in temperature of around 3°C, combined with a 20 percent decrease in rainfall could lead to a widespread reduction of around 15 percent of current PSR, with values of up to 40 percent in some moist lower montane tropical forests. The modelled PSR of dry forest ecoregions was found to be relatively stable. Some cooler upper montane forests in northern Mesoamerica, where few species of tropical origin are currently found, may gain PSR if species are free to migrate.     

Zooplankton Distribution in Tropical Reservoirs,South China

The zooplankton of 18 reservoirs of South China was investigated in 2000. 61 Rotifera species, 23 Cladoceras and 14 Copepodas were identified. The most frequent Rotifera genera were Keratella, Brachionus, Trichocerca, Diurella, Ascomorpha, Polyarthra, Ploesoma, Asplanchna, Pompholyx and Conochilus. Bosmina longirostris, Bosminopsis deitersi, Diaphanosoma birgei, D. brachyurum and Moina micrura were typical of Cladocera in the reservoirs. Phyllodiaptomus tunguidus, Neodiaptomus schmackeri and Mesocyclops leuckarti were the most frequent Copepoda and M. leuckarti dominated Copepoda in most reservoirs. High zooplankton species richness with low abundance was characteristic of the throughflowing reservoir, whereas low species richness with low abundance was found in the reservoir with the longest retention time. Relative high abundance and medium species diversity were the distinction of intermediate retention time reservoirs.