雅鲁藏布江中游河谷风沙化土地砂生槐群落结构特征

基于样方调查和等级聚类分析,研究了雅鲁藏布江中游风沙化土地不同恢复演替阶段砂生槐群落的结构特征.结果表明:雅鲁藏布江中游风沙化土地植物群落可分为砂生槐群落、固沙草群落、砂生槐＜固沙草群落、砂生槐-固沙草群落、藏沙蒿+砂生槐群落和砂生槐+藏沙蒿群落6种类型.自然恢复演替从流动沙丘上分布的砂生槐对流沙的初步固定开始,随后固沙草开始侵入群落,逐渐形成了砂生槐-固沙草群落.另一种演替途径开始于固沙草群落,砂生槐在演替过程中出现在固沙草群落中,最后亦达到砂生槐-固沙草群落阶段.在一些半固定沙地阶段,藏沙蒿开始侵入群落,形成砂生槐+藏沙蒿群落.雅鲁藏布江风沙化土地的顶极群落是以砂生槐为优势种的灌丛群落.随着坡度增加,砂生槐群落盖度和高度有降低的趋势.生物结皮对土壤的理化性质有一定的改善作用,结皮覆盖处土壤水分含量显著高于其他演替阶段的表层土壤水分含量.流动沙地砂生槐灌丛冠幅、株高和萌蘖枝数量最高,其次是固定沙地,半固定沙地最低.各阶段枯死枝数量说明固定沙地阶段以后砂生槐种群有衰退的趋势.     

群落生态学与有害生物防治(四):群落演替与群落多样性

一、演替的概念和类型群落也像个体一样具有由低级到高级、由简单到复杂的发育过程,具有发生、发展和消亡的新陈代谢过程。这种在同一地带由不同发育阶段的群落彼此替代的现象,称为演替。其中一系列先后出现的演替阶段,称为演替系列。演替的起因涉及内因和外因。内因主要是随着群落的发展,引起内部环境和种间竞争关系的变化;外因是自然因素的改变和人为干预以及外来种的入侵。由于不同生物的生态幅度不同,环境的改变就导致群落中优势种类的改     

浙江东部常绿阔叶林次生演替的随机过程模型

 植物群落次生演替过程的有限序列在一定意义上构成一随机过程。浙江东部常绿阔叶林次生演替的随机过程系统可以近似地看成线性系统,因而可以用马尔可夫过程描述。本文以群落主要乔木优势种作为马尔可夫过程的状态变量。用“空间序列代替时间序列”的研究方法测得自然次生演替过程和干扰次生演替过程群落主要优势乔木种的更新概率,以此建立了马尔可夫过程的一步平稳转移概率矩阵。应用马尔可夫链模型对常绿阔叶林的自然和干扰次生演替过程进行了模拟。模型还给出了次生演替过程群落主要优势乔木种类的数量动态,为深入研究常绿阔叶林次生演替规律以及林业生产和管理等提供了依据。     

人为干扰对小果野芭蕉群落生物量及多样性的影响

采用标准木法和回归分析法（乔木层）研究了小果野芭蕉群落在演替吕不同的压力条件下生物量和多样性的变化,结果显示,小果野芭蕉的侵入在正常情况下对群落生物量的影响并不显著,但由于人为干扰,可以明显地降低群落生物量。人为干扰是小果野芭焦群落长期保持在一个种群数量较大,物种多样性指较低和重要值较大的状态。轮歇丢荒地小果野芭蕉的侵入和迅速发展,是群落恢复演替过程中一种正常的途径。因此保持小果野芭蕉群落不受人为干扰是使其沿正常演替途径恢复的一种可行方法。     

青藏高原东部植物种子萌发能力与其在群落中相对多度的关系

不同演替阶段的群落中植物幼苗建植特性以及幼苗建植时所处的环境都会有所不同.这些差异可能会导致种子萌发率与物种多度之间的关系随着群落的演替阶段而发生改变.目前关于不同类型群落中以及同一类型群落的不同演替阶段物种多度和种子萌发能力之间的关系的研究较少.本研究以全面收集的青藏高原东缘3种常见次生植被(鼢鼠土丘群落、人工草地群落和弃耕地群落)中植物种子为基础,沿着群落演替梯度来探明种子萌发和物种多度之间的关系.通过对结果的线性回归分析发现:在鼢鼠土丘群落和人工草地群落中,种子萌发率和物种多度之间无显著相关性;而在弃耕地群落中,种子萌发率和物种多度之间的关系有随着群落的演替呈现由正相关向负相关转变的趋势.     

浙江东部常绿阔叶林次生演替的随机过程模型

植物群落次生演替过程的有限序列在一定意义上构成一随机过程。浙江东部常绿阔叶林次生演替的随机过程系统可以近似地看成线性系统,因而可以用马尔可夫过程描述。本文以群落主要乔木优势种作为马尔可夫过程的状态变量。用“空间序列代替时间序列”的研究方法测得自然次生演替过程和干扰次生演替过程群落主要优势乔木种的更新概率,以此建立了马尔可夫过程的一步平衡转移概率矩阵。应用马尔可夫链模型对常绿阔叶林的自然和干扰次生演     

植物群落演替的线性与非线性系统及数字预测

一、关于演替的线性与非线性的概念 植物群落的演替过程是一个系统。植物群落的演替的各个阶段,就是一个一个的子系统,亦即状态。在一定条件下,它可以由一种状态(原象)转移到另一种状态(映象),这种状态转移的过程就是所谓的演替系统,这种由各种状态或者子系统组成的系列,就构成了植物群落的演替系统。     

广西的南桦林和西桦林及其演替趋向

在亚热带地区,当常绿阔叶林或山地常绿落叶阔叶混交林被砍伐后,桦木常常迅速侵入并发展成林,构成亚热带落叶阔叶林的一种重要类型,在自然发展过程中,它们又将向原来的森林类型恢复和演变。本文重点介绍了广西南桦林和西桦林的一些群落类型及其演替替向、期待发挥它们在林业建设中应有的作用。     

鼢鼠土丘植物群落演替生态位动态及草地质量指数

采用"空间代替时间"的方法,以不同演替系列的鼢鼠土丘植物群落为对象,通过种群生态位动态和功能群变化探讨其演替机制.选取20个主要群落组分种,采用Shannon生态位宽度和Pianka生态位重叠指数进行定量分析.结果表明:较大的生态位宽度常伴随着较大的生态位重叠,但一些具较小生态位宽度的物种之间也存在着较大的生态位重叠;物种之间的生态位重叠普遍较大.功能群变化分析表明:随着演替的进行,1、2年生杂草先迅速减小后缓慢增大,但总体减小;多年生杂草先增大后减小;多年生禾草类线性增加.反映了多年生禾草类最终在演替顶极群落中占据主导地位.采用草地质量指数分析了鼢鼠土丘植被状况,表明随着演替的进行,草地质量指数显著增加.     

高原鼢鼠土丘对矮嵩草草甸植被演替及土壤营养元素的作用

本文研究了矮蒿草草甸上高原酚鼠土丘的出现率及其对植被的覆盖状况,土丘高度的下降及其直径的变化,土丘植物地上生物量和土丘营养元素含量。高原鼢鼠土丘出现率为242个/只/年,合土壤干重为1023.82公斤/只/年,对植被的覆盖面积高达22.53平方米/只/年。土丘在地表滞留时间约1年,处于不同演替阶段植被区域内出现的土丘,其植物地上生物量间的差异显著。5月前,在原生植被区出现的土丘,经4个月后,土丘边缘形成环状富草区,士丘边缘至中心区形成环状贫草区,而土丘中心仍处于无草状况。在次生植被区上的土丘则无此现象。新土丘除速效钾的含量与对照区无显著差异外,速效氮、磷的含量显著地高于对照区。旧土丘土壤中的速效氮、磷、钾含量均低于新土丘,但氮、磷的含量仍高于对照区。     

水磨河底栖动物群落结构的生态位分析

本文利用生态位理论,对水磨河6个站点,讨论了14个优势种的群落结构与水体污染之间的关系,在r—k连续统中进行种的生态位排序,通过聚类分析绘出底栖动物群落树状图,将水磨河底栖动物群落分成四个集群类型和一个边缘种,并叙述了其污染生态学特性和生态对策。       

Pollination niche separation in a winter annual community

Summary Differences in major selective forces important in early and late successional communities should influence niche breadth and degree of overlap. Early successional species may not experience consistent, strong selection against competition and can be expected to have broader niches with more overlap than later successional species. This paper presents data from 2 early successional winter annuals that show clear niche separation under conditions in which coevolution is unlikely. Lactuca scariola L. and Erigeron annuus (L.) Pers. flower in mid-summer and attract the same insect visitors. Erigeron, the more common species, begins to flower in mid-morning when insect visitors are quite active. Lactuca flowers open earlier in the morning and close just before Erigeron flowers open. The early morning hours are not optimum for Lactuca visitation, as most of the visits occur just before floral closing. Both species can selffertilize without a vector, and Lactuca was introduced from Europe. It is, therefore, not possible that niche separation inflowering time and subsequent time of visit in Erigeron and Lactuca is a result of coevolutionary niche differentiation between the two species. This separation is likely to be a preadaptation resulting from coevolution with other species.     

Niche and Neutral Processes Together Determine Diversity Loss in Response to Fertilization in an Alpine Meadow Community

Fertilization via nutrient deposition and agricultural inputs is one of the most important factors driving decreases in plant diversity. However, we still do not fully understand which processes (niche process or neutral process) are more important in leading to decreases in plant diversity caused by fertilization. A hypothesis-based approach was used to test the relative importance of niche versus neutral processes along a fertilization gradient in an alpine meadow community on the eastern Tibetan plateau, China. Niche overlap values were calculated for species biomass, and the null model was used to generate the values of niche overlap expected at random. A linear regression modeling was used to evaluate the relationship between functional traits (specific leaf area, leaf dry matter content, and leaf total nitrogen concentration) and species relative abundance. Our results demonstrated that observed niche overlap for species biomass was significantly higher than expected at lower fertilization gradients. Moreover, we also found a significantly negative correlation between species relative abundance and specific leaf area and leaf dry matter content, but a significantly positive correlation between relative abundance and leaf nitrogen concentration at lower fertilization gradients. However, these relationships were not significant at higher fertilization gradients. We concluded that community assembly is dynamic progression along the environmental gradients, and niche and neutral processes may together determine species diversity loss in response to fertilization.     

缙云山大头茶(Gordonia acuminata)生态位研究

基于四川缙云山森林群落演替系列群落取样, 采用Ｌｅｖｉｎｓ 生态位宽度、Ｆｅｉｎｓｉｎｇ 和Ｓｐｅａｒｓ相似性比例生态位宽度及Ｌｅｖｉｎｓ 生态位重叠、Ｐｅｔｒａｉｔｉｓ 生态位重叠等计测公式, 对大头茶（ Ｇｏｒ ｄｏｎｉａ ａｃｕｍｉｎａｔａ） 种群的生态位特征及动态进行了研究。结果表明, 大头茶种群生态位宽度在演替系列群落中由小到大再减小, 它与缙云山森林群落其它优势乔木种群的生态位特定重叠主要表现在同针叶林中的川灰木（ Ｓｙｍｐｌｏｃｏｓ ｓｅｔｃｈｕｎｅｎｓｉｓ） 、杉木（ Ｃｕｎｎｉｎｇｈａｍｉａ ｌａｎｃｅｏｌａｔａ） 、马尾松（Ｐｉｎｕｓ ｍａｓｓｏｎｉａｎａ） 种群上; 反之, 其它优势乔木种群在大头茶种群上的生态位特定重叠在大头茶纯林中表现较显著; 从总体上, 所选１５ 个优势种群在各类群落中均不表现出显著的生态位普遍重叠。反映了大头茶种群在缙云山森林群落演替中的先锋拓殖作用, 亦为其常绿阔叶林的重要种群之一, 但它更重要的是一森林群落演替过渡类型的优势种群。     

Shifts in Climate Foster Exceptional Opportunities for Species Radiation: The Case of South African Geraniums

Climate change is often assumed to be a major driver of biodiversity loss. However, it can also set the stage for novel diversification in lineages with the evolutionary ability to colonize new environments. Here we tested if the extraordinary evolutionary success of the genus Pelargonium was related to the ability of its species to capitalize on the climate niche variation produced by the historical changes in southern Africa. We evaluated the relationship between rates of climate niche evolution and diversification rates in the main Pelargonium lineages and disentangled the roles of deep and recent historical events in the modification of species niches. Pelargonium clades exhibiting higher ecological differentiation along summer precipitation (SPP) gradients also experienced higher diversification rates. Faster rates of niche differentiation in spatially structured variables, along with lower levels of niche overlap among closely related species, suggest recent modification in species niches (e.g. dispersal or range shift) and niche lability. We suggest that highly structured SPP gradients established during the aridification process within southern Africa, in concert with niche lability and low niche overlap, contributed to species divergence. These factors are likely to be responsible for the extensive diversification of other lineages in this diversity hot spot.     

Correspondence of seed traits with niche position in glacier foreland succession

Changes in species composition during succession are driven by biotic and abiotic factors leading to a multitude of niches occupied by distinct species. Gradient analyses of plant communities provide opportunities to approximate the niche position of species along a successional gradient. Several plant traits have been used to explain mechanisms governing successional sequences, but generalising changes in species traits during primary succession is still controversial. This study examined whether the seed mass and the optimum temperature for germination could explain the niche position of several glacier foreland species along a primary successional gradient in the Austrian Central Alps. We hypothesised that pioneer species should possess lighter seeds and a lower optimum temperature for germination than late successional species. We found significant differences in the seed mass between species, but the seed mass did not correspond with the assigned niche position on the successional gradient. Germination responses to temperature also differed significantly between species. Pioneer species performed better at lower temperatures than late successional species, suggesting that the optimum temperature for germination is a driver of niche separation. We discuss the interactions between seed traits and environmental conditions along the primary successional gradient emphasising the importance of temperature requirements for the germination. Differences in the regeneration characteristics are a major cue governing species turnover in glacier foreland succession.     

Joint effect of phylogenetic relatedness and trait selection on the elevational distribution of Rhododendron species

Congeneric species may coexist at fine spatial scales through niche differentiation, however, the magnitude to which the effects of functional traits and phylogenetic relatedness contribute to their distribution along elevational gradients remains understudied. To test the hypothesis that trait and elevational range overlap can affect local speciesʼ coexistence, we first compared phylogenetic relatedness and trait (including morphological traits and leaf elements) divergence among closely related species of Rhododendron L. on Yulong Mountain, China. We then assessed relationships between the overlap of multiple functional traits and the degree of elevational range overlap among species pairs in a phylogenetic context. We found that phylogeny was a good predictor for most functional traits, where closely related species showed higher trait similarity and occupied different elevational niches at our study site. Species pairs of R. subgen. Hymenanthes (Blume) K. Koch showed low elevational range overlap and some species pairs of R. subgen. Rhododendron showed obvious niche differentiation. Trait divergence is greater for species in R. subgen. Rhododendron, and it plays an important role between species pairs with low elevational range overlap. Trait convergent selection takes place between co-occurring closely related species that have high elevational range overlap, which share more functional trait space due to environmental filtering or ecological adaptation in more extreme habitats. Our results highlight the importance of evolutionary history and trait selection for species coexistence at fine ecological scales along environmental gradients.     

三峡库区消落带现存草本植物组成与生态位

为揭示经历长期水位变动后,三峡水库消落带优势植物对可利用资源的分享状况、不同资源环境下植物种群生态位特征以及植物种间竞争和共存机制,对三峡库区秭归段典型消落带现存优势草本物种的种群空间格局及生态位特征进行研究.结果表明: 该区共有草本植物39种,隶属18科32属,以禾本科、菊科、蓼科和大戟科植物为主;狗牙根、狗尾草、狼把草和毛马唐具有较大的重要值和生态位宽度,为主要优势种;海拔145～155 m段植物生态位宽度前3位依次为狗牙根＞酸模叶蓼＞狗尾草;海拔155～165 m段植物生态位宽度前3位依次为狗尾草＞毛马唐＞狗牙根;海拔165～175 m段植物生态位宽度前3位依次为狗尾草＞狼把草＞红蓼;不同海拔物种间生态位重叠均保持较高状态,生态位宽度较小物种也可与生态位宽度较大物种有较大的生态位重叠值,仅凭生态位宽度不能判定生态位重叠值.消落带经历7次水位涨落周年后,大多数优势物种为一年生草本植物,生态位分化程度较低,在资源匮乏且不稳定的生境中种间竞争强烈,消落带植被仍处于群落演替的初级阶段.     

Temporal variation in spatial organization of a rodent community in the southwestern Kyzylkum desert (Middle Asia)

The distribution of niches in resource space and the niche patterns of a 14-species community of Middle Asian desert rodents were studied during two years - at low and high rodent density - using discriminant function analysis Nineteen quantitative environmental parameters (soil structure and vegetation), measured in 550 plots within 22 1 -ha grids, were considered The first three canonical axes of resource space account for 72% of the variance The first two axes represent complex environmental gradients the first axis represents a general landscape gradient from sand to clay soils, the second axis reflects a gradient of in creasing productivity The third axis reflects with in-habitat environmental variation All community parameters, as well as parameters of individual species niches, were unstable between years At the same time, different parameters vary in different extent Position of niche centroids along macro-habitat axes, as. well as macrohabitat niche breadth, were relatively stable between years, but these parameters for microhabitat axis and values of niche overlap were much more variable A strong correlation between changes m relative between-habitat niche breadth and differences in average niche overlap with relative changes in species abundances indicate density dependence of these parameters Changes in niche overlap is a consequence of between-year differences in guild patterns Guild structure was pronounced at high density when the level of niche overlap was intermediate At low density, when the level of niche overlap decreased, guild structure was incon-spicous Different levels of diversity differed in their sensitivity to density changes α-diversity was relatively constant as a result of between-year stability of niche centroid positions However level of ß-diversity varied significantly between years reflecting changes in the level of niche overlap, because a decrease in niche overlap leads to an increase in the rate of species turnover     

高寒小嵩草草甸暖季草场主要植物种群的生态位

对高寒小嵩草草甸不同放牧强度下20种植物种群的优势度、生态位宽度及生态位重叠规律进行了研究。结果表明,经过2年的放牧实验,对照、轻度和中度放牧组的主要优势种均为小嵩草和垂穗披碱草,重度放牧组的主要优势种为鹅绒委陵菜和阿拉善马先蒿;由于小嵩草、矮嵩草和线叶嵩草具有耐牧和耐践踏等生物学特点,它们的生态位宽度很大（0．938,0．824,0．815）;垂穗披碱草由于其耐牧和耐旱性较差,生态位宽度相对较小（0．805）,且青海野青茅、异针茅、针茅、紫羊茅和双叉细柄茅等禾本科牧草的生态位宽度在放牧强度梯度上均较小（0．226,0．448,0．445,0．608,0．605）,说明放牧抑制了高大禾草层片的发育,为植株矮小的莎草科牧草的生长创造了条件;异针茅和针茅之间、甘肃马先蒿和阿拉善马先蒿之间生态位重叠较小（0．500,0．572）,这是种间对资源利用上分化的结果。分布于放牧演替系列2个极端的种群间生态位重叠较小,表明物种的分布是既间断又连续的。