1、Q1 群落、结构和稳定性要 点群 落 群落（ community） 是在相同时间聚集在同一地段上的许多物种种群（ species populations） 的集合。它的特性是由个体之间的相互作用如竞争（ competition） 和寄生（ parasitism） 决定的。群落也能够从更广阔的角度和物种多样性（ species diversity）、 食物网（ food-webs）、 能量流（ energy flow） 和同资源种团（ guilds） 中种间的相互作用来观察它的特性。The community is an assemblage of species populations tha
2、t occur together in the same place at the same place at the same time. It has properties determined by the imteractions among individuals such as competition and parasitism. The community can also be viewed from the broader perspective in terms of species diversity, food-webs, energy flow and the in
3、teractions among guilds of species.Key NotesThe communityQ1 THE CPMMUNITY, STRUCTURE AND STABILITY群落结构一个群落的物种多样性取决于群落含有的不同种的数量即种丰富度（ the species richness） 和种多度的均匀性（ the evenness of species abundance）。 多样性指数（diversity indices） 可以通过这两个因子计算出来。表达种丰富和种均匀度综合的另一种方式是通过种的相对多度对种的顺序作图。多样性能够在局域群落（ local communi
4、ty）、 地区（ region） 和最广阔的地理尺度（geographic scale）（ 如大陆）三个不同的空间尺度上测算它。这样就产生了 a、 和 多样性。 The species diversity of a community depends on the number of different species it contains (the species richness) and the evenness of species abundance across species. Diversity indices can be calculated to take into a
5、ccount both of these factors. Another way of representing species richness and evenness together is to plot the relative abundance of species against rank order of species abundance. Diversity can be measured over the three different spatial scales of the local community, the region and the broadest
6、 geographic scale (e.g. the continent). This yields alpha ()-, beta ()-and gamma ()-diversity. Community structure群落边界 群落不会突然中断，而是逐渐的过渡到其他群落，因为各个物种是逐渐受到它们的环境耐受力限制的。这一点可以通过梯度分析来得到证明，梯率分析重点在于物种分布重叠区域。分类和排序的统计方法允许群落的边界在这个连续体上重叠。分类技术分出了生态学上不同的物种或地段，获得了客观等级。排序并不是企图勾画出边界，而是根据它们在分布上的相似性而勾画出物种集团或地段。Communit
7、ies do not end abruptly but grade into one another as individual species encounter the limits of their environmental tolerance. This can be demonstrated through gradient analysis, which focuses on the overlapping distributions of individual species. The statistical methods of classification and ordi
8、nation allow community boundaries to be superimposed on this continuum. Classification techniques separate ecologically different species or sites yielding objective classes. Ordination does not attempt to draw boundaries but groups species or sites according to how similar they are in their distrib
9、utions. Community boundaries同资源种团 同资源种团是许多占据相似生态位的物种组合的集团；如以阔叶树为食物的许多昆虫就形成一个同资源种团。一些研究已经表明，在一个群落内的某些同资源种团中的总物种的比例是不变的。这就表明也许有某一共同的 “规则 ”在统治着群落结构。Guilds are groups of species that occupy similar niches; for example, insects feeding on broad-leaved trees form one guild. Some studies have found constan
10、cy in the proportion of total species in certain guilds within a community. This indicates that there may be certain common rules governing community structure.Guilds群落的复杂性、多样性和稳定性稳定性有两个组成成分 恢复力（ resilience） 和抵抗力（ resistance）。 这两个指标描述了群落在受到干扰后的恢复能力和抵御变化的能力。复杂性被认为是决定群落恢复力和抵抗力的重要因素。然而群落越复杂并不意味着群落越稳定。复杂性增加已经显示会导致不稳定。此外，群落的不同组分（如种丰富度和生物量）也许对干扰有不同反应。具有较低生产力的群落（如冻原）其恢复力是最低的。相反，较弱的竞争可以使许多的物种共存，从而减少群落的不稳定性。
