Institute of Desertification Studies, Chinese Academy of Forestry, Beijing, China.
PLoS One. 2013 Jul 26;8(7):e69970. doi: 10.1371/journal.pone.0069970. Print 2013.
The western Ordos Plateau is a key area of shrub diversity and a National Nature Reserve of endangered shrub species in north-west China. Desert expansion is becoming the most important threat to these endangered species. However, little is known about the effects of sand burial on the dynamics of the shrub community. This study aims to investigate how the shrubs as a community and as different individual shrubs respond to the disturbances caused by the desert expansion. The approach used by this study is to separate the seed-dispersal strategy from the sand-burial forces that are involved in structuring the shrub communities at different disturbance stages. Four communities for different disturbance stages were surveyed by using 50×50 m plots. The individual shrubs were classified into coloniser and successor groups at the seed-dispersal stage and strong and weak sand-burial tolerance groups at the sand-expansion stage. We employed spatial point pattern analysis with null models for each community to examine the seed-dispersal strategy and sand-burial forces affecting community distribution patterns. At the seed-dispersal stage, the interactions between the colonisers and the successors showed significant positive correlation at a scale of 0-1 m and significant negative correlation at a scale of 2 m; significant negative correlations between the groups with strong and weak sand-burial tolerance in the early stage of sand expansion at scales of 3-6 m, and significant positive correlation in the later stage of sand expansion at a scale of 13 m, were found. Seed-dispersal strategy is a reasonable mechanism to explain the shrub community pattern formation in the earlier stages, whereas sand burial is the primary reason for the disappearance of shrubs with weak sand-burial tolerance, this irreversible disturbance causes homogenisation of the community structure and produces aging populations of shrub species. This has an important influence on the succession direction of desert shrub communities.
鄂尔多斯高原西部是灌木多样性的关键区域，也是中国西北地区受威胁灌木物种的国家自然保护区。沙漠扩张正成为这些濒危物种的最重要威胁。然而，对于沙埋对灌木群落动态的影响知之甚少。本研究旨在调查灌木群落作为一个整体以及不同个体灌木如何应对沙漠扩张引起的干扰。本研究采用的方法是将种子扩散策略与参与不同干扰阶段灌木群落结构形成的沙埋力分开。通过使用 50×50 m 的样本来调查四个不同干扰阶段的群落。个体灌木在种子扩散阶段分为殖民者和后继者群体，在沙扩张阶段分为强沙埋和弱沙埋耐受群体。我们对每个群落都采用了空间点格局分析和空模型，以检验影响群落分布模式的种子扩散策略和沙埋力。在种子扩散阶段，殖民者和后继者之间的相互作用在 0-1 m 尺度上呈显著正相关，在 2 m 尺度上呈显著负相关；在沙扩张的早期阶段，强沙埋和弱沙埋耐受组之间在 3-6 m 尺度上呈显著负相关，在沙扩张的后期阶段在 13 m 尺度上呈显著正相关。种子扩散策略是解释早期阶段灌木群落模式形成的合理机制，而沙埋是导致弱沙埋耐受性灌木消失的主要原因，这种不可逆转的干扰导致群落结构同质化，并产生灌木物种的老龄化种群。这对沙漠灌木群落的演替方向有重要影响。
