锡林郭勒草原灌丛化对灌丛间地草本群落物种多样性和生物量的影响

目的灌丛化是全球性的热点问题，草原区灌丛化必然会改变草原生态系统的结构与功能。本文通过研究灌丛化对群落的物种多样性及生物量的影响，对后续治理和控制草原区灌丛化提供参考依据。方法对内蒙古锡林郭勒典型草原区灌丛化样地进行群落生态学调查，依据灌丛特征及灌丛间地草本群落特征，提出典型草原灌丛化指数（TSSEI），并对草原灌丛化等级进行划分，分别定义为轻度灌丛化草原（Ⅰ级）、中度灌丛化草原（Ⅱ级）和重度灌丛化草原（Ⅲ级）；对不同灌丛化等级样地内的灌丛特征指标、灌丛间地草本植物群落的α多样性指数及草本群落的生物量进行单因素方差分析、Pearson相关性分析、LSD多重比较分析。结果通过分析发现:（1）Ⅰ级与Ⅱ级灌丛化样地之间的丰富度指数、Shannon-Wiener指数和Simpson多样性指数均无显著性差异，但是均显著高于Ⅲ级灌丛化样地，即当灌丛化程度从中度灌丛化向重度灌丛化发展时，灌丛间地群落的物种多样性是显著降低的，重度灌丛化样地灌丛间地群落的物种多样性最低。（2）不同灌丛化等级样地中的灌丛间地地上生物量与灌丛间地枯落物的质量均无显著性差异；灌丛间地地下生物量与灌丛间地总生物量在Ⅱ级灌丛化样地中最低，Ⅲ级灌丛化样地中最高，其中Ⅰ级灌丛化样地的灌丛间地地下生物量和灌丛间地总生物量与Ⅱ级和Ⅲ级灌丛化样地无显著差异。（3）TSSEI与Shannon-Wiener指数和Simpson指数呈极显著负相关（P < 0.01），与丰富度指数呈显著负相关（P < 0.05），与Pielou均匀度指数呈极显著正相关（P < 0.01）；TSSEI与灌丛间地草本群落的地上生物量、地下生物量、灌丛间地枯落物及灌丛间地总生物量均无显著相关性。结论研究认为，典型草原轻度及中度灌丛化对于灌丛间草本群落物种多样性并不构成显著影响，重度灌丛化将显著降低灌丛间地草本群落物种多样性。典型草原灌丛化对灌丛间草本群落地上生物量及枯落物质量没有显著影响，重度灌丛化样地的草本群落地下生物量及总生物量显著高于中度灌丛化样地。典型草原灌丛化现象显著影响灌丛间地草本群落的物种多样性，而对于灌丛间地草本群落的生物量的影响较小，均不存在显著相关性。 

Effects of shrub encroachment in Xilin Gol Steppe on the species diversity and biomass of herbaceous communities in shrub interspaces area

ObjectiveThe occurrence of shrub encroachment in typical steppe areas will inevitably change the ecosystem structure and functions. In this paper, researching how the species diversity and biomass of grassland communities response to the shrub encroachment, to provide reference for subsequent management and control of shrub expansion in grassland areas.MethodWe conducted ecological community survey at shrub encroachment sample sites in Xilin Gol typical steppe area. Based on the characteristics of shrubs and herbaceous communities between shrubs, the typical steppe shrub encroachment index (TSSEI) was proposed and classified the shrub encroachment grade, defined as slightly, moderately, and severely shrub encroachment grassland, respectively. One-way ANOVA, Pearson correlation analysis and LSD multiple comparative analysis were conducted on the shrub characteristic index, the α diversity index of herbaceous community and the biomass of herbaceous community in different shrub encroachment level plots.ResultThrough analysis, it was found that: (1) there was no significant difference in richness index, Shannon-Wiener index and Simpson diversity index between grade I and grade II shrub encroachment plots, but they were significantly higher than grade III plots. With the development of shrub from moderate to severe, the species diversity of herbaceous community decreases gradually. Though, the species diversity of herbaceous communities was lowest in the severe shrub encroachment plot. (2) There was no significant difference in aboveground biomass and litter quality between shrubs in different shrub encroachment plots; underground biomass and total biomass of shrub interspaces areas were the lowest in grade II and the highest in grade III shrub encroachment plots. The belowground biomass and total biomass of shrub interspaces of grade I plots, have no significant difference with grade II and III shrub plots. (3) TSSEI was negatively correlated with Shannon-Wiener index and Simpson index (P < 0.01), negatively correlated with richness index (P < 0.05), and positively correlated with Pielou evenness index (P < 0.01). There was no significant correlation between TSSEI and aboveground biomass, underground biomass, litter and total biomass of herbaceous community in shrub interspaces. ConclusionThe results showed that slight and moderate shrub encroachment of typical steppe had no significant effect on species diversity of herbaceous community among shrubs, and severe shrub encroachment would significantly reduce species diversity. The expansion of shrubs had no significant effect on aboveground biomass and litter mass of herbaceous community. The underground biomass and total biomass of herbaceous community in severe shrub encroachment plots were significantly higher than that in moderate plots. The shrub expansion in typical grassland significantly affected the species diversity of herbaceous communities in shrub interspaces area, but had little effect on the biomass of herbaceous communities.