围封对温带半干旱典型草原群落种间关联的影响

Effects of exclosure on community inter-specific relationships in a typical temperate grassland

为明确围栏封育对温带典型草原群落物种种间关系的影响,运用方差比率法、基于2×2列联表的χ^2检验、Ochiai指数、Spearman相关分析,对位于内蒙古锡林郭勒盟太仆寺旗封育6年的围封样地及围栏外样地的主要优势种及伴生种进行了种间关联和相关性分析。同时运用生态位宽度指数分析围栏内外物种对环境资源的利用能力及种间竞争情况。结果表明：1）基于2×2列联表的χ^2检验结果表明围栏内9个种对显著正联结,4个种对显著负联结（p≤0.05）,围栏外有19个种对显著正联结,8个种对显著负联结;Spearman秩相关分析表明围栏内有10个种对显著正相关,16个种对显著负相关,围栏外有12个种对显著正相关,30个种对显著负相关。χ2检验和Spearman检验结果表明围栏内群落处于稳定发展状态,而围栏外群落处于退化阶段。2）围栏内外的优势种Ochiai指数都较高,但χ^2检验并不显著,表明优势种之间的关联程度高,但存在相对独立的分布格局。3）围栏内主要优势种的生态位宽度大于围栏外,说明围栏封育保护了主要优势种的生长。

Aims This study aimed to understand the impact of exclosure on interspecific associations of species in a typical temperate grassland. We compared the species associations of dominant and companion species in grassland plots with the six-year exclosure and grazing in Taips County, Nei Mongol. Methods We selected 14 species according to important values in each plot, using variance ratio to analyze the overall association. The χ~2 test with 2 × 2 contingency table, Ochiai index and spearman rank correlation test were applied to analyze the inter-specific associations of dominant and companion species. We used the niche breadth index to analyze the ability of resource utilization of species and inter-specific competition for grazed plots and ones with exclosure. Important findings The inter-specific associations among 91 species pairs inside the exclosure showed that nine species pairs were significantly positive but 4 pairs were negative based on the χ^2 test with 2 × 2 contingency table. Ten species pairs had significantly positive correlations and 16 species pairs were negative through the Spearman correlation test. For the plots outside the exclosure, we found 19 species pairs were positively associated but 8 pairs were negative associated using the χ^2 test, and 12 species pairs were significantly positively correlated but 30 pairs were negatively correlated using the Spearman correlation test. The results indicated that the community inside the exclosure was in a continuous development state while the outside community was degradating. The Ochiai indices of dominant species were high both inside and outside the exclosure but the differences using the χ^2 test were nonsignificant. It implied that there was some connection among dominant species but their patterns of distribution were relatively independent. The niche breadth for dominant species inside the exclosure was higher than ones outside, which suggested the exclosure has an important role in protecting dominant species.