围封和放牧对科尔沁沙地植物群落种间关联的影响

Effects of enclosure and grazing on interspecific association of plant communities in Horqin Sandy Land,Inner Mongolia

为明确围封和放牧对科尔沁沙地植物群落种间关联的影响,在对植物群落进行样方调查的基础上,采用方差比率法(VR)、χ^(2)检验、Ochiai指数、Spearman秩相关分析对种间关联性及相关性进行研究,得出如下结论:(1)围封和放牧改变了群落物种组成,围封群落出现30个物种,主要物种16个;放牧群落出现物种21个,主要物种13个。(2)VR值显示围封和放牧群落总体均呈正关联性,χ^(2)检验表明围封群落正联结显著率大于负联结显著率,主要物种间显著联结率为27.5%,放牧群落仅有显著正联结种对4个,占6.06%,OI值与χ^(2)检验结果基本一致。(3)Spearman秩相关分析表明,围封群落显著正相关对数略高于显著负相关对数,放牧群落则相反,且围封群落显著相关水平种对占比(44.17%)高于放牧群落(12.82%),故围封群落处于稳定发展阶段,而放牧群落处于退化阶段。

Interspecific association is one of the important quantitative and structural characteristics of plant communities.Inter-species linkage analysis is an effective way of understanding the community composition and interspecific relationship.In the Horqin Sandy Land of Inner Mongolia in China,vegetation restoration occurs under proper management regimes in fragile environmental conditions,e.g.,enclosing and non-grazing.However,little is known about the interspecific association in the area.Therefore,a field experiment was performed to examine the effects of enclosure and grazing on interspecific association of plant communities.And we compared the species associations of dominant and companion species in grassland plots with the ten-year enclosure and grazing.In 2014,the grazed and enclosed(ten years)communities were selected as experimental sites.At each site,two parallel 250 m line transects(20 m apart)were established.For each transect,25 sampling points of 1 m×1 m were established at 10 m intervals.At each of the 100 sampling points,the species composition,coverage,and height were surveyed.By analyzing the original data,the interspecific association of species and the overall association of herbaceous community were calculated.Based on the sample survey of plant communities,the interspecific association and correlation were studied by variance ratio method(VR),χ^(2)test,Ochiai index(OI),and Spearman rank correlation analysis.The conclusions are as follows:(1)Both enclosure and grazing changed community species composition,with 30 species and 16 major species appearing in the enclosed community and 21 species and 13 main species in grazing communities.(2)The VR value showed a positive correlation between the enclosing community and the grazing community as a whole.According to theχ^(2)test,the positive association of the enclosing community was higher than that of negative association.The positive association among major species was 27.5%while the numbers of the species with positive association in the grazing community was only 4,accounting for 6.06%.The result of OI value was basically consistent with that ofχ^(2)test results.(3)Spearman rank correlation analysis exhibited that the number of species with positive association of the enclosed community was slightly higher than that of negative association.However,the result of grazed community was completely opposite and the significantly correlated level in the enclosed community(44.17%)was higher than that of the grazing community(12.82%).The results indicated that the enclosed community was in a stable development stage while the grazed community was in a degraded stage.