荒漠草原区柠条灌丛对地面节肢动物群落小尺度空间分布的影响

Effect of shrub cover on small-scale spatial distribution of ground-active arthropod communities in desertified steppe

在宁夏盐池沙地以围栏封育柠条灌丛林为研究对象,在距离灌丛0(即灌丛下,S)、1.5(D1)、7.5(D2)、15 m(D3)处分别设置调查样点,采用陷阱诱捕法调查了地面节肢动物群落小尺度空间分布规律。结果表明,共捕获地面节肢动物11目4科71个类群。在远离灌丛的小尺度空间上,优势类群和常见类群多度呈现相反变化趋势,分别在距离柠条灌丛7.5 m处达到最低(58%)和最高值(34%),而稀有类群多度低于10%,且呈逐渐降低趋势。优势类群数和常见类群的丰富度均少于7个类群,而稀有类群数均超过25个类群,且波动变化较大,在D1和D2处分别达到最高(44)和最低值(25)。地面节肢动物总个体数表现为灌丛下与灌丛外样点间无显著差异性(p>0.05),但远离灌丛的D3显著高于靠近灌丛的D1和D2(p<0.05);总类群数表现为S、D1、D3间均无显著差异性(p>0.05),但均显著高于D2(p<0.05)。冗余分析(RDA)表明土壤粗砂和细砂含量是影响地面节肢动物空间分布的土壤因子,其中土壤细砂含量是主导因素。研究表明,柠条灌丛本身对地面节肢动物空间分布的影响范围小于7.5 m,随着空间距离的增加灌丛对地面节肢动物空间分布的作用逐渐弱化,而在围封条件下远离灌丛(15 m)处封育草地地面节肢动物群落与灌丛下相似。

Taking the Caragana shrub distributed in Yanchi county of Ningxia province as a subject, the sampling point was set at the distance of 0 （beneath the shrub canopy）, 1.5 （D1）, 7.5 （D2）, 15 m （D3） far from the centre of shrub canopy. An investigation on ground-active arthropods from each sampling point was carried out by trapping method in order to discuss the effect of shrub canopy on small-scale spatial distribution of ground-active arthropod communities in desertified steppe. In this study, 71 taxonomical groups were captured, and belonged to four families and 11 orders. Along with the increased distance from the shrub canopy, the abundance of dominant groups followed the reverse pattern to that of common groups, with the maximum and minimum values respectively at the point of 7.5 m far from the centre of shrub canopy, whereas the abundance of rare groups tended to decrease at a low level （〈10%）. The taxa richness of dominant groups and common groups was below 7. However, the taxa richness of rare groups fluctuated much, and indicated maximum and minimum values at the point of 1.5 and 7.5 m far from the centre of shrubs, respectively. As for total abundance of ground-active arthropods, no significant （p〉0.05） difference was found between S and Dl, D2, D3 （p〉0.05）, whereas the total abundance was significantly （p〈0.05） higher at D3 in comparison to D2 and D3 outside the centre of shrub canopy. No significant （p〉0.05） difference in taxa richness was found between S and D1, D3 （p〉0.05）, where a significantly higher value was found compared with the point of D2. Redundant analysis （RDA） indicated that soil coarse sand and fine sand contents were the factors affecting the spatial distribution of ground-active arthropod communities, with the latter as the main determinants. It suggested that the effectiveness of shrub patch on the spatial distribution of ground-active arthropod communities was limited within 7.5 m surrounding shrub canopy, and it declined with increased distance from the shrub canopy. No differences on ground-active arthropod community were found between the microhabitats beneath shrub canopy and at the point of 15 m far away from the centre of shrub cover.