干旱与半干旱区红砂枯落物分解初期节肢动物群落结构特征

选择宁夏盐池半干旱区和内蒙古乌拉特后旗干旱区荒漠草原为研究样地，以红砂枯落物为研究对象，利用网孔分解袋法，在灌丛内外微生境布设分解袋。通过调查分解袋中节肢动物群落组成与多样性分布特征，结合枯落物化学分析和土壤环境因子测定，研究灌丛微生境红砂枯落物分解初期节肢动物群落结构分布规律。结果表明：1）红砂枯落物节肢动物优势类群在盐池半干旱区灌丛中有3类，裸地中仅2类；而在乌拉特后旗干旱区表现为灌丛内外优势类群均有3类。常见类群在盐池半干旱区灌丛中有7类，而裸地中仅3类；而乌拉特后旗干旱区灌丛中有7类，裸地中有4类。稀有类群在盐池半干旱区表现为仅在裸地出现，而乌拉特后旗干旱区表现为仅在灌丛内出现。2）红砂枯落物节肢动物个体数和类群数在盐池半干旱区均表现为裸地显著高于灌丛，而在乌拉特后旗干旱区均表现为裸地显著低于灌丛（P<0.05）。红砂枯落物节肢动物Shannon-Wiener指数、Simpson指数、Margalef指数以及Pielou指数在盐池半干旱区和乌拉特后旗干旱区均表现为灌丛内外无显著差异（P>0.05）。3）红砂枯落物节肢动物个体数在盐池半干旱区仅与土壤pH值呈显著正相关性，而与土壤砂粒含量呈显著负相关性；类群数在盐池半干旱区仅与土壤砂粒呈显著负相关性（P<0.05）。在乌拉特后旗干旱区红砂枯落物节肢动物个体数和类群数与环境因子间均无相关性（P>0.05）。冗余分析（RDA）和偏RDA分析结果表明，枯落物K含量是影响干旱与半干旱区红砂枯落物节肢动物个体数分布的主要环境因子。4）综合表明，红砂枯落物节肢动物个体数和类群数受到灌丛微生境和气候因子的双重影响，但群落多样性受灌丛微生境和气候因子的影响均较小。并且，随干旱程度的加强，灌丛微生境对红砂枯落物节肢动物个体数和类群数分布的影响从溢出效应转变为聚集效应。

The arthropod community structure in Reaumuria soongorica litter at the early stage of its decomposition in arid and semi-arid regions

Two desertified grasslands in semi-arid Yanchi County of Ningxia and in arid Urat Rear Banner of Inner Mongolia were selected as sites to study litter decomposition of Reaumuria soongorica. Litter bags were set up between shrub microhabitats beneath the shrub canopy and in the open spaces. The litter arthropod community composition and diversity were investigated， as well as the litter chemical composition and soil conditions. The objective of the present study was to explore the differences in litter arthropod community composition and diversity between shrub microhabitats in semi-arid Yanchi County and a more arid Urat site. It was found that： 1） There were 3 dominant taxa of litter arthropods beneath shrub canopy and 2 dominant taxa in the open spaces in semi-arid Yanchi； there were 3 dominant taxa in both microhabitats in arid Urat. There were 7 commonly occurring taxa beneath shrub canopy， and 3 found in the open spaces in semi-arid Yanchi； while there were 7 commonly occurring taxa beneath shrub canopy and 4 in the open spaces in arid Urat. Rare species were found in the open spaces only in semi-arid Yanchi， and beneath shrub canopy only， in arid Urat. 2） The abundance and species richness of litter arthropods was found to be significantly higher in the open spaces than beneath shrub canopy in semi-arid Yanchi， but followed the reverse distribution in arid Urat （P<0.05）. There were no significant differences in Shannon-Wiener index， Simpson index， Margalef index， and Pielou index between the two shrub microhabitats at either of the study sites. 3） The abundance of litter arthropods was found to be positively correlated with soil pH and negatively correlated with soil sand content. Species richness was negatively correlated with soil sand content in semi-arid Yanchi only （P<0.05）. The abundance of litter arthropods and species richness were uncorrelated with environmental factors in the arid area of Urat Rear Banner （P>0.05）. From the results of redundancy analysis and partial redundancy analysis showed that litter K content of litter was the main factor driving the distribution of litter arthropods in arid and semi-arid areas. In conclusion， both shrub microhabitats and climatic factors affected the abundance and group richness of litter deposition， while there was little effect on litter arthropod diversity. With increased aridity， there was a transition from an ‘overflow’ effect towards a ‘facilitative’ effect of shrubs on the distribution of litter arthropod abundance and species richness.