不同刈割频度对大针茅草原群落特征及土壤元素含量的影响

在草原生态系统中,土壤是植物生长发育最重要的基质,对植物群落动态有显著的影响。刈割是内蒙古典型草原区除放牧外最重要的利用方式。研究不同刈割频度对典型草原区群落特征和若干土壤性质的影响及土壤因子与群落特征的相关性,旨在得出对群落多样性最有利并最适宜生产利用的刈割频度。研究区设置在内蒙古锡林浩特市东部以大针茅建群的典型草原;在2009—2013年进行不同频度的刈割处理,共设置处理,一年两次刈割、一年一次刈割、两年一次(割一年休一年)刈割、围封,在2013年8月采集测定土壤养分的样品。刈割对群落多样性影响显著,割一年休一年Shannon-Wiener多样性指数、Pielou均匀度指数、丰富度指数均高于其他刈割处理(P0.05);不同频度刈割下,一年两次刈割处理下土壤20—30cm和30—40cm的有机质含量显著高于其他处理(P0.05);不同频度刈割处理下土壤中的速效磷和速效氮的含量没有显著差异;一年两次处理的土壤全氮含量显著高于其他处理(P0.05)。Shannon-Wiener多样性指数与有机质含量、全氮含量呈显著负相关;Pielou均匀度指数与土壤元素间无显著相关关系;Richness指数与有机质含量呈显著负相关,与全氮含量为极显著负相关关系。割一年休一年刈割处理下土壤元素含量呈现更好的状态,结合群落物种多样性及生产利用的角度,割一年休一年为最合理的刈割频度。

Effects of different mowing frequency on the community characteristics and soil element contents in a Stipa grandis steppe ecosystem

In grassland ecosystems, soil is the most important substrate for plant growth and has a significant impact on Plant community dynamics. Mowing is the most important way to use steppes in Inner Mongolia, except for grazing. In the present study, the impact of different mowing frequencies on the community characteristics and soil properties, and the correlation between soil factors and community characteristics were studied. The aim was to determine the most efficient and suitable mowing system for enhanced productivity and community diversity. The study area is a typical steppe primarily based on Stipa grandis, located in the Maodeng pasture of eastern Xilinhaote City, Inner Mongolia, the mowing frequency were set four gradient(TAY:Twice a year;OAY:Once a year; OTY:Once two year; NM:No mowing). Different mowing treatments were conducted in 2009-2013, soil samples were collected and analyzed in August 2013. The results indicated that the mowing treatments significantly affected plant community diversity(P<0.05). The Shannon-Wiener diversity index, Pielou evenness index, and species richness index for the mowing once-in-two-years treatment were higher than those for the other treatments. The organic matter contents of 20-30 cm and 30-40 cm soil in the mowing twice-in-one-year treatment were significantly higher than those in other treatments(P<0.05). There were no significant differences in the available nitrogen and phosphorus contents of soil between the different treatments. In addition, the soil total nitrogen in the mowing twice-in-one-year treatment was significantly higher than that in other treatments(P<0.05). The correlation analysis showed the Shannon-Wiener diversity and species richness indices were significantly negatively correlated with organic matter and total nitrogen contents, where as the Pielou evenness index had no correlation with soil element content, Richness index was significantly negatively correlated with total nitrogen content and organic matter content. Fencing was significantly beneficial to soil nutrients, but not conducive to the growth of dominant species, plant community species diversity, and increasing the plant community density. Combining the results for species diversity and production, an annual mowing interval was the most efficient mowing method for the steppe ecosystem.