宁夏麻黄山草原蝗虫及天敌对土壤含水量及坡度的响应特征

为明确宁夏麻黄山蝗虫种群、天敌种群与土壤含水量及坡度之间的关系,于2012年在麻黄山蝗区设置3个样点进行2次调查,使用土壤水分温度速测仪测量不同深度土壤含水量,通过数字高程模型获取坡度数据,以网捕目测法对蝗虫及天敌进行采集,并利用典型性相关分析法分析不同深度土层土壤含水量、坡度与蝗虫物种多样性及种群密度的关系。结果显示,在能够影响蝗虫种群的20~40 cm土层上,首次调查中土壤含水量都体现出坡顶最高、坡底最低的相似趋势;第2次调查中则在不同地形上呈现出多样化。蝗虫物种多样性与20、30 cm土层含水量关系不明显,相关系数仅为0.1306和-0.0157;蝗虫种群密度与20、30 cm土壤含水量关系也不明显,相关系数为0.0077和-0.0118。随着坡度的增加,蝗虫物种多样性与种群密度都有所下降,相关系数分别为0.7223和0.4315;坡度在30°以内的蝗虫物种多样性与种群密度都比较高,超过30°后二者急剧下降。表明在西部干旱、半干旱草原地区,土壤含水量对蝗虫种群的空间分布没有决定性影响,而坡度是影响蝗虫分布的重要因素。

The responses of grasshoppers and their natural enemies to soil humidity and slope in Mahuang Mountain, Ningxia

In order to examine the ecological interactions between insect community of grasshopper and their natural enemies and environmental factors including soil humidity and slope, three experimental sites were selected for insect community investigation in Mahuang Mountain of Ningxia Hui Autonomous Region in 2012. Digital elevation model was used to obtain topography data. Additionally, both net sweeping and eye observation were conducted to determine species composition and abundance of insect community (grasshoppers and predators). Typical correlation analysis method was employed to examine the effects of soil moisture and slope on species diversity and abundance of grasshoppers and their natural enemies. The results showed that the soil humidity in the 20-40 cm depths had significant effects on the abundance of grasshoppers. The soil humidity on the top of slope was higher than that on the bottom of slope in the first investigation. However, the soil humidity varied greatly in different experimental sites in the second investigation. The soil humidity in the 20 cm and 30 cm depths had no significant effects on species diversity of grasshoppers. The correlation coefficients between soil humidity in the 20 cm and 30 cm depths and grasshopper diversity were 0.1306 and -0.0157, respectively. The soil humidity in the other soil depths had no significant effects on the abundance of grasshoppers. However, both species diversity and abundance of grasshoppers declined greatly as slope increasing, and the correlation coefficients were 0.7223 and 0.4315, respectively. The species diversity and abundance of grasshoppers were stable when the slope was less than 30°, but a sharp decline occurred when the slope exceeded 30°. In conclusion, the soil humidity had no effects on species diversity and abundance of grasshoppers, which were negatively affected by the slope in the experiments.