氮磷输入对过度放牧退化草原土壤线虫群落的影响

线虫是陆地生态系统中数量最多的一类无脊椎后生动物,在土壤碎屑食物网中占据多个营养级,并在能量流动和养分循环中发挥重要的生态功能.土壤线虫的群落结构和多样性水平可以反映生态系统功能的变化.多年来,过度放牧等不合理的开发利用导致我国大面积的草原处在不同程度的退化之中,外源性养分输入是维持其养分平衡进而恢复其生态和生产功能的重要措施.本研究以内蒙古锡林郭勒退化草原为对象,就氮磷输入对土壤线虫丰度和群落结构的单独效应和交互效应进行了研究.本研究获得线虫38属,其中垫咽属、滑刃属、索努斯属和盾垫属是该退化草原线虫群落优势属.氮输入降低了土壤线虫总丰度、捕食杂食线虫丰度以及植物寄生线虫丰度,而磷输入提高了土壤线虫总丰度、食真菌线虫丰度、捕食杂食类线虫丰度以及植物寄生线虫丰度,氮输入抑制了磷输入对线虫总丰度、捕食杂食线虫和植物寄生线虫丰度的促进作用.氮磷输入对线虫多样性无影响,可能与不同养分输入下稳定的植物群落多样性有关.氮输入显著提升了退化草原线虫成熟度指数,降低了植物寄生线虫成熟度指数(PPI),并且能缓解磷输入对PPI和瓦斯乐斯卡指数的负面作用,表明氮输入提高退化草地土壤健康程度,促进线虫群落和食物网的稳定性.上述研究结果有助于从土壤生物学角度理解氮磷输入对退化草地恢复的影响机理.

Effects of nitrogen and phosphorus inputs on soil nematode community in a degraded grassland.

Nematodes, occupying multiple trophic levels in the food web, play important roles in energy flow and nutrient cycling. Most of Chinese natural grasslands have been degraded due to long-term unreasonable utilization, such as over-grazing. External nutrient input is an important way to restore the ecological function of degraded grasslands. The main and intertative effects of nitrogen and phosphorus inputs on soil nematode abundance, trophic group composition and community structure were studied in the grasslands in Xilingol League of Inner Mongolia. Totally, 38 genera of nematodes were recorded. Tylencholaimus, Aphelenchoides, Thonus, and Scutylenchus were dominant genera in this degraded grassland. Nitrogen input decreased total abundances of soil nematodes, and that of omnivores-carnivorous nematodes and plant-feeding nematodes. Phosphorus input increased total abundances of soil nematodes, and that of fungal-feeding nematodes, omnivores-carnivorous nematodes, and plant-feeding nematodes. Nitrogen input inhibited the positive effects of phosphorus input on the abundances of total nematodes, omnivores-carnivorous nematodes and plant-feeding nematodes. Nutrient inputs had no effect on nematode diversity, which would be resulted from the stable plant community. Nitrogen input significantly increased nematode maturity index, decreased plant parasitic nematode maturity index (PPI), and greatly alleviated the negative effects of phosphorus input on PPI and Wasilewska index, indicating that nitrogen input could improve soil health condition and the stability of nematodes community. Our results would help improve our understanding of the effects of nutrient inputs on degraded grassland ecosystem from a soil biotic perspective.