旱地红壤线虫群落对不同耕作年限的响应及指示意义

我国热带和亚热带地区的红壤农田肥力水平低,严重制约着农业生产力的提升。不同农业管理措施会对土壤理化性质和生物群落产生不同的影响。本文研究了不同耕作年限条件下的旱地土壤,选取耕作10 a、20 a、50 a的花生地和菜地,并以未开垦的原始荒地作为对照。结果显示,与荒地相比,各年限花生地的土壤肥力等指标表现出下降的趋势,菜地土壤的各项性质则呈现提升的趋势。耕作20 a的花生地土壤有机碳、全氮、微生物生物量碳、有效磷等指标均最低,同时耕作50 a的菜地各项性质相对于10 a有显著的提升(p0.05)。花生地中植食性线虫比例伴随耕作年限延长而下降,而菜地中食细菌线虫比例伴随耕作年限延长而逐渐上升。从线虫生态指标数据显示,花生地相对于频繁施肥和耕作的菜地表现出更为稳定的土壤食物网。因此,线虫群落对不同耕作年限下旱地红壤生态系统的变化表现出一定的指示潜力。

Response of Soil Nematode Community to Cultivation in Upland Red Soil Relative to Cultivation History and Its Significance as Indicator

Low fertility of the red soils in tropical and subtropical regions of China is a major factor restricting development of the agricultural productivity of the regions. Different types of land use and/or different cultivation practices may have different impacts on soil physicochemical and biological properties. Soil nematodes play an important role in the detritus food webs, and have been used as a sensitive indicator of changes in soil ecosystems caused by different agricultural practices. In order to explore the effects of farming cultivations, different in history, on community composition of soil nematode in upland red soils, and relationships between nematode communities and soil physicochemical and microbial properties, red soil peanut fields and vegetable gardens, 10, 20 and 50 years in cultivation history, and a tract of red soil wasteland were selected for comparison in the following indices; soil organic C (SOC), total N (TN), pH, mineral N (MN), available P (AP) , microbial biomass C (MBC), microbial biomass N (MBN), microbial biomass P (MBP) , basal respiration (BR), qCO₂ and soil nematode community. It was found that compared with the wasteland, the peanut fields, regardless of cultivation history, all displayed declining trends in all indices of soil fertility, while the vegetable gardens did reversely. The 20-year old peanut field was the lowest in SOC, TN, MBC and (AP, and the 50-year old vegetable garden was significantly higher than the 10-year old one in all the indices (p < 0.05). In addition, soil nematodes showed a significant increase (p < 0.05) in the soil after 50 years of farming as vegetable garden, but it stayed almost unchanged in the 10- or 20-year old gardens from that in the wasteland. In the peanut fields,. plant-feeding nematodes gradually decreased in proportion in the soil with the cultivation going on (p < 0.05), from 45.89% in the wasteland to 2.60% in the 50-year old peanut field, while bacterial-feeding nematodes increased steadily in proportion with the cultivation going on, from 20.84% in the wasteland up to 67.29% and 54.51% in the 50-year old peanut field and vegetable garden, respectively. No significant changes, increase or decrease, were found with the proportion of fungal-feeding nematodes with the history of cultivation in the peanut fields, but significant decreases were after 20 and 50 years of cultivation in vegetable gardens (p < 0.05). Moreover, no significant difference was found either in the proportion of predators-omnivores between the peanut fields or between the vegetable gardens different in cultivation history. Analysis of nematode ecological indices shows that the soil food webs in the peanut fields were more stable than those in the vegetable gardens that were subjected to more frequent fertilization and tillage. It was found in this study that soil physicochemical and biological properties varied significantly with the cultivation going on in both the peanut fields and the vegetable gardens. Therefore, changes in soil nematode community can be used as an indicator of upland red soil ecosystems, and may provide some complementary information about structure of the red soil ecosystem, and hence help understand comprehensively dynamics of soil ecosystem of the red soil farmlands with cultivation going on.