长期施肥对紫色土农田土壤动物群落的影响

土壤动物在陆地生态系统物质循环和能量流动中起着重要作用,直接或间接的参与土壤有机质的分解与矿化;长期施肥对土壤理化性质产生影响的同时,改变了土壤动物群落组成.为查明紫色土长期施肥对土壤动物群落的影响及其响应关系,于2008年的5、7、9和11月分别对紫色土农田无肥对照(CK)、单施氮肥(N)、常规化肥氮磷钾(NPK)、有机肥(OM)、有机肥与化肥氮磷钾混施(OMNPK)、秸秆还田(RSD)和秸秆还田与化肥氮磷钾混施(RSDNPK)等7种长期施肥定位试验地的土壤动物群落进行调查,采用改良的干漏斗和湿漏斗两种方法,共获得土壤动物9454只,隶属7门17纲24目.分析表明,OM和RSDNPK两种施肥方式下土壤动物群落的多样性显著高于CK、N和NPK等3种施肥方式,说明有机物料的长期投入有利于提高土壤动物群落丰富度和多样性.方差分析表明施肥方式对土壤动物主要类群密度的影响差异性极显著(F=42.412,P=0.0001),对土壤动物群落类群影响存在不均衡性.施肥方式主要影响农田土壤动物类群的种群个体数量、线虫动物门个体数量、大蚓类个体数量、甲螨亚目个体数量、密度-类群指数DG及土壤动物群落类群数等六个指标,初步认为这些主要类群因素能够预测长期施肥引起的土壤肥力变化,可能对指示土壤质量的变化具有一定潜力.

Effects of fertilization regimes on soil faunal communities in cropland of purple soil, China

Soil fauna regulate soil processes affecting soil organic matter decomposition, mineralization and nutrient cycling, and play an important role in terrestrial ecosystem nutrient cycling and energy flow. Management of cropland, especially long-term fertilization, has considerable impacts on soil properties, and also affects the composition of soil faunal communities. The Sichuan Basin is an important agribusiness area in southwestern China which occupies 7% of the national cropland and supplies 10% of the agricultural products of China. The typical soil in the study area is highly productive and is called "purple soil" locally. It is classified as a Pup-Orthic Entisol in the Chinese Soil Taxonomy and an Entisol in the U.S. Taxonomy. However, the influence of long-term fertilization regimes on soil faunal communities and how indices of these soil faunal communities respond to changes in soil properties are poorly understood. To investigate the effects of long-term fertilization regimes on the soil faunal communities and their inter-relationships, seven fertilization regimes, a control with no fertilization (Control Check, CK), nitrogen fertilizer only (Nitrogen, N), a mixed synthetic fertilizer (Nitrogen Phosphorus Potassium, NPK), organic manure (Organic Manure, OM), organic manure plus synthetic fertilizer (Organic Manure Nitrogen Phosphorus Potassium, OMNPK), crop residues returned to the soil as fertilizer (Returning Straw Decomposition, RSD) and crop residues plus synthetic fertilizer (Returning Straw Decomposition Nitrogen Phosphorus Potassium, RSDNPK) were applied to the purple soil of the Sichuan Basin, China, and examined in May, July, September and November, 2008 using modified Tullgren and Baermann funnels. A total of 9,454 individuals were collected, and classified into seven phyla, 17 classes and 24 orders. Analysis of the data showed that the soil faunal communities were richer in the OM, OMNPK and RSDNPK plots, and that the greatest diversity of the soil faunal communities was found in the OM and RSDNPK plots, being significantly higher than those in the CK, N and NPK plots. Application of organic fertilizers promoted diversity and abundance of soil faunal communities, and was favorable for their survival and development. Analysis of variance indicated that different fertilization regimes had extremely significant impacts on the density of the main soil faunal groups (F=42.412, P=0.0001) and led to imbalances being present in the soil faunal groups. Analysis of the relationships between the fertilization regimes and the main groups of the soil faunal communities, using Principal Component Analysis, showed that the different fertilization regimes primarily affected six indices of soil fauna; individuals in the soil faunal population, individual nematodes, individual megadriles, individual Oribatidas, the DG index (density-group diversity index) and total groups in the soil faunal communities. Therefore, we consider that changes in the cropland soil faunal communities have a relationship with differences in long-term fertilization management. These six indices of the individual soil fauna population; individual Nematodes, individual Megadriles, individual Oribatidas, the DG index (density-group diversity index) and total groups in the soil faunal communities can be used to predict changes of soil fertility caused by long-term fertilization application, and have great potential as bio-indicators of changes in soil quality.