| Based on the long-term experiment carried out in an upland field of red soil, the impacts of long-term application of organic manure on distribution, community structure and seasonal changes of soil nematodes were studied. And several analyses were conducted on relationship between environmental factors and soil nematode community composition as well. The long-term manure application experiment was set up at Red Soil Ecological Experimental Station of the Chinese Academy of Sciences, Jiangxi Province. The long-term organic manure application experiment was designed to have four treatments: CK (no pig manure); ON1(low amount of pig manure); ON2(high amount of pig manure); ON2L (high amount of pig manure with lime). The study showed4301individuals in all treatments, including424in CK,1339in ON1,1514in ON2and1024in ON2L. The total nematode numbers ranged from72to880individuals per100g dry soil, represented by14families and27genera of soil nematodes were identified in the upland field, including6genera of plant-parasites,10genera of bacterivores,3genera of fungivores and8genera of predators/omnivores, of which Pratylenchus was found to be the dominant genera in all treatments, Rhabditis, Protorhabditis and Pratylenchus could be considered as key species in the upland. Plant parasites were found to be the dominant trophic group in CK and ON1while bacterivores was dominant in high rate manure. Application of organic manure significantly affected the nematode community structure. The minima of nematode abundance was observed in spring (April) while the maximum in summer (July) before maize harvesting, and the total nematode number under four manure treatments followed a decreasing order of ON2> ON1>ON2L> CK. The abundance of fungivores and plant parasites showed a decreasing sequence of ON1> ON2> ON2L and CK. The application of manure had less impact on omnivores-predators abundance. Moreover, functional groups of dominant were c-p1and c-p3, and group of c-p4,5showed minima. Significant differences were found between treatments and between month in Shannone-Weaver index (H’) and genus dominance (λ)(p<0.05), combined maturity index (ΣMI), nematode channel ratio (NCR) and structure index (p<0.01). Nematode channel ratio (NCR) indicated bacterial decomposition under high rate manure, whereas those in low rate manure were relatively more dominant fungal decomposition. The obtained data of nematode faunal profile analysis showed the food web of CK was maturing while most treatments with organic manure showed the food webs were relatively highly disturbed. Ripening time of maize could be considered as a turn-point in all sampling time. Redundancy analysis (RDA) indicated that axes1and2were found to be accounted for a total of26.3%of the total variance, and total N, organic matter, pH, available P and available K were the most important environmental parameters that influenced nematode distribution. The variation portioning analysis (VPA) showed climatic factor was able to independently explain17.3%of the variation observed and soil factor explained24.7%. Interactions between the two factors were25.3%total. Furthermore, aggregated boosted tree (ABT) analysis showed soil NO3--N and/or NH4+-N contents were the dominant variables that determined the variation of most trophic groups, apart from soil available K determined bacterivores. Seasonal changes in soil nematode community structure, together with new analysis under long-term experiment, could be used as an indicator of variation of soil fertility and considered an important bioindicator of soil health quality on an acid red soil in middle subtropical China. |
PDF Full Text Request