Changes Of Soil Fertility And Spatial Distribution Of Nematodes After The Establishment Of Vegetation On Sand Dune In Horqin

This study objective is to explore effects of plant on spatial distribution of soil nutrients and soil nematode community and to use nematode group to indice recovery mechanism of ecological system on sand dune. Soil nutrients and soil nematode community were researched in different slopes, different depths and shrub influences on Horqin sand land which were planted vegetation for fixing sand dune 25 years ago. The results showed that:(1) Contents of NO3--N, NH4+-N and total N descreased with soil depth for fixing sand vegetation were planted on sand dune. Contents of soil nutrients at depth of 0～5cm were significantly higher than that in other soil layers. The enrichment of NO3--N and NH4+-N decreased pH value and increased EC value, and had an important significance.(2) Exchangeable K, Na, Ca and Mg were influenced by planted Caragana microphylla, especially at different slopes. Every kind of exchangeable salt decreased with soil depth. Shrubs took significantly effects on enrichment of exchangeable Na, Ca and Mg, but no significance on exchangeable K.(3) Contents of TOC, total N and total P decreased with soil depth, and they were higher at WS than at TS and LS. Contents of TOC and total K are significantly higher at US than at BS. Changing range of C/N at US is larger than that at BS.(4) Microbial biomass carbon showed the significantly difference at different slopes and depths of stable sand dune, and the highest content of it was at surface layer. Microbial biomass carbon decreased with soil depth. Planting enhanced the accumulation of microbial biomass carbon.(5) Soil nematode individuals decreased with soil depth at WS and TS in spring. But numbers of nematode were the most at depth of 5～10cm on three slopes in summer, and showed no significance among slopes. Bacterivoirs trophic group is the dominance in Horqin stable sand dune. Dominant genera are Acrobeles, Acrobeloides, Cervidellus and Wilsonema.(6) Multi-factor ANOVA analyisis showed that the most important factor affecting nematode indices is slope in spring. Following that is soil depth and shrub, respectively. In summer, the most important factor is soil depth, and slope and shrub followed. Intereaction from slope, shrub and depth on TNEM, BF and FF are significance. Different seasons affect TNEM, OP, TD, EI, BI, BF,λand H'significantly. (7) Every testing nutrient took a significant effect on soil respiration and microbial biomass carbon except total K, and enhanced the ability of reproduce and activity. Adding number of microbe was benefit to soil fertility greatly.(8) Enrichment of soil nutrients affects the number of SNEM, BF, FF and the J'significantly. The main influence factors were TOC, TN, exchangeable K and Na. Effects of soil spiration and microbial biomass carbon on nematode community were more significant in spring than that in summer.