生物土壤结皮对荒漠土壤线虫群落的影响

Abstract

Biological soil crusts(BSCs) play an important role in dune fixation and maintaining soil biota in arid desert ecosystems.Soil nematodes can be used as significant bio-indicators to reflect soil recovery regimes and important biological properties in studies of the restoration and health of sandy ecological areas.However,the relationship between BSCs and nematodes is currently poorly understood.To understand how BSCs affect soil nematodes,sand dune soils under algal and moss crusts were investigated in an artificially revegetated desert area at the southeastern edge of the Tengger Desert,China.Sample plots were selected in four areas that had undergone different periods of sand-fixing(the sand dunes were stabilized in 1956,1964,1981 and 1991,respectively).Mobile sand dunes were used as the control.Soil samples from different soil layers(0—10,10—20 and 20—30 cm,respectively) under algal and moss crusts were collected in different months(4,7,9 and 12,respectively) to analyze the temporal and spatial variation of soil nematodes in the artificially revegetated desert areas at the southeastern edge of the Tengger Desert.Natural vegetation areas at Hongwei in the Shapotou area were used as the control.Soil nematodes were separated using the improved Baermann funnel method and were identified and counted by an optical microscope.Our results showed that algal and moss crusts could significantly enhance nematode abundances,generic richness,Shannon-Weaver index,enrichment index and structure index in the sand dunes,artificially stabilized in 1956,1964,1981 and 1991,respectively(P0.05).This can be attributed to the presence of BSCs providing an essential food source and the creation of suitable habitats for soil nematodes.The time of sand dune fixation was positively correlated with soil nematode abundances,generic richness,Shannon-Weaver index,enrichment index and structure index under crusts(P0.05).This result suggested that long periods of sand dune fixation were more beneficial to the survival and reproduction of soil nematodes than short periods of sand dune fixation.Crust type significantly affected soil nematode communities,with moss crusts having higher nematode abundances and generic richness than those of algal crusts.This result suggested that the late-successional moss crusts were more beneficial to the survival and reproduction of soil nematodes than the early-successional algal crusts.In addition,algal and moss crusts significantly increased soil nematode abundances and generic richness in the 0—10,10—20 and 20—30 cm soil layers.However,the effect gradually decreased with increasing soil depth,which demonstrated that BSCs were more beneficial to the survival of soil nematodes in topsoil than in subsoil.There were also seasonal changes of nematode abundances under algal and moss crusts,in the following order: autumn summer spring winter.Seasonal changes could reflect changes in the biomass,cover and species composition of BSCs with season changes.Therefore,the presence and succession of BSCs were beneficial to the survival and reproduction of soil nematodes,which increased their amount,species and diversity.The results indicate that BSCs could improve the recovery of soil and corresponding ecological systems in the artificially revegetated desert areas at the southeastern edge of the Tengger Desert.