Structure And Dynamic Characteristics Of Shrub Patch In The Water-wind Erosion Crisscross Region

Soil desertification has become a serious environmental problem with increasing global warming and human activity.Especially wind-water erosion crisscross region on the Loess Plateau is facing the deterioration of environment,such as soil erosion and other ecological problems,which was a threat to the survival and development of local residents.Shrub patch plays an important role in ecosystem stability and vegetation recovery in water-wind erosion crisscross zone.Artemisia ordosica shrub patch was the dominant landscape in water-wind erosion region in Loess plateau.We studied the spatial pattern,number structure,and the micro-habitat(species diversity,biomass,and soil water content,etc.)of shrub patch in different stage,trying to reveal vegetation restoration mechanism in the water-wind erosion crisscross zone.The main results of this paper are as follows:(1)The spatial distribution characteristics of shrub patches in the study area showed that,at the early successional stage,the small shrub patches(cube root volume d < 60 cm)were spatial aggregation,then the strength of aggregation decreased at the later successional stage,while large shrub patches(d ? 95 cm)were regularly distributed and the dead shrub patches(d ? 95 cm)were randomly distributed in last phase.The spatial association of the shrub patches showed positive spatial relationship between different sizes shrub patches,except that the middle shrub patches(60 cm< d ? 95 cm)were negatively related to large shrub patches(d > 95 cm).(2)The number structure of the shrub patches was a pyramid,and the small and medium shrub patches accounted for 77% of the total,and the growth of patches structure was low.Survival curve was Deevey-type II.Survival function analysis showed that shrub patches survival rate function monotonically decreased.Cumulative mortality function monotonically increased.Mortality density function has little difference in all the shrub patches.Risk rate function showed increasing trend with increasing size of shrub patch.(3)The Shannon-wiener index,richness index,biomass and soil water content were higher in shrub patch than those in the bare land patch.With the increasing size of shrub patches,the indices increased.Shrub patch ameliorated micro-habitat obviously in wind-water erosion crisscross region in Loess Plateau,and then benefit the process of shrub patch succession.As the pioneer species of plant community in secondary succession,Artemisia ordosica shrub patch plays an important role in the stability of the ecosystem in the cross areas of wind-water erosion in Loess Plateau in China.Succession stage and interaction of shrub patches determined the spatial pattern of shrub patch in small spatial scale(0-10 m).The shrub patch could grow,renew,and adapt in the cross areas of wind-water erosion climate environment,and the population was in stable increasing situation.Therefore,shrub patch can improve plant diversity,above-and below-ground biomass,and soil water content and these indices increased in shrub patch succession.The amelioration of shrub patch to micro-habitat would contribute to the settlement of other plants and accelerate the ecosystem recover in the cross areas of wind-water erosion.