| The redistribution of rainfall by vegetation canopy can change the spatial distribution of water and reduce the erosion impact intensity of rainfall on soil in the process of vegetation restoration,meanwhile,the synergistic effect of vegetation-soil can improve soil structure and reduce soil erosion.In order to clarify the influence of Robinia pseudoacacia(RP)on rainfall redistribution characteristics and soil erosion resistance during the growth recovery process of vegetation after the grain-for-green project in the loess plateau,in this study,the artificial RP communities that restored for 10,18,28 and 43-years in loess hilly-gully region in yan'an ansai district were taken as the research objects,and the slope farmland with low fat was taken as the control.Investigate the community characteristics of RP communities and redistribution of rainfall by using field research,combined with the indoor analysis methods of soil physical and chemical properties and grain composition.The results are expected to provide scientific basis for the ecological benefit process and evaluation of plantation vegetation restoration in the loess plateau.The main research contents and results are as follows:(1)The horizontal growth of RP was rapid before 28 a and slowly after 28 a,and the canopy density of RP increased first and then decreased in the process of restoration.The succession sequence of aboveground herbaceous community was Carex scaposa + Heteropappus altaicus + Poa pratensis(10a)?Patrinia heterophylla + Poa pratensis + Artemisia sacrorum(18a,28a)?Artemisia sacrorum+Artemisia giraldii + Poa pratensis(43a).The three functional plants Compositae,Gramineae and Leguminosae are dominant in communities with different ages.The diversity index of herbaceous plant community decreased first and then increased,while the biomass and thickness of litters increased significantly in the restoration of vegetation.(2)The throughfall,stemflow and canopy interception ratio of the rainfall on average is 80.37%,1.74% and 17.89%,respectively.The trend of stemflow and canopy interception is first increased and then reduced with the recovery of vegetation,but the trend of throughfall is first decreased and then increased tendency,and the effective intercept amount of litters is significantly increased with the recovery of RP.The surface runoff of RP communities significantly lower than that of farmland,and surface runoff has first decreases after increasing trend in the restoration of vegetation.Analysis showed that vegetation diversity index and canopy density of RP communities are the main influencing factor of rainfall redistribution,followed by biomass of litters.The planting of RP can effectively conserve water and soil,reduce surface runoff,and increase soil water content.There is a negative correlation between soil water content and plant community diversity,the growth of plants consumes much water.(3)SOC,TN and AN contents in soil of RP communities were significantly higher than those in farmland.TP and AP contents of soil were lower than farmland.The soil C:P and N:P increase significantly with the increase of recovery years,and the P limit gradually appears in the recovery of RP communities.The soil runoff was significantly negatively correlated with soil C and N in correlation analysis,canopy interception,SWC and effective intercept amount of litters were significantly positively correlated with AN,and RDA analysis showed that litters biomass had an extremely significant impact on soil nutrients and soil physical and chemical properties.Soil large aggregate content,soil clay,aggregate mean weight diameter(MWD)and soil texture fractal dimension values are higher than that of farmland,and increases along with the restoration of RP communities.Soil erodibility(K)of RP communities were less than that of farmland and the trend is first increased and then reduced with the recovery of vegetation.SOC has significant correlation with soil aggregate formation and the increase of soil silt content.There is a significant correlation between SOC and litter biomass,the herb and litter biomass and growth of RP have great deal of correlation with soil particle composition and resistance to erosion,meanwhile,herb and litter biomass have positively related to relationship with the soil clay and silt content.RP communities can affect soil physical and chemical properties by change the characteristic of rainfall redistribution,then affecting soil structure and increasing soil erosion resistance indirectly.In summary,in the rainfall redistribution characteristics of RP forest,the throughfall is the largest,and the runoff decreases first and then increases with the increase of recovery years.The vegetation diversity index and canopy density of RP are the main influencing factors of rainfall redistribution.Rainfall redistribution characteristics of RP affect soil physical and chemical properties and thus indirectly improve soil erosion resistance. |
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