Fine Root Distribution And Coupling To Soil Pysicochemical Properties Under Different Restored Vegetation Types

The Loess Plateau has a fragile ecological environment and soil erosion here is serious.After large-scale soil erosion control,the vegetation coverage in the area has increased significantly,and the ecological environment has improved,which has had a profound impact on the ecological and hydrological processes in this area.The vegetation restoration and its root system play a key role in the influence of soil physical and chemical properties.This article choses the upper catchment of the Beiluo River which located in Wuqi County as the research area,where the effect of returning farmland to forests(grass)is significant.Under the condition that the site conditions and the age of returning farmland are similar,the typical plots under the 6 kind of cover or use types of natural restoration grassland,artificial Hippophae reamnoide,Caragana microphylla,Prunus armeniaca,Robinia pseudoacacia forest in the main mode of returning farmland and farmland in this area are selected.This paper analyzes the characteristics of above-ground community such as vegetation cover and species diversity in various sites,also stratifies the underground plant fine root biomass,soil mechanical composition,organic matter,bulk density,water holding capacity,water stable aggregate content,porosity,infiltration performance.The effects of plant communities with major vegetation restoration types on the basic physicochemical properties of soil and soil infiltration performance were discussed,providing a theoretical basis for understanding the ecological-hydrological processes of vegetation restoration in the Loess Plateau,and providing hydrological parameters for the simulation of ecological-hydrological models.The ecological construction of the plateau and evaluation of soil and water conservation benefits provide scientific and technological support.The main results are as follows(1)A total of 30 species of herbaceous vegetation are common in the study area,belonging to 11 genera and 18 genera,mainly in Asteraceae family.The species richness,diversity,and evenness of the natural restoration grassland were less than those of the other four artificial forests.(2)The fine root biomass under six different coverages decreased with the deepening of the soil layer,they can be well fitted with an exponential relationship except the farmland.On the 0-60 cm profile,the fine root biomass of artificial arbor woodland and shrub land is larger than that of grassland and cultivated land.The fine root biomass of Caragana microphylla land is the largest,indicating that its root system has a strong effect on soil consolidation.(3)Soil organic matter under the cover of six species basically decreased with the deepening of the soil layer,and the effect of vegetation restoration on the improvement of organic matter content slightly decreased with the increase of depth.The soil bulk density increases as the soil layer deepens except the cultivated land.On the 0-60 cm section,the soil organic matter content of Hippophae reamnoide forest and grassland is generally high,the bulk density is small,and the saturated water capacity and capillary water holding capacity are relatively large.The soil in the study area was dominated by powder particles,and there was no significant difference in mechanical composition between different soil layers.The fractal dimension D and MWD under different soil cover decreased with depth.Except for Prunus armeniaca forest land and cultivated land,the initial infiltration rate and stable infiltration rate under the other vegetation types all decreased with the deepening of soil layers;on the 60 cm profile,the maximum soil infiltration rate and cumulative infiltration rate were in the grassland.During the infiltration process,the change of the hydraulic conductivity Ks mainly occurred within 5 hours,the Kostiakov formula was used to simulate the infiltration process in this area.(4)Fine roots can improve soil erosion resistance.The content of >1 mm water-stable aggregates often determine the quality of the soil structure,and soils with higher clay content have higher D values.The soil organic matter content in the study area had a significant effect on the distribution of fine root biomass,and had a stronger effect on soil erosion resistance,the number and stability of macroaggregates,soil water holding capacity and porosity.