Influences Of Soil Perparation Measures On Root Distribution Characteristics And Ecological Effect Of Plant Communities On The Loess Plateau

Slope surface preparation and vegetation restoration are the core means of ecological restoration in the semi-arid loess plateau,which plays an important role in improving habitats,optimizing vegetation structure,and enhancing ecosystem functions.This study was based on a variety of technical methods such as ground penetrating radar scanning,in-situ root drilling sampling,river basin survey,and simulated rainfall experiment,and a large amount of detailed data was obtained.On this basis,this study systematically analyzed influences of different soil preparation measures?reverse-slope terraces,fish scale pits,level benches?and plant communities?Pinus tabulaeformis,Platycladus orientalis,Armeniaca sibirica,Caragana korshinskii,Medicago sativa,weeds?on plant root distribution,soil moisture,nutrients,mechanical composition,and plant soil and water conservation capabilities.Besides,this study quantified the mutual feedback relationship between plant roots and soil properties,compared the water and sediment effects of different plant communities,and discussed the optimization mode of the species composition and community structure from the perspective of soil preparation and plant roots.The main conclusions are as follows:?1?The soil preparation measures had a significant influence on the root distribution?P<0.05?.Among the three typical soil preparation measures of Pinus tabulaeformis forest,the total root density(18.14 kg m^-2)of level benches was significantly higher than that of fish-scale pits(13.95 kg m^-2)and reverse-slope terraces(9.84 kg m^-2)?soil layer of 0-400 cm?,and fine root parameters of level benches?fine root density and fine root morphological density?were the highest,soil moisture and nutrient conditions were the best,and the soil erosion resistance was the strongest as well.The main reason was the difference in root distribution caused by soil preparation measures?P<0.05?.Compared with coarse roots,fine roots could improve soil quality and effectively increase deep soil moisture.Due to the influence of topographic factors on resource redistribution,fine root parameters of upper and middle slope positions were significantly higher than those of lower slope positions?P<0.05?,and the difference in root distribution of different slope positions also effectively weakened space heterogeneity of the slope surface moisture and nutrient.At the same time,in order to adapt to water stress,total root density of sunny slope was higher,while fine root of shade slope was more developed.?2?The root growth distribution and ecological effects of different plant communities were significantly different.Among them,the total root density,fine root density and fine root morphological density?fine root length density,fine root surface area density and fine root volume density?of trees?P.tabulaeformis,P.orientalis,and A.sibirica?were significantly higher than those of shrubs?C.korshinskii?and grasses?M.sativa and natural grassland??P<0.05?,and the total root density and fine root density of Pinus tabulaeformis and the fine root morphology density of Platycladus orientalis were the highest,respectively.In each plant community,as soil depth increased,fine root parameters decreased significantly.Affected by the difference in plant root distribution,different plant communities had very different soil properties?soil texture,nutrients,moisture,and erosion resistance?.Structural equation model showed that plant roots?especially fine roots?could significantly improve the soil quality and its erosion resistance through direct and indirect methods such as penetration,decomposition,connection and secretion,so the soil nutrients,water conditions and stability of the arbor community were also the best.?3?Under different soil preparation measures,the nutrient content of each plant community was closely related to soil nutrients.Compared with the above ground branches,fine root nutrient contents were more closely related to soil nutrients.Among them,the total nitrogen content of fine roots in different plant communities was:shrub communities>grass communities>tree communities.With the increase of soil depth,the total nitrogen content of fine roots of trees decreased significantly,while the total nitrogen content of fine roots of shrubs and grasses increased significantly.The fine root organic carbon content and carbon-to-nitrogen ratio were the highest in the arbor community,and there was no significant difference in the fine root organic carbon content and carbon-to-nitrogen ratio between shrubs and grasses.There was no significant difference in carbon and nitrogen content among arbor communities?P.tabulaeformis,P.orientalis,and A.sibirica?as well?P<0.05?.?4?The root systems of different plant communities had an important influence on the runoff and sediment production process.The results of canonical correlation analysis and correlation analysis showed that the explanation of runoff erosion factors by plant roots was higher than that of soil properties,and there was significant positive correlation between runoff erosion factors and soil particle size distribution?P<0.05?,while it was significantly negative related with soil nutrients?P<0.01?.When the surface coverage of the plant community was nearly 100%,the benefits of reducing flow and sediment were the best,and it decreased as the surface coverage decreased.The plant parts of different plant communities,such as P.orientalis,M.sativa and Agropyron cristatum,had significant differences in erosion resistance.The branches and leaves of P.orientalis community had the strongest erosion reduction ability,while M.sativa had the least difference in the benefits of reducing flow and sediment,and choke flow effect of their litter was the most significant.The spatial distribution of the plant underground roots in the soil is diverse and has a wide distribution range,and it is very difficult to systematically determine the spatial distribution of the plant.This study clarified the root distribution characteristics of deep soil profiles of typical plant communities under different soil preparation measures,clarified the influence mechanism of plant root distribution on soil properties under different site conditions,and discussed the distribution of nutrients in plants and soil,quantitatively revealed the soil and water conservation capabilities of different parts of the plant underground root system and surface cover.It is a useful supplement to and deepening the study of the ecological restoration mechanism of the Loess Plateau.It can also provide scientific theory basis and practical technical support for the management of fragile mountain ecosystems,optimization of land remediation technologies,and screening of vegetation species.