| How to effectively improve land productivity and solve rocky desertification ecological probl ems are important challenges for the development of typical fragile ecological regions for a series of problems such as soil erosion,vegetation destruction and low land productivity in rocky deserti fication areas.The research on characteristics of soil particle fractal and aggregate stability under t he environment of grassland in rocky desertification area and rocky desertification control area is helpful to reveal the stability of soil structure and carbon sequestration capacity,and to provide sci entific basis for preventing soil and water loss and improving soil corrosion resistance.This study is based on different grades of grassland in rocky desertification area of karst plateau mountain Sal axi in Bijie City,Guizhou Province(no rocky desertification,potential rocky desertification,light rocky desertification,moderate rocky desertification,and intensity rocky desertification)and rock y desertification control projects(forest-grass planting,rose planting,forest-grain planting).The a bove environmental soils are taken as research objects,and the soil particle size volume fractal,th e number of aggregates,aggregate stability and soil aggregate organic carbon are monitored.Princ ipal component analysis method was used to analyze the factors affecting the soil corrosion resista nce.Finally,the soil corrosion resistance index formula was used to quantitatively analyze the soil corrosion resistance under several control measures in order to reveal mechanism of soil degradati on in rocky desertification areas and provide scientific basis and technical support for the restorati on of ecological environment in rocky desertification areas.The main findings are as follows:(1)In study area,the content of clay is low and the content of sand and powder is high in grassland of rocky desertification area and rocky desertification control environment such as forest-grass planting,rose planting and forest-grain planting under different levels of rocky desertification.The fractal dimension varies from 1.80 to 2.20,and the fractal dimension(0-10cm)is smaller than the lower layer(10-20cm).Correlation analysis shows that the content of clay and powder is significantly correlated with the soil fractal dimension.(2)The particle size distribution and stability of soil aggregates can reflect the influence of rocky desertification control measures on soil quality.The composition and stability characteristics of aggregates under different dry and wet sieve treatments are very different.Under the dry sieving treatment,dominant particle is the large aggregates which size is bigger than 2mm,and the percentage of agglomerates of each particle size increases as the particle size increases.The results of wet sieving method show that the mass percentage of soil aggregates in the upper and lower layers is basically dominated by large agglomerates and small agglomerates(0.25-2mm),and microaggregates account for a small proportion.Agroforestry management is beneficial to increase the content of large aggregates.(3)The stability of agglomerates characterized by MMW,GMD,D,> 0.25 mm aggregate content and other indicators showed that stability of soil aggregates is the worst in grassland under the light grade of rocky desertification area.The stability of grassland under the environment of no rocky desertification is strong;the stability of soil aggregates is good in environment of single grassland,forest-grass,forest-shrub and grass combination,while the stability of thorn pear grassland is the worst;in rose environment,the interplanting measure of walnut-rose-potato have the worst stability,and the other several measures of rose intercropping have general effects;the forestry grain environment,the corn farmland has the worst stability,and the difference between other plots is not significant.(4)The organic carbon content of the aggregates in the small-grained aggregates is the highest in each environment,and the organic carbon content of the aggregates increases with the decrease of the particle size of the soil aggregates,indicating that the small-sized aggregates are more conducive to the accumulation of organic carbon.However,the contribution of >5mm and 2-5mm water-stable aggregate organic carbon to soil organic carbon is the largest,and the contribution of 0.25-0.5mm water-stable aggregate organic carbon is the smallest.(5)Principal component analysis of various factors in the study area showed that the soil anti-corrosion factors mainly had clayey content,>0.25 mm water-stable aggregate content and organic matter;soil resistance comprehensive index under different grades of rocky desertification and different treatment modes is different,forest-grass mode > rose mode > forest-grain mode > shrub-grassland in rock desertification area,forest-grass measures are more effective in improving soil corrosion resistance. |
PDF Full Text Request