Study On The Variation Of Soil Physical And Chemical Properties And Its Influencing Factors After Revegetation In The Karst Area Of Southwest Hubei

Rocky desertification is a pervasive ecological and environmental problem in karst areas in southwest China.Under the background of large-scale ecological recovery policies such as "Grain for Green",good results have been achieved in ecological restoration in karst areas in southwest China.However,the evolution mechanism of soil basic properties and its influencing factors in the process of vegetation restoration is still unclear.Relevant research is of great significance for the policy ecological environment,soil and water prevention,and policy implementation in karst areas.In this study,different vegetation types were selected in Hubei province,and measured physical and chemical properties of surface soil at each plot site.Analyzed the influence of environmental factors such as lithology,elevation,temperature,soil depth.The ultimate goal is to provide some scientific basis for the study of soil property evolution and government decision-making in the karst area.The results show that:(1)The soil developed in carbonate rocks is rich in calcium and magnesium and easy to weathering and dissolve.As a result,the nutrients of organic carbon and total nitrogen and sand content in the surface layer(0-15 cm)of karst soils are higher than those in non-karst soils.Due to the shallow soil layer,the total amount of unit soil nutrients in the karst area is limited and the availability is low.Farming activity will be significant(p < 0.05)increases soil nutrient loss.Non-karst areas also lead to increased clay and decreased sand,further increasing the risk of clay loss in extreme climates(especially rainstorm-induced floods).The main controlling factors of soil properties change due to lithologic differences are not consistent.The bare rock ratio in the karst area explains 63.6% of the variation of soil properties,which is significantly related to soil organic carbon and total nitrogen(p < 0.05)positive correlation.In addition to the land use pattern(43.8%),the difference of temperature on the gradient of elevation(27.5%)also has an important influence on the change of soil properties in non-karst areas.A decrease in temperature with increasing elevation reduces the production of litters and the decomposition rate of organic matter,leading to the increase of organic carbon and total nitrogen accumulation.Therefore,the prediction of soil properties at a regional scale requires attention to the effects of environmental factors such as rate lithology on soil physical and chemical properties.(2)Compared with cropland,after about 15 years of vegetation restoration,soil nutrient contents in plantation forest and natural restoration forest was significantly increased,but there was still a great difference in soil nutrient contents between plantation forest and secondary forest.There was no significant difference in soil nutrient content between plantation forests and natural restoration forest,which meant that short-term restoration methods could not determine which was more favorable.Elevation is an important environmental factor affecting the change of soil nutrients under the background of vegetation restoration.There is no correlation between all soil nutrients and elevation,suggesting that human factors may be the main driving factors.Soil nutrients in both plantation forests and natural restoration forests decreased with the increase of elevation.The difference in biomass caused by vegetation restoration at different elevations(i.e.,the effect of vegetation restoration at lower elevations was better than that at higher elevations)may be the influencing factor.In conclusion,vegetation restoration is conducive to nutrients enhancement and is affected by elevation.(3)As the representative of the top vegetation community,the surface soil pore properties(total porosity and capillary porosity),soil texture(sand and silt),and bulk density of the secondary forest were significantly different from the other three landuse patterns.In the process of vegetation restoration,environmental factors have a certain effect on soil properties.Elevation and temperature in plantation forest and natural restoration forest have a significant effect on soil properties,especially texture(p < 0.05).Clay content decreased while the sand content increased with the increase of elevation.Vegetation restoration had little effect on soil physical properties,and there was no significant difference in soil physical properties between plantation forest and natural restoration forest and cropland,which may require longer time series monitoring.