Comparative Study Of Soil Quality Under Different Vegetation Conditions In The Hilly And Gully Regions Of The Loess Plateau

Based on the soil properties of the tested area, in perspective of soil nutrient status andmicrobiological characteristics, this study analyzed and compared the mean and verticaldifferentiation of soil quality indicators in0~60cm soil profile in typical area that convertingfarmland to forest, with wasteland and farmland soil as controls. By introducing the indicatorof comprehensive soil quality index, to quantitatively describe the soil quality under differentvegetation conditions, and compare its effects on improving the soil quality of farmland, aswell as providing a scientific basis for the area converting farmland to forest. The mainconclusions are as follows:(1) The soil nutrient status is different among different vegetation conditions, andspecifically the content of soil organic matter, total nitrogen and available nitrogen. Legumework differently in improving soil organic matter and nitrogen. The Robinia pseudoacacia andCaragaua korshinskii work well in soil organic matter and nitrogen accumulation in0~20cmsoil, while the Robinia pseudoacacia has a good condition of nitrogen availability in surfacesoil and Caragaua korshinskii in soil below the depth of20cm. Due to human interference, theAlfalfa is not conducive to the accumulation of organic matter and nitrogen, at the same time,the effects on nitrogen availability is not obvious, too. Prunus armeniaca L and farmlandshows an accumulation of organic matter and nitrogen in the surface soil layer due tofertilization, and the nitrogen availability reduced with increasing soil depth. ChineseArborvitae and pear trees is not conducive to the accumulation of organic matter and nitrogen,as well as nitrogen availability. It all shows an obvious accumulation of organic matter andtotal nitrogen in the surface soil.(2) The soil microbial properties is different among different vegetation conditions, whichshows as soil MBC, respiration and enzyme activity is significantly different. Compared withfarmland, the soil MBC content of different vegetation are improved with varying degrees,and particularly evident in the surface. Legumes works better than other vegetation inimproving soil MBC content. Soil MBC content of Prunus armeniaca L is also higher thanother vegetation as a result of fertilization, the improvement of MBC in wasteland is inferiorto other vegetation conditions.In aspect of effects on soil respiration rate, the Robinia pseudoacacia and Caragaua korshinskii have significantly improved, the wasteland and other vegetation conditions showsno significant change. And the Prunus armeniaca L has significantly reduced. Soil respirationrate of different vegetation conditions decreased with soil depth, but due to the complexity ofimpact factor, the variation of soil respiration rate below the surface showed uncertainty.In aspect of effects on soil enzyme activities, different vegetation can significantlyimprove the soil enzymes activity on the whole. The legume shows a higher condition inUrease, phosphatase, catalase and invertase activity, and followed by orchards, woodland andwasteland. Different soil depths and different vegetation types have rarely effect on catalaseactivity. In the vertical direction, soil enzyme activity weakened gradually with the increase ofsoil depth.(3) The soil quality index was calculated and compared under different vegetationconditions and the result shows that, in addition to alfalfa, soil quality index were higher thanthe farmland under different vegetation conditions. The soil quality conditions of Robiniapseudoacacia and Caragaua korshinskii ranked the first, followed by Prunus armeniaca L andpoplar, the soil quality index of wasteland and jujube tree, Chinese Arborvitae, pearconditions were close to farmland, reflect that the effect on improving the farmland soilquality status is not obviously. The Alfalfa has decreased compared to farmland, reflectingthat the alfalfa is not conducive in improving the soil quality of farmland. Comprehensively,in the choice of vegetation species in the test area, the Robinia pseudoacacia and Caragauakorshinskii is the priority selection, followed by Prunus armeniaca L and poplar. Theimprovement of farmland soil quality among the wasteland and other vegetation conditions isnot obvious.