Effects Of Land Use Types And Slop Aspects On Soil Quality In The Arid Area Of Northern Weihe River Basin

This study firstly focused on effects of land use type and slope aspect on soil quality in Weibei rainfed highland. We selected five typical and representative land use types as study sites, which were Artificial forestland(Robinia pseudoacacia, AF), artificial grassland(alfalfa,AG), natural grassland(NG),farmland(rotation with wheat and corn) and abandoned farmland, respectively. Field survey and soil samples in 0-30 cm soil layer were collected to analyze soil physical, chemical and biological properties and their relationships between each other. Further to indicate responses of soil quality to changes of land use type and slope aspect, to make an evaluation for soil quality and provide theoretical foundation and scientific basis for land management, protection and effective use in this area.The main results were as follows:1. Changes in soil physical indicators in response to land use type and slope aspect were as follows. Soil water content decreased with increased soil depth, and soil water content in shady slope were basically higher than that in sunny slope. AG and NG owned higher soil water content. Soil bulk density basically increased with increased soil depth, and AF owned lowest value in soil bulk density with more reasonable forest community structure. Soil bulk density in sunny slope was higher than that in shady slope. Soil porosity decreased with increased soil depth, and it was higher in AF, which effectively improved soil infiltrationcapacity and further improved soil water storage. Soil mechanical composition analysis showed that proportion of silt particle in soil was higher than that of clay particle, and sand particle owned the smallest proportion in soil.2. Changes in soil chemical indicators in response to land use type and slope aspect were as follows. Soil organic carbon concentration in upper soil layer was highest, and it decreased with increased soil depth. Soil organic carbon concentrations in AF and NG were significantly higher than those in other three land use types(P<0.05). Soil total nitrogen concentration decreased with increased soil depth, and it was highest in AG, especially in shady slope, which significantly higher than that in other four land use types(P<0.05). Soil owned a large ratio of C to N, which slowed down litter decomposition process, and soil quality was generally poor in study area.3.Changes in soil biological indicators in response to land use type and slope aspect were as follows. Soil microbial biomass carbon contentraiton decreased with increased soil depth, while AF owned a significant higher concentration than other four land use types(P<0.05), and so as shady slope was higher than sunny slope. Soil microbial biomass nitrogen concentration decreased with increased soil depth, and AF and AG owned higher concentrations. Soil microbial biomass C: N ratio changed with soil depth with no clear pattern, and that in shady slope was higher than that in sunny slope.4. Evaluation of soil quality was as follows: AG > farmland >AF > NG > abandoned farmland. There were no significant differences in soil quality scores among five land use types, which generally were lower, indicating soil in study area had poor quality. However, AF scored highest in soil quality, thereby it could be treated as the best approach for soil resource protection and utilization.