| Slope orientation is thought to be a strong push for changes in soil nutrient cycling and availability by affecting microclimates(eg solar radiation input)and erosion processes.Due to different slope orientations,soil temperature and soil moisture are very different.Soil enzyme activity and nutrients are important indicators for evaluating soil quality and health.In this paper,the soil in different slopes of three valleys in the eastern section of Qilian Mountains in Tianzhu County,Wuwei City,Gansu Province was taken as the research object.Soil enzyme activities(urease,invertase,catalase,neutral phosphatase and ?-glucosidase)and glomalin-related soil protein(GRSP)were analyzed in different slopes.Combining physical and chemical properties of soil for analysis of variance,one-dimensional regression analysis,multiple regression analysis and redundancy analysis to explore the relationship between soil enzyme activities,GRSP,and soil physiochemical factors in different slope directions in the eastern section of Qilian Mountains.1.Studies have shown that the activity of soil urease,invertase and catalase on the South slope was significantly higher than the North slope.Neutral phosphatase,?-glucosidase activity and GRSP were higher on the North slope than on the South slope.Neutral phosphatase activity and GRSP were not significantly different in different slopes in XSTG.The increase of soil temperature will lead to the increase of enzyme activity(urease,sucrase),so the difference in temperature caused by different slope directions may have an impact on soil enzyme activity.2.The correlation of soil enzyme activity and GRSP with individual soil physicochemical properties on different slopes were analyzed.It was found that in the South slope there was a significant negative correlation between soil enzyme activity and GRSP with pH and available phosphorus,and there was a significant positive correlation with soil water content,organic carbon,total nitrogen,available nitrogen,and available nitrogen(AN:AP),and there was no significant correlation with the bulk density.Urease activity and water content were negatively correlated,while neutral phosphatase was negatively correlated with pH in the North slope.?-glucosidase activity was not significantly correlated with pH,moisture and available nitrogen on the South slope.There was also no significant correlation between ?-glucosidase activity and any soil factor in North slope.In short,whether it is a South or North slope,the soil enzyme activity and GRSP are related to organic carbon,total nitrogen and available phosphorus,but the comparison found that the South slope may be mainly affected by soil pH,soil moisture content,and nutrient availability.Soil moisture content is the limiting factor of soil enzyme activity and GRSP on South slopes.The pH value of the North slope is low(7.0-7.15),the soil moisture content is high(40%-44%),and the soil enzyme activity and GRSP may be mainly affected by available nutrients in the soil.3.The correlation of soil enzyme activities and GRSP with several soil physicochemical properties on different slopes were analyzed.It was found that in addition to pH,organic carbon,available phosphorus and water content,etc.,all the enzyme activities and GRSP were found to be related to soil total nitrogen in the South.In addition to urease activity on the North slope,it also has certain relation with soil total nitrogen.However,the availability of nitrogen is not high.Therefore,the low level of available nitrogen in the soil leads to a relatively high input of microorganisms to the nitrogen-harvesting enzyme(urease),indicating that the available nitrogen is severely restricted in Qilian Mountains,especially on South slopes.From this aspect it can be inferred that the production of soil enzymes is closely related to the availability of resources.4.The enzyme activity interacts with different soil physicochemical factors and with other related soil proteins,providing energy and nutrients for the organism in the soil ecosystem. |
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