| Soil enzyme is an important indicator of soil biological activity in the ecosystem.The activity of soil enzyme in arid desert area is mainly restricted by soil water,temperature and soil depth.It can provide theoretical basis for scientific management of vegetation and ecological environment to study the response of soil enzyme activities to precipitation regulation in Xiao hong-shan area.By using the rain-shelter and drip irrigation system to control precipitation input in the field experimental platform,five precipitation gradients were designed in this study,including extreme drought treatment?-50%,D1?,drought treatment?-25%,D2?,precipitation increase I?+50%,W1?,precipitation increase II?+25%,W2?,natural rainfall?RE?and control group?CK1?CK2?.The changes of soil protease,amylase,catalase,alkaline phosphatase,urease,cel ulase and invertase were studied by artificial control of precipitation.Its correlation with the soil physical and chemical properties and climate.And the change of soil enzyme activity in different seasons and different depths.The results of this study are shown as follows:?1?The seven soil enzyme activities studied in this paper were significantly differe nt from the seasonal factors?P<0.01?.The temperature and precipitation in the study area reached the highest in summer.Suitable temperature and humidity are beneficial to the breeding of soil microbes.At the same time,plant growth is flourishing,and the growth of plant roots will also have a certain effect on the activity of soil enzyme.Protease activity was consistent with catalase activity.When the summer temperature was the highest,the enzyme activity reached the maximum value.When entering the autumn,the activities of two soil enzymes all decreased,and the activity of enzyme increased again after entering winter.The activities of alkaline phosphatase,cel ulase and sucrase were the same.In spring,summer and autumn,the content of alkaline phosphatase,summer and autumn was higher than that in winter.The transformation of phosphorus in the soil is more affected by temperature and precipitation.?2?The study area belongs to the arid semi desert area.The soil fertility is low,and the vegetation is mainly herbaceous and small shrubs.Only the soil surface contains less litter and humus,which provides limited environmental conditions for microbial survival and development.Moreover,the precipitation in the arid area is scarce.In contrast,the soil surface water and heat conditions are better,and the permeability of the soil is good.Most of the precipitation stays on the surface.With the increase of the soil depth,the temperature decreases and the humidity decreases,and the soil enzyme activity decreases.Soil protease,amylase,catalase,alkaline phosphatase and urease activity showed a trend of decreasing enzyme activity with the increase of soil depth,and enzyme activities in the surface soil accounted for a larger proportion of total soil enzyme activities.The activity of soil celulase increased first and then decreased with the change of soil depth.The activity of invertase in soil decreased with the increase of soil depth.The vertical variation of soil enzyme activity is different,which may be due to the difference in the soil and climate environment in the study area.?3?The effects of different precipitation gradients on soil enzyme activity were analyzed in the experiment.Under the condition of different precipitation control,single factor variance analysis showed that the protease,alkaline phosphatase,urease and invertase activity was significantly different on soil enzyme activity?P<0.01?,and catalase,amylase and celulase activity had no significant difference?P>0.05?.The activity of soil protease decreased first and then increased with the increase of water content,the range of change is between 1.14-1.45?g·g-1·24h-1.There was no obvious change in the activity of amylase and catalase in soil.The activity of alkaline phosphatase increased with the increase of water content,the range of change is between 0.59-0.71 mg·g-1·24h-1.The activity of soil urease,celulase and invertase increased first and then decreased with the increase of water content,the range of change is between 0.32-0.37 mg·g-1·24h-1?0.22-0.29 mg·g-1·72h-11 and 2.59-3.77 mg·g-1·24h-1.The activity of soil enzyme is greatly influenced by environmental factors.In the analysis of its changes,the influence of environmental factors on the changes of soil enzymes should be considered.This paper mainly deals with the effects of three factors on soil enzyme activities,such as season,soil depth and rainfall control.We should combine the interaction of three factors and the biochemical properties of enzymes on their activities.?4?Principal component analysis of 7 soil enzymes showed that the cumulative variance contribution rate of the first 4 factors reached over 73%.Catalase,alkaline phosphatase and celulase were better than other enzymes in evaluating the comprehensive function of soil enzyme activities.Comprehensive index analysis showed that ENCI showed significant difference in interannual variability,seasonal change and soil depth change,while the difference in precipitation control was not obvious.?5?The correlation between soil enzyme activities and physical and chemical properties of soil is inconsistent.Soil enzymes are highly specific,and are affected by various physicochemical properties in the process of soil biological metabolism and material transformation.The activities of soil urease and cellulase have good correlation with soil total phosphorus,available phosphorus,electrical conductivity,pH,water content,microbial carbon and microbial nitrogen.The correlation between other enzyme activities and soil physical and chemical properties is not good.The physical and chemical properties of soil are influenced by the regulation of precipitation,and there are no significant differences in other properties except soil pH value and microbial carbon and nitrogen. |
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