Distribution And Mineralization Characteristics Of Soil Nitrogen In Alpine Shrub Meadow Of The Western Sichuan

Soil nitrogen not only affects the productivity of forest ecosystem,but also influences the biogeochemical cycle.It is an extremely important ecological factor in the ecosystem.Based on sichuan province ganzizhou SheDuoShan alpine mountain shrub meadow soil as the research object,adopt the method of field investigation and indoor analysis,soil nitrogen,the research of different elevation gradient SheDuoShan changes of time and space of soil nitrogen mineralization characteristics of a systematic study,in order to reveal SheDuoShan spatial and temporal distribution and mineralization of soil nitrogen,in western sichuan ecosystem restoration of degraded alpine mountain forest and provides the theory basis for reasonable utilization of resources and environmental protection.The main research results are as follows:?1?the contents of nitrogen components in the soil on the yin-yang slopes at all elevations and seasons were significantly higher in the leaching layer than in the deposition layer?P<0.05?,and the contents of nitrogen components in the soil were generally higher in the half-shade slope than in the half-sunny slope.?2?the contents of soil total nitrogen,soil nitrate nitrogen and microbial biomass nitrogen were positively correlated with altitude.The cumulative mineralization of soil in the sunny slope showed an increasing trend with the decrease of altitude,and the soil mineralization at 3800 m was significantly higher than that at other elevations?P<0.05?.The accumulation of soil nitrogen mineralization in overlying slope was positively correlated with the altitude,and the content of soil nitrogen mineralization in overlying slope was relatively low at 3800m.?3?the contents of soil accumulated nitrogen mineralization,soil microbial biomass nitrogen,total nitrogen,alkali-hydrolyzed nitrogen and nitrate nitrogen decreased from pre-freeze-thaw to post-freeze-thaw,and increased from freeze-thaw to growth season;The seasonal change of ammonium nitrogen in soil is just the opposite.The content of ammonium nitrogen increases before freezing-thawing and decreases after freezing-thawing.?4?the one-component first-order model of soil nitrogen mineralization has a high degree of fitting,in which the mineralization rate constant k has no obvious seasonal change rule and the change rule of altitude.As a whole,the mineralization potential N₀ of organic nitrogen is positively correlated with altitude.the mineralization rate of soil organic nitrogen gradually decreased with the passage of time.The first 14 days of the mineralization rate of organic nitrogen were significantly higher than that of the last 21days,and the first 7 days of the mineralization rate of soil organic nitrogen had the largest decline.With the passage of time,the mineralization rate of soil organic nitrogen also gradually decreased,with a decreasing range.?5?There is a correlation between soil physical and chemical factors and soil nitrogen mineralization,and they will show different proportions of influence due to different environments.Soil organic matter content has the greatest influence on soil nitrogen mineralization in negative slopes,while soil total nitrogen content is the most influential factor in positive slopes.