Effects Of Nitrogen And Biochar Addition On Soil Ecological Enzyme Activity And Chemometric Characteristics In A Moso Bamboo Plantation

As one of the important participants in soil biochemistry,the study on the activities of ecological enzymes is a useful tool to evaluate the function of soil microbial community or the turnover of soil organic matter.The activity of β-glucosidase(BG),β-N-accty lglucosamimidase(NAG),leucine amino pcptidase(LAP)and acid phosphatase(ACP)is used as an important indicator of nutrient acquisition and resource allocation for microorganisms during carbon(C),nitrogen(N)and phosphorus(P)acquisition,respectively.At present,under the background of increasing atmospheric nitrogen deposition,the effects of biochar addition on soil ecological enzyme activities and stoichiometric characteristics of moso bamboo plantation are still unclear.In this study,we studied four nitrogen level intensities(control:0 kg N ha-1 Yr-1,low nitrogen:30 kg N ha-1 Yr-1,medium nitrogen:60 kg N ha-1 Yr-1 and high nitrogen:90 kg N ha-1 Yr-1)and three gradient biochar(control:The effects of 0 t ha-1,low biochar:20 t ha-1 and high biochar:40 t ha-1)and their combinations on soil ecological enzyme activities and stoichiometric characteristics of moso bamboo plantation,and the changes of soil microbial biomass and soil nutrient contents were measured.The main results were as follows:(1)Nitrogen addition significantly increased the activities of BG and NAG+LAP by 27.8%-35.9%and 16.4%,respectively;The ACP activity was significantly decreased by 15.5%in medium nitrogen treatment.At the same time,nitrogen addition significantly increased the enzyme C/P ratio and enzyme N/P ratio by 2.6%-6.1%and 3.5%-7.8%,respectively.(2)Biochar significantly increased the activity of BG by 59.6%;High biochar significantly reduced NAG+LAP activity by 47.1%,but had no significant effect on ACP.At the same time,with the increase of biochar addition level,the enzyme C/N ratio and enzyme C/P ratio increased significantly,increasing by 6.1%-16.2%.and 7.8%-10.4%,respectively.(3)Under low and high nitrogen treatments,biochar addition significantly increased BG activity by 32.4%-153.3%;However,under low and medium nitrogen treatments,biochar addition significantly decreased NAG+LAP activity by 16.5%-48.1%.Under low nitrogen treatment,biochar significantly increased the enzyme C/N ratio and enzyme C/P ratio by 17.2%-19.2%and 11.9%,respectively.However,in the case of nitrogen addition,biochar significantly reduced the enzyme N/P ratio by 3.2%-7.6%.In this study,it was found that the addition of biochar partially enhanced the positive activation effect of nitrogen on BG activity,and to a large extent offset the positive activation effect of nitrogen on NAG+LAP activity.Under the background of nitrogen addition,biochar addition alleviated soil microbial nitrogen limitation.In general,our results indicate that the addition of biochar can significantly change the effects of nitrogen deposition on soil ecological enzyme activities and stoichiometric characteristics,which is an effective way to promote the sustainable operation of Moso bamboo plantation under the context of increasing nitrogen addition.