氮添加和采脂对湿地松林土壤酶活性及酶化学计量比的影响

大气氮沉降和采脂会引起树木生长和代谢的变化，从而影响土壤养分循环和酶活性。土壤酶和酶化学计量可以揭示土壤碳、氮循环和微生物生长代谢过程的养分限制，但目前亚热带湿地松人工林土壤酶和酶化学计量对氮添加和采脂的响应还不清楚。以亚热带北缘的湿地松人工林为研究对象，设置采脂(resin tapping, RT)和未采脂(no resin tapping, NRT)样地，开展不同强度氮添加(对照0 kg N·hm^-2·a^-1、低氮50 kg N·hm^-2·a^-1、高氮100 kg N·hm^-2·a^-1)试验，探讨氮添加和采脂对湿地松人工林土壤酶活性和酶化学计量比的影响。结果表明：采脂显著降低土壤pH、全磷(TP)含量和微生物生物量碳(MBC),显著增加了土壤可溶性有机碳(DOC)含量；氮添加显著降低了TP、DOC含量；氮添加和采脂对土壤DON和NH₄~+-N含量具有交互影响作用；采脂显著降低土壤过氧化氢酶(CAT)活性和土壤蔗糖酶/酸性磷酸酶(E...

Effects of nitrogen addition and resin tapping on soil enzyme activities and their stoichiometry in a slash pine plantation

Atmospheric nitrogen deposition and resin tapping alter tree growth and metabolism,with consequences on soil nutrient cycling and enzyme activities.Soil enzymes and enzymatic stoichiometry can reveal soil carbon and nitrogen cycling and the nutrient limitation of microbial growth and metabolic processes.However,the responses of soil enzymes and enzymatic stoichiometry to nitrogen addition and resin tapping of slash pine(Pinus elliottii)plan-tation in subtropical area are still unclear.In this study,a field experiment was conducted to examine the effects of three nitrogen addition levels(CK:0 kg N·hm^-2·a^-1;LN:50 kg N·hm^-2·a^-1;HN:100 kg N·hm^-2·a^-1)and resin tapping(RT,resin tapping;NRT,no resin tapping)on the activities of soil hydrolytic enzyme,oxidation enzyme,and their stoichiometry in a slash pine plantation.Resin tapping significantly decreased soil pH,total phosphorus(TP)content and microbial biomass carbon(MBC),while significantly increased dissolved organic carbon(DOC)content.Nitrogen addition significantly reduced soil TP and DOC contents.Nitrogen addition and RT interactively affected the contents of dissolved organic nitrogen(DON)and ammonium nitrogen(NH₄⁺-N).Resin tapping significantly decreased the activity of soil catalase(CAT)and the ratio of soil sucrase/acid phospha-tase(E_C/P),but significantly increased the activity of soil acid phosphatase(ACP).HN addition significantly sup-pressed soil urease(URE)activity in NRT stands,while LN addition significantly promoted CAT activity in RT stands.In the NRT stands,N addition significantly decreased soil E_N/P,while HN addition significantly increased soil E_C/N.Results of redundancy analysis showed that changes in soil enzyme activity and enzymatic stoichiometry were mainly driven by the variations of soil TP and DOC content under N addition.In conclusion,N addition exac-erbated soil microbial C and P limitation,and N addition and resin tapping changed soil C,N and P cycling in slash pine plantations.