亚热带常绿阔叶林土壤胞外酶活性对碳输入变化及增温的响应

Responses of soil extracellular enzyme activities to carbon input alteration and warming in a subtropical evergreen broad-leaved forest

土壤胞外酶来源于土壤微生物、植物和动物,是土壤生物地球化学过程的积极参与者,在森林生态系统的物质循环和能量流动过程中扮演着重要角色。为探明土壤胞外酶活性对碳输入变化及增温的响应,该研究基于长期增温、去除地表凋落物(以下简称去凋)和切根处理的云南哀牢山亚热带常绿阔叶林控制实验平台,研究了不同处理(对照、去凋、切根、切根并增温)下表层矿质土壤(0–5和5–10 cm)与碳氮磷获取相关的胞外酶活性,包括多酚氧化酶(POX)、过氧化物酶(PER)、β-葡萄糖苷酶(BG)、β-1,4-N-乙酰氨基葡萄糖苷酶(NAG)和酸性磷酸酶(AP)。结合铵态氮(NH4+-N)含量、硝态氮(NO3–-N)含量、溶解有机碳(DOC)含量、溶解总氮(DN)含量、土壤含水量(SWC)等相关指标,探讨凋落物碳输入、根系碳输入和温度变化对土壤胞外酶活性及其生态化学计量特征的影响。研究结果表明:在对照样方,除POX外其余酶活性均为0–5cm层显著高于5–10cm层。与对照相比,长期的凋落物去除显著降低了0–5 cm层土壤AP和BG活性,对NAG、PER和POX活性则无显著影响;长期切根处理显著降低了0–5 cm层土壤BG活性,但提高了两个土层PER活性;长期切根并增温处理显著降低了0–5 cm层AP和BG活性,对其余酶活性无显著影响。冗余分析结果显示SWC和NH4+-N含量是驱动土壤酶活性变化的重要因子。本研究为该生态系统土壤碳氮磷生物地球化学关键过程对全球变化的响应提供了土壤酶学的依据。

Aims The objective was to investigate the responses of soil extracellular enzyme activities to carbon input alteration and warming in a subtropical evergreen broad-leaved forest of Ailao Mountain,Yunnan,southwest China.Methods This study was based on two soil depths(0–5 and 5–10 cm)for four treatments under a long-term soil warming experiment in a subtropical evergreen broad-leaved forest of Ailao Mountain,Yunnan,southwest China.Potential activities ofβ-glucosidase(BG),polyphenol oxidase(POX),peroxidase(PER),β-1,4-N-acetylglucosaminidase(NAG)and acid phosphatase(AP)and their stoichiometric ratios were measured.Soil physical and chemical properties were also analyzed.Important findings The results showed that in the control treatment,activities of all enzymes except POX decreased significantly with soil depth.Compared with the control treatment,long-term litter removal significantly reduced AP and BG activities at 0–5 cm soil depth,but had no significant effect on NAG,PER and POX activities at both 0–5 and 5–10 cm soil depths.Long-term root removal significantly reduced BG activity at 0–5 cm soil depth,while increased PER activity at both soil depths.Long-term root removal and warming treatment significantly reduced AP and BG activities at 0–5 cm soil depth,but had no significant effect on activities of other enzymes at both soil depths.The results of redundancy analysis showed that soil water content and NH4+-N content were likely important factors driving the changes soil enzyme activities among treatments.This research provides critical information on the activities of soil enzymes related to carbon,nitrogen and phosphorus cycling in response to global change in this subtropical forest ecosystem.