马尾松人工林异龄混交改造对土壤团聚体酶活性及酶化学计量比的影响

Effect sofIntroducing Other Tree Speciesof Different Ages into Pinus massoniana Plantation on Activities and Stoichiometric Ratios of Enzymes Associated with Soil Aggregates

关键词:  马尾松人工林  阔叶树种  异龄混交改造  土壤酶活性  酶化学计量比  养分限制

Key words:  Pinus massoniana plantation  broadleaved tree species  introducing other tree species of different ages  soil enzyme activity  enzyme stoichiometric ratio  nutrient limitation

摘要:

土壤酶活性及酶化学计量比是表征土壤养分限制状况和评估微生物养分需求的关键指标。因此，为探究马尾松(Pinus massoniana)人工林引入一种或多种阔叶树种异龄混交改造对土壤团聚体酶活性和酶化学计量比的影响及其响应机制，本研究以马尾松人工纯林(PP)、马尾松/红锥(Castanopsis hystrix)异龄混交林(MP)、马尾松/多树种异龄混交林(MMP)为研究对象，测定不同林分类型下原土和不同粒径土壤团聚体碳(C)、氮(N)、磷(P)循环相关的酶活性、土壤理化性质、微生物生物量等指标，分析它们之间的关系，并通过冗余分析(RDA)确定影响土壤酶活性及酶化学计量比的最主要因素。结果表明：①异龄混交改造显著改变了土壤酶活性，表现为MP和MMP均显著高于PP，但MP和MMP之间没有显著差异，且酶活性在微团聚体(＜0.25 mm)中最高；②凋落物量、细根生物量、土壤理化性质、微生物生物量与酶活性、酶化学计量比均有不同程度的相关关系，冗余分析发现微生物生物量碳(MBC)、全氮(TN)、全磷(TP)、微生物生物量磷(MBP)、微生物生物量碳磷比(MBC∶MBP)是影响土壤酶活性的主要驱动因子，而TN、MBC和硝态氮(NO₃^--N)是影响酶化学计量比的主要因子；③PP、MP和MMP土壤酶C∶N∶P自然对数比分别为1.20∶1.03∶1、1.17∶1.07∶1和1.16∶1.04∶1,表明3种林分的土壤微生物均对C需求较高，微生物生长代谢容易受C限制，而异龄混交改造能有效缓解林分土壤的C限制。综上，马尾松人工林引入阔叶树种可有效提高土壤酶活性，促进土壤养分循环和改善土壤质量，但在经营过程中需注意适当增施氮肥以维持其高效生产力和可持续发展。

Abstract:

The activities and stoichiometric ratios of soil enzymes are important indicators to characterize soil microbial nutrient demand and nutrient limitation status.This study aims to investigate the effects of introducing broadleaved tree species of different ages into pure Pinus massoniana plantation on the activities and stoichiometric ratios of enzymes in soil aggregates and their response mechanisms.The activities of enzymes involved in carbon (C),nitrogen (N),and phosphorus (P) cycling in original soil and soil aggregates with different particle sizes,soil physicochemical properties,and microbial biomass were measured in a pure P.massoniana plantation (PP),an uneven-aged mixed plantation (MP) of P.massoniana and Castanopsis hystrix,and a multiple species uneven-aged mixed plantation (MMP) of P.massoniana.The relationships between the indicators were evaluated,and the major factors driving the variations in the activities and stoichiometric ratios of soil enzymes were identified.The results showed that:①Introducing other tree species of different ages into the plantation significantly altered soil enzyme activities,which were higher in MP and MMP than in PP and had no significant difference between MP and MMP.The enzyme activities were the highest in microaggregates (<0.25 mm);②Litterfall mass,fine root biomass,soil physicochemical properties,and microbial biomass were correlated with the activities and stoichiometric ratios of soil enzymes.Redundancy Analysis (RDA) revealed that Microbial Biomass Carbon (MBC),Total Nitrogen (TN),Total Phosphorus (TP),Microbial Biomass Phosphorus (MBP),and microbial biomass carbon to phosphorus ratio (MBC∶MBP) were the main drivers affecting soil enzyme activities,and TN,MBC,and nitrate nitrogen (NO₃^--N)were the main environmental factors affecting enzyme stoichiometric ratios;③The stoichiometric ratios of C,N,and P of soil enzymes in PP,MP,and MMP were 1.20∶1.03∶1,1.17∶1.07∶1,and 1.16∶1.04∶1,respectively,which indicated that the soil microorganisms in this area had high demand for C and were easily limited by C source.The findings suggested that introducing other tree species of different ages alleviated the C source limitation of soil microbial growth and metabolism.In conclusion,introducing broadleaved species into the pure P.massoniana plantation can effectively increase soil enzyme activities,promote soil nutrient cycling,and improve soil quality.However,attention should be paid to the application of nitrogen fertilizer in the introducing process in order to maintain the high productivity and sustainable development of the plantation.