川西亚高山不同林龄粗枝云杉人工林土壤微生物生物量及酶活性

Abstract

林分结构随林龄增加发生变化，致使土壤微环境变化，进而对土壤微生物生物量和酶活性产生直接或间接影响。以川西亚高山米亚罗林区25、40、50、60年生粗枝云杉（Picea asperata）人工林表层（0-20 cm）土壤为研究对象，分析不同林龄表层土壤微生物生物量碳（MBC）、氮（MBN）和酶活性的变化以及驱动土壤酶活性变化的主要环境因子，为人工林生态系统恢复效果评价及经营管理提供科学依据。结果表明：随着林龄的增加，MBC和MBN先上升后下降，在40年生达到最大；β-葡萄糖苷酶（βG）、β-N-乙酰氨基葡萄糖苷酶（NAG）和多酚氧化酶（PHO）活性与微生物生物量碳氮变化趋势相似，其中βG、NAG活性在50年生人工林达到最大，PHO活性于40年生人工林达到最大；50年生人工林过氧化物酶（PEO）活性显著低于其他林龄人工林；纤维素水解酶（CBH）活性随林龄增加而显著增加。冗余分析显示，碱解氮（AN）、pH和可溶性有机碳（DOC）是影响土壤酶活性变化的主导因子，分别解释了土壤酶活性变异的65.4%、9.7%和7.6%。综上可知，林龄对粗枝云杉人工林表层土壤微生物生物量和酶活性变化产生了显著影响，60年粗枝云杉林地力呈现衰退态势。为此，可对近60年的粗枝云杉人工林增加碳氮元素（尤其是氮素）的输入，以提升土壤质量和酶活性。;Stand structure changes with forest age caused the variation of soil microenvironment, which can directly or indirectly affect soil microbial biomass carbon and nitrogen, and soil enzyme activities. To better understand the change characteristics of soil microbial biomass contents and enzyme activities along an age sequence of spruce plantations, this study was conducted to evaluate the theoretical basis for restoration and effective management of subalpine plantations. In this study, Picea asperata plantations of various ages (25, 40, 50, and 60 years old) were selected in Miyaluo forest area of western Sichuan, China. The soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), available nitrogen (AN) and pH, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and light fraction organic carbon (LFOC), soil enzyme activity index(β-glucosidase, βG; Cellulose hydrolysis, CBH; β-N-acetylglucosaminidase, NAG; Phenol oxidase, PHO and Peroxidase, PEO) in 0-20 cm soil was measured,respectively. The results showed that the MBC and MBN increased up to 40 years, and then decreased with the increase of age. There was a similar trend in changes of the activities of βG, NAG and PHO, while βG and NAG were highest at 50 years, and PHO was highest at 40 years. PEO activity of 50 years was significantly lower than other plantations. The activity of CBH increased with the increasing age of Picea asperata plantation stands. Redundancy analysis (RDA) indicated that AN, pH and DOC were main influence factors of soil enzyme activities in the top-layer soil, accounted for 65.4%, 9.7% and 7.6% of total variation of soil enzyme activities, respectively. Overall, our results suggested that the growth of Picea asperata had a significant effect on soil microbial biomass and enzyme activities. The soil fertility in 60 years of Picea asperata plantation was the lowest in all Picea asperata plantations. Therefore, we can increase carbon and nitrogen elements (especially nitrogen) devotion to improve soil quality and enzyme activities in Picea asperata plantations nearly 60 years.