生物多样性 ›› 2021, Vol. 29 ›› Issue (11): 1447-1460.DOI: 10.17520/biods.2021240

• 研究报告:植物多样性 • 上一篇    下一篇

亚热带森林树种多样性对凋落叶分解胞外酶活性的影响

潘玉梅, 张乃莉()   

  1. 北京林业大学林学院森林培育与保护教育部重点实验室, 北京 100083
  • 收稿日期:2021-06-16 接受日期:2021-07-30 出版日期:2021-11-20 发布日期:2021-08-17
  • 通讯作者: 张乃莉
  • 作者简介:E-mail: zhangnaili@bjfu.edu.cn
  • 基金资助:
    北京林业大学中央高校基本科研业务费专项资金资助(BLX202012);国家自然科学基金(32071644)

Effects of tree diversity on enzyme activity in litter of a subtropical forest ecosystem

Yumei Pan, Naili Zhang()   

  1. Key Laboratory for Silviculture and Conservation of Ministry of Education, College of Forestry, Beijing Forestry University, Beijing 100083
  • Received:2021-06-16 Accepted:2021-07-30 Online:2021-11-20 Published:2021-08-17
  • Contact: Naili Zhang

摘要:

森林生物多样性与生态系统功能关系是当前群落生态学的热点研究领域。然而, 以往研究更多聚焦在森林植物多样性丧失对群落生产力的影响, 而对森林凋落物分解的相关研究稍显不足。森林凋落叶分解的快慢直接受控于凋落物分解者分泌的胞外酶的活性, 后者更是指示森林生态系统养分循环的重要指标之一。本研究依托我国江西亚热带森林生物多样性与生态系统功能控制实验, 通过对不同植物多样性梯度样方内目标树种凋落叶胞外酶活性、理化性质以及腐生真菌的分析, 探索树种多样性丧失对胞外酶活性的影响及其调控机制, 以探讨森林树种多样性对地表、地下生态过程和功能的影响。结果表明, 样方水平树种多样性丧失显著影响胞外酶的活性, 除单种样方外, 随着样方水平树种丰富度的增加, 胞外酶活性呈现出增长趋势; 与碳周转相关的α-葡萄糖苷酶(AG)、β-葡萄糖苷酶(BG)、纤维二糖水解酶(CB)在树种多样性最大时活性达到最高; 而木糖苷酶(XS)以及与氮、磷和顽拗有机养分分解相关的N-乙酰-β-氨基葡萄糖苷酶(NAG)、酸性磷酸酶(AP)和多酚氧化酶(PPO)在树种多样性较低时活性较高。针对目标树种周围的邻居树种多样性进一步分析发现, 各胞外酶活性随着邻居树种多样性的变化呈“单峰”响应趋势, 酶活性大多在邻居树种丰富度为6时呈现峰值。研究发现真菌分解者在胞外酶活性对植物多样性的响应上可能存在重要的调控作用, 可以推测树种多样性通过改变腐生真菌分解者的群落结构和多度, 从而影响胞外酶活性。

关键词: 酶促降解, 凋落叶分解, 树种多样性, 邻居树种多样性, 腐生真菌, 亚热带森林

Abstract

Aims There is a growing concern regarding biodiversity loss and its effects on ecosystem functioning. Previous studies have primarily focused on the impact of biodiversity loss on plant productivity in forest ecosystems, but research regarding its effects on enzyme-mediated litter decomposition remains elusive. It has been well documented that the rate of litter decomposition is directly controlled by the activities of extracellular enzymes secreted by microbial decomposers, which is an important indicator of nutrient cycling in forest ecosystems. To explore the effect of biodiversity loss on extracellular enzyme activities in litter, and the underpinning mechanism that regulates litter decomposition, a field experiment was conducted in a subtropical forest.
Methods The experiment was conducted in a subtropical forest biodiversity-ecosystem functioning experimental area established in Xingangshan, Jiangxi Province. In this study area, 31 intensively studied plots which form a gradient of tree species diversity (i.e., 16 monocultures, eight 2-species mixtures, four 4-species mixtures, two 8-species mixtures and one 16-species mixture) were chosen. We collected fresh-fallen leaf litter in the plots of varying tree diversity levels and measured the extracellular enzyme activity, chemicals, and fungi in litter. We hypothesized that extracellular enzyme activities in litter, particularly those relevant to carbon (C), nitrogen (N), and phosphorus (P) cycling would significantly change with tree species diversity loss. We also expected to find that fungal decomposers could modulate the responses of enzyme activities to tree species diversity loss.
Result Our results showed that tree species diversity loss significantly affected the activities of extracellular enzymes, and extracellular enzyme activity showed a positive correlation with increasing tree species richness, except for single species. The activities of α-glucosidase (AG), β-glucosidase (BG), and cellubiosidase (CB), which are involved in C turnover, were the highest in the litter from the plot with the highest tree species diversity. Xylosidase (XS), N-acetyl-β-glucosaminidase (NAG), acid phosphatase (AP), and polyphenol oxidase (PPO), which are respectively involved in the turnover of N and P and the degradation of polyphenol, had higher rates of activity when the tree species diversity was lower. Moreover, we found that the extracellular enzyme activities showed a ‘single peak’ trend that correlated to changes of neighboring tree species diversity. This trend indicates that most of the extracellular enzyme activities relevant to the turnover of C, N and P were highest when the species richness of the six neighboring tree species was high as well. These findings indicate that both plot-level tree diversity and neighboring tree species can significantly alter extracellular enzyme activities in litter of target tree species. Fungal decomposers may play an important role in affecting the response of extracellular enzyme activities to tree species diversity loss.
Conclusions Our findings demonstrate that the loss of tree species diversity may indirectly affect extracellular enzyme activity by influencing the community structure and abundance of fungal decomposers. This study promotes our understanding of how tree diversity loss influences litter degradation and nutrient release through the modulation of extracellular enzyme activities in subtropical forests.

Key words: enzymatic degradation, litter decomposition, tree species diversity, neighboring tree species diversity, saprotrophic fungi, subtropical forest