典型森林生态系统蚯蚓生态位的时空演变规律

The potential positive influences of soil biota on sustainable agroforestry have been increasingly recognized. Earthworms are decomposers, regulators, consumers and even predators in ecosystems, and involved in most of the physical, chemical and biological processes in soils. The changes in earthworm community may trigger a butterfly effect and alter ecosystem services profoundly. Thus, a great opportunity emerges for scientists to explore the functioning of soil biota in the sustainable agroforestry by focusing on the connections between the changing earthworm community and ecosystem processes. However, previous studies fail to do this due to two major obstacles. On the one hand, studies based on controlled experiment such as microcosm incubation have simplified the complex spatial-temporal interactions among ecosystem components. Hence, a biased and static function of earthworms could be illustrated by this approach. On the other hand, studies based on field survey of earthworm community could not recognize the earthworms’ primary role due to technical limitations. In this project, we aim to explore the feature and spatial-temporal patterns of the changing ecological niche of earthworms in typical forest ecosystems across biomes in China. A holistic approach, based on combined analysis of the datasets of stable isotope abundance, fatty acid profile, and high-throughput DNA sequencing, will be performed to trace the dynamic connections between the biological traits of earthworm community (e.g., trophic level and community size) and characteristics of vegetation and/or soil (e.g., soil fertility). This study would provide relevant scientific bases for applying earthworm-based techniques to the sustainable agroforestry.

土壤生物在可持续农林业中的潜在作用日益得到关注。蚯蚓在生态系统中扮演着分解者、环境调节者、消费者、甚至捕食者的角色，几乎参与了土壤中所有物理、化学和生物学过程。蚯蚓群落的变化“牵一发而动全身”，可能深刻影响生态系统服务功能，为开展土壤生物与可持续农林业研究提供了绝佳契机。但是已有的研究：或基于微宇宙培养等控制实验，割裂了生态系统中各组分之间复杂的时空联系，是故仅揭示了局部的和静态的蚯蚓生态功能；或仅限于野外蚯蚓群落调查，囿于落后的研究技术，以至于难以区分和比较蚯蚓扮演的各种“角色”的相对贡献。本项目拟从蚯蚓生物学属性（如群落大小和营养级水平）与植被和土壤属性（如土壤肥力）关系的动态变化入手，综合应用稳定同位素、脂肪酸图谱和高通量测序等新技术探究我国典型森林生态系统中蚯蚓“生态位”的内涵及其时空变化规律，为发挥蚯蚓在可持续农林业中的贡献提供科学依据。

探究蚯蚓生态位的内涵及其随着森林发育（演替）的变化规律是理解蚯蚓-植物-微生物关系的重要切入点，更是保护蚯蚓多样性并发挥其生态功能的重要基础。为揭示我国典型森林生态系统蚯蚓生态位的时空演变规律，本研究选取温带的长白山、南北气候过渡区的宝天曼、以及南亚热带的鼎湖山等地，开展不同纬度不同发育阶段森林生态系统蚯蚓群落组成、群落大小和营养级特征的系统研究。结果表明：1）对于北方的森林（长白山和宝天曼）来说，蚯蚓密度和生物量与土壤肥力（土壤碳、氮含量）明显负相关，但在南方的鼎湖山，蚯蚓则主要与凋落物钙含量正相关，与土壤pH值负相关。2）在长白山，蚯蚓群落大小在40年林龄森林中最高。该生态系统有土壤肥力低、细根生物量大、凋落物分解快、真菌细菌比高、细菌相对受胁迫等特征，推测该生态系统中微生物对蚯蚓的依赖强，故蚯蚓可获取相对多的资源；该生态系统中蚯蚓的15N自然丰度趋于最低，也说明蚯蚓可能处于相对低的营养级，方便其直接参与凋落物的分解并获取资源。3）外来种蚯蚓南美岸蚓在鼎湖山马尾松林的大量分布，可能干扰了蚯蚓群落随森林演替的变化规律。总的来看，随着森林的发育（演替），蚯蚓群落特征存在明显的变化，且植物-微生物对碳和养分的需求与给定生态系统对碳和养分的供给之间的平衡可能影响了蚯蚓在生态系统中的“角色”和重要性。本研究在动态解析蚯蚓生态位方面做了重要的尝试，对建立统一的蚯蚓-植物-微生物协同演变理论有积极意义。