常绿阔叶林碎屑食物网结构与养分级联效应的调控机制及其对环境梯度变化的响应

Detritus food webs is a complex core for organic N, nutrient resources and biodiversity gathering in a forest ecosystem, together with feedback of land plants, they are critical to maintain biodiversity and nutrient cycling. All existing theories and hypotheses about detritus food webs were based on simple ecosystem, which is hard to explain the regulation and control mechanism of detritus food webs in tropical and subtropical forests. Although few studies had been conducted about detritus food webs in tropical and subtropical forests, they overlooked the interaction effects between herbivores on plant populations and cascading effect of predators. This research will focus on two kind of evergreen broad-leaved forests in two climate zones, by using investigation and manipulation experiments to survey the structure, distribution patterns of detritus food webs and the relationship with their habitats; then integrate with plant diversity to explore the interaction between resources control and the strength of different trophic levels (species or groups) in detritus food webs, and the relationships with their ecological processes; meanwhile, analyze herbivores on plant populations and possible cascading effect of predator spiders in bottom-up effects in resources control processing. Then we will probe into the functional roles of species and functional diversity in ecosystems integrating our results from two-dimensional trophic levels (horizontal and vertical diversity), and find out the response patterns of detritus food webs structures and functions to the environmental gradient changes. This study will provide reliable data for predicting effects of biodiversity loss or biological invasions to ecosystem, and ecosystem restoration.

碎屑食物网是森林土壤有机碳、养分资源和生物多样性集聚的复杂核心体，其与地上植物的相互反馈作用是维持生物多样性和驱动养分循环的动因。已有来自简单系统的食物网理论和假说难以解释热带和亚热带森林碎屑食物网的调控机制，少有的研究也忽略了地上虫食和地下捕食效应的交互影响。本研究拟选取两种不同气候带常绿阔叶林，采用野外调查和人工操控试验方法，在充分了解碎屑食物网结构、分布格局与生境关系的基础上，进一步结合植物多样性探讨资源调控与碎屑食物网各营养级物种（类群）的相互作用强度及其与生态过程的耦合关系，并分析地上虫食和地下捕食者蜘蛛在资源上行调控过程中可能产生的级联效应。融合水平和垂直二维方向的结果理解物种和功能群多样性在生态系统中的作用和价值。同时了解常绿阔叶林碎屑食物网结构和功能对环境梯度变化的响应格局。有望为预测多样性丢失所产生的效应或生物入侵对生态系统所带来的影响，以及生态系统恢复提供有力的支持。

碎屑食物网与地上植物的相互反馈作用是维持生物多样性和驱动养分循环的动因。研究选取不同气候带常绿阔叶林为生境，采用野外调查和人工操控试验方法，探讨碎屑食物网各营养级主要功能群的群落构建、相互作用强度及对分解的调控作用，深入分析了地表捕食者蜘蛛下行作用对系统的级联效应。主要结果表明：1.热带、亚热带常绿阔叶林土壤动物群落以弹尾目、蜱螨目、食细菌线虫与植食性线虫为主要优势类群（60%的物种），线虫群落具有显著的集聚分布格局；环境异质性（pH、N:P、NO3-N、乔木集群结构）是驱动土壤线虫群落呈现空间异质性分布的主要因素，且作用强度随尺度增大而增强。2.凋落物质量、土壤动物和海拔均对凋落物分解有显著的独立和交互作用。热带常绿阔叶林凋落物年分解率显著快于亚热带阔叶林，其土壤动物群落对森林凋落物分解的贡献平均为67.98%，亚热带常绿阔叶林为18.03%，且低海拔生境土壤动物对来自高海拔生境的凋落物分解有更为显著的作用。3.土壤真菌多样性与倒木分解速率有显著的负相关关系，其对倒木分解速率呈现“净多样性”效应，真菌群落中潜在的干扰竞争调控倒木分解过程，真菌群落与季节温湿度的相互作用是导致湿暖季节倒木分解减缓的主要原因，暗示气候变化导致的微生物多样性增加将延缓植物残体分解C释放过程对生态系统具有重大意义。4.不同捕食策略地表蜘蛛通过影响土壤动物分解者群落结构对凋落物分解速率的产生不同的级联效应，呈现为游走型蜘蛛促进了凋落物分解，而结网等待型蜘蛛的级联影响不显著；环境变化如干旱和N沉降通过改变系统中土壤动物的群落结构，以及调节土壤微生物和基质质量而影响蜘蛛对凋落物分解速率的级联效应。以上研究结果融合了水平和垂直二维方向上生物多样性变化解答土壤动物功能群在森林生态系统中的作用和价值，同时了解常绿阔叶林碎屑食物网结构和功能对环境梯度变化的响应格局，为建立不同气候带常绿阔叶林碎屑食物网结构和功能的调控模型提供了可靠的试验数据和理论基础。