增温和氮沉降对青藏高原东缘云杉天然林和人工林土壤食物网结构以及功能的影响

Soil food webs play important roles in biodiversity maintenance and ecosystem productivity. It is very sensitive to climate change such as warming and nitrogen addition. However, the researches on the response of soil food web to climate change are very limited. Especially how soil food webs altered in carbon (C) and nitrogen (N) loss under climate change remain unknown. Therefore, the soil food webs of natural forest and plantation forest of Picea asperata will be studied in the project. Through the observation of soil fauna functional groups and calculation of each function group's contribution to the C and N mineralization by soil food model to detect the structure, key functional groups and species of soil food web under the natural forest and plantation. On the basis of this, we will carry out a field experiment of warming and N addition to study the driving mechanism of warming, nitrogen and its compound effect on the shifting of the structure of food web. Meanwhile we will find the coupling mechanism of global change on the structure and function of soil food webs, This research will analyzes the mechanism of the change of soil food web to the change of C, N mineralization, and evaluates the loss of soil C and N to establish the conjugate relationship of the structure and function of soil food web. It will help us to understand the adaptation of soil organisms under climate change. Feedback mechanism can also provide theoretical basis and technical reference for the restoration and reconstruction of forest vegetation under the background of climate change, and the identification of soil carbon sequestration and carbon source in natural forest and plantation of Picea asperata.

土壤食物网在维持生态系统生产力和生物多样性方面起着重要作用，并对气候变化十分敏感，但我国关于土壤食物网对气候变化的响应研究较为缺乏。本项目拟以云杉 (Picea asperata) 天然林和人工林下的土壤食物网为研究对象，运用土壤食物网模型，计算各功能群对C、N 矿化的贡献，探明天然林和人工林下各自土壤食物网结构和关键功能群。在此基础上，开展模拟增温及施氮野外试验，研究增温、施氮及其复合效应对食物网结构改变的驱动机制，探明全球变化对土壤食物网结构和功能影响的耦合机制，辨析土壤食物网结构变化对氮矿化作用改变的机理，同时评估土壤碳氮损失，通过模型建立其与土壤食物网结构与功能的共轭关系，这有助于深入了解气候变化下土壤生物的适应和反馈机制，也可为川西亚高山更好地促进气候变化背景下森林植被的恢复与重建，辨识天然林和人工林土壤碳汇和碳源的问题提供理论依据与技术参考。

增温和氮沉降是⽓候变化中常见的现象，在青藏⾼原地区更是普遍，但有关其对青藏⾼原森林⽣态系统地下⾷物⽹的结构与功能的影响的报道却⼗分缺乏。本项⽬以⼟壤⾷物⽹作为切⼊点，探讨增温、氮沉降及其复合效应对⼟壤⾷物⽹结构和功能的变化机制，对于全⾯评估这⼀区域内增温和氮沉降态效应具有较重要的科学价值。研究结果表明结果云杉林中不同营养水平的土壤生物（如原生动物、线虫、螨虫）对氮沉降和增温的响应不一致。但是土壤食物网联通度不受增温和N沉降的影响。我们通过食物网结构–能量模型分析显示，土壤食物网受到变暖和N沉降的负面影响，这是由于转移效率的降低（即改变不同营养群体内部的自上而下、自下而上的效应减弱等影响）所导致的，增加食物网中非同化作用的消耗量。暖化和氮沉降对食物网的影响既有直接的，也有间接的。最后，根据营养组的权衡和效益结果，土壤食物网在目前的状态下是最稳定的，而在变暖和N添加的情况下这种稳态会被打破，可能导致食物网内耗增加，高营养级生物损失，最终导致土壤生物多样性受损。这有助于深⼊了解⽓候变化下⼟壤⽣物的适应和反馈机制，也可为川西亚⾼⼭更好地促进⽓候变化背景下森林植被的恢复与重建提供理论依据与技术参考。这是本项⽬将基础和应⽤研究紧密结合的⼀个特⾊之处。