生境调控下红壤食物网结构和功能的时序变化及影响机制

Agriculture sustainability needs efficient management and utilization of soil biodiversity. Although the potential of agricultural management practice in regulating soil community and ecological functions has been well-known, the factors controlling biodiversity and functions in arable soil are not mechanically understood yet. Both organic matter and soil physical structure are of critical importance for soil habitat, as they determine the food resources and refuges of soil biota, respectively. However, very few field experiments aimed to study the dynamics of soil biodiversity and functions by directly manipulating soil habitat. Although numerous earlier studies has demonstrated that agricultural practices such as organic amendments and zero tillage would benefit the development of soil habitat and soil biota in sporadic studies, very few studies considered their integrated effects on the temporal changes of soil food web structure and soil functions. As a result, there is still far from comprehensively understanding the origins of soil biodiversity and their management. A red soil field experiment with factorial design was conducted in subtropical region of Southern China, with resource availability and soil physical structure directly modified by different organic amendments and tillage practice. Based on the hypothesis that soil managements that improve soil habitat would promote soil biodiversity and food web complexity, thus facilitating the biological regulations in agricultural ecosystem services, our study will explore the temporal changes of soil food web (via analyzing typical functional group) and functions (via analyzing plant production and organic matter decomposition). In particular, we will focus on the relationships among soil habitat and soil community/soil functions. To reach those objectives, our study will systematically evaluate soil habitat conditions by determining soil physical structure and organic matter quality, as they might contribute to soil biota development to a great extent. Based on the comprehensive analyses of temporal patterns of soil food web and soil functions, we will disentangle the complex relations among soil habitat and soil community/soil functions. Taken together, our results will help us clarity the mechanisms of how soil ecosystem structure influence soil ecosystem function and to what extent that soil habitat exerted effects. Furthermore, it will also provide scientific guidance for integrating soil biota as biological resource in formulating ecological agriculture managements.

农业的可持续发展迫切需要加强对土壤生物多样性的管理和利用。然而，迄今仍缺乏对农田土壤生物群落和功能调控机制的认识。资源有效性和土壤物理结构是决定土壤生物食物网结构的关键生境要素。因而，针对改善资源和物理结构的保护性措施可以促进土壤生物群落的发展，发挥生物自调节过程在生态系统功能中的作用。本项目以红壤地区有机物施用及免耕措施的野外调控实验为对象，基于土壤生境（有机物质量和物理结构）调控后土壤食物网（代表性功能类群）及生态功能（作物生长和分解过程）的连续监测，阐明土壤食物网结构和功能变化的时序格局；并在探讨土壤生境与食物网结构和功能关系的基础上，揭示土壤生物群落和功能的影响机制。预期结果不仅有助于深化对土壤生态系统结构和功能影响机制的认识，而且为将土壤生物资源的利用纳入生态农业技术管理体系提供依据。

伴随全球变化和人类活动的干扰，生物多样性丧失及生态系统服务的下降已成为农业可持续发展的严峻挑战。同时，伴随生态学知识的进步，生态学理论为农业土壤的生态集约化管理提供了关键的知识。越来越多的人开始认识到农业生态系统的作物地上和地下部是一个整体，土壤管理会影响土生态过程及生态系统服务。虽然已经认识到土壤土壤生物多样性的功能重要性，但是迄今仍缺乏对农田土壤生物群落和功能调控机制的认识。这一现状限制了土壤生物多样性的有效管理和高效利用。本项目以红壤地区有机物施用及免耕措施的野外调控实验为对象，基于土壤生境（有机物质量和物理结构）调控后土壤食物网及生态功能的连续监测，阐明土壤食物网结构和功能变化的时序格局；揭示土壤生物群落和功能的影响机制。结果表明：(1)有机物质量（秸秆、厩肥）和免耕影响土壤pH、EC、土壤容重、最大持水量、速效养分、土壤微生物生物量、土壤线虫群落数量和结构有显著影响；但是也受到年度的显著影响，尤其是夏秋气候条件的显著影响。伴随管理年限的增加，尚未呈现明显的时间趋势，可能因为试验的持续时间仍属于短期阶段。(2) 秸秆、厩肥和免耕对真土居弹尾虫影响不大。在功能性状方面，免耕有助于弹尾虫发展视觉能力和防紫外线的性状，而稻草覆盖有利于弹尾虫发展数量少的研究、个体小、颜色发白及中度发育个体；连续的农业措施也有利于发展半土居个体，而排斥真土居个体。(3)与预期相反，室内连续加热干扰研究没有发现有机肥影响土壤的功能稳定性比其他处理高。但野外调查表明有机肥处理的功能多样性和功能稳定性最高。(4) 基于生态化学计量学探讨了土壤团聚体上碳氮磷与土壤生物、功能的关系，发现植物茎叶和根系的养分比也与土壤、微生物和酶活性的元素比有显著联系。结构方程模型进一步证实了化肥和有机肥通过土壤理化性质及根系途径对微生物群落组成和酶活性的影响。(5)多元回归分析表明，细菌的存活与土壤资源有效性显著正相关，而与土著微生物性质显著负相关；土壤生物群落的组成和发展受到外部和其自身遗传特性的控制。干扰对于那些自身资源利用能力较弱的菌株所起的促进作用更大。总之，针对土壤资源有效性和物理结构改善的保护性措施能够促进土壤生物群落的发展。