脆弱生境植被恢复过程植物–微生物–土壤碳氮磷化学计量协调机制

Mutual feedbacks and dynamic equilibrium of the carbon (C), nitrogen (N), phosphorus (P) in plant- soil system are key to the stable and sustainable restoration of fragile ecosystems. The project takes the plant-microbe-soil as research object, and the ecological stoichiometry and microbial metabolism theory are applied. The regression analysis, quantity sorting, high-throughput sequencing, and fluorescent enzyme labeling technique are also synthetically used to analysis the coordination pattern of C, N and P among plants, microorganisms and soil components during succession stage of different artificial vegetation types in fragile ecosystem of north Shaanxi province. Combining and analyzing with vegetation characteristics, soil factors, and hydrothermal conditions, this project aims to reveal the coupling equilibrium of C, N, and P in plant-soil system and its influencing key factors after afforestation of artificial vegetation. Furthermore, we further explore the responses of microbial C, N, P stoichiometry, community structure, ratio of extracellular enzymes, and microbial respiration to the evolution patterns and coordination relationships of C, N, P stoichiometry in plant-soil system and the mineralization of plant components. The findings aim to reveal the mechanisms of microbial coordination of C, N, P stoichiometry in plant-soil system, and show the regional nutrient limitations and criterion. While the mutual feedbacks and cycle characteristics of C, N, and P in plant-soil system are clarified, which will provides a scientific basis for stable recovery and sustainable development of fragile ecosystems.

植物–土壤系统碳氮磷养分互馈与协调平衡是脆弱生境稳定与可持续恢复的关键。本项目以植物–微生物–土壤整体作为研究对象，基于生态化学计量与微生物代谢的理论和方法，综合运用回归分析、数量排序、高通量测序、荧光酶标测定等技术，分析陕北黄土丘陵沟壑区典型人工植被不同恢复演替阶段，植物、微生物、土壤碳氮磷生态化学计量的演变格局与动态协调关系；解析与植物群落特征、土壤因子、水热条件的交互影响，阐明人工植被恢复过程植物-土壤系统碳氮磷元素的耦合平衡特征及其主控环境因素；同时，进一步探求微生物碳氮磷化学计量、群落结构、胞外酶比例和微生物熵对植物–土壤碳氮磷化学计量演变格局及植物组分矿化分解的响应和调控作用，以深入揭示植物–土壤碳氮磷化学计量协调的微生物作用机制，以提出区域植被恢复限制养分与判断依据，明确人工植被恢复过程碳氮磷互馈效应与协调机制，为指导区域脆弱生态系统稳定可持续恢复提供科学依据。

探索生态脆弱区植物–土壤系统碳氮磷养分互馈与协调平衡是脆弱生境稳定与可持续恢复的关键,对指导脆弱生态系统的可持续恢复具有重要的科学价值和实践意义。因此，本项目于黄土高原丘陵沟壑区选择不同恢复年限的刺槐、柠条、撂荒草地植被恢复模式为研究对象，基于生态化学计量学理论与微生物代谢理论，探究人工林草恢复过程植物-微生物-土壤整体碳氮磷化学计量演变格局与动态协调关系，并进一步分析微生物碳氮磷化学计量、群落结构、胞外酶比例以及微生物熵对植物–土壤碳氮磷化学计量演变格局及枯落叶矿化分解的响应和调控作用，以提出区域植被恢复限制养分，明确人工植被恢复过程碳氮磷互馈效应与协调机制。研究结果表明人工林地植被恢复过程碳氮磷含量因植被类型和恢复年限不同产生不平衡的增长，导致C:N:P化学计量比随碳氮磷含量累积的差异发生分异变化。但总体上，植物-微生物-土壤之间以N:P比变化关系最为敏感，并且由N:P比变化推断植被恢复后期刺槐可能出现磷限制，柠条和撂荒出现氮限制。人工林草地恢复微生物丰度和多样性均显著提升，带动微生物能量代谢指标MBC:SOC在柠条和撂荒草地随着恢复年限的延长呈现增加趋势，刺槐林在后期出现降低趋势，说明微生物群落通过调整自身的群落构成、化学计量比以及能量代谢响应植被-土壤系统的元素平衡关系。同时，植被特征和土壤物理性质通过影响微生物对养分的获取强烈地调节着胞外酶活性及其化学计量比，特别是以土壤水溶性碳氮和微生物氮磷影响最敏感。在枯落叶分解过程碳氮大量损失，降低了微生物生长代谢资源，微生物响应降低了菌群多样性，但枯落叶有机质输入土壤后为微生物群落带来更丰富的资源，促进更大的生态位分化以增强其多样性。综上，本研究反映出了退耕林植被恢复过程植物–微生物–土壤系统间元素的平衡协调关系及微生物响应机制，这可为区域脆弱生态系统的稳定恢复与可持续发展提供了科学依据。综上，本研究反映出了退耕林植被恢复过程植物–微生物–土壤系统间元素的平衡协调关系及微生物响应机制，这可为区域脆弱生态系统的稳定恢复与可持续发展提供了科学依据。