植被类型变化对土壤微生物碳利用效率的影响研究进展

植被类型变化强烈影响着土壤碳循环。土壤微生物碳利用效率（CUE）是微生物将从环境中获取的碳分配给自身生长的比例，是土壤碳循环的综合指标。研究植被类型变化对CUE的影响有助于从微生物视角理解该过程中的土壤碳动态，可以为评估植被类型变化对土壤质量及生态系统碳循环的影响提供基础，具有重要的理论及实际价值。通过系统查阅相关文献，综述了植被类型变化导致的CUE变化情况，以及该过程中影响CUE的因子与机制。目前，相关研究主要涉及以林地、草地和农业用地为起点或终点的植被变化类型。天然林（原生林、次生林）变化为人工林、林地变化为草地后CUE普遍下降，随终点植被的发展CUE可能恢复至起点水平。植被成熟度越高，发生转变时CUE变化越剧烈。植被类型变化以农业用地为起点或终点时，CUE变化方向的不确定性及幅度的变异性均增加。植被类型变化导致的CUE变化主要受到植被、土壤、微生物因子及其交互作用的驱动，指示CUE的指标、采样季节和土层也会一定程度上影响CUE的变化。今后相关研究应采用直接的CUE测定方法，拓宽研究气候区及植被变化类型，关注植被变化过程中CUE变化的土层差异及动态监测，深入对植被类型变化导致的生态环境因子变化与CUE的关系及作用机制的研究。

Effect of vegetation type change on soil microbial carbon use efficiency: A review

Soil microbial carbon use efficiency (CUE) represents the proportion of microbes allocate carbon taken from the environment to their own growth. It is a synthesized index of ecosystem C cycling, because of the crucial role that microbes play in the decomposition and stabilization of soil organic C. Changes in vegetation types stronly influence soil physical and chemical properties and the composition of soil microbial community, and hence microbial CUE. Studying the effect of vegetation type conversion on microbial CUE could act as a lens through which to resolve the link between vegetation and ecosystem C cycling, and could provide the foundation for assessing the changes in soil quality caused by vegetation type shift. Therefore, it is of great theoretical and practical value to study the effect of vegetation type conversion on microbial CUE. Based on the systematic review of related literature, we summarized the changes in soil microbial CUE as a result of vegetation type conversion, as well as affecting factors and underlying mechanisms. At present, Most empirical studies concerning the changes in microbial CUE due to vegetation conversion mainly involves the following 5 types:primary forest to secondary forest, natural forest (primary forest and secondary forest) to plantaion, woodland to grassland, the conversion between woodland and agricultural land, and the degradation or restoration of grassland. Soil microbial CUE generally declines during the conversion from natural forests, including primary and secondary forests, to plantation, and from woodland to grassland, despite the microbial CUE would recover slowly to its original level as the vegetation develops after the conversions. The more mature the vegetation was, the more drastic the change of CUE would be when it changed. In addition, there are uncertainties in change directions and large variations when farmland abandonment and agricultural expansion are involved in conversion. The changes of CUE due to vegetation type conversion mainly driven by vegetation, edaphic and microbial factors and their interactions. However, many ambiguities still remain in the impact mechanism of vegetation type conversion on microbial CUE, such as the impact of plant diversity, litter quality and root, and many edaphic properties, e.g. soil temperature and pH. What''s more, the research on how microbial community drives CUE change is very weak. Besides, different methods, e.g. CUE indices, sampling seasons and soil layers, used in studies affect the evaluation of CUE changes. Future related sudies are needed to better understand the change dynamics of microbial CUE in different soil layers after vegetation conversion in a wide range of vegetation types and climatic zones by using the direct CUE determing methods, and particularly the mechanisms underlying the CUE dynamics.