Linking functional microbial groups to soil carbon cycle multifunctionality in degraded karst forests

The collected research data include indicators of soil microbial communities involved in the C cycle, environmental indicators and SCCM index. The microbial indicators consist of species diversity, relative abundance, functional strength, and functional diversity, considering overall, rare, common, and abundant taxa separately. Based on our research hypotheses: i) soil C cycle multifunctionality will increase during the restoration process; ii) the shifts in microbial communities involved in soil C cycling will differ among abundant, common, and rare taxa across the restoration stages; and iii) the contributions of these microbial taxa to soil C cycle multifunctionality will also differ throughout the restoration chronosequence. We conducted a space-for-time sequential study across multiple restoration stages. For each stage, ten fixed plots were randomly set up, with dimensions of SB (shrubland) in both SG (secondary-growth forest) and OG (old-growth forest) systems. The results showed that the SCCM index increased significantly throughout restoration, with microbial functional traits exerting more influence than microbial diversity. Within the microbial community, functional reorganization involves a shift in functional dominance from rare to non-rare (common and abundant) taxa, indicating improved functional stability. Specifically, common taxa were the primary drivers of the enhanced SCCM, with increases in their functional diversity and strength playing a pivotal role. The concurrent recovery of plant diversity and soil properties facilitated these microbial shifts. In summary, natural restoration promotes SCCM mainly by augmenting microbial functional performance, particularly that of common taxa, a subgroup whose role in supporting soil ecological functions has historically been underestimated.本研究采集的科研数据涵盖参与碳循环的土壤微生物群落指标、环境指标以及土壤碳循环多功能性（Soil C Cycle Multifunctionality，简称SCCM）指数。其中微生物指标包含物种多样性、相对丰度、功能强度与功能多样性，且分别针对整体类群、稀有类群、常见类群与优势类群展开分析。基于本研究提出的三项研究假设：其一，土壤碳循环多功能性在生态恢复进程中会逐步提升；其二，参与土壤碳循环的微生物群落在不同恢复阶段的演替模式，在优势、常见与稀有类群间存在显著差异；其三，上述微生物类群对土壤碳循环多功能性的贡献，也会随恢复时间序列发生变化。本研究采用以空间代时间的序列研究方法，覆盖多个恢复阶段。每个恢复阶段随机设置10个固定样地，样地在次生林（secondary-growth forest，简称SG）与原始林（old-growth forest，简称OG）系统中均为灌木地（shrubland，简称SB）类型。研究结果显示，SCCM指数在整个恢复进程中显著升高，且微生物功能性状的影响程度强于微生物多样性。在微生物群落内部，功能重组表现为功能主导地位从稀有类群转向非稀有类群（常见类群与优势类群），这表明群落功能稳定性得到增强。具体而言，常见类群是SCCM提升的核心驱动因子，其功能多样性与功能强度的增加发挥了关键作用。植物多样性与土壤性质的协同恢复，推动了上述微生物群落的演替过程。综上，自然恢复主要通过提升微生物的功能表现（尤其是常见类群的功能表现）来促进SCCM提升，而常见类群在支撑土壤生态功能中的作用此前长期被低估。