南京林业大学最新TOP成果揭示混交林间伐后土壤有机碳储存的韧性机制
微生物群落对土壤有机质分解至关重要，并调控土壤碳动态。然而，间伐恢复过程通过何种微生物机制调控土壤有机碳储存仍不明确。为阐明间伐如何通过微生物过程影响土壤有机碳储存，本研究运用Illumina测序技术和生态酶化学计量法，分析了间伐时间序列（CK：未间伐，T2018：约4年前间伐，T2010：约12年前间伐）下的微生物群落、土壤酶活性、微生物元素限制及微生物碳利用效率。间伐显著改变了关键真菌群落组成：子囊菌门相对丰度在间伐后下降，T2010中显著低于CK；而担子菌门相对丰度在T2018中降低，在T2010中升高并显著高于T2018。微生物代谢在间伐后从磷限制转变为碳-磷联合限制，其中T2018阶段碳限制加剧，T2010阶段得到缓解，且即使土壤有机碳储量恢复至间伐前水平，碳限制仍然持续存在。T2018的土壤有机碳储量较CK降低44.81%，但在T2010恢复至与CK相当水平（较T2018增长43.27%）。研究发现，间伐后土壤有机碳储量变化由微生物碳利用效率与关键真菌类群相对丰度的改变共同驱动：微生物碳利用效率受土壤含水量和微生物元素限制调控，而关键真菌类群相对丰度主要受土壤含水量调节。本研究揭示了间伐后土壤有机碳储量恢复的驱动机制，为通过森林管理提升土壤碳固存能力提供了科学依据。
Fig. 5. Relationships between SOC stocks and four types of predictive factors (soil properties, microbial community diversity and composition, soil EEAs and microbial element limitations, and microbial CUE). Hierarchical partitioning analysis illustrates the relative importance of representative variables for each type of predictive factor in regulating SOC stocks (a). Spearman correlations show the relationships between SOC stocks and the relative abundances of fungal phyla among keystone taxa (b). Relationships between SOC stocks and significant factors (c–e). The linear regression lines with 95 % confidence intervals represent predicted effects of fixed factors. Significance levels: ∗P < 0.05, ∗∗P < 0.01, and ∗∗∗P < 0.001.
Fig. 6. Structural equation model analysis reflecting the impact of the thinning chronosequence on SWC, microbial community diversity and composition, keystone fungal abundance, soil EEAs, microbial element limitations, microbial CUE, and SOC stocks in mixed oak-pine forests. Microbial community diversity and composition included B-Chao, F-Shannon and F-NMDS1; keystone fungal abundance refers to the relative abundance of Basidiomycota; microbial element limitations included vector length and BG/(NAG + LAP); and soil EEAs included LAP and ACP. CK: no thinning; T2018: thinned ∼4 years prior; T2010: thinned ∼12 years prior. Black and red arrows indicate positive and negative pathways, respectively, whereas gray arrows indicate non-significant paths (P > 0.05). Blue arrows represent the direct effects of thinning treatments. Different lowercase letters (a, b) denote significant differences among treatments based on Tukey’s HSD post-hoc tests (P < 0.05). The symbols ∗, ∗∗ and ∗∗∗ indicate significance at P < 0.05, P < 0.01 and P < 0.001, respectively.
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