Microbial traits affect soil organic carbon stability in degraded Moso bamboo forests

The degradation of Moso bamboo (Phyllostachys edulis) forests was reported to dominate soil organic carbon (SOC) accumulation via primarily increased litterfall and root secretions. However, to what extent degradation affects SOC fractions and the mechanisms underlying different degraded durations for SOC stability remain uncertain.

The vegetation spatial structure, basic soil physiochemical properties, SOC and its components, and microbial traits in four degradation categories of Moso bamboo forests were analyzed. Multiple statistical analyses were further conducted to explore the underlying mechanisms controlling the changing SOC pool size and stability under degradation.

Significantly higher SOC pools (5.40% to 33.62%) and POC/SOC ratios (11.26% to 30.68%), lower MAOC/SOC ratios (5.93% to 18.28%), and thus SOC stability, were reduced by degradation. Degraded Moso bamboo forests had higher age mingling (18.17%), more aggregated distribution (35.76%), and more intense competition (48.87%). This impacted increases in C inputs into soil from aboveground plants and, therefore, increased SOC and POC contents in the topsoil. Moreover, degradation reduced bacterial diversity and shifted the community from K- to r-strategists; fungal diversity remained unaffected, and saprotrophic fungi (r-) dominated the fungal community composition in soil. Consequently, microorganisms were highly involved in the shift from MAOC to POC, with implications for bacterial community diversity, life-history strategy, and increasing saprotrophic fungi. These alterations led to increased SOC storage but decreased its stability.

Overall, degradation-induced changes in plants, microbial communities, SOC fractions, and SOC stability are key processes for understanding plant-soil interactions under global change.