Supplementary file 1_Strip thinning and filling reduces litter humus carbon loss in Cupressus funebris plantations: relative contributions of microclimate, litter substrate and microbial biomass.docx

Shrub litter exhibited markedly greater HUc and HD than arbor, herb, and mixed litter (p < 0.05). Hierarchical partitioning (HP) revealed litter substrate as the dominant factor for humification variation, accounting for 64.59 %, 71.15 %, 42.69 %, and 46.60 % of explained variance in UMP, AFG, STF, and ETD, respectively; climatic variables also exerted notable regulatory effects, particularly within STF stands. Further partial least squares path modeling (PLS‑PM) demonstrated that climatic conditions exerted strong, statistically significant direct negative effects on litter humification in all stands, even though its relative explained variance from HP was moderate.

Among managed stands, STF yielded a negative point-estimate for the direct microbial-to-humification path (β = -0.422, bootstrap 95% CI -0.485 to 0.444, includes zero). By contrast, the unmanaged UMP stand had a significant positive microbial direct effect on litter humification. Significant negative direct litter‑substrate effects on humification were observed in UMP, AFG and ETD, whereas this substrate path was non-significant in STF.</p>Discussion<p>Overall, STF effectively mitigated litter humus carbon loss, and its humus-preserving capacity could be further enhanced by promoting understory shrub recruitment.

This study provides empirical evidence for optimizing management practices to conserve litter humus in low-yield subtropical cypress plantations, and replicated multi-stand experiments are needed for broader generalization.</p>