Soil microbial metabolic limitations under subalpine coniferous and broad‐leaved forests responding to litter input and removal treatments

Abstract The quality and quantity of above‐ground litter and belowground root input into soil impact microbial nutrient requirements and status. However, the impact of short‐term litter and root input on soil microbial metabolic limitations under different forest ecosystems remains unresolved. Here, we conducted a litter manipulation experiment (control, CK; double litter, DL; no roots and double litter, NRDL; no litter, NL; no roots, NR; no roots and no litter, NRNL) in a coniferous forest ( Pinus yunnanensis ) and a broad‐leaved forest ( Quercus pannosa ) of Southwest China. We evaluated the patterns in microbial relative carbon (C) and phosphorus (P) limitations indicated by vector lengths and angles using relative proportional enzymatic activities and key controlling factors after 1 year of treatment. Within the experimental timeframe, litter addition did not significantly change microbial metabolic limitations under both forest soils. In contrast, root removal significantly alleviated microbial relative C limitation and enhanced relative P limitations compared with above‐ground litter removal, likely due to root removal promoting above‐ground plant growth by increasing photosynthetic C fixation, thereby compensating for the C loss of the root system. Our study revealed that coniferous forests exhibit a greater relative C limitation and a lower relative P limitation compared to broad‐leaved forests. Microbial metabolic limitations in coniferous forests are primarily governed by microbial attributes (e.g. microbial biomass P). However, these limitations are regulated by soil properties (e.g. dissolved organic C) in broad‐leaved forests. These findings reflect coniferous forests with higher litter C:N ratio harbour stable‐adapted, specialized microbiota that favours long‐term C storage, whereas broad‐leaved forests with lower litter C:N ratio exhibit stronger soil physicochemical feedbacks and possibly increase susceptibility to nutrient leaching. Collectively, our results reveal divergent above‐ and belowground detrital dynamics regulate soil C and P cycling across forest ecosystems and highlight the necessity of distinct management priorities for two forest types: coniferous forests require protection of underground symbiotic systems and broad‐leaved forests need effective litter management to alleviate P limitations, respectively. Read the free Plain Language Summary for this article on the Journal blog.