Divergent soil organic carbon accrual from plant and microbial sources across ecosystem types in a hyper-arid oasis-desert ecotone

Soil organic carbon (SOC) dynamics in hyper-arid ecosystems are governed by allocation shifts between plant- and microbial-derived carbon (C). However, the underlying mechanisms governing these dynamics under land-use change remain poorly quantified. To address this, lignin phenols, amino sugar biomarkers, and microbial functional trait analysis were integrated to evaluate how microbial life-history strategies and environmental stressors regulate SOC accumulation across three ecosystem types (natural wetlands, paddies, and desert-steppes) in oasis-desert ecotones of the Taklamakan Desert. Natural wetlands exhibited the highest SOC (4.15 g kg −1 ) content, with 19.9 % derived from microbial necromass—primarily fungal component—due to alleviated nitrogen limitation [higher nitrogen/phosphorus (N/P) ratio: 0.928] and dominance of microbial growth-yield (Y) strategies. In contrast, paddies (SOC content: 2.57 g kg −1 ) exhibited the highest plant-derived C contribution (28.7 % of SOC), where plant-derived C was negatively correlated with SOC content, likely driven by C limitation and priming effects under reduced microbial Y-strategist abundance. Desert-steppes (SOC content: 3.44 g kg −1 ) showed minimal microbial necromass accumulation (6.1 % of SOC) and advanced lignin oxidation (elevated syringyl/vanillyl and cinnamyl/vanillyl), reflecting drought-induced depletion of Y-strategists and incomplete decomposition. Soil salinity was observed to suppress microbial necromass input, while N-P stoichiometry and available N facilitated its accrual. Collectively, our findings indicate a stability dichotomy: wetlands sustain persistent SOC through microbial necromass enrichment, whereas agricultural conversion shifts SOC toward plant-derived C prone to destabilization. Strategies for SOC conservation in hyper-arid oasis-desert ecotones should prioritize the preservation of natural wetlands coupled with implementation of balanced N-P fertilization in anthropogenically managed ecosystems (e.g., paddies). This integrated approach enhances microbial contributions to SOC resilience under ongoing land-use changes. • Hyper-arid wetlands store more SOC dominated by fungal necromass. • Paddy SOC is less stable due to plant-derived C dominance. • Microbial N-limitation alleviation drives SOC accumulation via Y-strategy. • Soil salinity suppresses microbial necromass accumulation. • N/P ratio and available N are key drivers of microbial necromass accrual.