Arbor-shrub mixed vegetation restoration strategies cause greater increases in plant-derived carbon than microbial-derived carbon in limestone hills

Both mixed and monoculture strategies significantly influence the sequestration of soil organic carbon (SOC) in limestone hills and are crucial for mitigating climate warming. However, the mechanisms underlying the differential responses of plant- and microbial-derived SOC in these forests remain poorly understood. In this study, lignin phenols and amino sugars were measured to explore the differences in plant- and microbial-derived carbon between arbor-shrub mixed forests and monoculture forests established on a limestone hill in 2012. The results indicated that mixed forests of Acer pictum × Ligustrum quihoui and Pistacia chinensis × Pyracantha fortuneana increases plant-derived carbon contents by 73.46 % and 40.41 %, respectively, with corresponding contributions to SOC rising by 10.18 % and 4.98 %, compared to their respective monoculture forests (Acer pictum and Pistacia chinensis). In contrast, microbial-derived carbon increased by 7.65 % and 22.22 %, while their contributions to SOC decreased by 9.39 % and 1.05 %, respectively. Notably, plant-derived carbon exhibited higher increases than microbial-derived carbon, underscoring its more prominent influence on soil carbon sequestration. Arbor-shrub mixed strategies enhanced both plant- and microbial-derived carbon content by affecting the soil bulk density, total nitrogen and phosphorus content, fine root biomass, fungal diversity, and β-glucosidase and sucrase enzyme activities, thereby contributing to an increase in SOC levels. Given the profound influence of plant- and microbial-derived carbon on carbon sequestration, these findings underscore the critical importance of prioritizing arbor-shrub mixed vegetation afforestation strategies for limestone hills.