Plant detritus plays a crucial role in regulating belowground biogeochemical processes in forest ecosystems, particularly influencing labile carbon (C) dynamics and overall soil C storage. However, the specific mechanisms by which litter and roots affect soil organic carbon (SOC) and its components in plantations remain insufficiently understood. To investigate this, we conducted a detritus input and removal treatment (DIRT) experiment in a Larix principis-rupprechtii Mayr plantation in the Taiyue Mountains, China, in July 2014. The experiment comprised three treatments: root and litter retention (CK), litter removal (LR), and root and litter removal (RLR). Soil samples were collected from depths of 0–10 cm and 10–20 cm during June, August, and October 2015 to evaluate changes in soil pH, water content (SW), SOC, dissolved organic carbon (DOC), readily oxidizable organic carbon (ROC), and microbial biomass carbon (MBC). The removal of litter and roots significantly increased soil pH (p < 0.05), with pH values being 8.84% and 8.55% higher in the LR and RLR treatments, respectively, compared to CK treatment. SOC levels were significantly reduced by 26.10% and 12.47% in the LR and RLR treatments, respectively (p < 0.05). Similarly, DOC and MBC concentrations decreased following litter and root removal, with DOC content in August being 2.5 times lower than in June. Across all treatments and sampling seasons, SOC content was consistently higher in the 0–10 cm depth, exhibiting increases of 35.15% to 39.44% compared to the 10–20 cm depth (p < 0.001). Significant negative correlations were observed between SOC and the ratios of ROC/SOC, pH, DOC/SOC, and MBC/SOC (R = −0.54 to −0.37; p < 0.05). Path analysis indicated that soil pH had a significant direct negative effect on SOC (p < 0.05), with a standardized path coefficient (β) of −0.36, while ROC had a significant direct positive effect on SOC (β = 0.66, p < 0.05). Additionally, pH indirectly affected SOC by significantly influencing ROC (β = −0.69), thereby impacting SOC indirectly. Random forest analysis also confirmed that the ROC/SOC ratio plays a critical role in SOC regulation. This study reveals the complex interactions between litter and root removal and soil C dynamics in larch plantations, identifying soil pH and ROC as crucial regulator of SOC content. However, the short-term duration and focus on shallow soil depths limit our understanding of long-term impacts and deeper soil C storage. Future research should explore these aspects and consider varying climate conditions to enhance the applicability of our findings. These insights provide a scientific foundation for developing effective forest management strategies and forecasting changes in soil C storage in the context of climate change.

Habitat degradation and fragmentation driven by climate change and human activities are major threats to wildlife, particularly in the ecologically sensitive Sanjiangyuan region on the Qinghai–Tibet Plateau. Alpine musk deer (Moschus chrysogaster) and blue sheep (Pseudois nayaur), two key ungulate species, face severe habitat challenges due to these environmental pressures. Understanding their habitat requirements and distribution patterns is critical for developing effective conservation strategies. This study applied the Maximum Entropy (MaxEnt) model to predict the habitat suitability of alpine musk deer and blue sheep in the characteristic canyons of the Sanjiangyuan region. Data from 55 infrared camera traps and 26 environmental variables, including climate, topography, land use, and human disturbance, were analyzed. The results indicated that annual mean temperature, altitude, temperature annual range, and distance to water were the most influential factors for both species. The suitable habitats for alpine musk deer and blue sheep were limited, covering only 9.61% and 10.84% of the study area, respectively. These areas were primarily distributed along the main stream of the Yellow River and its primary tributary canyons. The limited availability of high-quality habitats underscores the vulnerability of these species to ongoing habitat degradation and fragmentation. To effectively protect ungulate populations, we suggest continuously monitoring the trends of critical habitats, strengthening the protection of existing habitats, and improving the current conservation systems. The findings provide critical insights for conservation planning and management in the Sanjiangyuan region.