Forests

Different forest ecosystems affect the acquisition and loss of SOC by changing the niche differentiation of above-ground and under-ground, resulting in changes in the utilization efficiency of water and nutrient elements. The impact of different types of forests on carbon storage in forest soils has received significant attention in recent decades, as these ecosystems are critical for mitigating the effects of global climate change. There are significant differences in environmental factors among different types of forests, such as carbon source type, topographic characteristics, soil texture, microbial community status, climate and hydrological conditions. At present, the research on the effects of environmental factors such as climate, hydrological conditions or soil quality on SOC has been well carried out. Nevertheless, the distribution pattern of microbial carbon and particulate organic carbon in subtropical forest ecosystems and their contribution to SOC still need much of scientific research. Forest types have a significant impact on the content and distribution characteristics of MNC and particulate organic carbon fractions, but there is heterogeneity in different forests. Importantly, the random forest analysis showed that MNC and MAOC were the main factors affecting SOC compared with other variables, which indicated MNC and MAOC have higher relative importance to SOC (p < 0.05). Specifically, our research found that the total MNC and BNC content in natural forests and broad-leaved forests were significantly higher than that in coniferous forests (p < 0.05), while the FNC content and FNC/BNC in coniferous forests were significantly higher than that in the other two forests (p < 0.05). In addition, the MAOC content of natural forests was higher than others, which indicated the stability of natural forest is higher than other forests. However, CPOC, FPOC content, and POC/MAOC in coniferous forests were significantly higher than in broad-leaf forests and natural forests. Biotic and abiotic factors profoundly affect the dynamic changes in SOC accumulation and stability. Different environmental factors lead to more MNC and MAOC in forest types with faster decomposition rates. These findings have instructive implications for understanding the contributions of different forest types on SOC stability and accumulation mechanisms in forest soils.

Foliar fertilization, an efficient agricultural production strategy, is relatively rare in bamboo cultivation and management. Phosphorus assumes an indispensable role in controlling plant sugar metabolism and antioxidant defense. Whether foliar application of triple superphosphate (TSP) can enhance carbohydrate metabolism in new bamboo leaves, improve the antioxidant defense system, and thereby promote the growth and development of new leaves remains to be investigated. In this study, we conducted foliar application of TSP on the new leaves of 1-year-old Neosinocalamus affinis culms to analyze the effects of exogenous phosphorus on leaf morphological, anatomical, and physiological characteristics. The results showed that 0.3% TSP was the optimal concentration. This treatment significantly increased leaf length (maximum growth rate of 24.3% on day 21) and mesophyll cell thickness. It also significantly increased total chlorophyll content (maximum increase rate of 71.10% on day 14). The 0.3% TSP treatment significantly enhanced the activities of critical enzymes involved in sucrose biosynthetic and catabolic processes and starch synthesis, inhibited starch degrading enzyme activity, and promoted the accumulation of soluble sugars, starch, and total non-structural carbohydrates. Furthermore, TSP treatment significantly increased the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), and significantly reduced the contents of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) (45.11% and 54.64% reduction on day 7, respectively), indicating effective alleviation of oxidative stress and enhanced leaf stress resistance. Generally, foliar application of 0.3% TSP synergistically optimized leaf structure, photosynthetic capacity, sugar metabolism, and antioxidant defense system, comprehensively promoting the development of new N. affinis leaves and enhancing their stress resistance.

Knowledge of soil organic carbon (SOC) dynamics underpins accurate estimation of carbon sequestration in fragile ecosystems. However, most studies focus on SOC content in bulk soil while neglecting its distribution within soil aggregate fractions and the associated stabilization mechanisms. In the Mu Us Sandy Land, five vegetation types of the same restoration age were selected: natural grassland (NG), mixed grass–shrubland (GS), pure shrubland (PS), pure woodland (PW), and mixed woodland (MW). SOC stocks in bulk soil and aggregate fractions were quantified, and their key influencing factors were identified. The results showed that vegetation type and soil depth significantly impacted SOC stocks and their distribution among aggregates. Pure woodland exhibited the highest SOC stocks, particularly in macroaggregates and microaggregates. Aggregate stability, nutrient availability, and extracellular enzyme activities jointly regulated SOC accumulation, but their relative importance varied across vegetation types. Aggregate stability and physical protection were the main drivers in GS, PS, and PW, while nutrient availability played a more significant role in MW and NG. In conclusion, these findings emphasize the crucial role of soil aggregate stability and physical protection of macroaggregates and microaggregates in enhancing soil carbon sequestration, providing important theoretical support for optimizing ecological restoration strategies.