The decomposition of deadwood is a crucial process for the accumulation and sequestration of soil organic carbon (SOC) in forest ecosystems. However, the response of SOC to different decay classes of deadwood and the underlying mechanisms remain poorly understood. Here, we investigated the dynamics of SOC, soil properties, extracellular enzyme activities, and phospholipid fatty acid biomarkers across five decay classes (ranging from 1 to 5) of Masson pine (Pinus massoniana Lamb.) downed deadwood in a subtropical–temperate ecotone forest in Central China. Our results revealed a nonlinear response pattern of SOC along the deadwood decomposition gradient, with the maximum value at the decay class 4. Soil available nitrogen content, bacterial biomass, fungal biomass, the ratio of fungal-to-bacterial biomass, cellulase, activity and ligninase activity all increased with the intensification of deadwood decay, while soil pH decreased. The increase in SOC content was associated with a direct positive effect of bacteria and both direct and indirect positive effects of fungi by cellulose activity, but ligninase activity showed no significant relationship with SOC content. These findings suggest that cellulose and microbial biomass are key determinants of soil C formation and sequestration during deadwood decomposition. This study highlights the importance of the nonlinear response of SOC to deadwood decay, providing valuable insights for predicting future carbon-climate feedbacks.

Understanding the driving mechanisms of forest changes is of great significance for developing effective adaptation strategies to mitigate the impacts of climate change and human activities on ecosystems. This study used Theil–Sen median trend analysis, Mann–Kendall test, contribution rate decomposition, partial least squares, geodetector and residual analysis to explore the impact of climate change and human activities on the forest coverage area and NDVI of the Altai Mountains. Results show that changes in forest cover are driven by both forest management policies and climate change. Among them, forest management policy is the main factor. However, there are differences in the driving mechanisms in different altitude zones: in the alpine and subalpine zones, the promoting effects of natural death and climate change bring the forest coverage area toward a dynamic balance, while under the combined effects of human activities and climate change, the forest coverage area in the low mountain zones shows an expansion trend. For forest NDVI, the analysis results of the six scenarios show that the joint action of climate change and human activities promotes the growth of forest NDVI in the largest proportion (50.20%); the impact of climate change on forest NDVI is greater than that of human activities, and most of it is a promotion effect (30.28%). Forest degradation is mainly caused by human activities (19.39%), especially in the edge areas of the forest. Among climate factors, precipitation and snowmelt water are the main controlling factors for forest growth. Snowmelt water from March to April is an important water source before the growing season. This study provides the important scientific basis for forest management and strategic planning in the Altai Mountains.

Phenological models are valuable tools for predicting vegetation phenology and investigating the relationships between vegetation dynamics and climate. However, compared to temperate and boreal ecosystems, phenological modeling in alpine regions has received limited attention. In this study, we developed a semi-mechanistic phenological model, the Alpine Growing Season Index (AGSI), which incorporates the differential impacts of daily maximum and minimum air temperatures, as well as the constraints of precipitation and photoperiod, to predict foliar phenology in alpine grasslands on the Qinghai–Tibetan Plateau (QTP). The AGSI model is driven by daily minimum temperature (T_min), daily maximum temperature (T_max), precipitation averaged over the previous month (PA), and daily photoperiod (Photo). Based on the AGSI model, we further assessed the impacts of T_min, T_max, PA, and Photo on modeling accuracy, and identified the predominant climatic controls over foliar phenology across the entire QTP. Results showed that the AGSI model had higher accuracy than other GSI models. The total root mean square error (RMSE) of predicted leaf onset and offset dates, when evaluated using ground observations, was 12.9 ± 5.7 days, representing a reduction of 10.9%–54.1% compared to other models. The inclusion of T_max and PA in the AGSI model improved the total modeling accuracy of leaf onset and offset dates by 20.2%. Overall, PA and T_min showed more critical and extensive constraints on foliar phenology in alpine grasslands. The limiting effect of T_max was also considerable, particularly during July–November. This study provides a simple and effective tool for predicting foliar phenology in alpine grasslands and evaluating the climatic effects on vegetation phenological development in alpine regions.

This study used a method based on a spatial series in place of a temporal series, selecting Tamarix ramosissima shrubs at different developmental stages of coppice dunes as research subjects to investigate their chlorophyll fluorescence characteristics and non-structural carbohydrates (NSC). The results indicated that: (1) As coppice dunes developed, T. ramosissima showed a significant increase in photosynthetic pigment content alongside a decrease in actual photochemical efficiency (Y_(II)). Simultaneously, the reduction state of the plastoquinone (PQ) pool intensified, the apparent electron transport rate (ETR) increased, and the quantum yield of regulated energy dissipation significantly increased. These adaptations enabled T. ramosissima to dissipate excess light energy by enhancing its non-photochemical energy dissipation mechanisms. (2) Photosynthetically active radiation (PAR) and T. ramosissima leaf temperature (T_L) gradually increased during coppice dune development, whereas soil water content decreased, leading to increased stress on T. ramosissima and a subsequent decline in NSC content. This increased stress placed T. ramosissima at risk of ‘carbon starvation’, resulting in a gradual reduction in photosynthesis, biomass accumulation, and ultimately, mortality. (3) Correlations among various indicators of T. ramosissima were significant, with the highest degree of association and marked enhancement of synergistic effects in the growth and stable stages of coppice dunes. Comprehensive analysis revealed that high soil moisture content can alleviate water stress, improve light energy use efficiency and enhance the photosynthetic carbon assimilation process in T. ramosissima during coppice dune development.

Leaf construction cost (LCC), a proxy for the energetic investment plants make to construct leaf biomass, indicates carbon investment strategies of plants across diverse habitats. However, large-scale variations in LCC and their correlations with climate and soil factors have yet to be fully explored. Here, we compiled a dataset comprising 442 species-site combinations, spanning nearly all vegetation types in China, to address this knowledge gap. We found that LCC exhibited substantial variation, ranging from 0.72 g glucose g^-1 to 1.93 g glucose g^-1, with an average of 1.25 g glucose g^-1. LCC was significantly higher in woody species compared to non-woody species; however, there was no significant difference in LCC between evergreen and deciduous plants. LCC decreased with latitude and longitude but increased with altitude. Among bivariate LCC-environment relationships, LCC was positively correlated with mean annual precipitation and temperature, but negatively correlated with temperature seasonality, precipitation seasonality, soil nitrogen content, and soil silt content. Collectively, climate and soil factors account for over 54% of the variance in LCC, with soil exerting a more significant influence than climate on LCC. This study offers an exhaustive analysis of the evident pattern of LCC over a large spatial scale, fostering a fresh perspective on functional biogeography and establishing the foundation for further research exploring the interplay between LCC, ecological functions, and macroevolutionary implications.

Alpine meadows in Sanjiangyuan (SJY) National Park are experiencing degradation, and soil microbes play a critical role in maintaining the health and stability of these ecosystems. Soil microbes showed strong habitat specificity during meadow degradation, but we poorly understood the ecological assembly processes in soil microbial communities. This study explores the changes in ecological components across original and degraded patches of alpine meadows in SJY National Park. We examined vegetation-soil characteristics through field surveys, and soil microbial community structure by using high-throughput sequencing techniques. At the macro level, alpine meadows degradation increased vegetation species diversity, significantly reduced above-ground productivity, and made the soil more barren and alkaline. At the micro level, although the dominant phyla of soil microorganisms were similar in different degradation states of alpine meadows, degradation significantly increased the relative abundance of oligotrophic bacteria and decreased the relative abundance of dominant fungi. Additionally, microbial communities exhibited significant β-diversity. Degradation also led to an increase in microbial α-diversity, heightened microbial taxa competition, and a more complex microbial co-occurrence network. However, vegetation-soil variables explained only a small portion of the variation in soil microbes. Through the study of microbial ecological assembly processes, it was found that degradation enhanced the stochastic processes of soil microbial communities, and the changes in soil microbial communities were mainly driven by the variations inherent in the microbes themselves. These findings highlight the complex ecological interactions between above- and below-ground components, and emphasize the critical role of microbial community dynamics in ecosystem functions.

The invasion of Spartina alterniflora (SA) has led to significant hydrogen sulfide (H₂S) production in coastal wetlands. The phytotoxic S^2- plays a critical role in elemental biogeochemistry and may contribute to the successful invasion of SA in areas contaminated with heavy metals. To explore how H₂S influences nutrient uptake and energy utilization in SA and the native Phragmites australis (PA) under cadmium (Cd) stress, and to uncover the mechanisms by which H₂S facilitates SA invasion, a hydroponic experiment was conducted. This experiment included three Cd concentrations (0, 1, and 2 mg Cd L^-1) and three H₂S treatments (inhibiting H₂S synthesis, simulating an external H₂S source, and an untreated control). Results revealed that H₂S plays a crucial role in balancing the uptake of Mg, Mn, Ca, and Zn in SA, mitigating Cd-induced damage to the photosynthetic system, and enhancing nutrient and energy accumulation under Cd stress. In contrast, H₂S was toxic to PA, increasing lipid peroxidation, inhibiting growth, and disrupting mineral uptake, particularly of Ca. This exacerbated the detrimental effects of Cd on the photosynthetic system and nutrient accumulation in PA. In summary, irrespective of Cd treatment, H₂S enhanced energy accumulation, mineral uptake, and growth in SA compared to PA. It potentially supported the ecological niche competition within the coastal wetlands during the invasion of SA into PA habitats. Consequently, inhibiting endogenous H₂S synthesis in SA may offer a potential strategy for controlling its invasion.

Floodplain wetlands have a significant capacity for carbon sequestration but are vulnerable to land use changes. Poplars are extensively planted in wetlands due to the increasing demand for wood products and bioenergy. Although the large biomass of poplar may increase the carbon stock in wetlands, a high transpiration rate may reduce soil moisture, thereby improving the aeration of wetland soils and facilitating the oxidation of organic materials. Therefore, the impact of poplars on wetland carbon stocks is undetermined and remains unexplored. Here, we investigated the effects of poplar plantations on biomass carbon stocks (BCS) and soil organic carbon (SOC) stocks in Dongting Lake wetlands, China, using native Miscanthus lutarioriparius vegetation as a control. Our results indicated that the BCS of middle-aged and near-mature poplar plantations (36.47–81.34 t ha⁻¹) was higher than that of M. lutarioriparius (8.31 t ha⁻¹), and it increased with stand age. The SOC stocks within the 0–60 cm depth in young, middle-aged, and near-mature poplar plantations (130.32–152.58 t ha⁻¹) were higher than those in M. lutarioriparius (70.48 t ha⁻¹), but it did not increase with stand age. The BCS was positively associated with soil bulk density, and the SOC stocks were negatively associated with soil sand content. Overall, our findings indicate that poplar plantations increase carbon stocks in the Dongting Lake wetlands. Nevertheless, the long-term effect of poplar plantation on carbon sequestration in floodplain wetlands should be further investigated.

Plant root-associated fungal communities are pivotal for enhancing plant growth, nutrient absorption, disease resistance, and environmental stress adaptation. Despite their importance, the assembly processes of these communities remain inadequately explored. In this study, we utilized high-throughput sequencing, co-occurrence network analysis, and null models to perform an extensive examination of the diversity, composition, interaction patterns, and assembly mechanisms of the root-associated fungal communities of Mussaenda pubescens, a drought tolerant shrub that can thrive in stressful environments and which is widely used for Chinese medicine. Our findings revealed pronounced regional and ecological niche-based variations in the diversity and assembly of total fungi and essential functional guilds, including saprotrophs, symbiotrophs, and plant pathogens. Significantly, the fungal diversity of plant pathogens decreased with elevation, whereas total fungi, saprotrophs, and symbiotrophs were minimally affected. Stochastic processes, such as dispersal limitation, play a significant role in fungal assembly. Furthermore, soil physicochemical properties, climatic conditions, and spatial variables also emerged as critical determinants of fungal community structure. This study enriches our understanding of the dynamics governing root-associated fungal community assemblies and underscores the factors essential for sustaining fungal diversity.

Fruit type influences seed dispersal mode and its effectiveness, reflecting plant adaptability to their environments. However, the large-scale patterns of fruit type distribution in forest communities and differences in the drivers of various fruit types remain unclear. We present a large-scale biogeographic model of woody plant fruit types along a latitudinal gradient through the data analysis of 30 forest dynamic plots. Results showed the following. (1) Fleshy and dry fruits exhibited distinct distribution patterns in large-scale space. The distribution of fleshy fruits was greater in tropical and subtropical zones, while dry fruits were more common in temperate zones. (2) Climatic factors primarily drove the geographical distribution of the fruit types of woody plants. Climatic and spatial factors exerted greater effects on the species richness of dry fruits compared with that of fleshy fruits. Our results demonstrated the difference in the latitudinal gradient patterns of fleshy and dry fruits and identified the major abiotic environmental factors that drove their distribution in large-scale spaces, demonstrating the biogeography of the fruit types of woody plants.