Jiming Cheng

Global climate change has intensified drought and increased nitrogen deposition, threatening forest tree seedling regeneration. To clarify how drought severity and nitrogen enrichment jointly affect seedling performance in Quercus wutaishanica, a dominant montane tree in northern China, we conducted a full two-factor pot experiment. We established three drought treatments (ambient precipitation [CK], chronic drought [CD], and intense drought [ID]), fully crossed with two nitrogen addition levels (0 and 10 g N m⁻² yr⁻¹), and measured functional traits related to growth, photosynthesis, and stress resistance. Our main results were threefold: (1) Both drought treatments significantly inhibited growth and biomass accumulation: total biomass decreased by 28% under CD and 38% under ID relative to CK, with suppression intensifying as drought severity increased. (2) Nitrogen addition increased total biomass by 12% under chronic drought, but this ameliorative effect fell to just 2% under intense drought. (3) As drought stress increased, the seedlings underwent a shift from stomatal to non-stomatal photosynthetic limitation, and from active physiological acclimation to irreversible metabolic damage. (4) Random forest modeling confirmed that biomass variation was primarily driven by traits related to water-use efficiency and resource acquisition. Overall, intensifying drought consistently constrains Q. wutaishanica seedling growth, and the beneficial effect of nitrogen addition declines sharply with increasing drought severity. These findings provide new empirical insights for predicting seedling regeneration and guiding sustainable forest nutrient management under ongoing climate change.

Long‐term anthropogenic disturbances have damaged forest ecosystems, and different restoration approaches after disturbance play a crucial regulatory role in maintaining and enhancing ecosystem functions. However, existing studies have mostly focused on the response characteristics of single ecosystem functions, while research on the impacts of different restoration methods on soil multifunctionality of forests and their driving mechanisms remains scarce. Taking the completely anthropogenically disturbed Quercus wutaishanica communities in northern deciduous broad‐leaved forests as the research object, this study systematically explored the comprehensive effects of two typical restoration approaches (natural restoration and artificial assisted restoration with Larix principis‐rupprechtii ) and soil layer depths (0–10 cm, 10–20 cm) on soil microbial biomass and soil multifunctionality after 40 years of restoration, and further revealed the dominant driving factors of soil multifunctionality. The results showed that: (1) Artificial assisted restoration markedly increased soil microbial phosphorus content by 97.52% ± 28.86%; with increasing soil depth, both soil microbial carbon and nitrogen contents decreased significantly, by 24.18% ± 6.14% and 7.89% ± 2.12%, respectively. (2) Artificial assisted restoration communities exhibited a significantly higher soil multifunctionality index (0.34) compared with natural restoration communities (−0.37). Further analysis indicated that soil multifunctionality was mainly driven by soil microbial nitrogen content and the Pielou evenness index of plant community composition. This study provides notable theoretical supports and practical references for the sustenance, renewal and management of damaged ecosystems in northern deciduous broad‐leaved forests.

Anthropogenic activities and environmental changes have exerted an increasingly high impact on the habitats of wild animals, especially endangered species. Researchers have paid attention to the effects of future climate change on wildlife habitats. However, the impact of climate change on the suitable habitats of Tragopan birds has rarely been reported. Here, we used the Maxent model to assess the influence of climate change on the geographical distribution of five Tragopan species. The results showed that the SSP585 scenario projected relatively favorable conditions, with the total area of suitable habitats expected to show an overall increasing trend over time. Centroid analysis revealed that the centroid gradually shifts toward lower latitudes and elevations due to climate warming. Environmental factor analysis showed that human-induced factors (particularly land use) are the main determinants affecting the habitat suitability of Tragopan birds. Notably, a comparison between dispersal velocity and biological velocity showed that despite the predicted gradual expansion of habitat area, Tragopan birds may be difficult to expand into the newly suitable habitat regions. We further emphasize that establishing ecological corridors and setting up new protected areas will have a more significant impact on conserving the Tragopan birds.

Environmental changes may affect animal hoarding behavior through changes to plant diversity. Food hoarding behavior in small mammals can affect the seed dispersal process and thus the regeneration of the plant population. However, little is known about how small mammals select seeds of different sizes under different forest types. Here, we tracked the fates of 3360 seeds in the field. We used a generalized linear mixed model to analyze the effects of small mammals on three fates (predation in situ, predation after dispersal, hoarding after dispersal) and two dispersal distances (predation distance after dispersal and hoarding distance after dispersal) of different seeds by size and forest type. The results showed that small mammals consume smaller seeds in situ and cache larger seeds after dispersal. The predation distance after dispersal and hoarding distance after dispersal of the large seeds were significantly higher than those of small seeds. Forest types with dense vegetation conditions exhibited lower hoarding rates after dispersal, while those with poor vegetation conditions had increased predation and hoarding distances after dispersal. Our results suggest that larger seeds are dispersed to further distances, potentially enhancing plant population regeneration. However, seeds are more often scatter-hoarded and dispersed over longer distances in forests with poor vegetation conditions, which may also benefit plant population regeneration. These results provide insights into how seed size and forest type influence seed predation and dispersal by small mammals.

Precipitation changes have significant impacts on biodiversity and ecosystem productivity. However, the effects of precipitation changes on species diversity have been the focus of most previous studies. Little is known about the contributions of different dimensions of biodiversity (species, functional, and phylogenetic diversity) in linking long-term precipitation changes to ecosystem functions. In this study, a randomized design was conducted in the desert steppes of Ningxia, which included three treatments: natural rainfall, precipitation reduced by 50%, and precipitation increased by 50%. After 4 years of treatment, the effects of precipitation changes on aboveground productivity and its underlying mechanisms were explored. The results showed that (1) reduced precipitation significantly decreased phylogenetic diversity and species diversity, but had no significant effect on functional diversity; (2) reduced precipitation significantly decreased aboveground productivity, while increased precipitation significantly enhanced aboveground productivity; and (3) changes in precipitation primarily regulated aboveground productivity by altering soil nitrogen availability and the size of dominant plant species. This study provides important theoretical and practical guidance for the protection and management of desert steppe vegetation under future climate change.

Nitrogen (N) and phosphorus (P) are vital nutrients in terrestrial ecosystems, essential for vegetation growth, plant survival, development, and the maintenance of plant diversity. While the effects of N and P additions on plant nutrient concentrations and diversity have been extensively studied, the impact of various stages of natural forest ecosystem restoration after disturbance, particularly on plant N, P nutrients, and diversity, is less understood. This study investigates the influence of anthropogenic disturbance on soil N: P ratios, plant community-level N: P, and species diversity in Liaodong oak forests in northern China during early (about 10 years), mid-to-late (about 30 years), and late (about 40 years) restoration stages (it is a space for time substitution method). We observed that soil total nitrogen to total phosphorus ratio (TN: TP) and soil available nitrogen to phosphorus ratio (AN: AP) were significantly lower in the mid-to-late and late stages of restoration compared to the early restoration stages. Concurrently, plant community level leaf nitrogen-phosphorus ratio (CWM_{N: P}) were notably lower in these later stages. Additionally, species richness showed a decline as restoration time increased. These findings highlight that decreasing soil N: P ratio over time exacerbates plant N limitation and reduces plant richness, emphasizing the critical role of soil nutrient dynamics in forest restoration post-disturbance. Our results provide important insights for forest management and restoration practices, contributing to a better understanding of ecosystem restoration processes.

Mountain apricot (Prunus sibirica) is an important fruit tree variety, and has a wide range of planting and application value in China and even the world. However, the current research on the suitable distribution area of P. sibirica is still inconclusive. In this study, we retrieved distribution data for P. sibirica in China from the Global Biodiversity Information Facility (GBIF), and identified six key environmental factors influencing its distribution through cluster analysis. Using these six selected climate factors and P. sibirica distribution points in China, we applied the maximum entropy model (MaxEnt) to evaluate 1160 candidate models for parameter optimization. The final results predict the potential distribution of P. sibirica under the current climate as well as two future climate scenarios (SSPs126 and SSPs585). This study shows that the model optimized with six key climate factors (AUC = 0.897, TSS = 0.658) outperforms the full model using nineteen climate factors (AUC = 0.894, TSS = 0.592). Under the high-emission scenario (SSPs585), the highly suitable habitat for P. sibirica is expected to gradually shrink towards the southeast and northwest, while expanding in the northeast and southwest. After the 2050s, highly suitable habitats are projected to completely disappear in Shandong, while new suitable areas may emerge in Tibet. Additionally, the total area of suitable habitat is projected to increase in the future, with a more significant expansion under the high-emission scenario (SSPs585) compared to the low-emission scenario (SSPs126) (7.33% vs. 0.16%). Seasonal changes in precipitation are identified as the most influential factor in driving the distribution of P. sibirica.

Moisture is the most important environmental factor limiting seed regeneration of shrubs in desert areas. Therefore, understanding the effects of moisture changes on seed germination, morphological and physiological traits of shrubs is essential for vegetation restoration in desert areas. In March to June 2023, in a greenhouse using the potting method, we tested the effects of soil moisture changes (5%, 10%, 15%, 20% and 25%) on seed germination and seedling growth of six desert shrubs (Zygophyllum xanthoxylum, Nitraria sibirica, Calligonum mongolicum, Corethrodendron scoparium, Caragana korshinskii, and Corethrodendron fruticosu). Results showed that (1) seed germination percent and vigor index were significantly higher at 15 and 20% soil moisture content than at 5 and 10%; (2) shoot length, primary root length, specific leaf area and biomass of seedlings were significantly higher in the 15% and 20% soil moisture content treatments than in the 5% and 10% treatments; (3) superoxide dismutase activity (SOD) and soluble protein content (SP) decreased with decreasing soil water content, while peroxidase activity (POD) and catalase activity (CAT) showed a decreasing and then increasing trend with increasing soil water content; (4) the six seeds and seedling of shrubs were ranked in order of their survivability in response to changes in soil moisture: Caragana korshinskii > Zygophyllum xanthoxylum > Calligonum mongolicum > Corethrodendron scoparium > Corethrodendron fruticosu > Nitraria sibirica. Our study shows that shrub seedlings respond to water changes by regulating morphological and physiological traits together. More importantly, we found that C. korshinskii, Z. xanthoxylum and C. mongolicum were more survivable when coping with water deficit or extreme precipitation. The results of the study may provide a reference for the selection and cultivation of similar shrubs in desert areas under frequent extreme droughts in the future.