Xiali Guo

Effective coastal management of seagrass systems requires identifying both extant meadows and degraded areas suitable for recovery. However, these decisions often rely on distribution maps that provide limited information on ecological condition or carbon potential. Here, we develop an ensemble habitat modeling (EHM) framework for seagrass meadows around Guanglu Island, China, to test whether a habitat suitability index (HSI) can serve as a proxy for ecological performance and carbon storage potential. By integrating multiple single-algorithm predictions, the ensemble model reduced algorithm-dependent variation and achieved strong predictive performance (ROC = 0.967, TSS = 0.876), with predictions capturing 92.59% to 98.98% of the 2023 field-mapped meadow area. HSI was positively associated with aboveground biomass and shoot density. A predictive model fitted directly with biomass as the response showed that aboveground biomass increased with HSI, with a leave-one-out cross-validated RMSE of 77.68 g DW m⁻². High HSI samples also exhibited smaller relative deviations from the theoretical biomass–density envelope and a greater realized fraction of theoretical biomass potential. Modeled sediment carbon densities were consistent with the 2023 sediment comparison, thereby supporting conditional carbon stock screening. Our findings support the use of ensemble-derived HSI as a local spatial proxy for biomass-related ecological potential, rather than as a direct measure of habitat quality, actual biomass, or realized carbon stock. By separating predicted suitable habitat, observed meadow distribution, and model-based potential carbon stock, the framework provides a spatial screening tool for conservation prioritization, restoration opportunity assessment, and blue carbon planning under explicitly stated ecological and modeling assumptions.

Cryptocaryeae, as a significant tribe within the Lauraceae family with important economic and ecological value, comprises over 850 species. Its common ancestor dates back to approximately 123 million years ago, in the early Cretaceous, originating in tropical Africa and Asia. Understanding how leaf and fruit functional traits of Cryptocaryeae trees (Lauraceae) respond to environmental fluctuations is crucial for protecting the structure and function of forest ecosystems. In this study, we investigated the influence of environmental factors on leaf and fruit morphological traits in the tropical tribe Cryptocaryeae. Based on an established phylogenetic framework for Cryptocaryeae, we compiled a dataset containing 17,117 morphological observations across 369 species. The analyzed traits included leaf length, leaf width, leaf area, fruit length, fruit diameter, and fruit size. Through analyzing trends of leaves and fruits morphological traits across the latitude and longitude and their relationship with environmental factors, and by quantifying the relative contributions of environmental factors to these traits, we demonstrated that leaf morphology exhibited distinct latitudinal and longitudinal zonation and was sensitive to environmental fluctuations, especially to temperature changes. In contrast, the change of fruit morphological traits was comparatively conservative in their variation, mainly affected by precipitation. These findings suggest that different plant traits may employ different trade-off strategies during environmental adaptation. Highlighting the importance of integrating ecological and evolutionary perspectives on leaf and fruit morphological traits of tropical Cryptocaryeae trees could provide insights into understanding plant environmental adaptation.

Temperate grasslands are highly sensitive to climate change and play a crucial role in terrestrial carbon cycling. In the context of global warming, heterotrophic respiration (Rh) has intensified, contributing significantly to atmospheric CO₂ emissions. However, seasonal patterns of Rh, particularly differences between the growing season (GS) and non-growing season (non-GS), remain poorly quantified. This study used daily eddy covariance data from multiple flux towers combined with MODIS GPP and NPP products to estimate Rh across temperate grasslands from 2002 to 2021. We examined interannual variations in GS and non-GS Rh contributions and assessed their relationships with key hydrothermal variables. The results showed that mean Rh during GS and non-GS was 527 ± 357 and 341 ± 180 g C m⁻² yr⁻¹, respectively, accounting for 57.8 ± 14.6% and 42.2 ± 14.6% of the annual Rh. Moreover, GS Rh exhibited a declining trend, while non-GS Rh increased over time, indicating a gradual convergence in their seasonal contributions. This pattern was primarily driven by increasing drought stress in GS and warmer, moderately moist conditions in non-GS that favored microbial activity. Our findings underscore the necessity of distinguishing seasonal Rh dynamics when investigating global carbon cycle dynamics. Future earth system models should place greater emphasis on seasonal differences in soil respiration processes by explicitly incorporating the influence of soil moisture on the decomposition rate of soil organic carbon, in order to improve the accuracy of carbon release risk assessments under global change scenarios.

Due to climate effects and human influences, wildfire regimes in boreal forests are changing, leading to profound ecological consequences, including shortened fire return intervals and elevated tree mortality. However, a critical knowledge gap exists concerning the spatiotemporal dynamics of fire-induced tree mortality specifically within the vast North American boreal forest, as previous studies have predominantly focused on Mediterranean and tropical forests. Therefore, in this study, we used satellite observation data obtained by the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua and Terra MCD64A1 and related database data to study the spatial and temporal variability in burned area and forest mortality due to wildfires in North America (Alaska and Canada) over an 18-year period (2003 to 2020). By calculating the satellite reflectance data before and after the fire, fire-driven forest mortality is defined as the ratio of the area of forest loss in a given period relative to the total forest area in that period, i.e., the area of forest loss divided by the total forest area. Our findings have shown average values of burned area and forest mortality close to 8000 km²/yr and 40%, respectively. Burning and tree loss are mainly concentrated between May and September, with a corresponding temporal trend in the occurrence of forest fires and high mortality. In addition, large-scale forest fires were primarily concentrated in Central Canada, which, however, did not show the highest forest mortality (in contrast to the results recorded in Northern Canada). Critically, based on generalized linear models (GLMs), the results showed that fire size and duration, but not the burned area, had significant effects on post-fire forest mortality. Overall, this study shed light on the most sensitive forest areas and time periods to the detrimental effects of forest wildfire in boreal forests of North America, highlighting distinct spatial and temporal vulnerabilities within the boreal forest and demonstrating that fire regimes (size and duration) are primary drivers of ecological impact. These insights are crucial for refining models of boreal forest carbon dynamics, assessing ecosystem resilience under changing fire regimes, and informing targeted forest management and conservation strategies to mitigate wildfire impacts in this globally significant biome.

Due to climate effects and human influences, wildfire regimes in boreal forests are changing, with noticeable ecological consequences shortening the fire return interval and increasing forest tree mortality. However, our understanding of the spatio-temporal patterns of fire-induced mortality in boreal forests remains limited, as research has predominantly focused on Mediterranean and tropical forests. In this study, we used satellite observations to study the spatial and temporal variability in burned area and forest mortality due to wildfires in North America (Alaska and Canada) over an 18-year period (2003 to 2020). The study has shown average values of burned area and forest mortality close to 8000 km2/yr and 40%, respectively. Burning and tree loss are mainly concentrated between May and September with a corresponding temporal trend in the occurrence of forest fires and high mortality. Large-scale forest fires were primarily concentrated in Central Canada, which however did not show the highest forest mortality (in contrast, recorded in Northern Canada). A correlation analysis based on general linear models showed that fire size and duration, but not the burned area, had significant effects on post-fire forest mortality. Overall, the study shed light on the most sensitive forest areas and time period to the detrimental effects of forest wildfire in boreal forests of North America.

As a tree family with important economic and ecological significance, the adaptation mechanism of Cryptocaryeae trees (Lauraceae) to environmental fluctuations is crucial for protecting the structure and function of forest ecosystems. This study focuses on the effects of environmental climate on the adaptability of leaf and fruit functional traits. Through analyzing trends in the distribution of leaves and fruits across the latitude and longitude and their relationship with environmental factors, and by quantifying the relative contributions of environmental factors to these traits, we demonstrated that leaf morphology exhibits distinct latitudinal zonation and sensitivity to environmental fluctuations, especially to temperature changes. In contrast, the change of fruit is relatively conservative, mainly affected by annual precipitation. This indicates that in the process of plant adaptation to the environment, different functional traits may have independent adaptation mechanisms and different trade-off strategies, and plants themselves also have different trade-off strategies. Highlighting the importance of integrating ecological and evolutionary perspectives and considering phylogeny effects on various functional traits, it provides novel viewpoints on understanding environmental adaptation in plants.

Non-structural carbohydrates (NSC) are important carbon pools in trees, and previous studies have mainly focused on the concentration of NSC in tree organs such as leaves, branches, trunk, and root, separately. However, the seasonality of the concentration of NSC in different organs among tree species in the subtropical forests is less known. In this study, we measured the seasonal dynamics of the concentration of NSC in four tree species (Nothotsuga longibracteata W. C. Cheng, Pinus kwangtungensis Chun ex Tsiang, Schima superba Gardn. et Champ, and Betula alnoides Buch.-Ham. Ex D.Don) in subtropical forests at organ levels including canopy, trunk, and root. The results showed that the concentration of NSC in conifer species was higher than that in broadleaf species. Also, the average concentration and range of the concentration of NSC were higher in the canopy than in other organs. The concentration of NSC decreased at the beginning of the growing season and increased at the end of the growing season for all species. Specifically, the concentration of NSC in tree species was significantly higher in the dry season than that in the wet season. Our results revealed the seasonal dynamics of NSC in different organs, which is beneficial to a better understanding of the growth strategies of different tree species in subtropical regions.

Increased tree species diversity can promote forest production by reducing intra-specific competition and promoting an efficient unitization of resources. However, questions remain on whether and how mixed stands affect the dynamics of intra–annual xylem formation in trees, especially in subtropical forests. In this study, we randomly selected 18 trees from a monoculture of 63-year-old Masson pine (Pinus massoniana) growing in pure stands and mixed them with 39-year-old Castanopsis hystrix in Pinxiang, southern China. A total of 828 microcores were collected biweekly throughout the growing season from 2022 to 2023 to monitor the intra-annual xylem formation. Cell production started in early March and ended in late December and lasted about 281 to 284 days. Xylem phenology was similar between mixed and pure stands. During both seasons, the Masson pine in mixed stands showed higher xylem production and growth rates than those in pure stands. The Masson pine in mixed stands produced 45–51 cells in 2022 (growth rate of 0.22 cells day⁻¹) and 35–41 cells in 2023 (0.17 cells day⁻¹). Growth rate, and not growth seasons, determined the superior xylem growth in the mixed stands. Our study shows that after 39 years of management, Masson pine and C. hystrix unevenly aged mixed stands have a significant positive mixing effect on Masson pine xylem cell production, which demonstrates that monitoring intra-annual xylem growth dynamics can be an important tool to evaluate the effect of species composition and reveal the mechanisms to promote tree growth behind the mixing effect.