Invasive plants are foreign species that establish, reproduce, and spread outside their historical and current natural distribution ranges, causing significant adverse effects on local ecosystems, landscapes, and socioeconomic conditions. These invasive plant species alter ecosystem services through various mechanisms, posing an increasingly serious threat to global environmental health and ecological security. Soil provides the fundamental space for plant survival, and therefore understanding the impact of invasive plants on soil is crucial for comprehending their colonization, reproduction, and spread. Based on a comprehensive analysis of domestic and international literature, this paper systematically reviews recent research on the effects of invasive plants on soil properties, including physical and chemical characteristics, enzyme activity, and soil microorganisms. This paper explores the interactions between invasive plants and soil, summarizes the changes in soil characteristics following plant invasion, and discusses how invasive plants affect soil properties. Additionally, it provides an outlook on future research directions in this field, aiming to uncover the multifaceted impacts of invasive plants on soil, reveal the mechanisms of invasion, and offer scientific evidence for the effective prevention and control of invasive plants.

Aims Photovoltaic (PV) arrays facilitate the development of distinct plant assemblages by mediating local gradients of water, heat, light, and soil environment. This environmental heterogeneity induces a “niche differentiation-dominant species reorganization” effect among plant species in semi-arid coal mining subsidence areas. Consequently, there is an urgent need to elucidate the impacts of PV construction on the composition, diversity, and stability of plant community, as well as the driving mechanisms.

Methods To uncover the impact mechanisms of PV construction on vegetation restoration following the implementation of “PV + Ecological Remediation” project, this study investigated a PV field established on coal mining subsidence land in the Yushenfu mining area. By conducting field quadrat surveys and multivariate statistical analyses, we compared the characteristics of plant community composition, structure, and stability across distinct microhabitat units of the PV arrays (front eaves of the PV panel, underside of the PV panel, rear eaves of the PV panel and middle of the PV panel) with those in naturally recovered coal mining subsidence areas and in control areas (non-subsided lands). The driving mechanisms of community differentiation were analyzed by integrating soil physicochemical properties and microclimatic factors.

Important findings (1) The diversity and stability of plant communities significantly decreased in naturally recovered coal mining subsidence areas, while plant density increased due to the establishment of annuals and biennials. Compared to the naturally recovered areas, the front eaves and rear eaves of the PV panel enhanced plant density, diversity, and stability, whereas the underside and middle of the PV panel showed opposite trends. (2) Plant communities in the front and rear eaves of the PV panel were dominated by drought-tolerant perennial species. In contrast, the underside of the PV panel screened by shading and high humidity conditions, was primarily dominated by mesophytic annual and biennial species, showing reduced species similarity to control area. (3) Soil moisture and light intensity were common dominant environmental factors influencing community characteristics across the study area. Beyond these shared drivers, the key driving factors for different microenvironments included soil organic matter content in the front and rear eaves of the PV panel, air humidity underside of the PV panels and soil bulk density in the middle of the PV panel. Overall, the construction of the photovoltaic power station induced spatial differentiation in the plant community structure within the subsided land PV area, resulting in significant heterogeneity in vegetation restoration effectiveness. Among the microhabitat units, the front eaves of the PV panel exhibited the strongest promotive effect, while the rear eaves of the PV panel exhibited a limited promotive effect on vegetation restoration in the subsidence area. Conversely, the middle and underside of the PV panel showed significant inhibitory effects. These results provide a strong scientific basis for implementing targeted ecological optimization measures following the deployment of “PV + Ecological Remediation” projects.

Aims Grassland ecosystems store large amounts of organic carbon. In recent years, the construction of large-scale photovoltaic (PV) power plants in grassland areas has dramatically altered the microclimate, vegetation, and soil characteristics of the grassland ecosystem, thereby affecting the carbon cycle. However, there is a lack of systematic research regarding the effects of PV development on vegetation and soil storage.

Methods To investigate the impact on the carbon stock of desertified grassland ecosystems, this study adopts a space-for-time substitution method to analyze the changing patterns of aboveground biomass carbon density, total soil carbon, organic carbon, readily oxidizable organic carbon stock, and other indices at the Tala Beach Photovoltaic Power Station in Republican County, Qinghai Province, considering different years of construction.

Important findings The results showed that: (1) under the PV panels, between the panels, and outside the station in the study area, the average total soil carbon storage were 118.83, 119.08, and 108.15 t·hm^-2, respectively; the organic carbon was 61.97, 61.29, and 58.14 t·hm^-2, respectively; the readily oxidizable organic carbon was 23.95, 25.21, 19.18 t·hm^-2; the aboveground biomass carbon density was 47.58, 43.69, 26.03 g·m^-2, respectively. Except for the organic carbon and readily oxidizable organic carbon storage under the panels, values of other indices under and between panels were significantly larger than those outside the station. (2) As the establishment time of the power station increased, the aboveground biomass carbon density of the vegetation increased at a rate of 6.91 and 10.01 m^-2·a^-1 under the panels and between the panels, respectively. There was a significant positive correlation between soil organic carbon and easily oxidized organic carbon stocks and the number of the establishment year of PV. (3) Above-ground biomass carbon density was mainly affected by the construction of PV and vegetation cover, and the construction of PV also affected the easily oxidized organic carbon stock the most. In conclusion, although the construction of PV did not significantly affect the total soil carbon storage in the short term, it significantly increased the aboveground biomass carbon density soil organic carbon and readily oxidizable organic carbon stock. In the future, the soil in the region will continue to function as a carbon sink as the establishment time of PV increases. Therefore, large-scale photovoltaic development has a positive effect on enhancing the carbon sequestration capacity of alpine desert grassland in China and achieving the goal of carbon neutrality.

Aims Ants play an important role in material cycling and energy flow in subtropical forest ecosystems. However, there remains a knowledge gap regarding how different canopy tree species regulate ant community structure by altering the seasonal patterns of understory microclimate, soil surface conditions, and litter properties.

Methods From July 2023 to March 2024, we conducted an in situ pitfall trap survey in a common garden at the Fujian Sanming Forest Ecosystem National Observation and Research Station. We examined the seasonal dynamics of ant community structure, taxonomic and functional groups, and diversity under six representative canopy tree species in a mid-subtropical evergreen broadleaf forest.

Important findings A total of 30 389 ants were collected, belonging to 19 genera and 30 species. The dominant species were Pheidole nodus and Crematogaster rogenhoferi. Ant diversity was higher in summer and autumn and lower in winter and spring. Tree species significantly influenced ant abundance, with the following order: Liquidambar formosana> Castanopsis carlesii> Sapindus saponaria > Cunninghamia lanceolata > Michelia macclurei > Pinus massoniana. Sampling season and its interaction with tree species also significantly affected the structure of ant functional groups. For example, the abundance of generalized Myrmicinae was significantly higher under Cunninghamia lanceolata in summer, while climate specialists were relatively more abundant under Castanopsis carlesii in spring and less abundant under Pinus massoniana. Canonical correspondence analysis (CCA) revealed that soil temperature, soil organic matter content, aboveground biomass, and litter production together explained over 50% of the variation in ant community structure. These findings provide foundational data for understanding the structural and functional relationships between tree species and ants, and potentially other similar soil fauna, in central subtropical forest ecosystems.

Aims Revealing the regional differentiation of functional traits and their adaptative strategies of widely distributed species is of great ecological significance for predicting the adaptation of plants under climate change.

Methods Setaria viridiswas studied for its 18 water-carbon-related stem and leaf traits in 9 study sites along the precipitation gradient from southeast to northwest China. The trait network analysis and principal component analysis were used to quantify the regional differentiation of traits to clarify their habitat adaptative strategies.

Important findings (1) In humid regions, Setaria viridis exhibited the largest vessel diameter and specific leaf mass; in the semiarid/semihumid region, Setaria viridis exhibited the highest maximum net photosynthetic rate per unit leaf area, anatomical maximum stomatal conductance and stomatal area fraction; in arid regions, Setaria viridis exhibited the highest thickness-to-span ratio of vessel and maximum net photosynthetic rate per unit leaf mass. These trait variations revealed the adaptative strategies of Setaria viridis in different regions. (2) Both the correlations between traits and the connectivity of the network decreased with the decrease of precipitation, while the complexity of the network increased. The proportion of positive correlations among the trait network reached the maximum in the semiarid/semihumid regions, showing the best cooperative relationship between plant traits, which may be related to the balanced allocation of water and light resources in this region. (3) The trait network of nine sites indicated that the adaptation of Setaria viridis along the precipitation gradient was mainly regulated by stomatal traits. This study helps us to reveal the mechanisms of plant adaptation under the background of climate change.

Aims The Shenzhen Bay Mangrove Nature Reserve is the only national nature reserve in China located within an urban area. Studying the potential biodiversity of urban mangrove wetlands, which are significantly impacted by human disturbance, can provide a pathway for the sustainable management of mangrove ecosystems.

Methods This study conducted an ecological survey of different areas (core/non-core) in the Shenzhen Bay Mangrove National Nature Reserve. Species co-occurrence and distribution probability was assessed using the hypergeometric method, and the vegetation characteristics of the area were analyzed based on the survey data.

Important findings (1) A total of nine mangrove species were mainly distributed in the Shenzhen Bay Mangrove Nature Reserve, with Kandelia obovata being the dominant species. In the core area, K. obovata had the highest importance value (IV) (mean = 81.2%), while its importance value in the non-core area was significantly lower, where Sonneratia apetala and S. caseolaris appeared. (2) In the Shenzhen Bay mangrove ecosystem, S. caseolaris and S. apetala exhibited a strong coexistence tendency, with a z-score value of 2.82. Meanwhile, S. apetalaand K. obovata displayed competitive exclusion, with a z-score value of -2.41. z-score values reflect non-random species co-occurrence patterns. (3) A significant positive correlation was found between the observed species diversity and the community completeness index in the Shenzhen Bay mangroves. The higher the community completeness, the higher the observed species diversity. Some non-core area plots are at risk of S. apetala spreading, and ecosystem management and protection should be strengthened. The distribution probability of K. obovata in the core area (0.51 ± 0.09) is significantly higher than that in the non-core area (0.41 ± 0.15). However, in certain plots of the core area, such as the plots in the mid-tide zones of transects 8, community completeness is relatively low. It is recommended to appropriately replant native mangroves to enhance species diversity.

Aims Rhododendron xiaoxidongense is an endemic, rare and endangered species in China, with a narrow distribution in the central part of the Luoxiao Mountains. Rhododendron xiaoxidongense was once assessed as extinct (EX) because its habitat is extremely limited and individual numbers are so scarce that it is difficult to find in the wild. However, as details on the resource status, population structure and dynamics of the species are lacking, the conservation of this species is severely constrained. This study aims to clarify the survival status and future development trend of the population, and key factors affecting population regeneration by analyzing the structure and dynamics characteristics of the existing populations of R. xiaoxidongense, which will provide scientific basis for the conservation, management, and revitalization of wild populations.

Methods Based on the investigated parameters, the age structure of the R. xiaoxidongense population was obtained using a space-for-time substitution method. Subsequently, the dynamic index, static life table, survival curves and survival function curves of the population were determined to analyze the population structure characteristics and survival potential. The time series prediction model was employed to predict the future development trend of the population, and the aggregation degree index was used to determine the spatial distribution pattern of the population.

Important findings (1) The age structure of the four populations of R. xiaoxidongense was incomplete, with an overall trend of more middle-aged and mature individuals and a severe lack of low-aged and old individuals, and the age structure tended to be a decline type. (2) The dynamic index of adjacent age class showed a fluctuating trend of “decline—growth—stability—decline” with increasing age class, the dynamic index without external interference > the dynamic index under external disturbance (V′_pi) > 0, and V′_pi was close to 0. The maximum risk probability in response to random disturbance under external environmental interference was 11.11%, indicating that the population had a high probability of risk from external disturbance and had a very weak resistance to disturbances. (3) The life expectancy was highest at age class I, and the population survival curve tended to be Deevey-II type. (4) The mortality rate and vanish rate curves showed a dynamic pattern of “increase—decrease—increase”, which indicated the population was in an unstable state. (5) The survival function curve showed the trend of sharp decline in the early stages, relative stability in the middle stages, and slow decline in the later stages, and entered the decline phase at a relatively young age class (age class 2.25), which indicated that the population had weak viability. (6) In the future, after the 2, 4, 6, and 8 age classes, the number of low and middle-aged individuals in the population would decrease, in contrast, the number of adult and old individuals would increase, indicating that the population will face a risk of decline. (7) The overall spatial pattern of the population was clumped distribution, but the degree of aggregation decreased with increasing age class, transitioning to a random distribution in age classes VII-VIII. In summary, the small population size, narrow distribution range, low resistance to external disturbance, and difficulty in seedling regeneration are the main factors leading to the endangered status of the R. xiaoxidongense. We suggest strengthening habitat protection and tending management of the R. xiaoxidongense population, and achieving population conservation and revitalization through multiple approaches, including wild reintroduction and near situ conservation.

Aims In this study, we analyzed the genetic diversity and structure of Haloxylon ammodendron populations in the Turpan-Hami area, Xinjiang. The objective is to reveal the genetic diversity and genetic structure of the Haloxylon ammodendron population in the region, so as to provide a scientific basis for the conservation of Haloxylon resources in these areas.

Methods We sampled 154 individuals from 13 natural populations of H. ammodendron. Based on single nucleotide polymorphism (SNP) and chloroplast sequences genome data obtained by population resequencing, nucleotide diversity, haplotype diversity and genetic differentiation coefficient were calculated. The genetic structure was assessed by conducting ADMIXTURE, principal components analysis (PCA), phylogenetic tree and chloroplast haplotype network analyses.

Important findings The SNPs variations indicated that population Qitai exhibited higher nucleotide diversity compared to Barikun, Xishan and Qincheng Township in Hami City. Haloxylon ammodendron populations in the Turpan-Hami area can be divided into four groups. Populations in the Barkol County of Hami City has similar genetic composition with populations in the southeast of Junggar Basin and Gansu Province, and unique genetic compositions were retained in the Gaochang District and Xishan Township. The chloroplast genome analyses results showed that 39 haplotypes were detected, and Qitai region had the most diverse haplotypes and the highest genetic diversity. The haplotypes from Qitai were found in both Turpan-Hami and Gansu populations. This may suggest that H. ammodendron populations in the Turpan-Hami region originated from Qitai and dispersed eastward.

Aims In nature, resources essential for plant growth are heterogeneously distributed, and such environmental heterogeneity is ubiquitous. Clonal plants have evolved various strategies such as physiological integration and clonal morphological plasticity to deal with environmental heterogeneity, but the role of the resource storage capacity has been scarcely studied.

Methods Here, we buried rhizome fragments of Leymus chinensis in different lengths (0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 cm), each containing one bud-bearing node, in pots filled with a local soil, and recorded the sprouting status of the rhizomatous buds and the emergence and growth of the bud-forming clonal ramets.

Important findings The bud sprouting rate and the emergence rate, establishment rate, mass of newly produced clonal ramets increased with increasing length of the initial rhizome fragments, but only those clonal ramets forming on the rhizome fragments of 4.0 and 5.0 cm long could establish (i.e., grow to a self-sustaining state). These results suggest that storage of resources is an important strategy for clonal plants to deal with environmental changes and disturbances, and thus is of great significance for their growth and propagation. Additionally, our findings are potentially useful for restoring degraded grassland and for promoting grassland production and sustainability.

Aims The growth of trees is highly dependent on variations in the combination of external environmental factors such as precipitation and temperature. As a dominant coniferous species in the Qilian Mountains, Juniperus przewalskii’s growth dynamics in response to temperature and precipitation changes is crucial for the development of the forest ecosystem in the Qilian Mountains. Our objective is to identify the seasonal patterns of xylem formation of J. przewalskii and to clarify the characteristics of its intra-annual radial growth rate in response to variations in precipitation and temperature.

Methods This study selected five trees at altitude 3 000 m in the Qilian Mountains, collecting microcores from each tree every five days, and employed the microcoring method to complete laboratory experiments.

Important findings The results showed that: (1) The growth of J. przewalskii began around May 10 (day of the year (DOY) 131 ± 3) and ended around August 10 (DOY 223 ± 3), with a total growing season of (92 ± 2) d. (2) The dynamics of xylem cell number exhibited an S-shaped intra-annual trend, while the growth rate showed a Bell-shaped intra-annual trend, with a maximum growth rate of 0.32 units·column^-1·d^-1. The maximum growth rate occurred 12 d earlier than the summer solstice. (3) Hydrothermal variations emerge as primary drivers of intra-annual radial growth, with both temperature and precipitation demonstrating significant positive effects on growth rates. Notably, precipitation shows a more pronounced lagged effect on the growth of J. przewalskii. The findings of this study contribute to predicting future growth trends of J. przewalskii and provide theoretical support for understanding and protecting the sustainable development of the Qilian Mountains forest ecosystem.

Aims Populus euphratica and Tamarix ramosissima are two dominant species in the Daliyaboyi oasis, located at the tail of the Keriya River in the hinterland of the Taklamakan Desert. Against the backdrop of a warming and wetting climate trend in Northwest China, the relationship between the radial growth of these two species and climate change remains unclear. This study aimed to identify the limiting factors for the radial growth of P. euphraticaand T. ramosissima and to examine the characteristics of their growth-climate relationships in the conditions of a warming and wetting climate.

Methods Tree-ring samples of P. euphraticaand T. ramosissima were collected from two sites with different groundwater depths (1.0 m and 4.4 m) at the Daliyaboyi oasis. Standard chronologies were established for the two species, and the relationships between tree-ring width index and runoff and climatic factors for both species were analyzed. The differences in the climate responses of these two species were also explored.

Important findings The results indicated that P. euphratica and T. ramosissima with different groundwater depths have different responses to climate factors. With a groundwater depth of 1.0 m, the radial growth of P. euphratica was significantly and positively correlated with precipitation in April of the previous year and April of the current year. Meanwhile, the radial growth of T. ramosissima was significantly and positively correlated with runoff in June of the previous year and precipitation in February of the current year, and was significantly and negatively correlated with air temperature in December of the previous year. With a groundwater depth of 4.4 m, the radial growth of P. euphratica was significantly and positively correlated with air temperatures in January of the previous year and January of the current year, as well as with the Palmer Drought Severity Index (PDSI) from January of the previous year to June of the current year and from August to September of the current year. Meanwhile, the radial growth of T. ramosissima was significantly and positively correlated with runoff in June of the previous year, temperatures in September of the previous year, and precipitation in December of the previous year, as well as with temperatures in April of the current year. Sliding correlation analysis suggested that, under the influence of climate warming and wetting in the Taklamakan Desert, the positive response of P. euphratica radial growth to runoff factors (January to March) weakened at a groundwater depth of 1.0 m. In contrast, T. ramosissima showed an increased positive response to precipitation in April of the previous year and runoff from January to February of the previous year. With a groundwater depth of 4.4 m, the radial growth of P. euphratica showed a shift from a positive to a significant negative correlation with air temperature during April to May and July to August of the previous year, as well as during April to May and July to August of the current year, and the relationship between radial growth of P. euphratica to PDSI changed from significant positive correlation to non-significant correlation. The relationship between radial growth of T. ramosissima and precipitation and PDSI changed from negative correlation to positive correlation. In conclusion, P. euphratica demonstrates greater dependence on long-term climate factors at the deep groundwater depth, while T. ramosissima is more sensitive to short-term hydrological factors.

Aims The understory vegetation is a key component of subtropical forests closely linked to the structure and functional services of forest ecosystems. Long-term soil warming may alter leaf functional traits, affecting species diversity and community structure in the understory. In this study, we aim to investigate the effects of long-term soil warming on leaf structural succession of dominant shrubs of subtropical natural forest.

Methods Based on an eight-year in situ soil warming (+4 °C) experiment, we examined the effects of long-term soil warming on the leaf structure of three dominant shrubs (Ardisia lindleyana, Mussaenda pubescens and Ilex dasyphylla) under warming and control treatments in a natural forest.

Important findings The results indicated that long-term soil warming affected the stomatal and anatomical structure of leaves, leading to a decrease in stomatal density and leaf thickness, along with an increase in specific leaf area. Specifically, the thickness of the palisade and spongy tissue in large shrubs (Ilex dasyphylla) significantly decreased, while the thickness of the lower epidermis increased, likely due to the proliferation of dense epidermis trichomes on leaves induced by soil warming. In subshrub (Ardisia lindleyana), both epidermis and palisade tissue thickness decreased, while the spongy tissue thickness increased, reflecting an adaptive strategy to enhance water retention capacity and buffer water pressure of the leaves. In ground-lying shrubs (Mussaenda pubescens), the thickness of the upper epidermis and spongy tissue decreased, while palisade tissue thickness increased, likely enhancing water transport efficiency and drought tolerance of the leaves. Our results demonstrate that long-term soil warming has significantly impacted the water use efficiency of understory shrubs in subtropical forest. These findings provide scientific insights into the response mechanisms of understory shrub structure to global warming, with significant contribution to biodiversity conservation.

Aims The combined effects of ozone (O₃) pollution and nitrogen (N) addition on plant photosynthesis are still controversial, which may be related to factors such as measurement period, time, and leaf position. This study mainly explored the differences in the response of photosynthetic parameters of poplar to O₃ and N addition at different growth stages, diurnal variation, and leaf positions, in order to comprehensively understand the combined effects of O₃ pollution and N addition on plant carbon sequestration.

Methods The cuttings of hybrid poplar clone 107 (Populus euramericana cv. ‘74/76’) were exposed to six open top chambers. Two O₃ concentration treatments were set up (NF, non-filtered ambient air; NF45, NF + 45 nmol·mol^-1 O₃), with four N addition treatments nested under each O₃ treatment (N0, no N added; N50, N0 + 50 kg N·hm^-2·a^-1; N100, N0 + 100 kg N·hm^-2·a^-1; N200, N0 + 200 kg N·hm^-2·a^-1). The photosynthetic parameters of poplar at different growth stages, daily times, and leaf positions were measured.

Important findings When averaged across four N treatments, NF45 treatment significantly reduced the entire growth season photosynthetic rate (P_n), stomatal conductance (g_s), and chlorophyll content (SPAD) by 44.2%, 18.2%, and 24.7% compared with NF treatment, respectively. However, O₃ increased the intercellular CO₂ concentration (C_i) by 9.0%, indicating that the reduction of P_n by O₃ was mainly limited by non-stomatal factors. The results showed that NF45 treatment had a greater reduction in leaf P_n and SPAD at the middle and late stages of growth than at the early stages. The response of P_n and SPAD to O₃ varied among different leaf positions. O₃ significantly reduced P_n and SPAD at the lower leaf position, while O₃ increased P_n and SPAD at the topmost leaf position, indicating a compensatory effect of plants in response to O₃ stress. O₃ caused varying degrees of decrease in P_n of poplar at different times within a day, but there was no statistically significant interaction between O₃ and time on the photosynthetic parameters. The N addition significantly increased the leaf P_n and SPAD of poplar throughout the entire growing season, with no significant effect on g_s, but significantly reduced C_i. There was no significant difference in the promotion of photosynthesis by N addition at different growth stages and leaf positions. In addition, no significant interaction effect was observed between O₃ and N addition on all photosynthetic parameters, indicating that N addition did not alleviate the negative impact of O₃ on poplar photosynthesis.

Aims Diatoms are an important component of marine phytoplankton, and their photosynthetic production reaches more than 40% of the ocean primary productivity. The combined effects of enhanced solar ultraviolet radiation (UVR) and seawater warming will affect the photosynthesis of diatoms and their contribution to the primary productivity. In this study, we mainly explored the photosynthetic physiological regulation of diatoms in response to UVR radiation by warming, in order to further understand the effects of marine environmental changes on the photosynthesis of diatoms.

Methods Thalassiosira weissflogii was cultured at 18 °C and 24 °C and exposed to high visible light (photosynthetically active radiation (PAR), 400-700 nm) and UVR (PAR+UVR, 280-700 nm) to monitor changes in photosystem II (PSII) function and other physiological responses.

Important findings PAR and PAR+UVR inhibited the maximum photochemical efficiency (F_v/F_m) of PSII in T. weissflogii. The photoinactivation rate constant (K_pi) of PSII increased significantly in the presence of UVR. The ratio of repair rate constant to photoinactivation rate constant of PSII (K_rec/K_pi) in UVR was similar to that under low temperature. Analysis of PSII subunit turnover showed that warming under visible light allowed cells to maintain a high D2 (PsbD) pool, whereas warming under UVR synergistically promoted rapid clearance of damaged D1 (PsbA). In addition, the activities of superoxide dismutase and catalase were higher in the cells under the increased temperature, and low level of non-photochemical quenching was induced under all treatments. Our results showed that warming can promote the photosynthetic performance of T. weissflogii by adjusting its PSII repair cycle to counteract the inhibitory effect of UVR.

Aims Mangrove plants play crucial ecological roles in coastal wetland ecosystems, yet environmental stressors such as salinity-alkalinity and heavy metal pollution (e.g., copper) may significantly impact their photosynthesis and growth. This study aimed to investigate the photosynthetic physiological and ecological responses of three mangrove species—Kandelia obovata, Laguncularia racemosa and Bruguiera gymnorhiza—under combined salt and copper stress. The goal was to provide a scientific basis for effective management and restoration strategies to maintain mangrove wetland ecological functions.

Methods Controlled field experiments were conducted using combined salt and copper treatments. Principal component analysis and generalized linear mixed models were employed to assess changes in chlorophyll fluorescence characteristics, leaf structure (leaf length, leaf area, specific leaf area), and biochemical components (relative chlorophyll content (SPAD), total copper content, total carbon content, total nitrogen content) across different treatment conditions.

Important findings The results demonstrated that under low-concentration salt and copper treatments, the average maximum quantum yield of photosystem II (F_v/F_m) in three mangrove species ranged from 0.764 to 0.866, indicating strong stress resistance. Among them, Kandelia obovata and Laguncularia racemosa exhibited superior stress tolerance compared to Bruguiera gymnorhiza. The performance index (PI_abs) and potential activity of PSII (F_v/F_o) ranged from 0.63 to 1.89 and from 3.81 to 6.33, respectively, with an overall declining trend as salt concentrations increased, suggesting that high salinity inhibited photosynthetic activity. Low copper concentrations showed no significant impact on F_v/F_m or F_v/F_o, while high copper levels suppressed photosynthesis. Under combined salt-copper treatments, chlorophyll fluorescence parameters of the three mangroves remained stable, implying a counteracting effect of copper on salt stress. Principal component analysis (PCA) revealed temporal variations in the correlations among chlorophyll fluorescence parameters, leaf structural traits, and biochemical components across treatments. Species differentiation was indistinct in July 2019, Laguncularia racemosa showed clear separation in December 2019, and Bruguiera gymnorhiza was distinctly separated in August 2020. Overall, species differentiation across the three sampling periods was not pronounced. Generalized linear mixed model (GLMM) analysis highlighted significant positive correlations between F_v/F_m, F_v/F_o, and SPAD values in Kandelia obovata, but negative correlations with total nitrogen (N) content. Its PI_abs and SPAD values were positively linked to total copper content. In Laguncularia racemosa, PI_abs showed a strong positive correlation with SPAD values. For Bruguiera gymnorhiza, F_v/F_m and F_v/F_o were positively correlated with SPAD values and total carbon (C) content, yet negatively associated with total nitrogen content.

Aims The present study aimed to quantify the characteristics of soil organic carbon (SOC) fractions and the carbon (C) pool management index (CPMI) in the topsoil (0‒20 cm) of the four different natural forest types in the temperate climate-transition area in Pangquangou National Nature Reserve, Shanxi Province. The study’s findings may offer a potential valuable reference and significant insight into enhancing soil C storage and the forestland quality, as well as the sustainable forest management within native woodlands in the future.

Methods A total of four forest types, which were characterized by similar site conditions, were selected to investigate the variations and influencing factors of soil C fractions and the CPMI in the topsoil layer. Here, soil samples were collected from representative forestlands, including Betula platyphylla forest (BP), Picea wilsonii + Larix gmeliniivar. principis-rupprechtii + Betula conifer-broadleaf mixed forests (PLB), P. meyeri + P. wilsonii conifer mixed forest (PP), L. principis-rupprechtii forest (LP) and scrub-grass land (CK), respectively. The contents of SOC and its fractions were measured, and CPMI was calculated. Pearson correlation and redundancy analysis (RDA) were used to examine the relationships between soil environmental factors and carbon pool characteristics. Random forest analysis (RFA) was used to identify the soil properties significantly affecting the soil C fractions and CPMI.

Important findings The buildup of SOC and its fractions, as well as soil C pool index (CPI) and CPMI, was influenced by the distinct species composition and forest structure of different forest types. First, the contents of SOC were as follows: PP ˃ PLB ˃ BP ˃ LP, which increased by 74.22%, 41.62%, 39.05% and 3.01% respectively in the topsoil layer compared to CK. For soil C components, dissolved organic carbon (DOC), easily oxidizable organic carbon (EOC), microbial biomass carbon (MBC) and recalcitrant organic carbon (ROC) contents from the different forest types followed similar trends to the concentration of SOC at the surface layer where PP recorded the maximum concentration. Here we show that MBC and DOC contents did not vary significantly among different forest types. Second, our data clearly evidenced that the DOC:SOC and ROC:SOC were significantly higher and lower in LP and BP, respectively, in comparison to the other three forest types. Conversely, the EOC:SOC, MBC:SOC and AOC:SOC remained consistent, and no significant differences were observed among the four forest types, with the PP exhibiting the lowest values. Third, the variation tendency of CPMI followed the same trend as SOC, while the CPMI in LP was significantly lower than that observed in other forest types. RDA revealed that TN and NO₃^--N contents play a prominent role in the variation characteristics of soil C pools in the natural forests in the temperate climate-transition zone. Furthermore, we observed that soil water content and available potassium had a significant impact on soil C fractions, while the CPMI was significantly affected by soil water, pH and TP. Taken together, our findings demonstrate that both temperate mixed forests, especially coniferous mixed forests promoted SOC stock by increasing C pool fractions contents, which in turn promoted soil fertility and quality of the forest land in a temperate transition zone. The results of this study emphasize the key role of the interplay between soil nitrogen, soil water and soil pH in predicting soil C pool in temperate forests. Consequently, these results should be considered by the forestry sectors, and suggest that the forest ecological restoration should promote biodiversity especially conifer species in the context of improving C stock and soil quality in temperate forests. Thus, it is predicted that increasing soil nitrogen and species diversity may be an effective measure for improving soil C sequestration in natural forest ecosystems in the temperate climate-transition zone.