As a greenhouse gas with a strong warming effect, nitrous oxide (N2O) is also one of the main substances that destroy the atmospheric ozone layer. It has a strong feedback effect on climate change. Plants are another important source of N2O emissions in terrestrial ecosystems besides soil and related studies have received extensive attention in recent years. Based on the existing research results, this paper summarizes the research methods, mechanisms and their influencing factors related to N2O emissions from terrestrial plants. Existing studies have mainly determined the changes of N2O emission from plants by in situ and in vitro methods. The potential mechanisms for N2O emission from terrestrial plants are as follows: 1) the plant produces N2O during nitrogen metabolism; 2) microbial activities in or on the surface of the plant produce N2O; and 3) the plant acts as a soil N2O channel during the gas exchange process. Plant emissions of N2O are related to internal and external factors. The internal factors include plant species, different organs of the same plant and different developmental periods, etc.; external factors include light, temperature, water, nutrients and microorganisms. However, there is still a lack of in-depth analysis on the specific mechanisms. Therefore, combining metagenomic technology to determine plant microbial genomes under different soil environmental conditions, analyzing their microbial community structure, and elucidating the microbial mechanisms underlying the flux differences of N2O emissions from plants in different habitats; Using metatranscriptome technology to determine total RNA in plant tissues and analyze the expression abundance changes of N2O emission related genes under different environmental conditions; And using isotope labeling technology to track the nitrogen metabolism process of plants, further revealing the mechanism of N2O flux changes in plants, which is of great significance for supplementing and improving N2O prediction models such as "Ecosys" for global climate change., And provide theoretical reference for the formulation of greenhouse gas emission reduction measures.

Aims Rising sea levels and the associated increase in inundation heights will alter the carbon (C) cycle in tidal marsh wetlands. However, current research primarily focuses on the impact of increased inundation on total soil C stocks, while the effects on the balance of C budget processes remain unclear. Therefore, understanding how sea level rise affects the C sequestration capacity of tidal marshes is essential for predicting future impacts. Methods To address this, our study established a ‘marsh organ’ experimental platform in the tidal marshes of the Minjiang River Estuary. Three inundation treatments—CK (control), CK + 20 cm, and CK + 40 cm—simulated the current and the projected sea level rise scenarios for the next 50 and 100 years. We measured the effects of increased inundation on the net ecosystem carbon dioxide exchange (NEE), gross primary productivity (GPP), ecosystem respiration (ER), plant biomass, plant photosynthetic characteristics, and soil physicochemical properties of the Cyperus malaccensis tidal marshes. Important findings The results showed that increased inundation led to a decrease in aboveground biomass and an increase in belowground biomass. Compared to the control (CK), GPP decreased by 27% and 32%, while ER increased by 20% and 58% in the CK + 20 cm and CK + 40 cm treatments, respectively. The reduction in GPP was related to decreased aboveground biomass and declining plant photosynthetic characteristics, such as net photosynthetic rates, stomatal conductance, intercellular CO2 concentrations. The increase in ER was associated with higher soil oxidation-reduction potential (ORP) and dissolved organic carbon (DOC) content. Under the CK, CK + 20 cm, and CK + 40 cm treatments, NEE was ?539.8, ?102.7, and 185.6 g C·m?2·a?1, respectively. These findings indicate that a 20 cm increase in inundation height leads to an increase in NEE, demonstrating a weakened carbon sequestration capacity of the Cyperus malaccensis tidal marshes. Furthermore, a 40 cm increase in inundation height results in NEE shifting from negative to positive, indicating a transition of the ecosystem from a carbon sink to a carbon source. This research provides a scientific basis for predicting and mitigating the impacts of future sea level rise on the C cycle of tidal marsh.

Aims On September 6, 2024, Super Typhoon "Yagi" made landfall in Hainan Province, China, causing severe damages to mangrove forests in the region. Methods A systematic field survey was conducted in the Dongzhaigang Mangrove Nature Reserve one week after the typhoon, selecting four representative locations, encompassing nine mangrove communities and seven typical mangrove species in total, to assess the extent of damage caused by the typhoon. Important findings The results revealed that 1) the mangrove forests at Yanfeng, situated 4.5 km from the ty-phoon’s path, and Sanjiang, located 6.5 km away, incurred severe damage, with the non-native Laguncularia rac-emosa and Sonneratia apetala populations being the most severely affected. In contrast, the mangrove forests at Tashi, 2 km from the path, experienced moderate damage, while those at Bodu, a mere 0.3 km away, sustained on-ly light damage. Field survey, complemented by UAV imagery, found that mangrove communities along tidal creek edges were more severely impacted than those in contiguous areas. 2) Among the seven species surveyed, mechanical damage to the native species Bruguiera sexangula, Kandelia obovata, Aegiceras corniculatum, and Ceriops tagal was primarily characterized by branch breakage and partial defloration. The non-native Sonneratia apetala and Laguncularia racemosa populations suffered greater damage than the native communities, with nearly complete canopy defoliation and 96.62%–99.7% of individuals sustaining damage. Approximately 9.64% of indi-viduals experienced trunk breakage or complete uprooting. 3) With the exception of the short Ceriops tagal com-munity at Bodu, which had a maximum tree height of 2 m, mangrove communities closer to the typhoon's path exhibited more severe damage. Tree height, diameter at breast height, and crown size were significantly and posi-tively correlated with damage severity; the taller the trees, the more severe the impact. Based on these damage as-sessments, it is anticipated that native communities will recover much more rapidly than non-native populations. The typhoon caused considerable short-term damage to the mangrove forests. Therefore, future mangrove restora-tion efforts should consider the species-specific wind resistance, and the mixed-species planting strategies are recommended to enhance the stability and wind resilience of mangrove communities.

Abstract Aim Different levels of tidal flooding have significant effects on mangrove sediment nutrients and stoichiometric characteristics, and plant fine root functional traits are important strategies to cope with nutrient changes. However, there is a lack of in-depth understanding on the correlation between mangrove sediment nutrient changes and fine root functional traits at different tide levels, and relatively few studies have been conducted to explore the nutrient acquisition strategies of exotic and native mangrove plants from the scale of fine root functional traits. Methods The study used native species Bruguiera sexangular and exotic species Sonneratia apetala to sample fine root and rhizosphere sediments at different tide levels. The relationship between fine root functional traits of two mangrove species and the content of nutrients and enzyme activities in rhizosphere sediments was analyzed. Important findings The results showed as follows: 1) The exotic species has higher nutrient acquisition requirements and stronger metabolic capacity than the native species, and both species are subject to a certain degree of nitrogen restriction. 2) Within a certain range, the conversion rates of nitrogen and phosphorus in sediments accelerate significantly with the increase of waterlogging degree, and the contents of ammonium nitrogen, nitrate nitrogen and available phosphorus in sediments increase with the increase of waterlogging time. 3) The specific root length of fine roots of the two species was significantly positively correlated with the nitrate nitrogen content in the sediment, indicating that the increase of sediment nutrient availability played an important role in promoting the root elongation of mangrove plants. This study can provide basic data and scientific refercne for the environmental protection of mangrove ecosystem and the development and utilization of biological resources.

Aims Accurate monitoring of gross primary production (GPP) in terrestrial ecosystems is crucial for global carbon cycle and climate change studies. The near-linear relationship between solar-induced chlorophyll fluorescence (SIF) and GPP offers a new avenue for estimating vegetation carbon uptake from local to global scales. However, the contributions of radiative, structural, and physiological information of SIF to GPP estimation at different temporal scales remain unclear. Methods This study utilizes canopy spectroscopy and eddy covariance flux data from a field site in Shangqiu, Henan, focusing on wheat and maize as representative C3 and C4 crops, respectively. By comparing methods based on the near-infrared reflectance of terrestrial vegetation (NIRv) and the fluorescence correction vegetation index (FCVI) to decompose SIF components, we refined the leave-one-out method to quantify their contributions to GPP estimation and analyzed the impact of crop type and temporal resolution on the SIF-GPP relationship. Important findings The study reveals that the SIF-GPP relationship is influenced by differences in crop type and significantly strengthens as temporal resolution decreases. At shorter temporal scales, such as half-hour and one-day, the radiative component predominantly drives the SIF-GPP relationship. However, as the time scale extends to a week or longer, the influences of structural and physiological components become increasingly significant. The methods based on NIRv and FCVI showed high consistency in decomposing the radiative, structural, and physiological components of SIF. Through a deeper understanding and precise quantification of the SIF-GPP relationship, this research enhances the application of remote sensing technologies and models in global vegetation monitoring and carbon cycle studies.

Aims The rhizosphere microbial network characteristics profoundly influence various ecological processes including soil carbon turnover, nutrient cycling and plant growth. Mycorrhizal types and root traits are crucial factors that affect plant growth and below-ground nutrient acquisition strategies. However, it is currently unclear how the root characteristics of different mycorrhizal tree species affect the topological structure of the rhizosphere microbial network. Methods This study focused on the secondary forest and investigated the root traits and rhizosphere soil microorganisms of five arbuscular mycorrhizal(AM) tree species and seven ectomycorrhizal(EcM) tree species to explore the impact and mechanisms of mycorrhizal types on root traits and rhizosphere microbial network characteristics. Important findings (1) Specific root length, root nitrogen, and root phosphorus content of AM tree species were all higher than those of EcM tree species, while root tissue density, root diameter and root nitrogen-to-phosphorus ratio showed no significant differences between the two mycorrhizal types. (2) The relative abundance of Rozellomycota in the rhizosphere of AM tree species is significantly higher than that of EcM tree species, while the relative abundance of Bacteroidota is significantly lower in AM tree species compared to EcM tree species. There is no significant difference in the diversity of rhizosphere microbial communities between different mycorrhizal type tree species. (3) The rhizosphere microbial network of EcM tree species is more complex, and the negative bacterial cohesion of EcM tree species are significantly stronger than AM tree species. (4) The specific root length of AM tree species and the root diameter and root nitrogen-to-phosphorus ratio of EcM tree species are identified as crucial factors predicting rhizosphere microbial communities. These findings suggest that the mycorrhizal type of tree species significantly influences root traits such as specific root length and nutrient content to regulate the relationship between root traits and rhizosphere microbial communities and network complexity.

Aims Studying the coordination and differences in the functional traits of leaves and fine roots can help to better understand the ecological strategies of plants from the perspective of the whole plant. Methods In this study, we measured and analyzed the leaf and root traits of 20 species of woody plants (10 trees and 10 shrubs) in the natural evergreen broadleaf forest of Wanmulin Nature Reserve in Fujian Province, and explored the differences in the coordination of root and leaf functional traits and survival strategies between tree and understory shrub species in subtropical natural evergreen broadleaf forest. Important findings It was found that there was a strong correlation (P<0.05) between the leaf nitrogen concentration and root nitrogen concentration only among the similar traits of leaf and first-order root, and it was not affected by phylogeny. There was a leaf economic axis and a leaf tissue density-leaf thickness variance axis for leaf traits in the community, and a cooperative axis (represented by negatively correlated root diameter-ratio root length) and a root economic axis (represented by negatively correlated root nitrogen concentration-root tissue density) for root traits at level 1. There was no significant correlation (P>0.05) between root and leaf economic axes. Significant differences (P<0.01) were found between tree and shrub species only in the root cooperation axis, with trees having larger root diameters and shrubs having higher specific root lengths. In addition, the SLA of shrub species was significantly larger than that of tree species. The results indicated that leaf and root traits in subtropical natural broad-leaved evergreen forests showed a complex integration relationship, and that tree and shrub species adopted different aboveground and belowground strategies to adapt to the habitat heterogeneity in the community. The results of this study expand the understanding of the coordination between root and leaf traits at the local scale, and contribute to a deeper understanding of the ecological processes and species coexistence mechanisms in the community.

Aims Plant root exudates play important roles in the feedback of plant-soil-microbes interactions. However, the responses of root carbon (C), nitrogen (N) and phosphorus (P) exudate rates and their stoichiometric characteristics in the alpine steppe to long-term grazing exclusion and relationships between them and environmental factors are still poorly understood on the Qingzang Plateau. Methods In the study, we evaluated the root C, N and P exudate rates and their stoichiometric characteristics at plant community and species level, and further reveled the relationships between root exudate characteristics at plant community level and plant community characteristics, soil factors at long-term grazing exclusion field experimental site in the alpine steppe on the Qinghai-lake Basin. Important findings Our results showed that: (1) Root C and N exudate rates and their C:P and N:P at plant community level decreased in long-term grazing exclusion treatment, but root P exudate rate and their C:N were not significantly changed. (2) The long-term grazing exclusion exerted negative effects on root C, N and P exudate rates at species species, and has significant effects on their C:P and N:P simultaneously, especially them of Leymus secalinus were decreased in grazing exclusion treatment. (3) The root exudate ability of forb species was stronger than that of grass and sedge species, mainly presenting that the root C and N exudate rate of the Aster altaicus was overwhelming higher than other species. (4) The root C and N exudate rate and N:P of exudation at plant community level were significantly related with plant diversity, plant community composition, soil water content and soil N content. The further analysis illustrated that the key factors affecting root C, N and P exudate rate were different, showing that the root C exudate rate was most affected by soil factors, while root N and P exudate rate were most affected by the plant community composition. In conclusion, the long-term enclosure has been imposing significant effects on the root exudate rate and their stoichiometry in the alpine steppe, which is of great significance for understanding the changes of other ecosystem functions after grassland enclosure management in the future.

Aims Abies beshanzuensis is classified as a first-class national protected plant in China, with only three remaining trees located in mixed evergreen-deciduous broad-leaved forest at approximately 1 750 m above sea level on the southwest slope of Baishanzu, Qingyuan County, Zhejiang Province. This study aims to gain a comprehensive understanding of the impact of environmental factors on the growth of A. beshanzuensis seedlings at different altitudes. Methods we established 11 experimental sites at varying altitudes (ranging from 500 to 1 500 m) in the Qingyuan mountain region to monitor the growth of transplanted A. beshanzuensis seedlings. By examining changes in environmental factors such as temperature, humidity, soil microorganisms, and physical and chemical properties of soil, we investigated how A. beshanzuensis seedlings responded to altitude change. Important findings The results showed that: (1) the seedling survival rate of A. beshanzuensis decreased by 50% due to the low altitude (500 m). The height, crown width, base diameter their corresponding growth rate of seedlings increased first and then decreased with the increase of altitude, and the seedlings grew best at 700–1 100 m altitude. (2) An increase of Simpson diversity had a significant positive effect on the base diameter growth rate of seedlings. (3) The growth of seedlings shows a significant positive correlation with air and soil temperature, and a significant negative correlation with air and soil moisture. Specifically, an increase in air and soil temperature within the range of 11–19 ℃ and a decrease of air and soil humidity within the range of 10%–25% promoted seedling growth. (4) Soil nutrient content, including ammonium nitrogen content and carbon-to-nitrogen ratio, had significant positive effects on the growth rates of seedling height, base diameter and crown width. In conclusion, altitude, fungal diversity, soil and air temperature, humidity, and soil nutrients are key environmental factors influencing the growth of A. beshanzuensis seedlings and should be considered critical factors in their ex situ conservation.

Aims To study the effects of different nitrogen (N) addition levels and NH4+-N to NO3–-N ratios on the photosynthetic and chlorophyll fluorescence parameters of Schima superba of the main subtropical tree species, so as to clarifying the short-term response mechanism of photosynthesis physiology and growth of S. superba to different N nutrient environments. Methods One-year-old seedlings of S. superba were cultured in sands with three N addition levels of 0.5 (low N), 1.0 (medium N), and 2.0 (high N) mmol L-1, and seven ratios of NH4+-N to NO3–-N being as 10:0, 8:2, 6:4, 5:5, 4:6, 2:8, 0:10. After 180 days of treatment with different nutrient solution, the photosynthetic characteristics, chlorophyll fluorescence parameters, chlorophyll content, biomass, and root-shoot ratio of S. superba seedlings were determined. Findings (1) Under the 21 experimental treatments with different N addition levels and NH4+-N to NO3–-N ratios, the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), chlorophyll (a+b) content, aboveground biomass, and total biomass of S. superba seedlings were the highest at the ratio of 4:6 under the high and medium N addition levels. However, these traits at the ratio of 10:0 were highest under the low N addition level. The underground biomass was the highest at the ratio of 4:6 under high N addition level, and the highest at the ratio of 6:4 under medium and low N addition levels. The root-shoot ratio was the highest under both the high and medium N addition levels at the ratio of 10:0, and under the low N addition level at the ratio of 6:4. (2) The Pn, Gs, Tr, chlorophyll (a+b) content, aboveground biomass, and total biomass of S. superba seedlings were the highest under the high N addition level at the ratios of 0:10, 8:2, 2:8, 6:4, 4:6, 5:5, except the ratio of 10:0. The water use efficiency, underground biomass, and root-shoot ratio were the highest under the low N addition level. (3) The fluorescence intensity of S. superba was more substantial under the high N addition level, and it significantly decreased at the ratio of 4:6 compared to other ratios under the low N addition level. The deviation of the OJIP curve at the ratio of 0:10 was the largest under the medium N addition level. The fluorescence values in the J-I segment at the ratio of 10:0, 0:10, 8:2, 2:8 under the low N addition level, the O-J segment and J-I segment at the ratio of 0:10, 8:2, 2:8, 4:6 under the medium N addition level, the J-I segment at the ratio of 0:10, 2:8, 6:4, and the I-P segment at the ratio of 0:10, 4:6 were increased under the high N addition level. There was no significant difference in the degree of deviation of the OJIP curve under three N addition levels that showed that the low N addition level (N stress) and the highly unbalanced ammonium to nitrate N ratio (10:0 and 0:10) cultivation environment did not cause stress to the growth of S. superba seedlings. Overall, the energy utilization of the PSII reaction center could be optimized, the photosynthetic capacity could be effectively improved, the aboveground growth and biomass accumulation could be promoted of S. superba seedlings in the cultivation environment with the proper N addition level and the appropriate ratio of NH4+-N to NO3–-N. Under the low N addition level, the S. superba can obtain more nutrients for its growth and development by enhancing the growth of underground roots. However, but the photosynthetic capacity was weak and the biomass accumulation was less.

Aims Rhizophora stylosa plays a crucial role in coastal plant ecosystems, contributing to environmental pollution remediation, coastline stabilization, and water quality purification and filtration. Cold stress poses a significant challenge to breeding efforts in the modern era, impeding the normal growth of R. stylosa seedlings and consequently impacting the regeneration and distribution patterns of R. stylosa communities. Growth regulators can improve plant stress resistance, and reveal the alleviating effect of growth regulators on photosynthetic characteristics of red sea olive under low temperature stress, could provide a scientific basis and theoretical guidance for the cultivation of R. stylosaseedlings and the prevention and control of low temperature. Methods In this study, the effects of growth regulators on R. stylosa seedlings were investigated by comparing the photosynthetic pigment (chlorophyll a, chlorophyll b, total chlorophyll, carotenoids) content and photosynthesis indexes (net photosynthetic rate, stomatal conductance, intercellular carbon dioxide concentration, transpiration rate) of R. stylosa seedlings under low temperature stress and rewarming. Important findings 1) Low temperature stress inhibited the photosynthetic process of R. stylosa seedlings, significantly reducing the photosynthetic pigment content and photosynthesis indexes of R. stylosa seedlings. 2) Adding appropriate concentrations of growth regulators alleviated the low temperature inhibition, promoted the rewarming effect, and improved the photosynthetic physiological process of R. stylosa. 3) Excessive concentrations of growth regulators (150 mg·L–1 NAA) led to the aggravation of low temperature stress in R. stylosa seedlings, so it was extremely important to screen appropriate species and concentrations. 4) Principal component analysis showed that biennial R. stylosa seedlings had stronger low temperature resistance than annual R. stylosa seedlings. 5) Combined with membership function analysis, 100 and 200 mg·L–1 GA3, 150 mg·L–1 IAA, 400 mg·L–1 6-BA, 200mg·L–1 GA3, and 50 mg·L–1 NAA had better effects under low temperature stress and rewarming.

Shrublands are widely distributed across various islands in China. As zonal vegetation in island ecosystems, they have important ecological effects, such as conserving soil and water, and protecting biodiversity. In this study, 95 sample plots were established on Haitan Island, Fujian, China, using a standard sampling method, and species composition, quantitative characteristics, and habitat information of the shrubs were recorded. Two-way indicator species analysis (TWINSPAN) and redundancy analysis (RDA) were employed for the numerical classification and ordination. The results showed that: 1) The typical shrublands in the study area can be classified into two categories, one dominated by native plants and the other by exotic species, with a total of 11 alliances and 23 associations. Among them, Eurya emarginata and Dodonaea viscosa shrublands were the predominant types. 2) The RDA ordination revealed significant differences in the factors affecting the distribution of the two types of shrublands. The main environmental factors influencing native plant communities were wind speed and average annual rainfall, followed by distance from the coastline, total soil soluble salts, and available nitrogen. However, the factors affecting the distribution of naturalized or invasive plant communities remain unclear and are likely influenced by multiple factors. This study provides original data on the shrublands of Haitan Island, filling the knowledge gap and offering critical foundational information for the compilation of the Vegegraphy of China and the creation of the national vegetation map.