As a greenhouse gas with a strong warming effect, nitrous oxide (N₂O) is also one of the main substances which destroy the atmospheric ozone layer, with 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, the related research methods, mechanisms and their influencing factors on N₂O emissions from terrestrial plants are summarized in this study. Existing studies have mainly determined the changes in 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. The N₂O emissions from plant 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, and analyzing their microbial community structure were applied to elucidate the microbial mechanisms underlying the flux differences of N₂O emissions from plants in different habitats. The metatranscriptome technology was used to determine total RNA in plant tissues and analyze the expression abundance changes of N₂O emission related genes under different environmental conditions. And isotope labeling technology was further used to track the nitrogen metabolism process of plants and reveal the mechanism of N₂O flux changes in plants. These results are of great significance for supplementing and improving N₂O prediction models such as “Ecosys” for global climate change, which 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 marshes. 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 height led to a decrease in aboveground biomass and an increase in belowground biomass. Compared to the 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 and dissolved organic carbon 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 damage 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 typhoon’s path, and Sanjiang, situated 6.5 km away, incurred severe damage, with the non-native populations of Laguncularia racemosa and Sonneratia apetala 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 only 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 six 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%-99.70% of individuals sustaining damage. Approximately 9.64% of individuals experienced trunk breakage or complete uprooting. 3) With the exception of the short Ceriops tagal community at Bodu, which had a maximum tree height of 2 m, mangrove communities with same species closer to the typhoon’s pathway exhibited more severe damage. Tree height, diameter at breast height, and crown size were significantly and positively correlated with damage severity; the taller the trees, the more severe the impact. Based on these damage assessments, 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 restoration efforts should consider species-specific wind resistance, and mixed-species planting strategies are recommended to enhance the stability and wind resilience of mangrove communities.

Aims Different levels of tidal flooding significantly affect mangrove sediment nutrients and stoichiometric characteristics, and plant fine root functional traits are keys strategies to cope with nutrient changes. However, there is a lack of in-depth understanding of 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 dynamics in exotic and native mangrove plants from the scale of fine root functional traits.

Methods The present 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 that: 1) The exotic species displayed higher nutrient acquisition requirements and more substantial metabolic capacity than the native species, and both species were subjected 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 reference for the environmental protection of the 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 (Triticum aestivum) and maize (Zea mays) 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 soil 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 The present 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 impacts of mycorrhizal types on root traits and rhizosphere microbial network characteristics.

Important findings (1) Specific root length, root nitrogen, and root phosphorus contents 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 was significantly higher than that of EcM tree species, while the relative abundance of Bacteroidota was significantly lower in AM tree species compared to EcM tree species. There was no significant difference in the biodiversity of rhizosphere microbial communities between different mycorrhizal type tree species. (3) The rhizosphere microbial networks of EcM tree species were more complex, and the negative bacterial cohesions of EcM tree species were 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 were identified as key factors predicting rhizosphere microbial network. 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 microbial network complexity.

Aims Studying the coordination and differences in the functional traits of leaves and fine roots can help better understand the ecological strategies of plants from a whole-plant perspective.

Methods In this study, we measured and analyzed the leaf and root traits of 20 woody species (10 trees and 10 shrubs) from the natural evergreen broadleaf forest in Wanmulin Nature Reserve, Fujian Province. We explored the coordination of root and leaf functional traits and differences in survival strategies between tree and understory shrub species in this subtropical natural evergreen broadleaf forest.

Important findings We found a strong correlation between the leaf nitrogen concentration and root nitrogen concentration, but this was observed only for similar traits of leaf and first-order root, irrespective of phylogeny. In the studied forest, there was a leaf economics spectrum and a leaf tissue density-leaf thickness variance axis, shaped by the measured leaf traits. For first-order root, we observed a cooperative axis (represented by the negative correlation between root diameter and specific root length) and a root economics spectrum (represented by the negative correlation between root nitrogen concentration and root tissue density). There was no significant correlation between root and leaf economic spectra. Significant differences were found between tree and shrub species only along the root collaboration axis, with trees having larger root diameters and shrubs having higher specific root lengths. In addition, the specific leaf area of shrub species was significantly larger than that of tree species. The results indicated that leaf and root traits are integrated into a complex relationship, with tree and shrub species adopting different aboveground and belowground strategies to adapt to the habitat heterogeneity in the studied area. Our results expand the understanding of the coordination between root and leaf traits at a local scale, and provide deeper insights into the ecological processes and species coexistence mechanisms within the community.

Aims Plant root exudates play important roles in the plant-soil-microbes interactions and feedbacks. 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 remain poorly understood on the Qingzang Plateau.

Methods In the study, based on a long-term grazing exclusion experiment on the Qinghai Lake Basin, we evaluated the root C, N and P exudate rates and their stoichiometric characteristics at the plant community and species level. Furthermore, the relationships between root exudate characteristics and plant community characteristics, as well as soil factors were also explored.

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 after long-term grazing exclusion, although 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 the species level, and had significant effects on their C:P and N:P simultaneously, with the greatest decline observed in the Leymus secalinus. (3) The root exudate ability of forb species was found to be greater than that of grass and sedge species, which was demonstrated by the observations that the root C and N exudate rate of the Aster altaicus was significantly higher than that of other species. (4) The root C and N exudate rate and N:P of exudation at the plant community level were significantly related to plant diversity, plant community composition, soil water content and soil N content. The further analysis revealed that the key factors affecting root C, N and P exudate rate were different, indicating 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 imposed 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 a first-class protected wild plant in China, with only three individuals remaining in mixed evergreen-deciduous broadleaf 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 air temperature and humidity, soil microorganisms, and soil physicochemical properties, we investigated how A. beshanzuensis seedlings responded to altitude change.

Important findings The results showed that: (1) the survival rate of A. beshanzuensis seedlings decreased by 50% due to the low altitude (500 m). The height, crown width, base diameter and their corresponding growth rates of seedlings increased first and then decreased with the increasing altitude; and the seedlings grew best at altitudes ranging from 700-1 100 m. (2) An increase in fungal Simpson diversity index had a significant positive effect on the growth rate of seedling base diameter. (3) The growth of seedlings showed 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 °C and a decrease in air and soil humidity within the range of 10%-25% promoted seedling growth. (4) The soil nutrients, such as ammonium nitrogen content, as well as soil 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 as critical factors in their ex situ conservation.

Aims This study aims to investigate the effects of varying nitrogen (N) addition levels and NH₄⁺-N to NO₃^--N ratios on the photosynthetic and chlorophyll fluorescence parameters of Schima superba, a dominant subtropical tree species. The objective is to clarify the short-term response mechanisms of photosynthesis physiology and growth of S. superba to different N nutrient environments.

Methods One-year-old seedlings of S. superba were rooted in sand potted sand culture nutrient solution with three N addition levels: 0.5 (low N), 1.0 (medium N), and 2.0 (high N) mmol·L^-1, and seven NH₄⁺-N to NO₃^--N ratios: 10:0, 8:2, 6:4, 5:5, 4:6, 2:8, 0:10. After 180 d of treatment, the photosynthetic characteristics, chlorophyll fluorescence parameters, chlorophyll content, biomass, and root-shoot ratio of S. superba seedlings were determined.

Important findings (1) Across the 21 experimental treatments with varying N addition levels and NH₄⁺-N to NO₃^--N ratios, the net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), chlorophyll (a + b) content, aboveground biomass, and total biomass of S. superba seedlings were highest at the 4:6 ratio under high and medium N addition levels. However, these traits were highest at the 10:0 ratio under the low N addition level. The underground biomass peaked at the 4:6 ratio under high N addition, and at the 6:4 ratio under medium and low N addition levels. The root-shoot ratio was highest at the 10:0 ratio under high and medium N addition levels and at 6:4 ratio under low N addition. (2) The P_n, G_s, T_r, chlorophyll (a + b) content, aboveground biomass, and total biomass of S. superba seedlings were the highest under the high N addition level across all ratios except 10:0. The water use efficiency, underground biomass, and root-shoot ratio were highest under the low N addition level. (3) The chlorophyll fluorescence intensity was more pronounced under the high N addition level and significantly decreased at 4:6 ratio compared to other ratios under low N addition. The deviation of the OJIP curve was greatest at 0:10 ratio under medium N addition level. The fluorescence values in the J-I segment at ratios of 10:0, 0:10, 8:2, 2:8 under low N addition level, the O-J and J-I segments at ratios of 0:10, 8:2, 2:8, 4:6 under medium N addition, the J-I segment at ratios of 0:10, 2:8, 6:4, and the I-P segment at ratios of 0:10 and 4:6 were increased under high N addition. There was no significant difference in the deviation of the OJIP curve across three N addition levels, indicating that low N addition (N stress) and highly unbalanced ammonium to nitrate N ratios (10:0 and 0:10) did not stress the growth of S. superba seedlings. Overall, the energy utilization of the PSII reaction center could be optimized, photosynthetic capacity effectively improved, and aboveground growth and biomass accumulation promoted in S. superba seedlings under appropriate N addition levels and NH₄⁺-N to NO₃^--N ratios. Under low N addition, the S. superba enhanced underground root growth to obtain more nutrients for development, although the photosynthetic capacity was weaker and the biomass accumulation was lower.

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. Revealing the alleviating effect of growth regulators on photosynthetic characteristics of R. stylosa under low temperature stress could provide a scientific basis and theoretical guidance for the cultivation, the low temperature prevention and control of R. stylosa.

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 photosynthetic parameters (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 by significantly declining the photosynthetic pigment content and photosynthetic parameters. 2) Adding appropriate concentrations of growth regulators alleviated the low temperature inhibition, promoted the rewarming effect, and improved the photosynthetic 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, which highlighted the extreme importance 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) Combining with membership function analysis, 100 and 200 mg·L^-1 GA₃, 150 mg·L^-1 IAA, 400 mg·L^-1 6-BA, and 50 mg·L^-1 NAA had better effects on R. stylosa seedlings under low temperature stress and rewarming.

Shrublands are widely distributed across various islands in China. They have important ecological effects, such as conserving soil and water and protecting biodiversity. In this study, we established 95 sample plots on Haitan Island, Fujian, China, using a standard sampling method. Species composition, quantitative characteristics, and habitat information of the shrublands were recorded. Two-way indicator species analysis (TWINSPAN) and redundancy analysis (RDA) were employed for the numerical classification and ordination, respectively. 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, including 11 alliances and 23 associations in total. Among them, Eurya emarginata and Dodonaea viscosa shrublands were the predominant alliances. 2) The RDA ordination revealed that the shrublands dominated by native species and by exotic species were different in the factors affecting the distribution. The native plant communities were mainly influenced by wind speed and mean annual precipitation, followed by distance from the coastline, total soil soluble salts content, and available nitrogen content. However, the exotic plant communities were likely influenced by multiple factors but the main drivers remained unclear. This study provides original data on the shrublands of Haitan Island, filling the knowledge gap in the shrubland information in this area and offering important foundational information for the compilation of the Vegegraphy of China and the creation of the national vegetation map.