Aims Benthic microalgae are one of the primary producers in coastal wetlands, providing basic energy and material to the food web of coastal wetlands and playing an important role in maintaining the stability of coastal wetland ecosystems. Previous studies have focused on the effects of environmental factors, vascular plants and herbivores on benthic microalgae, neglecting the trophic cascade effects of predators.
Methods We investigated the trophic cascade effects of waterbirds on benthic microalgae in a manipulative field experiment in a coastal wetland in the Chang Jiang (Yangtze) estuary, where we measured the biomass of benthic microalgae monthly and their species composition quarterly for a year.
Important findings Results showed that: (1) benthic microalgal biomass was significantly decreased in waterbird exclusion treatments. In waterbird exclusion treatments, although the lack of direct consumption by waterbirds facilitated benthic microalgae, increases in the abundance of crabs feeding on microalgae suppressed benthic microalgae more strongly. (2) Crab exclusion treatments (simulating intense predation by waterbirds) also significantly reduced benthic microalgal biomass. In crab exclusion treatments, the abundance of snail feeding on microalgae increased substantially. (3) Waterbird and crab exclusion treatments both significantly reduced the abundance of the dominant microalgal taxa, diatoms, and increased the diversity of benthic microalgal communities. This study demonstrates that waterbirds in coastal wetlands can exert strong top-down effects on benthic microalgal communities through multiple direct or indirect processes, and enriches our understanding of the mechanisms controlling microalgal communities in coastal wetlands.

Aims Biodiversity plays an important role in regulating ecosystem functioning. Fire is an important ecological factor in forest ecosystems, and can significantly affects both above- and below-ground biodiversity, as well as ecosystem functions. However, how biodiversity affects ecosystem multifunctionality (EMF) after prescribed burning, such as forest biomass accumulation and nutrient availability, is still less understood.
Methods In this study, we investigated Pinus koraiensis plantations in Hongqi Forestry Farm, Hegang, Heilongjiang, four years after the prescribed burning was conducted in 2018 (when the forest environment has stabilized). We used structural equation modeling to assess the relationships of understory plant diversity (species and functional diversity, efficiency and quantity traits) and soil microbial diversity (fungi and bacteria) with EMF.
Important findings We found that prescribed burning increased both understory plant diversity and EMF. Out of various above and belowground diversity metrics, Trait_quantity (i.e., total leaf nitrogen per unit area) and functional diversity (i.e., functional dispersion (FDis) based on leaf dry matter content) were significantly and positively correlated with EMF, while the effect of belowground microbial diversity on EMF was not significant. The prescribed burning explained the highest proportion of variations in EMF (33.7%), followed by Trait_quantity (27.5%) and functional diversity (13.9%). The results suggest that in P. koraiensis plantations, enhancing nutrient accumulation and trait diversity in the understory layer is an effective strategy to improve EMF after prescribed burning. Meanwhile, in forest management in the context of global change, prescribed burning is not only an effective way to reduce forest fire risks, but may also play a positive role in maintaining understory biodiversity and EMF.

Aims As one of the key components of litter, cellulose decomposition plays an important role in the carbon cycle of terrestrial ecosystems. The objective of this study was to investigate the global patterns of cellulose decomposition rates of plant litters and the associated influential factors.
Methods We compiled a dataset from existing studies that reported the litter cellulose decomposition constant (i.e., k value, a measure of the decomposition rate). Using the first-order exponential kinetic model, we calculated the k values for litter cellulose decomposition. Then, we explored the distribution patterns of k across climatic zones, ecosystem types and leaf morphological types, and determined the extent to which these patterns were influenced by climate, terrain, soil properties, and litter substrate quality.
Important findings The decomposition rates of litter cellulose shifted pronouncedly with climatic zones and leaf morphological types, with climatic zone being highest in tropical (0.086), intermediate in subtropical (0.069) and lowest in temperate (0.048) regions, and with leaf morphology being higher in broadleaf than coniferous litters. Cellulose decomposition rates decreased with increase in initial carbon nitrogen ratio and lignin cellulose ratio, while increased with increasing mean annual temperature. These results suggest that litter substrate quality and climate play significant role for influencing litter cellulose decomposition. This study enhances our understanding of the litter cellulose decomposition, and helps to optimize plant litter turnover and ecosystem carbon cycle models.

Aims Species richness patterns along altitudinal gradients in mountain ecosystems have been a central theme in ecological research. While past studies often investigated species richness on individual mountains, regional-scale analyses have typically relied on samples collected along roadsides or foothills, potentially neglecting the crucial aspect of vertical zonation in mountain biodiversity.
Methods Eight mountains along the Rongbu River with varying base altitudes (ranging from 3 785 m to 5 155 m) were selected for the study. Employing transect and quadrat methods, species richness was comprehensively surveyed across the vertical zones of these mountains.
Important findings (1) A total of 81 plant species were recorded in this survey, including species such as Elymus nutans, Poa tibetica, Arenaria bryophylla, and Astragalus strictus, all of which were documented across all eight mountains in the basin. (2) On a watershed scale, species richness per unit area (1 m²) followed a unimodal curve with respect to altitude. However, on individual mountain ranges, the distribution patterns of species richness per unit area along the altitude gradient varied, showing U-shaped distributions, positive correlations, or no significant relationships. (3) Overall, the cumulative species richness in the lower parts of the mountains was lower than in the middle and upper parts. Additionally, the species richness per unit area was higher on the shady slopes of the mountains compared to the sunny slopes. This study revealed a significant disparity between species richness in the base zone of the mountains and the overall species richness of the entire mountain. This finding indicates that plant surveys conducted solely along roadsides or at the mountain base significantly underestimate the species richness of the entire mountain by 13.5% to 54.8%. Therefore, it is imperative to pay particular attention to the distribution patterns of species richness across mountain spatial scales and their key influencing factors in mountain ecosystems, especially on the Qingzang Plateau.

Aims The Loess Plateau stands as one of China’s most susceptible regions to meteorological drought, a vulnerability exacerbated in recent years by the backdrop of climate warming. As meteorological droughts show a rising trend, investigating the capacity of vegetation to withstand and recover from drought stress becomes paramount. Understanding the resilience and resistance of vegetation’s photosynthetic physiological processes to drought is crucial for comprehending how vegetation responds to environmental shifts and for forecasting the future trajectory of vegetation development in the area.
Methods Utilizing the solar-induced chlorophyll fluorescence Global SIF dataset based on OCO-2 (GOSIF) products alongside temperature and standardized precipitation evapotranspiration index (SPEI) data, this study aims to investigate the impact of drought on the spatial and temporal stability of photosynthesis across various vegetation types and climate zones on the Loess Plateau employing the multiple linear autoregressive model.
Important findings The study revealed a linear relationship between vegetation photosynthetic resilience and the severity of drought experienced on the Loess Plateau. Vegetation photosynthetic resilience weakens in the order of mild, moderate, and severe drought. The relationship between vegetation photosynthetic resistance and drought severity exhibited a nonlinear pattern, with resistance declining from severe to mild and moderate drought. Vegetation photosynthesis on the Loess Plateau displayed insensitivity to temperature variations. Comparison across climatic zones highlighted that in arid regions, vegetation photosynthetic resilience declined with escalating drought severity, whereas semi-arid zones demonstrated relatively stable resilience. In semi-humid regions, vegetation photosynthetic resilience decreased in the order of severe, mild, and moderate droughts. Among vegetation types, forests demonstrated the highest levels of both resilience and resistance. These findings contribute significantly to our understanding of the regional vegetation stability in the Loess Plateau under the background of climate changes, thereby guiding the ecological restoration and management efforts in the region.

Aims Exploring the variations of non-structural carbohydrates (NSC) among tree species and organs, as well as the differences in NSC among tree functional groups, is an important topic for a deeper understanding of the carbon allocation characteristics of plants.
Methods 32 tree species were selected from a typical conifer-broadleaf mixed forest in Laoyeling, Heilongjiang Province, and nine organs were collected to systematically analyze the changes in NSC concentration with organs and wood porosity.
Important findings (1) The effect of organs on concentrations of NSC and its components was greater than that of tree species. Among different organs, there was a gradual decrease in NSC from carbon source organs (leaf) to storage organs (bark and coarse root) and slow turnover organs (trunk wood); the sugar starch ratio was highest in fast turnover organs (leaf and fine root). (2) There were no significant correlations of the concentration(s) of NSC or its components between organs for most tree species; and there were no significant correlations between the concentrations of soluble sugar and starch in most organs. (3) Wood porosity had a significant effect on the concentrations of NSC and its components. From non-porous wood, diffuse-porous wood to ring-porous wood species, the soluble sugar concentration in bark gradually decreased; while the starch concentration in all organs except heartwood, as well as the total NSC concentration in sapwood and belowground organs, gradually increased. Transporting a greater proportion of NSC to non-photosynthetic organs, and thus keeping low concentrations of NSC in leaves, is an important strategy to ensure adequate carbon supply to the whole tree. These results indicate the obvious functional differentiation of NSC storage in different organs of typical temperate forest tree species, and the significant effect of wood porosity on the concentrations of NSC and its components in multi-organs.

Aims Nitrogen is a key nutrient element for maintaining species diversity in plant communities. In nitrogen-limited desert ecosystems, the impact of interspecific interactions within sand-fixed plant communities on nitrogen uptake rates and distribution among different functional groups of plants remains unclear.
Methods A field experiment was conducted in the Mau Us Sandy Land, northern China, with two treatments: removal of Artemisia ordosica and a control that retained A. ordosica. Nitrogen uptake rate and proportion of nitrate nitrogen, ammonium nitrogen, and glycine by three associated functional groups of herbaceous plants (annual herbaceous, perennial grasses, and perennial forbs) and the overall herbaceous community, were measured using ¹⁵N isotope labeling. Environmental factors, such as soil ammonium nitrogen, nitrate nitrogen, total nitrogen, soluble organic nitrogen content, soil moisture, and plot light transmittance were also determined. Additionally, the relationships between nitrogen uptake rate, proportion and environmental factors for each functional group and herbaceous community were analyzed.
Important findings Inorganic nitrogen and micromolecular organic nitrogen were effective nitrogen sources for herbaceous plants in A. ordosica community. The preference of herbaceous plants for different forms of nitrogen followed the order: nitrate nitrogen, ammonium nitrogen, and micromolecule organic nitrogen. After the removal of A. ordosica, the nitrogen uptake rate of annual herbaceous, perennial grasses, and the overall herbaceous community increased by 48.32%, 129.77%, and 55.53%, respectively, with perennial grasses showing a 10.65% increase in the proportion of nitrate nitrogen uptake. Artemisia ordosica affected the nitrogen uptake absorption mode of herbaceous plants by altering the microenvironment under the plants, particularly by reducing plot light transmittance and soil nitrate nitrogen content. Nitrogen uptake rate and proportion among different functional groups of herbaceous plants were influenced by various environmental factors, among which perennial grasses demonstrating flexible nitrogen source plasticity and higher nitrogen use efficiency. The study showed that the differentiated nitrogen acquisition strategies of herbaceous plants may be a crucial mechanism underlying that herbaceous plants in A. ordosica community coped with interspecific nitrogen competition and resource scarcity, thereby enhancing community stability and resilience. Perennial grasses, with flexible nitrogen source utilization and efficient absorption capabilities, may gradually become the dominant functional group as community succession. These findings may enhance the understanding of nutrient competition and species coexistence mechanisms in the typical sand-fixed community, which would provide scientific evidence for vegetation restoration and management in desertification areas.

Aims Studying the adaptation mechanisms of species in the context of climate change has been a concern in plant ecology. Investigating the effect of leaf nitrogen allocation of sand-fixing species on the photosynthetic capacity of plants help us to understand their adaptive capacity under changing climate.
Methods In this study, we selected two common sand-fixing species, Artemisia ordosica and Leymus secalinus, in Yanchi, Northwest China. The effects of leaf nitrogen allocation on the maximum net photosynthetic rate (A_max) of the two species were analyzed using in situ measurements of photosynthetic light- and CO₂-response curves, leaf traits, and enviromental variables, from May to October, 2021.
Important findings The results showed that the mean leaf nitrogen content per unit mass (N_mass) was about 0.02 g·g^-1 for both species. The mean values of A_max and the distribution proportion of leaf nitrogen in photosynthetic system (P_p) in A. ordosica were 22.44 μmol·m^-2·s^-1 and 42.9%, respectively. The mean values of A_max and P_p in L. secalinus were 11.99 μmol·m^-2·s^-1 and 27.5%, respectively, which were lower than those of A. ordosica. During the water deficit period in the middle growing season, A_max and P_p decreased in A. ordosica and remained relatively unchanged in L. secalinus. Comparing with L. secalinus, A_max of A. ordosica was more affected by leaf nitrogen distribution. The main controlling factors of A_max were P_p and leaf nitrogen distribution in carboxylation system (P_c) in A. ordosica and L. secalinus, respectively. In the middle growing season with low soil moisture, the N_mass decreased in both species. Photosynthetic nitrogen use efficiency (PNUE) decreased in A. ordosica due to its greater sensitivity of the nitrogen distribution ratio to soil moisture and more nitrogen investment in non-photosynthetic organisms and thus higher stress resistance, and remained relatively stable in L. secalinus. The A_max in A. ordosica was greater than L. secalinus during the observation period due to its relatively higher P_p. The differences between two sand-fixing species in variations in leaf nitrogen allocation and leaf photosynthetic capacity indicate that the research area might be dominated by shrub species A. ordosica under changing climate.

Aims Many factors can influence the growth of plants and their adaptability to the growing environment, among which plant growth promoting rhizobacteria (PGPR) may play a key role. Thus, the aim of this study is to explore the rhizosphere microbial resources with high aluminum tolerance and investigate their role in alleviating the aluminum toxicity to sugarcane (Saccharum officinarum).
Methods We isolated and screened the dominant strains of aluminum-tolerant PGPR from the rhizosphere soil of sugarcane and studied their effects on sugarcane growth. By measuring the aluminum accumulation, physiological metabolism and expression changes of aluminum-tolerant genes in the aboveground and underground parts of sugarcane under aluminum stress, we compared the aluminum tolerance of sugarcane inoculated with aluminum-tolerant bacteria and those without aluminum-tolerant bacteria.
Important findings Three strains of dominant sugarcane rhizosphere bacteria, Burkholderia A1, A23 and X6, have strong acid tolerance (pH 3.8) and aluminum tolerance (4 or 5 mmol·L^-1). All the three strains have the ability to dissolve phosphorus, secrete exopolysaccharides (EPS), fix nitrogen and remove Al³⁺. X6 can produce low level of indole-3-acetic acid (IAA), A1 and X6 can secrete a certain amount of iron carriers, and A23 and X6 have 1-aminocyclopropane-l-carboxylic acid (ACC) deaminase activity. The combined bacteria of A1, A23 and X6 improved the plant height, leaf area and fresh mass of aboveground part of sugarcane. Although the bacteria combinations showed no obvious effect on the contents of nitrogen, phosphorus and potassium in aboveground and underground parts of plant, but significantly increased the aluminum content in aboveground part of sugarcane under 0.5 and 1 mmol·L^-1 aluminum stress and significantly reduced the aluminum content in underground part of sugarcane under 1 mmol·L^-1 aluminum stress, and the overall performance was reducing the total aluminum content in sugarcane. The inoculation treatment showed no significant effect on the activities of superoxide dismutase (SOD) and peroxidase (POD), and the contents of proline (Pro) and soluble protein (SP), but significantly reduced the malondialdehyde (MDA) content and significantly increased the catalase (CAT) activity in root tips under aluminum stress, and significantly increased the expression of MAPK and GST genes in root tips and PEPC gene in leaves of sugarcane. These results showed that Al-tolerant Burkholderia strains had significant effects on sugarcane growth, aluminum absorption and accumulation, plant antioxidant defense ability and aluminum-tolerant gene expression, which together improved the aluminum tolerance of sugarcane.

Aims The Rhododendron as a high ornamental value genus has a great potential for resources development and utilization in China, which provided the most abundant rhododendron resources in the world. The risk of drought stress is rapidly increasing in the context of global warming, but the effects of water stress on growth and physiological and ecological indexes of rhododendrons are still lacking. In this paper, the height and ground diameter growth increment of R. delavayi under the drought stress were studied, and the numerical relationship of the growth increment response to the physiological indicators were established to provide a theoretical basis for the future protection and management of rhododendron.
Methods Pots experiment with 2 years old seedlings of R. delavayi were carried out from March 11th to October 15th, 2022. The water stress gradient was set as 15%, 25%, 35%, 50%, 70%, 90% of the field water holding capacity respectively. The height and ground diameter of each R. delavayi were measured in early and late of March, April, May and in the middle of June, July and October. The physiological index of osmotic system (proline (Pro), soluble sugar (Ss), soluble protein (Sp) contents), antioxidant system (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) activity, malondialdehyde (MDA) content) and photosynthesis system (net photosynthetic rate (P_n), stomatal conductance (g_s), intercellular CO₂ concentration (C_i), transpiration rate (T_r)) were measured in June, July, and August by randomly selecting five seedlings in each treatment.
Important findings 1) The equations of rhododendron height and ground diameter response to the day of year (DOY) were established under each drought gradient with the fitting accuracy between 0.94-0.99. The mortality was the highest under the treatment of 15% of the field water holding capacity. 2) The equations of the relative cumulative tree height response to the soil water content were established with the unimodal curve variation. While that of ground diameter response to the soil water content shows the U shape variation with the increase of soil water content before DOY 161, the linear pattern with that between DOY 161-201, and the unimodal curve variation after DOY 201. 3) With the increase of soil water content, SOD activity, CAT activity, POD activity, P_n, g_s, T_r and Pro content increased firstly and then decreased, the SOD activity, CAT activity, POD activity and Pro content reach the maximum value at field water holding capacity of 20%-30%, P_n, g_s and T_r reach that value at 60%-80%; MDA content gradually decreases; C_i, Ss and Sp contents decrease first and then increase, reaching the minimum value at field water holding capacity of 60%-80%. 4) Based on the regression analysis of the daily increment of ground diameter and the physiological indexes, the significant regression relationship index includes MDA content, P_n, g_s, T_r and Ss content. Except the relationship of daily ground diameter increment response to the MAD was quadratic function, the relationship of that to the other physiological indexes were power equation, the fitting accuracy of the relationships was T_r > P_n > MDA content > g_s > Ss content. The cumulative growth (diameter increment) of R. delavayi was the most when the soil content was 68% of the field water holding capacity. With the soil water varying, the growth was mainly promoted by T_r, P_n and g_s, but inhibited by Ss content. The MDA content promoted the growth when it was lower than 33.53 nmol∙g^-1, but it turned inhibited the growth when it was higher than 33.53 nmol·g^-1. This has further explained the physiological mechanism of R. delavayi seedlings growth.

Aims The subalpine meadow of Wuyi Mountain is the highest meadows in the subtropical region of southeastern China. Identifying the variation characteristics of soil carbon flux components, and exploring their relationships with environmental factors and temperature sensitivity (Q₁₀) are of great significance for accurately estimating regional soil carbon balance and improving the knowledge about carbon flux dynamics in subalpine meadows.
Methods From May 2020 to April 2021, the LI-8100 CO₂ flux analyzer was utilized to systematically monitor the soil respiration rate (RS) in the meadow located at the summit of Wuyi Mountain. Additionally, the root exclusion method was applied to distinguish between the autotrophic respiration rate (RA) and heterotrophic respiration rate (RH).
Important findings (1) The dynamics of RS, RA and RH followed bimodal patterns, with consistently higher rates record from May to October compared to other months. Notably, the RA exhibited greater variability than RH throughout the year, accounting for 45% of RS. (2) A multi-model comparative analysis suggested that the temperature (T) exhibited an exponential correlation with soil respiration rate and its components in the subalpine meadow soil of Wuyi Mountain. The ranking of Q₁₀ values for soil respiration rate and its components was RA (Q₁₀ = 1.96) > RS (Q₁₀ = 1.94) > RH (Q₁₀ = 1.67). Although soil moisture (W) had a certain effect on RS, there was no significant relationship between RA and RH. The two-factor models including both T and W provided a better fit for RS than single-factor models, jointly explaining 48% of the variation in RS. In conclusion, soil respiration was primarily driven by heterotrophic respiration, while autotrophic respiration was more sensitive to temperature. Additionally, soil temperature and humidity were crucial environmental factors influencing soil respiration in the subalpine meadow of Wuyi Mountain, with soil respiration inhibited by low temperatures and high humidity. This study contributes to enhancing our understanding of the seasonal dynamics and influencing factors of soil respiration and its components in the subalpine meadow, providing valuable insights for regional soil carbon flux and carbon cycle research.