Alien plant invasions pose a significant threat to global ecological security. Various factors, including the ecological tolerance of alien plants and their interactions with biotic and abiotic elements such as rainfall, temperature, and soil nutrients, influence the dynamics of plant invasions. The interaction between plants and various micro-organisms plays an important role in regulating plant growth, development, and interspecific competition. Previous studies indicate that the interactions between native plants and different groups of soil microorganisms affect plant invasion through several pathways: 1) Pathogenic microorganisms may have more suppressive effects on native plants, facilitating the invasion of alien plants. 2) Symbiotic microorganisms can help native plants resist alien plant invasion, but disrupting these mutualistic associations may accelerate invasion. 3) Additionally, saprophytic microbiota may promote plant invasions by increasing the rate of nutrient cycling and facilitating these alien plants with high nutrient utilization efficiency. Compared to single-species invasions, multispecies invasions can increase invasive capacity through shared pathogen pressures, forming symbioses, and utilizing heterogeneous nutrients from saprophytic microorganisms. This interspecific synergistic effect can disrupt the balance between native plants and soil microbes. Furthermore, global changes may promote alien plant invasions through the detrimental effects of soil microbes on native plants. This review examines the impact of interactions between native plants and soil microbes on plant invasions and outlines directions for future research.

Soil seed banks (SSBs) represent potential resource reserves for future species diversity in the terrestrial ecosystem, and play an important role in the storage of species and genetic diversity. Global changes and human activities have important impacts on SSBs, while current studies mainly focus on the response of SSBs to small scales (region) or single influencing factor. Comprehensive understanding on the responses of SSBs to global changes and human activities was limited by small scale (region) or lack of the multi-factor coupling. In this review, a total of 7 606 related articles were retrieved from databases of CNKI and Web of Science, ranging from 1980 to 9th February 2022, and bibliometrics were conducted to summarize the study progress and to guide the future study on the SSBs. The research outcomes of SSBs suggest that global changes (temperature, precipitation change and atmospheric nitrogen deposition) and human activities (soil use change, fenced, grazing and ecology restoration) have direct or indirect effects on the composition and size (density) of SSBs. The roles of SSBs in restoring degraded ecosystems remain unresolved. Four major research directions in SSBs still need to be paid more attention: (1) Standardize the sampling methods of SSBs, including sampling time, sampling size, and sampling depth, and establish a complete research methods systems; (2) Establish long-term field positioning observation and experimental station to study the change characteristics of SSBs on time and space scales; (3) Research on multi-factor interaction effects under global changes and human activities; (4) Based on the observation of long-term data, developing the models to predict and quantify the future restoration potential of SSBs to plant communities and ecosystems in the context of multiple factors.

Aims Plant secondary metabolites (PSMs) are closely related to plant growth, development, and the ability to resist biotic and abiotic stresses, playing a crucial role in plant adaptation strategies to the environment. However, the response of leaf PSMs to long-term nitrogen (N) addition in forest ecosystems remains insufficiently studied, which largely limits our ability to grasp the changes in tree resistance and forest ecosystem stability under N deposition.

Methods Our study is based on an 12-year N addition experiment platform, focusing on four dominant plant species in the temperate deciduous forest of Donglingshan: including the plants Betula platyphylla and Corylus mandshurica in the birch forest and Quercus mongolica and Deutzia grandiflora in the oak forest. We investigated responses of soil physicochemical properties in two forest types, leaf phenolic PSMs (i.e., total phenolic, flavonoid, and tannin) contents of four plant species, and tree growth to long-term N addition.

Important findings The results showed that soil water and nutrient contents of birch forest were higher than those of oak forest. N addition significantly decreased soil pH in birch forest and soil water content in oak forest, and increased soil total phosphorus content in oak forest. Overall, the responses of dominant plant species to N addition exhibited contrasting trends, with leaf PSMs showing an increasing trend in the birch forest and a decreasing trend in the oak forest, particularly under high N addition treatments. The leaf phenolic PSMs contents of the four plant species exhibited a trade-off with leaf nutrient contents which was regulated by soil water and nutrient availability. Additionally, after N addition, B. platyphylla showed a decreasing trend in relative growth rate, whereas Q. mongolica showed an increasing trend. These results suggested different nutrient allocation and growth-defense balance strategies among different forest types under N deposition. Compared to the birch forest, the oak forest, which was relatively poor in water and nutrients, was likely to experience vulnerability-related issues (e.g. increased levels of insect herbivory and higher abundance of pathogens) earlier under the influence of long-term high N deposition.

Aims Litterfall plays a pivotal role in nutrient cycling in forest ecosystems. The yield and composition of litterfall typically exhibit seasonal variations in subtropical evergreen broadleaf forests, however, the mechanisms underlying the patterns are largely unknown.

Methods Evergreen broadleaf forests were taken as the research object in the Castanopsis kawakamii nature reserve in Sanming, Fujian Province. The litterfall yield and environmental factors were monitored every month during 2018-2022.

Important findings Our results showed that 1) The annual litterfall yield ranged from 4 949.17 to 6 873.45 kg·hm^-2·a^-1, with leaves accounting for 66.63% of the litterfall. The yield of litterfall components ranked as leaves (66.63%) > miscellany (16.07%) > branches (12.78%) > fruit (4.64%). 2) The seasonal dynamics of total litterfall yield exhibited a trimodal pattern during the year, with the first peak observed from March to May, the second peak observed from July to August, and the third peak found from September to December. Leaf litterfall and fruit litterfall displayed bimodal patterns during the year, with leaf litterfall peaking at April and August, and fruit litterfall peaking at March and December, respectively. The seasonal dynamics of branch litterfall and debris litterfall showed trimodal patterns, with branch litterfall peaking in May, August, and December. Debris litterfall peaked in April, August, and December. 3) Random forest models indicated that the primary environmental factors affecting the seasonal dynamics of litterfall were monthly precipitation, air temperature, and daytime rain duration. The litterfall yield decreased with increasing daytime rain duration and soil moisture during March to May, while it increased with increasing soil moisture and daytime photosynthetically active radiation from July to August. Overall, precipitation and the timing of rainfall events play direct and indirect roles in influencing the litterfall yield and seasonal dynamics in the evergreen broadleaf forests in the mid-subtropical region.

Aims Biodiversity is an important driver in the formation and maintenance of ecosystem functions, but the underlying ecological mechanisms behind it are still highly controversial. The niche complementarity and mass-ratio effects are two main hypotheses that explain the relationship between biodiversity and ecosystem function. However, it is still unclear whether the relative contributions of niche complementarity and mass-ratio effects to ecosystem function in temperate forests change with succession.

Methods Based on the observations from three forest plots in Changbai Mountains, including a secondary Populus davidiana- Betula platyphylla forest (early successional stage), a secondary needleleaf-broadleaf mixed forest (middle successional stage), and a primary Tilia amurensis- Pinus koraiensisforest (late successional stage), this study estimated how biodiversity-ecosystem function relationships change with forest succession. Aboveground biomass and productivity were used as two indicators reflecting ecosystem function. Species richness and species composition were used to represent the niche complementarity and mass-ratio effects, respectively. The relative contributions of niche complementarity and mass-ratio effects to ecosystem function were tested using structural equation modeling.

Important findings The results showed that the relationships between species richness and ecosystem functions change with forest succession. The complementary effect of species richness was not significant in the early stages of succession, but gradually increased in the middle and late stages. Compared with species richness, species composition significantly affected ecosystem functions at all stages of forest succession, indicating that the mass-ratio effect plays an important role during the whole forest succession process. In addition, the results showed that aboveground biomass is also an important factor affecting forest productivity. This study elucidates how the relationships between biodiversity and ecosystem functions change with succession in temperate forests, which provide a scientific support for the ecological restoration and biodiversity protection of secondary forests in northeast China.

Aims Our aim is to explore density dependence across various life stages trees in temperate forests and determine the varying importance of density dependence at different life stages. We seek to provide a theoretical foundation for species coexistence at a local scale in these forest systems.

Methods Utilizing tree census data and the dynamic monitoring data from 451 seedling quadrats in a 21.12 hm² plot of coniferous and broadleaf mixed forest in Jiaohe, Jilin over three consecutive years (2016-2018), the effects of density dependence on different life stages were analyzed at community and species levels by four models: generalized linear mixed model, generalized linear mixed model incorporating the interaction between individual size and conspecific (heterospecific) neighbor variables, generalized linear mixed model incorporating conspecific neighbor variables and heterospecific neighbor variables as random effects, specialized generalized linear mixed model with sole incorporation of conspecific (heterospecific) neighbor variables as random effects.

Important findings At the community level, conspecific neighbors significantly affected the survival rate across all life stages. Conspecific adult tree neighbors exhibited a significant negative impact on seedling survival rate, while conspecific seedling neighbors had a positive effect on seedling survival rate. The survival of both saplings and adult tree stages was significantly and negatively affected by conspecific neighbors. The Conspecific Negative Density Dependence (CNDD) attenuated in response to life stages. Heterospecific neighbor effects varied in accordance with life stage and neighbor radius, without a well-defined trend. At the species level, the neighborhood effect differed significantly among species solely at the adult tree stage, and neither the conspecific neighborhood effect nor the heterospecific neighborhood effect differed significantly among species at other life stages. Negative density constraints existed in all life stages of this temperate forest, while CNDD decreased with life stage. The effect of heterospecific negative density constraints on the survival rate of individuals in different life stages was influenced by the scale of the neighborhood, without any apparent trend. As a result of the “herd immunity effect” or suitable habitat, the survival of individual seedlings was positively affected by conspecific seedling neighbors. Neighborhood effects varied among species depending on their life history strategies, life types and species richness. The results of this study suggest that the mechanisms affecting the coexistence of species in forest communities at the local scale require comprehensive analyses that incorporate multiple species and life stages.

Aims Vegetative growth and reproductive processes of plants are subject to selective pressure from interspecific competition. Clonal plants exhibit clonal modularity, and dioecious plants have varying reproductive costs for males and females. These may result in inconsistent responses of physiological activities to interspecific competition in dioecious clonal plants, potentially showing gender differences. Assessing the response of physiological activities of dioecious clonal plants to interspecific competition is significant for understanding the adaptability and population dynamics of plants.

Methods We focused on the dioecious clonal plant Acer barbinerve and utilized the Hegyi index to quantify interspecific competition intensity. At the level of genets, we examined the response of reproductive processes and vegetative growth of the dioecious clonal plant to changes in interspecific competition intensity. During the flowering and fruiting periods, we randomly selected a certain number of male and female genets of A. barbinerve and measured flower and fruit numbers, biomass, and leaf area. Additionally, we used linear regression analysis to explore the relationship between these variables and interspecific competition intensity. The aim of this study is to investigate the differences in responses of sexual reproduction, clonal reproduction, and growth to interspecific competition intensity between male and female genets.

Important findings Interspecific competition inhibited clonal reproduction and vegetative growth of both female and male genets of A. barbinerve, but the inhibition on vegetative growth of females was stronger. Sexual reproduction of females was not influenced by interspecific competition, whereas that of males was significantly inhibited during the flowering period in 2023. These results suggest that, while interspecific competition intensity was similar in females and male, they displayed distinct responses to interspecific competition, particularly in their growth and sexual reproductive processes.

Aims Seed traits are of great significance for clarifying plant population reproduction and regeneration strategies. Exploring responses of Artemisia ordosica seed traits to nitrogen and water addition can improve our understanding of desert plant community succession in the context of global change.

Methods The study was conducted based on a 8-year field water and nitrogen control experiment (2015-2022) in Mu Us Desert. A full factor interaction experiment of ambient precipitation, 20% water increase, 40% water increase and 0, 20, 60 kg N·hm⁻²·a⁻¹ were carried out to determine the morphological, physiological, chemical and germination traits of A. ordosica seed. Seed germination traits under each treatment at two temperatures (25 °C/15 °C and 20 °C /10 °C) were explored by using the petri dish germination experiment and calculating the germination indexes by observing the number of seedling emergence.

Important findings (1) Nitrogen and water addition, as well as their interactions, significantly influenced A. ordosica seed morphological traits, including seed mass, length, width, curvature, volume, form coefficient and other traits. Water addition resulted in smaller seeds while nitrogen alone led to larger seeds. However, 20% water increase mitigated the effect of nitrogen increase on seed size. Conversely, with a 40% water increase, nitrogen addition caused smaller seeds. (2) Germination percentage was higher at normal temperature (25 °C /15 °C) than that at low temperature conditions (20 °C /10 °C). At low temperature, seed germination traits were more affected by water and nitrogen addition experienced by parental organisms, and when only adding 20% and 40% water, A. ordosica had higher germination percentage. (3) Under the treatments of water and nitrogen addition, the morphological traits such as seed length, width, quality jointly regulated function of dispersal and establishment while form coefficient, 2 h water absorption, germination percentage and germination speed jointly regulated ecological function of germination timing. Adding water or nitrogen alone tent to the variation of only one function (seed dispersal and seedling establishment or seed germination) of A. ordosica seeds, while simultaneous addition of water and nitrogen led to the variation of both functions of A. ordosica seeds. These findings demonstrate that populations of A. ordosica possessed a great adaptability in response to global climate change by altering their functional strategies of seed dispersal, seedling establishment and seed germination.

Aims Clarifying the network characteristics of plant traits is one of the research hotspots in functional ecology. However, our understanding of plant trait networks (PTN) and their driving factors on a seasonal scale is still limited.

Methods We used a LI-6400 portable photosynthetic instrument to regularly measure the light response and carbon dioxide response curves of Artemisia ordosica during the growing season (May to September), as well as leaf structural and biochemical indicators, to explore the correlation and trait network characteristics among 25 leaf traits.

Important findings There were significant correlations between leaf traits at the seasonal scale, and the closest coupling relationship between traits occurred between photosynthetic physiological traits, with a total of 67 pairs of physiological trait combinations showing significant correlation. The edge density, diameter, average path length, and modularity of the PTN are 0.58, 3, 1.51, and 0.08, respectively. The betweenness of leaf tissue density, leaf nitrogen content per unit area, and transpiration rate is relatively high, making it a “bridge” in PTN. PTN does not have an absolute central trait, and physiological traits as a whole exhibit high degree, eigenvector centrality, and clustering coefficient, indicating that the trait network is jointly dominated by physiological traits. Further analysis indicated that the 25 leaf traits at the seasonal scale can be compressed into two major trait dimensions: one is regulated by air temperature and soil moisture, and the other is regulated by photosynthetic effective radiation. The results emphasize that when evaluating the potential response of different trait functional groups to climate fluctuations, it is necessary to distinguish the degree and effect of environmental factors on different traits. If the seasonal response of plant traits to the environment is included in a unified paradigm, it will incorrectly evaluate the adaptability of plant traits.

Aims Understanding the adaptive strategies of plant root morphological traits and biomass allocation in alpine meadows under degradation is crucial for exploring the synergistic relationship between root morphological plasticity and biomass distribution. This knowledge is essential for deepening our insight into the stress tolerance strategies of plants in degraded alpine meadows.

Methods In this study, we investigated the aboveground and belowground biomass, root morphological traits, and their interrelationships in grasses (Poa pratensis and Elymus nutans), sedges (Carex alatauensis and C. moorcroftii), and forbs (Anemone rivularis and Saussurea nigrescens) across alpine meadows with varying degrees of degradation (nondegraded, lightly degraded, moderately degraded, and severely degraded).

Important findings The results show that: 1) Carex alatauensis exhibited the greatest reduction in aboveground biomass under moderate degradation (71.44%) while its root-to-shoot ratio increased the most under light degradation (216.92%) among all species examined. Both Poa pratensis and Anemone rivularis showed increased aboveground and belowground biomass under moderate degradation, and their root-to-shoot ratios showed no significant change with increasing degradation. The relative abundance of aboveground biomass in Anemone rivularis and the relative abundance of belowground biomass in Elymus nutans increased the most under severe degradation (384.90% and 299.57%, respectively). 2) Carex alatauensis showed the greatest decrease in total root length under severe degradation (72.81%), whereas Carex moorcroftii had the greatest increase in total root length under light degradation (14.81%). Degradation increased the average root diameter of Poa pratensis, Carex alatauensis, Carex moorcroftii, and Anemone rivularis while recuding their specific root length. The number of root tips and branching in Poa pratensis, Elymus nutans, Carex alatauensis, Anemone rivularis and Saussurea nigrescens decreased as degradation intensified. 3) The relative abundance of Poa pratensis belowground biomass was significantly correlated with the number of root tips. The relative abundance of belowground biomass in both Elymus nutans and Carex alatauensis depended on the total root length and the number of branching. For Carex moorcroftii, the relative abundance of aboveground biomass was mainly correlated with total root surface area, while the relative abundance of belowground biomass depended on root volume and specific root length. The relative abundance of aboveground biomass in both Anemone rivularis and Saussurea nigrescens was significantly associated with total root length, while their relative abundance of belowground biomass was influenced by specific root length. In conclusion, different dominant plant species adapt to the soil microenvironments caused by degradation by adjusting their biomass allocation and root morphological traits, and these adaptive strategies vary among species, reflecting the diversity of stress tolerance strategies in alpine meadow plants.

Aims Leaf morphology and area variations are essential for understanding plant physiological and ecological functions. This study aims to develop non-destructive and accurate prediction models for leaf area with elliptical and lanceolate shapes across different species.

Methods A total of 4 061 leaf samples from 59 species across three subtropical natural reserves were collected. The relationships between leaf area and leaf length, width were modeled, and modeled leaf areas were compared with actual leaf areas. Model suitability was evaluated through root mean square error, coefficient of determination, and prediction accuracy.

Important findings The results indicate: 1) Significant linear correlations exist between leaf area and leaf length, width across different species, with the product of length and width having the most significant impact, achieving a correlation coefficient of 0.997. 2) Models based on length-width products for elliptic and lanceolate leaves showed root mean square errors of 0.996 and 1.017, determination coefficients of 0.998 and 0.990, and prediction accuracies of 95.32% and 94.89%, surpassing the overall accuracy of 92.76%. 3) Further analysis showed predictive model accuracy of 95.53% and 94.86%, based on mean length-to-width ratios of 59 species, decreasing as leaf length-to-width ratio increased. Therefore, these shape-classified models, using length-width products, offer a quick, accurate method for estimating leaf area in elliptic and lanceolate leaves. Additionally, refining leaf morphology classification improves model accuracy and minimizes the effect of length-to-width ratio variation on predictions.

Aims Leaf and root are sensitive to environmental changes. There are many studies about the responses of leaf and root to climate warming, but the effects of warming on phyllosphere and rhizospheric soil bacterial communities remain unclear.

Methods Two dominant species (Picea asperata and Fargesia nitida) of subalpine coniferous forest in the eastern Qingzang Plateau were selected, and the compositional and functional characteristics of phyllosphere and rhizosphere soil bacterial community between the two species and their responses to simulated warming were studied.

Important findings The results showed that the Chao index and Shannon-Wiener index of bacterial communities in rhizosphere soil were significantly higher than those in phyllosphere of both species. The bacterial diversity in P. asperata was decreased by warming, but that in F. nitida was increased under warming conditions. There were significant differences in bacterial community composition and structure between phyllosphere and rhizosphere. Rhizobiales (41%-46%) were the dominant order of phyllosphere bacterial community, and Vicinamibacterales were the dominant bacterial order in rhizosphere soil. The relative abundance of Burkholderiales and Corynebacteriales increased by about two times in P. asperata phyllosphere, and Acidobacteriales in F. nitida phyllosphere were also increased under warming conditions. However, the rhizosphere bacterial community composition of the two species was less affected by warming. The complexity of rhizosphere bacterial co-occurrence network was higher than that of phyllosphere in both species. The number of links in co-occurrence networks of P. asperata phyllosphere and rhizosphere bacterial community were increased by warming, but this index was decreased in F. nitida phyllosphere and rhizosphere under warming conditions. According to FAPROTAX, the relative abundance of bacterial groups involved in carbon cycling and nitrogen fixation in rhizosphere were significantly higher than those in phyllosphere. The predictive functions of phyllosphere bacteria were more sensitive to warming than those of rhizosphere, and warming increased urealysis function of phyllosphere bacteria community of both species, but significantly decreased the phyllosphere predictive functions of nitrogen respiration, nitrate reduction and nitrate respiration in F. nitida and that of nitrogen fixation in P. asperata. Therefore, there were significant differences in structure and function of bacterial community between rhizosphere and phyllosphere, and the phyllosphere bacterial community was more sensitive to warming than those in the rhizosphere soil.