The leaves and fine roots are the most sensitive and active parts of the above- and below-ground parts of plants, respectively, and they play a very important role in the carbon cycle of the forest ecosystem. The physiological and metabolic characteristics of leaves and fine roots, and their interrelated changes not only reflect the growth status of plants under the background of global warming, but also reveal the response characteristics and adaptation strategies of plants to environmental stress. Their changes have become one of the hotspots and difficulties in the field of global change. A large number of experiments has been carried out domestically and abroad to investigate the change characteristics and response mechanisms in physiological metabolism and of plant leaves and fine roots under global warming conditions from the perspectives of oxidative damage, antioxidant defense and metabolites. At present, some studies found that atmospheric warming will promote the accumulation of active oxygen species in leaves and caused oxidative damage to leaves, while the damage to fine roots is not obvious. But some other studies also showed that fine roots are more affected by soil warming. In summary, how plant leaves and fine roots will respond to climate warming by adjusting their physiological and metabolic characteristics and the interaction between organs and the internal mechanism of these responses have not been fully studied. So, this study systematically reviewed the research progress on the oxidative damage and antioxidant defense characteristics of plant leaves and fine roots under the background of global warming and their interrelated changes, with a view to providing a reference for the research on the response and adaptation mechanism of plants to global warming, and suggest that the following aspects should be carried out in the future: (1) more study on oxidative damage and defense characteristics of plants by warming at population and community scales; (2) combined above- and below-ground phenological characteristics to study the effect of warming on oxidative damage and defense characteristics of plants; (3) deeply analysis on the response of plant oxidative damage and defense characteristics to warming from the correlation between more plant physiological indicators; (4) more concern on the correlation between above- and below-ground of plants, and their seasonal differences.

Aims Studies on the adaptation of plant biomass and nitrogen use efficiency (NUE) to atmospheric nitrogen (N) deposition were helpful to understand the changes of carbon (C) and N cycling in terrestrial ecosystems under the background of global N deposition. However, the effects of N addition on plant biomass and NUE and the main factors affecting these responses remained unclear. Our objective was to explore the responses of biomass and NUE in the whole and different components of plants to N addition.

Methods We conducted a meta-analysis by collecting data from 94 publications focusing on N addition in China, to quantitatively assess the effects of N addition on biomass allocation and NUE of plants, as well as the main influencing factors.

Important findings The results showed that: (1) N addition significantly increased total, aboveground, and belowground biomass while significantly decreased the NUE of different components. Plant aboveground biomass (34.0%) increased more than that of belowground biomass (5.3%), and the decreased belowground NUE (29.9%) was higher than that of aboveground (15.4%). (2) The responses of plant biomass and NUE to N addition varied across ecosystem types, N forms, N addition levels, duration, and water conditions. The responses of plant in grassland and desert to N addition were significantly higher than that in other ecosystems. (3) Soil total N content was the most important factor affecting the responses of plant total, aboveground, and belowground biomass. The responses of plant and aboveground NUE were mainly modulated by N addition rate, and the form of N fertilizer mainly influenced the responses of belowground NUE. In conclusion, the effects of N addition on plant biomass and NUE were opposite, and they were mainly affected by soil total N content and N addition rate, respectively. These findings may provide reference for further research and practice on the distribution and utilization of C and N in plants under the background of N deposition.

Aims Qingzang Plateau is experiencing rapid climate change, including warming, wetting and frequent extreme weather events, however, we know less about the effects of these climate changes on alpine plants.

Methods We observed six phenological sequences of Potentilla saundersiana under simulating multi-level warming and precipitation changes, in 2016 through 2018. Then, by simulating seven different extreme cooling extents, we determined the frost resistance of P. saundersiana, and calculated its safety margin in the growing seasons during the experiment period.

Important findings Warming (1 °C and 2 °C) and precipitation increase (50%) had limited effects on the phenological sequences of P. saundersiana. But when temperature increased by 4 °C, first leafing day was significantly delayed, while first flowering day was significantly advanced. The frost resistance (LT₅₀) of P. saundersiana was (-4.76 ± 4.28) °C, and the safety margin against frost damage was negative in 34% of months of the growing season during 2011-2022, and most of them occurred in May and September, indicating high risk of extreme frost in the early and late growing season. These results revealed the effects of multi-level warming and increased precipitation on the phenological sequences of P. saundersiana, clarified the resistance of P. saundersiana to extreme cooling events, and provide insight into predicting the response of alpine plants to climate change in the future on the Qingzang Plateau.

Aims The management policies of China’s rangeland have shifted from grassland fencing and grazing removal towards a more balanced approach between livestock loads and herbage biomass for grazing. This shift has led to a growing emphasis on the theoretical and practical significance of using smart grazing management to promote grassland restoration.

Methods In this study, we conducted a two-year experiment involving continuous grazing, traditional rotational grazing, and intensive rotational grazing as treatment groups and no grazing as a control group to estimate the ecological and economic impacts of implementing intensive rotational grazing in a typical steppe of Xilin Gol.

Important findings Intensive rotational grazing could restore the biomass of Leymus chinensis and Stipa spp., and significantly put weight on the adult sheep. Furthermore, the advantage of intensive rotational grazing lies in extending the post-grazing recovery time and curbing selective animal grazing through balanced livestock loads and herbage biomass. Therefore, our preliminary results suggest that employing intensive rotational grazing and following balanced livestock loads and herbage biomass could be a promising approach to achieve a harmonious blend of economic benefits and ecosystem services in rangeland management practices.

Aims The spatial distributions and associations of tree species offer valuable insights into interspecies relationships and their interplay with the surrounding environment. These insights are critical for understanding community assembly and species coexistence.

Methods To investigate the spatial distribution patterns of the tree species in the mid-mountain moist evergreen broadleaf forest in the south of Gaoligong Mountains, the spatial distributions and interspecies associations of ten dominant species were analyzed by using the point pattern analyses for all woody plants with diameter at breast height ≥ 1 cm in a 4 hm² plot.

Important findings Our results showed: (1) All ten dominant species and the overall tree population exhibited a J-shaped diameter class distribution, indicating growing populations with successful recruitment. (2) Under the complete spatial randomness with univariate pairwise correlation functions, the small-scale patterns of species distribution were aggregated. This aggregation weakened with increasing scale, resulting in random and uniform distribution at larger scales. After accounting for environmental heterogeneity, the range of aggregation was reduced, while the range of random and uniform distribution expanded. (3) Bivariate pairwise correlation function tests under complete spatial randomness null model demonstrated that interspecies correlations were dominated by significant positive associations, while become no significant association under heterogeneous Poisson null model. In conclusion, the distribution patterns and correlations of ten dominant species in Gaoligong Mountains varied with spatial scale, further emphasizing the strong scale-dependency of species distributions. This suggests that forests in Gaoligong Mountains were influenced by several factors, such as dispersal limitation, negative density dependence, and habitat heterogeneity.

Aims Aging is an important process in the life cycle of plants, and the capacity of different organs to store nutrients and their activities in plants are important in judging individual aging. To date, the changes in these aspects during the aging process of different age-class ramets in clonal plants remain unclear.

Methods Aster pekinensis is a typical clonal plant with a root sucker. On the grassland of Northeast China, its ramets are mainly composed of three age classes (1a, 2a and 3a). In this study, the differences in water soluble carbohydrates (WSC) contents among storage organs (stem base, root collar, and taproot) or among age classes, and the seasonal variation of rhythm in the three ramets of Aster pekinensispopulations were analyzed quantitatively.

Important findings At the yellow-leaf stage, the WSC content of the taproot was higher than that of the root collar. The WSC content of root collars and taproots in 1a and 2a ramets was significantly higher than that in 3a ramets. The WSC content of stem bases was significantly lower in 1a ramets than in 2a and 3a ramets. Throughout the entire growth season, the root collars of 1a ramets always received priority allocation of nutrients, and their WSC content continued to accumulate in an exponential form. The nutrient contents in the root collars of the 2a and 3a ramets, as well as the taproots of the three age-class ramets, were all consumed first and then accumulated, and the WSC content changed in the form of a quadratic curve. The capacity of the taproot to store nutrients was generally greater than that of the root collar, whereas the activity of the root collar was greater than that of the taproot across the three age-class ramets in Aster pekinensispopulations. The nutrient storage capacity and activity of young ramets were strongest. There were no signs of aging in adolescent ramets. The old ramets were dramatically aged, and their nutrient storage capacity and activity reduced significantly. This study provides a new approach that combines qualitative and quantitative analyses to understand the relationship between the spatiotemporal changes in WSC content and the aging process of individuals in plant populations.

Aims This study investigated the effects of mother tree age, low temperature stress, and their interaction on the growth and leaf physiological characteristics of Caragana korshinskii seedlings.

Methods In this study, seeds of C. korshinskii were selected from an artificial forest in the hilly and sandy area of northwest Shanxi Province, representing five mother tree ages (7, 13, 19, 41 and 51 a). These seeds were germinated, and the resulting seedlings (about 2 months) were used as test material. The low temperature stress was applied at (-8 ± 1) °C with varying stress levels: W1 (6 h), W2 (12 h), W3 (24 h), W4 (48 h) and W5 (72 h). A control group (CK) was maintained at 25 °C (normal temperature). Different growth and physiological indicators related to frost resistance were determined, and a comprehensive evaluation was conducted using the membership function method.

Important findings The results showed that: (1) There were significant differences in the impact of low temperature stress on photosynthetic pigments and osmotic adjustment substances in C. korshinskii seedlings from different mother tree ages. Notably, mother tree age and low temperature stress had significant effects on chlorophyll (Chl) a content, while the contents of Chl b, Chl (a+b), carotenoid and Chl a/b in C. korshinskii seedlings were influenced by mother tree age, low temperature stress and their interaction. Low temperature stress as well as the interaction between low temperature stress and mother tree ages, had a significant effect on soluble sugar content, while mother tree ages, low temperature stress and their interaction significantly influenced free proline content. With the increasing low temperature stress duration, the contents of Chl a, Chl b, and Chl (a+b) in the leaves of C. korshinskii seedlings initially decreased and later increased, while the Chl a/b and carotenoid content exhibited an initial increase followed by a decreased, and the content of free proline increased. (2) Low temperature stress had variable effects on the growth of C. korshinskiiseedlings from different mother tree ages. Plant height, leaf number, dry mass, main root length and root shoot ratio of seedlings germinated from seeds from different age plants displayed significant differences, with values initially increasing and then decreasing with the increase in mother tree age. However, low temperature stress significantly inhibited the plant height of the seedlings, with no significant interaction observed between mother tree age and low temperature stress on the aforementioned growth parameters. (3) Seedlings germinated from the seeds of young mothers (7, 13 a) showed stronger frost resistance than those from older mothers (19, 41, 51 a). In summary, physiological parameters including Chl b content, Chl (a+b) content, Chl a/b, carotenoid content and growth parameters such as plant height, leaf number, dry mass, main root length and root shoot ratio can serve as indicators for assessing frost resistance in C. korshinskii seedlings. Besides that, when promoting the natural regeneration of C. korshinskii forest through artificial means, selecting seeds from young and middle-aged C. korshinskii plants can enhance the success of regeneration.

Aims To understand the interaction between maize and its colonized microbiome, the genetic mechanism of interaction between maize and phyllospheric microbiome was explored.

Methods Four modes of interactions between microorganisms, including mutualistic symbiosis, antagonism, aggression, and altruism, were identified by using mathematical models. Based on 230 phyllospheric microbiome datasets of maize, network mapping was applied to characterize the interaction between maize and phyllospheric microbiome.

Important findings Sixty-seven hub microbes were identified in the microbial interaction network, 405 significant Single Nucleotide Polymorphisms in maize were screened through network mapping, and finally 23 hub genes were located, and it was found that they played an important role in promoting plant growth, resisting pathogenic bacteria infection and tolerating abiotic stresses.

Aims Both the carbon cycle and the function of grassland ecosystem as a carbon sink are impacted by the rising nitrogen deposition. Active organic carbon content is an important measure that can reveal changes in soil carbon pool. For a thorough understanding of carbon cycling and the creation of sensible ecosystem management strategies, it is essential to investigate the impacts of nitrogen addition on the active organic carbon fractions of grassland soils.

Methods Five different nitrogen addition treatments were set up in a temperate typical steppe of Nei Mongol. Soil organic carbon fractions content, soil physical and chemical properties, aggregate stability, microbial activities and extracellular enzyme activities were measured. Pearson correlation and structural equation model (SEM) were used to examine the relationships.

Important findings Nitrogen addition reduced the contents of dissolved organic carbon (DOC), microbial biomass carbon (MBC), and easily oxidizable organic carbon (EOC). The contents of DOC, MBC, and EOC all decreased with the increases of soil depth. The treatment of 5 g·m^-2·a^-1 nitrogen addition significantly promoted the decomposition of active organic carbon fractions. The effect of nitrogen addition on soil active organic carbon fractions content was regulated by biotic (microbial biomass, extracellular enzyme activity, etc.) and abiotic (soil physical and chemical properties, aggregate stability, etc.) factors. Nitrogen addition reduced soil density, increased mean mass diameter and the proportion of large aggregates, increased the contact between organic matter and substrate, promoted the decomposition of active organic carbon, and reduced the contents of DOC and EOC. Nitrogen addition inhibited the activities of polyphenol oxidase and peroxidase, reduced the decomposition of difficult-to-decompose organic matter and the contents of EOC and MBC. Nitrogen addition increased the activities of β-glucosidase and cellulose hydrolase, promoted the utilization of DOC by microorganisms, and reduced the content of DOC. Our results indicated that nitrogen addition treatment can affect the decomposition process of active organic carbon by changing soil physicochemical properties and the secretion of extracellular enzymes from microorganisms, promoting the release of carbon in grassland soils. This provided a theoretical basis for further exploration of grassland soil carbon dynamics under nutrient addition in the future.

Aims It is of great significance to explore soil extracellular enzyme activity and its stoichiometry to understand soil nutrient availability and changes in the nutrient requirements of microorganisms. Subtropical forest ecosystems have high net primary productivity, but the availability of phosphorus (P) in soil is low due to severe soil weathering. Under climate change (i.e., warming, elevated CO₂ concentration), plant productivity is predicted to increase, which would increase the input of leaf litter. However, it is still unclear whether the effect of increasing litter input on soil enzyme activity and its stoichiometry is affected by soil P availability in the future.

Methods This study investigated the effects of the addition of three kinds of litters (Pinus massoniana, Michelia macclurei and Liquidambar formosa) with different quality (characterized by different leaf C:N or C:P) and P on soil properties and enzyme activities in subtropical low-P soils. By analyzing the stoichiometric ratio of soil enzymes, vector length (VL), and vector angle (VA), the relative nutrient limitation to soil microorganisms and the key regulatory factors were explored.

Important findings The results showed that litter addition increased β-N-acetyl-glucosaminidase and acid phosphatase (ACP) activities. The addition of litter significantly increased VL and VA in the order of M. macclurei > L. formosana > P. massoniana. Litter addition could change the status of nutrient limitation to soil microorganisms, with the degree of changes being related to the quality of litter. Compared with the addition of litter alone, the addition of both litter and P significantly increased the content of available P, and reduced ACP activity and VA, suggesting that P addition could help alleviate P limitation to soil microorganisms under the input of litter. Redundancy analysis results showed that the soil carbon/nitrogen ratio, dissolved organic carbon content, and available P content were the main factors affecting enzyme activities and their stoichiometry. In conclusion, our study found that the response of soil microbial nutrient limitation to litter input in subtropical forest was not only affected by litter quality, but also regulated by soil P availability. This study provides a theoretical reference for the response of microbial nutrient acquisition strategies to different litter inputs and P additions in subtropical forests under future climate change, and is conducive to improving our understanding of the soil biogeochemical cycling in subtropical low P forest ecosystems.

Dongtou National Marine Park (DNMP) locates at the southeast coast of China, and the climax vegetation belongs to the subtropical evergreen broadleaf forests. However, we are still unclear about the vegetation types on most islands in DNMP. The objective of this study is to investigate vegetation types and characteristics across islands in DNMP. We conducted vegetation survey by setting up 90 sampling plots on the islands in DNMP. Species composition and habitat information in each plot were recorded and vegetation type classification and naming were referred according to the Vegegraphy of China. A total of 3 Vegetation Formation Groups, 8 Vegetation Formations, 34 Alliances, and 80 Associations were found in DNMP. The widely distributed vegetation types included Pinus thunbergii evergreen needleleaf forest, Casuarina equisetifolia evergreen broadleaf forest, Acacia confuse evergreen broadleaf forest, Eurya emarginata evergreen broadleaf shrubland, and Eurya japonica evergreen broadleaf shrubland. Our finding provides basic and detail information of vegetation structure and composition in these continental islands in eastern China.