The leaves and fine roots are the most sensitive and active parts of the aboveground and belowground parts of plants, and 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 at home 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 believe 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 studies also believe 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 believed that the following aspects should be carried out in the future: (1) enhanced the study of 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 the response of plant oxidative damage and defense characteristics to warming from the correlation between more plant physiological indicators; (4) strengthen the research on the correlation of plants above and below ground and seasonal differences.

Aims Studies on the adaptation of biomass and nitrogen use efficiency (NUE) of whole plant and aboveground and belowground parts to atmospheric nitrogen (N) deposition were helpful to understand the changes of carbon (C) and N cycling in terrestrial ecosystems of China 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 effects of biomass and NUE to N addition in the whole and different components of plants. Methods We collected the results of artificial N addition in China from 95 publications. Meta-analysis was used to quantitatively assess the effects of N addition on biomass allocation and NUE of plants, their main influencing factors were also evaluated using this database. Important findings The results indicated that: (1) N addition significantly increased plant total, aboveground and belowground biomass while significantly decreased the NUE of different components(p < 0.01). Plant aboveground biomass (34%) increased more than that of belowground biomass (5.3%), and the decreased plant belowground NUE (29.9%) was higher than that of aboveground NUE (15.4%). (2) The effects of plant biomass and NUE to N addition were significantly different according to ecosystem types, N forms, N addition levels, duration and water conditions(p < 0.01), the responses of plant in grassland and desert ecosystems 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. Meanwhile, the responses of plant and aboveground NUE were mainly modulated by N addition rate, and the form of N fertilizer mainly influenced the effects 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 a 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 severe 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 Choosing Potentilla saundersiana as the object, we observed six phenological sequences of P. saundersiana under simulating multi-level warming and precipitation changes, in 2016, 2017 and 2018. Then, by simulating seven different extreme cooling gradients, we determined the frost resistance of P. saundersiana, and the safety margin in the growing season from 2011 to 2022 was calculated. Important findings Warming (1 ℃ and 2 ℃) and precipitation increase (50%) showed limited effects on the phenological sequences of P. saundersiana. When the temperature increased to 4 ℃, first leafing day was significantly advanced, and first flowering day was significantly delayed. The frost resistance (LT50) of P. saundersiana is –4.76 ± 4.28 ℃, and the safety margin against frost damage is negative in 34% of months of the growing season of 2011–2022, and most of them occurred in May and September, indicating that P. saundersiana was at high risk of extreme frost events early and late in the growing season. The results of this study 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 basis to predict response of alpine plant on Qingzang Plateau to climate change in the future.

Aims China’s rangeland management policy has shifted from grassland fencing and grazing removal towards a balancing grazing between livestock loads and herbage biomass. Therefore, it is an essential theoretical and practical issue to promote grassland restoration by smart grazing management. Methods In this study, we executed a two-year experiment with continuous grazing, traditional rotational grazing, and intensive rotational grazing as treatment groups and no grazing as control group to estimate the ecological and economic effects of intensive rotational grazing in a typical steppe of Xilingol. 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 is rooted in extending the post-grazing recovery time, and limiting the selective grazing of the animal under the balancing of livestock loads and herbage biomass. Therefore, our preliminary results suggest that it is a promising way to use intensive rotational grazing and to follow the balancing of livestock loads and herbage biomass to achieve the synergy of economic outcomes and ecosystem services in rangeland management practices.

Aims The spatial distribution and associations of tree species can reflect interspecies relationships and their interaction with the surrounding environment, which are of great significance for revealing community construction and species coexistence. Methods Therefore, to explore the spatial distribution pattern of the tree species in the mid-mountain moist evergreen broadleaf forest in the southern of Gaoligong Mountains, the spatial distribution and interspecies associations of the top ten dominant species with important values were analyzed by using the point patter analysis method for all woody plant with DBH ≥ 1 cm in the 4 hm2 plot of Gaoligong Mountains. Important findings The results showed that: (1) The diameter class structure of the ten dominant species and the species of whole plot were distinctly J-shaped, which indicated that they were a growing population and conducive to population recruitment. (2) Under the complete spatial model randomness with univariate pairwise correlation functions, the small-scale distribution was aggregation. The degree of aggregation then decreased with increasing scale, the large scale was random distribution and uniform distribution. After removing environmental heterogeneity, the scale range of aggregation distribution was shortened, and the scale range of random distribution and uniform distribution were increased. (3) Under the bivariate pairwise correlation functions test simulation, complete spatial randomness model of the correlation among the ten species was dominated by significant positive association, while the prerequisite model was dominated by no association. To conclude, the distribution pattern and correlation of four dominant species in Gaoligong Mountains varied with the spatial scale, which further proved that the spatial distribution of species were strongly scale-dependent. Thereby, the forest was affected by several factors, such as diffusion restriction, negative density dependence and habitat heterogeneity and so on.

Aims Aging is an important stage in the life cycle of plants, and the nutrient storage capacity and activity of different organs in plants are important criteria for judging individual aging. To date, the changes in the storage capacity and activity of storage organs during the aging process of different age class ramets of clonal plants remain unclear. Methods Aster pekinensis is a root sucker form clonal plant. In the Northeast grassland, the ramets are mainly composed of three age classes. In this study, the differences of water soluble carbohydrates (WSC) contents among storage organs (stem base, root collar and taproot) and age classes, and the seasonal variation rhythm in the 1-3 years old ramets of Aster pekinensis population were analyzed quantitatively. Important findings In the yellow leaves stage, the WSC content of the taproot was higher than that of the root collar in the Aster pekinensis population. The WSC content of root collar and taproot of 1 a and 2 a ramets was significantly higher than that of 3 a ramets. The WSC content of stem base was significantly lower in the 1 a ramets than in the 2 a and 3 a ramets. Throughout the entire growth season, the root collars of the 1 a ramets in Aster pekinensis population 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 2 a 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 nutrient storage capacity of the taproot was generally greater than that of the root collar, whereas the activity of the root collar was greater than that of the taproot in the three age class ramets in Aster pekinensis population. The nutrient storage capacity and activity of young-aged ramets were the strongest. There were no signs of aging in adolescent-aged ramets. The old-aged ramets were significantly aging, and their nutrient storage capacity and activity reduced significantly. This study provides a new approach that combines qualitative and quantitative analysis to understand the relationship between the spatio-temporal changes of WSC content and the aging process of individual in plant populations. Methods Aster pekinensis is a root sucker form clonal plant. In the Northeast grassland, the ramets are mainly composed of three age classes. were sampled. The differences of WSC contents among storage organs (stem base, root collar and taproot) and age classes, and the seasonal variation rhythm in the 1-3 years old ramets of Aster pekinensis population were analyzed quantitatively. Important findings In the yellow leaves stage, the WSC content of the taproot was higher than that of the root collar in the Aster pekinensis population. The WSC content of root collar and taproot of 1a and 2a ramets was significantly higher than that of 3a ramets (p < 0.05). The WSC content of stem base was significantly lower in the 1a ramets than in the 2a and 3a ramets. Throughout the entire growth season, the root collars of the 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 classes ramets, were all consumed first and then accumulated, and the WSC content changed in the form of a quadratic curve. The nutrient storage capacity of the taproot was generally greater than that of the root collar, whereas the activity of the root collar was greater than that of the taproot in the three age class ramets in Aster pekinensis population. The nutrient storage capacity and activity of young-aged ramets were the strongest. There were no signs of aging in adolescent-aged ramets. The old-aged ramets were significantly aging, and their nutrient storage capacity and activity reduced significantly. This study provides a new approach that combines qualitative and quantitative analysis to understand the relationship between the spatio-temporal changes of WSC content and the aging process of individual in plant populations.

Abstract Aims This study investigated the effects of stand age, low temperature stress and their interaction on the growth and leaf physiological characteristics of Caragana korshinskii seedlings. Methods In this study, the seeds of C. korshinskii in an artificial forest were selected from five stand ages (7, 13, 19, 41 and 51 a) in the hilly and sandy area of northwest Shanxi Province for germination, and the seedlings (about 2 months) were taken as test material. The low temperature stress of (-8 ± 1) °C was set, and the different stress levels were W1 (6 h), W2 (12 h), W3 (24 h), W4 (48 h) and W5 (72 h), and 25 °C (normal temperature) was taken as a control (CK). The growth physiological indexes related to frost resistance were determined, and the membership function method was used for comprehensive evaluation. Important findings The results showed that: (1) There were significant differences in the effects of low temperature stress on photosynthetic pigments and osmotic adjustment substances in C. korshinskii seedlings of different stand ages. Among them, stand age and low temperature stress had significant effects on chlorophyll a content, and the standage, low temperature stress and their interaction had significant effects on the contents of chlorophyll b, total chlorophyll, carotenoid and chlorophyll a/b in C. korshinskii seedlings. The interaction between low temperature stress and stand ages and low temperature stress had a significant effect on soluble sugar content, and the stand ages, low temperature stress and their interaction had a significant effect on free proline content. With the increase of low temperature stress time, the contents of chlorophyll a, chlorophyll b and total chlorophyll in the leaves of C. korshinskii seedlings decreased first and then increased, while the chlorophyll a/b and carotenoid content increased first and then decreased, and the content of free proline increased. (2) The effects of low temperature stress on the growth of C. korshinskii seedlings at different stand ages were significantly different. On one hand, there were significant differences in plant height, leaf number, dry mass, main root length and root/shoot ratio of seedlings germinated from seeds from different ages plants, which increased first and then decreased with the increase of stand age. On the other hand, low temperature stress significantly inhibited the plant height of seedlings, while the interaction between stand age and low temperature stress had no significant effect on the above growth parameters of seedlings. (3) The seedlings germinated from the seeds of young mother (7, 13 a) have stronger frost resistance than those of older (19, 41, 51 a) ones. In summary, physiological indicators chlorophyll b content, total chlorophyll content, chlorophyll a/b, carotenoid content and growth indicators plant height, leaf number, dry mass, main root length and root/shoot ratio can be used as indicators of frost resistance identification of C. korshinskii seedlings. At the same time, when the natural regeneration of C. korshinskii forest is promoted artificially, the seeds of young and middle-aged C. korshinskii can be selected for seedling cultivation, thereby improving the success of regeneration. Keywords windy and sandy hilly area in northwest Shanxi; stand age; Caragana korshinskii seedlings; low temperature stress; osmoregulation; photosynthetic pigment; root/shoot ratio

Aims To understand the interaction between maize and its colonized microbiome, the genetic mechanism of interaction between maize and leaf microbiome was explored. Methods Four ways to characterize the interaction between microorganisms using mathematical models: mutualistic symbiosis, antagonism, aggression, and altruism. Analysis of 230 leaf microbiome data of maize, network mapping was used to study the genetic mechanism of interaction between maize and leaf microbiome. Important findings 67 hub microbes were identified in the microbial interaction network, 405 significant Single Nucleotide Polymorphisms 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 The mechanism of the carbon cycle and the function of the grassland ecosystem as a carbon sink are both continuously impacted by the rising nitrogen deposition. An important measure that can reveal changes in the soil's carbon pool is active organic carbon. For a thorough understanding of the carbon cycle process and the creation of sensible ecosystem management strategies, investigating the impact of nitrogen addition on the active organic carbon fractions of grassland soil is essential. Methods In this paper, five different nitrogen addition treatments were set up in the typical temperate steppe of Nei Mongol. Soil organic carbon fractions, 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 results. Important findings Nitrogen addition reduced the contents of dissolved organic carbon (DOC), microbial biomass carbon (MBC) and easily oxidizable organic carbon (EOC). Additionally, the contents of DOC, MBC and EOC all decreased with the increase of soil depth. The 5 g·m–2·a–1 nitrogen addition treatment significantly promoted the decomposition of active organic carbon fractions. The effect of nitrogen application on soil active organic carbon fractions 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 (SD), increased mean mass diameter (MMD) and the proportion of large aggregates, increased the contact between organic matter and substrate, promoted the decomposition of active organic carbon, and reduced DOC and EOC. Nitrogen addition inhibited the activities of polyphenol oxidase (POX) and peroxidase (PER), reduced the decomposition of difficult-to-decompose organic matter, and reduced the content of EOC and MBC. In addition, the addition of nitrogen increased the activities of β-glucosidase (BG) and cellulose hydrolase (CB), promoted the utilization of DOC by microorganisms, and reduced the content of DOC. The above 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 typical temperate grassland soil. 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 a high level of plant 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 will 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 phosphorus 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 carbon:nitrogen or carbon:phosphorus) and P on soil properties and enzyme activities in subtropical low-P soils. By analyzing the enzyme stoichiometric ratio, vector length (VL), and vector angle (VA), the relative nutrient limitation of 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. Moreover, we found that the addition of litter significantly increased the VL and VA in the order of M. macclurei > L. formosana > P. massoniana. The results indicated that litter addition could change the nutrient restriction status of soil microorganisms, and the degree of influence was related to the quality of litter. Compared with the addition of litter alone, the addition of litter combined with P significantly increased the amount of available P, and reduced ACP activity and the VA, suggesting that P addition could help alleviate the P limitation of soil microorganisms under the input of litter. Redundancy analysis results showed that the soil carbon/nitrogen ratio, dissolved organic carbon, and available P were the main factors affecting enzyme activities and their stoichiometric changes. 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 cycle in subtropical low phosphorus forest ecosystems.

Aims Dongtou National Marine Park (DNMP) is located on the southeast coast of China, belonging to the subtropical evergreen broad-leaved forest. However, we are still unclear about the vegetation types on most islands in DNMP. Therefore, we aimed to investigate the main vegetation types on islands in DNMP, which is expected to provide data support for vegetation research and vegetation restoration on ocean islands in eastern China. Methods We conducted vegetation survey by setting up sampling plots on the islands in DNMP. A total of 90 plots were set up on 16 islands in DNMP. We recorded the species composition and habitat in-formation in each plot and referred to the "Vegegraphy of China" for vegetation type classification and naming. Important findings A total of 3 Vegetation Formation Groups, 8 Vegetation Formations, 34 Alliances, and 80 Associations were found in DNMP. 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 were widely dis-tributed on islands.