The alteration of terrestrial carbon cycling under climate warming is regulated by soil organic carbon (SOC) dynamics. Previous studies have developed multiple warming methods, mainly including laboratory incubation experiment, field in-situ manipulative experiment, and temperature gradient sampling, to investigate the responses and mechanisms of SOC dynamics to climate warming. However, due to the methodological limitations, the studies on the effect of warming on SOC dynamics cannot lead to consistent conclusions. SOC dynamics mainly include two processes: carbon input and carbon decomposition, and are also regulated by carbon persistence. The changes of carbon input, carbon decomposition, and carbon persistence together determine the response of SOC dynamics to warming. Previous studies showed that both carbon input and decomposition may positively respond to warming, which is related to the enhanced activities of plants and soil microbes. However, some studies pointed out that warming-induced alterations of soil physical and chemical properties (e.g., the decrease of soil water content) and biological processes (e.g., microbial community thermal adaptation) may affect the responses of carbon input and decomposition to warming. Moreover, inconsistent responses may arise when focusing on the SOC responses to warming in top (0-30 cm) or deep (>30 cm) soils due to the limitations of environmental factors on carbon input and decomposition in deep soils, as well as the different persistence of SOC in deep soils compared to top soils. Future research should focus on developing new warming methods, increasing research on deep soils and climate-sensitive ecosystems, introducing new technologies to study the source, structure, and protection of soil organic matter, paying attention to the response of plant-soil animal-soil microbe system to warming and its regulation on SOC dynamics, to improve uncertainties in carbon cycle models and more accurately predict the feedback of the global carbon cycle to climate warming.

Aims The nutrient foraging strategies of fine roots and arbuscular mycorrhizal (AM) fungi directly affect plant productivity and carbon sequestration, which are a key factor influencing the stability of forest ecosystems. Nutrient foraging accuracy is an important aspect of the nutrient foraging strategy, which refers to the ability of plants to accurately deploy their roots and mycelia to relatively nutrient-rich patches. However, the tradeoff between foraging precision of root length and foraging precision of mycelia of arbuscular mycorrhizal tree species and whether fine root morphology can predict foraging accuracy are still controversial.
Methods In this study, 17 AM tree species in a natural broadleaf evergreen forest in the central subtropics were tested for responses to phosphorus addition to in situ root bags in the field to simulate phosphorus nutrient patches in the soil. After 4 months application of phosphorus fertilizer, morphological scanning and analysis were carried out on the fine roots of the control group and the phosphorus addition group. Mycelia in the soil were extracted by the membrane filtration method and observed by electron microscope. Mycelia with no septa in the middle and easy to stain were screened as AM mycelia, and their length was calculated. On this basis, root length foraging precision and mycelial foraging precision were calculated to investigate their trade-off and also their correlation with fine root morphology in subtropical AM tree species.
Important findings Root length foraging precision and mycelial foraging precision of AM species were independent of each other. There was a significant positive correlation between fine root tissue density and root length foraging precision, a significant negative correlation between fine root diameter and mycelial foraging precision, and a significant positive correlation between specific root length and mycelial foraging precision. These results can help understand root nutrient foraging strategies of AM species in subtropical evergreen broadleaf forests, and suggest that easily observable metrics such as fine-root morphology can be used for assessing the accuracy of fine-root nutrient foraging of AM species.

Aims Carbon sequestration in terrestrial ecosystems is one of the important ways to slow down the rise of atmospheric CO₂ concentration. Therefore, understanding the natural vegetation ecosystems carbon storage (ECS) in response of future climate change is critical for making of regional land management policies.
Methods In this study, the sensitive parameters of LPJ-GUESS model are calibrated based on genetic algorithm. Using the downscale climate data-driven model, combined with Mann Kendall test, Sen’s slope estimation and partial correlation analysis, the temporal and spatial patterns, trend change characteristics and climate dominant factors of China’s ECS from 2001 to 2100 are analyzed.
Important findings The Nash-Sutcliffe efficiency coefficient and Pearson correlation coefficient of the calibrated LPJ-GUESS model in simulating ECS are 0.751 and 0.901, respectively, indicating that the LPJ-GUESS model can simulate China’s ECS well. During 2001-2020, China’s ECS decreased from southeast to northwest, with a total amount of 156.06 Pg. Vegetation, litter and soil carbon storage accounted for 34.2%, 1.9% and 63.8% of total ECS, respectively. The ECS in 2081-2100 shows similar spatial pattern with that in historical periods. The total amount of ECS at the end of this century are expected to increase by 0.51-11.16 Pg. The growth rates of China’s ECS was 8.5 g·m^-2·a^-1 and 3.7-21.0 g·m^-2·a^-1 during 2001-2020 and 2021-2100, respectively. During 2021-2100, significant increases of ECS are observed in southeast China, Nei Mongol Plateau, Qingzang Plateau (37-44 g·m^-2·a^-1), while obvious decreases (45-72 g·m^-2·a^-1, in the southern Yunnan-Guizhou Plateau, hilly areas in Guangxi and Guangdong. In northwest China, temperature is the dominant factor affecting ECS. The influences of precipitation on ECS are strengthened from the southeast to northwest. In high latitude and high-altitude areas, radiation is the dominant factor of ECS. CO₂ plays the most important role on ECS across about 47.9%-56.1% of China’s area.

Aims The growth and survival patterns of species might be affected by global climate change. Predicting changes of the potential range of geographic distribution for a certain species under climate change is important to understand the response of the species to climate change, and helps to formulate scientific conservation strategies for the species. Cupressus gigantea is an endemic species of both the Yarlung Zangbo River and one of the first class National Protection Wild Plants. However, this species faces dual pressures from resource development and climate change. We here research the distribution pattern on the both side of the Yarlung Zangbo River from Nang County to Danniang Town of Nyingchi.
Methods In this investigation, we simulated the habitat suitability of C. gigantea under current and two climate change scenarios from 2081 to 2100 (SSP5-8.5: high emission scenario and SSP1-2.6: low emission scenario) in Xizang by using maximum entropy models (MaxEnt), generalized liner models (GLM) and generalized additive models (GAM) with ArcGIS spatial analysis based on the current actual geographical distribution information. All the data were obtained by field investigation, with topographic factor variables and environmental data being collected or predicted under current and future climatic conditions, respectively.
Important findings The results of the study show that: (1) The potential geographical distribution of C. gigantea was narrow, with the suitable distribution areas beings concentrated in Gyaca County to Gongbo’gyamda County, through which the Yarlung Zangbo River in Xizang. And others were scatterly distributed in Lhünzê County, Gonggar County, and Cona County in eastern Xizang. (2) Environmental factors which had significant impacts on the potential geographic distribution of C. gigantea were the average air temperature of the coldest quarter, temperature seasonality, mean of monthly (maximum temperature-minimum temperature), and altitude with suitable ranges of -1.62-2.14 °C, 565.29-603.78, 11.66-12.97 °C and 2 898-3 550 m, respectively. (3) The general suitable area of C. gigantea under future climate change scenarios tended to expand compared with the potential geographic distribution area, and its expansion of the suitable area range of C. gigantea under the SSP5-8.5 climate scenario was much higher than the SSP1-2.6 climate scenario. (4) The center of mass in the future scenario displayed an overall trend to the southwest, and the distribution area of C. gigantea also showed a trend to the southwest of the middle reaches of the Southwest Yarlung Zangbo River. Our findings provided the scientific significance and practical guidance for investigating key environmental factors for the growth, restoration and conservation of C. gigantea.

Aims Studying the impact of climate warming on radial growth and biomass allocation of trees is crucial for accurately evaluating the carbon sequestration capacity of trees under climate change.
Methods In 2004, the seedlings of Larix gmelinii from four different locations (i.e., Tahe, Songling, Heihe and Dailing from north to south) were transplanted southward to a common garden at Mao’ershan Forestry Research Station in Heilongjiang Province to simulate climate warming. The radial growth and biomass allocation of trees in common garden and original sites were measured simultaneously.
Important findings Warming treatment significantly increased the radial growth of trees from Songling and Tahe sites. The stem diameter at breast height (DBH), diameter at 10 cm from the ground (D₁₀), relative increasing rate of DBH and D₁₀, and relative increasing rate per warming unit of DBH and D₁₀ increased with the increasing warming degree. The relative increasing rate of DBH for Songling and Tahe sites were 58.62% and 101.49%, and the relative increasing rate per warming unit were 16.11%·°C^-1 and 18.79%·°C^-1, respectively. Warming treatment significantly decreased the proportion of leaf, branch and root biomass and increased the proportion of stem, aboveground biomass of trees from Tahe site. The proportion of root biomass significantly decreased and the proportion of stem biomass increased for the trees from Songling site under warming treatment. The root-shoot ratio significantly decreased for the trees from Songling and Tahe sites under warming treatment. Climate warming can affect the radial growth and biomass allocation of L. gmelinii, and this effect varied with the degree of warming.

Aims Exploring the impact of climate warming on stoichiometric characteristics of trees is of significance for better understanding the response mechanism of trees to climate change.
Methods In 2004, we conducted a common garden experiment by transplanting Larix gmelinii trees from four provenances to a common garden near the warm edge of this species’ range in the Mao’ershan Ecological Station of China, in order to measure the concentrations of carbon (C), nitrogen (N) and phosphorus (P) in leaves of short branch, leaves of long branch, short branches, long branches, and fine roots at three diameter classes in response to warming.
Important findings The C, N, and P concentrations in leaves of short branch and roots of all diameter classes, and the N and P concentrations in leaves of old branch significantly differed among provenances. The provenances at high latitude sites were characterized by lower C and N concentrations and higher P concentration compared to those at low latitude sites. Warming treatment significantly increased the C concentration in all organs (except root at 1-2 mm diameter), and also significantly increased the N concentration in leaves, long branches and roots <1 mm diameter, and the P concentration in all organs (except short and long branches). The effect of warming on C and P concentrations decreased with the increasing warming, but increased for N concentration. The C:N, C:P and N:P in all organs (except short and long branches) significantly varied with provenances. The provenances at high latitude sites had higher C:N and lower C:P and N:P compared to those at low latitude sites. Warming treatment significantly decreased the C:N, C:P and N:P in all organs except short and long branches. In summary, the stoichiometric characteristics had evident geographical variations in resource acquisition organs of leaves and roots of L. gmelinii. Warming treatment mainly alleviated the constraints on the demand for N and P in leaves and roots, and simultaneously reduced the C sequestration efficiency of N and P. The impact of climate warming on the stoichiometric characteristics of C and P elements decreased as the increasing warming, except N element.

Aims The aim of this study is to develop a comprehensive understanding of the variations in tree height and the underlying mechanisms shaping them in China’s coastal mangroves. This knowledge will serve as a scientific foundation for the restoration and afforestation efforts in China’s coastal mangrove regions, as well as the reconstruction of mangrove ecosystems.
Methods To achieve this, we conducted a comprehensive analysis of existing literature spanning the years 1990 to 2022, examining the interplay between soil composition, climate conditions, and tidal range in relation to tree height within China’s mangrove ecosystems. We established a database of mangrove tree height and environmental factors to compare the differences in tree height and environmental factors between mangroves in Guangxi and the Southeast China coast. Additionally, we analyzed the relationship between environmental factors and mangrove tree height as well as the key factors affecting the tree height of mangroves in Guangxi coast and the Southeast China coast.
Important findings Our findings reveal noteworthy disparities in tree height between Guangxi coastal mangroves and those found along the Southeast China coast. These variations in tree height are associated with significant differences in environmental factors between these regions. Specifically, Guangxi exhibits the highest mean annual precipitation, mean tidal range, and soil salinity, while recording the lowest levels of soil pH, soil total nitrogen content, and total phosphorus content. Upon closer analysis, we identified significant correlations between various environmental factors and mangrove tree height. Notably, mean tidal range, soil pH, and soil salinity displayed significant negative associations with mangrove tree height, whereas mean annual temperature, soil density, soil total nitrogen content, and soil total phosphorus content showed significant positive correlations. The results derived from structural equation models highlighted the paramount influence of mean tidal range, total soil phosphorus content, and soil pH on mangrove tree height. Mean annual precipitation and mean annual temperature directly impact the radial growth of mangroves or indirectly influence tree height by regulating the interactions among other environmental factors. Further examination using linear mixed-effects models demonstrated that the mean annual temperature, mean tidal range, and soil salinity emerged as the primary limiting factors affecting the radial growth of mangroves along the coast of Guangxi. In contrast, soil factors predominantly constrained the radial growth of mangroves in the Southeast China coastal areas (excluding Fujian).

Aims Nighttime sap flow can be lost through the leave stomata as nocturnal transpiration or stored in the stem as nocturnal refilling. Distinguishing transpiration and refilling from nighttime sap flow has been a challenging and pressing problem that needs to be addressed. Although the water-refilling forecasting method is widely used due to its convenience, its accuracy is highly questionable.
Methods To systematically analyze the accuracy and applicability of four water-refilling forecasting methods for the division of nighttime sap flow components, we conducted a study using Populus tomentosa as the test material. The thermal dissipation probe (TDP) were utilized to measure the nighttime sap flow. By combining the accuracy advantage of the height difference method in stem water-refilling with that of the water-refilling forecasting method in nighttime transpiration, we compared and analyzed the estimation effects of the four commonly used water-refilling forecasting methods in this study.
Important findings In terms of estimating the amount of the nocturnal transpiration using the four methods based on sap flow at different heights, only the linear decay model method (Line Method) showed no significant difference, while the other methods exhibited large deviations. When comparing the estimated stem water refilling using the four water-refilling forecasting methods with the results calculated by the height difference method, only the prediction method based on transpiration inversion (Et method) showed a significant difference, while the other methods did not. Additionally, among the four water-refilling forecasting methods, the Line method had the smallest deviation. Thereby, we propose using the sap flow height difference method for water-refilling forecasting to divide nighttime sap flow into three components, namely stem water-refilling, canopy water-refilling, and nocturnal transpiration. This method improves the estimation accuracy of stem water-refilling below the canopy by applying the height difference method. Furthermore, it enhances the accuracy in differentiating canopy water-refilling and nocturnal transpiration through the Line method with the smallest error. Using the new method, the calculated amount of nocturnal refilling was approximately 76.5%, which was 19.8%-26.5% higher than the findings of existing studies. The responses of the divided nighttime sap flow components to environmental factors indicated that vapor pressure deficit (VPD) and shallow soil water content were the main factors influencing nocturnal refilling. The proportion of nocturnal transpiration in nighttime sap flow exhibited a negative and nonlinear correlation with VPD.

Aims The objective of this study was to explore the seasonal variations of the rhizosphere effects of woody plants and their driving factors, and to assess the importance of plant functional traits in the control of rhizosphere processes.
Methods We collected paired rhizosphere and bulk soils of the dominant tree species of two main types of vegetation in Dongling Mountain, Beijing, Betula platyphylla forest and Quercus mongolica forest. Soil physiochemical properties, microbial biomass, carbon and net nitrogen mineralization rates, extracellular enzyme activities and vector characteristics of rhizosphere and bulk soils, as well as plant root and leaf functional traits, in spring (May), summer (July), autumn (September), and winter (December) of 2017 were measured to analyze the seasonal dynamics of rhizosphere effects and their driving factors.
Important findings (1) There were significant differences in soil pH, NH₄⁺-N, microbial biomass, carbon and net nitrogen mineralization rates, extracellular enzyme activities and vector characteristics between rhizosphere soil and bulk soil, and these rhizosphere effects were mainly positive. (2) The rhizosphere effects had significant seasonal dynamics, usually being strongest in autumn. (3) There were often significant correlations between rhizosphere effects and plant root and leaf functional traits. Among them, fine root biomass was significantly and positively correlated with the rhizosphere effect on contents of extractable organic carbon, soil total carbon and total nitrogen. Leaf dry matter content and leaf carbon and nitrogen ratio were significantly and positively correlated with the rhizosphere effect on microbial biomass carbon content, microbial biomass nitrogen content, carbon mineralization rate, and acid phosphatase activity. These results showed that the functional traits of plants were of great significance in rhizosphere processes. In the temperate deciduous broadleaf forest in Dongling Mountain, the highest belowground carbon allocation of plants leads to an increase in the biomass and activity of rhizosphere microorganisms in autumn, which makes the rhizosphere effect of microbial biomass and activity in autumn higher than that in other seasons.

Aims Soil available nitrogen (N), generated from a series of soil mineralization processes, is a major limiting factor of terrestrial ecosystem productivity. Soil N availability depends on soil microorganisms, vegetation types, and soil physical and chemical properties. Soil microorganisms are very sensitive to environmental changes, especially the temperature change, which is closely related with microbial growth and reproduction. Therefore, it is important to understand the temperature sensitivity (Q₁₀) of microbial regulation of N mineralization rates in a large spatial scale for predicting the impacts of global climate changes on terrestrial ecosystem productivity.
Methods Three types of grasslands (namely meadow steppe, typical steppe, and desert steppe) were selected in Nei Mongol Plateau, Loess Plateau, and Qingzang Plateau, respectively. Soil net N mineralization rates were measured at different temperatures in the laboratory, and then Q₁₀ of N mineralization rates were calculated across different grassland types. Relative parameters, including soil microbe, soil physical and chemical properties, were also analyzed.
Important findings (1) The highest Q₁₀ of soil net N mineralization rates was found in all of three grassland types of Loess Plateau than those of Nei Mongol and Qingzang Plateaus. (2) The Q₁₀ values of soil net N mineralization rates in the meadow steppes and typical steppes on the Loess Plateau and Nei Mongol Plateau were significantly higher than those in the desert steppes, while on the Qingzang Plateau, the values in the alpine meadow steppes were significantly lower than that in the alpine typical steppes and alpine desert steppes. (3) Q₁₀ values of soil net N mineralization rates was closely correlated with soil microbial biomass carbon content across different grassland types. (4) The spatial pattern of Q₁₀ is jointly regulated by microorganisms, soil texture and substrate. The results of this study provide important data for understanding of the response of soil N cycle to global change in different grassland types in China, which is valuable for optimization of N cycle models of terrestrial ecosystems in the future.

Located in the northeast of the Qingzang Plateau, the Qaidam Basin is a huge plateau-type closed basin. The vegetation is dominated by desert, including swamp wetlands, halophytic meadows and montane grasslands. In order to show the species composition, community characteristics and distribution pattern of vegetation on the Qaidam Basin in more details, this study used the field data of the Second Tibetan Plateau Scientific Expedition and Research of 2022 and the Comprehensive Scientific Investigation of the Data-scarce Area of the Qinghai-Tibet Plateau of 2014, including 157 sample plots and 458 sample plots, which are integrated into the sample data set of plant communities in Qaidam Basin. Through the collation and compilation of data, a total of 185 species information was obtained, among which the families with the largest number of species were Asteraceae (39 species), Poaceae (33 species), Fabaceae (17 species), Amaranthaceae (16 species) and Brassicaceae (10 species), and the genera with the largest number of species were Stipa, Artemisia, Astragalus, Oxytropis and Saussurea. The composition of plant life forms is dominated by herbs, accounting for 78.37%. The species of middle Asia account for 41.62% of the geographical composition of the flora. Based on the phytocoenological-ecological principles, 157 sample plots can be classified into 4 Vegetation Formation Groups, 7 Vegetation Formations, 11 Vegetation Subformations and 40 Alliances. This data set can provide the most original basic data for the in-depth exploration of vegetation characteristics in the Qaidam Basin, the compilation and research of the Vegegraphy of China, and the mapping of the Qingzang Plateau and the national vegetation map.