Nutrient resorption (NuR) is the key strategy for plant to cope with environmental stresses and optimize nutrient use, and is essential for maintaining plant nutrient economy and ecological functions. This paper reviews the mobilization and transfer pathways of nutrients during leaf senescence, and summarizes the general patterns of nutrient resorption efficiency (NuRE) across elements, organs, growth stages, plant functional groups, and ecosystems, and examines the regulatory roles of genetic traits (e.g., structural tissues, leaf longevity) and environmental factors (e.g., climate conditions, soil nutrients, nitrogen (N) and phosphorus (P) deposition) on NuRE and their ecosystem-level effects. Future research directions are also proposed. Previous studies have shown that N mobilization is primarily achieved via proteolysis, while P mobilization involves the degradation of nucleic acids and phospholipids, along with the release of inorganic phosphate (Pi) from vacuoles. Elements with high mobility and high physiological demand (e.g., N, P, potassium) exhibit significantly higher NuRE than those with low mobility and low demand (e.g., calcium, iron, aluminum). Leaves, being metabolically active organs, show higher NuRE than roots and stems. Plant NuRE varies dynamically with developmental stages, peaking at maturity. Herbaceous and deciduous plants, owing to their lower proportion of structural tissues, have higher NuRE than woody and evergreen species. NuRE in tundra and wetland ecosystems is generally higher than in forests and grasslands, with marked variations across climatic zones. Genetic traits set the physiological upper limit of NuRE by constraining nutrient mobilization capacity, whereas environmental factors drive its dynamic changes, with marked increasesenhancement under nutrient-poor conditions. NuR interacts with below-ground nutrient acquisition strategies through synergistic or trade-off relationships, jointly modulated by soil nutrient availability and climate. The interspecific variability and phenotypic plasticity of NuRE play important roles in regulating nutrient cycling, community assembly, and ecosystem stability. Future research should integrate molecular approaches with long-term field experiments to elucidate the adaptive mechanisms of NuRE under multiple environmental stresses and its feedback effects on ecosystems, thereby providing a scientific basis for addressing global change and optimizing ecosystem management.

Mycorrhizae are widespread symbiotic associations that play a vital role in plant growth, community assembly, and soil nutrient cycling. In the context of global change, changes in mycorrhizal fungi community composition and function profoundly affect soil carbon decomposition and the state of carbon sources and sinks. Although mycorrhizae have been extensively studied, our understanding of the mechanisms by which different mycorrhizal types regulate soil carbon sequestration and decomposition under climate warming remains limited, largely due to their complex interactions with other soil components. By integrating relevant cutting-edge research results, this paper discusses the role of different mycorrhizal types, particularly ectomycorrhizal (EcM) and arbuscular mycorrhizal (AM) associations, in soil carbon sequestration. It further explores mechanisms of mycorrhiza- mediated “nitrogen competition” and its impact on soil carbon decomposition. In addition, it analyzes changes in mycorrhizal fungal communities and their contributions to carbon sink dynamics under climate warming. Finally, this paper highlights key directions for future mycorrhiza-related research, to improve our understanding of soil carbon cycling and to advance studies on mycorrhiza-carbon interactions in ecosystems under climate change.

Aims Climate change has led to a marked increase in the frequency of extreme heat events, posing a serious threat to wheat growth. Existing studies have investigated the effects of extreme heat on the photosynthetic processes of wheat (Triticum aestivum), whereas studies on its effects on leaf temperature and the underlying regulatory mechanisms remain relatively limited.

Methods In this study, three widely cultivated wheat cultivars in the Jianghuai region—‘Nongmai 77’ ‘Nongmai 88’ and ‘Yangmai 39’—were used as experimental materials. A field-based experimental platform simulating extreme heat conditions was employed, with two treatments established: normal ambient temperature (control) and extreme heat. Continuous measurements of leaf temperature, diurnal variations in stomatal conductance, photosynthetic rate, and relative chlorophyll content were conducted to elucidate cultivar-specific responses of leaf temperature and photosynthesis to extreme heat.

Important findings The results showed that mean air temperature increased by 2.7 °C; however, wheat leaf temperature did not change significantly, resulting in a significant reduction in the leaf-to-air temperature difference during the extreme heat treatment. Under extreme heat conditions, the mean stomatal conductance (g_s) of ‘Nongmai 77’ ‘Nongmai 88’ and ‘Yangmai 39’ increased by 59.3%, 56.7% and 32.4%, respectively, compared with the control. Diurnal analysis indicated that the largest increases in g_s occurred at 13:00 and 15:00, with increments of 67.4% and 26.1%, respectively. Under the coupled conditions of reduced radiation and elevated air temperature, extreme heat significantly increased g_s and leaf transpiration rate, suggesting that wheat may alleviate the adverse effects of high temperature on leaves by enhancing transpiration. Extreme heat had no significant effects on relative chlorophyll content or saturated photosynthetic rate, but it significantly reduced leaf-scale water use efficiency. Overall, wheat leaves exhibited strong acclimation to the extreme heat conditions examined in this study, primarily by enhancing transpiration and increasing latent heat flux to maintain relatively stable leaf temperature and photosynthetic rate, albeit at the cost of increased water consumption and reduced water use efficiency.

Aims Exploring the relationship between individual tree size and carbon sequestration rate in temperate forest communities offers a scientific foundation for understanding tree growth dynamics and enhancing the carbon sink function of these ecosystems.

Methods Using fixed monitoring data of 125 000 standing trees from temperate coniferous and broadleaf mixed forests across different regions of Northeast China, this study analyzed the relationship between tree carbon sequestration rate and tree size. The tree species in each region were classified into four groups based on their life forms and regeneration modes: (1) understory species with L-shaped diameter distribution (UNL); (2) L-shaped sub-canopy species (SUL); (3) bell-shaped sub-canopy species (SUB); (4) canopy species with bell-shaped diameter distribution (CAB). Partial correlation analysis was employed to quantify the impacts of tree size, neighborhood competition, and species diversity on the carbon sequestration rate of individual trees.

Important findings The carbon sequestration rate increased continuously with tree size. Although the trend of carbon sequestration rate with tree size is similar across different tree species groups, growth rates differ, with the CAB group exhibiting the fastest growth and the UNL group the slowest. Tree size is the main factor affecting carbon sequestration rate and is significantly positively correlated with carbon sequestration rate. The effects of neighborhood competition and species diversity on carbon sequestration rate vary among tree species groups, usually showing a significant negative correlation. This study reveals the factors influencing carbon sequestration rates in trees of temperate mixed coniferous and broadleaf forests, highlighting the crucial role of large-diameter individuals in carbon sequestration. Our findings enhance the understanding of tree carbon sequestration dynamics and provide a theoretical foundation for sustainable forest management and the restoration of carbon sink functions.

Aims Changes in precipitation intervals and grassland utilization can substantially influence soil inorganic phosphorus (Pi) fractions.

Methods This study combined field experiments and laboratory analyses to investigate how three grassland utilization methods—grazing, mowing, and enclosure—affect soil Pi fractions in a temperate meadow steppe under different precipitation intervals.

Important findings Under the ambient precipitation regime, aluminum-bound phosphorus (Al-P) content was highest in the mowing grassland, occluded phosphorus (O-P) content was highest in the grazing grassland, and iron-bound phosphorus (Fe-P) and calcium-bound phosphorus (Ca-P) contents were highest in the enclosed grassland. When the precipitation interval was extended, all Pi fractions were highest in the enclosed grassland. Precipitation interval and grassland utilization not only directly altered soil Pi fractions but also indirectly regulated them through changes in soil organic carbon (SOC). Specifically, SOC significantly promoted the accumulation of Al-P and Fe-P by increasing total phosphorus (TP) content and further influenced Pi fractions through its effects on microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP). Within the microbial community, dominant bacterial phyla, including Actinomycetota and Pseudomonadota, were significantly associated with soil properties such as SOC and MBN contents. Among fungal phyla, Chytridiomycota and Basidiomycota showed contrasting relationships with available phosphorus (AP) content, while AP content was significantly positively correlated with O-P content. Overall, changes in precipitation intervals and grassland utilization jointly regulate soil Pi dynamics through physicochemical and microbial pathways, providing a theoretical basis for phosphorus management and ecological restoration in grassland ecosystems.

Aims Dissolved organic carbon (DOC) and hot-water extractable carbon (HWEC) are important components of active carbon pools, which can be released quickly from decomposing litter and assimilated by soil microorganisms at short term. This fundamental biogeochemical process has been found to facilitate soil organic matter formation and biogeochemical processes. Traditional knowledge assumed that litter substrate quality and morphological traits are key regulators of litter decomposition. However, how the release rates of DOC and HWEC, two important labile carbon fractions released through leaching during litter decomposition, are influenced by substrate quality and morphological traits remains unknown. Therefore, this study primarily focuses on clarifying interspecific differences in the release rates of DOC and HWEC during foliar litter decomposition, and on revealing their relationships with litter substrate quality and morphological traits.

Methods Here, we conducted an in situ microcosm decomposition experiment to evaluate the release rates of DOC and HWEC from decomposing litter of 21 tree species over 214 d of decomposition in a subtropical forest.

Important findings We found that both DOC and HWEC release rates varied significantly among litters differing in substrate quality, ranging from 0.014 to 0.123 d^-1 and from 0.017 to 0.130 d^-1, respectively. Both DOC and HWEC release rates were significantly related to cellulose and phosphorus (P) contents, whereas no significant relationships were observed with morphological traits (such as thickness and leaf mass per area (LMA)) or with the initial DOC and HWEC contents. These results suggest that DOC and HWEC release rates from subtropical forest litter were controlled primarily by substrate quality rather than by morphological traits. This finding advances our mechanistic understanding of labile carbon release from litter and its role in soil carbon cycling in subtropical forests.

Aims Gross Primary Productivity (GPP) is a key component of carbon cycle in terrestrial ecosystems, and improving its simulation accuracy is crucial for understanding the variations of carbon dioxide concentration in the atmosphere. Currently, there are numerous global GPP products developed based on different data sources and models, but systematic assessments of their performance in the Qingzang Plateau are lacking.

Methods In this study, we collected GPP data from 17 eddy covariance flux towers on the Qingzang Plateau and comprehensively evaluated the accuracy of 8 global GPP products (GPP_GOSIF, GPP_NIRv, GPP_MODIS, GPP_VPM, GPP_GLASS, GPP_TL-LUE, GPP_PML, and GPP_BESS) in alpine meadows of the Qingzang Plateau using three indicators: coefficient of determination, relative root mean square error, and relative bias.

Important findings The results showed that GPP_VPM and GPP_GOSIF generally exhibited relatively higher accuracy and were more suitable for the alpine meadows of the Qingzang Plateau. Moreover, the accuracy of GPP products varied significantly in space and time. Seasonally, the accuracy was higher in summer and autumn than in spring; in terms of ecosystem types, typical alpine meadow showed better accuracy than other meadow ecosystems; regarding permafrost types, the accuracy was higher in permafrost zone than in seasonal frost zone; in climate zones, semi-humid region demonstrated higher accuracy than semi-arid region; in terms of drought conditions, the accuracy was greater in non-drought months compared to drought months; and with respect to fractional vegetation cover conditions, medium and high vegetation cover stages achieved higher accuracy than low vegetation cover stages. This study reveals the uncertainties of global GPP products in the alpine meadows of the Qingzang Plateau and provides important insights for selecting GPP data and improving GPP simulations in this region.

Aims In recent years, persistently elevated atmospheric ozone (O₃) concentration have not only reduced plant productivity but also disrupted secondary metabolite production, leading to changed chemical signaling, imbalances in local ecological interactions, and impaired precision of symbiotic interactions between animals and plants, as well as to ecosystem service functions.

Methods This study investigated the impact of elevated O₃ on plant chemical signaling and stomatal adaptation by comparing the volatile composition of receptive-phase syconia (the stage when pollinating fig wasps enter the syconium) and leaf stomatal traits of Ficus hispida in natural sites with high and low ambient O₃concentrations in Guangzhou.

Important findings Using gas chromatography-mass spectrometry (GC-MS) analysis, a total of 43 volatile organic compounds (VOCs) were identified across both sites. Of the 32 compounds shared between the two sites, terpenoid compounds were dominant. Furthermore, the high O₃ site exhibited specific oxidized products such as Decanal, Sesquicineole, and Caryophyllene oxide. Non-metric multidimensional scaling (NMDS) analysis revealed significant spatial differentiation in VOCs composition between the two sites (Stress < 0.2). Permutational multivariate analysis of variance (PERMANOVA) identified significant differences in the proportional composition of 12 shared compounds (Germacrene D, α-Amorphene, α-Humulene, (E)-β-Farnesene, α-trans-Bergamotene, (E)-Caryophyllene, β-elemene, β-Cubebene, trans-Linalool oxide, (E)-β-Ocimene, Indole, Hex-(3Z)-enyl acetate) between the sites. These results indicate that plant volatile chemical signals differed markedly between natural sites with high and low O₃concentrations, suggesting that such changes may reflect plant responses or potential adaptive strategies to ambient air conditions, particularly elevated O₃. Meanwhile, in the high O₃ sites, the stomatal length and area of Ficus hispida leaves significantly decreased, along with a reduction in chlorophyll content. This study reveals the changes in volatile chemical signals and stomatal physiological characteristics of Ficus hispida under ambient high O₃ conditions, providing new evidence for understanding how O₃pollution may potentially disrupt plant-pollinator interaction networks by affecting interspecies chemical communication and plant stomatal features.

Aims To investigate the effects of nitrate concentration on anthocyanin accumulation and spatial distribution in Mikania micrantha, and to reveal molecular mechanisms of adaptation to nitrogen fluctuations through secondary metabolic regulation.

Methods Controlled experiments with six nitrate nitrogen (NO₃^--N) concentrations (0, 0.5, 5, 10, 20, 40 mmol·L^-1) were conducted to measure anthocyanin content and spatial distribution in main stems and branches, combined with transcriptome analysis of key metabolic pathway genes and transcription factors.

Important findings The results show that under low nitrogen conditions (0-0.5 mmol·L^-1NO₃^--N), both the main stems and branches accumulated substantial anthocyanins to enhance stress resistance. By contrast, in treatments with medium-to-high nitrogen conditions (5-40 mmol·L^-1NO₃^--N), anthocyanin content in the main stems significantly decreased (by 43.1%-73.7%), turning them light green, while the branches remained red but with reduced anthocyanin levels, indicating a “main stem growth-branch defense” allocation strategy. Transcriptomic analysis revealed that 5 mmol·L^-1NO₃^--N suppressed the expression of key anthocyanin biosynthesis genes (PAL, CHS, CHI, F3′H, ANS, UGFT) in the main stems (downregulated by 39.2%-99.9%), while upregulating lignin synthesis genes (HCT1, CCoAOMT) and terpenoid metabolism genes (TPS11, TPS7). Additionally, nitrate modulated the expression of transcription factors (MYB (HHO₂), bHLH (PIF3)) and sucrose metabolism genes (SPS1), influencing the secondary metabolic network. This study demonstrates that M. micranthadynamically regulates anthocyanin allocation between main stems and branches, potentially to balance growth and stress resistance. This adaptive strategy might be a key mechanism contributing to its successful invasion in environments with fluctuating resource availability.

Aims Recent years have witnessed an acceleration in the degradation of alpine meadows on Qingzang Plateau due to rodent disturbances. While it is widely recognized that the digging and foraging activities of rodents significantly influence plant communities and soil properties, the effects of these disturbances on ecosystem respiration (Re) in alpine meadows, as well as the key driving factors associated with this process, have been seldom examined. The objective of this study is to evaluate the impact of rodent disturbances on soil respiration and to elucidate the underlying mechanisms in an alpine meadow.

Methods The static chamber-gas chromatography technique was employed to measure ecosystem respiration flux over a one-year period, spanning from October 2022 to October 2023. The differences in ecosystem respiration between healthy meadows (HM, control) and zokor-induced mound patches (ZM, treatment) were determined in an alpine meadow located in the northeastern Qingzang Plateau.

Important findings The annual cumulative respiration (Re) flux was observed to be 27.60% lower in the ZM plots compared to the HM plots. During the growing season, the cumulative Re flux in the ZM plots was 28.64% lower, and in the non-growing season, it was 16.39% lower. The difference in temperature sensitivity (Q₁₀) was minimal between the HM and ZM plots on an annual basis (6.11 ± 0.31 for HM and 5.78 ± 0.41 for ZM) and on a seasonal basis (4.13 ± 0.85 for the growing season and 4.10 ± 0.61 for the non-growing season). Notably, the Q₁₀ value during the non-growing season was significantly higher in the HM plots (11.90 ± 1.80) compared to the ZM plots (4.76 ± 1.00). The seasonal variation pattern of Re was consistent across the different treatments. Soil temperature, along with its interaction with soil moisture, significantly contributed to the variation in Re emissions, with soil temperature alone accounting for 59.7% to 85.3% of the observed variations. This study demonstrates that rodent disturbance significantly inhibits respiration in meadow ecosystems, which has important implications for carbon cycling and ecosystem management in grassland environments.

Aims To elucidate the rainfall redistribution characteristics among different plantation types in the mountainous region of Beijing—particularly the interception mechanisms of mixed forests with structurally complex canopies—this study conducted a quantitative analysis of throughfall, stemflow, and canopy interception based on field observations and simulations using the modified Gash model. The primary aim was to assess the model’s applicability under heterogeneous canopy structures and to provide a scientific foundation for regional water management and vegetation configuration optimization.

Methods Field measurements were conducted during the 2021 growing season (June to September) in the mountainous region of Beijing, targeting pure stands of Platycladus orientalis, Quercus variabilis, and their mixed forests. Meteorological and gross rainfall were collected alongside in-situmeasurements of throughfall, stemflow, and canopy interception. The modified Gash model was applied to simulate canopy interception across forest types, followed by a parameter sensitivity analysis to evaluate model applicability.

Important findings (1) Light rainfall events dominated the study period, accounting for 73.5% of gross rainfall. The observed mean proportions of throughfall, stemflow, and canopy interception were 74.15%, 1.89%, and 23.96% for Platycladus orientalis forest; 71.70%, 2.25%, and 26.23% for Quercus variabilis forest; and 68.74%, 2.56%, and 28.70% for the mixed forest, respectively. Throughfall and stemflow were significantly positively correlated with gross rainfall, while canopy interception exhibited a positive power-law relationship with rainfall. (2) The model-simulated canopy interception rates were 21.92%, 23.13%, and 26.47% for Platycladus orientalis forest, Quercus variabilis forest and the mixed forest, with relative errors of 8.52%, 11.82%, and 7.75%, respectively. The model demonstrated good performance across all forest types, with the highest accuracy observed in the mixed stand. (3) Sensitivity analysis indicated a consistent ranking of parameter influence on model output: average evaporation rate > average rainfall intensity > canopy storage capacity > canopy cover > trunk storage capacity > stemflow coefficient. In summary, structural differences among forest types led to distinct rainfall redistribution patterns under similar climatic conditions. The modified Gash model proved applicable to typical plantation and mixed forests in the mountainous areas of Beijing and can effectively support studies on forest water balance in the region.

Aims Pressure-volume traits of leaf and fine roots play a crucial role in the hydraulic architecture of trees, but the differences between leaf and root turgor loss point (TLP) and their relationship with the stomatal closure point (Ψ_close) among tree species are not fully understood. Moreover, the potential relationships between leaf and root morphological characteristics, non-structural carbohydrate (NSC) contents and turgor loss traits is not clear across species. This study in order to address this issue and provide a theoretical basis for the selection of tree species for afforestation in the loess hilly region.

Methods Five coniferous tree species and seven broadleaf tree species commonly occurring in the loess hilly region were selected, to analyze the differences in their Ψ_close, TLP and NSC contents of leaves and fine roots as well as the relationship between leaf and fine root morphology traits, NSC content and TLP.

Important findings The TLP of fine roots of coniferous tree species was 47.86% significantly lower than broadleaf species, while Ψ_close was 39.04% significantly higher than broadleaf species. The Ψ_close of coniferous species is 48.06%, 33.82% significantly higher than TLP of leaves and fine roots but the TLP of leaves and fine roots in broadleaf species was 19.83%, 37.70% higher than Ψ_close. The water capacity of leaves and fine roots of coniferous tree species was significantly lower than broadleaf species, with the elastic modulus and the soluble sugar content were significantly higher than broadleaf species. Besides, the leaf TLP of all tree species was significantly lower than that of fine roots. Correlation analysis showed that significant positive correlations existed between specific leaf area and leaf TLP, specific root length and fine root TLP, as well as leaf TLP and fine root TLP for all tree species. The above results show that coniferous species had stronger turgor pressure maintenance ability and greater stomatal sensitivity, which makes it easier to maintain water balance under drought conditions. In contrast, broadleaf species can maintain stomatal conductance even when the water potential dropped below TLP, showing stronger tolerance to stomatal dehydration, but more susceptible to hydraulic failure. The results of this study also suggests that there were differences in the relationships of turgor loss points and stomatal closure points between coniferous and broadleaf tree species. This study reveals the differences in the pressure-volume traits and stomatal regulation of leaves and fine roots among different tree species, and clarifies the species-specific differences in drought adaptability, which could help to predict the selection of afforestation tree species in the context of global change.

Aims Leaves, exhibiting the highest ecological plasticity, are sensitive to environmental change. They also act as both the hydraulic bottleneck and safety valve against hydraulic dysfunctions. Populus euphratica is well-adapted to extreme arid environments and possesses heteromorphic leaves that are distributed differentially along the vertical heights of the tree. This study aims to explore the variations of hydraulic and anatomical traits of heteromorphic leaves and their interaction, as well as to elucidate the mechanisms underlying morphological divergence along gradients of groundwater depth (GWD) and vertical heights. The findings are expected to enhance our understanding of their adaptation strategies to adverse environments and provide a scientific basis for the protection and restoration of desert P. euphratica forest in the context of global change.

Methods Through a community survey along a gradient of GWD, we measured the hydraulic, structural and morphological traits of three different leaf shapes from adult P. euphratica trees at different vertical heights within canopy. We then examined the differences in morphological traits, hydraulic traits (e.g., hydraulic conductance, vein, stomata) and anatomical structures, and analyzed their interrelationship.

Important findings (1) Under different GWD conditions, significant differences were observed in the morphological, hydraulic and anatomical traits of leaves with the same shape, while under the same GWD, the three heteromorphic leaves exhibited notable variations in these traits across different canopy heights. For a given leaf type, traits such as minor vein density, loopiness of veins, free-end density, vessel density, leaf thickness, palisade-to-spongy mesophyll ratio, epidermal and cuticular thickness all increased with greater GWD, similarly, these functional traits (e.g., minor vein density, vessel density and palisade-to-spongy mesophyll ratio) increased along vertical canopy height under the same GWD. Deeper GWD and higher canopy positions were associated with enhanced vein development and more xeromorphic anatomical structures in heteromorphic leaves. (2) Compared with the heteromorphic leaves in the lower-middle canopy, the serrated broad-oval leaves in the upper canopy are wider and thicker, with more developed palisade tissue and complex venation networks. These structural adaptations have evolved in response to intense light, high temperatures and increased transpiration demand, resulting in a more efficient hydraulic system and a robust defensive architecture. This enhances the water transport efficiency and water retention capacity, thereby improving embolism resistance and drought tolerance. (3) The leaf length-width ratio (LI) and dissection index (DI) were significantly correlated with most hydraulic and anatomical traits. Hydraulic traits contributed more to leaf morphological variation than anatomical features, with the interval distance between veins, closed-loop area, vein density and proportion of minor veins playing predominant roles in shaping leaf morphology. (4) Most leaf morphological traits showed a highly significant correlation with hydraulic path length and leaf attachment height. Hydraulic path length mediates leaf morphological variation (LI, DI) by influencing hydraulic and anatomical structures, indicating that hydraulic constraints along the vertical canopy gradient are a key factor driving leaf shape differentiation in P. euphratica.(5) The coupling between hydraulic traits and anatomical structures enhances hydraulic functionality and boosts stress resilience in P. euphratica. Leaf shape differentiation represents an ecological strategy evolved by the species to adapt to contrasting hydraulic environments throughout its life cycle.

Aims To clarify how water use in rubber (Hevea brasiliensis) plantations varies across leaf phenophases and to identify the key environmental drivers of stem sap flow dynamics, thereby improving the assessment of impacts on regional water cycling and informing water-resource management.

Methods We continuously monitored stem sap-flux density (F_d) with the thermal dissipation probe (TDP) method across four phenophases—defoliation, early leaf-expansion, mid leaf-expansion, and late leaf-expansion. Environmental variables (soil and atmospheric temperature and humidity, etc.) were recorded synchronously. We then applied XGBoost coupled with the SHAP interpretability framework to quantify the relative contributions of candidate drivers.

Important findings (1) Phenology strongly modulates water use: F_d and tree-level water use differed significantly among phenophases, in the order of late leaf-expansion > mid leaf-expansion > defoliation > early leaf-expansion; the daily mean F_d in late leaf-expansion was 4.4-6.1 times that of the leafless periods (defoliation and early leaf-expansion), indicating a significant increase in water consumption. (2) The dominant environmental drivers showed dynamic shifts with phenology. During defoliation, air temperature (T_a; 32.39%) and volumetric soil water content (VWC₅; 24.38%) at 5 cm depth were the primary drivers. In the early leaf-expansion, soil temperature (T_s; 36.61%) and photosynthetically active radiation (PAR; 19.55%) prevailed. During mid leaf­expansion, vapor pressure deficit (VPD; 52.16%) become dominant. In late leaf-expansion, T_a re-appeared as the key driver (62.75%). Mechanistically, leaf phenology modifies canopy leaf area (and thus canopy conductance), reshaping the soil—plant—atmosphere water-potential gradient, so that limitation of water use shifts from soil water availability and temperature toward atmospheric evaporative demand; this shift amplifies phenophase-dependent differences in sap flux and water consumption. These findings delineate the phenology-dependent dynamics and driver transitions of sap flow in H. brasiliensis, and provide an evidence base for water resource management and strategy development in tropical plantations.

Aims Root is the key organ for plants to absorb nutrients and water. Investigating the root interactions of mixed-species trees is of great significance to reveal the mechanism underlying the enhanced productivity in mixed-species stands.

Methods A pot experiment was set up by co-planting Cunninghamia lanceolata and Michelia macclurei seedlings. We established three root interaction modes: no separation (NB), 30 μm nylon film separation (MB) and plastic membrane separation (PB), and two controls: C. lanceolata monoculture (MC) and M. macclureimonoculture (MM). The photosynthetic parameters, root morphology and physiological characteristics of seedlings were determined.

Important findings The results showed that: 1) The mixed planting significantly increased stomatal conductance, transpiration rate and intercellular CO₂concentration, but did not change the net photosynthetic rate of M. macclurei; 2) Compared with monoculture treatment, mixed planting significantly increased root length, root dry mass, root surface area, root average diameter, root volume, root tissue density and root tip number of C. lanceolata; 3) The root length and root surface area of M. macclurei were significantly higher under PB than other treatments; 4) The mixed treatment significantly reduced the length, surface area and volume of big fine roots (0.5 < D ≤ 2.0 mm, D is the root diameter) of M. macclurei; 5) Under mixed planting treatment, the soluble protein content, malondialdehyde content and antioxidant enzyme activity of C. lanceolata increased significantly. Mixed planting treatment significantly decreased the soluble protein content and malondialdehyde content of M. macclurei, but significantly increased the activity of antioxidant enzymes. The findings clarified the effects of interspecific root interactions between C. lanceolata and M. macclurei on the seedling root growth, further revealed mechanisms driving productivity enhancement in mixed-species plantation. Results demonstrated that C. lanceolataand M. macclurei exhibited different response patterns in C. lanceolata-M. macclurei mixed planting system. This study revealed the mechanism about the species-specific root interaction and facilitation effect in mixed plantation. Our study provides a scientific basis for management of C. lanceolata-M. macclurei mixed forest and for implementing precision silviculture to enhance quality management.

Aims Alpine wetlands play an important role in maintaining biodiversity and replenishing water sources. Exploring plant adaptability to the environment is the basis for effective prevention of wetland degradation and preservation of wetland ecosystem functions. However, it is unclear how soil moisture and light intensity, as two crucial factors for plant growth, interactively affect plant ecophysiology in alpine wetlands. Therefore, the present study explored the adaptation strategies of plants to changes in light intensities and soil moisture.

Methods A factorial experiment with two light intensities (ambient light and 60% ambient light) and three soil moisture levels (30%, 55%, and 85%) was conducted on the dominant species Carex muliensis in the Zoigê alpine wetland, during which growth, morphology, and photosynthetic fluorescence indicators were measured.

Important findings According to the leaf economics spectrum theory, specific leaf area (SLA) and photosynthetic rate can serve as two key strategy indicators for assessing plant adaptation to variations in light availability and soil moisture. Results revealed that: 1) Under ambient light conditions, the SLA and photosynthetic rate of C. muliensis increased with increasing soil moisture, reaching maximum values of 170.00 cm²·g^-1 and 75.01 μmol·m^-2·s^-1, respectively. The plant adaptation strategy shifted from a conservative to an acquisition strategy along the water gradient. 2) Shading alleviated drought stress to a certain extent. The maximum SLA and photosynthetic rate of C. muliensis under moderate water conditions were 234.98 cm²·g^-1 and 7.59 μmol·m^-2·s^-1, respectively. In this water condition, plants adopted the acquisition strategy, while it switched to be conservative with low SLA and low photosynthesis rate when soil humidity changed. 3) Compared to the ambient light, shade inhibited growth and reduced physiological activity of C. muliensis. In conclusion, the adaptive strategy of C. muliensis under different soil moisture conditions is closely linked to light intensity. It provides a theoretical basis for guiding the ecological restoration of degraded alpine wetlands under complex environmental conditions.

Aims Approximately 19% of the photon flux density in sunlight is contributed by far-red light (FR, 700-800 nm), which plays a crucial role in plant photosynthesis. However, commonly used gas exchange systems are typically equipped with internal light sources that provide only blue (400-500 nm) and red (R, 600-700 nm) wavelengths, with little or no emission in the far-red region. This omission may lead to an inaccurate estimation of photosynthetic parameters and an underrepresentation of a plant’s true photosynthetic capacity under natural light conditions. To address this issue, the present study investigated the effects of supplementing far-red light into short-wavelength measuring light on photosynthetic parameters, and further examined whether such effects are influenced by growth light intensity.

Methods One-year-old seedlings of the shade-tolerant tree species (Quercus variabilis) were used as the study material. A two-factor factorial design was applied to investigate the combined effects of growth light intensity and measuring light quality on photosynthetic parameters. Two growth light environments with identical spectral characteristics (R/FR = 1.4 ± 0.01) were established: low light (LL, photosynthetic photon flux density (PPFD) at 30% of full sunlight (100% = 1 500 μmol·m^-2·s^-1)) and high light (HL, PPFD at 70% of full sunlight). Seedlings were grown and acclimated under these conditions for five weeks. Then two measuring light treatments were applied: (1) short-wavelength light (SWL, 1 100 μmol·m^-2·s^-1 PPFD); and (2) short-wavelength light supplemented with far-red radiation (SWL + FR, 1 100 μmol·m^-2·s^-1 PPFD + 300 μmol·m^-2·s^-1 far-red, PFD_FR), maintaining an R/FR ratio of 1.4. For each measuring light condition, steady-state photosynthetic parameters, and chlorophyll fluorescence kinetics, dark-light-dark induction curves of photosynthesis and fluorescence, and CO₂ response curves were measured.

Important findings The addition of far-red light into the short-wavelength measuring light significantly enhanced most photosynthetic parameters of Q. variabilis seedlings compared to SWL alone, and the extent of these effects varied with growth light intensity. For steady-state photosynthetic parameters, FR supplementation increased the maximum steady-state net photosynthetic rate by 31% under low light and by 25% under high light, while maximum steady-state stomatal conductance rose by 20% (LL) and 45% (HL) relative to SWL alone. Similarly, the effective quantum yield of photosystem II photochemistry increased by 62% (LL) and 29% (HL); and the photochemical quenching coefficient rose by 63% (LL) and 25% (HL) compared to measurements without FR. Non-photochemical quenching also showed increases of 24% (LL) and 7% (HL) respectively, versus non-FR conditions. However, there was no significant difference in the maximum carboxylation efficiency between FR-supplemented and control treatments. In photosynthetic induction responses, the addition of far-red light into the measuring light significantly enhanced the maximum slope of both photosynthesis and stomatal conductance induction curves, while simultaneously shortened the response time and lag time in leaves grown under low light (LL) compared to SWL alone. By contrast, leaves grown under high light exhibited little response to FR supplementation. Furthermore, the addition of FR into the measuring light markedly increased the maximum electron transport rate in CO₂ response curves by 22% and 24% under low and high light conditions, respectively, relative to non-FR conditions. This study demonstrated that adding far-red light during photosynthetic measurements significantly altered most photosynthetic parameters in Q. variabilis seedlings. The primary mechanism is that far-red light could optimize energy distribution between photosystem I and photosystem II, enhance electron transport efficiency, and improve overall light use efficiency, which collectively regulate photosynthetic performance. Incorporating far-red light into measuring systems provides more accurate representations of plant photosynthetic performance under natural light spectra than traditional far-red-deficient measurement systems. Consequently, standardizing the measurement light spectrum, especially by maintaining an adequate far-red component, can significantly improve the ecological validity of derived parameters and data comparability. These findings are important for plant physiological research and field applications. However, the current study was limited to potted seedlings of a single tree species under a fixed R/FR ratio. Future investigations should therefore be extended to multiple plant species and a broader range of R/FR combinations to further validate the universality and applicability of far-red light mediated photosynthetic regulation.

Chinese ironwood (Parrotia subaequalis) is classified as a first-class protected plant species in China and represents a rare example of plant species with extremely small populations. The Zhejiang Hynobius amjiensis National Nature Reserve serves as one of the key distribution sites for this critically endangered plant species and is also among the earliest sites to conduct research on P. subaequalis. However, investigations into the population characteristics of P. subaequalis within this reserve remain relatively insufficient, and there has yet to be a systematic exploration of the community characteristics associated with its primary habitat. This study established 22 plots that represent the primary habitat communities for this species within the reserve. Comprehensive investigations were conducted to assess both species composition and quantitative attributes of these communities, alongside an analysis of various community types and their respective characteristics. Furthermore, by examining the diameter class structure, compiling a static life table, drawing a survival curve, and calculating dynamic change indices of the P. subaequalis population, this study explored the intricate aspects of population dynamics concerning P. subaequalis. The results indicated that a total of 1 457 woody plants (including 121 individuals of P. subaequalis) with a diameter at breast height (DBH) of ≥ 1 cm were recorded, representing 106 species from 82 genera across 44 families. The 22 plant communities in their primary habitats were classified into 14 alliances. The population of P. subaequalis exhibited a relatively low proportion of seedlings and saplings with DBH < 7.5 cm, comprising only 22.31% of the total number of individuals. This observation suggests significant challenges regarding population renewal. The species survival curve conformed to the Deevey-II type. Notably, there were significant differences in population dynamic indices between natural and disturbed conditions, revealing an insufficient capacity for the population to withstand external disturbances. In light of these findings, this study recommends enhancing in-situ conservation efforts for P. subaequalis populations within the Zhejiang Hynobius amjiensis National Nature Reserve. Additionally, it is essential to implement management and protection measures specifically targeting seedlings and saplings of P. subaequalis while conducting long-term monitoring of its populations along with their associated primary habitat communities.