Ecology explores the fundamental principles and dynamics of macro living-systems and provides the scientific foundation of ecological civilization. China has separated the ecology as an independent subject from the biology subject to better promote its development. This transition calls for a broader conceptual framework for the subject of ecology. In this article, we define “ecology” as “the science that studies the structures, functions and dynamics of macro living-systems”, which provides a theoretical guidance and practical solutions for maintaining sustainable biosphere. Current ecology encompasses multiple living-system levels from molecules to the biosphere, with its core focus on five key levels: individual, population, community, ecosystem, and landscape. The sub-subject system of ecology comprises seven core disciplines: Plant Ecology, Animal Ecology, Microbial Ecology, Ecosystem Ecology, Landscape Ecology, Restoration Ecology, and Sustainable Ecology. Over nearly 160 years, ecology has generated seminal concepts and landmark theories that have profoundly influenced natural science advancement and human civilization. Current ecology is characterized with four distinctive features: (1) expansion of research scope to both macro- and micro-scales; (2) broad adoption of methodologies from other fields such as molecular biology or information science; (3) increased attention to field-based experiments and observational networks, with platforms now established at regional and global scales; and (4) enhanced emphasis on applied ecology to address ecological challenges of human society. Serving as both a natural philosophy for comprehending the living world and a praxeology for conserving and utilizing nature, ecology can be framed through five core perspectives: (1) hierarchical perspective (recognizing the multiple structural levels of living systems), (2) holistic perspective (approaching ecological phenomena from an integrative viewpoint), (3) systematic perspective (viewing the living world as interconnected networks), (4) evolutionary perspective (understanding life systems as dynamic and evolving), and (5) practical perspective (developing solutions for sustainable stewardship of nature). Methodologically, ecological research relies on four principal approaches: field investigations, laboratory and in-situ controlled experiments, model simulations, and meta-analyses. Although ecology and its branches possess robust theoretical frameworks, they lack their own technological systems. Consequently, the development of core ecological technologies is essential to promote continued vitality and progression of the ecology discipline.

In line with the evolution of fundamental concepts and theories in the discipline, ecology persists in developing its conceptual and theoretical framework. This paper puts forward and expounds on the potential foundational principles of ecology through the application of analytical, synthetic, and dialectical methods. (1) Scale-dependent principle. The regularities and mechanisms governing ecological processes are contingent upon spatial and temporal scales, as well as ecological organization or hierarchy. Corresponding concepts and theories are typically formulated for specific scales. Constructing a comprehensive theory that spans all scales continues to pose a substantial challenge. (2) Dynamic equilibrium principle. Considering the openness of ecosystems, especially their biological and ecological metabolic characteristics, a specific stage in an ecological process or a particular state of an ecosystem can only attain a dynamic equilibrium. The nature of this equilibrium depends on the system’s inherent regulatory capacity, encompassing both resistance and resilience, as well as the stage of succession. Typically, the climax of ecological succession signifies a stable equilibrium state for the ecosystem or community. Following this climax, the system may possibly shift into a non-equilibrium condition. (3) Feedback interaction principle. Feedback interactions play a crucial role in determining and regulating the nature and function of ecological processes and systems. Positive feedback can lead to unidirectional amplification or diminishment of these processes, while negative feedback generally maintains the equilibrium of ecological systems, including biological homeostasis. The dynamic balance between positive and negative feedback mechanisms within the ecological-evolutionary process governs the stability or instability of ecosystems. In actuality, the scale-dependent principle addresses the overarching cognitive perspective of ecological phenomena and processes, while the dynamic equilibrium principle focuses on the intrinsic nature of ecological processes or states. The feedback interaction principle, underscores the core issues in ecology, particularly the interactions among living organisms and between living organisms and non-living entities. These fundamental ecological principles or rules exhibit both relative independence and a degree of compatibility, yet they are inherently and inevitably interconnected. Understanding and establishing the fundamental principles of ecology will not only facilitate the progress of ecological concepts and theories but also contribute to the development and improvement of the scientific framework of ecology.

Aims Microbial nitrogen use efficiency (NUE) refers to the ratio of nitrogen used by microorganisms for growth to total organic nitrogen absorbed, which is a key regulator of the soil nitrogen cycle. The ¹⁸O-H₂O method and eco-enzyme stoichiometric model are the most common techniques employed to estimate microbial NUE. However, the impact of nitrogen enrichment on microbial NUE in forest soils remains to be elucidated, which would significantly impede the accurate prediction of soil nitrogen supply.

Methods In this study, we sampled the soils from subtropical Castanopsis faberi forests and used urea to simulate atmospheric nitrogen deposition. In total, three levels of nitrogen additions were set up, including control (CK, 0 kg N·hm^-2·a^-1), low nitrogen (LN, 40 kg N·hm^-2·a^-1), and high nitrogen (HN, 80 kg N·hm^-2·a^-1) treatments. The ¹⁸O-H₂O method and eco-enzyme stoichiometric model were used to compare the differences in soil microbial NUE under different nitrogen enrichment levels. Furthermore, soil physicochemical properties, microbial biomass, extracellular enzyme activity, and stoichiometric imbalance were also measured to explore the factors that influence the response of microbial NUE to nitrogen enrichment.

Important findings The results showed that the microbial NUE, as determined by two different methods, exhibited a decline with the increase of nitrogen enrichment. The vector angle values of different nitrogen treatments were all greater than 55°, indicating that soil microorganisms in this study area were generally phosphorus limited, but nitrogen enrichment did not exacerbate the phosphorus limitation. On the contrary, nitrogen enrichment has a significant negative effect on microbial carbon and nitrogen imbalance, and a positive correlation was observed between microbial NUE and microbial carbon and nitrogen imbalance. In summary, the nitrogen enrichment may have a detrimental effect on soil nitrogen storage in subtropical forests, highlighting the necessity to enhance soil nitrogen storage by means of regulating the soil stoichiometric balance in these forests.

Aims Soil nitrogen mineralization, nitrification and microbial nitrogen immobilization are key processes in soil nitrogen cycle, which have an important impact on soil nitrogen supply. Exploring the spatial variations in soil nitrogen transformation rates of forest may contribute to in-depth understanding of forest soil nitrogen dynamics and forest ecosystem productivity.

Methods In this study, we integrated and analyzed 685 observations from 78 published papers, and aimed to analyze the rate characteristics of soil gross nitrogen mineralization, gross nitrification and microbial nitrogen immobilization of forest ecosystem and the main influencing factors.

Important findings The results showed that: (1) The average rate of soil gross nitrogen mineralization, gross nitrification and microbial nitrogen immobilization of forest ecosystem were (6.65 ± 0.61), (1.99 ± 0.21) and (8.10 ± 1.45) mg N·kg^-1·d^-1, respectively. (2) The soil gross nitrogen mineralization rate and gross nitrification rate differed significantly among various forest types. Higher gross nitrogen mineralization rates were observed in tropical forest and temperate coniferous forest, while lower rates in subtropical broad-leaved forest and subtropical coniferous forest. The microbial nitrogen immobilization rates were higher in temperate coniferous and broad-leaved mixed forest, but was lower in subtropical coniferous and broad-leaved forest. (3) Soil gross nitrification rates exhibited no significant differences among various forest types. (4) The spatial variations in soil gross nitrogen transformation rates were main regulated by soil total nitrogen content and microbial biomass. Overall, the gross nitrogen transformation rates exhibited large spatial variability across global forest, and they were mainly affected by substrate supply and microbial biomass.

Aims Ecosystem reactive nitrogen (N) and phosphorus (P) inputs induced by recent industrial and agricultural development can modify soil carbon (C) storage capacity by affecting soil aggregate structure and stabilization. However, observational studies on modeling the effects of N and P deposition on soil aggregates are still lacking in subtropical regions, with research on P-N interactions being comparatively scarce.

Methods In order to investigate how ecosystem N enrichment and its interactions with P deposition affect C sequestration mechanisms in soil aggregates, N and P addition experiments were conducted for 7 consecutive years in a subtropical forest in southern China. Sample plots of four N addition types were established (control: CK, 0 kg N·hm^-2·a^-1; low N addition: LN, 50 kg N·hm^-2·a^-1; N addition: NA, 100 kg N·hm^-2·a^-1; N and P addition: N+P, 100 kg N·hm^-2·a^-1 + 50 kg P·hm^-2·a^-1). Soil properties, soil aggregates and their C, N contents, and C, N stable isotopes composition of aggregates at each aggregate level were determined.

Important findings Evergreen broadleaf forest macroaggregates (diameter > 250 μm) were the dominant soil aggregate size, accounting for 83%-87% of the total soil mass, and LN treatment increased macroaggregate formation, mean mass diameter and mean geometric diameter, while NA and N+P treatments marginally reduced soil aggregate stability. N enrichment in this region primarily increased the C and N contents of aggregate, attributable on an increase in the concentration of these elements at each grain level. The added organic matter was predominantly enriched in macroaggregates, which were characterized by a high C to N ratio and rich ¹³C abundance. Conversely, excessive N input was detrimental to the stabilization of soil aggregate structure and C sequestration, in comparison with low N addition. The addition of P did not significantly alter the stability of local aggregates or their C and N components. The total soil C, N, and P contents of evergreen broadleaf forests under N addition did not promote soil aggregate formation, and the decrease in pH significantly promoted the increase of C and N contents of aggregates. The results of this study enhance our understanding of the mechanisms of aggregate change, and thus represent important references for predicting the potential of soil C sinks in evergreen broadleaf forests and other areas with similar conditions under future N and P deposition.

Aims Under the background of global climate change, this study investigated the dynamic characteristics of energy fluxes in Jinyun Mountain’s coniferous-broadleaf mixed forest across different temporal scales and their responses to environmental factors.

Methods We selected the mixed coniferous and broadleaf forests in Jinyun Mountains as the study area, and analyzed the long time series flux data of the mixed coniferous and broadleaf forests in Jinyun Mountains for the years 2020, 2021, and 2023 (data for 2022 are missing) using correlation factor analysis and structural equation modeling based on the data measured by eddy correlation technique.

Important findings (1) At the diurnal scale, net radiation (Rn), sensible heat flux (H), and latent heat flux (LE) exhibited unimodal trends, with their peak values occurring at 14:00 local time, and approaching near-zero values after 19:00. In contrast, soil heat flux (G) displayed a bimodal pattern, reaching its daily minimum prior to sunrise and attaining its daily maximum at 14:00 local time. (2) At the monthly scale, the influence of Rn on energy fluxes increased from April, reached its maximum in July and August, then gradually decreased. The influence of canopy conductance (Gs) on LE followed the same trend. (3) At the growing season scale, Rn was the primary influencing factor for energy flux variations. Correlation factor analysis indicated that Gs had a slight limiting effect on H but a significant limiting effect on LE. However, the plant water balance mechanism exerted the strongest influence. (4) The annual mean Bowen ratios (β) for the three years were 0.69, 0.63, and 0.76, respectively. (5) Influenced by extreme drought, the sensible heat flux at the annual scale exhibited a bimodal trend. This study analyzed the characteristics and influencing factors of energy fluxes in the Jinyun Mountain coniferous-broadleaf mixed forests, revealing the dynamic processes of energy fluxes, quantifying the impacts of environmental factors, and providing a scientific basis for assessing the response of subtropical forest ecosystems to climate change and forest conservation.

Aims Accurate estimation of crop yield is important for agricultural policy formulation. Vegetation canopy reflectance spectra and carbon fluxes are the primary data for monitoring crop growth status. However, there are fewer studies comparing their performance in predicting crop yield.

Methods Here, we explored the capability of various parameters to predict rice (Oryza sativa) grain yield and aboveground biomass using synchronized observations of vegetation canopy reflectance spectra and gas exchange parameters.

Important findings Results showed that vegetation reflectance index outperformed carbon flux parameters in estimating rice grain yield and aboveground biomass, in which the optimal estimation parameter was the near-infrared reflectance of vegetation. The vegetative phase was the optimal estimation phase of rice grain yield and aboveground biomass. Our results could provide critical guidance for cropland yield estimation based on remote sensing data and ground flux data.

Aims This study aims to reveal the effects of soil warming on the fine root growth and morphological traits of subtropical evergreen broadleaf forests in China.

Methods At the Fujian Sanming Forest Ecosystem National Observation and Research Station, we used an in-situsoil warming experiment and cooperated with the method of in-growth core in a Castanopsis kawakamii forest to explore fine root biomass growth and morphological traits during the rainy season (May) and dry season (November). In this study, we sorted fine roots into absorption roots (diameter < 1 mm) and transport roots (diameter 1-2 mm).

Important findings Compared with the control, during the rainy season, soil warming treatment significantly reduced the biomass of absorptive roots by 41.2%, contrasting no changes of transport roots. Soil warming also did not alter the diameter and length of absorptive and transport roots, but specific root length (SRL) and specific root area (SRA) were significantly reduced by 53.2% and 42.9%, respectively, and root tissue density (RTD) was significantly increased by 28.8% in absorption roots. During the dry season, soil warming significantly increased the biomass of absorptive and transportive roots, as well as their root length (increased by 38.5% and 33.5%, respectively). However, the diameter, SRL, SRA, and RTD of absorptive and transport roots did not alter in soil warming treatment during the dry season. These results suggest that fine roots of Castanopsis kawakamii in mid-subtropical forests exhibited higher plasticity to cope with climate changes, such as adjusting absorptive root traits to alleviate the effect of soil warming on the resource absorption and growth during the rainy season, and increasing root length to expand resource absorption space during the dry season. This study provides a scientific basis for understanding the ecological adaptation and resource acquisition strategies of functionally distinct fine roots in subtropical forests under global warming.

Evergreen broad-leaved forest (EBLF) is one of the most typical vegetation types in China, with wide geographical distributions, complex species composition, and diverse community types. The EBLF classification is challenging and has not reached a consistent scheme. Here the recently developed “Ecophysiognomic-floristic vegetation classification system (EcoFloVCS)” was used to the EBLF classification. The high-level units of EcoFloVCS are mainly based on ecophysiognomy, with some considerations of floristic characteristics, including five units (Formation Class, Formation Subclass, Formation Group, Formation, and Division). The middle- and low-levels are mainly based on floristic characteristics, with some considerations of ecophysiognomy and geographical distributions, including four units (Community Class, Order, Alliance and Association). Following the previous EBLF classification in 2013, we had an update and revised classification system applied to China’s EBLF using the EcoFloVCS and the 4th edition of The International Code of Phytosociological Nomenclature. Currently, the EBLF is classified into 3 formations, 3 divisions, 9 community classes, 23 orders, and 58 alliances. For three formations, we introduced shortly their geographic distributions, the dominant species of dominant layers, diagnostic species, and the classifications of the low-level units. Furthermore, we classified the alliances into 69 associations and 339 communities using the currently available plant vegetation data. More information have been added into the EBLF website (http://EBLF.info), and we will keep updates of the EBLF classification system through this website.

Aims Climate change has significantly influenced the evolutionary history of various biological groups. Among these, succulents represent special plant groups adapted to arid conditions. Didiereaceae, a small family within Caryophyllales, consist of about 20 species representing 6 genera and 3 subfamilies. Members of this family are succulent plants found in the arid regions across southern to eastern African as well as Madagascar. However, the link between the family’s evolution and the establishment of arid climates in its habitats remains unclear.

Methods In this study, we reconstructed the phylogenetic relationships among Didiereaceae species based on analyses of six plastid DNA markers (rps16, rpl16, trnL-F, trnT-trnL, trnG-S, trnQ-rps16). Additionally, molecular dating and diversification analyses of the family were also conducted.

Important findings The monophyly of Didiereaceae was strongly supported, and a robust phylogenetic framework for the family was established. The crown age of the family was estimated at about 62.3 million years ago (Ma) in the middle Paleocene. However, the two subfamilies (Didiereoideae and Portulacarioideae) with multiple species began to diverge about 11.1 Ma and 14.9 Ma, respectively, during the mid-late Miocene. Results from diversification analysis further revealed an increased diversification rate shift about 11 Ma. These findings align closely with the timing of the establishment of arid climates (15-10 Ma) in the family’s distribution range. Thus, we suggest that the onset of aridity in southern and eastern Africa and Madagascar during the mid-late Miocene likely played a key role in driving species diversification within Didiereaceae. This study enhances our understanding of the evolutionary history of Didiereaceae and contributes to broader knowledge of species diversification patterns in succulent plants.

Aims Goosegrass (Eleusine indica), one of the world’s malignant weeds, is also a widespread weed in the cotton (Gossypium hirsutum) fields along the Yangtze River in Anhui. Cotton is highly sensitive to weed competition. This research aims to determine the density competition effect of goosegrass on cotton and to identify its critical period for control, thereby allowing farmers to make well-formed decisions to further improve the management of goosegrass in cotton fields.

Methods From 2010 to 2012, two experiments were conducted at an experimental site in Anqing, Anhui. In the density competition experiment, an additive series was used. The cotton density was kept constant while eight densities of goosegrass (0, 0.125, 0.25, 0.5, 1, 2, 3, and 4 plants·m^-1) were tested. This aimed to determine the effects of varying goosegrass densities on cotton growth and yield. In the critical control period experiment, different durations of weed interference and weed-free periods (0, 2, 4, 6, 8, 10, 12, 14 and 20 weeks after crop emergence) were investigated to determine how goosegrass affects cotton.

Important findings As the density of goosegrass increased, its plant height gradually decreased. Compared to 0.125 plants·m^-1 goosegrass, the plant height of goosegrass at densities of 3 plants·m^-1(2011) and 0.25 plants·m^-1 (2012) was significantly decreased. On average over three years, goosegrass biomass per unit area increased from 715 kg·hm^-2 (0.125 plants·m^-1) to 4 148 kg·hm^-2 (4 plants·m^-1). This indicates that intraspecific competition among goosegrass becomes more pronounced at higher densities. In 2012, the number of tillers and biomass per plant of goosegrass gradually increased with increasing weedy duration, and the height of goosegrass exceeded that of cotton during the first 12 weeks after crop emergence. With the increasing weed densities, the plant height and stem diameter of cotton decreased, while the number of fruit branches and bolls per plant were significantly reduced. The single boll mass was also reduced at higher densities of goosegrass, however, weed density did not significantly change the lint percentage. In 2012, the plant height of cotton significantly decreased at densities of over 2 plants·m^-1. The cotton stem diameter was remarkably reduced at densities of 3 plants·m^-1 or more in 2011 and 4 plants·m^-1 in 2012, respectively. Goosegrass even at the density of 1 plants·m^-1 reduced the fruit branch numbers, the boll number per plant and single boll mass of cotton by 8.7% to 11.6%, 18.6% to 35.2% and 0.1% to 4.6%, respectively. The seed cotton yields were significantly reduced at densities of 0.125 plants·m^-1 (2010 and 2012) and 0.25 plants·m^-1 (2011), with reductions ranging from 10% to 18%. The boll number per plant of cotton and seed cotton yield loss rate followed a hyperbolic model in response to goosgrass density. It is predicted that goosegrass at a density between 2.3 to 3.7 plants·m^-1 would result in a 50% reduction in the number of bolls per plant, while densities of 0.05 to 0.09 plants·m^-1 would lead to a 5% reduction in seed cotton yield. The increased competition duration of goosegrass resulted in a gradual decline in the height and stem diameter of cotton plants. The increased competition duration also significantly reduced the number of fruit branches and bolls per plant. A Logistic relationship exists between the seed cotton yields and the competition duration of goosegrass. Conversely, with an increasing weed-free duration, cotton plants exhibited greater height and stem diameter, along with a notable rise in the number of fruit branches, bolls per plant, and seed cotton yield. The increase in seed cotton yield with prolonged weed-free duration followed a Gompertz model. The critical period for controlling goosegrass at a density of 2.5 plants·m^-1 was between 35 to 83 days after cotton planting, based on a 5% yield-loss threshold.

Aims Plant sexual systems are important reproductive characteristics that affects plant mating, genetics, evolution, and species distribution. They are classified into three main categories based on the floral organ’s pistil and stamen arrangement: hermaphroditism, dioecy, and monoecy.

Methods We divided forest communities on the south slope of Daiyun Mountain (Fujian Province, China) into eight elevations along the elevational range of 900-1 600 m. Then we analyzed changes in the quantitative characteristics of woody plant sexual systems and investigated their correlation with environmental factors via Mantel correlation analysis.

Important findings The study area encompassed 85 woody plant species, with 47 (55.3%) hermaphroditic, 29 (34.1%) dioecious, and 9 (10.6%) monoecious species. With increasing elevation, the number of individuals and species diversity of dioecious plants show a “unimodal” pattern. The number of monoecious individuals first decreases and then increases, while the species diversity of monoecious plants significantly decreases. The number and species proportion of hermaphroditic plants show no significant changes. The Shannon-Wiener index and Pielou evenness index for sexual systems generally decreased with elevation, whereas the Simpson dominance index remained stable. Effective phosphorus and soil temperature were the primary drivers of elevational changes in sexual systems. In conclusion, the quantitative characteristics of the sexual systems of woody plants along elevational gradient on the south slope of Daiyun Mountain showed significant differences, and the elevational distribution of the sexual systems was highly sensitive to environmental changes, indicating that plants adapt to environmental changes by regulating the composition of their reproductive systems, thereby ensuring the continuous survival and reproduction of their populations.

Aims Our purpose is to explore the patterns and influencing factors of stem radial variation across different tree species and environmental conditions, which serves as the basis for quantifying and assessing forest carbon sinks and their carbon sequestration processes.

Methods This study focuses on Manchurian ash (Fraxinus mandshurica) and Dahurian larch (Larix gmelinii), employing continuous high-frequency monitoring of stem radial variations and relevant environmental factors. The research aims to analyze intra-annual and inter-annual differences in stem radial growth patterns, as well as the influence of environmental factors on stem radial dynamics.

Important findings Intra-annual stem radial variation in both Manchurian ash and Dahurian larch conformed to the Gompertz model, but exhibited incomplete synchrony at seasonal scales, and the annual cumulative radial increment and mean daily basal increment rate had significant differences between the two species. During the three-year observation period (2020-2022), Manchurian ash exhibited earlier initiation of radial growth compared to Dahurian larch. The day of year when 25% of annual cumulative radial increment was achieved (DOY₂₅) occurred 3-17 d earlier for Manchurian ash than for Dahurian larch; Manchurian ash demonstrated a 28-day longer peak growth period (L_PGS) than Dahurian larch in 2021. The two tree species showed comparable timing of growth cessation. Both tree species exhibited unimodal patterns in daily radial growth rates, characterized by an initial increase followed by a gradual decrease, reaching peak values in early summer (DOY 147-DOY 157). The critical phenological timings of radial growth (including DOY₂₅, DOY₅₀, and DOY₇₅) and the peak growth duration (L_PGS) were significantly influenced by interannual environmental factors. The daily stem radial variation of the two tree species during the growing season showed different trends depending on weather conditions, with a sinusoidal function type of fluctuation on sunny days. Daily amplitudes of Manchurian ash and Dahurian larch at the peak period of stem radial growth were significantly negatively correlated with volumetric soil water content and significantly positively correlated with photosynthetically active radiation. The amount of daily stem radial variation was negatively correlated with vapor pressure deficit for both species during the peak period of stem radial growth. This indicates that seasonal dynamics of stem radial variation are influenced by the characteristics of tree species, while the daily variation patterns are affected by environmental factors such as soil volumetric water content and light conditions. Moisture availability is a key factor influencing the stem radial variation of Manchurian ash and Dahurian larch.

Aims In recent years, the ever increasing greenhouse gas (GHG) emissions and extreme weather events had significantly impacted plant photosynthesis. Photosynthesis is closely related to plant growth and development, with photosynthetic rate is a key indicator of plant health, which has been widely used in predicting global carbon cycle dynamics. The net photosynthesis rate is also an important parameter in calibrating agriculture facility. Therefore, accurate prediction of plant photosynthesis rate is important to agriculture, forestry and grassland research.

Methods We used photosynthesis meter to obtain photosynthetic data of common reed (Phragmites australis) and smooth cordgrass (Spartina alterniflora) under different environmental conditions, we then fitted seven single-factor photosynthetic response models, and developed multifactorial photosynthetic rate prediction model using theory-guided neural network (TgNN).

Important findings All existing single-factor photosynthetic response models show good performances in fitting photosynthetic data but lack theoretical research value; whereas the multifactor photosynthetic model based on TgNN shows good predictability and generality. Our contribution provides a new avenue for calibrating more accurate and reliable models for predicting plant photosynthetic rate.

Aims As a crucial coupling agent linking plant roots, soil, and microorganisms, root exudates serve not only as an important vector for information transformation, but also as the core carrier for energy input, playing a significant role in shaping responses of plants to environmental changes. However, the effects of mixed-species on the metabolite compositions of root exudates remain unclear. Our objective is to explore the differences in metabolite compositions of root exudates between mixed stands and corresponding pure stands, and the implications on sustainable management of subtropical plantations.

Methods In this study, we used in-situ collection devices to sample root exudates of Pinus massoniana and Erythrophleum fordii in their pure and mixed (P. massoniana× E. fordii) stands in southern subtropial China. The metabolite compositions of root exudates of each species were analyzed using LC-MS/MS.

Important findings (1) The relative quantitative values of lipids, organic heterocyclic compounds, organic acids and organic oxygen compounds of root exudates of P. massoniana and E. fordii were significantly higher in pure stands than in mixed stands. (2) Comparative analysis of differential metabolites between pure and mixed forests, we revealed that P. massoniana had 208 differential metabolites, with glycerophospholipids exhibiting significant up-regulation in the P. massonianapure forest, and E. fordii had 106 differential metabolites, with p-Mentha-1,8-dien-7-ol, chavicol, isobutyric acid and diplodiatoxin exhibiting significant up-regulation in the E. fordiipure forest. (3) KEGG annotation and enrichment analysis showed that lipid metabolism pathways were significantly up-regulated in both P. massoniana and E. fordiipure forests compared to their mixed forest, and the lipid metabolism was correlated with plant defense strategies.

Aims The objective of this study is to elucidate the response mechanism of amino acids and their derivatives secreted by the roots of salt-tolerant plants under salt stress.

Methods This study selected Elytrigia elongata as the research subject. Four levels of salt stress (CK, mild, moderate, and severe) were established by adding varying concentrations of NaCl. Non-targeted metabolomics analysis based on liquid chromatography-mass spectrometry (LC-MS) was employed to investigate the changing trends of root-secreted amino acids and derivatives in response to increasing salt stress intensity, as well as their relationships with root characteristics and the rhizosphere soil properties.

Important findings The results indicated that with escalating salt stress, the secretion of L-Arginine, L-Dopachrome, 2,3,4,5-Tetrahydropyridine-2,6-dicarboxylic acid, N-Acetyl aspartic acid, L-Phenylalanine, L-Methionine, trans-3-Hydroxy-L-proline, and N-Acetyl-L-phenylalanine significantly decreased. In contrast, betaine and N-Jasmonic acid isoleucine exhibited significant increases. However, no significant differences were observed in the abundance of betaine across mild, moderate, and severe stress conditions. There was only no significant difference in the abundance of N-jasmonic acid isoleucine between the mild stress group and the control group. Although the abundances of pipecolic acid and homomethionine exhibited a significant response to salt stress, they did not display a linear trend with increasing salt stress intensity. The secretion amounts of the other amino acids and derivatives showed no significant changes. These findings suggest that Elytrigia elongata adapts to salt-stressed environments by modulating the secretion of specific amino acids and derivatives. Soil salinity, electrical conductivity, volumetric water content, total root volume, and total root surface are key factors influencing the up-regulation of betaine and N-jasmonic acid isoleucine. Soil electrical conductivity serves as a key influencing factor for the secretion of eight down-regulated amino acids and their derivatives. Path analysis indicates that both the up-regulated and down-regulated groups of ten amino acids and their derivatives are regulated by soil electrical conductivity and pH. Collectively, these results provide a scientific foundation for understanding the physiological mechanisms underlying how plants adapt to salt stress.

Aims Root water absorption and leaf transpiration work together to maintain the dynamic balance of water in plants. Long distance water transport in the xylem mainly relies on transpiration pull, whereas root pressure functions only at night or under conditions of low transpiration. Some rattan and herbaceous plants have high root pressure. However, given that transpiration pull simultaneously occurs, it remains unclear whether the root pressure changes affect transpiration rate, as well as the speed and manner in which transpiration responds to root pressure variations.

Methods In this paper, the effects of low temperature (0 °C), high temperature (35 °C), salt stress (200 mmol·L^-1 NaCl), drought (20% PEG 6000), fibrous root removal and in vitro conditions on root pressure and transpiration of Dracaena sanderiana were studied to explore the feedback of transpiration on root pressure.

Important findings (1) The root pressure of D. sanderiana was relatively high. Under non-stress conditions, it could maintain positive throughout the day and could independently drive water to the top of the stem. The maximum transpiration rate of D. sanderiana was only 0.37 mmol·m^-2·s^-1, which might explain why the root pressure can remain positive throughout the day. (2) After low temperature treatment, both root pressure and transpiration decreased, while increased under high temperature treatment, indicating that the root system was affected by temperature. This suggests that temperature directly impacts the root system, altering root pressure production, which in turn rapidly affects transpiration. (3) After salt, drought, fibrous root removal and in vitro treatments, root pressure dropped to a negative value in one day and then gradually recovered to near 0. The transpiration rate showed a slight initial decrease after several hours of short-term treatment, followed by a reduction to 18%-72% of the pre-treatment level the next day, and eventually dropped to zero after 4-12 d of long-term treatment, which indicated that the transpiration rate and stomatal conductance of D. sanderiana responded rapidly to the change of root pressure. In conclusion, after the root pressure disappeared, the transpiration pull failed to maintain the previous transpiration rate, suggesting that, unlike most plants, the long-distance water transport in the xylem of D. sanderiana is root pressure-driven. This study provides theoretical support and guidance for water management in D. sanderiana cultivation.

Aims In view of the expanding area of saline-alkaline land and the decline of maize (Zea mays) yield in Yinhuang Irrigation District of Ningxia, it is important to explore the effect of vertical deep rotary tillage with organic fertilizer on the aging characteristics of maize leaves and yield, which can provide theoretical basis for delaying the aging of maize and boosting yield in saline-alkaline land of this region.

Methods The study was carried out in Pingluo, Ningxia in 2021-2022. Two types of tillage methods including conventional tillage (TF, tilling depth 25-30 cm) and vertical deep rotary tillage (DT, depth 40-45 cm) were set as main zones, and four levels of organic fertilizers including 0 kg·hm^-2 (M0), 7 500 kg·hm^-2 (M1), 15 000 kg·hm^-2 (M2) and 22 500 kg·hm^-2 (M3) were set as sub-zones for analyzing the yield and leaf senescence characteristics of maize in saline-alkaline land.

Important findings (1) In the DT plus M2 treatment, the yield of maize was significantly increased, and the amount of organic fertilizer should be kept between 14 505-16 710 kg·hm^-2 to maximize the yield; under this treatment, the leaf area index (LAI) and relative chlorophyll content (SPAD) of maize were significantly increased, and the onset of leaf senescence was delayed by 1.7-2.19 d. (2) Compared with other treatments, DT with organic fertilizers decreased soil pH and electrical conductivity (EC), proline (Pro) and malondialdehyde (MDA) contents, and increased the contents of alkaline nitrogen (AN), available phosphorus (AP), available potassium (AK), and organic matter (OM). The activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and the contents of soluble sugar (SS) has significantly increased. The M2 treatment was the best among the four treatments. Compared with the M2 treatment, excessive organic fertilizer input (M3) increased soil pH, EC, and MDA content, and decreased nutrient content, SOD activity, POD activity, CAT activity, SS content, and Pro content, which inhibited the growth and yield of maize. (3) Pearson correlation analysis showed that maize yield was significantly or highly significantly positively correlated with leaf LAI, SPAD, SOD activity, POD activity, CAT activity, Pro content, SS content, soil AN content, AK content, and OM content, and significantly or highly significantly negatively correlated with MDA content and EC. (4) The principal component analysis showed that the composite scores of M2 > M3 > M1 > M0 under vertical deep rotary tillage with organic fertilizer treatment. In this study, vertical deep rotary tillage with 15 000 kg·hm^-2 organic fertilizer could effectively improve the saline soil environment, delay leaf senescence, increase leaf antioxidant enzyme activity, and reduce the accumulation of MDA, which in turn could stimulate the yield of maize.