Amid increasing drought frequency driven by climate change, lianas are expanding rapidly in subtropical forests and have become important competitors for tree water resources. However, how lianas affect host tree water use strategies and subsequent recovery capacity remains poorly understood. We selected evergreen (Myrsine seguinii, Daphniphyllum oldhamii) and deciduous (Alniphyllum fortunei) species under three treatments: liana-free control, liana-infested, and liana-removed. Stable isotopes (δ2H, δ18O, δ13C) were used to quantify water sources and water use efficiency (WUE). Under liana infestation, M. seguinii increased groundwater reliance from 19.05% to 44.12%, D. oldhamii increased deeper soil water uptake from 10.32% to 38.02%, and A. fortunei increased rainwater utilization from 3.95% to 31.47%. WUE of M. seguinii increased by 142.21% and 82.62% in growing and non-growing seasons, whereas D. oldhamii decreased by 67.01% and 54.79%. A. fortunei showed stable WUE. After liana removal, A. fortunei showed balanced water sources uptake and WUE comparable to the liana-free treatment, indicating substantial recovery of its water use strategy. In contrast, neither evergreen species achieved full recovery: both M. seguinii and D. oldhamii showed significant differences in WUE compared with the liana-free treatment, and D. oldhamii additionally lost access to deep water sources (rainwater accounting for 28.55% of uptake in the growing season and shallow soil water for 38.87% in the non-growing season). Plant responses to biotic stress and post-stress recovery are constrained by inherent physiological traits. These findings provide a new theoretical perspective for understanding the dynamics of interspecific interactions in forests and ecosystem responses to disturbance.

Lianas are woody vines that rely on host trees for support to access the forest canopy. Lianas typically occur in tropical and subtropical forests and coexist with trees in subtropical secondary forests, where their interactions strongly influence forests communities and ecosystem functioning. We compared stem and leaf traits of lianas and trees to examine the effects of growth form and leaf habit. We measured 20 functional traits (9 stem anatomical/hydraulic and 11 leaf morphological/nutrient) from 10 liana and 14 tree species coexisting in a subtropical forest of south China. Lianas exhibited 3.5‐fold higher sapwood specific conductivity ( K s ) than trees, as well as higher predawn leaf water potential (Ψ predawn ) and hydraulically weighted vessel diameter ( D h ). Additionally, maximum vessel diameter ( D max ) of lianas approximately three times higher than that of trees, and theoretical hydraulic conductivity ( K p ) was ~20 times higher than trees. Functional trait analysis indicated that lianas grouped separately from trees along a leaf and stem economics spectrum: lianas were grouped together at the fast end of the plant economics spectrum, with high hydraulic diameter ( D h ) and high nitrogen (N) and phosphorus (P) concentration, exhibiting an acquisition‐focused water and nutrient strategy, permitting rapid growth and tissue turnover. Trees were grouped at the low end of the plant economics spectrum, with a high C:N ratio, high vessel thickness/diameter (VT/VD) and high wood density (WD), exhibiting a conservative resource acquisition strategy. Moreover, lianas exhibited significantly higher modularity in their trait networks compared to trees (0.490 vs 0.345; p = 0.043), reflecting stronger local integration of function, with tightly coordinated traits that may enhance system adaptability by limiting the spread of local drought‐induced stress. These findings improve our understanding of the mechanisms shaping ecological strategies across woody plants with different growth forms and leaf habits, and addresses the limited trait‐based knowledge of subtropical forests relative to tropics. This study provides novel insight into how growth form and leaf habit shape resource acquisition and niche partitioning in co‐occurring woody species in a subtropical and secondary forests. Read the free Plain Language Summary for this article on the Journal blog.

Choerospondias axillaris is an important edible and wood plant in China. In 2023, leaf spot was observed on C. axillaris in Yongxiu County, Jiangxi Province, China, with a disease incidence of approximately 50%. To identify the etiologic agent of the disease, the fungal isolates were obtained using the tip hyphae picking method. Based on colony and conidial characteristics, 66.7% of the isolates were identified as Pestalotiopsis sp. Phylogeny analysis of combined sequences from the internal transcribed spacer (ITS), beta-tubulin (TUB2) and elongation factor 1-alpha (TEF) loci strongly supported a monophyletic clade, with posterior probability and bootstrap values of 1.00 and 97, respectively. Further morphological examination confirmed the establishment of a new species, which was described as Pestalotiopsis choerospondicola sp. nov. Koch's postulates were fulfilled by inoculating C. axillaris seedlings in the field, confirming the pathogenicity of the fungus. The sensitivity of the pathogenic strain Y1-2 to eight fungicides was assessed, revealing that 8% compound sodium nitrophenolate (CSN), carbendazim and tebuconazole exhibited high toxicity to Y1-2, with effective concentration inhibiting 50% (EC50) of mycelial growth measured at 0.3395, 0.5417 and 0.7680 mg/L, respectively. In summary, P. choerospondicola sp. nov. was identified as the causal agent of leaf spot on C. axillaris. CSN, carbendazim and tebuconazole are recommended for disease management.

This study investigated the effects of drought on carbon (C) allocation underground in two evergreen mycorrhizal tree species. Two-year-old Schima superba (AM) and Castanopsis sclerophylla (ECM) seedlings underwent a short-term drought with 13CO₂ labeling using the in-growth core method to quantify soil C input, with C content and δ13C analyzed by elemental analyzer–isotope ratio mass spectrometer. Short-term drought had no significant effects on biomass, 13C concentrations, or soil C allocation in S. superba, whereas for C. sclerophylla, short-term drought decreased the biomass and leaf 13C concentrations, but enhanced the mycorrhizal colonization by 55.8

Abstract Large‐scale application of methanol‐driven heterotrophic denitrification (MHD) biofilms to recirculating mariculture systems (RMSs) is constrained by the requirement of precise methanol dosage. The emergence of intelligent aquaculture offers an opportunity to address this challenge, necessitating a comprehensive understanding of the denitrification performance, kinetics, and microbial community of MHD biofilm reactors during the treatment of nitrate (NO3−‐N)‐rich RMS water. Therefore, this study conducted a systematic investigation on an MHD biofilm reactor for water purification in RMSs. Results show that the MHD biofilm reactor effectively eliminated NO3−‐N with removal efficiencies of 53.0%–98.4% and rates of 66.77–643.73 mg L−1 day−1. Complete denitrification was the dominant process of NO3−‐N removal in the MHD bioreactor; however, partial denitrification (PD) and dissimilatory nitrate reduction to ammonium (DNRA) were also observed. Higher carbon‐to‐nitrogen (C/N) ratio (0.5–2.5), hydraulic retention times (HRT) (0.5–4.0 h), and temperatures (10–30°C) and lower influent NO3−‐N concentrations (25–100 mg L−1) facilitated complete denitrification, whereas higher influent dissolved oxygen (DO) (4.0–6.5 mg L−1) slightly enhanced PD. These parameters had little impact on DNRA. The NO3−‐N and nitrite distributions along packing height followed a first‐order model and a first‐order consecutive reaction model, respectively, with their rate constants depending on the operational parameters. Enrichment cultivation, reactor start‐up, and reactor operation promoted the proliferation of Methylophaga, rendering it the dominant bacterial genus in the biofilm and the primary functional group for MHD. Lesser genera (e.g., Methanolobus, Methylomicrobium, Sulfurimonas, and Marinicella) also contributed to niche differentiation and elemental cycling in the MHD bioreactor.

Riverine inputs and sedimentary processes jointly regulate nutrient cycling in semi-enclosed coastal seas, yet their combined influence on phosphorus (P) dynamics remains insufficiently understood. This study evaluates the chemical forms, spatial gradients, burial, and long-term evolution of sedimentary P from the Yellow River Estuary Wetland to the Bohai Sea based on observations from 2011 to 2020. A pronounced regional pattern was identified, with detrital P dominating and a clear land-sea gradient reflecting the influence of major riverine inputs. Spatial heterogeneity was further expressed through contrasting sedimentary environments: high-sedimentation areas accumulated substantial detrital P, whereas regions with stronger biological activity exhibited elevated reactive P. At the sediment-water interface, burial exceeded benthic release, enhancing deposition of reactive P and contributing to a 22.7% increase in total sedimentary P from 1998 to 1999 to 2018-2020, indicative of efficient downward transport. Despite this, porewater data showed that benthic efflux remained sufficient to influence nutrient stoichiometry in the overlying water. Elevated nitrogen-to-phosphorus ratios, amplified by terrestrial loading and imbalanced benthic fluxes, reinforce persistent P limitation and highlight the vulnerability of the Bohai Sea to nutrient imbalance. These results highlight the central role of river-sea coupling in regulating coastal P pool and guiding eutrophication management.

Coastal pollution associated with mariculture nitrogen discharge necessitates efficient denitrification processes. However, the mariculture wastewater treatment is challenged by its high sulfate content, which poses a risk of toxic sulfide production during conventional heterotrophic denitrification. This study conducted a systematic investigation into a poly-3-hydroxybutyrate-cohydroxyvalerate (PHBV)-driven heterotrophic denitrification (PHD) biofilm process treating mariculture wastewater over 195 days. The PHD bioreactor achieved high nitrate removal efficiencies (53.5%-99.4%) and rates (110.0-630.5 mg L- 1 d(-1)), with minor accumulation of nitrite (< 5.5%) and ammonia (< 3.7%). However, phosphorus removal was limited (4.0%-20.0%). Bioreactor performance was significantly influenced by hydraulic retention time, influent nitrate concentration, and temperature, but was resilient to variations in influent dissolved oxygen levels. Kinetic analysis indicates a shift in the optimal kinetic model for nitrate removal from halforder to zero-order as the influent nitrate concentration increased, reflecting an alteration in the rate-limiting step. Metagenomic sequencing revealed a diverse microbial community dominated by Proteobacteria (68.78%), with key genera including Sedimenticola (10.02%), Marinobacter (6.79%), Shimia (3.70%), Azoarcus (2.13%), and Thauera (2.10%). Functional gene analysis confirmed the metabolic pathways for PHBV degradation and denitrification as the primary nitrate removal route. Crucially, despite the high sulfate load, no significant sulfide accumulation was observed in the effluent, which could be attributed to the co-existence of sulfur-oxidizing and reducing bacteria in the biofilm. This study demonstrates that the PHD biofilm process is a robust strategy for effective nitrate removal in sulfate-rich mariculture wastewater without causing sulfide-related secondary pollution.

[Objective]Forest regeneration is a core process of forest succession and serves as a key indicator for species development and community structural stability.This study aims to investigate the regeneration dynamics of major tree species and their relationship with competition in a subtropical secondary evergreen broad-leaved forest.[Method]Based on census data from 2015 and 2020 in a 12-ha permanent forest dynamics plot in Guanshan,Jiangxi Province,13 dominant tree species(8 evergreen broad-leaved,3 deciduous broad-leaved,and 2 coniferous)were selected according to their importance,dominance,and diameter class structure.Their population dynamics over the five-year interval were analyzed,including mortality rate,recruitment rate,changes in diameter class structure,and differences in competition intensity between dead and surviving individuals.[Result](1)The diameter class structures of the evergreen broad-leaved species remained stable,exhibiting a negative exponential distribution.In contrast,the coniferous species Pinus massoniana showed a positive exponential(declining)pattern.The diameter class structures of the deciduous broad-leaved species Choerospondias axillaris and Liquidambar formosana shifted from a negative exponential to an approximately uniform distribution,also indicating a declining trend.(2)Except for Castanopsis carlesii and Phoebe bournei,mortality rates exceeded recruitment rates for all other species.Both the number of dead and recruited individuals decreased with increasing diameter class.(3)Competition intensity decreased with increasing diameter at breast height for all tree species.In the small diameter class(1-5 cm),the competition intensity of dead individuals was significantly higher than that of surviving individuals for five species,including Castanopsis eyrei and Daphniphyllum oldhamii.(4)For ten species,including Castanopsis eyrei,mortality rates increased significantly with increasing plant density.In contrast,mortality rates of Machilus thunbergii,Choerospondias axillaris,and Elaeocarpus duclouxii decreased with increasing density.[Conclusion]The evergreen broad-leaved forest in Guanshan is succeeding towards a climax community dominated by shade-tolerant evergreen species.Competition intensity is an important biotic driver of population dynamics,but its effect direction is distinctly species-specific,reflecting the diversity of ecological strategies among different tree species.These findings provide an important scientific basis for predicting the dynamics and guiding close-to-nature management of subtropical forests.

[Objective]This study aims to provide a theoretical basis for exploring the endangered mechanism and ex situ conservation of Sinomanglietia glauca by systematically comparing the growth and diurnal photosynthetic responses of Sinomanglietia glauca and Schima superba under different light and fertilization treatments.[Method]Seedlings of S.glauca and S.superba were used as experimental materials.Three shading regimes(S0,S1,S2)were established under two fertilization treatments:nitrogen and phosphorus application(N1P1)and no nitrogen and phosphorus application(N0P0),yielding six simulated cultivation treatments.Growth performance and diurnal changes in photosynthetic parameters were then compared between the two species under these treatments.[Result](1)Ground diameter and plant height growth of S.glauca were significantly affected by shading(P<0.001),whereas the effect of fertilization was not significant(P>0.05).In contrast,the growth of S.superba was less affected by shading and fertilization and was even promoted under mild shading.(2)Across all treatments,the diurnal course of net photosynthetic rate(Pn)in both species exhibited a single-peaked pattern,and no midday depression of photosynthesis was observed.Fertilization had no significant effect on Pn in S.glauca(P>0.05).Stomatal conductance(Cond)showed a single-peaked pattern in S.glauca but tended to be bimodal in S.superba.Intercellular CO2 concentration(Ci)generally showed a U-shaped pattern.Transpiration rate(Tr)and water use efficiency(WUE)both showed single-peak patterns in the two species.Light use efficiency(LUE)fluctuated with small amplitude in both species.(3)Under low-light conditions,Pn in S.glauca was constrained by multiple environmental factors,and its adaptability to environmental conditions was significantly lower than that of S.superba,which may help explain its narrow ecological niche.[Conclusion]The growth of S.glauca seedlings is primarily limited by shading,whereas fertilization has little effect.In contrast,S.superba seedlings are less responsive to both shading and fertilization.Compared with S.superba,S.glauca seedlings demand more stringent environmental conditions under various shading levels and exhibit weaker photosynthetic acclimation.Therefore,for ex situ conservation of S.glauca,priority should be given to well-lit sites such as forest gaps,forest edges,and thinned stands,so as to facilitate population conservation and recovery.

Clarifying the role of density regulation in different stand types of Chinese fir (Cunninghamia lanceolata) is beneficial for sustainable management. Stand density management diagrams (SDMDs) can help in simulating thinning, regulating stand structure, and balancing timber yield. This study, conducted in Ganzhou City, a mid-subtropical region of China, used second-class forest resource survey plots dominated by Chinese fir, including 541 Chinese fir pure stands, 232 Chinese fir-conifer mixed stands, and 351 Chinese fir-broadleaf mixed stands. Equations for self-thinning, dominant height, and stand volume were constructed, and the SDMDs were subsequently developed to simulate two management scenarios: self-thinning and thinning. The results indicate that self-thinning relationships differ among Chinese fir stand types and that appropriate thinning can improve stand growth. Mixed stands, particularly Chinese fir–broadleaf mixed stands, showed greater growth potential at later stages, highlighting the role of species mixing in reducing competition and enhancing resource-use efficiency. The SDMDs developed in this study provide a practical tool for density regulation and silvicultural planning in Chinese fir plantations. However, being based on regional-scale growth models, the results mainly reflect regional conditions and should be further validated with long-term experiments.

Phosphorus (P) is an essential nutrient for primary production and frequently acts as a limiting factor in estuaries. The Changjiang River Estuary, recognized as one of the largest estuaries globally, has experienced significant changes in nutrient dynamics due to anthropogenic activities. The recent reduction in P loading from the Changjiang River may have significant implications for the dynamics of dissolved inorganic phosphorus (DIP) within this estuarine system. Based on DIP data collected in 2017, 2019, and 2023, combined with historical datasets, we aim to identify the drivers of DIP concentration changes in the Changjiang Estuary under the change in river inputs. The results indicate significant spatiotemporal variations in the distribution of DIP in the Changjiang Estuary, with the highest average concentration in winter. DIP exhibits non-conservative behavior along the salinity gradient, primarily influenced by biological utilization. Long-term DIP variations can be divided into three stages: a low-concentration period (1984-1987), a significant increase (1987-2014), and a decline (since 2015), with a current decreasing trend of 0.024 µmol/(L·yr) (R² = 0.97, P < 0.05). A discernible trend of P depletion in estuarine environments is observed, attributed to diminished riverine load and enhanced phytoplankton fixation. The reduction, and in some cases depletion, of DIP in the Changjiang Estuary has significantly altered the nitrogen-to-phosphorus ratio. The recent changes in total phosphorus (TP) compositions in the Changjiang Estuary are also attributed to a decrease in riverine input. Ongoing terrestrial nutrient management may further lower DIP concentrations, potentially impacting the estuarine ecosystem.

The expansion of bamboo (Phyllostachys edulis) affects the growth status of trees in colonized forests, but there has been insufficient research on changes in tree water physiology. In this study, we used stable δ2H, δ18O, and 13C isotope ratios to analyze the water sources and water use efficiency (WUE) of bamboo, deciduous broadleaf trees (Alniphyllum fortunei), and evergreen broadleaf trees (Machilus pauhoi and Castanopsis eyrei) in a bamboo-expended broadleaf forest (BEBF), a bamboo-absent broadleaf forest (BABF), and a bamboo forest (BF). We found that the expansion of bamboo had no significant effect on the water sources and WUE of deciduous broadleaf trees, but altered the water sources of evergreen broadleaf trees. During the growing season, evergreen broadleaf trees decrease their uptake fractions of surface soil water by 7.1% to 9.6% and increased their uptake fractions of middle soil water by 5.8%~9.4%. Conversely, during the non-growing season, they increased their uptake fractions of surface soil water by 11.9% and decreased their uptake fractions of deeper soil water by 5.6%~12.9%. Additionally, after expanding into broadleaf forests, bamboo increased its uptake proportion of surface and shallow soil water by 20.0% and 9.4% during the growing season. Its WUE also improved, increasing by 20.0 μmol/mol and 13.0 μmol/mol during the growing and non-growing seasons, respectively. These results indicate that as bamboo expands into broadleaf forests, it enhances its competitiveness for water resources by changing its water use strategy. Compared to deciduous broadleaf trees, evergreen broadleaf trees exhibit more flexible water use strategies under the conditions of bamboo expansion. Our research reveals, for the first time, how broadleaf trees adjust their water use strategies in response to bamboo expansion, and uncovers the mechanisms behind bamboo expansion into evergreen broadleaf forests from the perspective of water use strategies. This will aid future forest management under the conditions of bamboo expansion.

(1) Background: Moso bamboo (Phyllostachys edulis (Carrière) J. Houz.) expansion has seriously altered the species composition and structure of adjacent forest ecosystems in subtropical regions. However, the shift in phosphorus (P) biogeochemical cycling has yet to be assessed, which is a critical gap considering the great variation in ecophysiological properties between invasive bamboo and the displaced native tree species. (2) Methods: We investigated and compared expansion-induced changes in P pools (plant, litter, and soil) and P fluxes (plant uptake and litterfall return) using paired sampling of the bamboo-dominated forest (BDF) and secondary evergreen broadleaved forest (EBF) at Jiangxi province’s Dagang Mountain National Forest Ecological Station. (3) Results: Both the P storage of the plants and litter were significantly greater by 31.8% and 68.2% in the BDF than in the EBF, respectively. The soil total P and available P storage were 28.9% and 40.4% lower, respectively, in the BDF than in the EBF. Plant P uptake was 15.6% higher in the BDF than in the EBF, and the annual litter P return was 26.1% lower in the BDF than in the EBF due to higher P resorption efficiency for moso bamboo compared with evergreen broadleaved tree species. The ecosystem P cycling rate was reduced by 36.1% in the BDF compared with the EBF. (4) Conclusions: Moso bamboo expansion slowed the broadleaved forest ecosystem’s P cycle rate, likely because moso bamboo has higher P-use efficiency, reserving more P in its tissues rather than returning it to the soil. The results from this study elucidate an understudied element cycle in the context of forest succession, demonstrating the ecosystem consequences related to bamboo invasion.

Neighborhood competition influences tree growth, which can affect species composition and community succession. However, there is a lack of understanding regarding how dominant tree species at different successional stages of forest communities respond in terms of crown architecture and functional traits during their growth process to neighborhood competition. In this study, we analyzed the responses of average annual basal area increment (BAI), crown architecture, and leaf functional traits of early-successional species (Cunninghamia lanceolata and Pinus massoniana), transitional species (Alniphyllum fortunei and Choerospondias axillaris), and late-successional species (Elaeocarpus duclouxii and Castanopsis carlesii) to neighbor competition in a secondary evergreen broad-leaved forest. We found that the BAI of all species is negatively correlated with competition intensity. Notably, early-successional and transitional species exhibited a more rapid decline in growth rates compared to late-successional species in response to increased competition. Among these tree species, the response of crown structure to neighbor competition exhibited variation. Early-successional and transitional species displayed a negative correlation between the competition index and crown area (CA)/diameter, while a positive correlation emerged between the lowest branch height (LBH)/height. Conversely, late-successional species followed the opposite trend. In terms of leaf functional traits, specific leaf area (SLA) showed heightened sensitivity to neighborhood competition, with a positive correlation between SLA of all tree species and the competition index. Furthermore, water use efficiency (WUE) demonstrated negative correlations with the competition index in early-successional and transitional trees, while a positive correlation emerged with late-successional trees. These findings suggest that early-successional and transitional trees prioritize vertical canopy growth, whereas late-successional trees tend to favor horizontal canopy expansion in response to neighboring competition. Additionally, early-successional and transitional trees experience more significant suppression of radial growth rate. Our research contributes to a deeper understanding of the underlying mechanisms driving changes in species composition and community succession.

Phosphorus (P) is an essential nutrient for algal growth in nearshore ecosystems. In recent years, there has been a shift in nutrient dynamics in nearshore areas, leading to an exacerbation of P limitation, although the underlying mechanisms remain unclear. This study analyzed the P species and budget in the Bohai Sea (BS) from 2011 to 2020, aiming to explore the intrinsic mechanisms of P limitation in the BS. The results show that the main external source of P in the BS was river transport (89%), and the primary fate of P was burial (96%) into the sediment. Due to excessive nitrogen (N) input and biological processes in the BS, the P budget in the BS is unbalanced, resulting in an increase in the N/P ratio, particularly in nearshore areas. Nearshore areas typically have lower concentrations of dissolved inorganic P (DIP) in the water and higher concentrations of reactive P (Reac-P) in the sediments. This pattern is particularly evident in Bohai Bay and the northwest nearshore region, where harmful algal blooms occur frequently. To cope with enhanced P limitation, the biologically driven P regeneration and cycling processes within the BS are accelerated. From 2011 to 2020, the concentration of DIP in the BS during autumn increased, while the content of Reac-P in sediments slightly decreased. Historical data indicate that P depletion in the BS is intensifying and expanding, primarily due to N enrichment and algal production. N enrichment alters the structure and composition of primary production, potentially exacerbating P depletion in the BS. Excessive N may have significant impacts on the P pool, potentially influencing the stability of future coastal ecosystems.

This study presents a systematic investigation on pyrite-driven autotrophic denitrification (PAD) and pyrite/ poly-3-hydroxybutyrate-co-hyroxyvelate (PHBV)-driven mixotrophic denitrification (PPMD) for removing nitrate (NO3 --N) and phosphate (PO43- -P) from mariculture wastewater. PAD and PPMD biofilm reactors were operated for 195 days to assess their operation performance and NO3 --N removal kinetics as well as the contributions of PAD and PHBV-driven heterotrophic denitrification (PHBV-HD) to the NO3 --N and PO4 3--P removal in the PPMD reactor. Compared to the PAD reactor, the PPMD reactor had higher NO3 - -N removal efficiency (34.1 %-88.8 %) and rate (82.0-541.6 mg L- 1 d- 1) but lower PO4 3- -P removal efficiency (17.1 %-94.5 %) and rate (9.0-60.7 mg L- 1 d- 1), and yielded less sulfate but more acidity and residual DOC. HRT (0.5-4.0 h), influent NO3 --N concentration (25-150 mg L- 1) and temperature (10-30 degrees C) significantly affected the NO3 --N and PO4 3--P removal performance of both PAD and PPMD reactors, while influent DO concentration (0.1-7.5 mg L- 1) did not. A zeroorder kinetic model well described the NO3 --N removal in the PAD reactor, but the optimal kinetic model for the PPMD reactor shifted from half-order to zero-order with increasing influent NO3 --N concentration. PHBV-HD contributed 65.6 % f 0.4 %-72.2 % f 1.2 % to the NO3 - -N removal in the PPMD reactor under different operational conditions, followed by PAD (27.8 % f 1.2 %-34.4 % f 0.4 %). PAD played a dominant role in the PO4 3--P removal in the PPMD reactor, whose contribution (69.5 % f 4.7 %-98.3 % f 2.3 %) was impacted by HRT, influent NO3 --N concentration, and temperature. This study highlights the PPMD potential for controlling the NO3 --N and PO4 3--P pollution associated with mariculture wastewater.

The chemical oxygen demand (COD) is an essential indicator of organic pollution that represents the amount of bulk carbon in water. COD is strongly correlated with nutrient cycles and other pollutants in the environment, but it has a limited ability to quantify the amount of organic carbon (OC), of which a large proportion is made up of refractory dissolved organic carbon (RDOC) and is a potential carbon sink. Moreover, the biodegradability of OC in terms of its fate and destination should be explored, as well as how this is reflected by COD. Methods based on particle size, spectroscopy, and isotopic tracing are expected to help with deciphering the bioavailability of COD-responsive OC and explore the processes of biogeochemical cycles. As the pressure on the environment from anthropogenic inputs increases, understanding the bioavailability of OC associated with COD will help with developing more precise scientific indicators for environmental monitoring and identifying how new tools will increase knowledge of the carbon cycle. In this review, we discuss the application, scope, means, and advances of COD measurement. Based on data in the literature, we estimate the global RDOC stock and assess the impact of anthropogenic RDOC on the carbon cycle in offshore bays. This review presents new insights into the behavior of OC in aquatic environments and a potential pathway for ocean negative carbon emissions by expanding the role of RDOC as a carbon sink to offset the effect of anthropogenic carbon emissions.

Although litter decomposition is closely linked to soil biochemical processes, the non-additive effects of litter mixing on soil C:N:P stoichiometry and the factors that regulate it have been rarely studied. In this study, an in situ foliar litter decomposition experiment examined the effects of mixtures of the foliar litter of Eucalyptus urophylla × grandis with five native tree species (Acacia crassicarpa, Castanopsis hystrix, Michelia macclurei, Magnolia sumatrana and Mytilaria laosensis) in subtropical China. We investigated the decomposition and element release dynamics of single and mixed foliar litters, their non-additive effects on soil C:N:P stoichiometry, and the potential factors regulating this non-additive effect. Our results show that foliar litter mixing promoted mass loss and element release, with less mass remaining for one mixture. The magnitude of the non-additive effects of decomposing mixed foliar litter on mass remaining, element release, and soil C:N:P stoichiometry varied by litter type. Specifically, antagonistic effects were common for mass remaining (accounting for 10.0

[Objective]This study measured the nutrients stoichiometric characteristics between plants and soil at different succession stages,and analyzed the correlation between plant-soil nutrients stoichiometric,thus providing a theoretical basis for revealing the survival strategies of plants in community succession.[Method]The spatio-temporal substitution method was used to determine the C,N and P contents of stem and soil of Pinus massoniana community,Populus pseudoacacia community,and Castanopsis hystrix community at different development stages(early,peak and late stage)in the Guanshan Nature Reserve of Jiangxi Province.[Result](1)The soil C,N and P contents of three forest increased from early to late stage,among which the soil C,N and P contents for P.massoniana forest increased by 5.5 times,6.1 times and 0.04 times,those of P.pseudoacacia forest increased by 0.45 times,0.38 times and 0.21 times,and those of C.hystrix the forest increased by 0.26 times,0.55 times and 0.34 times,respectively.(2)From the early to late stage of community,the stem C,C∶N and C∶P of P.massoniana were increased by 7.1%,164%and 200%,respectively,while its stem N and P contents were decreased by 58.9%and 70.0%,respectively.The stem C,N and P contents as well as their stoichiometric ratio of P.pseudoacacia fluctuated slightly.The stem C and N contents of C.hystrix changed little,and its stem P content was decreased by 25%.(3)The N,P and N∶P content of stem were significantly different among different species at the same development stage.The total N,P and N∶P of C.hystri were the highest in the early and peak stages,followed by P.Pseudopoplar and P.massoniana.At the same time,the soil C,N and P of C.hystri forest was significantly higher than those of P.Pseudopoplar forest and P.massoniana forest.(4)There was a significantly positive correlation between the stem C content of P.massoniana and soil C,N,C∶P,and N∶P,and a significantly negative correlation between the stem N,P and soil C,N,C∶P,and N∶P;while the correlation between the stem and soil C,N,and P stoichiometric characteristics for P.pseudoalder and C.hystrix forest was weak.[Conclusion]The requirements of N and P of tolerant P.massoniana species were lower than those of the competing species C.hystri.P.massoniana can adapt to the poor soil in the early succession stage,and significantly increase the nutrient content of soil C,N and P to create good soil conditions for late successional tree species with high N and P requirements.

Better documentation and understanding of long-term temporal dynamics of nutrients in watersheds are necessary to support effective water quality management. We examined the hypothesis that the recent management of fertilizer use and pollution control in the Changjiang River Basin could govern the fluxes of nutrients from the river to the sea. Results based on historical data since 1962 and surveys in recent years show that concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) in the mid- and downstream reaches were higher than those in the upper reaches due to intensive anthropogenic activities, while dissolved silicate (DSi) was distributed evenly from the up- to downstream reaches. Fluxes of DIN and DIP increased rapidly, and DSi declined during the 1962-1980 and 1980-2000. After the 2000s, concentrations and fluxes of DIN and DSi remained almost unchanged; those of DIP remained stable until the 2010s and slightly decreased afterward. The decline in fertilizer use explains 45 % of the variance in the decline of DIP flux, followed by pollution control, groundwater and water discharge. As a result, the molar ratio of DIN:DIP, DSi:DIP and ammonia:nitrate varied largely during 1962-2020, and the excess DIN relative to DIP and DSi lead to increased limitations of silicon and phosphorus. A turning point probably occurred for nutrient fluxes in the Changjiang River in the 2010s, with the pattern of DIN from continuous increase to stability and DIP from increase to decrease. This decline in phosphorus in the Changjiang River has many similarities with the rivers worldwide. The continued basin nutrient management is likely to have a major influence on river nutrient delivery and therefore may control coastal nutrient budget and ecosystem stability.