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The decomposition of standing litter is a vital but easily neglected process. Most studies always focused on the decomposition of leaf litter on the surface of soil or sediment, whereas the decomposition of leaf and non-leaf litter in the air is often overlooked. A field experiment was conducted in the Yellow River Delta to investigate the decomposition of leaf and non-leaf (culm and sheath) litter (Phragmites australis) in the air and on the ground. The results showed that the litter on the ground decomposed faster than the standing litter due to its larger enzyme activities, and the remaining mass of litter on the soil surface was 73–87% of the standing litter. The culm litter had the largest mass remaining among three types of litter owing to the lowest enzyme activities and the largest initial C/N and C/P of the culm litter. Concerning the dynamics of nutrient, nitrogen and phosphorus in leaf and non-leaf litter were first released and then enriched at two decomposition interfaces. Of the three types of litter, the culm litter had the highest N remaining after 360 days of decomposition due to the largest initial C/N of the culm litter. Our findings emphasize the importance of standing litter decomposition in the wetlands of the Yellow River Delta, and suggest that the decomposition of non-leaf (culm and sheath) litter of emergent macrophytes should not be ignored in wetlands. [ABSTRACT FROM AUTHOR]

Despite growing interest in soil microbial resource limitation (MRL), the impacts of clipping-and-burning on bacterial resource acquisition and its soil carbon, nitrogen, and phosphorous stoichiometry (C:N:P) remain unclear, yet are critical for nutrient cycling and SOC accumulation in vegetation restoration. We examined the soil C:N:P and eco-enzymatic stoichiometry, bacterial life-history strategies, and bacterial resource limitation under the influence of clipping-and-burning management practices: high-intensity fire (HIF), low-intensity fire (LIF), clipping-and-fire (CF), clipping (CP), and an undisturbed control (CK) in a Karst site in southwest China. The results showed that SOC, TN, and TP in HIF and LIF were significantly (p < 0.05) reduced (by 64%, 97%, and 99%) compared to CK. However, soil C:N, C:P, and N:P ratios were surprisingly higher (18.1, 56, and 3.08) in CF than in CK. The ratios of soil microbial biomass carbon (MBC) and nitrogen (MBN) were higher (4.8) under clipping. In contrast, their ratios with microbial biomass phosphorus (MBP) were observed to be higher (22.3 and 6.4) under high-intensity fire compared to CK. Moreover, results show that there is a higher percentage of species linked with oligotroph bacteria of Rickettsiales in CF treatments than CK. Soil bacterial communities in CF treatments exhibited co-limitation by C and P, whereas N limitation was more pronounced under low-intensity fire conditions. In conclusion, the evidence links MRL to soil C:N:P stoichiometry, underscoring the critical role of oligotrophic bacteria in mediating soil nutrient dynamics under clipping-and-burning disturbances. These findings improve our understanding of MRL over the Karst region under clipping-and-burning treatments, shedding light on its relationship with soil C:N:P, eco-enzymatic stoichiometry, and bacterial life-history strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Plant litter decomposition is a crucial ecosystem process that regulates nutrient cycling, soil fertility, and plant productivity and is strongly influenced by increased nitrogen (N) deposition. However, the effects of exogenous N input on litter decomposition are still poorly understood, especially in temperate shrublands, which hinders predictions of soil C and nutrient dynamics under the context of global change. Temperate shrub ecosystems are usually N-limited and particularly sensitive to changes in exogenous N input. To investigate the responses of Vitex negundo and Spiraea trilobata litter decomposition to N addition, we conducted a field experiment in Vitex - and Spiraea -dominated shrublands located on Mt. Dongling in Beijing, North China. Four N treatment levels were applied: control (N0; no N addition), low N (N1; 20 kg⋅N⋅ha–1⋅year–1), moderate N (N2; 50 kg⋅N⋅ha–1⋅year–1), and high N (N3; 100 kg⋅N⋅ha–1⋅year–1). The litter decomposition in V. negundo was faster than that in S. trilobata , which may be due to the differences in their nutrient content and C/N ratio. N addition increased the amount of remaining N in the two litter types but had no effect on the remaining mass, C, or P. Nitrogen treatment did not affect the litter decomposition rates (k) of either litter type; i.e., N addition had no effect on litter decomposition in temperate shrublands. The neutral effect of N addition on litter decomposition may be primarily explained by the low temperatures and P limitation at the site as well as the opposing effects of the exogenous inorganic N, whereby exogenous N inhibits lignin degradation but promotes the decomposition of readily decomposed litter components. These results suggest that short-term N deposition may have a significant impact on N cycling but not C or P cycling in such shrub ecosystems. [ABSTRACT FROM AUTHOR]

Plant invasion can affect nutrient cycling by changing the quantity and quality of litter entering the environment. To determine the effect of an alien species (Spartina alterniflora) invasion on the decomposition rates and nutrient dynamics of litter in the Min River estuary, three communities with differing levels of invasion, namely, a Cyperus malaccensis community (before invasion, BI stage), a S. alterniflora community (after invasion, AI stage), and a C. malaccensis–S. alterniflora community (during invasion, DI stage), were studied using the space-for-time substitution method. Results showed that the decomposition of C. malaccensis was 59.79% faster than that of S. alterniflora, which was mainly related to the great variations in the C/N and lignin. Compared with S. alterniflora, the N (nitrogen) and S (sulfur) concentrations of litter in C. malaccensis were significantly higher. The C, N, and S stocks increased as the C. malaccensis was being invaded or after complete invasion by S. alterniflora, which might be ascribed to the higher mass remaining in S. alterniflora. Compared with S. alterniflora in DI stage, the higher C/N and C/S ratios might explain the higher C, N, and S stocks in S. alterniflora in AI stage. In summary, the invasion of S. alterniflora reduces the decomposition rate and nutrient release of litter. [ABSTRACT FROM AUTHOR]

Evaluating how decomposition rates and litter nutrient release of different litter types respond to changes in water conditions is crucial for understanding global carbon and nutrient cycling. However, it is unclear how decreasing water affects litter mixture interactions for the maize–poplar system in arid regions. Here, the responses of the litter decomposition process and litter mixture interactions in the agroforestry system to changes in water conditions (control, light drought, and moderate drought) were tested. Moderate drought significantly decreased the decomposition rate for poplar leaf and mixed litters, and decomposition rate was significantly reduced for maize straw litter in light and moderate drought stress. The mass loss rates of maize straw and mixed litters were significantly higher than that of the poplar leaf litter under drought conditions, but there was no significant difference among the three litter types in the control. There was no interaction between mass loss of the mixed litter in the control and light drought conditions, and the litter mixture interaction showed nonadditive synergistic interactions under moderate drought. In terms of nutrient release, there was also no interaction between litter mixture with nitrogen and carbon, but there was antagonistic interaction with potassium release under the light drought condition. Our results demonstrate that drought conditions can lead to decreasing decomposition rate and strong changes in the litter mixture interactions from additive effects to nonadditive synergistic effects in moderate drought. Moreover, light drought changed the mixture interaction from an additive effect to an antagonistic interaction for potassium release. [ABSTRACT FROM AUTHOR]

Large deep lakes in plateau regions provide crucial ecosystem services but are susceptible to eutrophication due to their long water residence time. To date, the water quality of deep lakes has not received as much attention as that of shallow lakes owing to logistical challenges. This study investigated the seasonal variation and vertical distribution of phosphorus and related environmental variables in a large deep lake in the Yunnan Plateau, China (Fuxian Lake). Generally, the concentrations of total phosphorus (TP, R2 = 0.862), total dissolved phosphorus (TDP, R2 = 0.922), and dissolved inorganic phosphorus (DIP, R2 = 0.889) exhibited a linear increase with the greater water depth, whereas the pH and dissolved oxygen (DO) showed decreasing trends. The TP, TDP, and DIP values were 0.012, 0.006, and 0.004 mg/L, respectively, in surface waters (0.5 m depth), and increased to 0.074, 0.065, and 0.062 mg/L, respectively, at 140.0 m depth. The averaged over ordering method demonstrated that DO and air temperature accounted for a higher proportion of the explained variance of TP, TDP, and DIP in the shallow water layer (0.5–20.0 m). In contrast, DO and pH accounted for a higher proportion of the explained variance of TP, TDP, and DIP in deeper water layers (40.0–150.0 m). As a warm monomictic lake, the higher observed phosphorus concentrations in deeper water and sediment potentially pose a risk of future eutrophication in the Fuxian Lake. Our findings demonstrate that more efficient technical and management measures should be taken to reduce the external phosphorus load to Fuxian Lake, so that the load to and from the sediment will decrease eventually. [Display omitted] • Vertical distribution of P and related variables was examined in a large deep lake. • Water P concentration exhibited a linear increase with the greater water depth. • Phosphorus was affected primarily by DO and air temperature in the shallow water. • Phosphorus was predominantly affected by DO and pH in the deeper water. • Higher concentrations of phosphorus in deeper water pose a risk of eutrophication. [ABSTRACT FROM AUTHOR]

A five-year (January 2009–December 2013) monthly monitoring program was undertaken in Shahe Reservoir to study phytoplankton dynamics and their relation to several key controlling factors including nutrient content and temperature. The results revealed that the phytoplankton biomass showed a significant single peak (mean of 30 mg/L) during May–July. The predominant genera showed significant seasonal succession, with the peak value of diatom biomass appearing in late spring and the peak value of cyanobacterial biomass appearing at early summer. Upon reduction of nitrogen and phosphorus, the biomass of phytoplankton in the reservoir decreased drastically. Based on correlation analysis and ordination analysis, biomass of the dominant genera showed significant positive relationships to temperature. The biomass of three dominant genera of Bacillariophyta,Cyclotella,Synedra, andAchnanthes, were significantly and positively related to ammonium concentration, while the biomass of three dominant genera from Cyanophyta,Aphanizomenon,Phormidium, andRaphidiopsis, were significantly and positively correlated to dissolved total P concentration. The results suggested that the phytoplankton biomass in Shahe Reservoir was mainly controlled by climatic factors, such as temperature and precipitation. However, N and P also had a strong influence on biomass and population structure of the phytoplankton as well as on proliferation of blooms. To avoid algal blooms in reservoirs located in southeast China, we suggest that both N and P should be reduced to grade II level of the Chinese surface water standard; more specifically, total N needs to be lower than 0.50 mg/L and total P needs to be lower than 0.025 mg/L. [ABSTRACT FROM AUTHOR]

Nutrient discharge during storm events is a critical pathway for nutrient export in semi-arid catchments. We investigated nutrient dynamics during three summer storms characterized by different rainfall magnitude in 2012 in a semi-arid catchment of northern China. The results showed that, in response to storm events, nutrient dynamics displayed big variation in temporal trends of nutrient concentration and in nutrient concentration-flow discharge relationships. Nutrient concentrations had broader fluctuations during an extreme storm than during lesser storms, whereas the concentration ranges of the a moderate storm were no broader than those of a smaller one. The different concentration fluctuations were caused by storm magnitude and intensity coupled with the antecedent rainfall amount and cumulative nutrients. Correlation coefficients between nutrient concentrations and flow discharge varied from positive to negative for the three different events. There were no consistent hysteresis effects for the three different events, and no hysteresis effects were observed for any of the variables during the moderate storm (E2). Our findings provide useful information for better understanding nutrient loss mechanisms during storm events in semiarid areas of a monsoon climate region. [ABSTRACT FROM AUTHOR]

Abstract: There are two kinds of land policies, the smallholding land policy (SLP) and the farmland policy (FLP) in China. The farmland nutrient dynamics under the two land policies were analysed with the soil system budget method. The averaged nitrogen (N) input of the SLP and the FLP over sixteen years increased about 23.9% and 33.3%, respectively and the phosphorus (P) input climbed about 39.1% and 42.3%, respectively. The statistical analysis showed that the land policies had significant impacts on N and P input from fertilizer and manure, but did not obviously affect the N input from seeds and biological N fixation. The efficiency percentage of N of the SLP and the FLP climbed about 54.5% and 59.4%, respectively, and the P efficiency improved by 52.7% and 82.6%, respectively. About the nutrient output, the F-test analysis indicated that the land polices had remarkable impacts on N output by crop uptake, ammonia volatilisation, denitrification, leaching and runoff, and P output by uptake, runoff, and leach. The balance showed that the absolute loss of N from land deceased about 43.6% and 46.0%, respectively, in the SLP and the FLP, and P discharge reduced about 34.2% and 75.2%, respectively. The F-test analysis of N and P efficiency and balance of between two polices both indicated that the FLP had significant impact on nutrient dynamic. With the Mitscherlich model, the correlations between nutrient input and crop uptake, usage efficiency and loss were analysed and showed that was a threshold value for the optimal nutrient input with the highest efficiency rate. For the optimal nutrient efficiency, the space for extra P addition was bigger than the N input. The FLP have more advantage than the SLP on the crop yield, nutrient efficiency and environmental discharge. [Copyright &y& Elsevier]

Release from the sediment is an important nutrient source to the water column of global oceans, especially for marginal seas with active biogeochemical processes. Benthic nutrient biogeochemistry and its responses to environmental changes were investigated in the eastern marginal seas of China using a two-layer diffusion-advection-reaction diagenetic model. Overall, the sediment represented the primary nutrient source with fluxes of ~−342 ± 197, −1.25 ± 0.50, and −114 ± 56 × 108 mol/month for dissolved inorganic nitrogen (DIN), phosphate, and silicate, respectively. This could contribute up to ~42% of nutrients requested by primary production (PP), with a DIN/SiO 3 2−/PO 4 3− molar ratio of 273:91:1, which was higher than that in the overlying water (49:47:1). Future benthic nutrient fluxes were predicted under two environmental change scenarios (increasing and decreasing PP and biogenic silica). Our study may help rebuild nutrient budgets in the future and formulate environmental management policies in marginal seas. [Display omitted] • Benthic nutrient dynamics was discussed using an early chemical diagenetic model. • Nitrification was strong within the upper sediments (<1.5 cm) in the YS and ECS. • Release from sediments was the primary nutrient source in the study area. • Benthic regeneration enhanced imbalance of nutrient compositions in water column. • Future benthic nutrient fluxes under multiple environmental pressures were quantified. [ABSTRACT FROM AUTHOR]

The application of organic residues and the release dynamics of nutrients during decomposition may be crucial to improving poplar growth in upland areas. Field experiments were conducted in Guizhou Province, southwestern China, to determine differences in biomass decomposition of four potential mulching materials in one-year-old poplar plantations. Results showed the initial total content of N, P, K, Ca and Mg in the mulches ranged from 30.0 to 35.0 g/kg and was significantly greater in Quercus fabri, Imperata cylindrica var. major and Pteridium aquilinum var. latiuscukum than in Coriaria nepalensis. The weight loss pattern of these four species during decomposition could be best described by a double exponential decay model, and monthly decay rate coefficients (k) were in the order Q. fabri >C. nepalensis>I. cylindrica>P. aquilinum over a one-year period. Total nutrient (N, P and K) release of the four mulching materials ranged from 74.2 to 90.8% of the initial content after one year of decomposition, while nutrients were released in the order K > P>N. Nutrient release was fastest in C. nepalensis followed by Q. fabri, I. cylindrica, and slowest in P. aquilinum. Thus, taking into account initial nutrient content, nutrient additions and decay rates, the sprouts of woody species (Q. fabri and C. nepalensis) with massive foliage proved to be more important as nitrogen sources than the grass or fern. [ABSTRACT FROM AUTHOR]

Litter decomposition and nutrient release of selected dominant synusiae in an old-growth, evergreen, broad-leaved mossy forest on Ailao Mountain, Yunnan, south-west China, were studied over a 22-month period. The species studied were three dominant tall tree species, Lithocarpus xylocarpus Markg., Lithocarpus chintungensis Hsu et Qian and Castanopsis wattii A. Camus; one dominant understory species (the bamboo Sinarundinaria nitida Nakai); and a mixture of dominant mosses (including Homaliodendron scalpellifolium Fleisch, Symphyodon perrottetti Mont., Herberta longifolissa Steph. and Bazzania albicans Horik.). Fast initial litter decomposition was followed by lower rates. Decomposition rates of canopy species and bamboo leaf litter appear to be controlled by the initial concentration of lignin, nitrogen (N) and phosphorus (P) more than by morphological features of the leaves. The decay rate of moss litter was less correlated with nutrient composition and lignin concentration in initial mass. The order of decomposition rates was Castanopsis wattii > L. xylocarpus > L. chintungensis > bamboo > moss. The decomposition rate constants (k) of the leaf litter for the canopy species L. xylocarpus, L. chintungensis and Castanopsis wattii were 0.62, 0.50 and 0.64, respectively, and 0.40 and 0.22 for bamboo and moss, respectively. Turnover time (1/k) for the three canopy species was 1.61 years, 2.0 years and 1.55 years, respectively, and 2.50 years and 4.55 years for bamboo and moss, respectively. The N and P concentration in the decomposing leaf litter increased in the first 6 months and then decreased over the remaining period. There was a relatively rapid initial loss of potassium (K), followed by a slight increase. Each of calcium (Ca) and magnesium (Mg) decreased with time whereas iron (Fe) and manganese (Mn) increased with time to some extent. Nutrient release from decomposing leaf litter was in the order of K > Mg > Ca > N > P > Mn > Fe, except for bamboo... [ABSTRACT FROM AUTHOR]

• Season-induced variation was much higher than spatial variation for foliar nutrient concentrations. • New leaves had the highest nutrient concentrations in a whole seasonal cycle. • Lower crown layers mainly acted as nutrients storage sites. • Higher nutrient retranslocation efficiency was observed in middle and lower crown layers. • Nutrient resorption efficiency was homogeneous in crown. Spatial distribution and season-induced variations in foliar nutrients of tree crowns play key roles in growth, and nutrient retranslocation and resorption from leaves are important mechanisms for trees to cope with sites of diversified fertility. Seasonal dynamics and spatial patterns of foliar macronutrients (Nitrogen (N), Phosphorus (P) and Potassium (K)) as well as nutrient retranslocation and resorption in a series of crown layers were examined in 5-year-old Betula alnoides plantations using a spacing trial (2500 (2 m × 2 m, spacing), 1667 (2 m × 3 m), 1250 (2 m × 4 m), 1111 (3 m × 3 m), 833 (3 m × 4 m) and 625 (4 m × 4 m) stems·ha−1) in south China. Significant effects of planting density on foliar nutrient concentrations and nutrient retranslocation and resorption were absent during a whole seasonal cycle or in each season. Both foliar total P and K concentrations increased significantly with increasing crown depth, whereas an obvious trend was not observed for foliar total N concentration. The season with the lowest foliar nutrient concentration varied with the elements, i.e. summer (Jul) for N, winter (Jan) for P and spring (Apr) for K, whereas the highest was observed in autumn (Oct) for all these macronutrient elements. Among crown layers, differences in nutrient concentrations were much lower in the high growth seasons from October to April than those in other seasons. There were significant differences among crown layers in N and P retranslocation efficiency rather than in nutrient resorption efficiency. Significant differences were absent in both retranslocation and resorption efficiencies of K. The highest nutrient retranslocation efficiency was found in the crown layer 2–3 m above ground level for N and 3–4 m for P. The absence of considerable differences among spacing treatments and crown layers mentioned above might be due to the weak early intra-specific competition induced by planting density, soil fertility or fertilization and nutrient demands of this species. These findings could provide suggestions for implementing proper pruning treatments, improving fertilization regimes and other related forest managements for B. alnoides and even other valuable timber species in the tropical and warm sub-tropical regions. [ABSTRACT FROM AUTHOR]

The Pearl River estuary is an ecologically dynamic region located in southern China that experiences strong gradients in its biogeochemical properties. This study examined the seasonality of nutrient dynamics, identified related environmental responses, and evaluated how river discharge regulated nutrient sink and source. The field investigation showed significant differences of dissolved nutrients with seasons and three zones of the estuary regarding the estuarine characteristics. Spatially, nutrients exhibited a clear decreasing trend along the salinity gradient; temporally, their levels were obviously higher in summer than other seasons. The aquatic environment was overall eutrophic, as a result of increased fluxes of nitrogen and silicate. This estuary was thus highly sensitive to nutrient enrichment and related pollution of eutrophication. River discharge, oceanic current, and atmospheric deposition distinctly influenced the nutrient status. These factors accordingly may influence phytoplankton that are of importance in coastal ecosystems. Phytoplankton (in terms of chlorophyll) was potentially phosphate limited, which then more frequently resulted in nutrient pollution and blooms. Additionally, the nutrient sources were implied according to the cause–effect chains between nutrients, hydrology, and chlorophyll, identified by the PCA-generated quantification. Nitrogen was constrained by marine-riverine waters and their mutual increase-decline trend, and a new source was supplemented along the transport from river to sea, while a different source of terrestrial emission from coastal cities contributed to phosphate greatly. [ABSTRACT FROM AUTHOR]