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Ecological stoichiometry provides a powerful tool for integrating microbial biomass stoichiometry with ecosystem processes, opening far-reaching possibilities for linking microbial dynamics to soil carbon (C) metabolism in response to agricultural nutrient management. Despite its importance to crop yield, the role of phosphorus (P) with respect to ecological stoichiometry and soil C sequestration in paddy fields remains poorly understood, which limits our ability to predict nutrient-related soil C cycling. Here, we collected soil samples from a paddy field experiment after seven years of superphosphate application along a gradient of 0, 30, 60, and 90 (P-0 through P-90, respectively) kg.ha-1.yr-1 in order to evaluate the role of exogenous P on soil C sequestration through regulating microbial stoichiometry. P fertilization increased soil total organic C and labile organic C by 1-14% and 4-96%, respectively, while rice yield is a function of the activities of soil β-1,4-glucosidase (BG), acid phosphatase (AP), and the level of available soil P through a stepwise linear regression model. P input induced C limitation, as reflected by decreases in the ratios of C:P in soil and microbial biomass. An eco-enzymatic ratio indicating microbial investment in C vs. P acquisition, i.e., ln(BG): ln(AP), changed the ecological function of microbial C acquisition, and was stoichiometrically related to P input. This mechanism drove a shift in soil resource availability by increasing bacterial community richness and diversity, and stimulated soil C sequestration in the paddy field by enhancing C-degradation-related bacteria for the breakdown of plant-derived carbon sources. Therefore, the decline in the C:P stoichiometric ratio of soil microorganism biomass under P input was beneficial for soil C sequestration, which offered a "win-win" relationship for the maximum balance point between C sequestration and P availability for rice production in the face of climate change.

Soil biogeochemical processes and the ecological stability of wetland ecosystems under global warming scenarios have gained increasing attention worldwide. Changes in the capacity of microorganisms to maintain stoichiometric homeostasis, or relatively stable internal concentrations of elements, may serve as an indicator of alterations to soil biogeochemical processes and their associated ecological feedbacks. In this study, an outdoor computerized microcosm was set up to simulate a warmed (+5°C) climate scenario, using novel, minute-scale temperature manipulation technology. The principle of stoichiometric homeostasis was adopted to illustrate phosphorus (P) biogeochemical cycling coupled with carbon (C) dynamics within the soil-microorganism complex. We hypothesized that enhancing the flux of P from soil to water under warming scenarios is tightly coupled with a decrease in homeostatic regulation ability in wetland ecosystems. Results indicate that experimental warming impaired the ability of stoichiometric homeostasis (H) to regulate biogeochemical processes, enhancing the ecological role of wetland soil as an ecological source for both P and C. The potential P flux from soil to water ranged from 0.11 to 34.51 mg m(-2) d(-1) in the control and 0.07 to 61.26 mg m(-2) d(-1) in the warmed treatment. The synergistic function of C-P acquisition is an important mechanism underlying C∶P stoichiometric balance for soil microorganisms under warming. For both treatment groups, strongly significant (p<0.001) relationships fitting a negative allometric power model with a fractional exponent were found between n-HC∶P (the specialized homeostatic regulation ability as a ratio of soil highly labile organic carbon to dissolved reactive phosphorus in porewater) and potential P flux. Although many factors may affect soil P dynamics, the n-HC∶P term fundamentally reflects the stoichiometric balance or interactions between the energy landscape (i.e., C) and flow of resources (e.g., N and P), and can be a useful ecological tool for assessing potential P flux in ecosystems.

High-strengthened farmland fertilization leads to mass inputs of nutrients and elements to agricultural riparian wetlands. The dissolved organic carbon (DOC) of such wetland sediments is an important intermediate in global carbon (C) cycling due to its role in connecting soil C pools with atmospheric CO2. But the impact of phosphorus (P) on sediment DOC is still largely unknown, despite increasing investigations to emphasize P interception by riparian wetlands. Here, we simulated the temporal influences of exogenous P on sediment DOC of riparian wetlands by integrating gradient P loading at rates of 0%, 5%, 10%, 20%, 30%, and 60% relative to the initial total phosphorus content of the sediment with the purpose of illustrating the role of external P on the complexity of soil DOC in terms of its amount and composition. After incubating for nine months, a dramatic linear correlation between Olsen-P and fluorescent and ultraviolet spectral indices considered DOC skeleton was observed. Together with a more microbial-derived origin of DOC and a reduction of DOC aromaticity or humicity, the excitation-emission matrix had shown a blue shift reflecting a trend towards a simpler molecular structure of sediment DOC after P addition. Meanwhile, the content of soil DOC and its ratio with total organic carbon (TOC) were also increased by P loading, coupled with enhanced values of highly labile organic carbon and two C-related enzymes. While TOC and recalcitrant organic carbon decreased significantly. Such implications of DOC amounts and composition stimulated by external P loading may enhance its bioavailability, thereby inducing an accelerated effect on soil C cycling and a potential C loss in response to global climate change., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Agricultural fertilization may change processes of elemental biogeochemical cycles and alter the ecological function. Ecoenzymatic stoichiometric feature plays a critical role in global soil carbon (C) metabolism, driving element cycles, and mediating atmospheric composition in response to agricultural nutrient management. Despite the importance on crop growth, the role of phosphorous (P) in compliance with eco-stoichiometry on soil C and nitrogen (N) sequestration in the paddy field remains poorly understood in the context of climate change. Here, we collected soil samples from a field experiment after 6 years of chemical P application at a gradient of 0 (P-0), 30 (P-30), 60 (P-60), and 90 (P-90) kg ha(-1) in order to evaluate the role of P on stoichiometric properties in terms of soil chemical, microbial biomass, and eco-enzyme activities as well as greenhouse gas (GHG: CO2, N2O and CH4) emissions. Continuous P input increased soil total organic C and N by 1.3-9.2% and 3%-13%, respectively. P input induced C and N limitations as indicated by the decreased ratio of C:P and N:P in the soil and microbial biomass. A synergistic mechanism among the ecoenzymatic stoichiometry, which regulated the ecological function of microbial C and N acquisition and were stoichiometrically related to P input, stimulated soil C and N sequestration in the paddy field. The lower emissions of N2O and CH4 under the higher P application (P-60 and P-90) in July and the insignificant difference in N2O emission in August compared to P-30; however, continuous P input enhanced CO2 fluxes for both samplings. There is a technical conflict for simultaneously regulating three types of GHGs in terms of the eco-stoichiometry mechanism under P fertilization. Thus, it is recommended that the P input in paddy fields not exceed 60 kg ha(-1) may maximize soil C sequestration, minimize P export, and guarantee grain yields.

Global warming is increasingly challenging for wetland ecological function. A temperature controlled microcosm system was developed to simulate climate change scenarios of an ambient temperature (control) and an elevated temperature (+5 °C). The effects and associated mechanisms of warming on phosphorus (P) fluxes at the sediment-water interface of six subtropical wetlands were investigated. The results indicated that P fluxes were generally enhanced under the experimental warming as measured by higher P concentrations in the porewater and overlying water as well as higher benthic P fluxes. The release of P from sediment to porewater occurred more strongly and quickly in response to experimental warming compared to the subsequent upward transfer into overlying water. The average accumulative benthic P output from the tested wetlands under the experimental warming was greater by 12.9 μg cm(-2) y(-1) (28%) for total P and 8.26 μg cm(-2) y(-1) (25%) for dissolved reactive P, compared to the ambient scenarios. Under warming the redistribution of P fractions in sediments occurred with greater NH(4)Cl-P and lower BD-P (extracted by a bicarbonate buffered dithionite solution) accompanied by greater NaOH-P. The higher temperature enhanced total phospholipid fatty acids. A shift in the microbial community was also observed with a relative dominance of fungi (a 4.7% increase) and a relative decline (by 18%) in bacterial abundance, leading to the higher secretion of phosphatase. Comparing between wetlands, the potential P fluxes in the nutrient-enriched wetlands were less impacted by warming than the other wetland types investigated. Thus wetlands characterized by low or medium concentrations of P in sediments were more susceptible to warming compared to P-rich wetlands., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Water quality in watersheds is severely impacted by nutrient enrichment as a result of agricultural activities. Understanding hydrological effects on P dynamics can optimize the ecological function of riparian wetlands to reduce nonpoint source pollution. The XiaZhuHu wetlands were selected for field P investigation, and two typical hydrological batch studies of 35 d each (a static column observation simulating the dry season, and a steady-flow flume observation simulating the rainy season) were conducted to understand sediment P dynamics and evaluate capacity of P immobilization. The average equilibrium P concentration of 0.02 mg L(-1) among the 31 sampled sediments was generally lower than the average dissolved reactive P concentrations in the overlying water, indicating an ecological role as a P sink. In static simulation observation, there was a fast-pace sorption process during the first 3d followed by a slower paced process, and the mass of P adsorbed per unit sediment surface (MPAS) reached 0.16 mg cm(-2). The temporal curves of P equilibrium between flowthrough water and top sediment (5 cm) were characterized as a quasi "V"-pattern, and the MPAS ranged from -0.04 to 0.46 mg cm(-2) during the steady-flow observation. The newly-trapped P was mainly found in Al-bound P and subsequently as Fe-bound P, which would be helpful for sediment P immobilization. Based on our findings, the sediment of the tested wetlands could retain external P from agricultural land by as much as 10-30 times the area of itself, which accounts for approximately 3.3-10% of the watershed area., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Municipal wastewater discharge is threatening the ecological security of the local water environment. This study investigated the field process performance and microorganism characteristics of enhanced biological phosphorus removal (EBPR) in municipal wastewater treatment plants (WWTPs) in China. The results showed that three WWTPs met the required criteria of phosphorus for discharge (< or = 1 mg/L), but with a low level of Accumulibacter (6.4 to 3.8%, on average) and a relatively high level of Competibacter (3.2 to 9.1%) in sludge. The phosphorus release and uptake rates were varied from 0.224 to 7.770 mg/gVSS x h and 0.386 to 7.901 mg/gVSSh, respectively. Denitrifying polyphosphate-accumulating organisms were estimated to be 28.2% of the polyphosphate-accumulating organisms. Sludge characteristics (phosphorus release and uptake rates) were positively correlated with the abundance of Accumulibacter and negatively correlated with the proportion of Competibacter. Moreover, the lower the ratio of anaerobic phosphorus/acetate (e.g., 0.496) is, the more abundant the Competibacter would be. Further discussion on an improvement strategy for these WWTPs for EBPR should be comprehensively based on the data of periodic investigations on field operation, sludge activities, and microbial populations.

The poor quality of effluent discharged by municipal wastewater treatment plants (WWTPs) is threatening the safety of water ecology. This study, which integrated a field survey, batch tests, and microbial community identification, was designed to improve the effectiveness of the enhanced biological phosphorus removal (EBPR) process for WWTPs. Over two-thirds of the investigated WWTPs could not achieve total P in effluent lower than 0.5 mg/L, mainly due to the high ratio of chemical oxygen demand to P (28.6-196.2) in the influent. The rates of anaerobic P release and aerobic P uptake for the activated sludge varied from 0.22 to 7.9 mg/g VSS/h and 0.43 to 8.11 mg/g VSS/h, respectively. The fraction of Accumulibacter (PAOs: polyphosphate accumulating organisms) was 4.8 ± 2.0% of the total biomass, while Competibacter (GAOs: glycogen-accumulating organisms) accounted for 4.8 ± 6.4%. The anaerobic P-release rate was found to be an effective indicator of EBPR. Four classifications of the principal components were identified to improve the EBPR effluent quality and sludge activity., (Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.)

A field experiment located in TaiHu Lake Basin in China was conducted, by application of superphosphate or a mixture of superphosphate with manure, to elucidate the interception of P export during a typical rice growing season through 'zero-drainage water management' combined with sound irrigation, rainfall forecasting and field drying. P concentrations in floodwater rapidly declined before the first event of field drying, and subsequently tended to return to the background levels. Before the first field drying TPP was the predominant P form in floodwater on fields with no P input, DRP on plots that received superphosphate only, and DOP on plots treated with the mixture of superphosphate and manure. Thereafter TPP became the major form. No P export was found from the paddy fields, but a retention of 0.65kgha(-1), mainly due to soil P sorption. The results recommend the zero-drainage water management for full-scale areas for minimizing P export.

Nonpoint-source pollution by phosphorus (P) poses a threat to waters in the Taihu Lake basin in China. The potential transfer of P in rice (Oryza sativa L.) fields through surface drainage and subsurface flow was investigated under simulated conventional irrigation-drainage management. Surface drainage events were conducted to avoid overflow across the plots after heavy rainfall and for rice harvest, at which time P losses were also investigated. This study was conducted in 2001 in a long-term rice field experiment. The experimental plots were treated with 0, 26, or 52 kg P ha(-1) as superphosphate or 26 kg P ha(-1) with equal parts of P supplied as superphosphate and pig manure. Phosphorus concentrations and loads in field floodwater on plots receiving P rapidly declined in a nonlinear manner before the first drainage, three weeks after fertilizer application. The combined application of fertilizer and manure P resulted in higher P transfer potential in field floodwater than with fertilizer P alone one week after P application. Phosphorus concentrations in interflow water sampled by Teflon suction cups inserted at a depth of 150 to 200 mm gradually increased within two weeks after P application, then declined. The concentration of P in interflow water was related to soil P buildup from long-term P application, as well as recently applied P. The 26 kg P ha(-1) treatment (the conventional P rate in this region) resulted in a loss of 0.74 kg total phosphorus (TP) ha(-1) and a drainage-weighted average concentration of 0.25 mg TP L(-1) from the three surface drainage events. Results indicate that avoiding overflow drainage after P input and extending the time between P application and drainage may reduce P losses from rice paddies.

The hydrometer method to measure manure specific gravity and subsequently relate it to manure nutrient contents was examined in this study. It was found that this method might be improved in estimation accuracy if only manure from a single growth stage of pigs was used (e.g., nursery pig manure used here). The total solids (TS) content of the test manure was well correlated with the total nitrogen (TN) and total phosphorus (TP) concentrations in the manure, with highly significant correlation coefficients of 0.9944 and 0.9873, respectively. Also observed were good linear correlations between the TN and TP contents and the manure specific gravity (correlation coefficients: 0.9836 and 0.9843, respectively). These correlations were much better than those reported by past researchers, in which lumped data for pigs at different growing stages were used. It may therefore be inferred that developing different linear equations for pigs at different ages should improve the accuracy in manure nutrient estimation using a hydrometer. Also, the error of using the hydrometer method to estimate manure TN and TP was found to increase, from +/- 10% to +/- 50%, with the decrease in TN (from 700 ppm to 100 ppm) and TP (from 130 ppm to 30 ppm) concentrations in the manure. The estimation errors for TN and TP may be larger than 50% if the total solids content is below 0.5%. In addition, the rapid settling of solids has long been considered characteristic of swine manure; however, in this study, the solids settling property appeared to be quite poor for nursery pig manure in that no conspicuous settling occurred after the manure was left statically for 5 hours. This information has not been reported elsewhere in the literature and may need further research to verify.

A special rice field experiment was conducted to investigate the characteristic and mechanism of phosphorus (P) loss potential in subsurface runoff from rice field. Teflon Suction Cups (TSC) were inserted into tested plots in 15-20 cm in the rice field for water sampling dynamically. The range of molybdate reactive phosphorus (MRP) in sub-surface runoff were 0.110-0.273 mg/L, 0.085-0.285 mg/L during growth seasons of early rice and later rice, respectively. The magnitude of MRP concentrations in subsurface runoff in 15-20 cm from rice field was more consistent with trend of soil P accumulation (expressed as Olsen-P) due to P application. P concentration and its expected loss loading in the subsurface runoff in 15-20 cm in the rice field were not affected by P application combined with manure.

Aims: Microbial-driven biogeochemical cycles of phosphorus (P) in wetlands subjected to global climate warming result in a downstream eutrophication risk. However, how warming influences P associated with microbial shifts in wetland soils is largely unknown.Methods: A custom-built, novel microcosm that simulated climate warming was established under ambient temperature and elevated warming conditions (+ 3 °C). 31P nuclear magnetic resonance (31P-NMR) technology was used to characterize different P forms and high-throughput sequencing of 16S rRNA gene was used to identify microbial community and functional potentials in wetland soils varied with nutrition status.Results: Soil P forms were dominated by orthophosphate. The dynamic changes of different P forms in response to warming were mainly observed in high nutrition wetlands. The relative abundance of orthophosphate and polyphosphate (inorganic) significantly (p < 0.05) decreased, which was accompanied with increased phosphonate (organic) under warming. Consistently, soil microbial community shifts were also found in high nutrition wetlands, especially in fall with significantly (p < 0.05) increased relative abundance of Alphaproteobacteria and Betaproteobacteria and decreased Clostridia under warming. The microbial functions related to catabolism, the transport, degradation and release of P were enriched under warming. Changed microbial community may have altered the overall functional potentials which were responsible for P dynamics.Conclusions: Soil microbial community shifts in response to experimental warming were season-based. Microbial changes and P shifts from high nutrition wetlands were more sensitive to warming. The changed microbial community under warming conditions may trigger the loss of orthophosphate through the altered functional potentials. These findings aid to better understand microbial-driven biogeochemical cycles of P in wetland soils under future climate changes. [ABSTRACT FROM AUTHOR]

Microbial-driven biogeochemical cycles in wetlands impacted by global warming pose a potential downstream eutrophication risk. However, the consequences of ongoing warming on the functional and metabolic potential of sediment microbial communities are largely unknown. We incubated sediment samples under both ambient temperature conditions (control) and simulated warming conditions of 5°C above ambient temperature (warmed) using a novel field microcosm system. In warmed samples, we observed in situ a decreased thickness of the oxidized sediment layer and associated lower sediment redox potential. GeoChip 4.0, a comprehensive functional gene microarray, demonstrated that many functional genes that are involved in oxidation-reduction reactions and in phosphorus (P) degradation were preferentially enriched under warming conditions. The enriched genes included those genes encoding carbon monoxide dehydrogenase, acetyl-CoA carboxylase biotin carboxylase ( ppc), and ribulose-1,5-bisphosphate carboxylase (Rubisco) for carbon fixation; nitrate reductases ( narG) and nitrous oxide reductases ( nosZ) for denitrification; cytochrome c for metal reduction; and exopolyphosphatase ( ppx) for polyphosphate degradation. The redox potential was one of the most significant parameters linked to microbial functional gene structure. These results demonstrate that the enhanced hypoxia and anaerobic metabolic pathways accelerated sediment P mobilization in freshwater wetland subject to warming, raising the potential of water eutrophication. [ABSTRACT FROM AUTHOR]

Summary: Excessive nutrient loading and changing hydrological regimes can significantly impact the ecological function of wetland ecosystems. Three wetland sediment samples collected from West Lake, Xiazhuhu Wetland and Baoyang River in the Taihu Lake Watershed, China, were compared to understand the P retention properties responding to hydrological regimes by using static column and steady-flow flume laboratory-scale experiments. Sediment in Xiazhuhu Wetland currently function as a P sink with equilibrium P concentration (EPC0) values of 0.010mgL−1, while sediments from West Lake and Baoyang River, have EPC0 values of 0.050mgL−1 and 0.023mgL−1, respectively, and serve as an internal P source. The P retention by sediments ranged from 17.20 to 22.61mgm−2 d−1 under 35-d static conditions, while sediment beds continuously fed by the simulated inflow water containing 2mgL−1 P ranged from 59.20 to 171.93mgm−2 d−1. The P removal capacities by sediments were higher during the rainy season than the dry season when wetlands were subjected to excessive P input. Since the majority of external P stored in sediment is in the form of Al-P (e.g., for Xiazhuhu wetland), the application of alum to water column could potentially increase the P retention capacity of sediment. [ABSTRACT FROM AUTHOR]

• Phosphorus (P) additions significantly increase respiration (R w) rates of wood. • P additions significantly increase the temperature sensitivity of R w. • Woods emit 20.29 kg CO 2 /ha/yr per 1 kg P /ha/yr added to evergreen-forests. • Our results provide insight into how and why R w would respond to global change. Phosphorus (P) deposition plays a vital role in determining forest productivity and influencing microbial decomposer communities and activities. Wood plays a key role in forest carbon (C) dynamics because it contains a sizeable proportion of total forest C. However, the effects of increasing P deposition on wood respiration (R w) in subtropical evergreen forests are still unclear. In this study, we conducted a four-year field factorial fertilization experiment in a subtropical Chinese evergreen forest to investigate the influences of simulated changes in P deposition at three levels (e.g., 0 (control), 30 (P1), and 60 (P2) kg P/ha/yr) on the R w of Lithocarpus glaber (Thunb.) Nakai (LI). We found that R w showed significantly higher sensitivity (Q 10) to wood temperature than to air temperature. The R w rate was significantly and positively correlated with the wood microbial decomposer community (including fungi and bacteria), wood temperature and available P. Compared to the control treatment, the P1 and P2 treatments increased the mean annual R w by approximately 1.82 and 0.98 times, respectively. P deposition also accelerated the Q 10 of R w. Meanwhile, on average, wood emitted 20.29 kg CO 2 /ha/yr per 1 kg P/ha/yr added, which declined when P deposition increased above a P saturation threshold of 30 kg P/ha/yr. Our results provide insights into the influences of P deposition on carbon dioxide emissions from wood and also on decomposition rates in subtropical evergreen forests under the rising temperatures expected in the coming decades. [ABSTRACT FROM AUTHOR]

Mn3(PO4)2⋅3H2O is synthesized by a new precipitation method. Anhydrous EtOH is dropped quickly into an aqueous solution of MnSO4 and NH4H2PO4 followed by drying of the precipitate at 80 °C for 12 h. A LiMnPO4/C composite is obtained from a mixture of the prepared Mn3(PO4)2⋅3H2O precursor, NH4H2PO4, Li2CO3, and glucose in the molar ratio of 1:1:1.5:0.58 (Ar atmosphere, 550--700 °C, 6 h). The LiMnPO4/C composite prepared at 650 °C shows discharge capacities of 141.7, 133.5, 126.6, 119.9, 109, 88.7, and 56.6 mAh/g at rates of 0.05, 0.2, 0.5, 1, 2, 5, and 10C, respectively. The material retains 95.2% of its initial discharge capacity after 100 cycles at 0.5C. [ABSTRACT FROM AUTHOR]