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Globally, paddy fields are a major anthropogenic source of greenhouse gas (GHG) emissions from agriculture. There is, however, limited understanding of relationships between GHG production with fertilizer management, rice varieties, and soil variables. This information is crucial for minimizing the climatic impacts of rice agriculture. Here, we examined the relationships between soil GHG production and management practices throughout China. The current doses of N‐fertilizer (73–272 kg ha−1) were negatively correlated with rice yield and with CO2 or CH4 production and positively correlated with N2O production, thus suggesting N‐overfertilization. Impacts on soil traits such as decreasing pH or the availabilities of other nutrients could be underlying these relationships. Rice yield was highest, and GHG production was lowest at sites using intermediate levels of P‐ and K‐fertilization. CO2 and CH4 production and emissions were positively related with soil water content. The yield was higher, and N2O productions were lower at the sites with japonica rice. Our results strongly suggest that current high doses of N‐fertilizers could be reduced to thus avoid the negative effects of excessive N input on GHG production without any immediate risk of rice production loss. Current intermediate doses of P‐ and K‐fertilization should be adopted across China to further improve rice production without the risk of GHG emissions. The use of different rice varieties and strategies of water management should be reexamined in relation to crop production and GHG mitigation. [ABSTRACT FROM AUTHOR]

The increasing success of invasive plant species in wetland areas can threaten their capacity to store carbon, nitrogen, and phosphorus (C, N, and P). Here, we have investigated the relationships between the different stocks of soil organic carbon (SOC), and total C, N, and P pools in the plant–soil system from eight different wetland areas across the South‐East coast of China, where the invasive tallgrass Spartina alterniflora has replaced the native tall grasses Phragmites australis and the mangrove communities, originally dominated by the native species Kandelia obovata and Avicennia marina. The invasive success of Spartina alterniflora replacing Phragmites australis did not greatly influence soil traits, biomass accumulation or plant–soil C and N storing capacity. However, the resulting higher ability to store P in both soil and standing plant biomass (approximately more than 70 and 15 kg P by ha, respectively) in the invasive than in the native tall grass communities suggesting the possibility of a decrease in the ecosystem N:P ratio with future consequences to below‐ and aboveground trophic chains. The results also showed that a future advance in the native mangrove replacement by Spartina alterniflora could constitute a serious environmental problem. This includes enrichment of sand in the soil, with the consequent loss of nutrient retention capacity, as well as a sharp decrease in the stocks of C (2.6 and 2.2 t C ha‐1 in soil and stand biomass, respectively), N, and P in the plant–soil system. This should be associated with a worsening of the water quality by aggravating potential eutrophication processes. Moreover, the loss of carbon and nutrient decreases the potential overall fertility of the system, strongly hampering the reestablishment of woody mangrove communities in the future. Here, we have investigated the relationships between the different stocks of soil organic carbon (SOC), and total C, N, and P pools in the plant–soil system from eight different wetland areas across the South‐East coast of China, where the invasive tallgrass Spartina alterniflora has replaced the native tall grasses Phragmites australis and the mangrove communities The invasive success of Spartina alterniflora replacing Phragmites australis increased the store of P in both soil and standing plant biomass (approximately more than 70 and 15 kg P by ha, respectively) in the invasive than in the native tall grass communities suggesting the possibility of a decrease in the ecosystem N:P ratio with future consequences to below‐ and aboveground trophic chains. [ABSTRACT FROM AUTHOR]

Sediment phosphorus (P) speciation plays a critical role in coastal wetland ecosystems, while the response of P speciation to reclamation culture remains unclear. In this study, sediment P species (total P [TP], organic P [Org‐P], inorganic P [IP], iron‐ and aluminum‐bound P [Fe/Al‐P], calcium‐bound P [Ca‐P], loosely adsorbed P [Lsor‐P], P sorption index [PSI], and P adsorption saturation [DPS] are investigated in the natural marsh wetland, 3‐year and 15‐year reclamation culture ponds. Sediment P pollution level and eutrophication risk are evaluated based on the single‐factor standard index (Si) and eutrophication risk index (ERI). Furthermore, a simulation experiment is conducted to reveal the effects of baits input and overlying water aeration on sediment P species and ecological risk. Measured sediment TP, Org‐P, IP, Fe/Al‐P, Ca‐P, and Lsor‐P concentrations are significantly higher in 15‐year culture ponds than in 3‐year culture ponds and natural marsh wetland. Sediment PSI is lower in reclamation culture ponds than in natural marsh wetland, while DPS is just opposite. The Si and ERI are higher in 15‐year culture ponds than in natural marsh wetland, suggesting that reclamation culture significantly increases sediment P pollution level and eutrophication risk. A short‐term simulation experiment further indicates that baits input and overlying water aeration can alter sediment P dynamics and increase sediment P loading. Overall, these results confirm that reclamation culture can make more available P accumulation and thus increase eutrophication risk of adjacent coastal water. Sediment P species, eutrophication risk, and key environment factors following reclamation culture chronosequences of 3 and 15 years, and in natural marsh wetland, are investigated. The results confirm that reclamation caused by fishery activities can make more available P accumulation and thus increase potential eutrophication risk of adjacent coastal water. [ABSTRACT FROM AUTHOR]