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• Breeding habitat can influence rice frog abundance and morphology. • Rice frog in farmland ditches exhibited highest abundance and lowest body condition. • Diverse waterbody types in agricultural landscapes benefit rice frog population. Amphibians are threatened by the intensification of agriculture throughout the world. Several studies have considered the morphology of animals to be an indicator of the health of a population, but differences in anuran morphology (especially body condition) in different breeding habitats in agricultural landscapes remain largely unknown. In this study, we investigated differences in the abundance and morphology of the rice frog (Fejervarya multistriata) in three waterbody types (ten farmland irrigation ditches, ten fruit forest drainage ditches, and ten lotus ponds) in agricultural landscapes in Shanghai, China. We sampled the snout–vent length, body mass, and body condition index for 206 individual rice frogs from the three types of waterbody. Our results showed that the abundance of rice frogs was higher in farmland irrigation ditches than in the other two habitats, whereas the snout–vent length, body mass, and body condition index of rice frogs were lower in farmland irrigation ditches than in the other two habitats. Our results suggest that breeding habitats in agricultural landscapes have different effects on rice frog abundance and morphology, and that constructing diverse waterbodies (other than farmland irrigation ditches) in the same agricultural landscape might benefit the condition of rice frogs. [ABSTRACT FROM AUTHOR]

• RE N and ANUE were 6.8 % and 33 % in Chinese plastic-shed vegetable production. • Exponential relationship well explains the response of N 2 O emission to N rate. • Combined synthetic fertilizer with manure at > 800 kg N ha−1 increase N 2 O emission. • There is a trade-off between soil fertility improvement and N 2 O mitigation. Currently, China has approximately four million hectares of intensively cultivated plastic-shed vegetable production, i.e., with excessive nitrogen (N) fertilization and high irrigation. Plastic-shed vegetable production has helped meet the rapidly increasing consumer demand for fresh vegetables while improving heat, light, and land utilization efficiencies, resulting in very high vegetable yield. We collected all studies from the 1980s to 2020 on N 2 O emissions and N fertilization associated with plastic-shed vegetable production at 40 field sites in China. Fertilizer N utilization efficiencies and N 2 O emissions that were affected by fertilizer N rate and type, irrigation, growth duration, nitrification inhibitors, and soil properties were systematically examined. The results revealed that fertilizer N efficiencies in plastic-shed vegetable production significantly decreased with increasing N fertilization rate. The average N recovery efficiency (RE N) and apparent N use efficiency (ANUE) were 6.8 % and 33 %, respectively; much lower than those of cereal crop production in the same region. In fruit and leafy vegetable production, N 2 O emissions exhibited an exponential and linear relationship with the fertilizer N rate, respectively, and the average contributions of fertilizer N to N 2 O emissions were 68 % and 70 %, respectively. Compared with synthetic N fertilizer or manure alone, combination of synthetic fertilizer with animal manure significantly increased the N 2 O emissions and emission factors (EFs) at high N fertilization rates (>800 kg N ha−1 season−1), but there were no significant differences among fertilizer types at N rate <800 kg N ha−1 season−1. Nitrification inhibitors reduced N 2 O emissions by 24.0 % (95 % confidence intervals [CI]: 19.2 %–28.9 %), and water-saving irrigation is the other effective measure to reduce emissions. Plastic-shed soils with neutral pH, high organic carbon content (> 30 g kg−1), growth period of >100 d, and higher irrigation increased the responses of N 2 O emission to N fertilization. As plastic-shed soils are continuously and intensively farmed, soil properties will be negatively affected, and should be considered together with fertilization and irrigation to maintain high vegetable yield and low N 2 O emissions. Our study highlighted that the exponential relationship was more appropriate to predict the N 2 O emissions in plastic-shed vegetable production, and our findings help to optimize fertilizer N input with consideration of crop yield and greenhouse gas emission. [ABSTRACT FROM AUTHOR]

• Less than 5 kg nitrate-N ha−1 is annually leached from 1-m soil in northeast China. • Long term incorporation of full straw increases nitrate leaching intensity. • Reducing nitrogen doses is an effective way to reduce nitrate leaching intensity. • Nitrate leaching of cultivated Phaeozems is sensitive to climate warming. • Nitrogen dose, precipitation and temperature jointly regulate nitrate leaching. Nitrate (NO 3 −) leaching from agricultural soils poses a potential risk for water contamination and a reduction in nutrient use efficiency. However, NO 3 − leaching intensity and its driving forces of cultivated Phaeozems, well-known for its high soil organic content and productivity, is still unclear, especially in regions with cool climates. In this study, a process-oriented biogeochemical model named CNMM-DNDC was validated with observed variables including soil moisture, NO 3 − concentrations and crop yields, which are closely related to NO 3 − leaching. Next, this validated model was used to quantify the NO 3 − leaching intensity of Phaeozems cultivated with maize in northeastern China in 1990 − 2015. The regional simulations showed that NO 3 − leaching intensities of maize fields (0 − 5 kg N ha−1 yr−1 for most 10 × 10 km2 grids) were lower than those in other Phaeozem regions with warmer climates (29 − 49 kg N ha−1 yr−1). In addition, the results of temperature scenarios also imply that global warming could potentially increase the risk of NO 3 − leaching from cultivated Phaeozems in this study region with cool climates, due to the high temperature sensitivity. Reducing nitrogen doses would be an effective strategy to alleviate the risk of water contamination by reducing the regional leaching amount by 15 % with 5% less applied nitrogen. The scenario simulation indicates that the incorporation of full straw would lead to less NO 3 − leaching in the near term, but more intensive leaching in the long term. A significant nonlinear relationship was found between the simulated NO 3 − leaching intensity and the product of average annual nitrogen dose, average annual precipitation and exponential of average annual air temperature at the county scale. This relationship may provide a simple approach for identifying the potential vulnerable zones prone to nitrogen loss by NO 3 − leaching. As this study suggests, the process-oriented CNMM-DNDC model shows the capacity to quantify long term NO 3 − leaching at the regional scale, which is potentially a robust tool for developing the best management strategies to mitigate/prevent water nitrogen contamination in the Phaeozem regions. [ABSTRACT FROM AUTHOR]

Alpine meadows are the largest grasslands in China. Greenhouse gas exchanges between alpine meadows and the atmosphere are highly uncertain due to the lack of year-round flux measurements. In this study, the methane (CH 4 ) and nitrous oxide (N 2 O) fluxes in an alpine Potentilla fruticosa shrub meadow in the Qinghai-Tibetan Plateau were investigated using the static, opaque chamber-gas chromatography method between April 2012 and April 2015. The annual CH 4 uptake (1.33–1.35 kg C ha −1 yr −1 ) and Q 10 value (1.79) were at the low end of the range for natural grasslands in China, which indicated that global warming at the same extent would result in less of an increase in the CH 4 sink in the Qinghai-Tibetan Plateau, compared to other grassland areas. The N 2 O emissions during the spring thaw period showed a tremendous inter-annual variation (0.03 to 0.14 kg N ha −1 ), which was closely linked to the variation in annual precipitation, especially the precipitation of the previous growing season. The high substrate concentrations and soil moisture during the spring thaw periods together provided the conditions for pulse N 2 O emissions. When the pulse N 2 O emissions occurred, emissions from the non-growing seasons dominated (67–74%) the annual total emissions. Thus, a proper sampling frequency (daily to weekly measurements) in non-growing seasons was needed for the quantification of annual fluxes. Four gas chromatographic set-ups (the Ar-CH 4 , N 2 -ascarite, N 2 -CO 2 , and pure N 2 methods) were adopted for N 2 O flux measurements over natural grasslands in China. Using the N 2 -CO 2 method, the annual N 2 O emissions from the alpine shrub meadow were quantified to be only 0.18–0.27 kg N ha −1 yr −1 in the present study. Based on measurements using the first three of the four gas chromatographic set-ups, the conclusion that can be drawn is that unfertilized natural grasslands in China function as marginally weak N 2 O sources, whereas the pure N 2 method may remarkably overestimate the emissions. [ABSTRACT FROM AUTHOR]

Highlights: [•] We measured impacts of land use and insecticides on ladybeetles in cotton. [•] First empirical evidence on landscape effects in a developing country context. [•] Insecticide sprays significantly affected ladybeetle density in cotton. [•] Ladybeetle density was higher in landscapes with more maize. [•] Land use diversity was negatively associated with ladybeetle density. [Copyright &y& Elsevier]

• Legumes increase diazotroph abundance in non-growing season. • High-density Indigofera atropurpurea decrease diazotroph abundance in growing season. • Diazotrophs were significantly affected by legume species and planting density. • Competitive interactions among diazotrophs increased under N-poor conditions. • Rare diazotrophic taxa enhance N fixation in different leguminous shrubs. Diazotrophs have potential for fixing atmospheric nitrogen (N) in terrestrial ecosystems. The effects of legumes on free-living N-fixing diazotrophs in the karst grassland were determined to provide a basis for ecosystem restoration. In a field experiment, diazotroph responses were examined in five treatments: control, low, and high densities of Amorpha fruticosa and Indigofera atropurpurea. The abundance and community composition of diazotrophs were significantly affected by sampling time and the interaction between different leguminous shrubs and planting density. Legume treatments significantly increased diazotroph abundance compared with the control in December (non-growing season). Greater N input with I. atropurpurea at high density in July (growing season) may suppress soil free-living N-fixing bacteria by decreasing diazotroph abundance. Diazotroph diversity was highest under I. atropurpurea in July. Phyllobacteriaceae and Beijerinckiaceae were abundant in the A. fruticosa plots, while Burkholderiaceae , Comamonadaceae , and Geobacteraceae were abundant in the I. atropurpurea plots. Regardless of the treatments, dissolved organic carbon was the key factor driving seasonal changes in diazotroph abundance and community composition. It suggests seasonal changes in temperature and soil moisture that drive nutrient availability (e.g., ammonium N and nitrate N) under planting legumes may explain the variation in diazotroph communities. Legumes reduced negative interactions among the species in network analyses. These findings suggest that increasing N availability by legume N fixation reduced inter-specific competition among the diazotrophs, with essential roles of rare taxa during the restoration of degraded lands in the karst region. [ABSTRACT FROM AUTHOR]