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Insight in the phosphorus (P) flows and P balances in the food chain is largely unknown at county scale in China, being the most appropriate spatial unit for nutrient management advice. Here, we examined changes in P flows in the food chain in a typical agricultural county (Quzhou) during 1980-2017, using substance flow analyses. Our results show that external P inputs to the county by feed import and fertilizer were 7 times greater in 2017 than in 1980, resulting in a 7-fold increase in P losses to the environment in the last 3 decades, with the biggest source being animal production. Phosphorus use efficiency decreased from 51% to 30% in crop production (PUEc) and from 32% to 11% in the whole food chain (PUEf), but increased from 4% to 7% in animal production (PUEa). A strong reduction in P inputs and thus increase in PUE can be achieved by balanced P fertilization, which is appropriate for Quzhou considering a current average adequate soil P status. Fertilizer P use can be reduced from 7276 tons yr -1 to 1765 tons yr -1 to equal P removal by crops. This change would increase P use efficiency for crops from 30% to 86% but it has a negligible effect on P losses to landfills and water bodies. Increasing the recycling of manure P from the current 43%-95% would reduce fertilizer P use by 17% and reduce P losses by 47%. A combination of reduced fertilizer P use and increased recycling of manure P would save fertilizer P by 93%, reduce P accumulation by 100% and P loss by 49%. The results indicate that increasing manure-recycling and decreasing fertilizer-application are key to achieving sustainable P use in the food chain, which can be achieved through coupling crop-livestock systems and crop-based nutrient management., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

China is experiencing severe tropospheric ozone pollution, especially during the summer period in cities. Previous studies have assessed the role of meteorological conditions and anthropogenic precursors in shaping the diurnal variation of ozone concentration in some Chinese cities or the spatial patterns of daytime ozone concentration, but less is known about the spatial variation and main regulators of the diurnal cycle of summer ozone concentrations in Chinese cities. Using monitoring data from 367 cities, we analyzed the spatial patterns and main regulators of daytime maximum, nighttime minimum and diurnal difference of summer (June-August) ozone concentration during 2015-2019. National mean values and standard deviations of daytime maximum and nighttime minimum of summer surface ozone concentration were 124.1 ± 27.5 and 33.4 ± 13.0 μg m -3 , resulting in a diurnal difference of 90.7 ± 25.2 μg m -3 . High values of daytime maximum, nighttime minimum, and diurnal difference of summer ozone concentration occurred in cities in northern China, especially in the North China Plain, and several city agglomerations in southern China. Daytime maximum ozone concentration was higher in cities with higher daytime PM 2.5 and NO 2 concentrations, lower daytime precipitation and lower elevation. Nighttime minimum ozone concentration increased with lower nighttime precipitation, lower NO 2 concentration and CO concentration, higher nighttime maximum PM 2.5 concentration and higher elevation. Diurnal difference of ozone concentration increased with lower elevation, lower daytime precipitation, and higher diurnal difference of CO and NO 2 concentrations. Our findings highlight different regulators for daytime and nighttime ozone and imply the need of joint regulation of PM 2.5 and NO 2 emissions to control ozone pollution., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Nitrogen (N) deposition has been conventionally thought to decrease forest soil methane (CH 4 ) uptake, while the biome specific and dose dependent effect is poorly understood. Based on a meta-analysis of 63 N addition trials from 7 boreal forests, 8 temperate forests, 13 subtropical and 4 tropical forests, we evaluated the effects of N addition on soil CH 4 uptake fluxes across global forest biomes. When combining all N addition levels, soil CH 4 uptake was insignificantly decreased by 7% in boreal forests, while N addition significantly decreased soil CH 4 uptake by 39% in temperate forests and by 21% in subtropical and tropical forests, respectively. Meta-regression analyses, however, indicated a shift from a positive to a negative effect on soil CH 4 uptake with increasing N additions both in boreal forests (threshold = 48 kg N ha -1 yr -1 ) and temperate forests (threshold = 27 kg N ha -1 yr -1 ), while no such shift was found in subtropical and tropical forests. Considering that current N deposition to most boreal and temperate forests is below the abovementioned thresholds, N deposition likely exerts a positive to neutral effect on soil CH 4 uptake in both forest biomes. Our results provide new insights on the biome specific and dose dependent effect of N addition on soil CH 4 sink in global forests and suggest that the current understanding that N deposition decreases forest soil CH 4 uptake is flawed by high levels of experimental N addition., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Distinct cropland acidification has been reported in China due to nitrogen (N) fertilizer overuse. However, the impacts on food production and thereby on food security are largely unknown. Yield losses in the period 1980-2050 were therefore assessed by simulating soil pH changes combined with derived pH-yield relationships for wheat, maize and rice. If the N fertilizer input continues to increase at 1% annually, the predicted average soil pH decline is about one unit and relative yield losses are expected to increase from approximately 4%-24% during 2010-2050. If the N fertilizer increase stops in 2020 (N2020), the expected losses are approximately 16% in 2050, which is comparable to a scenario of 100% crop residue return (100%RR). However, if 30% of the N fertilizer is replaced by manure N (30%MR), the losses reduce to near 5% in 2050. Soil acidification was predicted to reverse and expected losses are only 2.5% in 2050 in a combined scenario of N2020, 100%RR and 30%MR. Our results illustrate the potential food insecurity induced by cropland acidification and address the necessity of mitigation., (Copyright © 2019. Published by Elsevier Ltd.)

Total nitrogen (N) deposition has declined in many parts of the U.S. and Europe since the 1990s. Even so, it appears that decreased N deposition alone may be insufficient to induce recovery from the impacts of decades of elevated deposition, suggesting that management interventions may be necessary to promote recovery. Here we review the effectiveness of four remediation approaches (prescribed burning, thinning, liming, carbon addition) on three indicators of recovery from N deposition (decreased soil N availability, increased soil alkalinity, increased plant diversity), focusing on literature from the U.S. We reviewed papers indexed in the Web of Science since 1996 using specific key words, extracted data on the responses to treatment along with ancillary data, and conducted a meta-analysis using a three-level variance model structure. We found 69 publications (and 2158 responses) that focused on one of these remediation treatments in the context of N deposition, but only 29 publications (and 408 responses) reported results appropriate for our meta-analysis. We found that carbon addition was the only treatment that decreased N availability (effect size: -1.80 to -1.84 across metrics), while liming, thinning, and prescribed burning all tended to increase N availability (effect sizes: +0.4 to +1.2). Only liming had a significant positive effect on soil alkalinity (+10.5%-82.2% across metrics). Only prescribed burning and thinning affected plant diversity, but with opposing and often statistically marginal effects across metrics (i.e., increased richness, decreased Shannon or Simpson diversity). Thus, it appears that no single treatment is effective in promoting recovery from N deposition, and combinations of treatments should be explored. These conclusions are based on the limited published data available, underscoring the need for more studies in forested areas and more consistent reporting suitable for meta-analyses across studies., (Published by Elsevier Ltd.)

Average nitrogen (N) deposition across Europe has declined since the 1990s. This resulted in decreased N inputs to forest ecosystems especially in Central and Western Europe where deposition levels are highest. While the impact of atmospheric N deposition on forests has been receiving much attention for decades, ecosystem responses to the decline in N inputs received less attention. Here, we review observational studies reporting on trends in a number of indicators: soil acidification and eutrophication, understory vegetation, tree nutrition (foliar element concentrations) as well as tree vitality and growth in response to decreasing N deposition across Europe. Ecosystem responses varied with limited decrease in soil solution nitrate concentrations and potentially also foliar N concentrations. There was no large-scale response in understory vegetation, tree growth, or vitality. Experimental studies support the observation of a more distinct reaction of soil solution and foliar element concentrations to changes in N supply compared to the three other parameters. According to the most likely scenarios, further decrease of N deposition will be limited. We hypothesize that this expected decline will not cause major responses of the parameters analysed in this study. Instead, future changes might be more strongly controlled by the development of N pools accumulated within forest soils, affected by climate change and forest management., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Nitrogen (N) deposition and biological N fixation (BNF) are main external N inputs into terrestrial ecosystems. However, few studies have simultaneously quantified the contribution of these two external N inputs to global NPP and consequent C sequestration. Based on literature analysis, we estimated new net primary production (NPP) due to external N inputs from BNF and N deposition and the consequent C sinks in global boreal, temperate and tropical forest biomes via a stoichiometric scaling approach. Nitrogen-induced new NPP is estimated to be 3.48 Pg C yr -1 in global established forests and contributes to a C sink of 1.83 Pg C yr -1 . More specifically, the aboveground and belowground new NPP are estimated to be 2.36 and 1.12 Pg C yr -1 , while the external N-induced C sinks in wood and soil are estimated to be 1.51 and 0.32 Pg C yr -1 , respectively. BNF contributes to a major proportion of N-induced new NPP (3.07 Pg C yr -1 ) in global forest, and accounts for a C sink of 1.58 Pg C yr -1 . Compared with BNF, N deposition only makes a minor contribution to new NPP (0.41 Pg C yr -1 ) and C sinks (0.25 Pg C yr -1 ) in global forests. At the biome scale, rates of N-induced new NPP and C sink show an increase from boreal forest towards tropical forest, as mainly driven by an increase of BNF. In contrast, N deposition leads to a larger C sink in temperate forest (0.11 Pg C yr -1 ) than boreal (0.06 Pg C yr -1 ) and tropical forest (0.08 Pg C yr -1 ). Our estimate of total C sink due to N-induced new NPP approximately matches an independent assessment of total C sink in global established forests, suggesting that external N inputs by BNF and atmospheric deposition are key drivers of C sinks in global forests., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Anthropogenic emissions of acid precursors have enhanced global occurrence of acid rain, especially in East Asia. Acid rain directly suppresses leaf function by eroding surface waxes and cuticle and leaching base cations from mesophyll cells, while the simultaneous foliar uptake of nitrates in rainwater may directly benefit leaf photosynthesis and plant growth, suggesting a non-linear direct effect of acid rain. By synthesizing data from literature on acid rain exposure experiments, we assessed the direct effects of acid rain on leaf photosynthesis across 49 terrestrial plants in China. Our results show a non-linear direct effect of acid rain on leaf photosynthetic rate, including a neutral to positive effect above pH 5.0 and a negative effect below that pH level. The acid rain sensitivity of leaf photosynthesis showed no significant difference between herbs and woody species below pH 5.0, but the impacts above that pH level were strongly different, resulting in a significant increase in leaf photosynthetic rate of woody species and an insignificant effect on herbs. Our analysis also indicates a positive effect of the molar ratio of nitric versus sulfuric acid in the acid solution on leaf photosynthetic rate. These findings imply that rainwater acidity and the composition of acids both affect the response of leaf photosynthesis and therefore result in a non-linear direct effect., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

To quantify potential nitrogen (N) deposition impacts on peatland carbon (C) uptake, we explored temporal and spatial trends in N deposition and climate impacts on the production of the key peat forming functional group (Sphagnum mosses) across European peatlands for the period 1900-2050. Using a modelling approach we estimated that between 1900 and 1950 N deposition impacts remained limited irrespective of geographical position. Between 1950 and 2000 N deposition depressed production between 0 and 25% relative to 1900, particularly in temperate regions. Future scenarios indicate this trend will continue and become more pronounced with climate warming. At the European scale, the consequences for Sphagnum net C-uptake remained small relative to 1900 due to the low peatland cover in high-N areas. The predicted impacts of likely changes in N deposition on Sphagnum productivity appeared to be less than those of climate. Nevertheless, current critical loads for peatlands are likely to hold under a future climate., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Here we evaluate the performance and limitations of two frequently used model-types to predict trace element solubility in soils: regression based "partition-relations" and thermodynamically based "multisurface models", for a large set of elements. For this purpose partition-relations were derived for As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb, Se, V, Zn. The multi-surface model included aqueous speciation, mineral equilibria, sorption to organic matter, Fe/Al-(hydr)oxides and clay. Both approaches were evaluated by their application to independent data for a wide variety of conditions. We conclude that Freundlich-based partition-relations are robust predictors for most cations and can be used for independent soils, but within the environmental conditions of the data used for their derivation. The multisurface model is shown to be able to successfully predict solution concentrations over a wide range of conditions. Predicted trends for oxy-anions agree well for both approaches but with larger (random) deviations than for cations., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Nitrous oxide (N(2)O) direct soil emissions from agriculture are often estimated using the default IPCC emission factor (EF) of 1%. However, a large variation in EFs exists due to differences in environment, crops and management. We developed an approach to determine N(2)O EFs that depend on N-input sources and environmental factors. The starting point of the method was a monitoring study in which an EF of 1% was found. The conditions of this experiment were set as the reference from which the effects of 16 sources of N input, three soil types, two land-use types and annual precipitation on the N(2)O EF were estimated. The derived EF inference scheme performed on average better than the default IPCC EF. The use of differentiated EFs, including different regional conditions, allows accounting for the effects of more mitigation measures and offers European countries a possibility to use a Tier 2 approach., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

We calculated farm, land, and soil N-budgets for countries in Europe and the EU27 as a whole using the agro-economic model CAPRI. For EU27, N-surplus is 55 kg N ha(-1) yr(-1) in a soil budget and 65 kg N(2)O-N ha(-1) yr(-1) and 67 kg N ha(-1) yr(-1) in land and farm budgets, respectively. NUE is 31% for the farm budget, 60% for the land budget and 63% for the soil budget. NS values are mainly related to the excretion (farm budget) and application (soil and land budget) of manure per hectare of total agricultural land. On the other hand, NUE is best explained by the specialization of the agricultural system toward animal production (farm NUE) or the share of imported feedstuff (soil NUE). Total N input, intensive farming, and the specialization to animal production are found to be the main drivers for a high NS and low NUE., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Various dynamic soil chemistry models have been developed to gain insight into impacts of atmospheric deposition of sulphur, nitrogen and other elements on soil and soil solution chemistry. Sorption parameters for anions and cations are generally calibrated for each site, which hampers extrapolation in space and time. On the other hand, recently developed surface complexation models (SCMs) have been successful in predicting ion sorption for static systems using generic parameter sets. This study reports the inclusion of an assemblage of these SCMs in the dynamic soil chemistry model SMARTml and applies this model to a spruce forest site in Solling Germany. Parameters for SCMs were taken from generic datasets and not calibrated. Nevertheless, modelling results for major elements matched observations well. Further, trace metals were included in the model, also using the existing framework of SCMs. The model predicted sorption for most trace elements well., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

We modelled the combined effects of past and expected future changes in climate and nitrogen deposition on tree carbon sequestration by European forests for the period 1900-2050. Two scenarios for deposition (current legislation and maximum technically feasible reductions) and two climate scenarios (no change and SRES A1 scenario) were used. Furthermore, the possible limitation of forest growth by calcium, magnesium, potassium and phosphorus is investigated. The area and age structure of the forests was assumed to stay constant to observations during the period 1970-1990. Under these assumptions, the simulations show that the change in forest growth and carbon sequestration in the past is dominated by changes in nitrogen deposition, while climate change is the major driver for future carbon sequestration. However, its impact is reduced by nitrogen availability. Furthermore, limitations in base cations, especially magnesium, and in phosphorus may significantly affect predicted growth in the future., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Several monitoring programs have been set up to assess effects of atmospheric deposition on forest ecosystems. The aim of the present study was to evaluate effects on the understory vegetation, based on the first round of a regional (the Netherlands) and a European forest monitoring program. A multivariate statistical analysis showed surprisingly similar results for both data sets; the vegetation appeared to be largely determined by the 'traditional' factors soil, climate, and tree species, but there was a small but statistically significant effect of atmospheric deposition. The effects of deposition include a slight shift towards nitrophytic species at high N deposition in the European network, and towards acidophytic species at high S-deposition in the Dutch network. The relatively small effect of atmospheric deposition is understandable in view of the very large natural variation in environmental conditions. Time series of both vegetation and environment are needed to assess deposition effects in detail., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

The dynamic soil chemistry model SMART was applied to 121 intensive forest monitoring plots (mainly located in western and northern Europe) for which both element input (deposition) and element concentrations in the soil solution were available. After calibration of poorly known parameters, the model accurately simulated soil solution concentrations for most plots as indicated by goodness-of-fit measures, although some of the intra-annual variation especially in nitrate and aluminium concentrations could not be reproduced. Model evaluations of two emission-deposition scenarios (current legislation and maximum feasible reductions) for the period 1970-2030 show a strong reduction in sulphate concentrations between 1980 and 2000 in the soil due to the high reductions in sulphur emissions. However, current legislation hardly reduces future nitrogen concentrations, whereas maximum feasible reductions reduces them by more than half. Maximum feasible reductions are also more effective in increasing pH and reducing aluminium concentrations, mostly below 'critical' values.