Thirty-two% of European soils are thought to suffer soil structural damage by compaction. Temperate agricultural grasslands are particularly vulnerable. Larger vehicles, coupled with extended periods of grazing, and greater soil moisture, result in soil compaction: a component of poor soil health. This reduction in soil health reduces yields and increases emissions of nitrous oxide (N2O) from N application. As grass swards are not tilled regularly, mechanical improvement of structure is restricted. We assessed two non-inversion methods of grassland soil alleviation: mechanical slitting of the surface and shallow soil lifting. These were tested on two contrasting soils (sandy, free draining and silty clay loam, imperfectly drained) for dry matter (DM) yields over three annual silage cuts and emissions of N2O. Alleviation decreased soil bulk density, especially for the clay soil, but gave limited improvement in yield; as the sward lifter reduced the first cut DM yield for both soil types. N2O emissions were enhanced by alleviation, especially, the sandier soil, up to 94% more than the uncompacted control with implications for the potential short-term release of N2O from grassland, (up to 243 kg) associated with improvements to the physical aspects of soil health, for a 150 ha dairy farm.

Straw returning (R) combined with the application of a decomposition agent (RD) can increase crop yield and soil carbon (C) storage. However, the effect of RD on soil nitrous oxide (N2O) emissions in tropical areas remains poorly understood. In this study, an in situ experiment was performed under different water management strategies (long-term flooding or alternate wetting and drying) with the R and RD treatments to evaluate soil N2O emissions and rice yield. The SOC and TN contents were significantly lower under the RD treatment than under the R treatment. The R treatment significantly increased rice yield; however, the yield was further significantly increased under the RD treatment. The soil N2O emissions and yield-scaled N2O emissions were higher under the R treatment than under the no-straw-returning treatment. However, the RD treatment greatly reduced soil N2O emissions and yield-scaled N2O emissions under various water management strategies compared with those under the R treatment. Moreover, yield-scaled N2O emissions were lower in the RD treatment than in the control. The soil N2O emissions and yield-scaled N2O emissions were distinctly higher under alternate wetting and drying than under long-term flooding. Our results indicated that long-term flooding and straw returning with decomposition agents can effectively increase rice yield and reduce soil N2O emissions in tropical areas.

中高纬度地区是全球气候变化的敏感区域，近几十年来，该区年平均气温的增幅远高于全球平均增温幅度。中国东北地区地处中高纬度，是中国湿地的集中分布区之一，区域内湿地碳氮循过程对气候变化极为敏感。基于文献分析，归纳总结了温度升高对中国东北地区湿地温室气体通量的影响及其作用机制，梳理了湿地温室气体源汇功能的变化，在此基础上提出了当前研究中存在的问题并对未来研究进行了展望。总体来说，气温升高引起土壤温度升高、植物生长加快、微生物活性增强以及土壤理化性质的改变，从而影响湿地温室气体的吸收或排放。此外，气温升高可促使东北地区湿地由CH4的弱源向强源以及CO2由汇向源逐渐转变，但对N2O源汇变化的研究还存在较多不确定性。现有研究对东北地区湿地的覆盖还不够全面，缺少长时高频的监测以及多梯度、多因子交互作用的研究。未来应针对上述问题开展综合研究与分析，并进一步探究不同温室气体通量变化的相互影响机制。

Studies of the impact of nitrification inhibitors (NIs), specifically DMPP and DMPSA, on N2O emissions during hot moments have produced conflicting results regarding their effectiveness after rewetting. This study aimed to clarify the effectiveness of NIs in reducing N2O emissions by assessing residual DMP concentration and its influence on ammonia-oxidizing bacteria (AOB) in two pot experiments using calcareous (Soil C, Calcic Haploxerept) and acidic soils (Soil A, Dystric Xerochrepts). Fertilizer treatments included urea (U), DMPP, and DMPSA. The experiments were divided into Phase I (water application to dry period, 44 days) and Phase II (rewetting from days 101 to 121). In both phases for Soil C, total N2O emissions were reduced by 88% and 90% for DMPP and DMPSA, respectively, compared with U alone. While in Phase I, the efficacy of NIs was linked to the regulation of AOB populations, in Phase II this group was not affected by NIs, suggesting that nitrification may not be the predominant process after rewetting. In Soil A, higher concentrations of DMP from DMPP were maintained compared to Soil C at the end of each phase. Despite this, NIs had no significant effect due to low nitrification rates and limited amoA gene abundance, indicating unfavorable conditions for nitrifiers. The study highlights the need to optimize NIs to reduce N2O emissions and improve nitrogen efficiency, while understanding their interactions with the soil. This knowledge is necessary in order to design fertilization strategies that improve the sustainability of agriculture under climate change.

Environmental damage attributed to nitrous oxide (N2O) emissions have received widespread attention. Agricultural sources release substantial amounts of N2O into the atmosphere. However, comparative studies on the effects of different irrigation and fertilization methods, namely, drip fertigation (a combination of fertilizing and irrigation), sprinkler fertigation, and traditional furrow irrigation with chemical fertilizer spraying, on N2O emissions in alkaline soil have been limited. Therefore, three-year in situ field observations were conducted to investigate the effect of these three irrigation and fertilization modes on N2O emissions using the static chamber method over the period 2015-2017. There are significant seasonal variations in soil N2O emission fluxes among alkaline soils under different fertilization and irrigation modes, with emissions peaking in July and August, but no significant difference in yearly variations. The N2O emission intensity of drip fertigation soil was 0.20 kg N t-1 year-1, of sprinkler fertigation soil was 0.38 kg N t-1 year-1, respectively, while of furrow irrigation was 0.91 kg N t-1 year-1, respectively. Moisture and temperature of soil were key factors driving the observed nitrous oxide variations. Compared with traditional furrow irrigation, drip and sprinkler fertigation significantly increased potato yield and decreased N2O emissions in alkaline soil, thus satisfying both yield and environmental protection.

Significant changes in climate and perturbation from human activities have been reported over the Qinghai -Tibetan Plateau (QTP), likely altering the ecosystem nitrogen (N) cycling and thus N2O emission. So far, a number of studies have reported variabilities of N2O fluxes from background soil conditions, or conducted warming and N addition experiments to test these effects; however, a synthesized understanding of warming and N input on soil N2O emission is still lacking for the QTP. Here, based on available studies published for this region, we investigated spatiotemporal patterns of background N2O fluxes and performed a meta-analysis to examine the warming and N-addition effects on N2O emission. Annual N2O fluxes ranged from-0.33 to 2.14 kg N2O-N ha(-1) yr(-1) (mean =0.73), of which their spatial distributions across ecosystems were mainly reflected by mean annual precipitation. N2O fluxes during growing seasons were generally larger than those in non-growing seasons, but hot moments of N2O emission existed during freeze-thawing periods. Our meta-analysis showed that warming had a significantly negative but minor effect on N2O emission from non-permafrost soils, although the effect varied with warming magnitudes and methods. The negative response of N2O flux to warming could be explained by the associated decrease of soil moisture and enhancement of plant N uptake. In contrast, warming-induced thawing increases soil moisture in permafrost soils, which could stimulate N2O emission. N addition exhibited an overall positive impact on N2O emission over the QTP region, with a moderate emission factor (0.8%) lower than the IPCC value. Considering the moderate N2O emission from background soils (< 1 kg N2O-N ha(-1) yr(-1)) and common N limitation across ecosystems, our findings suggest that climate change and enhanced N inputs may not turn the QTP into a globally significant N2O source in the near future.

Permafrost-affected tundra soils are large carbon (C) and nitrogen (N) reservoirs. However, N is largely bound in soil organic matter (SOM), and ecosystems generally have low N availability. Therefore, microbial induced N-cycling processes and N losses were considered negligible. Recent studies show that microbial N processing rates, inorganic N availability, and lateral N losses from thawing permafrost increase when vegetation cover is disturbed, resulting in reduced N uptake or increased N input from thawing permafrost. In this review, we describe currently known N hotspots, particularly bare patches in permafrost peatland or permafrost soils affected by thermokarst, and their microbiogeochemical characteristics, and present evidence for previously unrecorded N hotspots in the tundra. We summarize the current understanding of microbial N cycling processes that promote the release of the potent greenhouse gas (GHG) nitrous oxide (N2O) and the translocation of inorganic N from terrestrial into aquatic ecosystems. We suggest that certain soil characteristics and microbial traits can be used as indicators of N availability and N losses. Identifying N hotspots in permafrost soils is key to assessing the potential for N release from permafrost-affected soils under global warming, as well as the impact of increased N availability on emissions of carbon-containing GHGs.

Climate change is profound in the Arctic where increased snowfall during winter and warmer growing season temperatures may accelerate soil nitrogen (N) turnover and increase inorganic N availability. Nitrous oxide (N2O) is a potent greenhouse gas formed by soil microbes and in the Arctic, the production is seen as limited mainly by low inorganic N availability. Hence, it can be hypothesized that climate change in the Arctic may increase total N2O emissions, yet this topic remains understudied. We investigated the combined effects of variable snow depths and experimental warming on soil N cycling in a factorial field study established along a natural snowmelt gradient in a low Arctic heath ecosystem. The study assessed N2O surface fluxes, gross N mineralization and nitrification rates, potential denitrification activity, and the pools of soil microbial, soil organic and soil inorganic N, carbon (C) and phosphorus (P) during two growing seasons. The net fluxes of N2O averaged 1.7 mu g N2O-N m- 2 h-1 (range -3.6 to 10.5 mu g N2O-N m- 2 h-1), and generally increased from ambient (1 m) to moderate (2-3 m) snow depths. At the greatest snow depth (4 m) where snowmelt was profoundly later, N2O fluxes decreased, likely caused by combined negative effects of low summer temperatures and high soil moisture. Positive correlations between N2O and nitrate (NO3- ) and dissolved organic N (DON) suggested that the availability of N was the main controlling variable along the snowmelt gradient. The maximum N2O fluxes were observed in the second half of August associated with high NO3- concentrations. The effect of growing season experimental warming on N2O surface flux varied along the snowmelt gradient and with time. Generally, the experimental warming stimulated N2O fluxes under conditions with increased concentrations of inorganic N. In contrast, warming reduced N2O fluxes when inorganic N was low. Experimental warming had no clear effects on soil inorganic N. The study suggests that if increased winter precipitation leads to a deeper snow cover and a later snowmelt, total emissions of N2O from low Arctic heath ecosystems may be enhanced in the future and, dependent on dissolved N availability, summer warming may stimulate or reduce total emissions.

Permafrost thawing may lead to the release of carbon and nitrogen in high-latitude regions of the Northern Hemisphere, mainly in the form of greenhouse gases. Our research aims to reveal the effects of permafrost thawing on CH4 and N2O emissions from peatlands in Xiaoxing'an Mountains, Northeast China. During four growing seasons (2011-2014), in situ CH4 and N2O emissions were monitored from peatland under permafrost no-thawing, mild-thawing, and severe-thawing conditions in the middle of the Xiaoxing'an Mountains by a static-chamber method. Average CH4 emissions in the severe-thawing site were 55-fold higher than those in the no-thawing site. The seasonal variation of CH4 emission became more aggravated with the intensification of permafrost thawing, in which the emission peaks became larger and the absorption decreased to zero. The increased CH4 emissions were caused by the expansion of the thawing layer and the subsequent increases in soil temperature, water table, and shifts of plant communities. However, N2O emissions did not change with thawing. Permafrost thawing increased CH4 emissions but did not impact N2O emissions in peatlands in the Xiaoxing'an Mountains. Increased CH4 emissions from peatlands in this region may amplify global warming.

Despite the fact that winter lasts for a third of the year in the temperate grasslands, winter processes in these ecosystems have been inadequately represented in global climate change studies. While climate change increases the snow depth in the Mongolian Plateau, grasslands in this region are also simultaneously facing high pressure from land use changes, such as grazing, mowing, and agricultural cultivation. To elucidate how these changes affect the grasslands' winter nitrogen (N) budget, we manipulated snow depth under different land use practices and conducted a(15)NH(4)(15)NO(3)-labeling experiment. The change in(15)N recovery during winter time was assessed by measuring the(15)N/N-14 ratio of root, litter, and soils (0-5 cm and 5-20 cm). Soil microbial biomass carbon and N as well as N2O emission were also measured. Compared with ambient snow, the deepened snow treatment reduced total(15)N recovery on average by 21.7% and 19.2% during the first and second winter, respectively. The decrease in(15)N recovery was primarily attributed to deepened snow increasing the soil temperature and thus microbial biomass. The higher microbial activity under deepened snow then subsequently resulted in higher gaseous N loss. The N2O emission under deepened snow (0.144 kg N ha(-1)) was 6.26 times than that of under ambient snow (0.023 kg N ha(-1)) during the period of snow cover and spring thaw. Although deepened snow reduced soil(15)N recovery, the surface soil N concentration remained unchanged after five years' deepened snow treatment because deepened snow reduced soil N loss via wind erosion by 86%.