Temperature responses of NO and N2O emissions from boreal organic soil

Both NO and N₂O are produced in soil microbial processes and have importance in atmospheric physics and chemistry. In recent years several studies have shown that N₂O emissions from organic soils can be high at low temperatures. However, the effects of low temperature on NO emissions from soil are unknown. We studied in laboratory conditions, using undisturbed soil cores, the emissions of NO and N₂O from organic soils at various temperatures, with an emphasis on processes and emissions during soil freezing and thawing periods. We found no soil freezing- or thawing-related emission maxima for NO, while the N₂O emissions were higher both during soil freezing and thawing periods. The results suggest that different factors are involved in the regulation of NO and N₂O emissions at low temperatures.     

Acid deposition: Perspectives in time and space

Most acid-deposition investigations have been concerned with the impact of nitrogen oxides (NO_x) and sulfur dioxide (SO₂) emissions on Europe and North America. This paper examines three issues beyond this central focus. Major conclusions are 1) ammonia (NH₃) emissions and subsequent nitrogen (N) accumulation in terrestrial ecosystems have the potential to generate significant acidification in terrestrial and aquatic ecosystems; 2) sulfur (S) and N accumulation in environmental reservoirs will not only result in significant and extensive acidification but will also impact the earth's radiation balance, tropospheric oxidizing capacity, ecosystem nutrient balance and groundwater quality; and 3) future emissions will substantially increase in the developing world, especially in Asia. By 2020, Asian emissions of SO₂, NO_x and NH₃ will be equal to or greater than the combined emissions from Europe and North America.     

U.S. Sulfur Dioxide Emissions Trading Program: Results and Further Applications

The use of emissions trading (cap and trade) is gaining worldwide recognition as an extremely effective policy tool. More than 4 million tons of SO₂ have been reduced annually from sources participating in the US SO₂ emissions trading program. Ambient SO₂ levels and sulfate deposition have decreased by over 25 percent in the most sensitive ecosystems. By harnessing market forces, the program has led to significant cost savings. This paper discusses the results of the US SO₂ emissions trading program and emerging efforts in the US and around the world to use emissions trading.     

Composting Hog Manure/Sawdust Mixtures Using Intermittent and Continuous Aeration: Ammonia Emissions

Odorous emissions from manures have become a significant problem. Preliminary work on composting hog manure with sawdust had indicated that intermittent aeration could reduce ammonia emissions during this process. This paper presents results from four additional runs with a total of 22 pilot-scale vessels that have confirmed that ammonia emissions are affected by aeration. The pilot-scale vessels consisted of insulated, stainless steel, 205 L drums that either received continuous (high/low rate, thermostatically controlled blowers) or intermittent (5 min on high rate, 55 min off) aeration. Ammonia emissions, air flow rates, carbon dioxide production, oxygen utilization, and temperatures at four locations in each vessel were monitored. Ammonia emissions under intermittent aeration were roughly 50% less than those from the continuously aerated vessels. However, this appeared to result more from total air flow than from the aeration technique used. A linear regression of emissions versus total air flow data for all vessels yielded a fit of y = 0.1309x + 29.385 (y being total ammonia emitted [in g of N] and x being total air flow [in kg]) with an R² = 0.6808. Since air flow termination was relatively arbitrary, this only means basically, that ammonia emissions were doubled for a quadrupling of air flow. Under intermittent aeration, the minimum oxygen level in the exhaust air occasionally dropped to as low as 1%. So the aeration pattern used probably represents the lowest one suitable for maintaining aerobic conditions. Within this constraint, however, lower air flow appears to be suitable for reducing odorous ammonia emissions.     

中国农业温室气体排放量测算及影响因素研究

农业生产过程所产生的温室气体在全球生产活动温室气体排放总量中占有很大比例,因此对农业温室气体的排放量进行测算并分析其影响因素,对实现农业节能减排有重要意义。本文基于1993―2011年中国农业生产的相关统计数据,借鉴前人关于农业生产中各种温室气体排放源排放系数的研究成果,测算了中国农业生产过程中的CH4、N2O和CO2排放量,并分析了影响因素。结果表明,CH4排放量基本平稳波动不大,N2O排放量从1993年的93.21万t波动增加到2011年的120.51万t,农业生产资料CO2排放量由15 626.98万t增加到31 258.10万t。种植业CO2排放主要分为土壤排放和生产资料排放,土壤CO2排放与大气温度、土壤温度、地表温度和土壤水分有关,生产资料CO2排放主要是由化肥和农药造成的;种植业CH4、N2O排放原因较为复杂,还有待进一步研究;动物肠道发酵CH4、N2O排放的影响因素主要取决于动物种类、饲料特性、饲养方式和粪便管理方式等。     

Effects of nitrogen fertilization and irrigation on N2O emissions from a sandy soil in Germany

The aim of this study was to investigate the effect of supplemental irrigation on the amount of N₂O emissions on a sandy soil in north-east Germany. N₂O flux measurements were carried out over two vegetation periods from the emergence of plants to harvest. The level of N₂O emissions was low, which is typical for sandy soils in north-east Germany. In both periods, irrigation had no increasing effect on N₂O emissions. Relevant factors were the soil temperature and the soil water-filled pore space (WFPS), which were mainly influenced by weather conditions. This may indicate that nitrification was the main source of N₂O emissions. In conclusion, this study has confirmed that sandy soils under weather conditions of north-east Germany generally have a very low potential for N₂O emissions.     

Recent developments in technologies and policies in Germany to control acid deposition

In Germany, acidifying emissions have decreased since the mid-eighties, but are still at levels that cause environmentally harmful acid deposition and thus make further action necessary. The driving force behind such actions is the precautionary principle laid down in pollution control legislation. It is implemented as a requirement to minimize emissions and mandates the parties concerned to formulate and implement emission control requirements based on the state of the art, and to update them as technological advances are made. As the scope for restructuring energy supply and switching to environmentally friendlier sources is very limited in Germany, strategies for controlling inevitable NO_X and SO₂ emissions will continue to be directed at further improving the technical systems (besides necessary changes in lifestyle). Since the large-scale retrofit programmes were initiated in the eighties, technological advances have provided some scope for a further tightening of emission reduction requirements for SO₂ and NO_X. In addition, there is some potential for further reducing these emissions through more energy-efficient demand- and supply-side technology.     

Azolla incorporation and dual cropping influences CH4 and N2O emissions from flooded paddy ecosystems

ABSTRACT

To investigate the influence of Azolla (A. filiculoides Lam.) incorporated as a green manure and its subsequent growth as a dual crop with rice on simultaneous methane (CH₄) and nitrous oxide (N₂O) emissions from a flooded alluvial soil planted with rice, a pot experiment with three treatments, chemical fertilizers (NPK) as the control, incorporation of Azolla as green manure (AGM), and AGM plus basal chemical fertilizers (NPK+AGM) was conducted in Tsuruoka, Yamagata, Japan in 2017. AGM and NPK+AGM treatments significantly increased CH₄ emissions at early rice growth stages before 63 days after transplanting (DAT) by 123.0% and 176.7% compared to NPK, respectively. At late rice growth stages (after 63 DAT), only the NPK+AGM treatment significantly increased CH₄ emission by 22.1% compared to NPK. However, percentage of CH₄ emitted after 63 DAT relative to the seasonal CH₄ emission followed the order of NPK (86.2%) > AGM (76.5%) > NPK+AGM (73.3%). Higher CH₄ emissions from AGM and NPK+AGM before 63 DAT were attributed to the incorporated Azolla, while the higher emissions after 63 DAT in all treatment groups were ascribed to rice photosynthesis. AGM and NPK+AGM treatments significantly decreased N₂O emissions by 71.6% and 81.1% compared to NPK, respectively, at early rice growth stages. Azolla incorporation may have restricted N₂O emission from initial soil nitrate before 63 DAT and not have contributed to N₂O emissions after 63 DAT. Significantly higher grain yields were observed under the AGM (32.5%) and NPK+AGM (36.3%) compared to NPK. Together, AGM and NPK+AGM treatments significantly increased seasonal CH₄ emissions by 31.5% and 43.5%, and decreased seasonal N₂O emissions 3.4- and 4.6- fold compared to NPK, respectively. There were no significant differences in the CH₄ emissions per grain yield among the treatments; however compared to NPK, AGM and NPK+AGM treatments significantly reduced N₂O emissions per grain yield by 78.7% and 84.1%, respectively.     

Methodology and Results of the REKLIP Atmospheric Emission Inventory of the Upper Rhine Valley Transborder Region

In the frame of the climatological project REKLIPwhich involves part of Switzerland, Germany and Franceand concerns the upper Rhine valley, an atmosphericemission inventory has been established with a spatialresolution of a square kilometer and a time resolutionup to one hour. Anthropogenic emissions of SO₂, NO_x,CO, HCl and volatile organic compounds (VOC) divided into thirty compounds or group of compounds as well as biogenic emissions of NMVOC have been taken into account for the year 1990. This inventory has been updated for the following years until 1993 and some hourly emissions inventories have been derived for a period of several days of September 1992,corresponding to a REKLIP intensive measurement campaign.     

Effects of biochar addition on N<Subscript>2</Subscript>O and CO<Subscript>2</Subscript> emissions from two paddy soils

Impacts of biochar addition on nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions from paddy soils are not well documented. Here, we have hypothesized that N₂O emissions from paddy soils could be depressed by biochar incorporation during the upland crop season without any effect on CO₂ emissions. Therefore, we have carried out the 60-day aerobic incubation experiment to investigate the influences of rice husk biochar incorporation (50 t ha⁻¹) into two typical paddy soils with or without nitrogen (N) fertilizer on N₂O and CO₂ evolution from soil. Biochar addition significantly decreased N₂O emissions during the 60-day period by 73.1% as an average value while the inhibition ranged from 51.4% to 93.5% (P < 0.05–0.01) in terms of cumulative emissions. Significant interactions were observed between biochar, N fertilizer, and soil type indicating that the effect of biochar addition on N₂O emissions was influenced by soil type. Moreover, biochar addition did not increase CO₂ emissions from both paddy soils (P > 0.05) in terms of cumulative emissions. Therefore, biochar can be added to paddy fields during the upland crop growing season to mitigate N₂O evolution and thus global warming.     

生物柴油对能源和环境影响分析

生物柴油是从植物或动物脂肪酸通过酯化反应而得到,由于生物柴油无毒,可生物降解和可以再生,因此受到越来越多人的关注。生物柴油的性质和普通柴油非常相似,它能直接被用到发动机上而不需要改动发动机的结构。该文基于美国能源部对生物柴油的统计数据,利用生命循环分析法,对生物柴油从生产到消耗的生命循环中的能量消耗和产出、循环中的排放以及生物柴油汽车尾气排放等方面进行了分析。生命循环开始于普通柴油或生物柴油生产的原料提取,结束于成品油在发动机上的使用。只有分析生命循环中的所有过程,才能确定它对自然环境总量的影响。例如研究温室效应就要对整个生命循环中CO₂的排放进行分析。该文利用生命循环分析法分析了在生产生物柴油或柴油生命循环过程中的能量平衡、温室气体排放及对气体和固体污染物排放,提供了生物柴油生产过程和在发动机上使用的详细数据。分析结果表明∶生物柴油循环的石化能效比大大提高,大约是柴油的4倍;生物柴油循环中CO₂排放大大降低,大约降低了78.4%;发动机排气管有害物质的排放中,除NO_x排放增加8.89%外,CO、HC、PM等有害物质的排放大大降低（分别降低了46%、37%和68%）。     

Efficiency of nitrification inhibitor DMPP to reduce nitrous oxide emissions under different temperature and moisture conditions

Agricultural intensification has led to the use of very high inputs of nitrogen fertilizers into cultivated land. As a consequence of this, nitrous oxide (N₂O) emissions have increased significantly. Nowadays, the challenge is to mitigate these emissions in order to reduce global warming. Addition of nitrification inhibitors (NI) to fertilizers can reduce the losses of N₂O to the atmosphere, but field studies have shown that their efficiency varies depending greatly on the environmental conditions. Soil water content and temperature are key factors controlling N₂O emissions from soils and they seem to be also key parameters responsible for the variation in nitrification inhibitors efficiency. We present a laboratory study aimed at evaluating the effectiveness of the nitrification inhibitor 3,4-dimethylpyrazol phosphate (DMPP) at three different temperatures (10, 15 and 20 °C) and three soil water contents (40%, 60% and 80% of WFPS) on N₂O emissions following the application of 1.2 mg N kg⁻¹ dry soil (equivalent to 140 kg N ha⁻¹). Also the CO₂ and CH₄ emissions were followed to see the possible side effects of DMPP on the overall microbial activities. Nitrogen was applied either as ammonium sulfate nitrate (ASN) or as ENTEC 26 (ASN + DMPP). The application of ENTEC 26 was effective reducing N₂O losses up to the levels of an unfertilized control treatment in all conditions. Nevertheless, the percentage of reduction induced by DMPP in the ENTEC treatment with respect to the ASN varied from 3% to 45% depending on temperature and soil water content conditions. At 40% of WFPS, when nitrification is expected to be the main process producing N₂O, the increase of N₂O emissions in ASN together with temperature provoked an increase in DMPP efficiency reducing these emissions from 17% up to 42%. Contrarily, at 80% of WFPS, when denitrification is expected to be the main source of N₂O, emissions after ASN application decreased with temperature, which induced a decrease from 45% to 23% in the efficiency of DMPP reducing N₂O losses. Overall, the results obtained in this study suggest that DMPP performance regarding N₂O emissions reduction would be the best in cold and wet conditions. Neither CO₂ emissions nor CH₄ emissions were affected by the use of DMPP at the different soil water contents and temperatures.     

Emissions of N2O from soils during cycles of freezing and thawing and the effects of soil water, texture and duration of freezing

Freezing and thawing influence many physical, chemical and biological processes in soils, including the production of trace gases. We studied the effects of freezing and thawing on three soils, one sandy, one silty and one loamy, on the emissions of N₂O and CO₂. We also studied the effect of varying the water content, expressed as the percentage of the water‐filled pore space (WFPS). Emissions of N₂O during thawing decreased in the order 64% > 55% > 42% WFPS, which suggests that the retardation of the denitrification was more pronounced than the acceleration of the nitrification with increasing oxygen concentration in the soil. However, emissions of N₂O at 76% WFPS were less than at 55% WFPS, which might be caused by an increased ratio of N₂/N₂O in the very moist conditions. The emission of CO₂ was related to the soil water, with the smallest emissions at 76% WFPS and largest at 42% WFPS. The emissions of CO₂ during thawing exceeded the initial CO₂ emissions before the soils were frozen, which suggests that the supply of nutrients was increased by freezing. Differences in soil texture had no marked effect on the N₂O emissions during thawing. The duration of freezing, however, did affect the emissions from all three soils. Freezing the soil for less than 1 day had negligible effects, but freezing for longer caused concomitant increases in emissions. Evidently the duration of freezing and soil water content have important effects on the emission of N₂O, whereas the effects of texture in the range we studied were small.     

Trends in wet and dry deposition of sulphur in the United Kingdom

UK data on sulphur deposition trends between the 1960's and 1990's are presented. Long term data sets of sulphur dioxide (SO₂) concentrations at two sites have been analysed and dry deposition determined using a resistance model. Wet deposition has been calculated from non-marine sulphate concentration and rainfall fields for 1978–80 and 1989–93. These maps have been interpolated and corrected for seeder feeder enhancement. The wet deposition of sulphur declined by about 43 % between 1979 and 1993 whereas emissions of sulphur declined by about 32 %. An indication of the trends in sulphur dry deposition is provided by data from Eskdalemuir, a site in southern Scotland where wet deposition and SO₂ concentration have been measured since 1979. Dry deposition at Eskdalemuir has decreased by 70 % and wet deposition by 48 %. Hence, while wet deposition has responded approximately linearly with the decline in UK emissions of sulphur dioxide, dry deposition has declined at twice the rate of decline in UK emissions.     

覆盖材料和厚度对堆存牛粪氨气和温室气体排放的影响

为了研究锯末和稻草2种材料覆盖以及不同厚度的锯末覆盖对牛粪堆存过程中氨气(NH3)和温室气体(N2O、CH4和CO2)排放量的影响,采用静态箱的方法测试了不同覆盖厚度(1、3和5 cm)和2种材料(锯末和稻草)覆盖下牛粪NH3、N2O、CH4和CO2排放量。结果表明,在不同厚度锯末覆盖的试验中,与不覆盖处理组相比,覆盖降低了牛粪NH3和CO2累积排放量,但覆盖显著增加了牛粪N2O和CH4累积排放量(P0.05);3个覆盖处理组内,NH3、N2O和CO2排放量随着覆盖厚度的增加而下降,然而,CH4排放量随着覆盖厚度的增加而升高;1、3和5 cm厚锯末覆盖的牛粪总温室气体排放量分别为108.61、103.57和101.36 g/kg,与1 cm锯末覆盖相比,3和5 cm厚锯末覆盖的牛粪总温室气体排放量显著降低(P0.05)。在相同质量的锯末(2 cm厚)和稻草(6 cm厚)2种材料覆盖的比较试验中,2种材料覆盖都显著降低了牛粪NH3和CO2的累积排放量(P0.05),但同时也显著增加了CH4的累积排放量(P0.05);锯末覆盖增加了牛粪N2O累积排放量(P0.05),而稻草覆盖则降低了牛粪N2O累积排放量(P0.05)。与锯末覆盖相比,稻草覆盖显著增加了CH4的累积排放量(P0.05),但同时显著降低了牛粪CO2的累积排放量(P0.05);锯末覆盖和稻草覆盖牛粪总温室气体排放量分别为101.51和109.46 g/kg,与锯末覆盖相比,稻草覆盖显著增加了牛粪总的温室气体排放量。试验结果表明,较厚的锯末(3和5 cm)覆盖对牛粪NH3和温室气体的减排效果更好。     

Spatial Distribution of Gaseous And Particulate Matter Emissions in Greece

The quantification of air pollutant emissions to theatmosphere, from anthropogenic and natural sources, in Greece is the main focus of the current work. Emissions are spatially and temporally disaggregated in a high resolution grid based on a methodology given in Atmospheric Emissions Inventory Guidebook, CORINAIR. The anthropogenic emissions are equal to those given by UNECE through the EMEP program and an estimation of their spatial distribution in a 5 × 5 km² grid is performed. Furthermore, natural emissions are calculated using the bottom-up approach and are distributed to the 5 × 5 km² grid. The methodology used for the estimation of the spatial and temporal distribution of the emissions is presented as well as the contribution of each individual source in the distribution of gaseous and particulate matter emissions in Greece. Energy production, agriculture and road transport have been recognized as the activities in Greece mainly contributing to the anthropogenic emissions. Other important sources include biogenic VOC and resuspended dust.     

Combined effects of nitrogen deposition and biochar application on emissions of N2O,CO2 and NH3 from agricultural and forest soils

Abstract

Both nitrogen (N) deposition and biochar can affect the emissions of nitrous oxide (N₂O), carbon dioxide (CO₂) and ammonia (NH₃) from different soils. Here, we have established a simulated wet N deposition experiment to investigate the effects of N deposition and biochar addition on N₂O and CO₂ emissions and NH₃ volatilization from agricultural and forest soils. Repacked soil columns were subjected to six N deposition events over a 1-year period. N was applied at rates of 0 (N0), 60 (N60), and 120 (N120) kg Nh a^?1 yr^?1 without or with biochar (0 and 30 t ha^?1 yr^?1). For agricultural soil, adding N increased cumulative N₂O emissions by 29.8% and 99.1% (p < 0.05) from the N60 and N120 treatments, respectively as compared to without N treatments, and N120 emitted 53.4% more (p < 0.05) N₂O than the N60 treatment; NH₃ volatilization increased by 33.6% and 91.9% (p < 0.05) from the N60 and N120 treatments, respectively, as compared to without N treatments, and N120 emitted 43.6% more (p < 0.05) NH₃ than N60; cumulative CO₂ emissions were not influenced by N addition. For forest soil, adding N significantly increased cumulative N₂O emissions by 141.2% (p < 0.05) and 323.0% (p < 0.05) from N60 and N120 treatments, respectively, as compared to without N treatments, and N120 emitted 75.4% more (p < 0.05) N₂O than N60; NH₃ volatilization increased by 39.0% (p < 0.05) and 56.1% (p < 0.05) from the N60 and N120 treatments, respectively, as compared to without N treatments, and there was no obvious difference between N120 and N60 treatments; cumulative CO₂ emissions were not influenced by N addition. Biochar amendment significantly (p < 0.05) decreased cumulative N₂O emissions by 20.2% and 25.5% from agricultural and forest soils, respectively, and increased CO₂ emissions slightly by 7.2% and NH₃ volatilization obviously by 21.0% in the agricultural soil, while significantly decreasing CO₂ emissions by 31.5% and NH₃ volatilization by 22.5% in the forest soil. These results suggest that N deposition would strengthen N₂O and NH₃ emissions and have no effect on CO₂ emissions in both soils, and treatments receiving the higher N rate at N120 emitted obviously more N₂O and NH₃ than the lower rate at N60. Under the simulated N deposition circumstances, biochar incorporation suppressed N₂O emissions in both soils, and produced contrasting effects on CO₂ and NH₃ emissions, being enhanced in the agricultural soil while suppressed in the forest soil.     

Potential and promisingness of technical options for mitigating greenhouse gas emissions from rice cultivation in Southeast Asian countries

ABSTRACT

Paddy fields are considered as one of the most important sources of anthropogenic methane (CH₄) and nitrous oxide (N₂O) emissions. While several technical options have been proposed to reduce these emissions, gaps in data and information based on application of these options in the field are a key barrier to scaling-up. To address these gaps, we conducted a review of literature to analyze the potential of technical options in Southeast Asia (SEA). Using screening criteria based on reliability of experimental data, 31 region-specific cases were selected for the analysis. A meta-analysis indicated that water management options, including single and multiple drainage approaches such as alternative wetting and drying (AWD), significantly reduced CH₄ emissions by 35% as a mean effect size (95% confidential interval: 41–29%), as well as the combined effects of CH₄+N₂O (net GWP) by 29% (36–23%). The effect on reducing CH₄ emissions in the dry season was significantly larger than that in the wet season. Application of biochar reduced both CH₄ and N₂O emissions by 20% (40% to ?7%), while significantly increased rice yield by 28% (8–52%). Other options such as removal of rice straw from the previous crop, composting rice straw and manure, application of sulfate-containing fertilizer, and soil drying in the fallow season also have recognized potential to reduce emissions but require further data and consideration of possible trade-offs. Based on the analysis of mitigation potential, promising technical options were assessed by considering together with constraints and additional co-benefits in order to provide a useful guide for policy makers and rice value chain operators in SEA countries for adopting mitigation options in rice cultivation to tackle climate change and enhance agriculture sector sustainability.     

中国农业碳排放绩效评价及随机性收敛研究——基于SBM-Undesirable模型与面板单位根检验

当前,全局层面及工业视角下的碳排放绩效评价和收敛性分析已趋于成熟,但农业碳排放方面的研究尚十分薄弱。为补充相关研究,对区域农业碳排放总量、绩效及两者的收敛趋势有更清晰的认识,本文在测算2000—2014年我国30个省市农业碳排放总量的基础上,运用SBM-Undesirable模型计算农业碳排放绩效,并通过面板单位根检验方法对全国和各区域的农业碳排放总量及绩效进行了随机性收敛检验。结果显示:1)2000—2014年间,全国农业碳排放量整体呈递增趋势,但各区域排放量差异明显。比较中部与全国、东部和西部各年总量均值,发现2000年的差值分别为3.357 4?106 t,3.965 0?106 t和5.904 7?106 t,到2014年,差距扩大至5.244 8?106 t,7.351 2?106 t和7.681 0?106 t,对应增长比例分别为56.2%、85.4%和30.0%。2)各区域农业碳排放绩效存在显著差异。绩效均值折线图显示,东部平均绩效较高,15年来基本稳定在0.8左右;西部和中部绩效均值较低,绝大多数年份处于0.3~0.5,但西部不断改善,中部则持续下降。3)对总量进行收敛性检验,发现全国、西部、中部呈现明显的随机性分异,仅东部出现随机性趋同;在绩效的收敛性检验中,全国范围内不存在随机性收敛,但东部、中部、西部各自呈俱乐部式随机性收敛态势。随机性收敛检验结果表明,中国农业碳排放总量和绩效不会自动降低到稳态水平,有必要进行相关政策干预,以缩小各省市间的差距。本研究为制定区域间差异化和区域内统一性农业减排政策奠定了基础。     

Effects of biochar application in forest ecosystems on soil properties and greenhouse gas emissions: a review

Purpose

Forests play a critical role in terrestrial ecosystem carbon cycling and the mitigation of global climate change. Intensive forest management and global climate change have had negative impacts on the quality of forest soils via soil acidification, reduction of soil organic carbon content, deterioration of soil biological properties, and reduction of soil biodiversity. The role of biochar in improving soil properties and the mitigation of greenhouse gas (GHG) emissions has been extensively documented in agricultural soils, while the effect of biochar application on forest soils remains poorly understood. Here, we review and summarize the available literature on the effects of biochar on soil properties and GHG emissions in forest soils.

Materials and methods

This review focuses on (1) the effect of biochar application on soil physical, chemical, and microbial properties in forest ecosystems; (2) the effect of biochar application on soil GHG emissions in forest ecosystems; and (3) knowledge gaps concerning the effect of biochar application on biogeochemical and ecological processes in forest soils.

Results and discussion

Biochar application to forests generally increases soil porosity, soil moisture retention, and aggregate stability while reducing soil bulk density. In addition, it typically enhances soil chemical properties including pH, organic carbon stock, cation exchange capacity, and the concentration of available phosphorous and potassium. Further, biochar application alters microbial community structure in forest soils, while the increase of soil microbial biomass is only a short-term effect of biochar application. Biochar effects on GHG emissions have been shown to be variable as reflected in significantly decreasing soil N₂O emissions, increasing soil CH₄ uptake, and complex (negative, positive, or negligible) changes of soil CO₂ emissions. Moreover, all of the aforementioned effects are biochar-, soil-, and plant-specific.

Conclusions

The application of biochars to forest soils generally results in the improvement of soil physical, chemical, and microbial properties while also mitigating soil GHG emissions. Therefore, we propose that the application of biochar in forest soils has considerable advantages, and this is especially true for plantation soils with low fertility.