淡水湿地不同围垦土壤非耕季节呼吸速率差异

选择何种湿地利用方式,使得土壤固碳能力及CO₂气体排放受到的影响最小,是合理利用湿地、减少温室气体排放的关键所在,湿地土壤呼吸不仅受环境条件的影响,还受土壤本身性状的影响。以皖江地区为研究区域,利用定位试验对天然湿地及不同围垦利用方式下土壤在非耕季节CO₂排放通量、大气温度及表层土壤温度进行测定,并对其土壤TOC含量进行分析。结果表明,CO₂排放通量:水稻田[700.70 mg/(m²·h)]> 旱地[433.80 mg/(m²·h)]> 天然湿地[302.66 mg/(m²·h)],天然湿地土壤TOC含量明显高于围垦旱地及水稻田(0-30 cm),说明天然湿地较围垦旱地和水稻田对大气中CO₂浓度贡献最小,能存储更多的碳。探讨了CO₂排放通量与温度的相关性,得出3种土壤类型CO₂排放通量与大气温度和表层土壤温度均呈正相关关系。     

Soil Respiration of Biologically-Crusted Soils in Response to Simulated Precipitation Pulses in the Tengger Desert, Northern China

Soil respiration (SR) is a major process of carbon loss from dryland soils, and it is closely linked to precipitation which often occurs as a discrete episodic event. However, knowledge on the dynamic patterns of SR of biologically-crusted soils in response to precipitation pulses remains limited. In this study, we investigated CO₂ emissions from a moss-crusted soil (MCS) and a cyanobacterialichen-crusted soil (CLCS) after 2, 4, 8, 16, and 32 mm precipitation during the dry season in the Tengger Desert, northern China. Results showed that 2 h after precipitation, the SR rates of both MCS and CLCS increased up to 18-fold compared with those before rewetting, and then gradually declined to background levels; the decrease was faster at lower precipitation amount and slower at higher precipitation amount. The peak and average SR rates over the first 2 h in MCS increased with increasing precipitation amount, but did not vary in CLCS. Total CO₂ emission during the experiment (72 h) ranged from 1.35 to 5.67 g C m-² in MCS, and from 1.11 to 3.19 g C m-² in CLCS. Peak and average SR rates, as well as total carbon loss, were greater in MCS than in CLCS. Soil respiration rates of both MCS and CLCS were logarithmically correlated with gravimetric soil water content. Comparisons of SR among different precipitation events, together with the analysis of long-term precipitation data, suggest that small-size precipitation events have the potential for large short-term carbon losses, and that biological soil crusts might significantly contribute to soil CO₂ emission in the water-limited desert ecosystem.     

滨海防护林土壤CO2排放和土壤因子对计划火烧的响应

为研究林火对滨海沙地森林生态系统碳循环的干扰作用,以尾巨桉防护林(Eucalyptus urophylla×Eucalyptus grandis)和木麻黄防护林(Casuarina equisetifolia)为研究对象,利用LI-8100土壤CO₂通量全自动测量系统测定不同防护林火烧迹地和对照样地的土壤CO₂通量,同时测定样地内土壤温湿度和土壤pH、全量碳氮和矿质氮含量,并分析不同林地土壤CO₂通量与水热因子关系以及土壤理化特性的变化。结果表明：2种防护林火烧迹地土壤CO₂通量均显著低于对照样地,尾巨桉林火烧迹地和对照样地土壤CO₂通量月平均值分别为2.47,3.32μmol/(m²·s),木麻黄林分别为2.48,3.28μmol/(m²·s)。林火干扰后2种防护林土壤温度和湿度均高于对照样地,在指数函数模型中尾巨桉林和木麻黄林10 cm处土壤温度解释土壤总呼吸的10.4%～21.4%,在二项式函数模型中尾巨桉林和木麻黄林10 cm...     

黄土区刺槐林土壤含水量变化对土壤呼吸强度的影响

通过室内培养实验来评估土壤含水量的变化对土壤枯落物层、不同深度土壤层及DOC淋失后的土壤呼吸的影响.采集安塞纸坊沟31a刺槐林土样及林下混合枯落物,通过碱液吸收法测定100％,20％和2％含水量条件下3个深度土样(20,40和60 cm);去除DOC土样(仅100％含水量条件下);3种处理枯落物混合土样(林下混合枯落物、刺槐枯落物和草本类枯落物)培养过程中CO2的累计释放量.结果表明,100％和20％含水量条件下各深度土壤CO2释放量为20 cm土样＞60 cm土样＞40 cm土样;20 cm土样去除DOC后CO2释放量明显减少,40 cm明显增加,60 cm没有明显变化;混合枯落物土样在l00％含水量条件下CO2释放量最高;20％和2％含水量条件下刺槐枯落物CO2释放量明显大于草类,而100％含水量条件下草类枯落物略大于刺槐枯落物.研究证明土壤含水量对SOC组分含量和枯落物种类不同的土壤层呼吸强度存在差异性影响,强降水对DOC的淋失可造成表层土壤呼吸的减弱.     

Carbon Dioxide Emission from Black Soil as Influenced by Land‐Use Change and Long‐Term Fertilization

Land‐use change and soil management play a vital role in influencing losses of soil carbon (C) by respiration. The aim of this experiment was to examine the impact of natural vegetation restoration and long‐term fertilization on the seasonal pattern of soil respiration and cumulative carbon dioxide (CO₂) emission from a black soil of northeast China. Soil respiration rate fluctuated greatly during the growing season in grassland (GL), ranging from 278 to 1030 mg CO₂ m^?2 h^?1 with an average of 606 mg CO₂ m^?2 h^?1. By contrast, soil CO₂ emission did not change in bareland (BL) as much as in GL. For cropland (CL), including three treatments [CK (no fertilizer application), nitrogen, phosphorus and potassium application (NPK), and NPK together with organic manure (OM)], soil CO₂ emission gradually increased with the growth of maize after seedling with an increasing order of CK < NPM < OM, reaching a maximum on 17 August and declining thereafter. A highly significant exponential correlation was observed between soil temperature and soil CO₂ emission for GL during the late growing season (from 3 August to 28 September) with Q₁₀ = 2.46, which accounted for approximately 75% of emission variability. However, no correlation was found between the two parameters for BL and CL. Seasonal CO₂ emission from rhizosphere soil changed in line with the overall soil respiration, which averaged 184, 407, and 584 mg CO₂ m^?2 h^?1, with peaks at 614, 1260, and 1770 mg CO₂ m^?2 h^?1 for CK, NPK, and OM, respectively. SOM‐derived CO₂ emission of root free‐soil, including basal soil respiration and plant residue–derived microbial decomposition, averaged 132, 132, and 136 mg CO₂ m^?2 h^?1, respectively, showing no difference for the three CL treatments. Cumulative soil CO₂ emissions decreased in the order OM > GL > NPK > CK > BL. The cumulative rhizosphere‐derived CO₂ emissions during the growing season of maize in cropland accounted for about 67, 74, and 80% of the overall CO₂ emissions for CK, NPK, and OM, respectively. Cumulative CO₂ emissions were found to significantly correlate with SOC stocks (r = 0.92, n = 5, P < 0.05) as well as with SOC concentration (r = 0.97, n = 5, P < 0.01). We concluded that natural vegetation restoration and long‐term application of organic manure substantially increased C sequestration into soil rather than C losses for the black soil. These results are of great significance to properly manage black soil as a large C pool in northeast China.     

半干旱区不同土地利用方式下土壤呼吸特征

采用动态密闭气室红外CO₂分析法测定了盐碱地、撂荒地和苜蓿地三种土地利用方式下的土壤呼吸速率,并结合水热因子,对不同土地利用方式下土壤呼吸速率的差异性以及其和温度、含水量之间的关系进行了分析。结果表明:三种土地利用类型土壤呼吸速率日变化均呈现单峰型曲线,与气温变化趋势一致,一天中气温最高时的土壤呼吸速率均显著高于其他时间;不同土地利用方式土壤呼吸与水热因子均呈正相关,采用线性关系式来分析土壤呼吸速率与土壤水分含量的关系。不同土地利用方式下土壤呼吸速率与近地面气温、不同深度土壤温度的关系可以用指数方程得到较好的拟合（p < 0.05）,撂荒地土壤呼吸的温度敏感性系数Q₁₀值变化较大,从而对土壤温度的响应更为敏感,且不同深度土壤的Q₁₀值存在较大差异,盐碱地和苜蓿地不同土层的Q₁₀值均在2.0左右变化,与全球Q₁₀的平均水平接近。盐碱地、撂荒地和苜蓿地土壤呼吸与土壤温度和湿度的双变量模型关系显著,比相应的单变量模型更好地解释了土壤呼吸变异。     

农村土地整治项目CO2排放及减排政策下的情景模拟

[目的]揭示农村土地整治的CO_2排放效应,为土地整理的碳排放研究提供科学参考。[方法]在项目预算书编制的基础上,采用IPCC清单法,估算农村土地整治项目的 CO_2排放量,分析影响CO_2排放的关键因子,模拟不同政策情景下农村土地整治项目CO_2排放的变化情况。[结果]项目的 CO_2排放总量约5.50×105t,灌溉与排水工程所占比例最大;水泥是最主要的碳源,占总排放量的92.07%,碳源材料的CO_2排放量直接取决于该类材料的CO_2排放系数及消耗量,间接取决于各单项工程的工程量和工程结构;随着相关节能减排政策力度的加大,减排量也会随之增多。[结论]应在土地整治规划设计中贯彻绿色、低碳、环保的设计理念,重视土地整治的生态效应;加大对水泥、电力、钢铁等能源密集型行业的节能减排力度,严格执行国家减排政策。     

土壤水分对夏玉米农田CO2通量和群体水分利用率的影响

利用ＣＯ₂分析系统,配合波文比装置,在夏玉米全生育期连续测定农田冠层瞬时ＣＯ₂浓度差及农田小气候特征量,并计算了农田冠层瞬时ＣＯ₂通量密度、潜热通量和群体水分利用率。结果表明,群体光饱和点位移是受土壤水分影响的一个辐射能量范围,充沛的太阳辐射能量只有充足水分条件的耦合,才能发挥生产力效益;群体水分利用率与０～６０ｃｍ土层土壤平均相对含水率呈负相关,土壤相对含水率在３０.３％～８０％范围内,水分利用率随相对含水率的增加而降低。     

Soil Air Permeability and Carbon Dioxide Flux Measurements from the Soil Surface

Abstract

Air permeability has been recognized as an index of soil structure and used in attempts to characterize soil pore geometry. The importance of increased carbon dioxide in soil to agriculture comes from the direct effects of carbon dioxide (CO₂) on root respiration of agricultural crops. In this study, the soil air permeability and CO₂ flux values were obtained using two different apparatuses built and designed to measure air permeability and CO₂ flux. Air permeability was obtained in clay soil using two different aggregate sizes. The average values obtained were 9.55×10^?8 and 1.78×10^?7 cm² for the <2-mm and 2- to 5-mm fractions, respectively. Carbon dioxide flux from the soil surface of no‐till and bare plots under winter conditions was measured using another apparatus. The average CO₂ flux for the no‐till plot was 2.88 g/m²‐day and for the bare plot was 1.31 g/m²‐day. These values were within the range of values obtained from other studies.     

水分对苹果园土壤呼吸季节性与年际变化的影响

[目的]了解果园土壤呼吸的季节和年际变化及其影响因素,为退耕还果条件下黄土高原地区土壤碳源汇功能变化研究提供依据。[方法]在长武农田生态系统国家野外站,以盛产期果园为对象,利用土壤碳通量监测系统(Li-COR,Lincoln,NE,USA)连续3 a原位监测了土壤呼吸、土壤水分和温度变化,分析了土壤呼吸的季节性和年际间的变化及其与水分、温度变化之间的关系。[结果]土壤呼吸具有明显的季节和年际变异特征:最高值出现在雨季(7—9月),3 a分别为3.14,3.98,4.71μmol/(m~2·s),最低值出现在11月后,3 a依次为0.99,0.88,0.69μmol/(m~2·s);年际间累积呼吸量变异约21%。土壤呼吸与温度呈显著指数关系,而不同水分状况下土壤呼吸及温度敏感性(Q_(10))不同,当土壤水分含量11.12%时,土壤呼吸为2.01μmol/(m~2·s),当土壤含水量变化于11.12%～23.63%之间时,土壤呼吸为2.24μmol/(m~2·s),当土壤含水量23.63%时,土壤呼吸则为1.38μmol/(m~2·s);相应地不同水分条件下Q_(10)值分别为1.57,1.63和1.38。[结论]土壤水分显著影响黄土区苹果园土壤呼吸和Q_(10),研究结果为黄土区果园生态系统碳汇功能的估算提供了依据。     

土壤水分对夏玉米农田CO2通量和群体水分利用率的影响

利用CO     

Effects of irrigation and plowing on soil carbon dioxide efflux in a poplar plantation chronosequence in northwest China

Soil respiration in forest plantations can be greatly affected by management practices. Irrigation is necessary for high productivity of poplar plantations in semi-arid northwest China. Moreover, plowing is essential for improving soil quality and reducing evaporation. In the present study, the influences of irrigation and plowing on soil carbon dioxide (CO₂) efflux were investigated in poplar plantations in 2007 and 2008. The experiments included three stand age classes receiving three treatments: control, irrigation, and plowing. Mean soil respiration in irrigation treatment stands was 5.47, 4.86, and 4.43?µmol?m^?2?s^?1 in 3-, 8-, and 15-year-old stands, respectively, during the growing season. In contrast, mean soil respiration in control stands was 3.71, 3.83, and 3.98?µmol?m^?2?s^?1 in 3-, 8-, and 15-year-old stands, respectively. During the entire observation period, mean soil respiration in plowing treatment stands increased by 36.2% compared with that in the control stands. Mean soil respiration in irrigation treatment stands was significantly higher than that in the control stands; this was mainly because fine root growth and decomposer activities were greatly depressed by soil drought, since natural precipitation could not meet their water demands. The results also suggest that plowing management can greatly increase soil CO₂ emission by modifying soil structure. After plowing, soil bulk density decreased and soil aeration was greatly improved, leading to greater rates of oxidation and mineralization.     

External impacts of soils as considered with the example of slovakia

Background, Aims and Scope  Being an integral part of nature, soil affects all main natural resources and is simultaneously affected by them. This is due to soil management practices (agriculture, forestry) and to the leaching and emission of soil substances. Soil affects mainly water resources and the open air. In this work, soil nitrate production as a possible cause for nitrate leaching and nitrogen emission from soil into the air was determined and generalized. CO₂ emissions from soil into the air were quantified as well. All data were generalized and evaluated. Methods  The data were obtained by analyzing samples taken from nine different soils in Slovakia during 3 years. Results and Discussion  Between 30 and 50 kg of nitrate nitrogen were produced in non-N-fertilized soils during the growing season. Application of fertilizer N yielded 50 to 90 kg N-NO₃-. About 111 thousand tons of N-NO₃ are produced yearly in all non-N-fertilized agricultural soils in Slovakia. On the average, about 10,061 thousand tons of C-CO₂ can be produced in the soil cover during the growing season (about 4.2 tons of C-CO₂ per ha). Recommendation and Outlook  Published data suggest that it is necessary to decrease soil nitrate production and to reduce CO₂ emissions from soils. The data also attest to a very high level of external effects of soil, including negative effects accelerated mainly by human activities.     

Cassava (Manihot Esculenta Crantz) Yields,Soil Nitrous Oxide Emission,and Soil Nitrogen Transformation Affected by Nitrification Inhibitors in Loamy Sand Soil in Thailand

The effects of nitrification inhibitors (NIs) on soil nitrous oxide (N₂O) emission, soil ammonium (NH₄⁺) and nitrate (NO₃^?), and cassava (Manihot esculenta Crantz) yields were investigated in a loamy sand soil in eastern Thailand. Treatments were chemical fertilizer (CF) and CF plus dicyandiamide (DCD) or neem (Azadirachta indica) oil at two rates of 5% and 10%. DCD had a greater reduction of soil N₂O flux than the neem oil (P<0.10). DCD and neem oil retained NH₄⁺-N in the soil by 79% and 63% (P ≤ 0.10), respectively. The NI effect on soil NO₃^?-N was small due to a low N fertilizer rate. The cassava root yield and N uptake were increased 4–11% and 2–18%, respectively, by use of NIs, but they were only significant for DCD (P ≤ 0.10). These findings suggest that NIs application may be a promising method for minimizing nitrogen loss and enhancing crop yields in a tropical cassava field.     

Correlation between Solvita Labile Amino-Nitrogen and CO2-Burst Soil Health Tests and Response to Organic Fertilizer in a Turfgrass Soil

ABSTRACT

The Solvita Soil Labile Amino-Nitrogen (SLAN) and Soil CO₂-Burst (SSCB) tests are used in soil health assessments. Field experiments were conducted from 2014–2016 in Connecticut, USA to: (1) determine if SLAN and SSCB concentrations are correlated for a sandy loam soil under predominately Kentucky bluegrass (Poa pratensis L.) and tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] turfgrass lawns, and (2) compare the response of SSCB–C and SLAN–N concentrations in relation to varying rates of an organic fertilizer. Concentrations of SLAN–N were positively and significantly (P < .001) correlated with concentrations of SSCB–C for all years, both species, and combinations of years and species (r = 0.477 to 0.754). The response of SSCB–C and SLAN–N concentrations to organic fertilizer rates were positively linear and significant (P < .01) in all cases but one (2014 tall fescue SSCB–C concentrations). Rates of change across fertilizer rates were generally greater for SLAN–N concentrations. There was greater variation within the SSCB test than within the SLAN test. The results suggest that the SLAN and SSCB tests are well-correlated and both may be able to provide an estimate of a turfgrass soil’s N mineralization potential.     

Carbon mineralization in subtropical alluvial arable soils amended with sugarcane bagasse and rice husk biochars

Subtropical recent alluvial soils are low in organic carbon (C). Thus, increasing organic C is a major challenge to sustain soil fertility. Biochar amendment could be an option as biochar is a C-rich pyrolyzed material, which is slowly decomposed in soil. We investigated C mineralization (CO₂-C evolution) in two types of soils (recent and old alluvial soils) amended with two feedstocks (sugarcane bagasse and rice husk) (1%, weight/weight), as well as their biochars and aged biochars under a controlled environment (25 ±2 ℃) over 85 d. For the recent alluvial soil (charland soil), the highest absolute cumulative CO₂-C evolution was observed in the sugarcane bagasse treatment (1 140 mg CO₂-C kg^-1 soil) followed by the rice husk treatment (1 090 mg CO₂-C kg^-1 soil); the lowest amount (150 mg CO₂-C kg^-1 soil) was observed in the aged rice husk biochar treatment. Similarly, for the old alluvial soil (farmland soil), the highest absolute cumulative CO₂-C evolution (1 290 mg CO₂-C kg^-1 soil) was observed in the sugarcane bagasse treatment and then in the rice husk treatment (1 270 mg CO₂-C kg^-1 soil); the lowest amount (200 mg CO₂-C kg^-1 soil) was in the aged rice husk biochar treatment. Aged sugarcane bagasse and rice husk biochar treatments reduced absolute cumulative CO₂-C evolution by 10% and 36%, respectively, compared with unamended recent alluvial soil, and by 10% and 18%, respectively, compared with unamended old alluvial soil. Both absolute and normalized C mineralization were similar between the sugarcane bagasse and rice husk treatments, between the biochar treatments, and between the aged biochar treatments. In both soils, the feedstock treatments resulted in the highest cumulative CO₂-C evolution, followed by the biochar treatments and then the aged biochar treatments. The absolute and normalized CO₂-C evolution and the mineralization rate constant of the stable C pool (K_s) were lower in the recent alluvial soil compared with those in the old alluvial soil. The biochars and aged biochars had a negative priming effect in both soils, but the effect was more prominent in the recent alluvial soil. These results would have good implications for improving organic matter content in organic C-poor alluvial soils.     

Evaluation of the soil fauna impact on decomposition in a simulated coniferous forest soil

Summary Long-term experiments (ca. 2 years) were carried out in laboratory systems that simulated the complexity of a coniferous forest floor. The test materials were partially sterilized by freezing and thawing, and reinoculated with (1) microbes alone or (2) microbes with fauna. Removable microcosms containing birch litter, spruce litter, or humus were inserted into a humus substrate. Two experiments used organic matter only, and another included a layer of mineral soil below the humus. Both were incubated in climate chambers that simulated both summer and winter conditions. The evolution of CO₂ was measured at regular intervals. In order to determine the C content of the leachates, the macrocosms and the microcosms were watered periodically.Soil fauna significantly increased respiration in the litter, but not in the microcosms containing humus. In the later phases of decomposition the presence of fauna had a negative effect. In the total systems the fauna consistently increased the respiration rate. The loss of mass was greater in the presence of fauna, especially during the middle phases (5–11 months), but it was higher in the controls later.Throughout the whole incubation period the decomposition rate was strongly influenced by the composition of the animal community. The interpretation of the results is affected by the fact that the controls, to which no fauna had been added, contained dense populations of microbial feeders (nematodes, rotifers, and protozoans).     

中国农村户用沼气工程建设对减排CO2、SO2的贡献——分析与预测

农村户用沼气工程是中国可再生能源建设的重点项目，可为农村居民生活提供清洁的可再生能源，该工程的建设能减轻农村环境污染，有助于部分缓解全球气候变暖的趋势。该文根据国际通用的减排量计算方法，对中国农村户用沼气替代传统生物质能和煤炭所产生的CO₂和SO₂的减排量进行了计算分析，为制定农村能源发展战略和农村环境发展规划提供参考。研究结果表明，在1996～2003年间，每年可减少CO₂排放39.76～419.39万t，减少SO₂排放2.13～6.20万t。通过对2010、2020和2050年沼气替代农村传统能源减排CO₂和SO₂量的预测，证明农村户用沼气工程的建设可以有效减少CO₂和SO₂的排放。     

Carbon Dioxide in Arable Soil Profiles: A Comparison of Automated and Manual Measuring Systems

Carbon dioxide (CO₂) concentrations in arable soil profiles are influenced by autotrophic and heterotrophic respiration as well as soil physical properties that regulate gas transport. Although different methods have been used to assess dynamics of soil CO₂ concentrations, our understanding of the comparability of results obtained using different methods is limited. We therefore aimed to compare the dynamics in soil CO₂ concentrations obtained from an automated system (GMP343 sensors) to those from a manually operated measurement system (i.e., soil gas sampled using stainless steel needles and rods). In a winter wheat field in Denmark, soil CO₂ concentrations were measured from 29 November 2011 to 14 June 2012 at upslope and footslope positions of a short catena (25 m). Carbon dioxide was measured at 20- and 40-cm soil depths (i.e., within and below the nominal plow layer) using the two measurement systems. Within the measurement range for the GMP343 sensors (0–20,000 ppm), mean results from the two systems were similar within the plow layer at the upslope (P = 0.060) and footslope (P = 0.139) position, and also below the plow layer at the upslope position (P = 0.795). However, results from the two systems deviated for the soil from the footslope position below the plow layer (P = 0.001). These results were partly attributed to larger variation in soil parameters below than within the nominal plow layer. The data suggested that generally the application of either system may be adequate; however, differences may occur in response to soil spatial variability. A better coverage of spatial variability is more easily addressed using manually operated systems, whereas temporal variability can be covered using the automated system. Depending on the aim of the study, the two systems may be used in combination to enhance both spatial and temporal data coverage.     

Greenhouse gas emissions in response to straw incorporation,water management and their interaction in a paddy field in subtropical central China

A field experiment was conducted to study the effects of combination of straw incorporation and water management on fluxes of CH₄, N₂O and soil heterotrophic respiration (Rh) in a paddy field in subtropical central China by using a static opaque chamber/gas chromatography method. Four treatments were set up: two rice straw incorporation rates at 0 (S1) and 6 (S2) t ha^?1 combined with two water managements of intermittent irrigation (W1, with mid-season drainage) and continuous flooding (W2, without mid-season drainage). The cumulative seasonal CH₄ emissions for the treatments of S1W2, S2W1 and S2W2 increased significantly by 1.84, 5.47 and 6.63 times, respectively, while seasonal N₂O emissions decreased by 0.67, 0.29 and 1.21 times, respectively, as compared to S1W1 treatment. The significant increase in the cumulative Rh for the treatments S1W1, S2W1 and S2W2 were 0.54, 1.35 and 0.52 times, respectively, in comparison with S1W2. On a seasonal basis, both the CO₂-equivalents (CO₂e) and yield-scaled CO₂e (GHGI) of CH₄ and N₂O emissions increased with straw incorporation and continuous flooding, following the order: S2W2>S2W1>S1W2>S1W1. Thus, the practices of in season straw incorporation should be discouraged, while mid-season drainage is recommended in paddy rice production from a point view of reducing greenhouse gas emissions.