贡嘎山东坡峨眉冷杉林区土壤CO2排放

在植物生长季对贡嘎山东坡峨眉冷杉林区三种不同类型土壤排放CO2过程进行了连续观测,三种类型土壤CO2排放存在着显著差异,峨眉冷杉滨替林采伐迹地土壤呼吸强度最高,达5．89μmol/m^2sCO2,在各月份中高低依次为9月＞8月＞6月＞7月＞5月＞10月＞11月;峨眉冷杉林土壤呼吸强度次之,为5．76μmol/m^2sCO2在各月份中高低依次为8月＞7月＞9月＞6月＞5月＞10月＞11月;峨眉冷杉演要替林土壤呼吸强度最低,为3．26μmol/m^2sCO2在各月份中高低依次为5月＞7月＞8月＞6月＞9月＞10月＞11月,观测的各种温度指标对土壤CO2排放有明显的影响,分析表明,近地表气温对峨眉冷杉林采伐迹地和演替林土壤CO2排放影响最大,10cm和5cm深地漫地峨眉冷杉土壤CO2排放影响最大,根据观测的土壤品种月平均值计算出土壤CO2排放的通量估计值,峨眉冷杉林采伐迹地土壤CO2排放为223．91kg/hm^2d,峨眉冷杉林土壤排放为218．48kg/hm^2d,峨眉冷杉演替林土壤CO2排放为123．76kg/hm^2d.     

土壤酶活性对温度和CO2浓度升高的响应研究

作为土壤生态系统中的重要组成部分及生物元素循环的积极参与者,土壤酶在陆地生态系统地下生态过程中扮演着十分重要的角色。升高温度和(或)大气CO2浓度可能直接或者间接影响其活性。但目前对温度和(或)大气CO2浓度升高对土壤酶的影响机理、过程及土壤酶对其的响应机制研究相对薄弱。本文初步总结了国内外关于温度和(或)大气CO2浓度升高对土壤酶活性影响研究的现状,并指出了目前研究中存在的不足。     

间伐对杉木林土壤CO2通量的影响

Forest management is expected to influence soil CO₂ efflux (FCO₂) as a result of changes in microenvironmental conditions, soil microclimate, and root dynamics. Soil FCO₂ rate was measured during the growing season of 2006 in both thinning and non-thinning locations within stands ranging from 0 to 8 years after the most recent thinning in Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations in Huitong Ecosystem Research Station, Hunan, China. Soil temperature and moisture were also measured to examine relationships between FCO₂ and soil properties. Forest thinning resulted in huge changes in FCO₂ that varied with time since cutting. Immediately following harvest (year 0) FCO₂ in thinning area increased by about 30%, declined to 20%-27% below pre-cutting levels during years 4-6, and recovered to pre-cutting levels at 8 years post-cutting. A similar temporal pattern, but with smaller changes, was found in non-thinning locations. The initial increase in FCO₂ could be attributed to a combination of root decay, soil disturbance, and increased soil temperature in gaps, while the subsequent decrease and recovery to the death and gradual regrowth of active roots. Strong effects of soil temperature and soil water content on FCO₂ were found. Forest thinning mainly influenced FCO₂ through changes in tree root respiration, and the net result was a decrease in integrated FCO₂ flux through the entire felling cycle.     

高CO2浓度下羊草对土壤干旱胁迫的响应

在高CO2浓度下羊草对土壤干旱胁迫响应的人工模拟试验分析表明，CO2浓度升高对羊草具有“施肥”效应，羊草生物量增加20％以上，光合速率提高50％左右，气孔阻力增大，蒸腾速率下降，水分利用效率提高，土壤干旱胁迫对羊草的影响为负效应，与此相反，高CO2浓度下发生土壤干旱胁迫一定程度抑制了CO2的施肥效应。     

膜下滴灌对土壤CO2与CH4浓度的影响

在温室进行了马铃薯盆栽试验,采用静态暗箱气相色谱法比较了滴灌(D)和漫灌(F)两种不同灌溉制度对土壤CO2与CH4浓度的影响。在每种灌溉制度下再分设覆膜(M)与不覆膜两种农艺措施处理。覆膜滴灌(MD)下按土壤湿润比(P)不同,再设3个处理,分别为P1(P=25%)、P2(P=33%)、P3(P=50%),共6个处理,即DP1、MDP1、MDP2、MDP3、FC(不覆膜漫灌)和MF(覆膜漫灌),裸土(BS)和覆膜裸土(MBS)为对照。研究结果表明:覆膜的增温保湿作用及薄膜对土壤与大气间气体传输的自然阻隔作用使土壤CO2浓度升高10.4%~94.5%,CH4浓度降低5.1%~47.4%。滴灌的干湿交替现象以及漫灌对土壤通气性的降低使漫灌处理土壤中CO2浓度高于滴灌7.4%~49.7%,CH4浓度降低6.6%~68.2%。而土壤湿度通过影响土壤通气性和土壤溶解性有机质两方面来影响土壤温室气体排放,覆膜滴灌下湿润比越高,土壤中CO2浓度越低,其对CH4浓度的影响不确定。土壤温度是土壤呼吸的主要驱动因子,也会影响CH4的氧化过程。观察DP1处理灌水后土壤中温室气体浓度发现,CO2浓度与温度呈显著正相关关系,CH4浓度与温度呈显著负相关关系,土壤中CO2浓度与CH4浓度呈显著负相关关系。     

土壤无机离子对CO2封存泄漏的响应

[目的]旨在研究土壤中无机离子含量对CO2封存泄漏的响应。[方法]在CO2人工气候箱中分别种植绿豆、荞麦两种作物,模拟10 000,20 000,40 000和80 000μl/L这4个浓度梯度,外加一个空白浓度对照组,观测土壤无机离子含量变化及作物生长情况。[结果]随着大气中CO2浓度升高,土壤中的Cl-,K+,Ca2+含量基本先降后升,SO2-4呈现先升后降再升再降的M型变化趋势,Na+,Mg2+,HCO-3变化不显著,而CO2-3始终未检出。绿豆、荞麦的光合速率及生物量均在CO2浓度10 000μl/L时达到最大。[结论]大气中CO2浓度升高一方面会直接影响土壤溶液酸碱度、碳平衡,发生离子沉淀;另一方面还会影响作物和微生物生长,改变其对土壤离子的吸收和代谢。     

华北平原典型农田CO2和N2O排放通量及其与土壤养分动态和施肥的关系

对华北平原小麦-棉花(麦棉)、小麦-大豆(麦豆)、小麦-玉米(麦玉)轮作田的CO2和N2O排放通量进行了测定,分析了温室气体排放通量与土壤中碳、氮元素、气温以及施肥等之间的关系。主要结论:1)麦棉、麦豆、麦玉田的土壤CO2平均排放通量分别为CO2-C 141.7、109.8、128.2 mg.m-2.h-1,其中夏播作物的排放通量高于小麦季;2)麦棉、麦豆及麦玉田作物生长季的土壤N2O平均排放通量分别为N2O-N 98.8、38.9、44.7μg.m-2.h-1,也表现为麦后季作物的排放量高于小麦季;3)同一生育期中不同处理的N2O排放主要与土壤中无机氮含量相关,不同生育期的N2O排放通量主要受不同生育期的土壤温度及水分状况的影响;4)在施肥灌溉后的9 d内土壤N2O排放通量较高,之后逐渐降低,至施肥后22～27 d即与不施肥处理的排放持平。     

干湿交替对新疆绿洲农田土壤CO2排放的影响

[目的]分析不同土壤水分变化及干湿交替对土壤CO_2排放的影响,为绿洲农田土壤碳循环提供科学依据。[方法]选取新疆绿洲棉田土壤,通过室内控制模拟试验,以及用气相色谱仪分析CO_2浓度。[结果](1)与60%WFPS(土壤充水孔隙度)相比,40%WFPS对土壤CO_2排放起到了显著的抑制作用(p0.05),而80%WFPS对土壤CO_2排放无显著性影响(p0.05)。培养结束时,与60%WFPS的土壤CO_2累积排放量相比,40%WFPS的土壤CO_2累积排放量降低26%(p0.05),而80%WFPS的土壤CO_2累积排放量仅增加0.04%(p0.05)。(2)多次干湿交替循环后,干湿交替处理下的土壤CO_2累积排放量显著低于恒湿处理。在不同干旱强度处理中,重度干旱(SD)处理对土壤CO_2排放速率响应程度大于适度干旱(MD)处理,但多次干湿交替循环后,SD处理下的土壤CO_2累积排放量却显著小于MD处理。随干湿交替循环次数的增加,干湿交替对土壤CO_2排放速率的影响显著降低,特别是对土壤CO_2排放速率最高值的影响最大。[结论]在新疆绿洲棉田土壤中,干湿交替能降低土壤CO_2排放量,降低量随干旱强度的增大而增大。     

黄土区退耕草地合理放牧可减少土壤CO2排放和土壤侵蚀

【目的】在退耕草地实施合理放牧,有助于减少土壤CO2排放、 减缓土壤侵蚀。为验证此假设,本研究选择黄土高原渭北旱原坡地,建立退耕草地放牧、 退耕草地不放牧和传统农业耕作三种处理的对比试验小区,定量研究了退耕草地合理放牧相对于退耕草地在减少土壤CO2排放和土壤侵蚀的作用及其影响因素,为探寻在我国西部退耕还草区实施畜牧业生产与环境保护的协调发展模式提供科学依据。【方法】在建立的退耕草地放牧、 退耕草地不放牧和传统农业耕作3种处理的试验小区,利用LI-8100 碳通量自动测量仪原位监测植物生长期(4~8月)和放牧前后土壤CO2排放速率的变化,同时利用时域反射仪(TDR)测定表层0—10 cm土壤含水量,用地温表测定土壤表层2 cm和5 cm的温度。利用环境放射性核素 7Be示踪技术监测较大降雨事件引起的土壤侵蚀速率,同时取样测定侵蚀区土壤有机碳含量,比较不同处理小区侵蚀导致的土壤有机碳流失量。【结果】观测期间,3种处理CO2平均排放速率大小顺序为退耕草地[3.69±0.39 μmol/(m2·s)]退耕草地放牧[3.00±0.44 μmol/(m2·s)]传统农耕地[1.99±0.22 μmol/(m2·s)],坡耕地退耕还草后土壤CO2排放增加了85%,而合理放牧使退耕草地土壤CO2排放量减少了19%。放牧后退耕草地土壤CO2排放速率平均减少了11%,减少值在2% ~ 41%之间。观测期内,退耕草地放牧后土壤侵蚀速率比农耕地和退耕草地分别减少了93% 和77%。坡耕地退耕还草后土壤CO2排放增加主要由于草被植物引起土壤有机碳储量增加和土壤侵蚀强度减小,放牧后退耕草地土壤CO2排放减少主要与动物踩踏引起土壤容重明显增加及草类植被地上部分向土壤中输入的有机碳的减少有关。水分、 温度影响因子无法解释3种处理间土壤CO2排放差异。【结论】合理放牧不仅能显著减少退耕草地土壤CO2排放,而且可以有效控制退耕草地土壤和有机碳侵蚀流失。放牧期间动物的踩踏作用引起草地土壤容重显著增加是退耕草地土壤CO2排放量和土壤侵蚀速率减少的主要原因。本研究结果揭示,在我国黄土高原和类似的退耕还草地区实施合理放牧既可以促进当地畜牧业生产,又能控制土壤侵蚀和减少CO2的排放,是一种值得探究的草地可持续发展管理模式。     

羊草、针茅对高CO2浓度及土壤干旱的响应

通过人工模拟试验分析了CO2浓度升高对羊草、针茅的"施肥效应"。结果表明生物量随CO2浓度的升高而增加;总生物量分别增加40.0%和45.0%。土壤干旱对羊草、针茅的生长及干物质积累为负效应且随干旱程度的增加负效应增强。轻度干旱时总生物量分别减少16%和30%左右,严重干旱下降44%和35%左右。在土壤发生干旱条件下,CO2的"施肥效应"有所减弱,羊草比针茅更为明显。     

Soil CO2 flux in six monospecific forest plantations in Southern Rwanda

Forest soils contain the largest carbon stock of all terrestrial biomes and are probably the most important source of carbon dioxide (CO₂) to atmosphere. Soil CO₂ fluxes from 54 to 72-year-old monospecific stands in Rwanda were quantified from March 2006 to December 2007. The influences of soil temperature, soil water content, soil carbon (C) and nitrogen (N) stocks, soil pH, and stand characteristics on soil CO₂ flux were investigated. The mean annual soil CO₂ flux was highest under Eucalyptus saligna (3.92 μmol m⁻² s⁻¹) and lowest under Entandrophragma excelsum (3.13 μmol m⁻² s⁻¹). The seasonal variation in soil CO₂ flux from all stands followed the same trend and was highest in rainy seasons and lowest in dry seasons. Soil CO₂ flux was mainly correlated to soil water content (R² = 0.36-0.77), stand age (R² = 0.45), soil C stock (R² = 0.33), basal area (R² = 0.21), and soil temperature (R² = 0.06-0.17). The results contribute to the understanding of factors that influence soil CO₂ flux in monocultural plantations grown under the same microclimatic and soil conditions. The results can be used to construct models that predict soil CO₂ emissions in the tropics.     

A new technique to measure soil CO2 efflux at constant CO2 concentration

A new principle for measuring soil CO₂ efflux at constant ambient concentration is introduced. The measuring principle relies on the continuous absorption of CO₂ within the system to achieve a constant CO₂ concentration inside the soil chamber at ambient level, thus balancing the amount of CO₂ entering the soil chamber by diffusion from the soil. We report results that show reliable soil CO₂ efflux measurements with the new system. The novel measuring principle does not disturb the natural gradient of CO₂ within the soil, while allowing for continuous capture of the CO₂ released from the soil. It therefore holds great potential for application in simultaneous measurements of soil CO₂ efflux and its δ¹³C, since both variables show sensitivity to a distortion of the soil CO₂ profile commonly found in conventional chamber techniques.     

Relationship between soil CO2 concentrations and forest-floor CO2 effluxes

To better understand the biotic and abiotic factors that control soil CO₂ efflux, we compared seasonal and diurnal variations in simultaneously measured forest-floor CO₂ effluxes and soil CO₂ concentration profiles in a 54-year-old Douglas fir forest on the east coast of Vancouver Island. We used small solid-state infrared CO₂ sensors for long-term continuous real-time measurement of CO₂ concentrations at different depths, and measured half-hourly soil CO₂ effluxes with an automated non-steady-state chamber. We describe a simple steady-state method to measure CO₂ diffusivity in undisturbed soil cores. The method accounts for the CO₂ production in the soil and uses an analytical solution to the diffusion equation. The diffusivity was related to air-filled porosity by a power law function, which was independent of soil depth. CO₂ concentration at all depths increased with increase in soil temperature, likely due to a rise in CO₂ production, and with increase in soil water content due to decreased diffusivity or increased CO₂ production or both. It also increased with soil depth reaching almost 10 mmol mol⁻¹ at the 50-cm depth. Annually, soil CO₂ efflux was best described by an exponential function of soil temperature at the 5-cm depth, with the reference efflux at 10 °C (F₁₀) of 2.6 μmol m⁻² s⁻¹ and the Q₁₀ of 3.7. No evidence of displacement of CO₂-rich soil air with rain was observed.Effluxes calculated from soil CO₂ concentration gradients near the surface closely agreed with the measured effluxes. Calculations indicated that more than 75% of the soil CO₂ efflux originated in the top 20 cm soil. Calculated CO₂ production varied with soil temperature, soil water content and season, and when scaled to 10 °C also showed some diurnal variation. Soil CO₂ efflux and concentrations as well as soil temperature at the 5-cm depth varied in phase. Changes in CO₂ storage in the 0–50 cm soil layer were an order of magnitude smaller than measured effluxes. Soil CO₂ efflux was proportional to CO₂ concentration at the 50-cm depth with the slope determined by soil water content, which was consistent with a simple steady-state analytical model of diffusive transport of CO₂ in the soil. The latter proved successful in calculating effluxes during 2004.     

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。     

不同管理措施对滨海盐渍农田土壤CO2排放及碳平衡的影响

为探讨不同管理措施对滨海盐渍农田碳平衡的影响,本文通过玉米–小麦轮作试验,研究农田土壤的CO_2释放规律,及其农田碳收支状况。试验设计6个处理:1常规对照(CK);2有机肥常量(OF);3氮肥增施(NF);4秸秆还田(S);5有机肥加秸秆(OF+S);6免耕(NT)。研究表明,秸秆还田和有机肥的施用增加了土壤呼吸的强度,而免耕处理的CO_2平均释放量最低,不同处理下土壤呼吸总体表现为OF+SSOMNFCKNT。各处理土壤有机碳含量随着作物的收获逐渐升高,其中OF与NT增加最多,而增施氮肥处理并没有显著提高土壤的有机碳水平。各处理间的有机碳含量没有显著性差异。在两季作物种植结束后,各处理的碳输入均高于碳输出,均为碳净输入,表现出较强的碳汇特征。秸秆还田和单施有机肥的碳净输入均显著高于对照,可有效减缓因农田土壤CO_2排放而造成的全球气候变化问题。     

Soil CO2 efflux vs. soil respiration: Implications for flux models

In the long term, all CO₂ produced in the soil must be emitted by the surface and soil CO₂ efflux (FCO₂) must correspond to soil respiration (R_soil). In the short term, however, the efflux can deviate from the instantaneous soil respiration, if the amount of CO₂ stored in the soil pore-space (SCO₂) is changing. We measured FCO₂ continuously for one year using an automated chamber system. Simultaneously, vertical soil profiles of CO₂ concentration, moisture, and temperature were measured in order to assess the changes in the amount of CO₂ stored in the soil. R_soil was calculated as the sum of the rate of change of the CO₂ storage over time and FCO₂. The experiment was split into a warm and a cold season. The dependency of soil respiration and soil efflux on soil temperature and on soil moisture was analyzed separately. Only the moisture-driven model of the warm season was significantly different for FCO₂ and R_soil. At our site, a moisture-driven soil-respiration model derived from CO₂ efflux data would underestimate the importance of soil moisture. This effect can be attributed to a temporary storage of CO₂ in the soil pore-space after rainfalls where up to 40% of the respired CO₂ were stored.     

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。     

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