CO2浓度升高对三江平原湿地活性有机碳及土壤微生物的影响

利用开顶箱薰气室,设置正常大气CO2浓度(Ambient CO2,350 umol·mol-1)和高CO2浓度(Elevated CO2,700μmol·mol-1)2个水平和不施氮(NN,0 gN·m-2)、常氮(MN,5 gN·m-2)、高氮(HN,15 gN·m-2)3个氮素水平,研究CO2浓度升高和氮肥施用对三江平原草甸小叶章湿地(Calamagrostis angustifolia)土壤活性有机碳及微生物的影响。结果表明,CO2浓度升高条件下,土壤微生物量碳(MBC)和溶解性有机碳(DOC)呈增加趋势,易氧化有机碳(LOC)和水溶性碳水化合物碳(CHC)的变化因生长期和氮素水平而异。CO2浓度升高,小叶章湿地土壤微生物数量在不同的生长时期呈现不同的响应趋势。细菌数量在腊熟期增幅最大,为31.4%;真菌数量在腊熟期增加16.6%,成熟期增加24.3%;放线菌数量没有发生明显变化。相关分析表明,细菌、真菌和放线菌数量都与土壤微生物量碳呈显著相关。湿地土壤中的活性有机碳可以为土壤微生物提供更多的有效能量,从而加快湿地生态系统养分循环过程。     

巴丹吉林最高沙山区CO2浓度与昼夜变化规律

为查明沙漠区CO₂浓度和对大气CO₂的影响以及在全球碳循环中的作用,利用红外CO₂监测仪,在2009年5月对全球最高大的巴丹吉林诺尔图东大沙山等进行了17个钻孔CO₂浓度的昼夜观测。结果表明,巴丹吉林大沙山不同观测点CO₂浓度差异较大,各观测点CO₂浓度变化在0.01%~0.075％之间;夜间沙层CO₂浓度低,白天CO₂浓度高;CO₂浓度昼夜变化明显,从早7时到次日7时1~5m各深度CO₂浓度均呈现由低到高再到低的变化规律;在24h内,沙层CO₂浓度变化存在4个转折点,分别出现在凌晨5时、11时、18时和21时左右。在沙层水分一定的条件下,昼夜温度变化是造成沙层CO₂浓度昼夜规律变化的主要原因,两者呈正相关关系;含水量较高的沙层CO₂浓度明显高于含水量较低的沙层;5m深度以上沙层CO₂浓度均高于地表空气CO₂浓度,表明极端干旱的高大沙山区是CO₂的来源区,也指示环境恶劣的裸露高大沙山区微生物活动产生的沙层CO₂浓度仍然超过了大气CO₂浓度。     

黄河下游沿岸地市CO2排放的时空分异

地市级尺度的碳排放结构演变与区域差异分析对通过技术学习与知识流动短期内抑制 碳排放的快速增长具有重要意义。以地市级行政区作为基本空间单元, 对黄河下游沿岸区、 两大子区及21地市化石能源与水泥工业生产过程排放的CO₂ 进行科学核算, 发现CO₂ 排放量 变化于2000年的364.12～4426.95万t至2009年的1238.98～10411.91万t,呈现出典型的 “S型”增长特征, 但不同尺度区域排放结构的时空差异显着。2006年以来, 工业化进程较快 的区域水泥排碳比例有显着增长, 产业结构优化策略促使少数地市水泥排碳比例有所下降。 CO₂ 排放强度与人均排放量的变动符合碳排放EKC曲线关系, 但时空分异特征并不一致。排 放强度的全区总体差异较为合理, 而人均排放量的区域差异偏大, 从而为涓滴效应的加速作 用创造了空间。地区内差异分别为两指标全区总体差异变动的主导因素, 整体上, 中原区内 地市间差异对两指标全区差异变动的贡献更大。     

散射辐射对西藏高原高寒草甸净生态系统CO2交换的影响

2003~2006年在当雄草原站用涡度相关法对西藏高原广泛分布的高寒草甸生态系统的碳通量和常规气象数据进行了连续观测。基于这些数据,根据净生态系统CO₂交换量(NEE)对晴朗指数(k)和土壤温度的响应特征,分析了净生态系统CO₂交换量与散射辐射之间的关系。依据地面接受的散射辐射量把天气划分为云隙天、晴天和多云天。结果表明,散射辐射不能提高西藏高原高寒草甸生态系统的碳吸收水平。该生态系统的碳收支过程主要受光合有效辐射控制,碳排放过程主要受土壤温度控制;且NEE随k的变化趋势受散射辐射的影响较小,生态系统碳收支更多地受太阳辐射对土壤强烈加温的影响。三种散射辐射天气条件下,NEE随k的变化趋势基本一致,先增加后减小;NEE达最大值时的土壤温度皆为15℃左右,k值皆为0.7~0.8。     

作物水分利用效率对温度和CO2浓度升高的响应研究进展

以大气CO2浓度和温度升高为主要标志的全球气候变化对作物水分利用效率产生重要影响,作物水分利用效率对CO2浓度和温度升高的响应特征与机理研究,对揭示气候变化对作物生长的影响及其机制具有重要作用和意义。本文分别介绍了作物水分利用效率对CO2浓度和温度升高的响应研究进展,CO2浓度和温度升高对作物水分利用效率的协同效应,以及CO2浓度与温度升高对作物水分利用效率影响的实验研究方法,并提出了作物水分利用效率对CO2浓度和温度升高响应研究仍需要解决的几个关键问题:①多因子协同效应;②不同品种的响应差异;③不同尺度水平的响应过程;④作物水分利用效率对气候变化的适应性。     

大气CO_2浓度升高对土壤中不同粒级碳的影响

不同粒级土壤中的碳有着不同的周转规律,在高CO2浓度条件下,它们含量的变化将在一定程度上反映土壤碳是累积还是减少,对明确土壤碳的变化趋势有重要意义.采用田间培养试验初步模拟研究在高CO2浓度条件下土壤不同粒级碳的分布.结果表明,加入秸秆培养1年,由于CO2浓度升高的原因导致在低氮(LN)、常规氮(NN)和高氮(HN)水平下土壤中碳分别增加0·01、1·10、1·22g/kg,表现为粒级<53μm土壤颗粒中碳分别增加1·53、2·19、2·70g/kg.粒级<53μm土壤颗粒碳量的增加,主要是由于其重量分配百分数显著增加36·2%,碳浓度增加5·4%;粒级>250μm和250~53μm土壤颗粒部分虽然其碳浓度分别增加20·8%和17·3%(P<0·05),但由于重量分配百分数分别显著降低22·8%和36·1%,结果碳量降低.试验表明高CO2浓度导致不同粒级土壤的分配及碳浓度的变化;高氮施肥水平下有增加土壤碳量特别是小粒级土壤碳量的趋势.     

大气CO2浓度升高对土壤中不同粒级碳的影响

不同粒级土壤中的碳有着不同的周转规律,在高CO2浓度条件下,它们含量的变化将在一定程度上反映土壤碳是累积还是减少,对明确土壤碳的变化趋势有重要意义.采用田间培养试验初步模拟研究在高CO2浓度条件下土壤不同粒级碳的分布.结果表明,加入秸秆培养1年,由于CO2浓度升高的原因导致在低氮(LN)、常规氮(NN)和高氮(HN)水平下土壤中碳分别增加0.01、1.10、1.22g/kg,表现为粒级＜53 μm土壤颗粒中碳分别增加1.53、2.19、2.70 g/kg.粒级＜53 μm土壤颗粒碳量的增加,主要是由于其重量分配百分数显著增加36.2%,碳浓度增加5.4%;粒级＞250μm和250～53μm土壤颗粒部分虽然其碳浓度分别增加20.8%和17.3%(P＜0.05),但由于重量分配百分数分别显著降低22.8%和36.1%,结果碳量降低.试验表明高CO2浓度导致不同粒级土壤的分配及碳浓度的变化;高氮施肥水平下有增加土壤碳量特别是小粒级土壤碳量的趋势.     

温度升高和CO2浓度增加对冬小麦生物量的影响和不确定性分析（英文）

Impacts of climatic change on agriculture and adaptation are of key concern of scientific research. However, vast uncertainties exist among global climates model output, emission scenarios, scale transformation and crop model parameterization. In order to reduce these uncertainties, we integrate output results of four IPCC emission scenarios of A1FI, A2, B1 and B2, and five global climatic patterns of HadCM3, PCM, CGCM2, CSIRO2 and ECHAM4 in this study. Based on 20 databases of future climatic change scenarios from the Climatic Research Unit (CRU) , the scenario data of the climatic daily median values are generated on research sites with the global mean temperature increase of 1 ℃(GMT+1D), 2 ℃ (GMT+2D) and 3 ℃(GMT+3D). The impact of CO2 fertilization effect on wheat biomass for GMT+1D, GMT+2D and GMT+3D in China’s wheat-producing areas is studied in the process model, CERES-Wheat and probabilistic forecasting method. The research results show the CO2 fertilization effect can compensate reduction of wheat biomass with warming temperature in a strong compensating effect. Under the CO2 fertilization effect, the rain-fed and irrigated wheat biomasses increase respectively, and the increment of biomass goes up with temperature rising. The rain-fed wheat biomass increase is greater than the irrigated wheat biomass. Without consideration of CO2 fertilization effect, both irrigated and rain-fed wheat biomasses reduce, and there is a higher probability for the irrigated wheat biomass than that of the rain-fed wheat biomass.     

不同植被类型覆盖下土壤CO2浓度对洞穴景观的影响

土壤中的CO2 通过影响土壤水对碳酸盐岩的溶蚀能力控制洞穴滴水中的Ca2 +初始含量 ,同时它进入洞穴水体后溶解度的变化也会影响洞穴景观的形成。研究表明 ,不同植被类型对土壤CO2 浓度会产生不同影响。本文通过模拟分析认为 ,在一定范围内 ,地表生态系统的改善有利于土壤中CO2 的增加和洞穴中碳酸钙沉积景观的发育 ,但是若超过一定的阈值 ,即土壤中的CO2 浓度过高 ,使喀斯特水中的CO2 不能在洞穴顶部碳酸盐岩体渗流过程中完全被消耗时 ,洞穴滴水的酸性会对碳酸钙产生溶蚀作用 ,易形成洞穴溶蚀景观。     

Influence of environmental, root, and stand parameters on soil surface CO2 efflux in a Populus euphratica of desert forest in extreme arid region

Spatial variation in soil surface CO2 efflux was measured in a stand of Populus euphratica in the Ejina Oasis of desert riparian forest in the extreme arid region in northwestern China from April 2007 through October 2007.Measurements were taken with a gas-exchange analyzer linked to a soil-respiration chamber.The mean soil CO2 efflux in the stand was 2.71 μmol/(m2·s) during the growing season and 1.38 μmol/(m2·s) in the nongrowing season.The seasonal maximum (end of May through early June) andminimum (October) CO2 efflux were 3.38 and 0.69 μmol/(m2·s),respectively.The diurnal fluctuation of CO2 efflux was relatively small (< 20 percent),with theminimum appearing around 05:00 and the maximum around 15:00.Linear regression analysis showed soil-surface CO2 efflux to be most highly correlated with soil temperature (R2=0.435) and soil moisture (R2=0.213).When all variables were considered simultaneously,only soil temperature (R2=0.378),soil moisture (R2=0.147),and root volume density (R2=0.021) explained a significant amount of variance in soil surface CO2 efflux.Stand volumes were not correlated with soil CO2 efflux on our sites.     

干旱沙区典型人工植被群落下土壤剖面CO_2浓度变化特征及其驱动因子

对人工固沙植被区柠条(Caragana korshinskii)群落和油蒿(Caragana korshinskii)群落下不同深度的土壤气体采样,主要研究和讨论了不同类型人工植被区下土壤CO2浓度的变化特征及土壤温度和土壤水分对其的影响。结果表明:柠条和油蒿群落0~80cm处的土壤空气CO2浓度随着土壤深度的增加而增加,并且在0~40cm,油蒿群落下的土壤CO2浓度值大于柠条,而在40cm以下则相反。其平均值分别为1 229.3μmol·mol-1和1 242.7μmol·mol-1,大于同一深度流沙下土壤CO2浓度值978.9μmol·mol-1。土壤水分与二者的土壤CO2浓度变化趋势在年际尺度上具有一致性,浅层40cm内油蒿群落下的土壤CO2浓度和土壤水分含量的相关性明显大于柠条和流沙。而在40cm以下,则表现为柠条油蒿流沙。土壤温度对土壤CO2浓度的影响程度一般为流沙油蒿柠条,特别是流沙,在表层达到了极显著的水平,之后随着土壤深度的增加而降低。而土壤温度对油蒿和柠条样地土壤CO2浓度的影响较为复杂,呈现出先增加后减小的趋势。在年际尺度上,土壤水分含量是不同植被群落下土壤剖面CO2浓度的关键限制因子,而在日尺度上,土壤温度则为主要限制因子。据粗略估计,在0~80cm内,柠条和油蒿根系呼吸所占的比例约为30.7%和33.3%。     

Effect of nitrogen amendments on microbial biomass, above-ground biomass and nematode population in the Negev Desert soil

Nitrogen amendments (0, 25, 50 and 100 kg NH₄NO₃/ha) were used to study the responses of primary production, microbial biomass and nematode population in desert soil. The study was conducted in the Israeli Negev Desert, a region characterized by low and randomly distributed rainfall. Over a 1-year study period, nitrogen amendments resulted in a significant (p<0·01) increase in soil microbial biomass. Soil microbial biomass also increased concomitantly with the increase in soil organic matter. The number of free-living nematodes in the soil increased with the increase in soil moisture, ranging from 43,000 individuals per square metre at the end of the summer to 351,000 individuals per square metre during the rainy season. No significant correlation was found between the nitrogen treatments and the nematode population, whereas a significant positive correlation was found between the nitrogen amendments and the above-ground biomass (r²=0·94, p<0·03). The nitrate proportion of the total soluble nitrogen in the soil also increased with the increase in soil moisture. This study provides baseline data for nitrogen amendments on soil microbial status, as well as insights into the importance of nitrogen in fertility in arid environments.     

CO2 seasonal variation and global change: Test global warming from another point of view

CO₂ and temperature records at Mauna Loa, Hawaii, and other observation stations show that the correlation between CO₂ and temperature is not significant. These stations are located away from big cities, and in various latitudes and hemispheres. But the correlation is significant in global mean data. Over the last five decades, CO₂ has grown at an accelerating rate with no corresponding rise in temperature in the stations. This discrepancy indicates that CO₂ probably is not the driving force of temperature change globally but only locally (mainly in big cities). We suggest that the Earth''s atmospheric concentration of CO₂ is too low to drive global temperature change. Our empirical perception of the global warming record is due to the urban heat island effect:temperature rises in areas with rising population density and rising industrial activity. This effect mainly occurs in the areas with high population and intense human activities, and is not representative of global warming. Regions far from cities, such as the Mauna Loa highland, show no evident warming trend. The global monthly mean temperature calculated by record data, widely used by academic researchers, shows R²=0.765, a high degree of correlation with CO₂. However, the R² shows much less significance (mean R²=0.024) if calculated by each record for 188 selected stations over the world. This test suggests that the inflated high correlation between CO₂ and temperature (mean R²=0.765-0.024=0.741) used in reports from the Intergovernmental Panel on Climate Change (IPCC) was very likely produced during data correction and processing. This untrue global monthly mean temperature has created a picture:human emission drives global warming.     

Chemical weathering and CO2 consumption in the Xijiang River basin, South China

Monthly samples of riverine water were collected and analyzed for the concentrations of major ions (Ca²⁺, Mg²⁺, K⁺, Na⁺, HCO₃⁻, SO₄²⁻, Cl⁻, NO₃⁻), dissolved silicon, and total dissolved solids (TDS) at Wuzhou hydrological station located between the middle and lower reaches of the Xijiang River (XJR) from March 2005 to April 2006. More frequent sampling and analysis were carried out during the catastrophic flooding in June 2005. Stoichiometric analysis was applied for tracing sources of major ions and estimating CO₂ consumption from the chemical weathering of rocks. The results demonstrate that the chemical weathering of carbonate and silicate rocks within the drainage basin is the main source of the dissolved chemical substances in the XJR. Some 81.20% of the riverine cations originated from the chemical weathering processes induced by carbonic acid, 11.32% by sulfuric acid, and the other 7.48% from the dissolution of gypsum and precipitates of sea salts within the drainage basin. The CO₂ flux consumed by the rock chemical weathering within the XJR basin is 2.37 × 10¹¹ mol y^− 1, of which 0.64 × 10¹¹ mol y^− 1 results from silicate rock chemical weathering, and 1.73 × 10¹¹ mol y^− 1 results from carbonate rock chemical weathering. The CO₂ consumption comprises 0.38 × 10¹¹ mol during the 9-d catastrophic flooding. The CO₂ consumption from rock chemical weathering in humid subtropical zones regulates atmospheric CO₂ level and constitutes a significant part of the global carbon budget. The carbon sink potential of rock chemical weathering processes in the humid subtropical zones deserves extra attention.     

Photosynthetic responses of Larrea tridentata to a step-increase in atmospheric CO2at the Nevada Desert FACE Facility

Of all terrestrial ecosystems, the productivity of deserts has been suggested to be the most responsive to increasing atmospheric CO₂. The extent to which this prediction holds will depend in part on plant responses to elevated CO₂under the highly variable conditions characteristic of arid regions. The photosynthetic responses ofLarrea tridentata , an evergreen shrub, to a step-increase in atmospheric CO₂(to 550 μmolmol⁻¹) were examined in the field using Free-Air CO₂Enrichment (FACE) under seasonally varying moisture conditions. Elevated CO₂substantially increased net assimilation rate (A_net) in Larrea during both moist and dry periods of the potential growing season, while stomatal conductance (g_s) did not differ between elevated and ambient CO₂treatments. Seasonal and diurnal gas exchange dynamics in elevated CO₂mirrored patterns in ambient CO₂, indicating that elevated CO₂did not extend photosynthetic activity longer into the dry season or during more stressful times of the day. Net assimilation vs. internal CO₂(A/C_i) responses showed no evidence of photosynthetic down-regulation during the dry season. In contrast, after significant autumn rains, A_max(the CO₂saturated rate of photosynthesis) and CE (carboxylation efficiency) were lower in Larrea under elevated CO₂. In situ chlorophyll fluorescence estimation ofLarrea Photosystem II efficiency (F_v/F_m) responded more to water limitation than to elevated CO₂. These findings suggest that predictions regarding desert plant responses to elevated CO₂should account for seasonal patterns of photosynthetic regulatory responses, which may vary across species and plant functional types.     

A large daylight geodesic dome for quantification of whole-ecosystem CO2 and water vapour fluxes in arid shrublands

We designed, constructed, calibrated and field-tested a lightweight (30 kg), 4.2 m diameter, 16.4 m³ polyethylene-covered dome static chamber ecosystem gas exchange cuvette that can quantify ecosystem CO₂ and water vapour fluxes as low as 0.1 μmol CO₂ m⁻² s⁻¹ and 0.1 mmol H₂O m⁻² s⁻¹ with little impact on environmental conditions. Fluxes measured in May 2001 in an intact Great Basin sagebrush ecosystem at midday were significantly higher than in an adjacent post-wildfire successional ecosystem, with observed ranges from –0.71 to 1.49 μmol CO₂ m⁻² s⁻¹ for CO₂ and from –0.09 to 0.53 mmol H₂O m⁻² s⁻¹ for water vapour.     

Effects of freeze–thaw cycles on soil N_2O concentration and flux in the permafrost regions of the Qinghai–Tibetan Plateau

Nitrous oxide(N_2 O) is one of the most important greenhouse gases in the atmosphere; freeze–thaw cycles(FTCs) might strongly influence the emission of soil N_2 O on the Qinghai–Tibetan Plateau(QTP). However, there is a lack of in situ research on the characteristics of soil N_2 O concentration and flux in response to variations in soil properties caused by FTCs.Here, we report the effect of FTC-induced changes in soil properties on the soil N_2 O concentration and flux in the permafrost region of the higher reaches of the Shule River Basin on the northeastern margin of the QTP. We measured chemical properties of the topsoil, activities of soil microorganisms, and air temperature(AT), as well as soil N_2 O concentration and flux, over an annual cycle from July 31, 2011, to July 30, 2012. The results showed that soil N_2 O concentration was significantly affected by soil temperature(ST), soil moisture(SM), soil salinity(SS), soil polyphenol oxidase(SPO), soil alkaline phosphatase(SAP), and soil culturable actinomycetes(SCA), ranked as SMSSSTSPOSAPSCA, whereas ST significantly increased soil N_2 O flux, compared with SS. Overall, our study indicated that the soil N_2 O concentration and flux in permafrost zone FTCs were strongly affected by soil properties, especially soil moisture, soil salinity, and soil temperature.     

四川盆地中三叠统雷口坡组雷三、雷四段盐岩沉积环境与成因研究

四川盆地雷口坡组大量钻井资料揭示中三叠统雷口坡组主要成盐期分别为雷三2期和雷四2期。岩性组合特征、沉积环境研究表明,在川中的平昌—南充—遂宁一带发育雷三2期浓缩盐膏质蒸发泻湖微相,在川中-川西地区的南部—盐亭—成都—邛崃地区发育雷四2期盐膏湖盆微相。两期盐岩差异主要表现是,雷三2期时,盆地处于频繁的海进、海退过程中,沉积环境变化较快,成盐环境相对开放,盐盆往往多次蒸发浓缩、补给、淡化,海水表现出接近或者达到盐岩沉积浓度,其间往往夹杂石膏和云质团块沉积。雷四2期时,四川盆地处于持续的海退蒸发期,蒸发量远远大于补给量,海水以蒸发浓缩为主,海水表现为超过石盐沉积浓度,沉积石盐中夹杂卤石,局部地区钾含量极高。     

不同形貌纳米二氧化锰对三价砷吸附性能及机理研究

以高锰酸钾和一水硫酸锰为原料,采用水热合成法,合成得到了花状和海胆状纳米二氧化锰吸附剂。研究了两种吸附剂对三价砷的吸附选择性、循环利用性及除砷机理。结果表明,阴离子对花状和海胆状吸附剂吸附三价砷的影响顺序略有不同,其分别为PO■ CO■HCO~-_3NO~-_3SO■Cl~-,PO■HCO■SO■CO■NO~-_3Cl~-;花状和海胆状二氧化锰经三次循环再生后的除砷率分别为65.5%和75.1%;两种吸附剂对三价砷的吸附机理主要为氧化吸附作用。