中国南京与美国德克萨斯稻田甲烷排放的比较(英文)

稻田甲烷排放试验分别在南京与德克萨斯水稻生长季实施，观测期内测定甲烷排放通量、上壤温度和水稻生物量。结果表明：南京稻田土镶温度的季节性变幅为１５．３℃，甲烷排放通量与土壤温度成非线性正相关而与水稻生物量无关；德克萨斯稻田土壤温度的季节性变幅为的２．９℃，甲烷排放通量与土壤温度无关而与水稻生物量成线性正相关。由此得出结论：在持续淹水和无外源有机碳施加的条件下，土壤温度变幅大的地区驱动稻田甲烷排放季节性变化的关键因子为土壤温度，土壤温度变幅小的地区其关键驱动因子则为水稻的生长量。     

农田土壤固碳潜力研究的关键科学问题

农田生态系统在陆地生态系统碳循环中扮演着重要的角色。增加农田土壤有机碳的固定不仅可减少大气CO2含量,而且对保障国家粮食安全具有举足轻重的作用。近年来评估土壤固碳潜力已成为国际科学界研究的热点和难点。但由于不同研究者对“潜力”范畴的界定不同,全球或区域尺度农田土壤固碳潜力的估算还存在很大的不确定性。所谓固碳潜力,即土壤碳的饱和水平或土壤所容纳碳的最大能力。这一能力受区域气候、土壤类型、农业管理措施的综合影响。故此,合理地评价固碳潜力,应综合考虑气候、土壤和农业措施诸因素,并将宏观尺度与微观尺度的研究结合起来。从固碳潜力概念范畴及研究方法出发,阐述了农田土壤固碳潜力的研究现状,并结合生物潜力和物理化学潜力的研究,提出区域农田土壤固碳潜力的计量方案,并就该研究领域亟需回答的科学问题进行了探讨。     

Simulating Crop Net Primary Production in China from 2000 to 2050 by Linking the Crop-C model with a FGOALS＇s Model Climate Change Scenario

Net primary production （NPP） of crop represents the capacity of sequestrating atmospheric CO2 in agro-ecosystem, and it plays an important role in terrestrial carbon cycling. By linking the Crop-C model with climate change scenario projected by a coupled GCM FGOALS via geographical information system （GIS） techniques, crop NPP in China was simulated from 2000 to 2050. The national averaged surface air temperature from FGOALS is projected to increase by 1.0℃ over this period and the corresponding atmospheric CO2 concentration is 535 ppm by 2050 under the IPCC A1B scenario. With a spatial resolution of 10 ×10 km^2, model simulation indicated that an annual average increase of 0.6 Tg C yr^-1 （Tg=10^12 g） would be possible under the A1B scenario. The NPP in the late 2040s would increase by 5% （30 Tg C） within the 98×10^6 hm^2 cropland area in contrast with that in the early 2000s. A further investigation suggested that changes in the NPP would not be evenly distributed in China. A higher increase would occur in a majority of regions located in eastern and northwestern China, while a slight reduction would appear in Hebei and Tianjin in northern China. The spatial characteristics of the crop NPP change are attributed primarily to the uneven distribution of temperature change.     

中国小麦和玉米农田N2O减排措施及潜力

旱作农田是N₂O的主要排放源,削减其N₂O排放有助于整体降低农田温室气体排放。运用整合分析(Meta-analysis)的方法,研究了不同农业管理措施对中国小麦和玉米农田N₂O排放的影响,并估算了各减排措施的减排潜力。结果表明：添加抑制剂可显著减少小麦和玉米农田N₂O排放36%~46%,并增加作物产量;施氮量减少30%以内,可削减N₂O排放10%~18%,且对产量无明显影响;施用缓(控)释肥和秸秆还田能显著减少小麦田N₂O排放,但对玉米田的减排效果并不显著。在不同的减排措施下,中国小麦和玉米农田N₂O减排潜力分别为9.29~13.90 Gg N₂O-N/生长季和10.53~23.19 Gg N₂O-N/生长季。河南、山东、河北和安徽省小麦田减排潜力最大,占全国小麦田N₂O减排潜力的53%;黑龙江、吉林、山东、河北和河南省玉米田减排潜力最大,约占全国玉米田N₂O减排潜力的50%。     

中国草地碳收支研究与展望

如何提高生物圈固定大气CO2的能力是减缓气候变化的重要主题.中国草地面积约400×106hm2,占世界草地面积的12.5%,在吸收和固定大气CO2中具有重要作用.文章就气候变化和人类活动对草地碳收支的影响以及区域和国家尺度草地碳收支变化的研究进展进行了评述,提出未来中国草地碳收支研究应重点关注3个方面: 气候变化和人为干预对草地碳收支影响的驱动机制; 中国草地碳收支变化的时空特征与固碳潜力; 草地生态系统碳收支模型的开发.     

Methane and nitrous oxide emissions from three paddy rice based cultivation systems in Southwest China

To understand methane (CH4) and nitrous oxide (N2O) emissions from permanently flooded rice paddy fields and to develop mitigation options, a field experiment was conducted in situ for two years (from late 2002 to early 2005) in three rice-based cultivation systems, which are a permanently flooded rice field cultivated with a single time and followed by a non-rice season (PF), a rice-wheat rotation system (RW) and a rice-rapeseed rotation system (RR) in a hilly area in Southwest China. The results showed that the total CH4 emissions from PF were 646.3±52.1 and 215.0±45.4 kg CH4 hm-2 during the rice-growing period and non-rice period, respectively. Both values were much lower than many previous reports from similar regions in Southwest China. The CH4 emissions in the rice-growing season were more intensive in PF, as compared to RW and RR. Only 33% of the total annual CH4 emission in PF occurred in the non-rice season, though the duration of this season is two times longer than the rice season. The annual mean N2O flux in PF was 4.5±0.6 kg N2O hm-2 yr-1. The N2O emission in the rice-growing season was also more intensive than in the non-rice season, with only 16% of the total annual emission occurring in the non-rice season. The amounts of N2O emission in PF were ignorable compared to the CH4 emission in terms of the global warming potential (GWP). Changing PF to RW or RR not only eliminated CH4 emissions in the non-rice season, but also substantially reduced the CH4 emission during the following rice-growing period (ca. 58%, P<0.05). However, this change in cultivation system substantially increased N2O emissions, especially in the non-rice season, by a factor of 3.7 to 4.5. On the 100-year horizon, the integrated GWP of total annual CH4 and N2O emissions satisfies PF>>RR≈RW. The GWP of PF is higher than that of RW and RR by a factor of 2.6 and 2.7, respectively. Of the total GWP of CH4 and N2O emissions, CH4 emission contributed to 93%, 65% and 59% in PF, RW and RR, respectively. These results suggest that changing PF to RW and RR can substantially reduce not only CH4 emission but also the total GWP of the CH4 and N2O emissions.     

三江平原典型沼泽湿地蒸散量研究

利用涡度相关技术对三江平原典型沼泽湿地蒸散量及其影响因子进行研究,结果表明沼泽湿地蒸散量时间变化特征明显。日出后蒸散量逐渐增加,12:00～13:00(北京时间)达到最大值,6～10月各月平均值分别为285.5、257.4、243.0、167.1和65.9W.m-2,各月总蒸散量分别为120.9、101.6、93.1、59.3和25.9mm。与同期降雨量相比,6～9月沼泽湿地水量发生亏缺,亏缺量分别为72.7、3.2、58.8和44.4mm。沼泽湿地蒸散量受环境因子影响强烈。蒸散量与净辐射呈显著线性正相关。蒸散量也随饱和水汽压差的增加而增加,但植物发育成熟后,当饱和水汽压差大于某一阈值(11hPa)时,饱和水汽压差的增加反而抑制了水分蒸散。另外,白天风速增加在一定程度上能够促进水分蒸散。     

大气CO2浓度升高和秸秆还田对稻麦轮作农田N2O排放的影响

随着大气CO2浓度的逐渐升高,CO2的施肥效应很可能对陆地生态系统的N2O地气交换过程产生一定的影响。在江苏北部的中国稻麦轮作FACE (Free-Air Carbon Dioxide Enrichment) 实验平台上,采用静态箱暗箱-色谱法,研究了一个稻麦轮作周期（2005年6月中旬至2006年6月中旬）3种小麦秸秆还田水平处理(全还田、半还田和不还田)和CO2浓度升高200 μmol·mol-1对稻麦轮作农田N2O排放的影响。结果表明,就当地传统农田管理方式下的砂性土壤稻麦轮作农田N2O排放而言,所采用的观测方法未能检测到显著的秸秆还田效应和大气CO2浓度升高效应。     

中国东北三省1960—2005年地表干燥度变化趋势

为研究气候变化对东北三省地表干湿状况的影响,利用该区1960—2005年72个气象站的观测资料,采用Penman Monteith模型计算了各站的潜在蒸散量,由潜在蒸散量和降水量之比构建干燥度指数,并采用Kriging法进行空间插值以分析其区域特征。结果表明,该区地表干湿状况具有明显的时空变化特征。1960—1979年间,由于降水减少和潜在蒸散增加,地表干燥度指数呈增加趋势,水汽压差增大是潜在蒸散增加的主要原因;1980—2005年间,大部分地区地表干旱状况有所减缓,其中以黑龙江省和吉林东部尤为明显。降水增加和潜在蒸散减少是地表干旱状况趋缓的主要原因,风速降低和净辐射减小导致潜在蒸散减少。总体而言,气候变化并未加剧东北三省的干旱化。     

温带森林土壤溶液溶解性N2O和CO2含量特征及其影响机制

利用陶瓷头土壤溶液收集器采集2006年7月～2007年8月问长白山阔叶红松天然林不同深度(15cm和60 cm)土壤溶液,探讨应用气液萃取平衡-气相色谱法测定森林土壤溶液中溶解性气体N_2O和CO_2浓度的可行性,并利用此方法研究林地不同深度土壤溶液中两种气体含量特征及其影响机理.研究结果显示观测期内林地15 cm和60 cm深度土壤溶液中溶解性CO_2浓度的变化范围分别为5.26～10.71μg·mL~(-1)(C)和3.13～6.16 μg·mL~(-1)(C),溶解性N_2O浓度的变化范围分别为2.44～13.40 ng·mL~(-1)(N)和3.23～27.98 ng·mL~(-1)(N).阔叶红松天然林土壤溶液中溶解性CO_2和N_2O浓度均呈现出明显的季节性变化.春融后的降水促进了土壤溶液中溶解性N_2O产生,尤其在60 cm深度.与60 cm深度相比,林地15 cm深度溶液中溶解性CO_2浓度的季节性变化更明显,尤其在植物生长旺季.逐步回归分析显示,水溶性有机碳含量可以解释林地不同深度溶液中溶解性CO_2浓度变化的29%;水溶性有机氮含量可以解释林地60 cm深度溶解性N_2O浓度变化的34%.因此,水溶性有机碳和有机氮分别是长白山阔叶红松林土壤溶液溶解性CO_2和N_2O形成的重要因子.同时研究结果表明本文实验方法对于测定林地不同深度土壤溶液中溶解性N_2O和CO_2含量均有较好的适用性,连续三次萃取后所获得的气体浓度可有效反映溶液中的实际气体浓度.