共查询到13条相似文献，搜索用时 68 毫秒
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乌江流域近年来建成一系列梯级水电站,本文以乌江(有坝)、赤水河(无坝)为例,基于Modis-NDVI时间序列数据,采用Sen趋势分析、Hurst指数等方法,研究筑坝对植被覆盖过去变化趋势以及未来变化的可持续性影响,及其影响的尺度范围。结果显示：乌江、赤水河流域NDVI均呈波动上升趋势,主要变化类型均为显著增加;在空间尺度上,乌江流域梯级水库密集建设的中下游地区植被覆盖当前变化为减少趋势。乌江流域与赤水河流域植被覆盖未来变化趋势存在差异,乌江流域平均Hurst指数 < 0.5,植被覆盖变化反向持续性较强,反持续类型区域主要分布于流域中下游;赤水河流域Hurst指数 > 0.5,植被覆盖变化正向持续性较强。筑坝活动对河流周边过去的植被覆盖造成了影响,且对未来植被覆盖变化的影响具有持续性。 相似文献
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河流物理生境是维持河流生物多样性及生态功能的关键因素。生境质量的好坏能反应河流健康的程度。以我国西南地区的五布河和藻渡河为例,采用河流生境调查方法(RHS)和树状水系连通性指数(DCI)定量评估水电梯级开发和水坝建设对河流物理生境质量和河流纵向连通性的影响。结果表明,水电梯级开发后,五布河干流未受水坝明显影响河段、库区河段、减水河段分别为20.48、43.34、18.09 km,占总长度的25.0%、52.9%、22.1%。藻渡河干流河口至双河口段未受水坝明显影响河段、库区河段、减水河段分别为58.61、8.28、18.99 km,占总长度的68.2%、9.6%、占22.1%。水电梯级开发后,五布河干流河流片段由26个增至29个,藻渡河干流河流片段由2个增至5个。两条河流纵向连通性分别降低了7.8%和38.0%。五布河坝下减水河段生境质量降低14.1%,库区河段生境质量变化不明显。藻渡河减水河段生境质量与近自然河段无显著差异;两座坝后式电站库区河段生境质量明显低于近自然河段。水电梯级开发对两条河流物理生境的影响与水坝位置选择、建坝前的自然阻隔数量与分布、河流地貌特征、水电资源开发方式等密切相关。 相似文献
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- Many rivers are oversaturated in methane (CH4) and carbon dioxide (CO2) relative to the atmosphere, but we know little about the biological controls on the balance between these two important greenhouse gases and how they might respond to warming.
- We characterise the potential response to temperature in the biological production of CO2 and CH4 and the subsequent microbial oxidation of that CH4, that is the sink and source components of the CH4 cycle, in contrasting river bed sediments: fine sediments, which are largely anoxic, and oxic, coarse gravels.
- In the fine sediments, anaerobic production of both CH4 and CO2 increased with temperature, with apparent activation energies for each being 0.51 eV and 0.24 eV, respectively. The difference between the two resulted in a 4% increase in the ratio of CH4:CO2 production for a 1 °C increase in temperature.
- In the coarse gravels, microbial CH4 oxidation showed no response to temperature at CH4 concentrations characteristic of these gravel beds (30–200 nmol CH4 L?1), due to strong substrate limitation. In contrast, at higher (although still rate limiting) CH4 concentrations, more characteristic of the fine sediment patches (2–4 μmol CH4 L?1), CH4 oxidation exhibited an increasingly strong response to temperature, eventually exceeding that for CH4 production.
- In the fine sediment, the surface layers had a CH4 oxidation capacity over 100 times greater than the gravels and the kinetic response to differing pore water CH4 concentrations meant CH4 was oxidised some 2000 times faster in the fine sediment patches compared with the coarse gravels.
- The calculated kinetic and temperature responses showed that with warming, methanogenesis is unlikely to outstrip methanotrophy and the ratio of CO2 to CH4 emitted could be conserved. Consequently, any changes in the efflux ratio of CH4 to CO2 are unlikely to be due to the incapacity of methanotrophy to respond to CH4 production, but rather to a physical bypassing of the methanotrophic community (e.g. through ebullition or transport via plant stems) or contraction of the oxic layer.
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Joachim Audet David Bastviken Mirco Bundschuh Ishi Buffam Alexander Feckler Leif Klemedtsson Hjalmar Laudon Stefan Lfgren Sivakiruthika Natchimuthu Mats
quist Mike Peacock Marcus B. Wallin 《Global Change Biology》2020,26(2):629-641
Streams and river networks are increasingly recognized as significant sources for the greenhouse gas nitrous oxide (N2O). N2O is a transformation product of nitrogenous compounds in soil, sediment and water. Agricultural areas are considered a particular hotspot for emissions because of the large input of nitrogen (N) fertilizers applied on arable land. However, there is little information on N2O emissions from forest streams although they constitute a major part of the total stream network globally. Here, we compiled N2O concentration data from low‐order streams (~1,000 observations from 172 stream sites) covering a large geographical gradient in Sweden from the temperate to the boreal zone and representing catchments with various degrees of agriculture and forest coverage. Our results showed that agricultural and forest streams had comparable N2O concentrations of 1.6 ± 2.1 and 1.3 ± 1.8 µg N/L, respectively (mean ± SD) despite higher total N (TN) concentrations in agricultural streams (1,520 ± 1,640 vs. 780 ± 600 µg N/L). Although clear patterns linking N2O concentrations and environmental variables were difficult to discern, the percent saturation of N2O in the streams was positively correlated with stream concentration of TN and negatively correlated with pH. We speculate that the apparent contradiction between lower TN concentration but similar N2O concentrations in forest streams than in agricultural streams is due to the low pH (<6) in forest soils and streams which affects denitrification and yields higher N2O emissions. An estimate of the N2O emission from low‐order streams at the national scale revealed that ~1.8 × 109 g N2O‐N are emitted annually in Sweden, with forest streams contributing about 80% of the total stream emission. Hence, our results provide evidence that forest streams can act as substantial N2O sources in the landscape with 800 × 109 g CO2‐eq emitted annually in Sweden, equivalent to 25% of the total N2O emissions from the Swedish agricultural sector. 相似文献
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全球温室气体排放概况 总被引：7，自引：0，他引：7
全球温室气体排放概况曹志平（中国农业大学资源与环境学院生态系,北京１０００９４）ＩｎｔｒｏｄｕｃｔｉｏｎｏｆＧｌｏｂａｌＥｍｉｓｓｉｏｎｓｏｆＧｒｅｅｎｈｏｕｓｅＧａｓ．ＣａｏＺｈｉｐｉｎｇ（ＣｏｌｅｇｅｏｆＲｅｓｏｕｒｃｅｓａｎｄＥｎｖｉｒｏｎｍ... 相似文献
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通过田间试验研究了不同缓/控释尿素对水稻产量和稻田周年温室气体排放的影响,评估生产单位质量水稻的温室气体排放量.结果表明: 优化施肥(OPT)处理在减氮(N)21.4%条件下产量与习惯施肥(FFP)处理持平,同时减少了稻田周年CH4和N2O的排放,其中水稻季CH4和N2O分别减排12.6%和12.5%,休闲季N2O减排33.3%.与OPT处理相比,控释尿素(CRU)处理在水稻季CH4减排28.9%,休闲季CH4零排放;硝化抑制剂(DMPP)处理在水稻季CH4和N2O分别减排41.6%和85.7%,休闲季CH4和N2O分别减排76.9%和6.5%.休闲季节N2O排放占周年N2O排放的76.8%～94.9%,是评价整个稻田温室气体排放不容忽视的因素.OPT、CRU和DMPP处理生产1.0 kg稻谷的温室气体排放强度分别为0.50、0.41和0.33 kg·kg-1,综合考虑周年的温室气体排放总量和产量,尿素和硝化抑制剂配合施用可以在保证水稻产量的情况下,减少温室气体的排放. 相似文献
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不同氮肥对东北春玉米农田温室气体周年排放的影响 总被引：1，自引：0，他引：1
为探明不同氮肥条件下高纬度农田土壤的温室气体排放特性,采用静态箱-气相色谱法研究了常规施氮(CN)、施用缓释肥(SLN)、尿素添加硝化抑制剂和脲酶抑制剂(NIUI)、不施氮肥(NN)对东北春玉米农田土壤温室气体排放的影响.结果表明: CN、SLN和NIUI处理产量分别为9618、9376和9645 kg·hm-2.与CN处理相比,SLN促进了玉米生长季土壤N2O的排放,降低了非生长季土壤N2O的排放;NIUI处理N2O累积排放量比CN降低了39.0%;各处理土壤CO2周年累积排放通量无显著差异;东北春玉米田是大气中CH4的弱汇,NIUI处理较CN促进了玉米生长季土壤对CH4的吸收.综上,尿素添加脲酶抑制剂和硝化抑制剂可以在实现玉米高产的同时有效减少土壤温室气体排放. 相似文献
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Sarah M. Collier Matthew D. Ruark Lawrence G. Oates William E. Jokela Curtis J. Dell 《Journal of visualized experiments : JoVE》2014,(90)
Measurement of greenhouse gas (GHG) fluxes between the soil and the atmosphere, in both managed and unmanaged ecosystems, is critical to understanding the biogeochemical drivers of climate change and to the development and evaluation of GHG mitigation strategies based on modulation of landscape management practices. The static chamber-based method described here is based on trapping gases emitted from the soil surface within a chamber and collecting samples from the chamber headspace at regular intervals for analysis by gas chromatography. Change in gas concentration over time is used to calculate flux. This method can be utilized to measure landscape-based flux of carbon dioxide, nitrous oxide, and methane, and to estimate differences between treatments or explore system dynamics over seasons or years. Infrastructure requirements are modest, but a comprehensive experimental design is essential. This method is easily deployed in the field, conforms to established guidelines, and produces data suitable to large-scale GHG emissions studies. 相似文献
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为了解西安市温室气体排放的动态规律和排放水平,基于全球标杆的温室气体排放等级评价方法,并采用国际公认的《2006年IPCC国家温室气体清单指南》和基于IPCC的《省级温室气体编制指南》推荐的方法对西安市的温室气体排放进行了动态分析和排放等级评估。结果表明,从1995年到2011年,西安市温室气体排放呈快速上升趋势,16年间温室气体排放量从1207.16×104t上升为3934.17×104t,年均增高7.66%。增幅最高的是水泥温室气体(年均增高11.75%)、废弃物(8.77%)和能源(7.63%),农业年均降低1.74%,林业固碳年圴增加3.56%。从温室气体构成看,能源占80.13%—90.55%,水泥占1.75%—7.49%,农业占1.86%—8.01%,林业固碳占-2.58%—-5.22%,废物处理占7.52%—16.38%。可见能源消费的增加是导致西安市温室气体排放增长的主要原因,林业碳汇能力有待提高。万元GDP温室气体排放不断降低,说明西安市碳减排方面的科技进步在不断提高。人均、单位面积温室气体排放量和排放指数增速很快,年均增幅分别达5.84%、7.66%和6.84%。西安市温室气体排放等级持续增高,16年间从较低等级(Ⅰc)上升为中下等级(Ⅱa),目前距应对气候变暖目标(Ⅰb)已高出两个亚级,温室气体排放增高的趋势不容忽视。 相似文献
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基于1961-2017年环渤海地区60个地面气象站点的逐日气温和降水资料,计算了各站点逐日气象干旱综合指数（Meteorological drought Composite Index,MCI）,统计近57年各站点的气象干旱过程,并进一步分析了环渤海地区各季节气象干旱的时空变化特征及致灾危险性等级分布。结果表明：（1）环渤海地区春季干旱覆盖范围和持续日数呈下降趋势,但干旱强度有所增加,夏、秋两季干旱覆盖范围和持续日数呈上升趋势,而干旱强度有所减少,冬季干旱覆盖范围和干旱强度均呈增加状态,干旱持续日数有所下降。（2）春季干旱覆盖范围、干旱持续日数、干旱强度以及干旱发生频率均居四季之首,干旱状况最严重,夏、秋季次之,冬季最轻。（3）各季节干旱强度和干旱发生频率的高值区主要分布在辽宁西北部、河北中南部以及山东大部分地区,低值区主要位于辽宁东部地区。（4）各季节干旱致灾危险性等级总体呈西高东低、南高北低的分布特征,其中,河北中南部气象干旱的致灾危险性较高,辽宁东部的较低;春旱致灾危险性总体较高,夏、秋季次之,冬季最低。 相似文献
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采用静态暗箱-气相色谱法,研究施用生物炭与添加硝化抑制剂对菜地周年综合温室效应的影响.结果表明: 与不施用生物炭相比,施用生物炭处理N2O和CH4的综合温室效应增加8.7%~12.4%,蔬菜产量增加16.1%~52.5%,温室气体强度降低5.4%~28.7%.添加硝化抑制剂显著减少N2O排放,不影响CH4排放,综合温室效应减少17.5%~20.6%,蔬菜产量增加21.2%~40.1%,温室气体强度显著降低.混合施用生物炭与硝化抑制剂一方面增加蔬菜产量,另一方面显著增加综合温室效应(增幅为10.6%～11.2%).因此,在菜地添加硝化抑制剂,既能保证蔬菜产量又能减少温室气体排放,是合适的减排措施. 相似文献
