土壤呼吸的温度敏感性   总被引：14，自引：0，他引：14  

刘洪升  刘华杰  王智平  徐明  韩兴国  李凌浩 《地理科学进展》2008,27(4):51-60

土壤呼吸是指土壤释放CO₂ 的过程,它所释放出的CO₂ 是生物圈向大气圈释放CO₂ 的主要来源之一。土壤呼吸速率对温度变化的敏感性是陆地生态系统碳循环过程中一个十分重要的环节。由于许多大尺度碳循环模型中都涉及土壤呼吸的温度敏感性这一问题,因此对该问题的回答有助于提高对当前陆地生态系统碳通量的估算和对 未来气候变化预测的准确性。本文就目前土壤呼吸速率对温度变化的敏感性的主要问题进行了综述,从温度、水分、呼吸底物的数量和质量、酶促反应动力学等几个不同的方面,概述了土壤呼吸温度敏感性的变异范围较大的原因,以及这些因素对土壤呼吸的温度敏感性影响的机理。土壤呼吸是酶促的化学反应,因此其温度敏感性不仅取决于呼吸底物的质量,同样也取决于底物的有效性。  相似文献   

双矩形钢模管互导干作业地下连续墙   总被引：1，自引：1，他引：0       下载免费PDF全文

张文清  邹正盛  孔清华 《水文地质工程地质》2012,39(2):51-55

地下连续墙常采用泥浆护壁、水下灌注混凝土进行施工,槽壁稳定和槽段接头防渗一直是施工控制的难点。泥浆本身易于造成环境污染,而泥浆制备的水耗和废料处置也增加了工程造价。为解决这些问题,开发了一种新技术——双模管互导干作业地下连续墙技术。该技术采用钢模管护壁和双矩形模管导向沉管挤土或沉管干取土的成墙工艺（分别适用于墙厚300～500mm和600～1 000mm）,不需要泥浆和水下灌注墙混凝土,可以在同一平面内成墙、实现墙单元无缝连接。实践表明,该技术墙体防渗性能好,成墙效率高,连接质量可靠,不仅适用于深厚软粘土地层的基坑围护工程,也可应用于类似地质条件下水库工程的防渗加固。  相似文献   

Macro- and megafauna communities in three deep basins of the South-East Atlantic     

《Deep Sea Research Part I: Oceanographic Research Papers》2013

During ‘Meteor’ expedition ‘DIVA 2’ in 2005 the abyssal macro- and megafauna communities were studied in the northern Cape Basin, in the northern Angola Basin and in the eastern and western Guinea Basin. Water depths varied between 5040 and 5670 m.Surface deposit feeding or predatory ophiuroids dominated the megafaunal community in the northern Cape Basin, sponges, sipunculids and fish in the northern Angola Basin, and asteroids, crustaceans and fish in the eastern Guinea Basin, while in the western Guinea Basin sipunculids dominated.In the northern Cape Basin, peracarid crustaceans were the dominant macrofaunal group, followed by polychaetes and bivalves. In the Guinea Basin, polychaetes, peracarid crustaceans and bivalves dominated, although omnivorous or predatory free-living nematodes of macrofaunal size (>0.5 mm) made up 40–60% of the total abundance, with maxima in the western basin.The chlorophyll a content of sediments was lower in the northern Cape and Angola Basins than in the Guinea Basin, which was consistent with the differences in water masses, primary production and flux rate of organic matter in the three basins of the South-East Atlantic. The differences in structure and function of the macro- and megafauna communities in the three basins correlated with the differences in the amount of food reaching the seafloor in tropical and subtropical settings.  相似文献   

A non-destructive method to estimate biomass in arid environments: A comment on     

N. Montès 《Journal of Arid Environments》2009,73(6-7):599-601

Numerous ecological studies in grasslands and shrublands have used plant cover as a surrogate of aboveground net primary production (ANPP), biomass or biovolume. Regression equations between biomass and plant cover involve taking into account a wide range of vegetation cover. This comment assesses the consequences for biomass estimations of the method presented by Flombaum and Sala [Flombaum, P., Sala, O.E., 2007. A non-destructive and rapid method to estimate biomass and aboveground net primary production in arid environments. Journal of Arid Environments 69, 352–358.], which consists in removing portions of individuals to achieve the desired plant cover estimation. We found that alteration of architecture of individuals could lead to an overestimation of biomass by a factor ranging from 1.05 to 3.16, depending on the extent of the reduction of the plant cover.  相似文献   

不同物候模型对作物发育期模拟的对比分析   总被引：1，自引：0，他引：1       下载免费PDF全文

李荣平  周广胜  王笑影  史奎桥 《气象与环境学报》2012,28(3):25-30

作物发育期预报在农业气象业务中具有重要意义。通过比较4种作物发育期模型的模拟效果,为中国东北地区作物发育期预报提供参考。基于东北地区玉米、水稻和大豆的发育期观测数据及其对应的气象资料,利用模拟退火算法估算了4个发育期模型的参数值,并对模型进行内外部验证。结果表明：在参数本地化过程中,高亮之模型和沈国权模型的效果较好,均方根误差平均分别为3.31d和3.72d。在模型验证过程中,沈国权模型的模拟效果较好,均方根误差平均为5.22d,因此,相对而言,沈国权模型对作物发育期模拟效果较好。  相似文献   

Tree-ring reconstruction of summer temperature for A.D. 1475–2003 in the central Hengduan Mountains, Northwestern Yunnan, China     

Zong-Shan Li  Qi-Bin Zhang  Keping Ma 《Climatic change》2012,110(1-2):455-467

Development of long tree-ring records is an important task in paleoclimate studies. Here we presented a five-century long reconstruction of summer (June to August) temperature based on a tree ring-width chronology of Picea brachytyla var. complanata originating from the Hengduan Mountains of China. Climate-growth response analysis showed that summer temperature was the main climatic factor limiting tree-ring growth in the study area. The reconstructed summer temperature accounted for 47.6% of the variance in actual temperature during their common period A.D. 1958–2002. Analysis of the temperature reconstruction showed that major warm periods occurred in the A.D. 1710s–1750s, 1850s, 1920s–1950s and 1990s to present, whereas cold intervals occurred in the A.D. 1630s–1680s, 1790s–1800s, 1860s–1880s and 1950s–1980s, respectively. The low-frequency variation of the reconstruction agreed fairly well with tree-ring reconstructed temperature from nearby regions and with records of glacier fluctuations in the surrounding high mountains, suggesting that our reconstructed summer temperature was reliable, and could aid in the evaluation of regional climate variability.  相似文献   

Regional-scale winter-spring temperature variability and chilling damage dynamics over the past two centuries in southeastern China   总被引：1，自引：0，他引：1  

Jianping Duan  Qi-Bin Zhang  Lixin Lv  Chao Zhang 《Climate Dynamics》2012,39(3-4):919-928

Winter-spring cold extreme is a kind of serious natural disaster for southeastern China. As such events are recorded in discrete documents, long and continuous records are required to understand their characteristics and driving forces. Here we report a regional-scale winter-spring (January–April) temperature reconstruction based on a tree-ring network of pine trees (Pinus massoniana) from five sampling sites over a large spatial scale (25–29°N, 111–115°E) in southeastern China. The regional tree-ring chronology explains 48.6% of the instrumental temperature variance during the period 1957–2008. The reconstruction shows six relatively warm intervals (i.e., ~1849–1855, ~1871–1888, ~1909–1920, ~1939–1944, ~1958–1968, 1997–2007) and five cold intervals (i.e., ~1860–1870, ~1893–1908, ~1925–1934, ~1945–1957, ~1982–1996) during 1849–2008. The last decade and the 1930s were the warmest and coldest decades, respectively, in the past 160 years. The composite analysis of 500-hPa geopotential height fields reveals that distinctly different circulation patterns occurred in the instrumental and pre-instrumental periods. The winter-spring cold extremes in southeastern China are associated with Ural-High ridge pattern for the instrumental period (1957–2008), whereas the cold extremes in pre-instrumental period (1871–1956) are associated with North circulation pattern.  相似文献   

成都金沙遗址距今3000年的古气候探讨   总被引：2，自引：2，他引：0       下载免费PDF全文

姚轶锋  李奎  刘建  王宇飞  杜乃秋  李承森 《古地理学报》2005,7(4):549-560

成都金沙遗址位于成都西郊金沙村,可能是商代晚期至西周时期（约公元前11世纪–前770年）古蜀国的都邑所在地。本文分析了金沙遗址两个探方WT7908和IT8305的31个孢粉样品,探方IT8305孢粉组合表明：蕨类植物孢子占60.3%,草本被子植物花粉占24.8%,木本裸子和被子植物花粉占14.2%,水生植物花粉相对较少,仅占0.7%。蕨类植物主要以蹄盖蕨科、水龙骨科和凤尾蕨属为主,草本植物中野牡丹科占绝对优势,木本裸子和被子植物中主要以松属和桦木属为主,水生植物主要包括双星藻、鸭跖草科和香蒲属。成都平原在这个时期的气候分为两个阶段,前期阶段的气候属于亚热带温暖湿润气候,平原上生长着茂盛的草本植物和蕨类植物;后期阶段的气候虽然还属于亚热带气候,但较前期更加湿热,气温和降雨量都比前期要高。定量分析和重建了金沙遗址距今3000年的古气候：年均温17.7–19.8ºC、最热月均温21.7–28.6ºC、最冷月均温11.5–11.9ºC、年较差12.1–14.9ºC、年降雨量993.3–1113.3 mm、最大月降雨量224.6–268.1 mm、最小月降雨量6.9–14.1 mm。成都地区3000年前的年均温比现在要高1.7–2.8ºC,而年降雨量基本和现在一致。  相似文献   

陕北统万城地区历史自然景观及毛乌素沙漠迁移速率   总被引：3，自引：0，他引：3       下载免费PDF全文

孙同兴  王宇飞  侯甬坚  杜乃秋  李承森 《古地理学报》2004,6(3):363-371

十六国时期夏国都城--统万城位于陕西省靖边 县城北无定河北岸,今天的自然景观属 于沙漠,仅存稀疏的次生灌丛和草本群落。但是,在约1600年以前,当地为温带干草原, 在塬面或山丘上分布有侧柏林,沟谷、河岸边生长喜温湿的乔木,河流、湖泊、沼泽中水生 植物繁盛,在丘间低洼处或盐碱土上分布有灌木和草本植物。当时该地区的年平均温度为7 8℃～9.3℃,最热月平均温度23.0℃～24.9℃,最冷月平均温度-12℃～-5.6℃,年 较差285℃～38.2℃,年 降雨量403.4～550.0 mm,最大月降雨量83.8～123.9 mm,最小月降雨量为4.4～1 2.2 mm。 当时的年平均温度比现在高出0.2℃～0.7℃,年降雨量也高出60～100 mm。如此的历史景 观今天 已经向南迁移,侧柏林或森林草原退缩至延安以南。在此近 1600年的时间里,毛乌素沙漠 分布范围不断扩大,其南部边缘推进了约200 km,推测沙漠扩展的速率达到平均125 m/ a。  相似文献   

Significance of Late Devonian – Lower Carboniferous ages of hydrothermal sulphides and sericites from the Urals Volcanic-Hosted Massive Sulphide deposits     

《Ore Geology Reviews》2017

Formation of the Urals Volcanic-Hosted Massive Sulphide (VHMS) deposits is considered to be related with the intra-oceanic stage of the island arc(s) development in Late Ordovician – Middle Devonian time (ca. 460–385 Ma) based on the biostratigraphic record of ore-hosting sedimentary rocks. However, the known radiometric ages of ore hosting volcanics are very limited. Here we present direct dating results of sulphide mineralisation from the Yaman-Kasy and Kul-Yurt-Tau VHMS deposits using Re-Os isotope systematics showing similar mineralisation ages of 362 ± 9 Ma and 363 ± 1 Ma. These ages coincide with the previous Re-Os dating of the Alexandrinskoe (355 ± 15 Ma) and Dergamysh (366 ± 2 Ma) VHMS deposits. This Late Devonian (Famennian) age corresponds to the late stage of the ‘Magnitogorsk arc – Laurussia continent’ collision event and coincides with a beginning of large scale subduction-related granitoid magmatism. The younger mineralisation age relative to the biostratigraphic ages of host rocks is interpreted as one of the latest episodes of the multi-stage history of VHMS deposits development. Ar-Ar ages of sericites from metasomatic rocks of Barsuchi Log and Babaryk deposits show even younger ages clustering around 345 Ma, and testify another late hydrothermal event in the history of the Urals VHMS deposits.  相似文献