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161.
162.
Laboratory experiments under controlled environmental conditions are a useful tool to investigate the influence of different environmental parameters on VOC emissions from plants individually. Before using the obtained results to interpret measurements under ambient conditions, it has to be ensured that the laboratory system is suitable for performing emission rate measurements under ambient-like conditions to derive algorithms describing the emissions of volatile organic compounds as a function of physical variables like temperature and light intensity. Here we compare results from monoterpene emission rate measurements with Scots pines (Pinus sylvestris L.) under both ambient environmental conditions using a mobile plant enclosure chamber, and under controlled laboratory conditions in a continuously stirred tank reactor. The different analytical instruments to quantify monoterpene emissions were compared in an intercalibration experiment. Measurements of the mixing ratios of -pinene, -pinene, 3-carene, camphene, and limonene on the order of some hundred parts per trillion differed by less than 20%. The laboratory system has proven capable of providing ambient-like conditions and results of monoterpene emission rate measurements under laboratory conditions could be extrapolated to the natural environment. Monoterpene emission rate measurements with identical specimens of Scots pines conducted within small temporal differences under similar laboratory and outdoor conditions agreed well. Both laboratory and outdoor experiments clearly showed that distinct and constant values neither exist for the standard emission rates nor for the emission pattern of monoterpenes from Scots pine. Temporal variations in the standard emission rates from identical specimens and plant-to-plant variations were on the order of one magnitude. 相似文献
163.
《中国科学D辑(英文版)》2006,(Z2)
Long-term measurement of carbon metabolism of old-growth forests is critical to predict their behaviors and to reduce the uncertainties of carbon accounting under changing climate. Eddy covariance technology was applied to investigate the long-term carbon exchange over a 200 year-old Chinese broad-leaved Korean pine mixed forest in the Changbai Mountains (128°28'E and 42°24'N, Jilin Province, P. R. China) since August 2002. On the data obtained with open-path eddy covariance system and CO2 profile measurement system from Jan. 2003 to Dec. 2004, this paper reports (i) annual and seasonal variation of FNEE, FGPP and Re; (ii) regulation of environmental factors on phase and amplitude of ecosystem CO2 uptake and release Corrections due to storage and friction velocity were applied to the eddy carbon flux. Lal and soil temperature determined the seasonal and annual dynamics of FGPP and RE separately. VPD and air temperature regulated ecosystem photosynthesis at finer scales in growing seasons. Water condition at the root zone exerted a significant influence on ecosystem maintenance carbon metabolism of this forest in winter. The forest was a net sink of atmospheric CO2 and sequestered -449 g C·m-2 during the study period; -278 and -171 gC·m-2 for 2003 and 2004 respectively. FGPP and FRE over 2003 and 2004 were -1332, -1294 g C·m-2. and 1054, 1124 g C·m-2 respectively. This study shows that old-growth forest can be a strong net carbon sink of atmospheric CO2. There was significant seasonal and annual variation in carbon metabolism. In winter, there was weak photosynthesis while the ecosystem emitted CO2. Carbon exchanges were active in spring and fall but contributed little to carbon sequestration on an annual scale. The summer is the most significant season as far as ecosystem carbon balance is concerned. The 90 days of summer contributed 66.9, 68.9% of FGPp, and 60.4, 62.1% of RE of the entire year. 相似文献
164.
本系统是利用掌上电脑的屏幕触控技术,开发智能标绘功能,使防火工作人员在发现着火点的同时依据导航信息快速地在电子地图上标绘火头、火线的位置,撰写火情报告并输出态势图,然后通过无线上网功能,实时将标绘的信息传送给防火指挥中心,为指挥中心及时做出扑火决策提供支持。 相似文献
165.
166.
The Ratcliff Site in southwestern Virginia lies in a small second-order stream valley filled with approximately 3.5 m of organic-rich deposits that contain bones of mammoth, mastodon, deer (or antelope), logs, and plant macrofossils. Radiocarbon analyses indicate the age of the organic-rich sediment ranges from > 44,000 to 29,100 14C yr BP, a time period with no fossil remains reported in this region of the Appalachians. Analyses of field observations, textural data, organic carbon content, and plant macrofossils indicate that the organic-rich sediments contain interbedded standing-water and debris-flow deposits. Up to 6 m of oxidized debris-flow sediments bury the organic-rich sediments. The presence of Rubus parviflorus (Thimble Berry) throughout the deposit indicates the site had a boreal environment from > 44,000 to 29,100 14C yr BP. Plant macrofossil evidence indicates the uplands had stands of spruce/jack-pine forests while the valley contained ponds and associated wetlands. Three debris flows occurred at the site between approximately 38,000 and 29,000 14C yr BP, suggesting a recurrence interval for major storms of approximately 3000 yr, even though the apparent stability of the boreal environment implies a climate not conducive to catastrophic rainstorms. This conflicting combination of features suggests that during the middle Wisconsinan this area experienced generally cool climates, dominated by polar air masses, but was punctuated by relatively brief warm periods marked by incursions of tropical air masses. 相似文献
167.
Tackling fuel poverty is central to the delivery of the Scottish Executive’s commitment to social justice. Many Scottish rural households are not linked into the mains gas network and rely on expensive alternatives, despite being surrounded by plentiful supplies of low-cost renewable wood biomass. A regional study was undertaken to establish the potential market for pelletised wood fuel, available as a low-value by-product from the rapidly expanding Scottish forest industry sector. The wider implications of the research findings are analysed by extending the principles of industrial symbiosis from a site-specific to a regional scale. Promoting an indigenous pellet-based wood fuel market for rural Scotland would fulfil important Scottish Executive economic, social and environmental sustainability objectives. Adding off-site social symbiotic elements increases the potential for on-site technical symbiosis in nascent Scottish forest industry clusters. At present, market failure is preventing the realisation of these benefits, and the paper concludes by identifying ways in which market intermediation, through wood fuel energy service companies, might overcome the current barriers to exploiting such symbiosis. 相似文献
168.
In 1988, four states in the northeastern USA commissioned a study to address land use changes in the Northern Forest, 26 million acres of temperate and boreal forest extending from Maine to eastern New York State. Against a backdrop of economic destabilization and concerns regarding social and ecological implications of a real estate boom, the sustained deliberative dialogue catalyzed by this study has come to rely heavily on the ambiguous concept of “working forest.” To clarify political and environmental dynamics in the region, we analyzed how people respond to and seek to capitalize on the interpretive flexibility of the term working forest. We combine an analysis of socio-political discourses of working forest based on a structured literature review with an assessment of local peoples’ definitions of working forest based on a survey conducted in a pair of contrasting New York State communities. The first study site represents an amenity-oriented community (i.e. a place where the forest supports a service economy including recreation and tourism) and the other study site represents a timber-dependent community. By linking data from community-level analysis to data derived from a general analysis of forest politics, we seek to develop a more robust perspective. By comparing discourses across differently structured communities, we investigate how local forest politics are mediated by local economic development processes. Our study empirically illustrates contested and geographically uneven processes of social construction of environment and rural development in a region confronting pressures of globalization. Results indicate that timber harvesting is a heavily privileged management objective, as a logic of ‘the forest that pays is the forest that stays’ dominates. Environmental politics in the region, and perhaps more generally, increasingly conforms to a form of pragmatism in which economic opportunities structure conservation planning and investment. 相似文献
169.
170.
Linking the Sulu UHP belt to the Korean Peninsula: Evidence from eclogite, Precambrian basement, and Paleozoic sedimentary basins 总被引:13,自引:0,他引:13
Mingguo Zhai Jinghui Guo Zhong Li Daizhao Chen Peng Peng Tiesheng Li Quanlin Hou Qicheng Fan 《Gondwana Research》2007,12(4):388-403
Considerable debate on whether and how the Sulu Orogenic Belt extends eastward to the Korean Peninsula has remained over the past decade. New results reported here include the following: (1) an eclogite and retrograded eclogite-bearing complex (Hongseong Complex) is discovered in South Korea, in which the eclogite occurs as lenses in circa 810–820 Ma granitic gneiss. SHRIMP zircon dating of the eclogite yields 230 Ma for the metamorphic age and 880 Ma for the protolith age; (2) The basement of the Rangnim, Gyeonggi and Yeongnam massifs have affinities to the basement of the North China Block (NCB). However the Gyeonggi Massif encloses a minor amount of large or small slabs of the Hongseong Complex that are similar to the rocks of the Sulu Belt. (3) Two main Paleozoic basins within the Rangnim and Gyeonggi massifs have a similar Paleozoic tectono-stratigraphy to the NCB. (4) The Imjingang and Ogcheon belts do not exhibit any metamorphic characteristics of collisional orogenic belts. Based on these facts, we propose a crustal-detachment and thrust model and suggest that the collision belt between the Yangtze Block (YB) and NCB (Sino–Korea Craton) is preserved along the western margin of the Korean Peninsula. The lower part of the UHP metamorphosed lithosphere of the YB was subducted under the Korean Peninsula and not uplifted to the surface. The lower crust of the YB (the Hongseong Complex) was detached from the subducted lithosphere and thrust over the Korean Peninsula, and inserted into the basement rocks of the Gyeonggi Massif. The upper crust of the YB possibly was detached from the lower crust and overthrusted along the Honam and Chugaryong shear zones. The Imjingang and Ogcheon belts possibly represent the detached upper crust of YB and their present occurrences are controlled by a Mesozoic strike–slip shear structure. All these detached lower and upper crustal slabs were strongly deformed during the Late Jurassic and Early Cretaceous tectonic event leading to their present geological distribution and characteristics. 相似文献