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991.
Senlin LU Longyi SHAO Minghong WU Zheng JIAO JONES T. P. 《中国地球化学学报》2006,25(B08):2-2
In order to better understand what controls carbonate weathering rates, we report results from the Jura Mountains (East France), an area exclusively composed of carbonate rocks. This region presents an altitude gradient increasing from 250 m to 1300 m. Over the basin, this gradient generates climatic contrasts of 5℃ and a runoff three times higher in altitude. This place offers a good opportunity for understanding the controlling factors of carbonate weathering. Contrary to thermodynamic calculations that predict the highest concentrations at low temperature, we observe that carbonate dissolution is two times higher at low elevation than in the mountains. This observation can only be explained by a variation in soil pCO2. In order to better constrain the observed variation in cation contents (principally Ca and Mg) of rivers, we used the ASPECTS ecological model (Rasse et al., 2001). Based on both hourly climatic data, vegetation type and soil type, ASPECTS may reconstruct pCO2 in soil. 相似文献
992.
本文在搜集了大量生态环境历史变迁及气象灾害史料的基础上,应用历史学、生态学、环境学、灾害学等多学科理论与方法,对山西中部地区自明代前中期以来近500年的生态环境劣变过程,以及在其影响下的气象灾害变化情况进行了分析研究后,得出初步结论:森林毁坏导致生态环境破坏,具有不可逆性和累积性的特征。生态环境一旦被破坏就很难恢复;生态环境遭破坏引发4个方面恶果:一是水土流失会长期存在,并逐趋加重。二是洪涝灾害明显加剧。三是干旱频率显著增大。四是局地性强对流天气造成的灾害趋于严重。森林毁坏,生态环境恶化导致气象灾害加剧,反过来气象灾害加剧又促使生态环境进一步恶化。 相似文献
993.
本研究系应用数字地球系统理论于中央山脉保育轴经营管理机制建置 ,并依 IUCN之保育区划设标准 ,作为未来研订中央山脉保育计划之分区准则与数字台湾系统建立之发展模式。数字台湾之观念乃源于数字地球突破传统信息空间、政策经营之多向度信息整合 ,同时考虑克服科技应用与时间效益以及决策兼蓄解决传统资源管理在空间地理与生态艺术上之综合性问题。 相似文献
994.
995.
TM 图像在城市绿地调查中的应用 总被引:1,自引:0,他引:1
城市绿化水平是衡量城市生态环境质量和平衡状况的主要标准,因此,收集城市的绿化信息非常重要.传统的借助人力实地勘察的手段费时费力且数据不准确,成了制约城市绿化建设的瓶颈问题.以TM卫星图像的数据源为线索,辅之以一系列遥感图像的处理方法,如几何校正、图像增强、波段组合、专题信息提取、数据的换算等,适当结合实地踏查,就能准确及时便捷地收集城市的绿化信息,为制定合理科学的城市规划提供依据. 相似文献
996.
Ge Yu Xiangjun Sun Boqiang Qin Changqing Song Haiyu Li I. C. Prentice P. S. Harrison 《中国科学D辑(英文版)》1998,41(2):130-136
Biomization provides an important way to assign pollen taxa to biomes and to simulate palaeo-vegetation patterns, so that
pollen data can be mapped to reconstruct biogeography and climate. The authors have tested the applicability of this procedure
to assign modern pollen surface samples from China to biomes. The procedure successfully delineated the major vegetation types
of China. When the same procedure was applied to 6 ka B. P. fossil pollen samples, the reconstructions showed that the forest
zones were systematically shifted northwards ca. 300–500 km beyond their present northern limits in eastern China; the area
of desert and steppe vegetation was reduced compared to the present in northwestern China; the area of tundra was reduced
largely on the Tibetan Plateau. This research is a contribution to the project of BIOME 6000 in Pacific-Asian regions.
Project supported by the Funding for Returned Students from the Overseas of the State Education Commission of China, the Postdoctoral
Station, and State Pilot Laboratory of Coast & Island Development of Nanjing University, Financial support has also been provided
by European Community (EV5V-CT95-0075) and by the Swedish Natural Science Research Council (G-AA/GU 09334-321). 相似文献
997.
Investigations of the ecological, atmospheric chemical, and climatic impacts of contemporary fires in tropical vegetation have received increasing attention during the last 10 years. Little is known, however, about the impacts of climate changes on tropical vegetation and wildland fires. This paper summarizes the main known interactions of fire, vegetation, and atmosphere. Examples of predictive models on the impacts of climate change on the boreal and temperate zones are given in order to highlight the possible impacts on the tropical forest and savanna biomes and to demonstrate parameters that need to be involved in this process. Response of tropical vegetation to fire is characterized by degradation towards xerophytic and pyrophytic plant communities dominated by grasses and fire-tolerant tree and bush invaders. The potential impacts of climate change on tropical fire regimes are investigated using a GISS GCM-based lightning and fire model and the Model for the Assessment of Greenhouse Gas-Induced Climate Change (MAGICC). 相似文献
998.
第三纪青藏高原面高程与古植被变迁 总被引:18,自引:0,他引:18
收集了近半个世纪以来、几乎全部有关青藏高原第三纪古植被的研究资料,从整体角度对青藏高原的古植被演化史与高原面高程变化史进行了初步研究。认为青藏高原第三纪古植被经历了由古老、湿热环境下的热带低地森林,脉动式地渐变为热带、亚热带山地森林及灌丛草原。反映高原是阶段性、持续上升的,其间不存在大幅的降低过程。冈底斯山、念青唐古拉山、唐古拉山、昆仑山所围限的藏北高原比喜马拉雅山系隆升早,且在整个第三纪都比喜马拉雅山高,到上新世的中、晚期其高度已达海拔3000m以上。喜马拉雅山系成为世界屋脊是第四纪以来的事。 相似文献
999.
A vegetation analysis reveals that the Lai Chi Wo mangrove swamp in Hong Kong has 10 mangrove species comprising 76.9% of
the total number of mangrove species in Hong Kong. This swamp is a mixed community dominated byAegiceras corniculatum, Heritiera littoralis, Excoecaria agallocha, Kandelia candel, Bruguiera gymnorrhiza, with importance values of 37.88, 28.19, 14.33, 11.33 and 8.27 respectively. The community’s mangrove species diversity and
evenness, as based on the Shannon-Wiener Function, were 1.44 and 62.01%, which were lower than those of the south su-tropical
evergreen broad-leaf forest community but its ecological dominance (0.26) was higher. The correlation information field (CIF)
method, a useful analytical method for complex forest community, was adopted in the present mangrove analysis. The species
correlation information was:Aegiceras corniculatum (0.268)>Heritiera littoralis (0.250)>Kandelia candel (0.220)>Excoecaria agallocha (0.169)>Bruguiera gymnorrhiza (0.101). The correlation information of the mangrove community was 1.008.
This work was financially supported by the Agriculture and Fisheries Department of The Hong Kong Government and The Hong Kong
University of Science & Technology. 相似文献
1000.
Christian A. Kull 《The Professional geographer》1998,50(2):163-176
Describing and explaining land-use change is of critical concern in Madagascar, where land transformations such as deforestation and resulting environmental degradation currently capture widespread attention. While the eastern rain forest recedes in the face of swidden cultivators, the highlands demonstrate more constructive transformations. In this paper I present a case study of land-use change in Leimavo, a small village near Ambositra studied in the 1960s by Jean-Pierre Raison. Here, the twentieth century has seen a gradual reduction in irrigated rice cultivation and cattle husbandry, and a boom in market-oriented orange, vegetable, and grain production. In the long term, a historical landscape of grassy hills has been transformed into a productive cultural landscape with woodlots, anti-erosion benching, rice terraces, fruit groves, and diverse crops. Critical factors determining the trajectory of land-use change include regional population pressure, state policies, market incentives, climate variations, and access to land and water resources. These critical factors, or explanations, are linked in the discussion by the use of a simple heuristic device—the range of choice—as a theoretical framework. 相似文献