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排序方式: 共有407条查询结果,搜索用时 343 毫秒
91.
对甘肃省2000-2009年的碳源和碳汇进行了研究,获得了该地区碳源、碳汇随时间变化的预测模型,并预测了未来的发展趋势.结果表明,甘肃省碳源由2000年的4.294 7×108 t/a逐年增加至2009年的5.6307×108t/a,10年间增加了31.11%.而同期碳汇由3.9595×108t/a逐年增加到4.8991×108t/a,仅增加了23.73%.显然,碳源的增加速率高于碳汇.甘肃省2000年碳失汇为0.3352×108t/a,2009年增至0.7316×108 t/a.预测甘肃省2015年碳源总量将达到6.7193×108t/a,碳汇总量为5.5487×108 t/a,碳失汇将达到1.1706×108t/a.显而易见,如不改变现有的发展模式,甘肃碳源与碳汇的失衡将不断加剧,碳安全面临更严峻的考验. 相似文献
92.
中国东北红河国家级自然保护区湿地植被空间格局与环境梯度关系(英文) 总被引:1,自引:0,他引:1
Quantifying correlation between the spatial patterns of natural wetland plants and environmental gradient gives better understanding of wetland habitats, which is the fundamental for the strategy making on the protection and restoration of natural wetlands. In this study, the spatial patterns of wetland plants and the environmental gradient of wetland habitats were assessed in the Honghe National Nature Reserve (HNNR) in Northeast China, a wetland of international importance on the Ramsar list. Biophysical parameters’ values of wetland plants were obtained by field sampling methods, and wetland mapping at the community scale was completed using remote sensing techniques. Digital delineation of the surface water system, hydrological zoning and wetness index were produced by spatial analysis methods in Geographic Information System. An ecological ordination method and two clustering methods were used to quantify the relationship between the spatial distribution patterns of wetland plants and the corresponding environmental gradients. Such quantitative analyses also present the specific diversity of different types of wetland plants based on the environmental attributes of their habitats. With the support from modern geo-information techniques, the experimental results indicate how four ecotypes of wetland plants spatially transit from forest swamp, shrub wetland and meadow into marsh wetland with increasing wetness index and water table. And they also show how wetland spatial distribution patterns are controlled by an environmental gradient of wetness. Another key finding of this research work is that our results present the exact fundamental differences between marsh and non-marsh plants of 11 wetland plant communities within the core study area. Hence, this case study gives a good sample for better understanding of the complex correlation between the spatial patterns of wetland plants and their environmental attributes using advanced digital analysis methods. It is also useful to show how to integrate geoinformatic techniques with statistical analysis methods based on the field data base. 相似文献
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Local-scale spatial variability of soil organic carbon and its stock in the hilly area of the Loess Plateau, China 总被引:3,自引:0,他引:3
Soil organic carbon (SOC) is one of the key components for assessing soil quality. Meanwhile, the changes in the stocks SOC may have large potential impact on global climate. It is increasingly important to estimate the SOC stock precisely and to investigate its variability. In this study, Yangjuangou watershed was selected to investigate the SOC distribution under different land uses. We found that SOC concentration decreased with increasing soil depth under all land uses and was significantly different across the vertical soil profile (P < 0.01). However, considering effect of land use on SOC, it is only significant (P < 0.01) in the topsoil (0-5 cm) layer. This indicated that land use has a large effect on the stocks of SOC in the surface soil. The stratification ratio of SOC > 1.2 may mean that soil quality is improving. The order of the SOC density (0-30 cm) under different land uses is forestland > orchard land > grassland > immature forestland > terraced cropland. The SOC stock is found to be as large as 2.67 × 103 t (0-30 cm) in this watershed. Considering time effect of restoration, the slope cropland just abandoned is more efficient for SOC accumulation than trees planted in the semi-arid hilly loess area. 相似文献
95.
Sand waves on the northern South China Sea shelf had been considered as stable relict bed form. For the industry use of sea bed between stations LF13-2 and LF13-1, a new round of explorations were conducted. The newly obtained data show that both spacings and amplitudes of sand waves are all systematically changing with water depth. Repeated observations since 2003 to 2004 showed that the sea bed is currently active. Due to strong erosion of surface sediment since Dongsha (东沙) uplifting, there are almost no... 相似文献
96.
丹宁棉分离富集—发射光谱法同时测定地质样品中微量铌钽锆铪 总被引:1,自引:1,他引:1
采用丹宁棉对地质样品溶液中的铌、钽、锆、铪进行分离富集,将写信后的丹宁棉在600℃灼烧30min,灰分用发射光谱法同时测定四元素。检出限与通常的发射光谱法相比降低约2个数量级,经国家级标准物质检验,结果与标准值相符,精密度试验,各元素的RSD(n=20)为2.6%-7.9%。 相似文献
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介绍了云南丽江高美古天文候选点,1995年12月~1996年11月全夜视宁度观测结果:全年平均r0=16.50cm(FWHM=0.67″),夜平均极大值rmax=22.41cm(0.49″),夜平均极小值rmin=12.95cm(0.85″)。 相似文献
100.