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排序方式: 共有993条查询结果,搜索用时 15 毫秒
991.
Marc Herlyn 《Journal of Sea Research》2005,53(4):243-253
The aim of this investigation was to develop appropriate methods for quantitative assessment of blue mussel beds. Combined methods of remote sensing, ground truth investigation and sampling in the field were applied to mature and young intertidal mussel beds. Three variables were measured to obtain reliable quantitative estimates of biomass and abundance: the total area covered by a bed; the cover, i.e. the area of mussel-covered patches in relation to the total mussel bed area; and the proportion, i.e. the area covered by mussels within the patches in relation to the total area of mussel patches. Cover and proportion of intertidal blue mussel beds were measured in the field by the transection method. Aerial photographs enabled the total area of the beds to be determined and large-scale surveys of mussel beds to be carried out synchronously. By examining large-scale aerial photographs it was possible also to determine the cover by remote sensing. The proportion could not be derived from aerial photographs, even from pictures at the largest scale tested during this investigation (scale 1:2500). By statistical methods it was estimated that 12 sub-samples (each covering 177 cm2) from mature beds, and 12 sub-samples (each covering 38 cm2) from young beds are needed to obtain reliable data on biomass and abundance. 相似文献
992.
The importance of shale composition and pore structure upon gas storage potential of shale gas reservoirs 总被引:14,自引:0,他引:14
The effect of shale composition and fabric upon pore structure and CH4 sorption is investigated for potential shale gas reservoirs in the Western Canadian Sedimentary Basin (WCSB). Devonian–Mississippian (D–M) and Jurassic shales have complex, heterogeneous pore volume distributions as identified by low pressure CO2 and N2 sorption, and high pressure Hg porosimetry. Thermally mature D–M shales (1.6–2.5% VRo) have Dubinin–Radushkevich (D–R) CO2 micropore volumes ranging between 0.3 and 1.2 cc/100 g and N2 BET surface areas of 5–31 m2/g. Jurassic shales, which are invariably of lower thermal maturity ranging from 0.9 to 1.3% VRo, than D–M shales have smaller D–R CO2 micropore volumes and N2 BET surface areas, typically in the range of 0.23–0.63 cc/100 g (CO2) and 1–9 m2/g (N2). 相似文献
993.
Ludmila de Freitas Marcílio Vieira Martins Filho José Carlos Casagrande Ivanildo Amorim de Oliveira Luiz Gabriel da Silva 《Environmental Earth Sciences》2018,77(18):642
The evaluation of soil quality is an important tool for degradation monitoring and sustainable management implementation. The objective of this study was to measure physical and chemical soil properties to set soil quality and validate a model of soil quality indicator in latosols (oxisols) under sugarcane cropping and native forest. The study was carried out in the cities of Araras, Santa Ernestina, and Guariba in São Paulo State, Brazil. We collected 24 samples of disturbed and undisturbed soil at 0.0–0.10 m layer from three areas grown with sugarcane and neighboring locations under native woodland. We assessed the following soil properties: (a) chemical—pH in CaCl2, organic matter (OM), phosphorus (P), potassium (K+), calcium (Ca2+), magnesium (Mg2+), potential acidity (H?+?Al), aluminum (Al3+), and sulfur (S); (b) physical—macro- and microporosity, soil bulk density (Ds), aggregate stability, mean weight diameter (MWD), rill (Kr) and interrill (Ki) global erodibility, shear stress (τc), and magnetic susceptibility (MS). Data underwent multivariate statistics to identify the properties that denote soil quality and to set their weights within the functions of soil quality indicator (SQI). This study showed that the multivariate analysis was efficient in determining which physical and chemical properties were most sensitive, of which we can mention total sand, MS, clay, microporosity, Mg, Ca, pH, and OM. We can therefore conclude that the quality indicators of soils grown with sugarcane were lower than those under forest were, showing the need for adoption of conservation management practices. 相似文献