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Tropical forests have been recognized as having global conservation importance. However, they are being rapidly destroyed in many regions of the world. Regular monitoring of forests is necessary for an adaptive management approach and the successful implementation of ecosystem management. The present study analyses the temporal changes in forest ecosystem structure in tribal dominated Malkangiri district of Orissa, India, during 1973–2004 period based on digitized forest cover maps using geographic information system (GIS) and interpretation of satellite data. Three satellite images Landsat MSS (1973), Landsat TM (1990) and IRS P6 LISS III (2004) were used to determine changes. Six land cover types were delineated which includes dense forest, open forest, scrub land, agriculture, barren land and water body. Different forest types were also demarcated within forest class for better understanding the degradation pattern in each forest types. The results showed that there was a net decrease of 475.7 km2 forest cover (rate of deforestation = 2.34) from 1973 to 1990 and 402.3 km2 (rate of deforestation = 2.27) from 1990 to 2004. Forest cover has changed over time depending on a few factors such as large-scale deforestation, shifting cultivation, dam and road construction, unregulated management actions, and social pressure. A significant increase of 1222.8 km2 agriculture area (1973–2004) clearly indicated the conversion of forest cover to agricultural land. These alterations had resulted in significant environmental consequences, including decline in forest cover, soil erosion, and loss of biodiversity. There is an urgent need for rational management of the remaining forest for it to be able to survive beyond next decades. Particular attention must be paid to tropical forests, which are rapidly being deforested. 相似文献
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Tin and rare metal-bearing granitic pegmatites in the Bastar–Malkangiri pegmatite belt of Central India are hosted by metabasic and metasedimentary country rocks. Fluid inclusion studies were conducted in spatially associated two-mica granite and the staniferous and non-staniferous pegmatites to characterize the physicochemical environment of mineralization, to distinguish different pegmatites in terms of their fluid characteristics and to envisage a possible genetic link between the pegmatites and spatially associated granite. Three different types of primary inclusions were identified. The type-I, aqueous bi-phase (L+V) inclusions are the most abundant and ubiquitous. Type-II polyphase (L+V+S) inclusions are rare. Type-III, monophase (L) and metastable aqueous inclusions, though less abundant than type-I inclusions, are ubiquitous. The fluid evolution trends indicate that mixing of two different fluids of contrasting salinities, one of high salinity (20–30 wt% NaCl equivalent) and another of low salinity (0–10 wt% NaCl equivalent), was responsible for precipitation of the bulk of the cassiterite. This mixing is the single most important characteristic that distinguishes the staniferous pegmatites from their non-staniferous counterparts. The non-staniferous pegmatites, on the other hand, are typified by the presence either of a high saline or a low saline fluid that evolved through simple cooling. The minimum pressure–temperature of entrapment, estimated from the intersections of the halide liquidus with the corresponding inclusion isochores of type-II inclusions, range between 2.1–2.2 kb and 300–325 °C. The similar P–T range of fluid entrapment of the staniferous and non-staniferous pegmatites indicates that they were possibly emplaced within a similar physical environment. Type-I inclusions from granite recorded only the high salinity fluid, the salinity of which compares well with that of the highly saline fluid component of type-I inclusions in the pegmatites. This is a possible indication of a genetic link between the pegmatites and spatially associated granite. 相似文献
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热带森林覆被的时空动态评价——以印度Malkangiri district of Orissa为例 总被引：1，自引：1，他引：0
Tropical forests have been recognized as having global conservation importance. However,they are being rapidly destroyed in many regions of the world. Regular monitoring of forests is necessary for an adaptive management approach and the successful implementation of ecosystem management. The present study analyses the temporal changes in forest ecosystem structure in tribal dominated Malkangiri district of Orissa,India,during 1973-2004 period based on digitized forest cover maps using geographic information system (GIS) and interpretation of satellite data. Three satellite images Landsat MSS (1973),Landsat TM (1990) and IRS P6 LISS III (2004) were used to determine changes. Six land cover types were delineated which includes dense forest,open forest,scrub land,agriculture,barren land and water body. Different forest types were also demarcated within forest class for better understanding the degradation pattern in each forest types. The results showed that there was a net decrease of 475.7 km2 forest cover (rate of deforestation = 2.34) from 1973 to 1990 and 402.3 km2 (rate of deforestation = 2.27) from 1990 to 2004. Forest cover has changed over time depending on a few factors such as large-scale deforestation,shifting cultivation,dam and road construction,unregulated management actions,and social pressure. A significant increase of 1222.8 km2 agriculture area (1973-2004) clearly indicated the conversion of forest cover to agricultural land. These alterations had resulted in significant environmental consequences,including decline in forest cover,soil erosion,and loss of biodiversity. There is an urgent need for rational management of the remaining forest for it to be able to survive beyond next decades. Particular attention must be paid to tropical forests,which are rapidly being deforested. 相似文献
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