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Xinjiang University (2002)

The Landscape Heterogeneity Of Arid Oasis-Desert Ecosystem And Possible Response To Regional Climate Change

ZhangJie

Titre : The Landscape Heterogeneity Of Arid Oasis-Desert Ecosystem And Possible Response To Regional Climate Change

Auteur : Zhang Jie

U8niversité : Xinjiang University

Grade : Master (Thesis) 2002

Résumé
At multi-scale level we have studied the spatial heterogeneity of oasis-desert landscape patterns and classificied the landscape types of the mountain-oasis-desert ecosystem in Xinjiang at landscape scale and regional scale in the dissertation. Combined with 20 years climate data sets form 50 stations and using the NOAA/AVHRR FVC (Fractional vegetation cover) data to study the possible effects of climatic change on the oasis-desert regional landscape in Xinjiang.The GIS technique supported by Arc/info software was used to analyze the heterogeneity of oasis-desert ecosystem and its mosaic of patch structure, landscape change in Fukang transect. We selected several landscape metrics, such as landscape diversity metrics, edge index, fractal dimension, evenness index, contagion index and so on. The results show that the relationship and feedback among the structure, function and process of oasis-desert ecosystem is real essence of landscape heterogeneity. Anthropogenic activities (e.g. development, over-grazing, timber harvest) can disrupt the structural integrity of oasis-desert landscapes and is expected to impede diversity communities across the landscape and make it fragmented. With human dimension and activities enhancing, the patchiness grain, edge density and landscape contrast become large, landscape diversity and patch fractal dimension decreased. The mutation, contrast and heterogeneity of ecological interface between oasis and desert ecosystem increased. Rare natural or non-regional mosaic of patch show obvious sensitivity to spatial scale, the change ratios of theirs area and perimeter are greater than large patch.Fractional vegetation cover data (FVC) based on the annual maximum NOAA/AVHRR NDVI (Advanced Very High Resolution Radiometer normalized difference vegetation index) data and the ground meteorological data have been used to analyze the relationship between the temporal and spatial evolution of ecological landscape pattern and climate change in Xinjiang autonomous region, China from 1982 to 2000. It is found that during this period, the averaged oasis cropland or low-damp forest-shrub meadow area occupies 7.50% of the whole region, desert dune/barren desert 25.70% ; temperate semi-arbor desert 21.70% ; temperate shrub and semi-shrub desert 8.36% ; alpine subalpine desert steppe 7.71% ; temperate gramineous and ruderal steppe 7.63% ; mountainOasis-desert Landscape Heterogeneityforest steppe 2.13% ; high-cold barren 8.93% ; high-cold low semi-shrub desert 9.08% ; water/ice 1.26%. Compared with the 30-year (1961-1990) climatology, the 12-year averaged annual surface air temperature and precipitation over the whole region increase by 0.44 癈 and 23.6 mm respectively, annual surface air temperature and precipitation over the whole region increase by 0.28 癈 and 14.5 mm respectively from 1982 to 2000. The maximum increase of precipitation does not occur over the mountain region ; instead it occurs over the region with a concentrated distribution of oases, suggesting the positive role of oases in adjusting regional climate. The area of temporal steppe also increases with the increase of precipitation and temperature. Together, these results demonstrate that, during the 20-year period, the condition of vegetation cover has been improved and large-scale desertification does not occur in Xinjiang.At 8km resolution of FVC (Fractional vegetation cover)/NOAA data, the matrix classes that greatly related to the topography of Tian Shan Mountains were detected. NOAA 8km model is good for the annual monitoring of each landscape unit, and regeneration planning at the regional level. Mountain-Desert-Oasis landscape structure within Xinjiang, arid region of northwestern China, is the basic focus of this study concerning land-use planning for sustainable vegetation restoration and climate change study

Mots clés : Oasis-Desert, Landscape, Ecosystem, Heterogeneity, Response, Climate Change, Patch

Présentation (Dissertationtopic )

Page publiée le 19 avril 2013, mise à jour le 14 septembre 2017