Alishir Kurban

Trajectory analysis of land cover change in arid environment of China

Remotely sensed data have been utilized for environmental change study over the past 30 years. Large collections of remote sensing imagery have made it possible for spatio‐temporal analyses of the environment and the impact of human activities. This research attempts to develop both conceptual framework and methodological implementation for land cover change detection based on medium and high spatial resolution imagery and temporal trajectory analysis. Multi‐temporal and multi‐scale remotely sensed data have been integrated from various sources with a monitoring time frame of 30 years, including historical and state‐of‐the‐art high‐resolution satellite imagery. Based on this, spatio‐temporal patterns of environmental change, which is largely represented by changes in land cover (e.g., vegetation and water), were analysed for the given timeframe. Multi‐scale and multi‐temporal remotely sensed data, including Landsat MSS, TM, ETM and SPOT HRV, were used to detect changes in land cover in the past 30 years in Tarim River, Xinjiang, China. The study shows that by using the auto‐classification approach an overall accuracy of 85–90% with a Kappa coefficient of 0.66–0.78 was achieved for the classification of individual images. The temporal trajectory of land‐use change was established and its spatial pattern was analysed to gain a better understanding of the human impact on the fragile ecosystem of Chinas arid environment.

Spatial pattern analysis of land cover change trajectories in Tarim Basin, northwest China

This study attempts to develop a methodology to quantify spatial patterns of land cover change using landscape metrics. First, multitemporal land cover types are derived based on a unified land cover classification scheme and from the classification of multitemporal remotely sensed imagery. Categorical land cover change trajectories are then established and reclassified according to the nature and driving forces of the change. Finally, spatial pattern metrics of the land cover change trajectory classes are computed and their relationships to human activities and environmental factors are analysed. A case study in the middle reach of Tarim River in the arid zone of China from 1973 to 2000 shows that during the 30‐year study period, the natural force is dominant in environmental change, although the human impact through altering water resources and surface materials has increased dramatically in recent years. The human‐induced change trajectories generally show lower normalized landscape shape index (NLSI), interspersion and juxtaposition index (IJI) and area‐weighted mean patch fractal dimension (FARC_AM), indicating greater aggregation, less association with others and simpler and larger patches in shape, respectively. The results suggest that spatial pattern metrics of land cover change trajectories can provide a good quantitative measurement for better understanding of the spatio‐temporal pattern of land cover change due to different causes.

Glacier characteristics and changes in the Sary-Jaz River Basin (Central Tien Shan, Kyrgyzstan) – 1990–2010

The water discharge from the heavily glacierized Sary-Jaz River Basin (Eastern Kyrgyzstan) is of high importance for the very arid Tarim Basin located in Xinjiang (north-western China). We investigated glacier changes in the entire Sary-Jaz River Basin, which covers a large part of the Central Tien Shan, for the period from 1990 to 2010 based on Landsat ‘TM’/‘ETM+’data. We found 1310 glaciers (>0.1 km2), which covered 2055 ± 41.1 km2 (∼18% of the entire basin) in 1990. The glaciers shrank by 77.1 ± 57.1 km2 (3.7 ± 2.7%) until 2010. This is considerably lower than in most other ranges of the Tien Shan. The lowest insignificant area loss (−1.5 ± 2.7%) was found in the eastern part of the basin where the largest glaciers and highest peaks are situated. Debris-covered glaciers shrank significantly less than clean-ice glaciers of comparable size. We also identified a few advancing glaciers which show surge characteristics. Climate data from the Tien Shan weather station (3614 m asl.) close to the study region showed no significant long-term trend.

Eco-morphological response of floodplain forests ( Populus euphratica Oliv.) to water diversion in the lower Tarim River, northwest China

Abstract The Tarim River is about 1,320xa0km long and is one of the longest continental inland waterways in the world. In an undisturbed state, it is accompanied on both sides by floodplain forests of Euphrates poplar (Populus euphratica Oliv.). The rising water consumption in the upper and middle reaches, and massive hydro-technical interventions in the development of uncultivated land for cotton farming, especially during the last decades, have led to a widespread destruction of the natural ecosystems. This is the case particularly in the lower reaches of the river, where 320xa0km of the floodplain forests are either highly degraded or dead. Since the year 2000, the Chinese government has made efforts to restore these ecosystems and conducted man-made water diversion project into the affected area. The starting phase of recovering measures needs an efficient and extensive long-term monitoring. A combined approach of remote sensing and terrestrial samples can meet these demands. This study is based on the data from a small-scale ecological monitoring in the past 7xa0years and combination of QuickBird image information of the floodplain forests along the lower reaches of the Tarim River within the purview of the man-made restoration project. The effects of the artificial water diversion on the dynamics of the groundwater layer and the revitalization of P. euphratica floodplain forests have been analysed in the Arghan transect. The results showed that the groundwater level has risen from 12.6 to 5.5–6.2xa0m below the surface in the vicinity of the river beds. Some eco-morphological parameters of the P. euphratica trees have different levels of response to the ecological water diversion. To specify, in the vertical direction, the farther the trees are from the river, the weaker the response of ecological indicators. These parameters include tree vitality level, crown diameter, under branch height as well as newly developed crown types of P. euphratica trees. Generally, the floodplain forests within 200xa0m to the riverbed recovered remarkably, and those between 200 and 800xa0m from the river showed a medium response to the water transfer, while forests further away than 800xa0m from the river bed showed less sign of recovery.

Object based change detection of Central Asian Tugai vegetation with very high spatial resolution satellite imagery

Abstract Ecological restoration of degraded riparian Tugai forests in north-western China is a key driver to combat desertification in this region. Recent restoration efforts attempt to recover the forest along with its most dominant tree species, Populus euphratica. The present research observed the response of natural vegetation using an object based change detection method on QuickBird (2005) and WorldView2 (2011) data. We applied the region growing approach to derived Normalized Difference Vegetation Index (NDVI) values in order to identify single P. euphratica trees, delineate tree crown areas and quantify crown diameter changes. Results were compared to 59 reference trees. The findings confirmed a positive tree crown growth and suggest a crown diameter increase of 1.14xa0m, on average. On a single tree basis, tree crown diameters of larger crowns were generally underestimated. Small crowns were slightly underestimated in QuickBird and overestimated in Worldview2 images. The results of the automated tree crown delineation show a moderate relation to field reference data with R 2005 2 : 0.36 and R 2011 2 : 0.48. The object based image analysis (OBIA) method proved to be applicable in sparse riparian Tugai forests and showed great suitability to evaluate ecological restoration efforts in an endangered ecosystem.

Desert riparian forest colonization in the lower reaches of Tarim River based on remote sensing analysis

The ecological water conveyance project that pipes water from Daxihaizi reservoir to lower reaches of Tarim River has been implemented ten times since 2000. After ecological water conveyance, restoration has taken place for vegetation along the dried-up lower reaches of the Tarim River. The changes of vegetation fluctuated yearly due to ecological water conveyance. In order to reveal the detailed process of vegetation changes, remote sensing images from 1999 to 2010 were all classified individually into vegetated and non-vegetated areas using the soil-adjusted vegetation index threshold method. Then inter-annual changes of vegetation over a period of 12xa0years were obtained using a post-classification change detection technique. Finally, spatial–temporal changes distribution of vegetation cover and its response to ecological water conveyance were analyzed. The results indicate: (1) vegetation area increased by 8.52xa0% overall after ecological water conveyance. Vegetation between 2003 and 2004 increased dramatically with 45.87xa0% while vegetation between 2002 and 2003 decreased dramatically with 17.83xa0%. (2) Vegetation area gain is greater than vegetation loss during 1999–2000, 2001–2002, 2003–2004 and 2009–2010 periods. Although vegetation restoration is obvious from 1999 to 2010, vegetation loss also existed except for the periods above. It indicates that vegetation restoration fluctuated due to ecological water conveyance. (3) Spatial distribution of vegetation restoration presented “strip” distribution along the river and group shaper in the lower terrain area, while spatial distribution of vegetation loss mainly located in the upper reaches of river and area far away from the river. (4) Vegetation restoration area had a positive relative with total ecological water conveyance volume. The scheme and season of ecological water conveyance had also influenced the vegetation restoration. The vegetation change process monitoring, based on continuous remote sensing data, can provide the spatial–temporal distribution of vegetation cover in a large-scale area and scientific evidences for implementing ecological water conveyance in the lower Tarim River.

Spatiotemporal dynamics of land cover and their impacts on potential dust source regions in the Tarim Basin, NW China

AbstractnHuman-driven dynamics of land cover types in the Tarim Basin are able to affect potential dust source regions and provide particles for dust storms. Analyses about dynamics of potential dust source regions are useful for understanding the effects of human activities on the fragile ecosystem in the extremely arid zone and also provide scientific evidence for the rational land development in the future. This paper therefore selected the Tarim Basin, NW China, as a representative study area to reveal spatiotemporal dynamics of land cover and their impacts on potential dust source regions. The results showed that farmland, desert and forest increased by 28.63, 0.64 and 29.27%, while grassland decreased by 10.29% during 1990–2010. The largest reclamation, grassland loss and desertification were 639.17xa0×xa0103, 2350.42xa0×xa0103 and 1605.86xa0×xa0103xa0ha during 1995–2000. The relationship between reclamation and grassland loss was a positive correlation, while a highly positive correlation was 0.993 between the desertification and grassland loss at different stages. The most serious dust source region was the desertification during 1990–2010 (1614.58xa0thousand ha), and the serious region was stable desert (40,631.21xa0thousand ha). The area of the medium and low dust source region was 499.08xa0×xa0103 and 2667.27xa0×xa0103xa0ha. Dramatic reclamation resulted in the desertification by destroying natural vegetation and breaking the balance of water allocation in various regions.

Satellite sensor data analysis of urban surface temperatures and land use / land cover

With the rapid population growth, urbanization has become a common trend all over the world since the 20th Century. Meanwhile, urban air temperature is rising gradually in all the cities. In this paper, we took an oasis city—Urumqi as an example, investigated application of integration of remote sensing and geographic information systems (GIS) to detect the land use/cover change and urban growth, besides assessed their impacts on land surface temperature in this region. The results indicated as fellows: 1) during the last 20 years from 1990 to 2009, land use of Urumqi appeared a dramatic variation; 2) The mean annul temperatures of the land surface in Urumqi were 21.63°C and 25.39°C in 1990 and 2009, respectively. 3) According to the characteristics of the standard classification maps of land surface temperature and they revealed that the urban development had raised the land surface temperature of the urban. 4) Integration of remote sensing and GIS was an effective way to monitor and analyze urban growth pattern, and evaluate the urbanization impact on land surface temperature.

The impacts of urban landscape pattern on urban land surface temperature: —Taking Urumqi as an Example

Urbanization has become an important contributor for global warming and urban air temperature is rising gradually in all the cities. It means that urban land use and land cover (LULC) changed became critical in determining the urban environment quality. This paper presents an integrated study to investigate and identify landscape pattern which have the influence to increase of land surface temperature, using Geographical Information Systems (GIS) and remote sensing. In this paper, an oasis city-Urumqi as an example, which explores the temporal and spatial characteristics of land use and land cover change from 1990 to 2004, and the land surface temperature variation from 1990 to 2004. Results shows that land use of Urumqi appeared a dramatic variation during the last 15 years. The mean annul temperatures of the land surface in Urumqi were 21.41 °C in 1990 and 31.12 °C in 2004, respectively. In particular, the land surface temperature and landscape pattern index had shown the close relationship. To sum up, integration of remote sensing and GIS was an effective way to monitor and analyze urban LULC, and evaluate the landscape pattern impact on land surface temperature.