Xiao Du-ning

Temporal and spatial dynamical simulation of groundwater characteristics in Minqin Oasis

Application scope of geostatistics has been gradually extended from original geologic field to soil science and ecological field, etc. and its successful application results have been widely demonstrated. But little information is reported as to the direct use of geostatistical method to work out the distribution map of groundwater characteristics. In this paper the semivariogram of geostatistics, in combination with GIS, was used to quantitatively study the spatial variation characteristics of groundwater table depth and mineralization degree and their relation to the landuse changes. F test of the used spherical model reached a very significant level, and the theoretical model can well reflect the spatial structural characteristics of groundwater table depth and mineralization degree and achieve an ideal result. This shows that the application of the method in the dynamical simulation of groundwater is feasible. And this paper also provides useful reference for the application of geostatistics in the study of the dynamical variations of groundwater resources in the oasis.

Hydrological Effects of Forest Landscape Patterns in the Qilian Mountains A Case Study of Two Catchments in Northwest China

Abstract The relationship between vegetation and water budgets in mountain catchments has been the subject of intense debate from an ecological as well as a hydrological point of view. In the present article, we evaluate forest landscape patterns and their hydrological effects on the Qilian Mountains of northwest China, using GIS and 15 years (1987 to 2001) of hydrological databases to illustrate the cases of 2 catchments, Dayekou (DYK) and Haichaoba (HCB). Landsat ETM+ remote sensing satellite data (1:50,000) taken in May 2001 and topographic maps (1:50,000) were used to produce the landscape maps. The results showed that the main landscape elements affecting hydrological processes were grassland and Picea crassifolia forest in the lower areas in DYK, while the main landscape elements affecting hydrological processes in the higher areas in HCB were shrub-land and barren land. Observations over many years indicate that the water retention capacity of Picea crassifolia forest makes it the best of all vegetation types for hydrological purposes in the area. In DYK, evapotranspiration was 61%, and runoff was 39% of rainfall, whereas in HCB, evapotranspiration was 41%, and runoff was 59% of rainfall. However, dry season runoff in DYK (25.2%) was higher than in HCB (17.7%). Our results show that the various forest landscapes cause different hydrological processes in arid mountain areas in northwest China.

Corridor effect of the spatial changes of landscape patterns in arid areas: A case study of the river corridor areas in the middle and lower reaches of Tarim River

The river corridor areas in the middle and lower reaches of the Tarim River are dominated by the traditional green corridors along the river section from the Qara Reservoir in Yuli County to the Taitema Lake in Ruoqiang County, which plays an important role in the social and economic development in the Tarim River Watershed with a extremely significant ecological functions. The buffer zones perpendicular to the watercourse were defined along both riversides at a 5-km interval beginning from the watercourse (10 km wider) using the method of the buffer zone analysis. The landscape pattern indexes of each buffer zone were calculated, and the indexes of the main landscape patterns were analyzed so as to reveal the radiative effect and the characteristics of the river corridors on landscape and patch levels. The results show that the radiative width is generally 30 km in the study area, and can be up to 50–70 km in sub-region FG1 because the study area is located in two drainage basins, with an ecological interstitial zone between them. The landscapes of woodlands and wetlands are generally distributed within the 10 km buffer zone (it means that the buffer zone is 5 km away from the watercourse; the same hereafter) along both riversides. Moreover, the closer the buffer zone is to the watercourse, the higher the patch density and the largest patch index are. In the ecological and environmental regeneration for the study area, the extent of ecological effect of the river corridors must be fully considered, and the projects must be scientifically and rationally planned and designed.

Forest crown density restoration and influencing factors in the burned area of northern Great Hing′an Mountains of China

Abstract Fire in the Great Hing′an Mountains in 1987 affected an area of more than 1.33×106 hm2, creating a mosaic of burn severities across the landscape, which strongly affected the postfire vegetation succession. In addition, undulate landform and anthropogenic disturbance inevitably influenced the postfire vegetation succession. In this paper, a typical area was selected for a case study, including two forest farms, covering more than 1.2×105 hm2. In order to reveal how the forest changed in 2000 (13 years after the fire) by comparing with 1987 (prefire) and to find out the relationship between the forest succession and the affecting factors, forest crown density was selected as the criterion, and forest type, fire severity, silviculture practice, elevation and topography gradients were designed as the affecting variables. With the support of GIS software, each variable was classified and entered into the multivariate regression model. The result showed that the forest crown density changed notably in 2000 compared with that of the prefire, and all the variables significantly affected the forest crown density. The most important affecting variable was elevation, which was positively correlated with the forest crown density. The next was fire severity, which was negatively related with the forest succession. The effects of topographic factors and silviculture practices on forest crown density were relatively small.

Post-fire habitat restoration of sables during winter season in northern slope of the Great Xing′an Mountains

Habitat loss and fragmentation have been associated with the decline of endangered species. In 1987, a catastrophic fire in the northern Great Hing’an Mountains of China, where the main habitat of sables. (Martes zibellina) is located, aggravated the loss and fragmentation of the forest landscape. Due to restricted distribution and low population density, sables were listed in the national first-grade protected species in China. The objective of this paper was to identify to what extent the habitat of sables had been restored 13 years after the fire. Based on the behavioral data, which came from field survey information by radio-tracking, GPS (Global Positioning System) and forest inventory data, suitability habitat maps were derived using the Ecological Niche Suitability Model (ENSM). In addition, the habitat structure was analyzed with selected landscape indices. Although forest cover mostly had been restored by 2000, the results indicated that, compared to the pre-fire situation, the areas of suitable habitat had been reduced significantly, especially those of less suitable, marginally suitable and moderately suitable designation. Fragmentation was aggravated, and suitable patches were found to be further isolated with the exception of those in most suitable areas. The ratio of the patch perimeter to area in unsuitable, moderately suitable and suitable areas decreased, while the ratios within other suitability types increased. Moreover, the percentage of soft boundaries decreased slightly, which can influence the redistribution of sables. The results above indicated that the suitable habitat had deteriorated, and the restoration of the sables’ habitat remained to be done.

Ecological security pattern analysis of Jiuquan oasis using remote sensing and GIS

Ecological degradation has taken place in many arid regions, north-west China, especially in oases. The heterogeneous oasis is the soul and the most sensitivity part of the arid regions, so it is important to pay attention to the ecological security of oasis. The aim of this study is to analyze the ecological security pattern from the aspect of spatial neighboring characteristics between the sand land/the salinized land and the various oasis patch types, taking the Jiuquan oasis as an example. Remote sensing and GIS were used to analyze ecological security pattern. Main data included Landsat 5 TM image in 1986, Landsat 7 ETM+ image in 2000 and topographic maps. Landscape maps of Jiuquan oasis were compiled based on the above data, then sand land and salinized land threats against oasis patch types were calculated. The results showed that: 1) in 1986, the order of the sand land threat was Cfarm land>Cgrass land>Cwoodland>Cwater area>Cresidential area; in 2000, except the threat against residential area, the threat against the other oasis patch types increased, and the value of Cgrass land became the biggest, followed by Cwoodland> Cfarm land> Cwater area>Cresidential area; 2) in 1986, the order of the salinized land threat was Cgrass land>Cwoodland>Cfarm land>Cwater area>Cresidential area, and there was a decline in the salinized land threat against all oasis patch types in 2000, the order became Cgrass land>Cfarm land>Cwater area >Cwoodland >Cresidential area; 3) as to the total oasis, there was an increasing of 73.9% in sandy desertification threat, while there was a decreasing of 39% in salinization threat from 1986 to 2000.

Literature analysis and research progress of the landscape ecology in China in the 1990s

This paper makes analysis of published articles and books on landscape ecology in the 1990s through literature collection. The analytical results showed that the study of landscape ecology had made a great advance during the past decade in China. By incomplete survey, Chinese researchers at home and abroad published 619 scientific articles and 13 monographs on landscape ecology in the 1990s, and most of them (more than 90%) were published in Chinese with English abstracts. The published articles on basic theory accounted for 39.6% (245 articles), and those concerning application and methods accounted for 36.8% (228) and 23.6% (146), respectively. According to the objects of research, the published articles on landscape ecology were classified into nine catalogues. The urban landscape ranks first in terms of number of published articles, accounting for 13.4% of the total, followed by regional and river basin landscape, cold and arid landscape, forest landscape, habitat and bio-diversity landscape, agricultural landscape, wetlands, suburban landscape, and vegetation landscape. Based on the analysis, some discussions were made on the existing problems and development trend of landscape ecology study in China.

Spatial pattern and function of corridors in wetlands of Liaohe delta

Corridors are special patches with narrow and long shape, and often have the functions as transportation, protection, resources and aesthetics. Corridors in the study area can be classified into 8 types, with a total length of 5167.2 km, and corridor density of 1.25 km/km2. The corridors are mainly composed of irrigation and drainage canals, the total length of which is 2794 km, about 54.1% of all the corridors. The corridors have segmented the landscape, and changed the original situation of the natural landscapes. The types of corridors are closely related to the landscape types they are distributed in. Canals are mainly distributed in the wetland landscapes, while roads are mainly in the buil-up area. Dikes are always along rivers or coastlines. The corridors are most densely distributed wherever human activity occurs most frequently, such as in the artificial wetlands of paddy fields.

Landscape pattern changes in west suburbs of Shenyang

Spatial pattern of landscape is a central issue in landscape ecology study. The main reason of landscape patten change owes to the external disturbance. In this article, retrospective sequential airphotoanalysis and statistical analysis of information on landscape development were used and two remarkable changes of landscape pattern in west Shenyang were identified: (a) one landscape element becomes a new matrix in place of the former one; (b) landscape proportions among several constiting elements changed significantly. This paper studied spatial pattern of the landscape using following quanta indices: (1) number and size of patches, (2) transition matrix of patches, (3) priority index of each kind of patch and (4) diversity and evenness indices of landscape. The results show that the landscape of west Shenyang has been more and more disturbed by human activities, so it becomes fragmentary throughout 30 years, and many blocky and island-like patches emerged.

The effects of the mountain forest changes on hydrology in Northwest Arid China

The research on the relationship between vegetation and water budgets in mountainous area occupies an important niche either in hydrology or ecology. Based on GIS, using 15 years’ (from 1987 to 2001) hydrological databases and forest investigation databases, we evaluated the hydrological effects of forest changes in the Qilian Mountains of northwest arid China with the cases of two catchments (DYK and HCB). In this paper, Landsat ETM remote sensing satellite data (1 : 50000) taken in May 2001, forest map (1 : 50000) and topographic map (1 : 50000) were used to produce the forest landscape map. The forest spatial pattern and area had changed very little in the two catchments, and the main changes were the forest growing stock during the 10 years (from 1989 to 2001). The growing stock increased 50926m in DYK and 34282m in HCB. The result of analyzing the forest change and hydrological databases indicated that, from 1989 to 2001, with a certain forest area in the two catchments, the runoff modulus and the dry season runoff percentage increased with the forest growing stock increasing. Runoff modulus increased 5.41mm per 10000m forest growing stock in DYK and 5.7mm in HCB. The mean dry season runoff percentage of DYK was 10.14% during 1989 to 1995 and 11.9% during 1996 to 2002, and which was separately 7.23% and 8.48% in HCB, which means the forest growing in the catchments should improve its hydrology adjusting function especially in arid mountains. Keywordsforest changes, hydrological effects, Qilian Mountains, northwest arid China