| As one of the main body of terrestrial ecosystem, wetland is significant to maintain the balance of ecosystem. Because of the influence of nature and human activities. The wetland was become more and more fragmentation while the area of wetland was reduced rapidly. An obvious decrease in biodiversity and degradation of wetland ecosystem was turn up. As a result the Badan Jilin desert is moving to the south which will threaten the survival and development of the Heihe basin. The ecosystem safety of the whole Hexi Corridor and the whole of northwest were in danger. The analysis of wetland fragmentation processes and driving factors could improve the understanding of wetland fragmentation which was important for the protection of the wetland and oasis sustainable development in Hexi Corridor. On the other hand this study was a typical case of wetland fragmentation in arid region.Based on remote sensing and GIS, the type change tracker model will be constructed with sliding window technique and spatially morphological rule in this study. The suitable scale and optimum scale of the fragmentation model of wetland landscape in the middle reaches of Heihe River will be determined by area frequency statistics method, Chi-square distribution normalized scale variance, fractal dimension and diversity index. By integrating type change tracker model and the optimum scale with GIS spatial analysis, the fragmentation spatial distribution characteristics of the different periods and spatial-temporal dynamics change process of wetland fragmentation will be clarified. Then the redundancy analysis and principal component analysis were chose to identify the driving factors of wetland fragmentation. The accuracy of the driving factors was verified by CLUE-S model. The future pattern of wetland fragmentation under different scenario were predicted by this model. The main research contents and results are as follows:(1) Traditional method such as area frequency statistics, fractal dimension and diversity index integrating with the Chi-square distribution normalized scale variance, performed well in the scale analysis of the wetland fragmentation in the arid inland river. The suitable scale for the type change tracker model was 150 m×150 m – 450 m×450 m, and the optimum scale was 250 m×250 m in the middle reaches of Heihe River.(2) The wetland area decreased by 23.19%(7570.27 hm2), during 1975- 2010, while the wetland become more fragmentation. The core wetland decreased from 32.55% to 18.80%, edge wetland increased from 36.86% to 39.95%, perforated wetland increased from 36.86% to 39.95% and patch wetland increased from 24.355 to 33.21%. The fragmentation process in the research region is core wetlandâ†' perforated or edge wetlandâ†' patch wetland or non-wetland. The research of wetland conversion between different fragmentation types not only enriched the research content, but also laid the foundation for further analysis of the driving mechanism.(3) 3 natural driving factors and 9 anthropogenetic driving factors were selected for the redundancy analysis. Combing with the existed study these 12 driving factors were the driving factors of wetland fragmentation in the middle reaches of Heihe River. Principle component analysis was used to unweil the main factors of wetland fragmentation. The cumulative contribution of first five main components has reached 75.3801% that means it was credible. The wetland fragmentation process was not only influenced by artificial factors but also affected by nature factors. Actually, artificial factors are the mian reasons for wetland fragmentation.(4) The accuracy of the simulation by the CLUE-S was 0.6424 which mean that the factors we chose do well in the simulation. In other words the chose of factors was reasonable. The future pattern of wetland fragmentation under different scenario were predicted by this model. A further wetland fragmentation mechanism model should be established to interpretation the driving mechanism of wetland fragmentation. |
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