Browsing by Author "Liu, Yanxu"

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    Applying ant colony algorithm to identify ecological security patterns in megacities
    (Elsevier, 2019-03-20) Peng, Jian; Zhao, Shiquan; Dong, Jianquan; Liu, Yanxu; Meersmans, Jeroen; Li, Huilei; Wu, Jiansheng
    Ecological security patterns composed of ecological sources and corridors provide an effective approach to conserving natural ecosystems. Although the direction of ecological corridors has been identified in previous studies, the precise range remains unknown. To address this crucial gap, ant colony algorithm and kernel density estimation were applied to identify the range and restoration points of ecological corridors, which is important for natural conservation and ecological restoration. In this case study of Beijing City, ecological sources were identified based on habitat importance and landscape connectivity. The results showed that, in total 3119.65 km2 of ecological land had been extracted as ecological sources, which were mainly located in the northern, northwestern and northeastern mountainous areas. The identified key ecological corridor covered an area of 198.86 km2, with 567.30 km2 for potential ecological corridors, both connecting the ecological sources. 34 key points were also identified with priority in restoring ecological corridors.
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    Integrating spatial continuous wavelet transform and normalized difference vegetation index to map the agro-pastoral transitional zone in Northern China
    (MDPI, 2018-11-30) Han, Yinan; Peng, Jian; Meersmans, Jeroen; Liu, Yanxu; Zhao, Zhiqiang; Mao, Qi
    The agro-pastoral transitional zone (APTZ) in Northern China is one of the most important ecological barriers of the world. The commonly-used method to identify the spatial distribution of ATPZ is to apply a threshold rule on climatic or land use indicators. This approach is highly subjective, and the quantity standards vary among the studies. In this study, we adopted the spatial continuous wavelet transform (SCWT) technique to detect the spatial fluctuation in normalized difference vegetation index (NDVI) sequences, and as such identify the APTZ. To carry out this analysis, the Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI 1-month data (MODND1M) covering the period 2006–2015 were used. Based on the spatial variation in NDVI, we identified two sub-regions within the APTZ. The temporal change of APTZ showed that although vegetation spatial pattern changed annually, certain areas appeared to be stable, while others showed higher sensitivity to environmental variance. Through correlation analysis between the dynamics of APTZ and precipitation, we found that the mean center of the APTZ moved toward the southeast during dry years and toward the northwest during humid years. By comparing the APTZ spatial pattern obtained in the present study with the outcome following the traditional approach based on mean annual precipitation data, it can be concluded that our study provides a reliable basis to advance the methodological framework to identify accurately transitional zones. The identification framework is of high importance to support decision-making in land use management in Northern China as well as other similar regions around the world.
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    Linking ecosystem services and circuit theory to identify ecological security patterns
    (Elsevier, 2018-07-11) Peng, Jian; Yang, Yang; Liu, Yanxu; Hu, Yi'na; Du, Yueyue; Meersmans, Jeroen; Qiu, Sijing
    The rapid process of urbanization, accompanied by the sharp increase of urban population and expansion of artificial surface, has resulted in the loss of natural ecosystems and the degradation of ecosystem services. Identifying and protecting key places that have high importance for ecological sustainability are great challenges. Ecological security patterns are such an integrated approach to protecting regional ecological sustainability. In this study, taking Yunnan Province, China as a case study area, ecological sources were identified through ecosystem services, and circuit theory was used to model ecosystem processes in heterogeneous landscapes via calculating the ‘resistance’ or ‘current’, and thus to identify ecological corridors and key ecological nodes. The results showed that, ecological security patterns included 66 ecological sources, 186 ecological corridors, 24 pinch-points and 10 barriers. In details, the ecological sources were mainly distributed in the southwest and northwest of Yunnan Province, with the ecological corridors locating along the high mountains, and both ecological sources and corridors were mostly covered with forest land. Pinch-points covered by forest land and cultivated land, were distributed in the middle of Yunnan Province along the rivers. Approximately 75.9% nature reserves were located in the identified ecological sources, and the remainings were mainly distributed in eastern Yunnan Province with small area, showing the effectiveness in identifying ecological security patterns. Among 81 projects of low–slope hill development carried out in Yunnan Province, 46.9% showed potential human stress on regional ecological security. Based on ecosystem services and circuit theory, this study provides a new approach to identifying the spatial range of ecological corridors and the specific location of key nodes for effective ecological conservation and restoration.
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    Multifunctional landscapes identification and associated development zoning in mountainous area
    (Elsevier, 2019-01-04) Peng, Jian; Hui, Xiaoxu; Qiu, Sijing; Hu, Yi'na; Meersmans, Jeroen; Liu, Yanxu
    Multifunctional landscape has become a new discipline growth point in landscape ecology. Globally mountainous areas occupy about one fifth of Earth's surface. However, few studies focused on landscape multifunctionality in mountainous areas. Taking Dali Bai Autonomous Prefecture, China, as a case study area, five typical landscape functions (net primary productivity, soil retention, water yield, crop production, and residential support) were quantified and mapped. Hotspots of multiple landscape functions were identified using spatial overlap tools, interaction between each landscape function pair was discussed through Spearman's rank correlation analysis, and development zoning was conducted based on landscape function bundle. The results showed that, about 61% of the study area had at least one kind of landscape function hotspot, with only 2.7% covering three or more kinds of landscape function hotspots. Significant trade-offs or synergies existed between all pairs of landscape functions, except the pair of net primary productivity and residential support. With the application of Self-Organizing Feature Maps (SOFM) method, the study area was divided into four types of development zones (i.e. ecological shelter area, ecological transition area, suburban development area, and urban agglomeration area) which were all corresponding to different landscape function bundles. This study could provide spatial guidance for differentiated sustainable developing in mountainous areas according to local conditions of landscape multifunctionality.
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    Simulating the impact of Grain-for-Green Programme on ecosystem services trade-offs in Northwestern Yunnan, China
    (Elsevier, 2019-09-01) Peng, Jian; Hu, Xiaoxu; Wang, Xiaoyu; Meersmans, Jeroen; Liu, Yanxu; Qiu, Sijing
    Prefecture in 2000, land use/cover has undergone dramatic changes. This study used the CLUE-S model to simulate land use change in 2030, and explored the spatial pattern and relationship of different ecosystem services under the four scenarios of GFGP. The results show that, GFGP can help to improve indirect services of ecosystems, such as carbon storage and soil conservation. However, direct services of the ecosystem will decline, such as food production and water yield. Compared with 2010, the overall supply level of the four ecosystem services is the most balanced in the moderate GFGP scenario. In this scenario, total food production decreased by 179,000 tons and water yield decreased by 57 million cubic meters. Carbon storage and soil conservation continued to grow, increasing by 21.86 million tons and 17.87 million tons, respectively. The changes of ecosystem services in the strong GFGP scenario are extreme. The increases in carbon storage and soil conservation are at the expense of a significant reduction in food production and water yield. It can be concluded that GFGP may lead to intensifying ecosystem services trade-offs. Through comparing the changes of ecosystem services under different GFGP scenarios, it is found that the implementation intensity of GFGP should be deeply concerned in policy making.
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    Spatial identification of conservation priority areas for urban ecological land: An approach based on water ecosystem services
    (Wiley, 2019-01-09) Peng, Jian; Wang, An; Luo, Lingwei; Liu, Yanxu; Li, Huilei; Hu, Yi'na; Meersmans, Jeroen; Wu, Jiansheng
    How to effectively prevent land degradation and ecosystem deterioration in the process of urbanization has been the focus of land degradation researches in urban areas. Urban ecological land can be defined as the natural base on which a city relies to ecologically survive. It closely links the social economy with the natural eco‐environment, providing an important integrated approach to resolve the contradiction between urban expansion and natural ecosystems conservation in the process of urbanization. The research question addressed in this study is how to accurately identify the conservation priority areas for urban ecological land. Taking Zhuhai City, located in China, as an example, an approach based on seven kinds of water ecosystem services was put forward, combining social demand and natural supply for the services to determine service targets and conservation priority areas. The results showed that the conservation priority areas in Zhuhai City covered 868 km2, accounting for 51.03% of the total land area, which were mainly covered by woodlands or paddy fields and fish ponds. In addition, by synthesizing ecological importance and ecological sensitivity, management zones for urban ecological land were delineated, including 510 km2 of primary control areas and 358 km2 of secondary control areas. In the supply and demand view of water ecosystem services, this study put forward an integrated ecosystem‐based approach for conservation priority area identification of urban ecological land, aiming to prevent land degradation and achieve urban ecological sustainability.