Temporal and Spatial Variations in the Leaf Area Index and Its Response to Topography in the Three-River Source Region, China from 2000 to 2017
The Three-River Source Region (TRSR) is an important area for the ecological security of China. Vegetation growth has been affected by the climate change, topography, and human activities in this area. However, few studies have focused on analyzing time series tendencies of vegetation change in vari...
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MDPI AG
2021-01-01
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| Series: | ISPRS International Journal of Geo-Information |
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| Online Access: | https://www.mdpi.com/2220-9964/10/1/33 |
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| author | Wenqi Zhang Huaan Jin Huaiyong Shao Ainong Li Shangzhi Li Wenjie Fan |
| author_facet | Wenqi Zhang Huaan Jin Huaiyong Shao Ainong Li Shangzhi Li Wenjie Fan |
| author_sort | Wenqi Zhang |
| collection | DOAJ |
| description | The Three-River Source Region (TRSR) is an important area for the ecological security of China. Vegetation growth has been affected by the climate change, topography, and human activities in this area. However, few studies have focused on analyzing time series tendencies of vegetation change in various terrain conditions. To address this issue in the TRSR, this study explored vegetation stability, tendency, and sustainability with multiple methods (e.g., coefficient of variation, Theil-Sen median trend analysis, Mann-Kendall test, and Hurst index) based on the 2000–2017 Global LAnd Surface Satellite Leaf Area Index (GLASS LAI) product. The differentiation patterns of LAI variations and multiyear mean LAI value under different topographic factors were also investigated in combination with digital elevation model (DEM). The results showed that (1) the mean LAI value in the study area increased, with a linear tendency of 0.013·10 a<sup>−1</sup>; (2) LAI values decreased from southeast to northwest in terms of spatial distribution and the CV indicated LAI variations were relatively stable; (3) the trend analysis revealed that the improved area of LAI accounted for 62.72% which was larger than the degraded area (37.28%), and hurst index revealed a weak anti-sustaining effect of the current tendencies; and (4) the increasing trend was found in multiyear mean LAI value as relief amplitude and slope increased, while LAI stability improved with increasing slope. They exhibited a clear regular pattern. Moreover, significant improvement in LAI generally occurred in low-altitude and flat areas. Finally, the overall improvement and sustainability of LAI improved when moving from sunny aspects to shady aspects, but the LAI stability decreased. Note that vegetation degradation was observed in some high slope areas and was further aggravated. This study is beneficial for revealing the spatial and temporal changes of LAI and their changing rules as a function of different topographic factors in the TRSR. Meanwhile, the results of this study provide theoretical support for sustainable development of this area. |
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| language | English |
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| spelling | doaj.art-c665e70b2c6c41a6822fcaeb9f7bfa272023-12-03T13:09:00ZengMDPI AGISPRS International Journal of Geo-Information2220-99642021-01-011013310.3390/ijgi10010033Temporal and Spatial Variations in the Leaf Area Index and Its Response to Topography in the Three-River Source Region, China from 2000 to 2017Wenqi Zhang0Huaan Jin1Huaiyong Shao2Ainong Li3Shangzhi Li4Wenjie Fan5College of Earth Science, Chengdu University of Technology, Chengdu 610059, ChinaResearch Center for Digital Mountain and Remote Sensing Application, Institute of Mountain Hazards and Environment, CAS, Chengdu 610041, ChinaCollege of Earth Science, Chengdu University of Technology, Chengdu 610059, ChinaResearch Center for Digital Mountain and Remote Sensing Application, Institute of Mountain Hazards and Environment, CAS, Chengdu 610041, ChinaSchool of Surveying and Land Information Engineering, Henan Polytechnic University, Jiaozuo 454000, ChinaCollege of Earth Science, Chengdu University of Technology, Chengdu 610059, ChinaThe Three-River Source Region (TRSR) is an important area for the ecological security of China. Vegetation growth has been affected by the climate change, topography, and human activities in this area. However, few studies have focused on analyzing time series tendencies of vegetation change in various terrain conditions. To address this issue in the TRSR, this study explored vegetation stability, tendency, and sustainability with multiple methods (e.g., coefficient of variation, Theil-Sen median trend analysis, Mann-Kendall test, and Hurst index) based on the 2000–2017 Global LAnd Surface Satellite Leaf Area Index (GLASS LAI) product. The differentiation patterns of LAI variations and multiyear mean LAI value under different topographic factors were also investigated in combination with digital elevation model (DEM). The results showed that (1) the mean LAI value in the study area increased, with a linear tendency of 0.013·10 a<sup>−1</sup>; (2) LAI values decreased from southeast to northwest in terms of spatial distribution and the CV indicated LAI variations were relatively stable; (3) the trend analysis revealed that the improved area of LAI accounted for 62.72% which was larger than the degraded area (37.28%), and hurst index revealed a weak anti-sustaining effect of the current tendencies; and (4) the increasing trend was found in multiyear mean LAI value as relief amplitude and slope increased, while LAI stability improved with increasing slope. They exhibited a clear regular pattern. Moreover, significant improvement in LAI generally occurred in low-altitude and flat areas. Finally, the overall improvement and sustainability of LAI improved when moving from sunny aspects to shady aspects, but the LAI stability decreased. Note that vegetation degradation was observed in some high slope areas and was further aggravated. This study is beneficial for revealing the spatial and temporal changes of LAI and their changing rules as a function of different topographic factors in the TRSR. Meanwhile, the results of this study provide theoretical support for sustainable development of this area.https://www.mdpi.com/2220-9964/10/1/33Three-River Source Regionleaf area indexvegetation changestopographic effect |
| spellingShingle | Wenqi Zhang Huaan Jin Huaiyong Shao Ainong Li Shangzhi Li Wenjie Fan Temporal and Spatial Variations in the Leaf Area Index and Its Response to Topography in the Three-River Source Region, China from 2000 to 2017 ISPRS International Journal of Geo-Information Three-River Source Region leaf area index vegetation changes topographic effect |
| title | Temporal and Spatial Variations in the Leaf Area Index and Its Response to Topography in the Three-River Source Region, China from 2000 to 2017 |
| title_full | Temporal and Spatial Variations in the Leaf Area Index and Its Response to Topography in the Three-River Source Region, China from 2000 to 2017 |
| title_fullStr | Temporal and Spatial Variations in the Leaf Area Index and Its Response to Topography in the Three-River Source Region, China from 2000 to 2017 |
| title_full_unstemmed | Temporal and Spatial Variations in the Leaf Area Index and Its Response to Topography in the Three-River Source Region, China from 2000 to 2017 |
| title_short | Temporal and Spatial Variations in the Leaf Area Index and Its Response to Topography in the Three-River Source Region, China from 2000 to 2017 |
| title_sort | temporal and spatial variations in the leaf area index and its response to topography in the three river source region china from 2000 to 2017 |
| topic | Three-River Source Region leaf area index vegetation changes topographic effect |
| url | https://www.mdpi.com/2220-9964/10/1/33 |
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