| 摘要: |
| 通过科学认识黄河植被覆盖的空间格局、时间规律，揭示气候变化与人类活动对植被覆盖率空间演化的影响与机理，对于提出科学的生态防护方法、进行生态安全评价，以及推进黄河战略有着重大的理论意义与应用意义。本文以1982—2015年GIMMS NDVI和2000—2021年MODIS NDVI为主要数据源，通过最大值合成法、平均值法、Theil-Sen Median和Mann-Kendall等方法分析了黄河流域1982—2021年植被覆盖空间格局、月际和年际变化规律。结合同时段的年平均气温和年降水量，采用二元线性回归分析和残差分析等方法，探讨了黄河流域植被覆盖的主要影响因素。根据时空变化分析，1982—2021年黄河流域多年NDVI均值变化趋势由西北向东南依次增加，年际变化呈现波动增长趋势，增长速率为0.019 (10a) −1，月际变化呈现先增后减的单峰曲线状分布，8月（0.50）为峰值。根据变化趋势分析，1982—2021年黄河流域77.35%的区域植被覆盖呈增加趋势。根据影响因素分析，黄河流域植被覆盖以气候变化和人类活动共同作用为主要影响因素，其中受人类活动促进作用较为明显，约占46.13%。因此，气候变化和人类活动共同作用是黄河流域植被覆盖变化的影响因素，其中人类活动对植被恢复有重要作用。 |
| 关键词: 黄河流域 GIMMS NDVI MODIS NDVI 植被覆盖 多元线性回归模型 残差分析 |
| DOI：10.7515/JEE222016 |
| CSTR： |
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| 基金项目:国家自然科学基金项目（41972189）；中央高校基本科研业务费专项资金；河南省高等学校重点科研项目（22A170012）；河南省科技攻关项目（222102320236）；黄河中下游地理空间技术教育部重点实验室（河南大学）开放基金（GTYR202106） |
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| Study on the spatial-temporal evolution and influence factors of vegetation coverage in the Yellow River Basin during 1982 — 2021 |
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LI Xueyin, ZHANG Zhiqiang, SUN Aizhi
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1. College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
2. College of Surveying and Geo-Informatics, North China University of Water Resources and Electric Power, Zhengzhou 450045, China
3. Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions (Henan University), Ministry of Education, Kaifeng 475001, China
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| Abstract: |
| Background, aim, and scope Depicting the spatial-temporal dynamics of vegetation coverage in the Yellow River Basin and delineating the influences of climate change and human activities on the dynamics has are of significant importance for understanding the surface earth systems in general and also for formulating ecological protection plans of the Yellow River Basin in particular. This study uses GIMMS NDVI data from 1982—2015 and the MODIS NDVI data from 2000—2021 to explore the spatial and temporal characteristics of vegetation covers in the Yellow River Basin for the period from 1982 to 2021 with an attempt to reveal the influencing factors. Materials and methods Based on GIMMS NDVI and MODIS NDVI, this paper employs several methods including maximum value composite, mean, Theil-Sen Median trend analysis and Mann-Kendall test to analyze the spatial distribution and inter-annual and inter-month changes of the vegetation covers in the Yellow River Basin. The influencing factors were explored through examining the correlations of the spatial and temporal characteristics of the remotely-sensed vegetation covers with the climate factors (i.e., temperature and precipitation) and human activities (e.g., land-use types and ecological protection methods) using binary linear regression analysis and residual analysis and other methods. Results Our analytical results show that the multi-year average NDVI values increased from the northwest to the southeast and that the annual mean values of the vegetation covers fluctuate relatively greatly along an increasing trend with a growth rate of 0.019·(10a) −1. Understandably, the monthly mean values showed a single-peak distribution pattern with August being the peak time. Overall, 77.35% of the studied areas were characterized by exhibiting an increasing trend of vegetation cover during the study period (i.e., 1982—2021). Our analytical results also show that the vegetation coverage of the Yellow River Basin is affected by the combined effects of climate change and human activities with human activities being more significant in the observed amelioration of vegetation cover. Discussion Compared with previous studies, our analytical results show that the spatial-temporal distribution of vegetation coverage in the Yellow River Basin is significantly different, and the overall vegetation coverage in the Yellow River Basin show an increasing trend. Due to the joint effect of climate change and human activities, the vegetation coverage of the Yellow River Basin increases from northwest to southeast, and human activities mainly promoted the growth of vegetation coverage. However, there are still some areas with a downward trend of vegetation cover (e.g., some areas in the upper reaches of the Yellow River, which need to be strengthened management and protection by relevant departments. Conclusions In brief, several conclusions can be drawn from this study. First, the overall vegetation coverage showed an increasing trend during the study period. Second, the vegetation coverage increased from the northwest to the southeast. Third, the observed changes in the vegetation coverage were influenced by both climate and human factors with human factors being more significant. Recommendations and perspectives It should be particularly pointed out that the vegetation in some areas of the Yellow River Basin experienced deterioration under the background of overall amelioration in the entire basin and the areas need management attention. |
| Key words: Yellow River Basin GIMMS NDVI MODIS NDVI vegetation coverage multiple linear regression model residual analysis |
