Abstract
In the modern era, vegetation dynamics is an important aspect of climate change studies. The present study examined spatiotemporal changes of (NDVI) normalized difference vegetation index in the Korama basin (Southern Zinder of Niger) from 2000 to 2018, and their correlation with climatic factors was predicted. To analyze the change of vegetation cover, geographical information system, MODIS_NDVI, remote sensing, and climate variables (e.g., temperature and precipitation) datasets were used. Further, the correlation was performed for different years of vegetation types during the growing season (June–October). Our results show an increasing trend in average maximum annual NDVI across the Korama River Basin in the years 2000 and 2018. Conversely, significantly increasing trends in most of the areas were reported. Moreover, in downstream the vegetation cover is increased in Matameye and Magaria, but with a smaller increase in the upstream rate in Mirriah. Furthermore, a decrease in the surface water was observed in the Tessaoua, Matameye, and Magaria sections of the study region in 2000 and 2018, while a rise in water surface area was observed in Matameye and Magaria in the years 2006 and 2012. During rainy and dry seasons, NDVI correlated differently with temperature and precipitation with strong seasonal variations, while the mean vegetation period of NDVI does not show any significant change. In addition, moderate increase was observed in years 2000 and 2012 (r: 0.22; P: 0.50; R2: 0.05; r: 0.31; P: 0.34, R2: 0.10, respectively), and weak decrease in 2006 and 2018 (r: 0.61; P: 0.04; R2: 0.37; r: 0.58; P: 0.06, R2:0.33, respectively). The analysis indicates that climatic parameters such as precipitation and temperature are the main limiting factors affecting the vegetation growth. Indeed, the trends calculated by the correlation analysis showed that as climate factors increased (July, August, and September), the NDVI value increased at a rate of 0.16, reflecting the best growth in vegetation and rise in water bodies, although significantly decreased during years. This study would be highly useful in choice-making for sustainable water resource management in the Korama watershed in Southern Zinder, Niger.
Highlights
Vegetation is the key component of the earth’s terrestrial ecosystems and plays a major role in soil, energy exchange, and biogeochemical cycles on earth’s surface (Liu et al 2018; Ning et al 2015)
A decrease in the surface water was observed in the Tessaoua, Matameye, and Magaria sections of the study region in 2000 and 2018, while a rise in water surface area was observed in Matameye and Magaria in the years 2006 and 2012
The trends calculated by the correlation analysis showed that as climate factors increased (July, August, and September), the NDVI value increased at a rate of 0.16, reflecting the best growth in vegetation and rise in water bodies, significantly decreased during years
Summary
Vegetation is the key component of the earth’s terrestrial ecosystems and plays a major role in soil, energy exchange, and biogeochemical cycles on earth’s surface (Liu et al 2018; Ning et al 2015). Vegetation is the natural connection of the earth to the soil, atmosphere, and humidity It indicates clear signs of seasonality and inter-annual change (Chuai et al 2013; Cui and Shi 2010) and is a touchy indicator of worldwide climate change (Weiss et al 2004); vegetation responds and subtly to weather change. The mathematical representation of NDVI is given as follows: NDVI = (NIR-Red)/(NIR + Red), where NIR represented reflectance radiated in near-infrared wavebands and Red in the visible reflectance wavebands from the satellite It is the primary indicator of the growth and spatial pattern of vegetation (Liu et al 1999; Purevdorj et al 1998), as well as plant morphology (Defries and Townshend 1994; Derrien et al 1992). Over the last three decades, NDVI has been widely used for analyzing climatic effects on modifications on productivity of in plant life (Chuai et al 2013; Hu et al 2011; Nemani 2003), whereas some recent studies examined hydrological responses to vegetation cover changes. Jiao et al (2017) analyzed the effect of vegetation dynamics on hydrological processes in a semiarid basin using a land surface hydrology coupled model and found that vegetation dynamics induced higher ET, lower runoff, and soil moisture content and decelerated the evolving trend of discharge (Zhang et al 2019; Wu et al (2020)
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