Abstract
To detect changes in vegetation is desirable for modeling and predicting interactions between land surface and atmosphere. Multitemporal series of SPOT VEGETATION NDVI dataset and meteorological data were integrated to interpret vegetation dynamics and the linkage with climate variations in the upper and middle reaches of the Nenjiang River Basin (NRB) from 1999 to 2010 using the correlation analysis and the rescaled range (R/S) analysis. The results demonstrate that annual NDVI increased slightly and 26.02% vegetation coverage of the study area significantly improved. The area of significantly decreased in vegetation cover took up 13.33% of the total land in spring. In autumn, 26.2% of the study area showed a significant vegetation increase. The improved activity of vegetation might reinforce in summer and autumn, while the decreasing tendency in spring might be persistent in the future. The yearly NDVI had significant positive linkages with precipitation and relative humidity. NDVI related significantly and negatively with temperature, sunshine hours and wind velocity, because they may have effects of increasing evapotranspiration and risk of drought and cold damage of vegetation. The variations of annual NDVI were much affected by summer temperature, relative humidity and sunshine duration in autumn and spring wind velocity. Seasonal NDVI decreased in parallel with elevated temperature, but there was no correlation between NDVI and precipitation. Spring temperature, relative humidity in summer and autumn contributed markedly to NDVI variations in the same season. The vegetation improving trend may induce by the warm-wetting climate in recent twelve years.
Highlights
Vegetation affects several processes such as water balance, latent and sensible heat fluxes and carbon cycle
The annual average Normalized Difference Vegetation Index (NDVI) slightly increased with an undulating trend in the upper and middle reaches of the Nenjiang River Basin (NRB) (Table 1)
NDVI decreased by 1.3% and 6.3% implying degraded vegetation cover during 1999–2001 and 2007–2009
Summary
Vegetation affects several processes such as water balance, latent and sensible heat fluxes and carbon cycle. Various NDVI datasets have been widely applied to assess terrestrial vegetation vigor at regional and global scales during past decades (Lambin and Strahlers, 1994; Ludeke et al, 1996; Lambin, 1996; Piao and Fang, 2001; Zhou et al, 2001; Fang et al, 2003; Ma and Frank, 2006; Fensholt et al, 2009; Huang and Wang,2010; Amri et al, 2011; Sun et al, 2011; Schucknecht et al, 2013; Horion et al.,2014; Ivits et al.,2014; Du et al, 2016). In the past a few decades, land surface condition changes resulting from urbanization, water project constructions and agricultural activities have been dramatic. The main purposes of this study are (1) to elaborate the interannual and seasonal variations in the coverage of vegetation in the upper and middle reaches of the Nenjiang River Basin (NRB), (2) analyze the possible causes of vegetation changes based on multitemporal NDVI, meteorological data for the period of 1999 to 2010. The result may offer scientific evidences for the land management and landscape ecological regulation in this region
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