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Remote Sens. 2016, 8(11), 910; doi:10.3390/rs8110910

Vegetation Responses to Climate Variability in the Northern Arid to Sub-Humid Zones of Sub-Saharan Africa

1
Department of Geographical Sciences, University of Maryland, College Park, MD 20782, USA
2
Department of Geography, University of California-Los Angeles, Los Angeles, CA 90095, USA
*
Author to whom correspondence should be addressed.
Academic Editors: Rasmus Fensholt, Stephanie Horion, Torbern Tagesson, Martin Brandt, Alfredo R. Huete, Clement Atzberger and Prasad S. Thenkabail
Received: 3 June 2016 / Revised: 12 October 2016 / Accepted: 18 October 2016 / Published: 2 November 2016
(This article belongs to the Special Issue Remote Sensing of Land Degradation and Drivers of Change)
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Abstract

In water limited environments precipitation is often considered the key factor influencing vegetation growth and rates of development. However; other climate variables including temperature; humidity; the frequency and intensity of precipitation events are also known to affect productivity; either directly by changing photosynthesis and transpiration rates or indirectly by influencing water availability and plant physiology. The aim here is to quantify the spatiotemporal patterns of vegetation responses to precipitation and to additional; relevant; meteorological variables. First; an empirical; statistical analysis of the relationship between precipitation and the additional meteorological variables and a proxy of vegetation productivity (the Normalized Difference Vegetation Index; NDVI) is reported and; second; a process-oriented modeling approach to explore the hydrologic and biophysical mechanisms to which the significant empirical relationships might be attributed. The analysis was conducted in Sub-Saharan Africa; between 5 and 18°N; for a 25-year period 1982–2006; and used a new quasi-daily Advanced Very High Resolution Radiometer (AVHRR) dataset. The results suggest that vegetation; particularly in the wetter areas; does not always respond directly and proportionately to precipitation variation; either because of the non-linearity of soil moisture recharge in response to increases in precipitation; or because variations in temperature and humidity attenuate the vegetation responses to changes in water availability. We also find that productivity; independent of changes in total precipitation; is responsive to intra-annual precipitation variation. A significant consequence is that the degree of correlation of all the meteorological variables with productivity varies geographically; so no one formulation is adequate for the entire region. Put together; these results demonstrate that vegetation responses to meteorological variation are more complex than an equilibrium relationship between precipitation and productivity. In addition to their intrinsic interest; the findings have important implications for detection of anthropogenic dryland degradation (desertification); for which the effects of natural fluctuations in meteorological variables must be controlled in order to reveal non-meteorological; including anthropogenic; degradation. View Full-Text
Keywords: primary production; NPP; NDVI; land degradation; Sahel; rainfall; temperature; humidity; RUE primary production; NPP; NDVI; land degradation; Sahel; rainfall; temperature; humidity; RUE
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Rishmawi, K.; Prince, S.D.; Xue, Y. Vegetation Responses to Climate Variability in the Northern Arid to Sub-Humid Zones of Sub-Saharan Africa. Remote Sens. 2016, 8, 910.

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