Abstract
Monitoring temporal changes of aboveground carbon (AGC) stocks distribution in subtropical thicket is key to understanding the role of vegetation in carbon sequestration. The main objectives of this research paper were to model and quantify the temporal changes of AGC stocks between 1972 and 2010 in the Great Fish River Nature Reserve and its environs, Eastern Cape Province, South Africa. We used a method based on the integration of remote sensing and geographical information systems to estimate AGC stocks in a time series framework. A non-linear regression model was developed using Normalised Difference Vegetation Index values generated from SPOT 5 High Resolution Geometric satellite imagery of 2010 as an independent variable and AGC stock estimates from field plots as the dependent variable. The regression model was used to estimate AGC stocks from satellite imagery for 1972 (Landsat TM), 1982 (Landsat 4 TM), 1992 (Landsat 7 ETM), 2002 (Landsat ETM+) and 2010 (SPOT 5) satellite imagery. AGC stocks for the respective years were compared by means of change detection analysis at the subtropical thicket class level. The results showed a decline of AGC stocks in all the classes from 1972 to 2010. Degraded and transformed thicket classes had the highest AGC stock losses. The decline of AGC stocks was attributed to thicket transformation and degradation, which were attributed to anthropogenic activities.
Highlights
IntroductionRecent studies have shown that forests store close to 289 919 t of carbon in trees and other vegetation.[1] the rate of deforestation has become a subject of major concern for many scientists
The role of forests as a carbon source and sink has been widely explored
This stratification was performed with the aid of a land use/cover map generated from the 2010 SPOT (HRG) imagery and was undertaken in order to obtain precise estimates of the subtropical thicket vegetation parameters
Summary
Recent studies have shown that forests store close to 289 919 t of carbon in trees and other vegetation.[1] the rate of deforestation has become a subject of major concern for many scientists. The global forest deforestation rate has been approximated at -7317% per year between 2000 and 2005.1-3 Approximately 13 million ha of world forest was lost between 2000 and 2010,4 implying an increase in the amount of carbon dioxide into the atmosphere.[1,5] Africa’s forests are disappearing at a rate approximately four times more than that of the world average.[6] A study by the United Nations Environment Programme (UNEP) conducted in 2006 estimated that 70%, 95% and 30% of forests in West Africa, East Africa and the Democratic Republic of Congo, respectively, would be decimated by 2040. Deforestation and forest degradation contribute to atmospheric greenhouse gas emissions through the combustion of forest biomass and decomposition of the remaining plant material.[7]
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