Classification And Net Primary Productivity Of Potential Natural Vegetation In Africa Continent From 1911 To 2013

Terrestrial ecosystem is highly sensitive to the global climate change,especially the changes in temperature and precipitation,which are the dominant factor controlling plant growth.African continent is one of the most regions vulnerable to global climate change,raising the air temperature and changes in precipitation affected the continent potential natural vegetation PNV types and distribution.In this study,we used CRU TS v3.22 datasets and geographic information system(GIS)software to simulate the distribution of PNV of African continent based on the comprehensive and sequential classification system approach CSCS and their net primary productivity for the time period 1911 to 2013.The result showed that;African continent had 24 PNV classes from 1911 to 1945,1946 to 1980,and it had seven broad potential natural vegetation categories form 1911 to 1945 and from 1946 to 1981.The period from 1981 to 2013 showed decreasing in PNV classes,which had 23 classes and increasing in PNV categories(eight vegetation categories);this period showed disappearance of mixed coniferous leaved forest and the sub-tropical desert(VA)classes,and appearance of the meadow steppe(IIID)class.For the PNV categories,the warm desert broad PNV category formed the largest area flowed by savanna,while the steppe formed the lowest area.The total area of PNV was decreased by 19% from 1911 to 2013.Most of the decreasing trend was occurred in the forest broad vegetation categories.In regard to the net primary productivity NPP Thornthwaite memorial model was used in this study to estimate the potential NPP.The result showed;the rain forest PNV class(VIIF)is the highly productive class through the Study time periods,while the least productive class is tropical desert PNV class(VIIA),and The second most productive class is the evergreen broad-leaved forest ii PNV class(VIF).Generally the forests PNV classes showed the highly productivity such as;seasonal rain forest class(VIIE),deciduous-evergreen broad-leaved forest(VF),xerophytic forest(VIID),deciduous broad-leaved forest iii class(IVF),and deciduous-evergreen broad-leaved forest class(VE).The most productive classes in the grassland PNV are: subtropical brush steppe class(VIC)and forest steppe class(IVD).The desert PNV classes formed the lowest classes' productivity.