University of Khartoum

Vegetation Change in Erkowit, Northeastern Sudan between 1953 - 2009

Vegetation Change in Erkowit, Northeastern Sudan between 1953 - 2009

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Title: Vegetation Change in Erkowit, Northeastern Sudan between 1953 - 2009
Author: Salih, Elsir Adam Omer
Abstract: This study is a comparative study which is based mainly on resurveying the natural vegetation in the study area, Erkowit, and comparing the present situation with the situations in 1953 and 1989. The mainobjectives of this study were to evaluate whether changes in species composition observed from 1953 to 1993 continued, what is the main driver of vegetation change in the area: land use changes or climate, and whether the vegetation has become more homogenous i.e. has beta diversity decreased. The study resurveyed the vegetation on thirty of the originally surveyed hills in 1953and 1989. The relative abundance of each perennial plant species was estimated per hill by visual estimation. Due to the large areal extent of the hills (3140 m2 to 96460 m2) the species were assigned to abundance categories: d = dominant, a = abundant, c = common, o = occasional and r = rare. For numerical analysis, the abundance classes were coded as; r = 0.5, o = 1, c = 2 and a/d = 4. Gradient Analysis was used to analyse the change in species composition, then the gradient axes were scaled in standard deviation units (SDU), which make them directly interpretable in terms of species homogeneity i.e. beta diversity. The results clearly indicate a spatial and temporal trend in the vegetation development in the area. The secondary succession described by Vetaas (1993) appears to have continued in the last 20 years, and it may have accelerated because the differences in species composition between years of sampling were larger in the period between 1989 and 2009 compared to the period between 1953 and 1989. Changes in plant species composition has been reflected on Beta diversity which has slightly decreased from 2.6 to 2.51 SDU. The landscape at Erkowit has been changing continuously from a semi-evergreen woodland to a very open shrubland, similar to hot desert shrubland that surrounds Erkowit, and is not comparable any more to a mist oasis dominated by Afromontane and Mediterranean species that was reported in the twentieth century. As shown by species scores on the temporal axis of the gradient analysis, toxic plants have continued to increase, whereas Afromontane and Mediterranean species in general have decreased. The former indicates land use change as a driver, and the latter indicates climate change.
URI: http://khartoumspace.uofk.edu/123456789/17122
Date: 2015-11-16


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