Search

African tropical montane forests are facing fast and dynamic changes in land use. However, the impacts of these changes on stream water quality are understudied. This paper aims at assessing the effect of land use and physical catchment characteristics on stream water concentrations of dissolved organic carbon (DOC), total dissolved nitrogen (TDN), nitrate (NO 3 -N) and dissolved organic nitrogen (DON) in the Mau Forest, the largest tropical montane forest in Kenya. We conducted five synoptic stream water sampling campaigns at the outlets of 13–16 catchments dominated by either natural forest, smallholder agriculture or commercial tea and tree plantations. Our data show a strong effect of land use on TDN and NO 3 -N, with highest concentrations in stream water of catchments dominated by tea plantations (1.80 ± 0.50 and 1.62 ± 0.60 mg N l −1 , respectively), and lowest values in forested catchments (0.55 ± 0.15 and 0.30 ± 0.08 mg N l −1 , respectively). NO 3 -N concentration increased with stream temperature and specific discharge, but decreased with increasing catchment area. DOC concentrations increased with catchment area and precipitation and decreased with specific discharge, drainage density and topographic wetness index. Precipitation and specific discharge were also strong predictors for DON concentrations, with an additional small positive effect of tree cover. In summary, land use affects TDN and NO 3 -N concentrations in stream water in the Mau Forest region in Kenya, while DOC and DON were more related to hydrologic regimes and catchment properties. The importance of land use for NO 3 -N and TDN concentrations emphasizes the risk of increased nitrogen export along hydrological pathways caused by intensified land use and conversion of land to agricultural uses, which might result in deterioration of drinking water quality and eutrophication in surface water in tropical Africa. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, energy consumption and carbon dioxide emissions from 17 countries of the Middle East and North Africa are studied using Data Envelopment Analysis. Four indicators for the year 1996 are employed in the analysis. The analysis shows that Sudan, Bahrain and Oman are considered efficient, and Saudi Arabia is rated as the least efficient under constant returns to scale (CRS) assumption. Mauritania and Israel are considered efficient under variable returns to scale (VRS) assumption, indicating that the CRS inefficiency of these two countries is due to the fact that they are not operating at the best possible scale size. The patterns of changes in efficiency of the countries are further analyzed using Malmquist Productivity Index (MPI) approach for the period of 1992–1996. The analysis shows that there is progress in achieving higher values of output-side indicators and in achieving lower values of the input-side indicators in the year 1996 compared to 1992 for 5 out of the 17 countries (Algeria, Egypt, Sudan, Oman and Syria). [Copyright &y& Elsevier]