HR: 0800h
AN: B11B-0148    [Abstracts]
TI: Trajectories of Vegetation Change Under Controlled Land-use in Sudanian West Africa
AU: * Fisher, J I
EM: Jeremy_Fisher@brown.edu
AF: Brown University, Department of Geological Sciences, Box 1846, Providence, RI 0291 United States
AU: Mustard, J F
EM: John_Mustard@brown.edu
AF: Brown University, Department of Geological Sciences, Box 1846, Providence, RI 0291 United States
AU: Sanou, P
EM: sanoup@fasonet.bf
AF: Centre SIG et T\'{e}l\'{e}d\'{e}tection, Adjaratou, Ouagadougou, 05 BP 6154 Burkina Faso
AB: Land cover dynamics in Sudanian West African savannas are complex functions of climate variability, human migration, and increasingly intensive land-uses. The Nouhao Valley Project land management area in southeast Burkina Faso provides a large-scale natural experiment (2000 km$^{-2}$) in which pastoral and agricultural land-uses are controlled in demarcated, contiguous zones. Abandoned more than 20 years, the Nouhao Valley was resettled by plan in 1984, after the eradication of Onchocerciasis (River Blindness). Pastoralists and agriculturalists were allocated and now occupy separate Project lands; adjacent areas are mixed use (control). Quantitative satellite analyses at the regional and landscape scale reveal that policy-driven land-uses significantly alter the long-term trajectory of riparian cover in a pattern distinct from climatic regional variability. Local patterns of land-use change are overprinted on climatic variability. Trends of primary productivity, derived from the AVHRR instrument, show that while the greater region has recovered gradually after the early 1980s droughts (10 g C m$^{-2}$ y$^{-2}$ in the control area), the pastoral region of the Nouhao Valley experienced relatively enhanced growth (19 g C m$^{-2}$ y$^{-2}$). A multi-temporal spectral mixture analysis of five Landsat TM scenes, spanning the period 1984-2002, indicate that the broad increase in green vegetation abundance is similar in open savannas across all land-use types, but highly contrasted in forest galleries and riparian areas. Trajectories of green vegetation areal abundance reveal that open savanna (20-60% tree and shrub) increased by an average of 5-10% from 1984-2002 over all land-uses; forests became more vegetated by 20-30% in pastoral areas, but only 7-10% in the agriculture and control areas. Large areas in the agricultural region experienced wide-spread loss of riparian forests. The sharp contrast between the land-cover dynamics of pastoral and agricultural land-uses is significant in savanna ecosystem services management. This remote sensing approach focuses future ground-based studies towards precise drivers of change in savanna riparian areas; differentiating the degree of forest loss, riparian growth, or shrub encroachment is critical to understanding long-term sustainability.
UR: http://porter.geo.brown.edu/$\sim$jfisher/
DE: 9305 Africa
DE: 1694 Instruments and techniques
DE: 1809 Desertification
DE: 1851 Plant ecology
DE: 1640 Remote sensing
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting