Regional Characterization of Inland Valley Agroecosystems in Save, Bante, Bassila, and Parakou Regions in South Central Republic of Benin
Total Page：16
File Type：pdf, Size：1020Kb
Regional Characterization of Inland Valley Agroecosystems in Save, Bante, Bassila, and Parakou Regions in South central Republic of Benin through Integration of Remote Sensing Global Positioning System, and Ground-Truth Data in a Geographic Information Systems Framework Prasad S. Thenkabail and Christian Nolte Inland valley watershed system highlighting the valley bottoms • Uplands o Intensely cultivated valley bottoms ESl Moderately cultivated valley bottoms 8ll Uncultivated valley bottoms International Institute of Tropical Agriculture with Inland Valley Consortium Inland Valley Characterization Report 1 Regional Characterization of Inland Valley Agroecosystems in Save, Bante, Bassila, and Parakou Regions in South-Central Republic of Benin through Integration of Remote Sensing, Global Positioning System, and Ground-Truth Data in a Geographic Information Systems Framework Prasad S. Thenkabail and Christian Nolte International Institute of Tropical Agriculture with Inland Valley Consortium Preface The inland valley characterization report series of the Resource and Crop Management Division (RCMD) is intended for the wide dissemination of results of research about the inland valley agroecosystems of sub-Saharan Africa. These research reports will address issues relating to characterization and diagnosis concerning inland valley agroecosystems. The range of subject matter is expected to contribute to existing knowledge on improved agricultural principles, practices, and policies that affect the sustainable development of these potentially rich and productive agroecosystems of sub-Saharan Africa. These reports summarize results of studies by lITA researchers and their collaborators; they are generally more substantial in content than journal articles. The research report series is aimed at scientists and researchers within the national agricultural research systems of Africa, the international research community, policy makers, donors, and international development agencies. Individuals and institutions in Africa may receive single copies free of charge by writing to: The Director Resource and Crop Management Division International Institute of Tropical Agriculture PMB 5320 Ibadan Nigeria The Authors Dr. Prasad S. Thenkabail is a Visiting Scientist, Remote Sensing Specialist, at Agroecological Studies Unit of RCMD, IITA. Dr. Christian Nolte is an Associate Scientist, Wetland Agroecosystem Agronomist, at Agroecological Studies Unit of RCMD, lITA. '" 1995 International Institute of Tropical Agriculture ii Contents I. Introduction and Background ...................................... I II. Study Area and Satellite Data Characteristics . .. 6 2.1 Physical characteristics of the study area ........................ 6 III. Ground-Truth Data .. 23 3.1 Methodology 23 IV. Results and Discussion ........................................ 26 4.1 Mapping valley bottoms and valley fringes ...................... 26 4.2 Mapping settlements and road networks using TM data .............. 26 4.3 Land-use characterization of valley bottoms, valley fringes, and uplands ... 28 4.4 Discussion of results: valley bottoms, valley fringes, and uplands ....... 31 4.5 Spectral characteristics of land-use classes ...................... 32 4.6 Cultivation intensities with respect to distance from settlements and road networks .... .................................. 33 4.7 Studying the cultivation pattern across the toposequence in the entire study area 34 4.8 Studying inland-valley characteristics from ground-truth data ......... 34 4.9 Establishing morphometric characteristics from ground-truth and TM data 37 4.10 Determining the cropping pattern of inland valleys from ground-truth data ... 37 V. Key Site and Key Watershed Selection for Technology Development ............. 41 VI. Summary and Conclusions ....................................... 42 References .................................................... 45 Tables I. Parameters describing liTA 's level I agroecological and soil zones .............. 2 2. Legend to the land-regions map of the WURP report ...................... 4 3. Areas of level I agroecological and soil zones covered by Landsat TM path: 192, row:54 .................................... 7 4. Distribution of soil units in the study area (according to FAa/UNESCO 1977) ....... 8 5. Thematic Mapper vegetation indices for agroecological zones and the entire study area .......................................... 18 6. Rainfall in the study area ........................................ 19 7. Discharge of sample watersheds in the study area ......................... 22 8. Land-use categories, their vegetation distribution, and description in valley bottoms, valley fringes, and uplands of the study area ................. 24 9. Land-cover types identified in this study .............................. 25 10. Percentage distribution of land-cover types in the 16 land-use classes ............ 25 II. Population, settlements, and major road networks in the study area ............. 27 12. Distribution of land-use classes in the different agroecological and soil zones of the study area ......................................... 29 iii 13. Distribution of valley bottoms, valley fringes and uplands, and their cultivation pattern in the study area ................................. 30 14. TM-derived vegetation indices for the final land-use classes .................. 32 15. Cultivation pattern of valley bottoms, valley fringes, and uplands with respects to their distance from settlements and road networks for different level I rones . .. 35 16. Morphometric characteristics of inland valleys in the two agroecological and soil zones obtained through ground-truth data ........................ 36 17. Characteristics of watersheds of inland valleys analyzed with Landsat-TM and ground-trulh data .......................................... 38 18. Land-use pattern in valley bottoms, at valley fringes, and on uplands of the study area, determined using ground-truth data ........................ 39 19. Farmland cropping pattern in bottoms, fringes, and on uplands of inland valleys in the study area, determined using ground-truth data ...................... 40 Figures 1. Landsat and SPOT acquisitions for level II characterization of inland valley agroecosystems in the level I agroecological and soil zones ............ insert: pp.2/3 2. Location of Landsat-TM and SPOT-HRV acquisitions in land regions of West Africa according to the WURP map ............................. 3 3. Cross-section showing a model inland valley as defined in this study ............ 5 4. Location of the study area and the ground-truth sites ....................... 10 5. Spatial distribution of the level 1 agroecological and soil zones in this study area; the total study area covers about 3.2 million ha of which 49% fall into AEZ 2 and 46% into AEZ 7 ......................... 11 6. Population density in the study area ................................. 12 7. Geological formations in the study area ............................... 13 8. Soils distribution in the study area .................................. 14 9. Characterization of cropping systems in the Republic of Benin (Manyong et aI. in preparation) .................................... 16 10. Characterization of agricultural systems in the Republic of Benin (Manyong et aI. in preparation) .................................... 17 11. Rainfall zones, discharge units and isohyetes, and location of rainfall and discharge stations in the study area .................................. 20 12. Mean monthly discharge in percent of the annual total (reference period 1960-1984) at 6 stations in the study area .................. 21 13. Selected vegetation indices for land-use class 1 through 16 . .. 34 iv Plates - see centerfold - I. Ratio RGB image of Landsat TM bands: TM4rrM7 (red), TM4rrM3 (green), TM4rrM2 (blue) distinguishing the inland valley bottoms from fringes and uplands for a subarea of Landsat path: 192, row:54 in Save, Republic of Benin 2. Inland valley bottoms delineated and diS(11ayed as a false color composite of TM bands: TM4 (red), TM3 (green), and TM5 (blue). Color key: red (densest vegetation), shades of green and blue (very little and/or dry vegetation. The NDVI values were less than 0.10 for these areas) 3. Inland valley fringes for the same subarea as shown in plates I and 2 displaying the false color image of TM4 (red), TM3 (green), TM 5 (blue). Color key: red (densest vegetation), shades of green (lowest density and vigor of vegetation), and shades of blue and gray (intermediate vegetation) 4. Inland valley bottoms and their land use delineated and mapped for the entire study area of Landsat TM path: 192, row:54 (Save, Republic of Benin). The total valley bottom area was 9% (0.28 million ha) of the total area (see the legend for color key) 5. Land-use classes mapped for the different components of the toposequence (valley bottoms, valley fringes, and uplands) for the entire study area of 3.12 million ha covered by Landsat TM path: 192, row:54 in Save, Republic of Benin (see the legend for color key) 6. Land-use classes in a subarea near Gouka, Republic of Benin. Note the relatively high density of cultivation across the toposequence in areas adjoining roads and settlements (see legend for color key) 7. Cultivation intensities in inland valleys (valley bottoms plus valley fringes) relative to their distance from roads and settlements. Note the decreasing intensities of cultivation in inland valleys with increasing distances from roads