Combating Desertification And Soil Degradation

The protecting role of vegetation is the base for many erosion control, soil conservation, and rangeland management measures. Vegetation cover reduces splash erosion due

FIGURE 16-6 Airphoto map with additional GIS layers of the test site (Testfeld) and its surroundings at Arnas in the central Pyrenees, Province of Jaca, Spain. The grazing control site (Beweidungskontrollflachen) is to the right of the image center. Blue triangles indicate rainfall simulation microplots, brown squares soil profile pits. Hot-air blimp photograph taken by IM, JBR, and M. Seeger, August 1998. Image processing by IM; taken from Ries et al. (2000, fig. 3).

FIGURE 16-6 Airphoto map with additional GIS layers of the test site (Testfeld) and its surroundings at Arnas in the central Pyrenees, Province of Jaca, Spain. The grazing control site (Beweidungskontrollflachen) is to the right of the image center. Blue triangles indicate rainfall simulation microplots, brown squares soil profile pits. Hot-air blimp photograph taken by IM, JBR, and M. Seeger, August 1998. Image processing by IM; taken from Ries et al. (2000, fig. 3).

FIGURE 16-7 Vegetation cover of the grazing control cage (left) and reference site (right) at Arnas in July 1996, August 1997, and August 1998. White to dark gray are grass and herbs cover classes, black is full shrub cover. Image analysis by IM; adapted from Ries et al. (2000, fig. 10).

to interception of rainfall, decreases overland flow, and improves infiltration of precipitation and runoff water into the soil. One example for such vegetation regeneration measures was documented by SFAP on the wide and flat glacis areas of northern Burkina Faso (see Fig. 5-19), where the international non-governmental organization ADRA conducted tillage experiments in 2000 and 2001. A specially developed plow was used for carving deep furrows into the hard and bare clayey surface in order to reduce overland flow and encourage infiltration (Fig. 16-9). On the ridges piled up next to the furrows, various tree species were planted. It was expected that grasses would come up both in the furrows and the interlaced glacis strips, further increasing the erosion-control effects.

Experimental measurements of runoff and erosion rates on sites treated two rainy seasons apart could show that both factors were significantly reduced on earlier treated areas when compared to only recently treated

FIGURE 16-8 Vegetation cover at the test site Arnas. (A) Actual cover in July 1996, classification based on hot-air blimp photograph. Note the clearly visible open sheep trails between the shrubs where the sheep enter the test site through a wall opening in the upper left. (B) Simulated vegetation cover in summer 1998, assuming that grazing was discontinued two years previously. GIS analysis based on the results shown in Figure 16-7. Image processing by IM; adapted from Ries et al. (2000, figs. 7 and 11).

FIGURE 16-9 Tillage experiments for soil conservation near Gorom-Gorom, Province of Oudalan, Burkina Faso. Photo by JBR, July 2000.

sites, proving the short-term effectiveness of the measures. KAP was taken to document the vegetation development and assess its spatial extent (Fig. 16-10). The increase of grass cover, here shown in the dry season of December 2001, is stunning. In view of improving the resilience of this vulnerable area to climatic change, livestock pressure, and increasing food security, the experiments are promising. However, the success of the measures also depends on the future management of the improved sites. For a prevailing regeneration of the barren glacis areas and sustainable use as rangeland, grazing management strategies are of vital importance in a region where the number of cattle is directly correlated to fodder supply.

FIGURE 16-10 Tillage experiment sites seen from the air. (A) July 2000. (B) December 2001. Kite aerial photographs taken by IM, JBR, and K.-D. Albert.
100 Photography Tips

100 Photography Tips

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