Impact evaluation on survival of tree seedling using selected in situ rainwater harvesting methods in Gerduba Watershed, Borana Zone, Ethiopia.

Abstract

Establishing forest plantation on degraded rangelands play a key role in forest rehabilitation processes through afforestation or/and reforestation. In-situ rainwater harvesting has positive impact on seedling survivals at degraded rangelands. A quadrant of 10 m × 10 m of five times replication at three slope classes under area enclosure was used. Both survived seedlings and soil physical parameters were collected from three soil depth profiles (0-10, 10-20 and 20-30 cm) and then analyzed. Of the transplanted seedling to the area enclosure with pits (66.53, 46.13, and 25.66%), half-moon (66.53, 41.80, and 20.40%), and soil bund embankment (55.46, 42.60, and 28.80%) were survived at bottom, middle and upper slope classes respectively. The interaction of seedling survival in both planting methods were not significantly different at P>0.05, particularly, in half-moon and pits except soil bund embankment. Because, tree seedling rose at nursery site transplanted to the embankment of structures, that is, on the dig out soils. The conserved moisture is far from seedling roots as a result needs long roots to absorb but weak and short rooting system. Pits and half-moon showed good performance than soil embankments at bottom parts. This explains that almost all in-situ structures play a crucial role at flat land rather than middle and upper parts but highest bulk density achieved for the upper parts, which might be due to risks of soil erosion and only left with very compacted cobles. Therefore, slope gradient have implication on in-situ rainwater harvesting devices efficiencies in conserving moisture for tree seedling survival so as to establish good forest stands. Key words: Growth, in-situ rainwater harvesting, moisture stress, seedlings, survival.