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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/62

Authors: Taye, Jara
Keywords: Canopy regeneration
Gap regeneration
Gap makers
Gap filler
Replacement probabilities
soil seed Bank
Date Added: 4-Sep-2007
Abstract: Change in forest communities and recruitment of new individuals into tree populations depend on the dynamics and formation of canopy gaps. Gap dynamics and canopy gap regeneration were investigated in Harena Forest of Bale Mountains, Southeastern Ethiopia at altitudes ranging from 3000 – 2000 m a.s.l. Wind was found to be the main type of natural disturbance resulting in the overthrow and snapping of heavily crowned emergent canopy trees. The most affected canopy species by this disturbance regime was Dombeya torrida. 14 species were found to be gap makers. The mean DBH of the gap makers was 50.4cm. Mean gap size of the forest was (289.74+165.48 m2) and almost all the gaps were found in sloppy areas. Twenty-four different woody species were encountered as gap–filler species along different altitudes. Of these species, six were recruited only in gap sites while the gap environment favored most of the rest. Seedling and sapling density of the gaps were higher than that of closed canopied sites indicating the importance of gaps for maintaining woody species diversity in the forest. The strong negative correlation between slope, altitude, and species and seedling densities indicates that both factors affect gap regeneration. Otherwise, gap size differentiation in the forest and replacement probabilities in the Harena forest was weak (less than 0.5) except for Diospyros abyssinica(0.86); most of the gap makers were replaced by other subcanopy species of the forest. Thus, species recruitments in gaps of the forest are likely due to chance effects. Germination trial of the soil seed banks of Harena forest collected from the sampled gaps and canopied sites has revealed a high dominance of herbaceous species. Only five of the 24-gap filling species and three of the gap maker species were recovered in the soil seed bank of the gap sites and even that was in smaller density. Thus, the chance of getting an immediate replacement of the canopy trees, if removed naturally, was found to be minimal.
Description: A Thesis Presented to the School of Graduate Studies Addis Ababa University In partial fulfillment of the Requirements for the Degree of Masters of Science in Biology
URI: http://hdl.handle.net/123456789/62
Appears in:Thesis - Biology

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