ASSESSMENT OF CARBON SEQUESTRATION BY DRYLAND FOREST AND ECO-CHAR SYSTEM IN TAITA RANCH- VOI, KENYA

Abstract

Mapping carbon stock in Kenya is central in establishing the country’s potential for carbon emission and emission reduction through forestry. The study aimed to establish the carbon biomass capture and storage by the common tree genus in dryland forest and to assess the sustainability of eco-char production system in Taita Ranch, South Eastern Kenya. Non-destructive approach was used, where key parameters including diameter at breast height (DBH) and Tree height were measured in the field and used to compute carbon biomass estimates. This study fit into an ongoing research experimental set-up, where tenone hectare (ha) blocks have been curved out of a larger area of approximately one thousand and one hundred ha (1100ha) where branch harvesting for eco-charcoal production is done. These blocks were randomly selected and used to study the effects of harvesting at various intensities and frequency on the trees’ growth and regeneration. A total of two thousand and sixty (2060) trees belonging to twenty five tree species from 14 genuses were inventoried from the Ten-one ha plots. Genus Commiphora dominated the study area with approximately 47% followed by Lannea with 19% and Boswellia at 13% and Acacia and Boscia recorded 9% each while the other pooled genus contributed approximately 3%. Species specific Allometric equations generated by Wildlife Works were used to compute tree biomass. Total biomass estimate was approximately 32.8 Mg/ha. Advanced linear regression model was used to perform significance across the study blocks and tree genus. Similarly, t-test was conducted for hypothesis testing. The analysis revealed high significance for mean biomass across the study blocks and tree genus whereby genus Commiphora had the highest mean biomass of 24.1Mg ha-1 followed by genus Acacia by 3.0 Mgha-1. Similarly, genus Acacia had low density that made it insignificant in carbon sequestration in Taita Ranch. Nonetheless, it has high potential in carbon capture as exhibited by least square mean analysis that indicated genus Acacia with highest mean of approximately 0.2 Mg of biomass while an individual in genus Commiphora recorded the approximately 0.1 Mg of biomass. Based on these estimates, then Acacia species with an average diameter at breast height of 13 cm can potentially release 0.33 Mg of Carbon if the whole tree is harvested for charcoal production, while an individual in genus Commiphora would release approximately 0.17 Mg. On the other hand genus Commiphora is very light but its abundance makes it to be potentially important. Pruning of trees and branches at 25% and 50% and eco-char production system has no significant impact on the study area biomass and thus the study recommends it to be included in Reducing Emission from Deforestation and Degradation plus programs in dryland forest.