Emphasizing the Forest Biomass Management Challenges in Commercially Exotic Tree Plantation Areas: A Case Study from the Rungwe Volcanic Province (Southern Highlands of Tanzania)

The carbon (C) stored in the living biomass of trees is typically the largest C pool of the forest
ecosystem which is directly impacted by deforestation and degradation. With the global efforts to
combat climate change through afore-station and reforestation to reduce carbon emissions in the
atmosphere, natural forests conservation and tree planting programmes are highly emphasized in
developing countries for both commercial purposes and carbon emissions reduction. Though most of
the trees planted are exotic trees especially Pinus patula, Eucalyptus saligina and partly Cypress sp.
with some fruit and shade trees in towns. Hence embarking on clearance of forest’s indigenous trees
for plantation of commercial exotic trees slightly slows down the efforts of carbon emission reduction
and mitigation of climate change through enhancement of carbon sequesters. The study was
conducted at Mbeya One ward lying between Mporoto and Rungwe forest re-serves in Mbeya rural
district, in the Southern highlands of Tanzania. The main objective was 1) to assess the indigenous
tree biomass variation between Mporoto and Rungwe forest reserves; 2) to assess the exotic tree
biomass variation between the two forest reserves; and 3) to assess the human implication on
aboveground biomass variation between the two forest reserves. The results of this study indicated
significant decrease in indigenous trees biomass in residential and crop land areas with a hasty
increase in biomass when just reaching Mporoto forest reserve indicating little human encroachment
in the forest reserve. There was the same trend towards Rungwe forest reserve; however, there was
a slight increase in indigenous tree biomass when reaching forest reserve signing presence of human
encroachment in the forest reserve. The main human activities observed in the reserve were: Timber
harvesting and commercial exotic trees planting (especially the commercial trees, Pinus patula).
There is also a massive human encroachment for indigenous trees clearance in expense of exotic
trees plantations towards and in Rungwe forest reserve. Therefore, the study would like to call for an
urgent intervention especially in the east side of the study area (Rungwe forest reserve) stopping
exotic tree plantation penetrating into the forest re-serve which intensifies cutting down of indigenous
trees in the forest reserves plummeting above ground biomass and escalating carbon emissions in
the atmosphere while jeopardizing the natural forest ecosystem services to the communities.