Sediment and macrobenthic fauna distribution at Dar es Salaam harbour channel were investigated to attest the influence of sediment grain size distribution and total organic carbon contents on benthic macrofauna domin...Sediment and macrobenthic fauna distribution at Dar es Salaam harbour channel were investigated to attest the influence of sediment grain size distribution and total organic carbon contents on benthic macrofauna dominance and diversity. Sampling campaign was conducted from January to April, 2019 in 25 sampling stations along the channel. Sediment grain sizes ranged between 0.7405 and 0.00273 mm with an average of 0.0804 mm classified as medium silt. Sediment distribution showed an onshore-offshore pattern consisting of fine dark clay-silt sediments in the southern part of the harbour close to Mwalimu Nyerere Bridge, medium (sandy) at the harbour and coarse sandy offshore. Five classes of macrofauna were identified with sedentary Polychaetes (Diopatra cuprea) found in tubes and free forms being dominant in most of the sediment types, however more abundant in clay-silt. High species diversity index values were encountered in sediments with medium total organic carbon (TOC) and sediment grain sizes (sand-silt). Apparently, low species similarity indices were observed in all sediment type indicating significant dissimilarities in species composition among sediment grain sizes. Thus, the distribution of benthic macrofauna species along Dar es Salaam harbour channel is strongly influenced by the sediment grain sizes and organic carbon contents in sediments.展开更多
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 (Ensslin et al, 2015). The relationships between...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 (Ensslin et al, 2015). The relationships between diversity, biomass and C stocks at varied altitudes can have crucial implications for the management and conservation of C sinks. The study was conducted at Mbeya One ward lying between Mporoto and Rungwe forest reserves 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 findings indicated the significant decreased in indigenous trees biomass in residential and crop land areas with a hasty increase in biomass when reaching Mporoto forest reserve indicating little human encroachment in the forest reserve. There was the same trend towards Rungwe forest reserve however in that side, there was a slight increase in indigenous tree biomass when reaching forest reserve which is the sign of human encroachment in the forest reserve. The main human activities encroaching the reserve were;timber harvesting and commercial exotic trees planting (especially the commercial trees, Pinus patula sp). However, the trend was opposite for the exotic trees especially for Pinus patula and Eucalyptus sp in the study area. Hence the study concludes that there is a significant variation between indigenous and exotic trees in the study area, hence the variation in the tree biomass (fig 2&3). 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 reserve which intensify cutting down of indigenous trees in the forest reserves plummeting aboveground biomass and escalating carbon emissions in the atmosphere while jeopardizing the natural forest ecosystem services to the communities. Conservation education should be emphasized in the study area to local communities, exotic trees plantations owners and other relevant stakeholders.展开更多
文摘Sediment and macrobenthic fauna distribution at Dar es Salaam harbour channel were investigated to attest the influence of sediment grain size distribution and total organic carbon contents on benthic macrofauna dominance and diversity. Sampling campaign was conducted from January to April, 2019 in 25 sampling stations along the channel. Sediment grain sizes ranged between 0.7405 and 0.00273 mm with an average of 0.0804 mm classified as medium silt. Sediment distribution showed an onshore-offshore pattern consisting of fine dark clay-silt sediments in the southern part of the harbour close to Mwalimu Nyerere Bridge, medium (sandy) at the harbour and coarse sandy offshore. Five classes of macrofauna were identified with sedentary Polychaetes (Diopatra cuprea) found in tubes and free forms being dominant in most of the sediment types, however more abundant in clay-silt. High species diversity index values were encountered in sediments with medium total organic carbon (TOC) and sediment grain sizes (sand-silt). Apparently, low species similarity indices were observed in all sediment type indicating significant dissimilarities in species composition among sediment grain sizes. Thus, the distribution of benthic macrofauna species along Dar es Salaam harbour channel is strongly influenced by the sediment grain sizes and organic carbon contents in sediments.
文摘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 (Ensslin et al, 2015). The relationships between diversity, biomass and C stocks at varied altitudes can have crucial implications for the management and conservation of C sinks. The study was conducted at Mbeya One ward lying between Mporoto and Rungwe forest reserves 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 findings indicated the significant decreased in indigenous trees biomass in residential and crop land areas with a hasty increase in biomass when reaching Mporoto forest reserve indicating little human encroachment in the forest reserve. There was the same trend towards Rungwe forest reserve however in that side, there was a slight increase in indigenous tree biomass when reaching forest reserve which is the sign of human encroachment in the forest reserve. The main human activities encroaching the reserve were;timber harvesting and commercial exotic trees planting (especially the commercial trees, Pinus patula sp). However, the trend was opposite for the exotic trees especially for Pinus patula and Eucalyptus sp in the study area. Hence the study concludes that there is a significant variation between indigenous and exotic trees in the study area, hence the variation in the tree biomass (fig 2&3). 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 reserve which intensify cutting down of indigenous trees in the forest reserves plummeting aboveground biomass and escalating carbon emissions in the atmosphere while jeopardizing the natural forest ecosystem services to the communities. Conservation education should be emphasized in the study area to local communities, exotic trees plantations owners and other relevant stakeholders.
