Browsing by Author "Mauya, E"

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Combining airborne laser scanning and Landsat data for statistical modeling of soil carbon and tree biomass in Tanzanian Miombo woodlands
(Springer Open, 2017-04-17) Egberth, M.; Nyberg, G.; Næsset, E.; Gobakken, T.; Mauya, E; Malimbwi, R.; Katani, J.; Chamuya, N.; Bulenga, G.; Olsson, H.
Background: Soil carbon and biomass depletion can be used to identify and quantify degraded soils, and by using remote sensing, there is potential to map soil conditions over large areas. Landsat 8 Operational Land Imager satellite data and airborne laser scanning data were evaluated separately and in combination for modeling soil organic carbon, above ground tree biomass and below ground tree biomass. The test site is situated in the Liwale district in southeastern Tanzania and is dominated by Miombo woodlands. Tree data from 15 m radius field-surveyed plots and samples of soil carbon down to a depth of 30 cm were used as reference data for tree biomass and soil carbon estimations. Results: Cross-validated plot level error (RMSE) for predicting soil organic carbon was 28% using only Landsat 8, 26% using laser only, and 23% for the combination of the two. The plot level error for above ground tree biomass was 66% when using only Landsat 8, 50% for laser and 49% for the combination of Landsat 8 and laser data. Results for below ground tree biomass were similar to above ground biomass. Additionally it was found that an early dry season satellite image was preferable for modelling biomass while images from later in the dry season were better for modelling soil carbon. Conclusion: The results show that laser data is superior to Landsat 8 when predicting both soil carbon and biomass above and below ground in landscapes dominated by Miombo woodlands. Furthermore, the combination of laser data and Landsat data were marginally better than using laser data only.
Rotation age and fibre length of pinus patula at sao hill forest plantation, Tanzania
(Tanzania Forestry Research Institute (TAFORI) and Tanzania Forest Fund (TaFF), 2018) Laswai, F; Malimbwi, R.E; Chamshama, S.A.O; Abdallah, J.M; Balama, C.; Pima, N.E; Mugasha, W.A; Mauya, E
This study determined the rotation age of Pinus patula grown at Sao Hill forest plantation based on growth, yield, wood properties, and economic analysis. Previous Technical Orders on rotation age were not based on these considerations. Growth, yield, wood properties, revenue, and management costs data were collected and analysed using standard procedures. The results indicate that there were fewer and lighter prunings and thinnings than specified in the respective schedules. Many trees were found to have breast height diameter below 40 cm in all compartments except one. Growth and yield results showed that for P. patula grown at Sao Hill, the equity point of Mean Annual Increment (MAI) and Current Annual Increment (CAI) were achieved at between 16 and 17 years with the maximum MAI being maintained until about 20 years. Basic density and mechanical properties showed that strong wood was obtained when trees were 16 years and above and these properties increased with age. The mean fibre length for 5 - 25 years old P. patula was found to range from 2.29 to 3.53 mm and increased with age. Fibre lengths from 11 years and above exceed the minimum (3 mm) considered suitable for pulp and paper production. Based on economic analysis, net present value (NPV) was attained at between 16 and 17 years. Based on considerations of growth and yield, wood properties and economics of rotation age; P. patula from Sao Hill is recommended to be harvested at 18 years for timber and 11 years for pulp and paper production.
Stump diameter : a potential predictor of removed biomass through tree cutting
(Tanzania Journal of Forestry and Nature Conservation, 2021) Mugasha, W.A; Mauya, E; Karlsson, K; Malimbwi, R.E.
Stump diameter (SD) has been rarely considered as an important tree parameter in forestry. It is until recently that SD has been found to be important predictor of tree diameter at breast height (D) and forest stand parameter such as volume and biomass. This study, developed D-SD relationships for nine different forest cover type in Tanzania mainland. A total of 32265 sample trees covering miombo woodlands, humid montane, lowland forests, bushlands, grasslands, mangroves, cultivated land, wetlands forests and plantations (Pines and Eucalyptus species) were used for fitting D-SD models. The findings revealed a linear relationship between D and SD for all forest covers. In addition, we found forest covers having similar D-SD allometry while others had unique D-SD allometry. This prompted fitting Generalised Linear Model where three forest cover groups were generated, i.e. group 1 (bushlands, woodlands, lowlands and grasslands); group 2 (mangroves, cultivated land, plantation and wetlands); and group 3 (humid montane). We fitted linear model to each forest cover group. Large variations in D were adequately explained by SD for each forest cover group. We further compared AGB values estimated from the measured D and estimated D from the D-SD equation. The estimated AGB from both approach did not differ significantly. We therefore, recommend the developed D-SD relationships models be applied to predict D of the missing trees for which their stumps still exist.