Figure 1 - uploaded by Martin Karlson
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Map showing the Sudano-Sahelian zone defined as the area between the 200 mm and 1000 mm isohyets. The map was modified from the WorldClim dataset (Hijmans et al. 2005).
Source publication
Woodlands constitute the subsistence base of the majority of people in the Sudano-Sahelian zone (SSZ), but low availability of in situ data on vegetation structure and composition hampers research and monitoring. This thesis explores the utility of remote sensing for mapping and analysing vegetation, primarily trees, in the SSZ. A comprehensive lit...
Contexts in source publication
Context 1
... geographic focus of this thesis is on the African woodlands north of the Equator, the Sudano-Sahelian zone (SSZ), which stretches between the coasts of the Atlantic Ocean and the Red Sea (Figure 1). This is one of the poorest, most marginalized and technologically underdeveloped regions of world, ranking at the bottom of numerous global lists of life expectancies, per capita revenues, nutrition intake and other welfare indicators (Chidumayo and Gumbo 2010). ...
Context 2
... SZZ consists of two roughly parallel ecological regions (see Figure 1), the Sahel and the Sudan, which stretches across the African continent between 10°N and 20°N latitude and includes 17 sub-Saharan countries. The Sahel is located on the fringes of the Sahara desert and extends south covering the area that receives between 200 and 600 mm mean annual rainfall, whereas the Sudanian zone receives between 600 and 1000 mm mean annual rainfall and borders the Guinean zone to the south ( Nicholson 2013, Le Houerou 1980, Nicholson 1995). ...
Context 3
... shows that the three types of predictor variables bear partially independent information about the trees that is complimentary in the context of woodland tree cover mapping. In this study, the panchromatic band of Landsat 8 showed the strongest relationship to both TCC and AGB according to the RF variable importance ranking, followed by the homogeneity texture features calculated from the panchromatic band (see Paper IV: Figure 1-4). The other Landsat 8 bands (bands 2-7) were ranked low for both TCC and AGB. ...
Citations
... This confirms the importance of integrating spatiotemporal datasets of satellite remote sensing image classification, as demonstrated in prior studies. [81][82][83]. ...
Pakistan has an annual deforestation rate of 4.6% which is the second highest in Asia. It has been described by the Food and Agriculture Organization (FAO) that the deforestation rate increased from 1.8–2.2% within two decades (1980–2000 and 2000–2010). KPK (Khyber Pakhtunkhwa), Pakistan’s northwestern province, holds 31% of the country’s total forest resources, the majority of which are natural forests. The Malam Jabba region, known for its agro-forestry practices, has undergone significant changes in its agricultural, forestry, and urban development. Agricultural and built-up land increased by 77.6% in the last four decades, and significant changes in land cover especially loss in forest, woodland, and agricultural land were observed due to flood disasters since 1980. For assessing and interpreting land-cover dynamics, particularly for changes in natural resources such as evergreen forest cover, remote sensing images are valuable assets. This study proposes a framework to assess the changes in vegetation cover in the Malam Jabba region during the past four decades with Landsat time series data. The random forest classifier (RF) was used to analyze the forest, woodland, and other land cover changes over the past four decades. Landsat MMS, TM, ETM+, and OLI satellite images were used as inputs for the random forest (RF) classifier. The vegetation cover change for each period was calculated from the pixels using vegetation indices such as NDVI, SAVI, and VCI. The results show that Malam Jabba’s total forest land area in 1980 was about 236 km2 and shrank to 152 km2 by 2020. The overall loss rate of evergreen forests was 35.3 percent. The mean forest cover loss rate occurred at 2.1 km2/year from 1980 to 2020. The area of woodland forest decreased by 87 km2 (25.43 percent) between 1980 and 2020. Other landcover increased by 121% and covered a total area of 178 km2. The overall accuracy was about 94% and the value of the kappa coefficient was 0.92 for the change in forest and woodland cover. In conclusion, this study can be beneficial to researchers and decision makers who are enthusiastic about using remote sensing for monitoring and planning the development of LULC at the regional and global scales.
... The vegetation of the region is mainly composed of woody savanna and steppe [15] on sandy soils with low organic matter and nutrient content. Mean annual rainfall and soil nutrient content govern vegetation cover in the study area; consequently, vegetation growth occurs during the rainy season [16]. These characteristics make the presence of bare soil common in the study area during the dry season. ...
... A loop-based hyperparameter tuning strategy was applied to determine the best combination. Hence, we iteratively trained the model with a set of hyperparameter combinations, such as the number of filters (2,4,8,16, and 32), the batch size (2, 4, 8, 16, and 32), and the learning rate (10e-4, 5e-4, 10e-5, and 5e-5). Each model is trained for 250 epochs, while a model checkpoint strategy was used to save the weights associated with the lower validation loss. ...
In this letter, we propose a Deep Learning (DL) based approach which exploits multispectral Sentinel-2 open-source data and a small-size inventory to map artisanal and small-scale mines (ASM). The study area is in central northern Burkina Faso (Africa) and is characterized by a semi-desert environment that makes mapping challenging. In sub-Saharan Africa, artisanal and small-scale mining represents a source of subsistence for a significant number of individuals. However, because ASM are often illegal and uncontrolled, the materials employed in the excavation process are highly dangerous for the environment as well as for the lives of the people involved in the mining activities. One of the most important aspects regarding ASM is the record of their spatial location which, at the moment, is missing in most of the African regions. Performance evaluation of two state-of-art DL architectures (U-Net, and Attention Deep Supervised Multi-Scale U-Net - ADSMS U-Net) is provided, along with an in-depth analysis of the predictions when dealing with both dry and rainy seasons. The ADSMS U-Net architecture yields generally more accurate predictions than the basic U-Net allowing us to better discriminate ASM in such an environment. The findings show that the proposed approach can detect ASM in semi-desertic areas starting with a few samples at a low cost in terms of both human and financial resources.
... The in situ dataset from 2012 was collected between October and December within 76 plots (50 m × 50 m in dimensions), randomly distributed throughout the 100 km 2 test site and equally divided between three canopy cover classes, derived using the WorldView-2 image [15,20,48]. This resulted in a total of 1125 measured trees. ...
Mapping of tree height is of great importance for management, planning, and research related to agroforestry parklands in Africa. In this paper, we investigate the potential of spotlight-mode data from the interferometric synthetic aperture radar (InSAR) satellite system TanDEM-X (TDM) for mapping of tree height in Saponé, Burkina Faso, a test site characterised by a low average canopy cover (~15%) and a mean tree height of 9.0 m. Seven TDM acquisitions from January–April 2018 are used jointly to create high-resolution (~3 m) maps of interferometric phase height and mean canopy elevation, the latter derived using a new, model-based processing approach compensating for some effects of the side-looking geometry of SAR. Compared with phase height, mean canopy elevation provides a more accurate representation of tree height variations, a better tree positioning accuracy, and better tree height estimation performance when assessed using 915 trees inventoried in situ and representing 15 different species/genera. We observe and discuss two bias effects, and we use empirical models to compensate for these effects. The best-performing model using only TDM data provides tree height estimates with a standard error (SE) of 2.8 m (31% of the average height) and a correlation coefficient of 75%. The estimation performance is further improved when TDM height data are combined with in situ measurements; this is a promising result in view of future synergies with other remote sensing techniques or ground measurement-supported monitoring of well-known trees.
... The plant is of Sudano-Sahelian zone (Hedberg, and Edwards,1989;Polhill, 1966), which located between the Atlantic ocean and the Red sea with an annual rainfall, 200 to 600 mm in the Sahara desert region and 600 to 1000 mm in Sudanian zone (Karlson, 2015). ...
A new species of Celtis toka (Family Cannabaceae) from Faifa, Saudi Arabia is described and illustrated. Morphological descriptions with a distribution map and photograph of the species were provided. Celtis toka is only recorded from West and Middle of the Sahel region and East Tropical Africa to Yemen in Arabian Peninsula. This record conceded as the second locations for the Arabian Peninsula.
... (Carsan et al., 2012, Djuikouo et al., 2010. Species-specific wood densities were used for individuals identified to the species level (Karlson, 2015). In cases wherein species-specific wood densities were not available, mean values for the genus or family were used. ...
... (Carsan et al., 2012, Djuikouo et al., 2010. Species-specific wood densities were used for individuals identified to the species level (Karlson, 2015). In cases wherein species-specific wood densities were not available, mean values for the genus or family were used. ...
Tropical forests ecosystems remain the most diverse on the planet, and store considerable amounts of biomass and carbon. Despite the importance of tropical forests, sizable knowledge gaps exist regarding species diversity, plant biomass and carbon. These knowledge gaps are particularly large in tropical systems, and even more so in the African tropics. This study provides baseline data on species composition and vegetation structure, and evaluate variation along elevational gradient transecting of four elevation-forest types: lowland, mid-elevation, sub-montane and montane forest in the Rumpi Hills Forest Reserve of Cameroon. We collected data on tree species diversity, above-ground biomass and carbon in 25 1-ha plots sampled in 500 m long x 20 m width transect. Results revealed high species diversity, particularly in lowland forest. Overall, the study enumerated 12,037 individuals (trees ≥ 10 cm dbh) of 441 species. The mean species per plot decreased with increasing elevation, 112 in lowland, 81 in mid-elevation, 60 in submontane and 38 in montane forest. Above-ground carbon averaged 162.88±50 t ha-1. We found the greatest carbon storage and tree and liana species diversity at low elevations. Our results indicate that high species diversity and occurrence of larger tree species are more important in carbon storage in lowland forest than at higher elevations. These findings are useful for management and land use planning of the forests in the Rumpi Hills Forest Reserve.
... Agroforestry can also be applied to enhance biomass production, stabilize soil or conserve water in natural vegetation or human-made productions systems, such as parklands. Parklands as traditional multifunctional land-use systems exist throughout the Sudano-Sahelian part of Africa (Karlson 2015) and are the setting for our chapter (Sanou Chapter 3) on shea production (the nut from the tree Vitellaria paradoxa) in Burkina Faso (Figure 1.1). In these systems, the regular production of one or more agricultural crops is supported by scattered trees that supply additional products such as fodder, fruits or fuel wood while enhancing crop productivity through improved water retention, soil structure and fertility. ...
