Research Repository :: Browsing by Author "Becker, M."

Browsing by Author "Becker, M."

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Aerial Imagery for Monitoring Land Use in East African Wetland Ecosystems
(IEEE, 2009) Franke, Jonas; Becker, M.; Menz, Gunter; Misana, Salome B.; Mwita, Emiliana J.; Nienkemper, Pamela
Anthropogenic pressure and environmental change processes are key drivers of the recent intensification in the agricultural use of East African wetlands. Land shortage and degradation of upland areas as well as climate change effects turn wetland ecosystems into focal points of production by commercial and traditional users, entailing rapid wetland use changes and, in some instances, severe wetland degradation. An ecosystem inventory by mapping land cover and monitoring land use changes with remote sensing improves our understanding of change processes in wetlands and will contribute to the provision of decision support for sustainable use of wetland ecosystems. However, the spatial resolution of satellite systems is often too coarse to derive land use information at the plot level. In particular, small wetlands often exhibit abrupt transitions into different types of land use and landscape elements. Hence, monitoring of small wetlands requires spatially high-resolution remote sensing data, accounting for the prevailing small-scale diversity in land use. High-resolution aerial imagery, which is not available for most parts of East Africa, may provide information of wetland use/change at the required plot-level scale. Therefore, image acquisition campaigns over Kenyan and Tanzanian wetlands were realized with a common Nikon D-200 in September 2008 and February 2009, respectively. A comprehensive geo-referenced image data set that displays land use units at the plot level was obtained, used to discriminate various land cover types. Land cover/-land use maps can be derived that reveal land use trends fundamental for providing decision support for a sustainable wetland use.
Classification, Characterisation, and Use of Small Wetlands in East Africa
(Springer Link, 2011) Sakana, Naomi; Alvarez, Miguel; Becker, M.; Boehme, Beate; Handa, Collins; Kamiri, Wangechi; Langensiepen, Matthias; Menz, Gunter; Misana, Salome B.; Mogha, Neema G.; Möseler, Bodo M.; Mwita, Emiliana J.; Oyieke, Helida; Van Wijk, Mark
Small wetlands in Kenya and Tanzania cover about 12 million ha and are increasingly converted for agricultural production. There is a need to provide guide-lines for their future protection or use, requiring their systematic classification and characterisation. Fifty-one wetlands were inventoried in 2008 in four contrasting sites, covering a surveyed total area of 484 km 2 . Each wetland was subdivided into sub-units of 0.5–458 ha based on the predominant land use. The biophysical and socio-economic attributes of the resulting 157 wetland sub-units were determined. The wetland sub-units were categorized using multivariate analyses into five major cluster groups. The main wetland categories comprised: (1) narrow permanent-ly flooded inland valleys that are largely unused; (2) wide permanently flooded inland valleys and highlands flood-plains under extensive use; (3) large inland valleys and lowland floodplains with seasonal flooding under medium use intensity; (4) completely drained wide inland valleys and highlands floodplains under intensive food crop production; and (5) narrow drained inland valleys under permanent horticultural production. The wetland types were associated with specific vegetation forms and soil attributes.
Floristic Classification of the Vegetation in Small Wetlands of Kenya and Tanzania
(2012) Alvarez, Miguel; Becker, M.; Boehme, Beate; Handa, Collins; Josko, Matthias; Kamiri, Hellen W.; Langensiepen, Matthias; Menz, Gunter; Misana, Salome B.; Mogha, Neema G.; Möseler, Bodo M.; Mwita, Emiliana J.; Oyieke, Helida A.; Sakané, Nomé
Small wetlands in East Africa are increasingly converted into sites for agricultural production. The resulting changes in land use and cropping systems will impact on the wetlands’ vegetation. We characterized the plant communities in four wetlands of Kenya and Tanzania, each comprising four types of land use differentiated by the degree of anthropogenic disturbance (cropland, fallow, grazing land and unused). Since no syntaxonomical scheme was available as a reference, a first classification of vegetation units and the identification of diagnostic species is proposed. We collected 207 relevés in the representative wetlands in relation to the current land uses. The plant communities were determined using a modified TWINSPAN classification. For each vegetation unit, diagnostic species were selected according to their fidelity index (phi coefficient). Floristic relationships between vegetation units were surveyed by nMDS ordination analyses. We identified 15 plant communities and selected 147 diagnostic species. The communities were differentiated into (1) semi-natural wetland vegetation (associated with less disturbed environments), (2) grassland and fallow vegetation, and (3) weed communities (associated with eu-hemerobic, drained and cultivated cropland). While the semi-natural vegetation was distinctly matched with unused fields, the differential matching of the other plant communities with land use types was less clear. According to the floristic similarity, the weed communities associated with cropland tended to be aggregated in the nMDS configuration while the semi-natural vegetation was dispersed. The results of the ordination did not differ when involving all species or only the selected diagnostic ones. As the plant communities described are rankless syntaxa, the establishment of a comprehensive syntaxonomic classification for African wetlands will require further vegetation surveys as well as their comparison with published data.
Mapping Small Wetlands of Kenya and Tanzania Using Remote Sensing Techniques
(Elsevier, 2013) Mwita, Emiliana J.; Menz, Gunter; Misana, Salome B.; Becker, M.; Kisanga, Danielson; Boehme, Beate
Although wetlands in Tanzania and Kenya have great potentials for agricultural production and a multitude of uses, many of them are not even documented on official maps. Lack of official recognition has done little in preventing there over utilization. As the wetlands continue to play remarkable roles in the movement of people and terrestrial species in the region, it is important that they are monitored and properly managed. This study was undertaken in Usambara highlands and the Pangani floodplain in Tanzania, the Mount Kenya highlands and Laikipia floodplain in Kenya to map the different types of wetlands in terms of their size, density, spatial distribution and use patterns. Remote sensing techniques and field surveys were adopted, and 51 wetlands were identified in flood plains within the semi-arid and sub-humid lowlands, and inland valleys in the region. The detailed maps generated showed the intensity of wetland use, inland valleys being the most intensively used, and are useful in monitoring changes in wetlands for their effective management. The use of multispatial resolution imagery, combined with field survey and GIS produced satisfactory results for the delineation and mapping of small wetlands and their uses
Mapping Small Wetlands of Kenya and Tanzania Using Remote Sensing Techniques
(Elsevier, 2013) Mwita, Emiliana J.; Menz, Gunter; Misana, Salome B.; Becker, M.; Kisanga, Danielson; Boehme, Beate
Although wetlands in Tanzania and Kenya have great potentials for agricultural production and a mul-titude of uses, many of them are not even documented on official maps. Lack of official recognition has done little in preventing there over utilization. As the wetlands continue to play remarkable roles in the movement of people and terrestrial species in the region, it is important that they are monitored and properly managed. This study was undertaken in Usambara highlands and the Pangani floodplain in Tanzania, the Mount Kenya highlands and Laikipia floodplain in Kenya to map the different types of wetlands in terms of their size, density, spatial distribution and use patterns. Remote sensing techniques and field surveys were adopted, and 51 wetlands were identified in flood plains within the semi-arid and sub-humid lowlands, and inland valleys in the region. The detailed maps generated showed the intensity of wetland use, inland valleys being the most intensively used, and are useful in monitoring changes in wetlands for their effective management. The use of multispatial resolution imagery, combined with field survey and GIS produced satisfactory results for the delineation and mapping of small wetlands and their uses.
Seasonal Vegetation Changes in the Malinda Wetland Using Bi-Temporal, Multi-Sensor, Very High Resolution Remote Sensing Data Sets
(Scientific Research, 2014) Kuria, David N.; Menz, Gunter; Misana, Salome B.; Mwita, Emiliana; Thamm, Hans P.; Alvarez, Miguel; Mogha, Neema; Becker, M.; Oyieke, Helida
Small wetlands in East Africa have grown in prominence driven by the unreliable and diminished rains and the increasing population pressure. Due to their size (less than 500 Ha), these wetlands have not been studied extensively using satellite remote sensing approaches. High spatial resolu- tion remote sensing approaches overcome this limitation allowing detailed inventorying and re- search on such small wetlands. For understanding the seasonal variations in land cover within the Malinda Wetland in Tanzania (350 Ha), two periods were considered, May 2012 coinciding with the wet period (rainy season) and August 2012 coinciding with a fairly rain depressed period (substantially dry but generally cooler season). The wetland was studied using very high spatial resolution orthophotos derived from Unmanned Aerial Vehicle (UAV) photography fused with TerraSAR-X Spotlight mode dual polarized radar data. Using these fused datasets, five main classes were identified that were used to firstly delineate seasonal changes in land use activities and secondly used in determining phenology changes. Combining fuzzy maximum likelihood clas- sification, knowledge classifier and Change Vector Analysis (CVA), land cover classification was undertaken for both seasons. From the results, manifold anthropogenic activities are taking place between the seasons as evidenced by the high conversion rates (63.01 Ha). The phenological change was also highest within the human influence class due to the growing process of cropped land (26.60 Ha). Much of the changes in both cover and phenology are occurring in the mid upper portion of the wetland, attributed to the presence of springs in this portion of the wetland along the banks of River Mkomazi. There is thus seasonality in the observed anthropogenic influence between the wetland and its periphery.
Seasonal Vegetation Changes in the Malinda Wetland Using Bi-Temporal, Multi-Sensor, Very High Resolution Remote Sensing Data Sets
(2014-03) Kuria, David N.; Menz, Gunter; Misana, Salome; Mwita, Emiliana; Thamm, Hans P.; Alvarez, Miguel; Mogha, Neema; Becker, M.; Oyieke, Helida
Small wetlands in East Africa have grown in prominence driven by the unreliable and diminished rains and the increasing population pressure. Due to their size (less than 500 Ha), these wetlands have not been studied extensively using satellite remote sensing approaches. High spatial resolu-tion remote sensing approaches overcome this limitation allowing detailed inventorying and re-search on such small wetlands. For understanding the seasonal variations in land cover within the Malinda Wetland in Tanzania (350 Ha), two periods were considered, May 2012 coinciding with the wet period (rainy season) and August 2012 coinciding with a fairly rain depressed period (substantially dry but generally cooler season). The wetland was studied using very high spatial resolution orthophotos derived from Unmanned Aerial Vehicle (UAV) photography fused with TerraSAR-X Spotlight mode dual polarized radar data. Using these fused datasets, five main classes were identified that were used to firstly delineate seasonal changes in land use activities and secondly used in determining phenology changes. Combining fuzzy maximum likelihood classification, knowledge classifier and Change Vector Analysis (CVA), land cover classification was undertaken for both seasons. From the results, manifold anthropogenic activities are taking place between the seasons as evidenced by the high conversion rates (63.01 Ha). The phenological change was also highest within the human influence class due to the growing process of cropped land (26.60 Ha). Much of the changes in both cover and phenology are occurring in the mid upper portion of the wetland, attributed to the presence of springs in this portion of the wetland along the banks of River Mkomazi. There is thus seasonality in the observed anthropogenic influence between the wetland and its periphery.
SWEA-Dataveg – Vegetation of Small Eetlands in East Africa
(2015) Alvarez, Miguel; Möseler, Bodo M.; Josko, Matthias; Becker, M.; Langensiepen, Matthias; Menz, Gunter; Boehme, Beate; Oyieke, Helida; Handa, Collins; Kamiri, Wangechi; Misana, Salome B.; Mwita, Emiliana J.; Mogha, Neema G.; Sakana, Naomi
SWEA (agricultural use and vulnerability of small wetlands in East Africa) is a multidisciplinary project which task is to evaluate the effects of land use on the ecological and socio-economical functions of small wetlands in Kenya and Tanzania. In order to allow the availability of the collected data for further studies we stored them into SWEA-Dataveg (GIVD ID AF-00-006), a database stored in Microsoft Access (mdb-format). Because this project is dealing not only with vegetation science but also with geography, soil science, hydrology and socio-economy, the database also contains information related to these research fields. Additionally, some functional traits of the plant species occurring in the relevés are included in the species list. The sampling areas are concentrated in four localities, two of them in Kenya (Karatina and Rumuruti) and two in Tanzania (Malinda and Lukozi). The vegetation ecology group is dealing in the project with the classification of the vegetation according to species composition, the correlation of plant communities with environmental factors and land uses, and the survey of potential indicator species for the determination of the resilience of wetlands. Once finished the storage, we are considering an adaptation of SWEA-Dataveg into a TURBOVEG-format as well as its extension to further projects (e.g. SWEA phase II) and relevés collected from publications.
The Use of UAS for Assessing Agricultural Systems in AN Wetland in Tanzania in the Dry- and Wet-Season for Sustainable Agriculture and Providing Ground Truth for Terra-SAR X Data
(2013) Thamm, Hans P.; Menz, Gunter; Becker, M.; Kuria, David N.; Misana, Salome B.; Kohn, D.
The paper describes the assessment of the vegetation and the land use systems of the Malinda Wetland in the Usambara Mountains in Tanzania with the parachute UAS (unmanned aerial system) SUSI 62. The area of investigation was around 8 km2. In two campaigns, one in the wet season and one in the dry season, approximately 2600 aerial photos of the wetland were taken using the parachute UAS SUSI 62; of these images, ortho-photos with a spatial resolution of 20 cm × 20 cm, were computed with an advanced block bundle approach. The block bundles were geo-referenced using control points taken with differential GPS. As well a digital surface model (DSM) of the wetland was created out of the UAS photos. Using the ortho-photos it is possible to assess the different land use systems; the differences in the phenology of the vegetation between wet and dry season can be investigated. In addition, the regionalisation of bio mass samples on smaller test plots was possible. The ortho-photos and the DSM derived from the UAS proved to be a valuable ground truth for the interpretation of Terra-SAR X images. The campaigns demonstrated that SUSI 62 was a suitable, robust tool to obtain the valuable information under harsh conditions.

Browsing by Author "Becker, M."

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