TY - JOUR A1 - Milewski, Robert A1 - Chabrillat, Sabine A1 - Brell, Maximillian A1 - Schleicher, Anja Maria A1 - Guanter, Luis T1 - Assessment of the 1.75μm absorption feature for gypsum estimation using laboratory, air- and spaceborne hyperspectral sensors JF - International Journal of Applied Earth Observation and Geoinformation N2 - High spectral resolution (hyperspectral) remote sensing has already demonstrated its capabilities for soil constituent mapping based on absorption feature parameters. This paper tests different parametrizations of the 1.75 μm gypsum feature for the determination of gypsum abundances, from the laboratory to remote sensing applications of recent as well as upcoming hyperspectral sensors. In particular, this study focuses on remote sensing imagery over the large body of the Omongwa pan located in the Namibian Kalahari. Four common absorption feature parameters are compared: band ratio through the introduction of the Normalized Differenced Gypsum Index (NDGI), the shape-based parameters Slope, and Half-Area, and the Continuum Removed Absorption Depth (CRAD). On laboratory soil samples from the pan, CRAD and NDGI approaches perform best to determine gypsum content tested in cross validated regression models with XRD mineralogical data (R² = 0.84 for NDGI and R² = 0.86 for CRAD). Subsequently the laboratory prediction functions are transferred to remote sensing imagery of spaceborne Hyperion, airborne HySpex and simulated spaceborne EnMAP sensor. Variable results were obtained depending on sensor characteristics, data quality, preprocessing and spectral parameters. Overall, the CRAD parameter in this wavelength region proved not to be robust for remote sensing applications, and the simple band ratio based parameter, the NDGI, proved robust and is recommended for future use for the determination of gypsum content in bare soils based on remote sensing hyperspectral imagery. KW - Hyperspectral KW - Gypsum quantification KW - Salt pan KW - Absorption feature parameters KW - Namibia Y1 - 2017 U6 - https://doi.org/10.1016/j.jag.2018.12.012 SN - 0303-2434 VL - 77 SP - 69 EP - 83 PB - Elsevier Science CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Tabares, Ximena A1 - Mapani, Benjamin A1 - Blaum, Niels A1 - Herzschuh, Ulrike T1 - Composition and diversity of vegetation and pollen spectra along gradients of grazing intensity and precipitation in southern Africa JF - Review of palaeobotany and palynology : an international journal N2 - Understanding vegetation-modern pollen relationships is essential to provide confidence in fossil pollen reconstructions of long-term vegetation changes in savanna ecosystems. In this paper we compare the taxonomical composition and the diversity (Hill NO, N1, N2) of vegetation and modern pollen along precipitation and local grazing-intensity gradients in Namibian savannas. Modern pollen was extracted from surface soil samples collected from 5 x 5 m plots distributed along four 500 m gradients. Vegetation was surveyed in each plot. The results show a high correspondence between vegetation and pollen data in terms of composition. Precipitation and grazing explain a significant although low proportion of compositional change in the vegetation and pollen spectra. We identified pollen taxa as indicators of grazing pressure such as Limeum, Alternanthera, and particularly Tribulus. Correspondence between vegetation and pollen data in terms of taxa richness (NO) is limited, probably because of the influence of landscape heterogeneity and openness, as well as low pollen concentrations. In contrast, the effective numbers of common and dominant taxa (N1, N2) are consistent among the different datasets. We conclude that in spite of limitations, modern pollen assemblages can reflect changes in vegetation composition, richness and diversity patterns along precipitation and grazing gradients in savanna environments. (C) 2018 Elsevier B.V. All rights reserved. KW - Modern pollen-vegetation relationships KW - Hill numbers KW - Indicator species KW - Savanna ecology KW - Namibia Y1 - 2018 U6 - https://doi.org/10.1016/j.revpalbo.2018.04.004 SN - 0034-6667 SN - 1879-0615 VL - 253 SP - 88 EP - 100 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Falk, Thomas A1 - Kirk, Michael A1 - Lohmann, Dirk A1 - Kruger, Bertus A1 - Hüttich, Christian A1 - Kamukuenjandje, Richard T1 - The profits of excludability and transferability in redistributive land reform in central Namibia JF - Development Southern Africa N2 - Policies which redistribute property rights to land can improve the well-being of rural households and can have overall growth effects. In many cases, however, land reforms are driven mainly by politically justified objectives. Under such circumstances, little emphasis is placed on whether and, if so, how property rights can increase productivity. Following 18 years of land reform implementation in Namibia, we evaluated 65 beneficiaries in Namibia. We assess to which degree land rights affects their farm income. The study focuses on Namibia’s two main commercial land reform instruments, namely the Farm Unit Resettlement Scheme and the Affirmative Action Loan Scheme. We find evidence that the majority of land reform projects are not profitable. Further, our study confirms the importance of the right to restrict land access compared with the right to transfer. The long-term leasehold contract seemingly provides sufficient incentives to make productive use of the land. KW - Redistributive land reform KW - property rights KW - farm productivity KW - pastoralism KW - Namibia Y1 - 2017 U6 - https://doi.org/10.1080/0376835X.2016.1269633 SN - 0376-835X SN - 1470-3637 VL - 34 SP - 314 EP - 329 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Falk, Thomas A1 - Lohmann, Dirk A1 - Azebaze, Nadege T1 - Congruence of appropriation and provision in collective water provision in Central Namibia JF - International journal of the commons N2 - Achieving cooperation in natural resource management is always a challenge when incentives exist for an individual to maximise her short term benefits at the cost of a group. We study a public good social dilemma in water infrastructure provision on land reform farms in Namibia. In the context of the Namibian land reform, arbitrarily mixed groups of livestock farmers have to share the operation and maintenance of water infrastructure. Typically, water is mainly used for livestock production, and livestock numbers are subject to high fluctuations due to the given environmental conditions. Our paper assesses how alternative payment systems with differing congruence of provision and appropriation support the cooperation in the group given the ever-changing equilibria. In a first step, we conducted an exploratory overview of the social-ecological system of central Namibian land reform projects. The Social Ecological System (SES) Framework served as a guideline for this assessment (Ostrom 2009). Taking the complexity of the cooperation situation into account, in the second step we designed a role-play that is based on a social-ecological simulation model. The role-play simulates the real-life decision situations of land reform beneficiaries wherein equilibria are permanently changing. This approach helped us to not only better understand the cooperation challenges of Namibian land reform beneficiaries, but also supported stakeholders in their decision making and institution building. Our study provides evidence to support that land reform beneficiaries increase their contributions as they own more livestock and as other group members increase their payments. Nevertheless, only groups with relatively homogeneous livestock endowments manage to agree on payment rules. Interestingly, the dominant rule is an "equal payment per farmer" and not a "payment per head of livestock", though the latter would imply a higher congruence of provision and appropriation. KW - Land reform KW - Namibia KW - participatory ecological-economic modelling KW - public good KW - role play KW - savanna rangeland Y1 - 2016 U6 - https://doi.org/10.18352/ijc.583 SN - 1875-0281 VL - 10 SP - 71 EP - 118 PB - Brill CY - Urtrecht ER -