Land Use Policy 64 (2017) 95–100 Contents lists available at ScienceDirect Land Use Policy j o ur na l ho me page: www.elsevier.com/locate/landusepol Implications of land use transitions on soil nitrogen in dynamic landscapes in Tanzania Mercy M. Ojoyi a,b , Onisimo Mutanga a , John Odindi a , Jean-Marc Mwenge Kahinda c , Elfatih M. Abdel-Rahman a,d,∗ a University of KwaZulu-Natal, Private Bag X01, Scottsville, Pietermaritzburg, 3209, South Africa b Governance of Africa’s Resources Programme (GARP), South African Institute of International Affairs, 33 Church Street, Vunani Chambers, Cape Town, 8001, South Africa c Council for Scientific and Industrial Research, P.O. Box 395, Pretoria, 0001, South Africa d Department of Agronomy, Faculty of Agriculture, University of Khartoum, Khartoum North 13314, Sudan a r t i c l e i n f o Article history: Received 1 June 2016 Received in revised form 15 February 2017 Accepted 16 February 2017 Keywords: Land use Dynamics Soil Nitrogen Remote sensing Impact a b s t r a c t Land use transitions are rated among the leading sources of greenhouse gas emissions in the tropics. They significantly challenge the functioning of ecosystems and affect multi-temporal stability of green- house gases such as N 2 O and soil properties. Studies on dynamics in nitrogen balances are essential in understanding greenhouse gas emissions such as N 2 O and to manage their impacts on productivity. In this study, multi-temporal Landsat images (1975, 1995 and 2012) were classified to determine land use transitions and potential drivers. The classified images were categorized into degraded and non-degraded lands and eighty sampling plots generated within the entire study area. Soil samples were then collected at 0–15, 15–30 and 30–60 cm depths on each plot and soil nitrogen determined. A regression analysis was developed to determine the influence of forest and grassland degradation on soil nitrogen. Results indicated a significant change in major land use and land cover types. Specifically, there was a decrease in areas covered by forests, woodland and grassland, however, area covered by less dense forest increased. Results also indicated variability in mean nitrogen content between degraded and non-degraded areas and depths. Furthermore, levels of degradation influence nitrogen content up to a soil depth of 30 cm. The present study is relevant in the detailed assessment of the extent of damage and threats posed to biodiversity hotspots in sub-Saharan Africa. These results are transferable to other parts of the world characterized by dynamic ecological transformation. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Terrestrial forest ecosystems occupy more than a fifth of Africa’s land area (UNEP, 2008). The continent, which saw a net loss of approximately 4.1 million hectares of forests per year in the 1990s, reported a further average net loss of about 3.4 million hectares per year between 2000 and 2010 (FAO, 2010). These losses are mainly attributed to population growth and associated demand for ecolog- ical resources (Henzen, 2008). The ever increasing human pressure on land has led to an increase in the urgency to assess effects of land use on soil (Islam and Weil, 2000). Land use transitions, which refer to spatio-temporal land use morphology of a region ∗ Corresponding author at: Department of Agronomy, Faculty of Agriculture, Uni- versity of Khartoum, Khartoum North 13314, Sudan. E-mail address: elfatihabdelrahman@gmail.com (E.M. Abdel-Rahman). due anthropogenic impacts, affect ecosystem support services and conservation efforts (Long et al., 2014; Polasky et al., 2011). Accord- ing to Maitima et al. (2009), alteration of natural landscapes due to land use transformations influence ecosystem functioning, veg- etation structure and biodiversity while Gude et al. (2007) note that land use transformations affect ecological parameters like species composition and densities. The modification of landscapes into other land uses interferes with environmental quality (Don et al., 2011); changes the climatic and hydrological systems and bio-geochemical cycles (Reyers et al., 2009; Ward and Robinson, 1990). Furthermore, landscape modification affects the quality, size and ecological functioning of ecosystems, leading to changes in the composition of structural habitat entities, spatial characteristics and habitat organization (Wilson et al., 2004). These pose serious threats to the ecosystems ecological integrity (Foley et al., 2005). As aforementioned, increased rural settlements, commonly accompa- nied by creation of new farmlands for instance leads to habitat loss http://dx.doi.org/10.1016/j.landusepol.2017.02.023 0264-8377/© 2017 Elsevier Ltd. All rights reserved.