Landscape fragmentation and soil cover changes on south- and north-facing slopes during ecosystems recovery: an analysis from multi-date air photographs Maxim Shoshany * Remote Sensing and GIS Laboratory, Geography Department, Bar-Ilan University, 52900 Ramat Gan, Israel Received 28 November 1999; received in revised form 3 March 2001; accepted 14 October 2001 Abstract A quantitative analysis is presented, of soil and vegetation patch patterns from air photographs of three dates (1956, 1976 and 1990). Relationships between changes in soil cover and landscape fragmentation are assessed for north- and south-facing slope units in the semi-arid zone of Israel undergoing recovery following severe overgrazing and woodcutting phases. Soil loss accompanied by an increase in rock fragment exposure, and an increase in soil erodibility due to a decrease in aggregate size and organic matter content are the two main characteristics of soil changes in this area. Changes in both of these characteristics are highly correlated with soil brightness properties as recorded from aerial photographs. The methodology developed combines image processing techniques, enabling differentiation between soil and vegetation patches, with raster Geographical Information Systems (GIS) techniques, allowing patch distribution, fragmentation and form to be analyzed. Expansion of vegetation patches and contraction of soil patches were found to follow similar lines of spatial pattern evolution when parameterized according to their size, form and density. Assessment of temporal changes in soil and vegetation patch composition indicated that there is a phase difference of 12 years between the processes taking place on the two slope units. Hypothetical descriptions of soil patch fragmentation and vegetation patch expansion processes between 1920 and 2010 were formulated following the analysis of data between 1956 and 1990. Evidence of soil brightness changes provided indications for the continuation of soil loss, mainly in large patches (a few thousands of square meters in size) undergoing relatively slow fragmentation. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Aerial photography; GIS; Landscape fragmentation; Image processing; Patch patterns; Soil erosion 1. Introduction Studies of land degradation in Mediterranean regions have attracted wide scientific attention (see, for example, Thornes, 1990; Perez-Trejo, 1994; Yasso- glou, 1996) due to its climatic, geomorphic and anthro- pogenic consequences. However, there is relatively little knowledge regarding eco-geomorphic changes taking place during recovery processes following eco- system disturbance (Turner et al., 1993; Baker, 1995). The evolution of soil – vegetation patterns and their geomorphological implications have been investigated in numerous studies (see, for example, Morrison et al., 1948; Puigdefa ´bregas and Sa ´nchez, 1996; Valentin et 0169-555X/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0169-555X(01)00186-6 * Department of Geography School of Humanities, King’s College, Strand Campus, WC2R 2R1S, London, UK. E-mail address: shosham1@inter.net.il (M. Shoshany). www.elsevier.com/locate/geomorph Geomorphology 45 (2002) 3 – 20