Soil quality and aggregation in runoff water harvesting forestry systems in the semi-arid Israeli Negev I. Stavi a, ⁎, E. Argaman b a Dead Sea & Arava Science Center, Yotvata 88820, Israel b Soil Erosion Research Station, Ministry of Agriculture & Rural Development, P.O.B. 30, Bet Dagan 50250, Israel abstract article info Article history: Received 30 May 2015 Received in revised form 6 June 2016 Accepted 7 June 2016 Available online 15 June 2016 Water availability is a major limiting factor for dryland afforestation. Earthworks that modify natural landforms for the formation of runoff harvesting systems are prevalent in the Israeli drylands, with the aim of establishing afforestation projects. However, serious concerns alarm that such earthworks have detrimental effects on the geo-ecosystem functioning. Therefore, the objective of this study was to examine the impact of the establishment of contour bench terrace (also called shichs/shychs/shikim) runoff harvesting systems on selected soil properties, with particular focus on soil aggregation. Thus, we assessed the effect of the establishment of contour bench ter- races in a multi-aged forestry land, comprised of 2-year-old and 9-year-old afforestation areas, and compared them to ‘natural’ hillslopes as a reference treatment. The study was implemented in the Ambassadors' Forest, lo- cated in the semi-arid northern Negev of Israel, where we sampled the surface soil (at a depth of 0–5 cm) in north- and south-facing hillslopes. Considerable differences were recorded for the afforestation systems between the source (inter-terrace area) and sink (terrace-bottoms) areas. Data normalizing according to the relative cover percentage of the terraces and inter-terrace areas showed that the mean values of mean weight diameter (MWD), stable aggregate content, and particulate organic carbon in the natural hillslopes were 1.4%, 32.4%, and 20%, respectively, greater than in the 9-year-old afforestation systems, and 12.1%, 28.9%, and 31%, respective- ly, greater than in the 2-year-old systems. Means of clod content, aggregate slaking index, and clay dispersion index in the natural hillslopes were 62.3%, ~twofold, and 35.0%, respectively, smaller than in the 9-year-old sys- tems, and almost threefold, nearly twofold, and 46.2%, respectively, smaller than in the 2-year-old areas. The soil calcium carbonate content was similar in soils of the natural hillslopes and 9-year-old afforestation lands, which was ~17% smaller than in the 2-year-old afforestation systems. Considerable differences among the land-uses were also recorded for the soil texture. Mean coarse root biomass, despite revealing only a marginally-significant effect (p-value = 0.0765), was 40.0% greater in the natural hillslopes than in the 9-year-old systems, and more than twofold greater than in the 2-year-old systems. Hillslope aspect affected some of the measured properties, revealing only slightly better soil conditions in the (mesic) north- than in the (xeric) south-aspects. The data re- vealed that forestry-related earthworks degrade the soil quality and geo-ecosystem functioning in the short term. Yet, despite some discrepancies, the data also showed the occurrence of self-restoration processes of the geo-eco- system over the long term. © 2016 Elsevier B.V. All rights reserved. Keywords: Contour-ridge systems Land degradation and desertification Land-use change Net primary productivity Reclamation projects Soil erosion control 1. Introduction Forestry projects have been prevalent as cost-effective and environ- mentally-sound means in the restoration of degraded lands. Particular- ly, afforestation projects have covered extensive drylands around the world, aimed at restoring terrestrial ecosystems and controlling soil erosion (Ryan et al., 2002). In addition, forestry projects have been shown to provide additional ecosystem services, such as sustaining spe- cies diversity (Ginsberg, 2002), increasing carbon sequestration (Tal and Gordon, 2010), and affording recreational activities (Ginsberg, 2002). In the semi-arid northern and western Negev regions of Israel, the earliest afforestation efforts date back to the 1950's and 1960's, when the national forestry agency – the Keren Kayemet Le'Israel (KKL/also known internationally as JNF) – established the first forestry projects, aimed at combating desertification of the southern parts of the state. Since then, the afforested lands have covered extensive areas, of which their landforms have been mainly comprised of moderate hillslopes, and to a lesser extent, also valleys. The earliest forestry pro- jects were comprised of relatively simple practices, of which most were uni-species forests of Pinus halepensis (Miller) and Pinus brutia Catena 146 (2016) 88–93 ⁎ Corresponding author. E-mail addresses: istavi@adssc.org, istavi@yahoo.com (I. Stavi). http://dx.doi.org/10.1016/j.catena.2016.06.010 0341-8162/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Catena journal homepage: www.elsevier.com/locate/catena