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Stavi I, Islam KR, Rahman MA, Gusarov Y, Laham J, Comay O, Basson U, Xu C, Xu Z, Argaman E. Unexpected consequences of afforestation in degraded drylands: Divergent impacts on soil and vegetation. J Environ Manage 2023; 345:118703. [PMID: 37540983 DOI: 10.1016/j.jenvman.2023.118703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 07/09/2023] [Accepted: 07/26/2023] [Indexed: 08/06/2023]
Abstract
Forestry has long been considered an effective means of restoring degraded drylands worldwide. Often, afforestation in such lands relies on the establishment of runoff harvesting systems that are formed as contour bench terraces on hillslopes, increasing water availability for the planted trees and shrubs. The construction of terraces requires intensive earthworks by heavy machinery. This study assessed the long-term (>10 yrs) effects of forestry-related land-use change on soil properties and herbaceous vegetation in 16-year-old and 12-year-old afforestation sites (established in 2005 and 2009), and in nearby control ("natural") areas in the semi-arid northern Negev, Israel. Mean herbaceous vegetation height in the 2005 afforestation sites (12.1 cm) was significantly (P = 0.0009) and 23% greater than in the control areas (9.8 cm), whereas in the 2009 afforestation sites (6.2 cm) it was 37% lesser than in the control areas. Mean herbaceous vegetation aboveground biomass was similar in the 2005 afforestation (0.39 Mg ha-1) and control areas (0.38 Mg ha-1), and almost significantly (P = 0.0510) and twofold greater than in the 2009 afforestation sites (0.19 Mg ha-1). The effect of hillslope aspect on these variables was substantial; their mean values were higher in the northern (mesic) hillslopes than in the southern (xeric) hillslopes. Soil samples were obtained from depths of 0-5 and 5-10 cm and physio-chemo-biological properties were assessed in the laboratory. The overall soil quality - as calculated by two soil quality indices (SQIs), including the generalized SQI (SQIgen) and the minimum dataset SQI (SQIMDS) - was significantly (P < 0.0001 for both indices) and 13-22% greater in the control areas (0.52 and 0.61, respectively) than that in the afforestation treatments (0.44-0.46 and 0.50-0.51, respectively). These results are generally attributed to the removal of soil's A-horizon during earthworks, and the exposure of the underlying B-horizon. The similar SQI values of both hillslope aspects, as well as of both soil depths, indicate the generally degraded state of the entire region. In conclusion, while contour bench terracing may facilitate the recovery of herbacaeous vegetation to some extent, the effectiveness of this practice for soil restoration is questionable. Overall, insights of this study demonstrate a caveat that converting natural drylands to forestry systems may not yield sufficient ecological benefits, and therefore should be implemented with caution.
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Affiliation(s)
- Ilan Stavi
- Dead Sea and Arava Science Center, Yotvata, 88820, Israel; Ben-Gurion University of the Negev, Eilat Campus, Eilat, 88100, Israel.
| | - Khandakar R Islam
- Soil, Water, and Bioenergy Resources, The Ohio State University South Centers, Piketon, OH, 45661, USA
| | - Mohammad A Rahman
- Soil, Water, and Bioenergy Resources, The Ohio State University South Centers, Piketon, OH, 45661, USA
| | - Yulia Gusarov
- Dead Sea and Arava Science Center, Yotvata, 88820, Israel
| | - Jawad Laham
- Dead Sea and Arava Science Center, Yotvata, 88820, Israel
| | - Orr Comay
- The Entomological Laboratory for Applied Ecology and Hamaarag, The Steinhardt Museum for Natural History, Tel Aviv University, 6997801, Israel
| | - Uri Basson
- GeoSense Ltd., Even-Yehuda, 40500, Israel; Department of Marine Geosciences, School of Marine Science, University of Haifa, Haifa, 3498838, Israel
| | - Chi Xu
- School of Life Sciences, Nanjing University, Nanjing, 210023, China; Breeding Base for State Key Laboratory of Land Degradation and Ecological Restoration in northwestern China, and Key Laboratory of Restoration and Reconstruction of Degraded Ecosystems in northwestern China, of Ministry of Education, Ningxia University, Yinchuan, 750021, China
| | - Zhiwei Xu
- School of Geography and Ocean Science, Nanjing University, Nanjing, 210023, China
| | - Eli Argaman
- Soil Erosion Research Station, Ministry of Agriculture & Rural Development, Bet Dagan, 50250, Israel
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