Effects of Land Use Change on Soil Quality Indicators in Forest Landscapes of the Western Amazon Santiago Bonilla-Bedoya, 1,2 Magdalena López-Ulloa, 3 Tom Vanwalleghem, 4 and Miguel Ángel Herrera-Machuca 2 ABSTRACT: Western Amazon has the highest forest biodiversity in the world; however, farming, pasture, or subsistence farming has cleared extensive forest areas, impacting soil quality. This study evaluates the variations in soil quality indicators such as organic carbon (OC), NH 4 + , available P, soil texture, and pH, taking into account changes of land use from forest to disturbed areas in four different landscape positions: plains, peneplains, piedmont, and periandes piedmont. We used three vegetation cover maps of 1990-2000-2008 and 1,820 soil samples in an estimated area of 40,000 km 2 . Cokriging and regression kriging of each edaphic attribute and maps of land use were crossed. Analysis of variance for each landscape position was applied in order to identify significant differences in soil quality indicators between different land use categories (forest and disturbed areas). Re- sults suggest changes in biogeochemical soil dynamics. We reported statistically significant reduction in the percentage of OC for disturbed areas and an increase in available P, which is remarkable. NH 4+ stocks were lower for disturbed areas; however. In piedmont and periandes piedmont land- scapes, forests presented the highest concentrations of OC (3.99 ± 1.1 and 5.06 ± 1.41, respectively) in comparison to disturbed areas (3.56 ± 0.87 and 3.98 ± 1.41, respectively). Changes in soil quality main indicators suggest a potential drop in ecosystem services production for the western Am- azon of Ecuador. Management decisions should consider sustainable land use strategies oriented to maintain the resilience of soil quality indicators. Key Words: Equatorial Andean Amazon, forest landscape, land use change, soil quality (Soil Sci 2017;182: 00–00) L and use changes are mainly driven by socioecological system dynamics (Braimoh and Osaki, 2010; Turner, 2010). Land use practices vary across the world, and their fundamental purposes are the identification and use of ecosystem services and benefits to meet human needs (Foley, 2005). Over the last 25 years, 24% of the global land area has suffered a dramatic decline in quality and productivity as a result of unsustainable land use management (Bai et al., 2008; Bringezu et al., 2014). Soil is the primary resource for land use (Hillel, 1992; Braimoh and Osaki, 2010) and contributes to five principal functions within a landscape: nutrient cycling; water-holding capacity; habitats and biodiversity; storing, filtering, buffering, and transforming com- pounds; and provision of physical stability and support (Blum, 1993; Young and Crawford, 2004; Koch et al., 2013). Maintaining soil quality is a key determinant for ecosystem services and benefits management and climate change mitigation (Lal, 1997; Foley, 2005; Lal, 2010; Bringezu et al., 2014). In the tropics, the transition that occurs between the degradation of forests and soils is mainly due to the agricultural frontier (ITTO, 2002). Both soil and forest degradations reduce its capacities to pro- duce and provide ecosystem services and benefits. The causes of soil degradation include some combination of water erosion, wind ero- sion, soil fertility decline due to nutrient mining, waterlogging, sali- nization, lowering of water table, and overuse of chemical inputs causing soil pollution (Scherr, 1999; Bringezu et al., 2014). A de- graded forest has lost the structure, function, composition, and/or the productivity of species associated with these ecosystems. Between 1980 and 2015, humid tropical forest landscapes showed the largest segment of global net forest loss (Lindquist et al., 2012; Food and Agriculture Organization of the United Nations, 2015); almost 100 million hectares were the net total increase in ag- ricultural land in the tropics; more than 55% of new agricultural land came at the expense of intact forests, and another 28% came from disturbed forests (Gibbs et al., 2010). This trend could continue con- sidering that tropical countries represent a potential reserve for agri- cultural expansion (Lambin and Meyfroidt, 2011). Amazon forest is one of the most biologically diverse ecosys- tems in the world (Baker et al., 2014). Western Amazon (WA) or Andes Amazon is recognized as one of the most biodiverse regions within the overall Amazon basin. The region maintains large tracts of intact tropical humid forests and is critical in maintaining stable climate conditions within the current scenario of global warming (Finer et al., 2009; Finer et al., 2010; Finer et al., 2015; Killeen et al., 2007). Geological and phylogenetic evidence shows how the Andean uplift was crucial for Amazonian landscapes and ecosystems evo- lution and its biodiversity patrons (Hoorn et al., 2010). The Ama- zonia is heterogeneous regarding parent material, geographic accidents, and geomorphology history (Irion, 1978; Quesada et al., 2011). It also has important soil diversity that includes different pedogenetic levels and taxa (Richter and Babbar, 1991; Quesada et al., 2011). A gradient from West to East for chemical properties of soils is reported for the Amazon Basin (Fittakau, 1972; Quesada et al., 2011; Quesada et al., 2012). Pedogenesis of the West Amazon is based on the Quaternary Miocene (Hoorn et al., 2010); therefore, there is a relative increase on soil fertility in areas with significant in- fluence of the Andes Mountains, whereas for central Amazonia, lim- itations in fertility due to greater stability in regional landscapes have been reported (Silver et al., 2000). Despite this difference, regional soils present chemical limita- tions expressed by high concentration of Al 3+ due to low pH, low Guest Editor: Emmanouil Varouchakis. 1 Centro de Investigación para el Territorio y el Hábitat Sostenible. Universidad Tecnológica Indoamérica, Machala y Sabanilla, Quito, Ecuador. 2 Department of Forest Engineering, E.T.S.I.A.M., Campus de Excelencia Internacional Agroalimentario (ceiA3), Universidad de Córdoba, Cordoba, Spain. 3 Department of Environmental Engineering, Universidad de Las Américas, Quito, Ecuador. 4 Department of Agronomy, E.T.S.I.A.M., Campus de Excelencia Internacional Agroalimentario (ceiA3), Universidad de Córdoba, Cordoba, Spain. Address for correspondence: Dr. Santiago Bonilla-Bedoya, Centro de Investigación para el Territorio y el Hábitat Sostenible. Universidad Tecnológica Indoamérica, Machala y Sabanilla, 170301, Quito, Ecuador. E-mail: santiagobonillab@hotmail.es Financial Disclosures/Conflicts of Interest: None reported. Received November 15, 2016. Accepted for publication May 5, 2017. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0038-075X DOI: 10.1097/SS.0000000000000203 TECHNICAL ARTICLE Soil Science • April 2017 • Volume 182 • Number 4 www.soilsci.com 1 Copyright © 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.