ecological engineering 32 ( 2 0 0 8 ) 215–221 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/ecoleng Engineering properties of Leucaena leucocephala for prevention of slope failure O. Normaniza ∗ , H.A. Faisal, S.S. Barakbah Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia article info Article history: Received 4 June 2007 Received in revised form 30 October 2007 Accepted 5 November 2007 Keywords: Soil erosion Leucaena leucocephala Root length density Soil–root matrix Root reinforcement abstract The potential of Leucaena leucocephala as an erosion control plant was investigated in terms of its capacity of root reinforcement, root profile and root shear strength. The species stud- ied exhibited extensive, dense rooting and depth of penetration. These aspects, to some extent, could provide surficial as well as deep-seated erosion control. A high water absorp- tion capacity would increase suction, thus potentially extracting water at the greater depth. The soil–root matrix significantly affects cohesion factor but not the angle of friction. The effect varies with increasing depth and age of plant depending on the root length density. After 6 months of growth, the cohesion factor had tremendously increased by two- to five- fold (0.1–0.5 m soil depth). This range almost reached the values of those in the 12-month treatment, indicating a high contribution of the root system to soil–root reinforcement. © 2007 Elsevier B.V. All rights reserved. 1. Introduction In the past few decades, topics on ecological restoration have been much discussed due to the increase in awareness of environmental conservation issues. Various terminologies and techniques have been established, integrated and imple- mented in order to obtain a structurally sound, ecologically sustainable and socio-economic method for restoring the ecosystem. One of the techniques of interest is slope bioengi- neering, the use of living plant materials to perform some engineering and ecological functions for slope stabilization and site restoration of riverbanks, which is widely investi- gated and discussed (e.g. Haigh and Gentcheva-Kostadinova, 2002; Li and Eddleman, 2002; Li et al., 2006). The mecha- nism used includes the enhancement of soil shear strength using vegetation–soil systems and limiting soil particle move- ∗ Corresponding author. Tel.: +60 3 79674185; fax: +60 3 79674178. E-mail address: normaniza@um.edu.my (O. Normaniza). Abbreviations: RLD, root length density; WAC, water absorption capacity. ments on slope via utilizing the effects of root systems on soil structure. It is hence of great interest to explore further the influence of the engineering properties of the root system on slope stability and shallow landsliding. Much has been investigated and written about root growth, phenology and function but very little attention has been given to aspects of roots concerning stabilization of slopes. This is mainly due to destructive harvesting and the diffi- culties in collecting representative samples and separating the roots from soil in the field or on the slope. However, the progress made in the past few years on the contribution of the root system in reinforcing mass-stability of the slopes is an eye-opener. Various studies have documented the impor- tant effects of root density in preventing landslides (Gray, 1995; Abe, 1997). The mechanical or reinforcing effect of plant roots on the stability of slopes is mainly attributed to, inter alia, the 0925-8574/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.ecoleng.2007.11.004