Rehabilitating degraded forest land in central Vietnam with mixed native species plantings Sean McNamara a, * , Duong Viet Tinh b , Peter D. Erskine a , David Lamb a , David Yates a , Sharon Brown a a School of Integrative Biology, The University of Queensland, Brisbane, Qld 4072 Australia b Hue University of Agriculture and Forestry, Hue, Thua Thien Hue Province, Vietnam Abstract This paper examines the use of Acacia as a nurse crop to overcome some of the ecological and economic impediments to reforestation of degraded areas dominated by grasses including Imperata cylindrica. The study site at Hai Van Pass in central Vietnam was initially reforested using Acacia auriculiformis. After 8 years these stands were thinned and under-planted with Hopea odorata, Dipterocarpus alatus, Parashorea chinensis, Tarrietia javanica, Parashorea stellata, Scaphium lychnophorum, Peltophorum dasyrhachis var. tonkinensis and other high-value native species. At the time of field assessment (early 2004), the Acacia trees were aged between 16 and 18 years and basal area ranged from 9 to 13 m 2 ha À1 after several thinnings. Acacias facilitated the establishment of native species, but after 6–7 years of growth, further thinning is needed to maintain growth rates. In addition to assisting the establishment of native species, the Acacia nurse crop should provide a revenue stream (NPV about US$ 180, or IRR 19%) sufficient to cover the establishment costs of the underplanted native species (about US$ 100). # 2006 Published by Elsevier B.V. Keywords: Acacia; Fire; Under-planting; Shade requirements; Reforestation; Hopea odorata; Imperata cylindrical; Nurse crop 1. Introduction Forest cover in Vietnam diminished rapidly for most of the latter half of the last century declining from around 43% in the 1940s to 17% by the late 1970s (De Koninck, 1999). By 1995 the total area of land with grass or shrub cover was estimated to cover 9.7 million ha (Gilmour et al., 2000). Between 1976 and 1990, it is estimated that 185 000 ha of forest cover was being lost annually (Barney, 2005). There are a number of reasons for these losses including logging and over harvesting of forest products, slash and burn agriculture and by encroachment into forest lands by industrial agricultural (Nguyen and Gilmour, 2000; Lamb and Gilmour, 2003; Morris et al., 2004). Many forest areas in Thua Thien Hue province were also affected by the use of chemical defoliants and intensive bombing during years of war. Application of chemical defoliants was often followed by napalm bombing to ensure vegetation clearance (Filipchuk, 1990). As a result of this many previously forested areas of Vietnam were converted to fire-prone grasslands and are unlikely to recover in the short term without specific interventions. Forest policy in Vietnam has undergone several significant changes over the last decades in an attempt to overcome these losses, beginning with the National Forestry Action Plan developed in the early 1990s (Nguyen and Gilmour, 2000; Morris et al., 2004; Ohlsson et al., 2005). A recent development has been the introduction of the ‘‘Five Million Hectares Rehabilitation Program (5MHRP)’’, the target of which is to increase forest cover to 43% (MARD, 2001; Phan, 2004; Morris et al., 2004; Ohlsson et al., 2005). If successful this will return forest cover in Vietnam to the levels present in the 1940s. Reforestation of many of these degraded areas is difficult. Not only is it difficult to establish trees in fire-prone grasslands (e.g. Turvey, 1994) but many of the soils are also very infertile and very few native species are able to tolerate such sites. The seedlings of some tropical tree species also appear to require some degree of initial shading to become established (Aide et al., 1995; Parrotta et al., 1997). Because of this much early plantation development in Vietnam has focussed on mono- cultures of fast-growing exotic species of Eucalyptus, Acacia and Pinus (Nghia and Kha, 1998; Turnbull et al., 1998; Kha et al., 2003). The advantages of such species have been reviewed by Boland and Turnbull (1981). Most of these species www.elsevier.com/locate/foreco Forest Ecology and Management 233 (2006) 358–365 * Corresponding author. E-mail address: sean.mcnamara@uq.edu.au (S. McNamara). 0378-1127/$ – see front matter # 2006 Published by Elsevier B.V. doi:10.1016/j.foreco.2006.05.033