Provisioning of nonwood forest products in diverse plantations

In addition to the production of wood, the production function of plantations also extends to other plant products and animals that may be harvested for human consumption. Forest products that are not related to timber have been important to human beings since the hunting and gathering age. The importance of non-wood forest products (NWFPs) for the livelihood systems of people all over the world, in developing as well as industrialized countries, has been clearly pointed out in the literature (Wickens, 1991; SCBD, 2001; Chamberlain et al, 2002; Ticktin, 2004; Kaushal and Melkani, 2005; Emery et al, 2006). Here, the term non-wood forest products (NWFPs) will be used for all the biological material (other than wood products) that can be utilized within the household, be marketed or have social, cultural or religious significance (Wickens, 1994). Typically this includes nuts, fruits, berries, mushrooms, herbs, bark, resin, rubber, etc. This definition does not include forage, which sustains livestock or game animals (Wickens, 1994). However, in the livelihood systems of many people, forage from forested land plays an important role.

With a shrinking area of natural forests, the supply of NWFPs is shrinking accordingly. For example, it has been estimated that the demand for these products outstrips the sustainable yield from Indian forests (Appasamy, 1993), and in countries such as Nepal, some non-timber forest product species are threatened by extinction from overexploitation (Maraseni, 2008). Not surprisingly, NWFPs are cultivated at an industrial scale in plantations, for example for rubber, palm oil, nuts, etc. (Last, 2001). In addition, the active management of forests for provision of NWFPs has commenced in some areas, partly to reduce the pressure on native forest (e.g. Maraseni, 2008; Trauernicht and Ticktin, 2005). This objective, which is similar to that for the establishment of tree plantations in some regions, suggests that there may be some synergies. However, the active cultivation of NWFPs is certainly more in the domain of agroforestry, in particular in home gardens, which provide a rich variety of these products and function as harbours of biodiversity (Kumar and Nair, 2006). The relationship between biodiversity and NWFPs in these systems warrants a separate discussion, which is beyond the scope of this chapter and this book. Here, we ask, whether management for diversity in 'conventional' tree plantations might accommodate the provisioning of NWFPs. However, studies that deal specifically with silvicultural approaches to maintaining or enhancing the provision of NWFPs are extremely rare. This lack of knowledge has been identified by different authors in different regions. Neumann and Hirsch (2000) reviewed the literature about the policies and practices regarding the management of NWFPs and found, that 'there are promising speculations about integrating timber and NWFP management, but few studies that experimentally test the possibilities of different management techniques and silvicultural treatments, and there is even less information specific to plantations. Chamberlain et al (2002) analysed the management plans of 32 eastern national forests of the US concerning the space given for the description and management of NWFPs. Despite an increasing importance of various NWFPs in the studied states, NWFPs were mentioned in only seven plans and no plan devoted more than 1 per cent of its text to them. The lack of explicit concern for NWFPs in management plans, inventory, policy and legislation is echoed by others (Lynch and McLain, 2004; Emery et al, 2006). The lack of such information is particularly obvious for tropical countries, where NWFPs play a more important role for local livelihoods (Panayotou and Ashton, 1992; Mahapatra and Mitchell, 1997; Gautam, 2001; Ticktin et al, 2002; Ticktin, 2004).

One of the speculations about silvicultural treatments and NWFPs mentioned by Neumann and Hirsch (2000) is that product yield in forests or plantations may be increased through the enhancement of biodiversity and the creation of structural diversity (Gautam, 2001; Ticktin, 2004; Gautam and Devoe, 2006). However, this often seems to be largely related to the interactions between canopy light regime and understorey development. For example, Gautam (2001) found that lopping and litter removal in sal (Shorea robusta) forests in Nepal increased understorey light conditions and thus enhanced the supply of NWFPs such as herbs, lianas and grasses, whereas useful shrubs declined. Floristic diversity in plantations, which is probably related to the diversity of NWFPs, is often inversely related to canopy cover (e.g. Bone et al, 1997; and discussion below). However, based on existing studies, the effects of tree species diversity on understorey diversity can usually not be disentangled from the effects of succession and plantation age (see Box 5.2). For example, monoculture plantations have been proven to be a probate system for the successful re-establishing or restoration of diverse native vegetation (Lugo, 1997; Parrotta et al, 1997). Here, functional traits such as shade-tolerance, litter decomposability or the allelopathic effects of the tree species are more important than questions of tree species richness or origin, native vs. exotic.

Most studies in the literature are concerned with the management of selected non-timber products. The question that is important for this review, namely to what extent production of NWFPs can be accommodated in plantations grown for other purposes without affecting the main production goals or what the trade-offs may be between the provision of NWFPs and wood production, is not dealt with. Despite the lack of information, however, some general statements can be made. The provision of mushrooms would be highly compatible with plantation management, particularly when these are the fruiting bodies of mycorrhizal fungi, which are fed by the tree crop. However, these may not necessarily be native mushrooms, since for some exotic species the mycorrhizae were imported as well (Brundrett et al, 1995). For the provision of NWFPs that stem from understory vegetation (fruits, berries, medicinal plants, roots and tubers) the same considerations apply, discussed further below in relation to the richness and diversity of understorey vegetation in plantations. The provision of these plant products may depend on the functional traits of tree species, their canopy light transmission, competition for soil resources, litterfall, initial site preparation, etc. Thus provision NWFPs may be influenced by spacing, thinning and the initial establishment techniques.

Information about the role of plantations in the provisioning of huntable animals is even scarcer, although large-bodied mammals and birds are a major source of dietary protein, in particular in many parts of the tropics (Robinson and Bennett, 2004). This lack of information is probably related to the scale of investigation, since the home range of many of these animals is defined by landscapes comprising a variety of land use and forest types, and where it is difficult to relate hunting and habitat preferences to particular landscape units such as plantations. The habitat quality for huntable animals is likely to depend on the structural diversity of plantation forests as well as the diversity of the landscape and the proportion of native ecosystems in the landscape (e.g. Nasi et al, 2008). One study, which investigated subsistence hunting patterns in a landscape with different land-use types in tropical Brazil, showed that most of the kills were sourced from primary forest (Parry et al, 2009). In contrast, hunting pressure in plantations was low, despite a high catch-per-unit-effort. The authors assume that plantations were less attractive to hunters because there were limited additional benefits from visiting these habitats. Because large-scale tree plantations fail to attract hunters away from primary forests and support few forest specialist animals, they were viewed to have limited conservation potential for large vertebrates.

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