Ben du Toit

5.1 Introduction

Intensively managed plantations of fast-growing trees, planted on a short rotations at high stand densities, is arguably one of the most productive and energy efficient ways to produce biomass. In this chapter we discuss silvicultural options to establish and manage highly productive bio-energy plantations, based on case studies from short-rotation plantation forests in warm-climate regions. Our focus is on the growing of biomass as a main product. We also explore the energy and green house gas balances from such intensively managed systems.

A topic that has been extensively researched in short-rotation pulpwood plan­tations in tropical and warm-climate countries, is that of intensive management to boost stand productivity (Schonau 1984; Nambiar 2008; Stape et al. 2008, 2010; Gonsalves et al. 2007; Fox et al. 2007b; du Toit et al. 2010). This management style has been dubbed “Intensive, Site-specific Silviculture” in Southern Africa (Schonau 1984; du Toit et al. 2010), and has been responsible for large improvements in productivity. It has also been categorised under the more general field of “Precision Forestry” by some authors because the management philosophy hinges on choosing and implementing a suite of management operations that are specifically suited to the ecological capability of a specific site type, or to alleviate constraints to productivity on a specific site type (Pallett 2005; du Toit et al. 2010). This production system, with some adaptations, is arguably the most suitable starting point to design silvicultural regimes for intensively managed, highly productive biomass plantations. In its current form, it is usually a man-made (afforested) monoculture tree crop managed under a clear felling system. However, it has some important

B. du Toit (H)

Department of Forest and Wood Science, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa e-mail: ben@sun. ac. za

T. Seifert (ed.), Bioenergy from Wood: Sustainable Production in the Tropics, Managing Forest Ecosystems 26, DOI 10.1007/978-94-007-7448-3__5,

© Springer Science+Business Media Dordrecht 2014 differences to conventional agricultural monocultures, namely minimum soil cul­tivation where feasible, relatively low dependence on artificial chemical inputs for sustained productivity, prolonged periods of minimal cultural interventions, a net carbon footprint that is strongly positive, and the incorporation of significant biodiversity/conservation areas for the maintenance of ecosystem services (usually in the form of ecological networks or corridors) within the broader system in the landscape (cf. Chap. 10). In Sects. 5.2, 5.3, 5.4 and 5.5, we will discuss the most important elements of “intensive, site-specific silviculture” from the existing body of knowledge which essentially consist of a number of strategic choices (e. g. choice of genetic material and planting density/rotation length combination) as well as cultural practices (e. g. site preparation, vegetation management and fertilization). We will also focus on the most promising adaptations of conventional systems may be necessary to optimise this kind of silvicultural system for bio-energy plantations.