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Spatial mapping of tree species site suitability for the Hawke’s Bay region

Authors: David Palmer, Andrew Clarke, Kit Richards, James Powrie, Les Dowling, Tim Payn
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 2020, Issue N.Z.J.For. 65(1) 2020, pp 30-35, May 2020

Abstract: Planting the right tree in the right place and for the right purpose is an adage commonly used in the discussion of where to establish new plantations. In reality, information to support landowner decisions around the establishment of new forests is not in a readily available or in an intuitive format. The mapping of Tree Species Site Suitability Indices for Hawke’s Bay was developed to provide landowners with easy-tounderstand maps to support decision-making and to complement field investigations. Specifically, tree species site suitability methodology was developed to match the species Pinus radiata (radiata pine), Sequoia sempervirens (coast redwood), Cupressus lusitanica, Eucalyptus (generic scenario), Leptospermum scoparium (manuka) and Podocarpus totara (totara) to their preferred growing environments across the Hawke’s Bay region. National tree species site suitability characteristics include ranges of average annual temperatures, total rainfall, elevations above sea level, site fertility including soil water availability, rooting depth, and soil fertility and tolerance to both wind exposure damage and salt water spray. This information was compiled from existing permanent sample plot (PSP) location data, published information and expert knowledge for each of the species, to help inform us of the preferred environmental conditions for each species. Tree species growing conditions were mapped using response curves and to assign fuzzy logic (membership) values between zero and one, with one being an optimal degree of membership (DOM), and zero being no DOM. For example, is the establishment location for a tree too hot, too cold, too wet or too dry and so forth. The outcome of this project provides the regional council and landowners with maps by which to assess and compare potential tree species suitable for their local site conditions - Tree Species Site Suitability Indices - and as a basis for more detailed assessment and planning.