Modelling Non-Timber Forest Products for Forest Management Planning in Europe
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Current Forestry Reports (2020) 6:309–322 https://doi.org/10.1007/s40725-020-00130-7 FOREST POLICY, ECONOMICS AND SOCIAL RESEARCH (A TOPPINEN, SECTION EDITOR) Modelling Non-timber Forest Products for Forest Management Planning in Europe Jari Miina1 & Mikko Kurttila1 & Rafael Calama2 & Sergio de-Miguel3,4 & Timo Pukkala5 Accepted: 13 August 2020 / Published online: 9 October 2020 # The Author(s) 2020 Abstract Purpose of Review The increased popularity and commercial use of non-timber forest products (NTFPs) calls for the develop- ment of models for NTFPs to include their predicted yields in forest management planning and to evaluate the potential of multi- functional forest management. This study assesses and discusses the current state of the art and trends in NTFP yield modelling in Europe and the integration of the models in multi-functional forest management planning at different spatial scales. Recent Findings Climate-sensitive empirical yield models already exist not only for a variety of NTFPs that are economically important to forest owners (e.g. cork and pine nuts) but also for wild-gathered berries and mushrooms, the harvesting of which cannot be controlled by the forest landowner in all European countries. Several studies on multi-functional forest management planning consider the economic profitability of the joint production of timber and NTFP. Harvesting NTFPs can create signif- icant additional incomes for forest owners, compared with timber production only. However, maximizing the economic returns from the joint production of timber and NTFPs often calls for changes in forest management practices. Summary Continued efforts in modelling and predicting the yields of NTFPs have enabled forest managers to further expand the analyses of multi-functional forest planning and management in Europe. Climate-sensitive models also allow analyses on the potential effects of climate change on NTFP yields. New models and forest management practices are still needed for tree fruits, birch sap, a wider variety of wild edible mushrooms, specialty mushrooms cultivated on live trees as well as medicinal and edible forest herbs harvested for commercial value in Europe. Keywords Joint production . Multi-functional forest management . Non-wood forest products . Yield models . NTFP . NWFP Introduction NTFPs is increasing in European forestry [1••, 2••]. Timber- oriented forest management is in transition towards sustain- The global demand for non-timber forest products (NTFPs) able joint-production of timber and NTFPs [3••] and mainte- has increased due to the current trends in lifestyle and con- nance of other ecosystem services [4•, 5–7]. Various models sumption. As a consequence, the commercial utilization of for NTFPs have been developed that would enable their This article is part of the Topical Collection on Forest Policy, Economics and Social Research * Jari Miina 1 Natural Resources Institute Finland (Luke), Yliopistokatu 6 B, [email protected] 80100 Joensuu, Finland 2 INIA-CIFOR, Forest Research Centre, Ctra A Coruña km 7.5, Mikko Kurttila 28040 Madrid, Spain [email protected] 3 Department of Crop and Forest Sciences, University of Lleida, Av. Rafael Calama Alcalde Rovira Roure 191, 25198 Lleida, Spain [email protected] 4 Joint Research Unit CTFC, Agrotecnio, Ctra. de St. Llorenç de Sergio de-Miguel Morunys km 2, 25280 Solsona, Spain [email protected]; [email protected] 5 Faculty of Science and Forestry, School of Forest Sciences, Timo Pukkala University of Eastern Finland, P.O. Box 111, [email protected] 80101 Joensuu, Finland 310 Curr Forestry Rep (2020) 6:309–322 inclusion in forest planning calculations. These models facil- (trade-offs) between timber production and NTFPs [11, 12]. itate multi-functional planning where the predicted yields of Full compatibility (lack of trade-off) or incompatibility (tim- NTFPs are considered simultaneously with other forest prod- ber production prevents the production of NTFP or vice versa) ucts and services. Recent studies on yield modelling of NTFPs are rare cases. In most cases, NTFPs compete to some extent document advances to support the joint production of timber with timber production, the optimality of joint production de- and NTFPs. pending on the shape of the trade-off curve between timber There are many different types of NTFPs differing in abun- production and NTFP (Fig. 1). When the trade-off curve is dance, ecology, origin, yield periodicity, harvesting rights, concave, reflecting an increasing rate of transformation, it is frequency and methods, end-use and economic importance. often optimal to produce timber and NTFP in the same forest Further, the degree of domestication varies considerably, from (cases b and c in Fig. 1). A decreasing rate of transformation wild resources opportunistically collected to products actively (convex trade-off curve) results in the production of either enhanced or even cultivated. All these issues bring their chal- timber or NTFP (case D in Fig. 1). It should be noted that lenges to yield modelling and joint management of NTFPs the shapes of the trade-off curves between timber and NTFP and timber [8•]. can be different at the forest and stand levels. This is because, In this review, NTFPs are categorized into four groups as at the forest level, production can be directed towards NTFPs follows [1••]: (i) mushrooms and truffles; (ii) tree-origin to different degrees in different stands, depending on the pro- NTFPs; (iii) understory plants; and (iv) NTFPs of animal or- duction potentials of the stands. As a result, the trade-off igin. NTFPs of tree-origin include exudates (e.g. resin and curves are often more concave in forest level analyses. Full sap), reproductive propagules (e.g. fruits, nuts and seeds) incompatibility at the stand level turns into a negative corre- and vegetative structures (e.g. bark, cork and leaves), among lation and straight trade-off curve at the forest level. In addi- others. The production of these NTFPs is related to several tion, the length of the planning period, i.e. time horizon, also physiological processes of trees, which are complex and partly affects the shape of the curve. unknown, and therefore difficult to model. On the other hand, The objective of this literature review is to describe the the yields of wild understory berries harvested as NTFPs are recent European advances in modelling NTFP yields and more related to growing conditions within the stand, not di- how the developed models have been applied in forest man- rectly to individual trees. Edible mushrooms of economic in- agement planning at various geographical scales. The second terest are mostly mycorrhizal fungi, whose fruit body forma- objective is to discuss the relationships between various tion depends on both the physiology of trees and microclimat- NTFPs and timber production. Also, the potential for devel- ic conditions controlled by trees. oping new multiple-use forest management practices is Animal-based NTFPs are important products in many discussed. European countries [1••]. Animal products derived from, for example, game and bees include meat, horns, bones, pelts, glands, feathers, wild honey and beeswax. In addition, various Materials and Methods silvopastoral systems may provide beef, milk and many other products [9]. Some NTFPs are derived from game animals We focused our assessment of recent advances in NTFP that are hunted or trapped as a form of recreation or as a means modelling and the integration of the models in forest manage- of species population control. In this review, game-related ment planning based on peer-reviewed research papers pub- NTFPs were deliberately excluded as describing game- lished in English from 2010 to 2019. The cut-off date for the related NTFPs in detail would require a separate review paper. review was at the end of January 2020. NTFP models pub- Depending on the planning objective and NTFP in ques- lished before 2010 have been reviewed by Calama et al. [8•]. tion, the joint production of timber and NTFP can be studied at The literature searches were carried out using the Web of different spatial scales: tree, stand, forest holding or region. Science (WoS) database with the following pre-determined For example, the yield of pine resin (Pinus pinaster), pine nuts keywords: non-timber OR non-wood forest product AND (Pinus pinea) and birch sap (Betula spp.) could be predicted model OR yield OR forest management. Some additional by tree-level models, but the profitability of their production and more targeted searches were undertaken using terms more needs to be analysed at a broader level, e.g. stand and land- directly related to specific NTFPs such as acorn, cork, berry, scape. While stand density influences NTFP yields of individ- fruit, honey, leaves, mushroom, nut, resin, sap and truffle, in ual trees [10], and a target density can be identified to maxi- combination with the previously listed keywords. Search mize tree-level production, a different density may be optimal names of the most relevant European NTFPs were identified for stand-level production, which at the end is the objective of by using existing literature [1••, 2••] and our knowledge. All the management. the materials found in the literature search were first checked Analyses on sustainable multi-functional forest manage- for relevance for the review, and if judged relevant enough, ment may reveal both compatibilities (synergies) and conflicts they were selected for further analyses. Besides the literature Curr Forestry Rep (2020) 6:309–322 311 Fig. 1 Different types of a b relationships between forest Full compatibility Competition and positive correlation products ranging from full No trade-off Trade-off at near-maximal level compatibility (a) to different E.g. timber and bark from felled trees Increasing rate of transformation degrees of competition (b, c, d). E.g. Boletus edulis and spruce timber Joint production is the only possibility in case a, probably optimal in cases b and c,and unlikely optimal in case d.