Remote sensing aided monitoring of non-timber forest resources
Löfstrand, Ronny; Olsson, Håkan; Reese, Heather
Forests have traditionally been multiple use areas. However, during the last century the scientific literature on forests has been dominated by timber related issues. The non-wood forest-based resources such as recreation, biodiversity, water, wildlife habitat, range and fisheries did not gain recognition until multiple-use of forests became a renewed concept (Hytonen et al. 1995). That recognition came when the Multiple Use Sustained Yield Act (USA) was passed in 1960 which promoted sustained management of all renewable forest resources, including the non-wood ones. Another catalyst for interest in forests as non-wood resources was the 1992 Convention on Biological Diversity. These non-wood resources have been treated under different names e.g. non-wood goods and services (NWGS), non-wood benefits (Wibe 1994) that can all be regarded synonymous to non-timber forest resources (NTFR) which is the term used in the present project. The landscape can be thought of as a hierarchically organised system (Forman and Godron 1986). In order to understand the landscape, and to be able to predict changes using this, three linkages must be known. Each landscape element is linked to the: 1) encompassing element at the next higher level; 2) nearby elements at the same scale; and 3) component elements at the next lower level. Each level in the hierarchy represents a single scale, from fine grained to coarse grained (Forman 1995). The occurrence of resources and their distributional pattern in the landscape are to a large extent scale-dependent (Turner 1989). The same can be said about processes, although processes are usually aspects of biodiversity that are less easy to observe. With processes, the time dimension should also be included since many processes occur very slowly. In order to determine the existence of processes or NTFRs, indicators are sometimes used. Indicators work as observable substitutes for the object or process of interest, the existence for which they provide evidence. Due to the described hierarchical nature of the landscape, the scale-dependency of monitoring and mapping resources, and the necessity to use indicators, there is a need to combine different data sources, i.e. field data, mapped information and when feasible remote sensing data. Usually when remote sensing data is used, it must be combined with a field sample with known geographical position. The objective of the present literature review is to provide an overview of remote sensing related methods for monitoring NTFR. Our aim is not to produce a complete review of the topic, but rather to present a sample of studies that can be regarded as good representatives of what has been achieved and reported in the scientific literature. The focus is on published studies, research and operational monitoring where remote sensing has been used for monitoring of non-timber forest resources. The whole NTFR concept is considered, in the event that we find meaningful studies, but the focus falls primarily on biodiversity monitoring. The scales used in most studies are from stand (1 ha) up to landscape (100 km by 100 km) level, and using remote sensing data sources with image elements ranging from 1 to 200m.
forest land; remote sensing; mulitiple use; landscape; ecology; biodiversity
Arbetsrapport / Sveriges lantbruksuniversitet, Institutionen för skoglig resurshushållning
Publisher: Institutionen för skoglig resurshushållning, Sveriges lantbruksuniversitet
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