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Proceedings of the Symposium on Global and Environmental Monitoring

which error reduction and more localized estimates are desired through this
approach include the following:
(1) forest area clear-felled annually;
(2) forest area thinned on an annual basis and to what degree thinned;
(3) area by forest type (for the NFI, these types are defined in terms of
dominant tree species, relative stocking density, and tree size);
(4) change or exchange of forest area, on an annual basis, in or with other
than traditional forest land classes, including agricultural land, wetlands,
mountains, and national park land;
(5) forest area, on an annual basis, associated with given degrees of
regeneration success; and
(6) forest area damaged annually by diseases and pests.
The Department of Forest Survey has grouped the six estimation areas listed
above into two categories: (1) remote sensing-aided estimation for
environmental monitoring (which includes the sixth estimation objective),
and (2) remote sensing for cover type area and cover type area change
(which includes the first Five estimation objectives). Environmental
monitoring, while a technically more difficult problem from the remote
sensing standpoint, has recently been given a slightly higher priority by
the Department.
Another important objective of introducing remote sensing in the Swedish
NFI is to provide a data type that can enable the effective use of forest
industry sample plot data with NFI plot data. This will enable further error
reduction, particularly at the local level, and perhaps expand the kinds of
estimates available. The use of satellite-acquired digital data will also result
in the availability of data files containing spatial information. These files
can consist of category maps, aggregatablc into different class structures
according to NFI or other user needs.
Focus on environmental monitoring in this review has been directed to the
problem of forest tree disease and pest detection and identification. With
respect to this problem, some specific applications of aerial photography for
mapping or counting affected trees for a few types of damage could be
adapted for use in the NFI in the near future. These include the present
operational use in Sweden of large (approximately 1:2000) scale color
infrared photography for Norway spruce (Picea abies) and Scotch pine
(Pinus Sylvestris) needle loss surveys (e.g., Hedlund and Jacobson, 1988,
Sylvander 1987). Abnormal needle loss is thought to be related to acid rain
damage in many cases. Based on a study reported by Sylvander (1989), use
could be made of the same type of photography for inventorying, on a
sample basis, Gremmeniella abietina fungi damages. Color aerial
photography of somewhat smaller scale is now being used by private
companies in Sweden to locate and assess blow-down damage.
Satellite applications, with the following exception, arc not expected to be
reliable for application in the near future in the Swedish forest context. The
exception is the possible use of Landsat TM and SPOT data to enable