Assessment of insect occurrence in boreal forests based on satellite imagery and field measurements

Abstract

The presence-absence data of twenty-seven forest insect taxa and recorded environmental variation were used to investigate the applicability of modelling insect occurrence based on satellite imagery. The sampling was based on 1800 sample plots (25 m by 25 m) placed along the sides of 30 equilateral triangles (side one km) in a fragmented forest area (approx 100 km2) in Evo, S. Finland. The triangles were overlaid on land use maps interpreted from satellite images and digitized geological maps. Insect occurrence was explained using either environmental variables measured in the field or those interpreted from the land use and geological maps. The fit of logistic regression models varied between species. The occurrence of certain insect species, especially those associated with Scots pine Pinus sylvestris, could be relatively accurately assessed indireclty on the basis of satellite imagery and geological maps. Models based on both remotely sensed and geological data better predicted the distribution of forest insects expected in the case of Xylechinus pilosus, Dryoceotes sp. and Trypodendron lineatum, where the differences were relatively small in favour of the models based on field measurements. -from Authors