Spatial pattern of Siberian silkmoth outbreak and taiga mortality

Abstract

The latest catastrophic Siberian silkmoth (Dendrolimus superans sibiricus Tschetw.) outbreak occurred in central Siberia during 1994–1996. The relationship between forest stand mortality from insects and topographic features (azimuth, elevation, slope steepness) was analyzed based on a high-resolution digital elevation model, a pest damage map and Terra/MODIS data. It was found that pest-induced forest mortality patterns depend on topographic features. Before the outbreak the major part of host forest species was found within the elevation zone of 150–500 m. After the outbreak, surviving dark-needle stands were found mainly at elevations higher than 400 m. The greatest damage was observed at elevations between 210 and 320 m, whereas maximum mortality was observed at elevations of about 200 m and minimal mortality at elevations of 300 m. With respect to slope steepness, maximum damage for all categories was observed for slopes of 5–20°. Slightly damaged stands were most common at low slope angle (about 5° or less), whereas the highest proportion of stands with high tree mortality was found on steeper slopes. With respect to azimuth, insect damage is mostly uniform, with a small increase in damage on the south-west-facing slopes. The spatial pattern of the silkmoth outbreak can provide a basis for prioritizing Siberian silkmoth outbreak monitoring.

Keywords:

• 3D analysis
• landscape
• pest outbreaks
• Siberian silkmoth

Acknowledgements

This work funded in part by NASA Earth Science Enterprise and Russian Fund of Fundamental Investigations grant 06-05-64939.