Environmental characteristics of primary outbreak foci of the pine-tree lappet Dendrolimus pini (Lepidoptera, Lasiocampidae)

11 S.

e-journal

200211951

Dendrolimus pini is a severe pest of Scots pine forests in many European countries. The area and frequency of its outbreaks in Poland has increased since 1990s. Outbreak probability is predicted to increase in yet non-outbreak parts of Europe due to climate change. Several studies have focused on the effect of meteorological factors favorable for D. pini outbreaks. However, tree stand, soil, site, and topographic characteristics have been rarely considered, particularly at a fine spatial level (subcompartment, which delimits an individual stand). Therefore, our study aimed to determine the characteristics of D. pini primary outbreak foci (POF). Topographic variables were calculated from a digital terrain model. All the other variables originated from forest inventory and are available to foresters at the stand level for daily management. Random Forest (RF) procedure was applied to analyze two data sets: with and without topographic variables. The analysis revealed that the most important variables common for both models were soil type/subtype and diameter-to-age ratio, with poor Albic Podzols (Ochric) and Albic Brunic Arenosols (Protospodic) and low values (0.27–0.38) of diameter-to-age ratio characterizing POF.
Keywords: Insect defoliators; Random Forest model; Scots pine tree growth; Soil and forest site types
Topography; Water shortage