Monitoring and Prediction of Siberian Silk Moth IDendrolimus sibiricus/I Tschetv. Outbreaks Using Remote Sensing Techniques

Insects are a significant cause of harm and mortality to forest areas. In particular, the forests of Siberia, covering over 2.4 million square kilometers with a low or non-existent pest insect population, are at high risk. Under such conditions, observing insects from the ground is nearly impossible. Consequently, remote sensing techniques are the sole feasible option. However, many remote indicators only change after significant damage occurs to the stands of trees, making it too late to implement protective measures. The objective of this study was to construct distance indicators that could identify areas where forest stands have lost resistance to attacks by such a dangerous pest of Siberian forests as the Siberian silk moth Dendrolimus sibiricus Tschetv. To create indicators, it has been suggested that estimations rely on the reaction of stands to weather conditions during the season, instead of absolute values. Such remote indicators were constructible, and these indicators in the areas of future outbreaks had changed already two or three years before the outbreak. Remote sensing data allow the development of complex indicators of forest stands’ insect resistance anywhere in the world, thus making it possible to monitor large areas to identify risk of pest outbreaks. The feasibility of risk assessment of a Siberian silk moth (Dendrolimus sibiricus Tschetv.) outbreak was analyzed by means of landscape and weather characteristics and tree condition parameters. Difficulties in detecting forest pest outbreaks (especially in Siberian conditions) are associated with the inability to conduct regular ground surveillance in taiga territories, which generally occupy more than 2 million km[sup.2] . Our analysis of characteristics of Siberian silk moth outbreak zones under mountainous taiga conditions showed that it is possible to distinguish an altitudinal belt between 400 and 800 m above sea level where an outbreak develops and trees are damaged. It was found that to assess the resistance of forest stands to pest attacks, researchers can employ new parameters: namely, characteristics of a response of remote sensing variables to changes in land surface temperature. Using these parameters, it is possible to identify in advance (2–3 years before an outbreak) forest stands that are not resistant to the pest. Thus, field studies in difficult-to-access taiga forests are not needed to determine these parameters, and hence the task of monitoring outbreaks of forest in