Landscape-scale Ips typographus attack dynamics: from monitoring plots to GIS-based disturbance models

Abstract

In natural spruce stands, a change of generation is usually initiated by wind or bark beetle disturbances. We combined semi-temporary monitoring plots, remote sensing, and GIS in order to understand and model these processes. Sub plots, called “active”, were located in areas with a high probability of bark beetle or wind disturbances. The optimal location of these plots is usually at an active forest edge, i.e., the zone of maximal change in bark beetle abundance over time, corresponding to the border between wind-damaged or bark beetle-attacked parts and undisturbed parts of a forest stand. The key variable investigated was tree mortality caused by bark beetles. Other variables were similar to those recorded in traditional forest monitoring. Tree defense indicators (resin flow, phenolic compounds) and reaction of a tree to bark beetle inoculation were measured. Terrestrial data were then combined with remote sensing data. Time series of satellite images were analyzed in order to define the pattern of wind and bark beetle damages. Weather monitoring data were used for predicting bark beetle and water stress development. All of the information was integrated in a GIS-based system and future bark beetle infestations were predicted. In this paper, we review previous studies and conclude that: (1) the hypotheses of habitat selection (non-host volatiles and semiochemical diversity) and location of moderately-stressed host trees are confirmed, although further work about olfactory orientation and host resistance is needed;(2) reactions of trees to bark beetle attack can be predicted by monitoring several parameters, e.g., air temperature and tree physiology; (3) data from ground monitoring can be integrated with GIS and remote sensing systems for bark beetle prognosis and management at the habitat and landscape levels.