Population dynamics of Ips typographus in the Bohemian Forest (Czech Republic): Validation of the phenology model PHENIPS and impacts of climate change

Abstract

Phenology models play an important role in insect ecology and pest management. For bark beetle species prone to frequent outbreaks, they help predict swarming periods, discern sister generations hard to recognize in the field yet indispensable in studies of bark beetle population dynamics, predict the extent to which the generations entering diapause develop, as well as help address the omnipresent issue of impacts of climate change. As a prerequisite to developing a simulation model of landscape-level forest disturbances in the Bohemian Forest, including those due to Ips typographus, we validate the phenology model PHENIPS, published in the literature and simulating seasonal development of this species, by data coming from this region. We find a reasonable agreement between the modeled and actually observed bark beetle dynamics, thus strengthening the potential role of PHENIPS in any future attempt to model dynamics of Central European populations of I. typographus. In addition, we use PHENIPS to assess impacts of climate change on temperature-regulated phenology of I. typographus. In contrast to previous studies which used regional climate models to predict future temperature development, we independently account for changes in the mean air temperature and in the frequency of extreme weather events – for the latter, we assume that the inter-annual air temperature variance will also increase. Since bark beetle development is driven by bark temperatures and both low and high bark temperatures inhibit the development, we find that the effects of increases in the air temperature mean and variance are compensatory. Hence, if climate is to change so that both these characteristics grow, we expect only a relatively minor change in generation development time. Moreover, initiation of the third filial generation of I. typographus in the Bohemian Forest is predicted to occur only for relatively large shifts in the mean air temperature.