Reconstructing past disturbance dynamics in mountain spruce forests from fosssil insect remains

Nick Bennett Schafstall

Disertační práce

Abstract:

The identification of fossil insects has been part of paleoecological studies since the 1960’s, when it became apparent that insect taxa have kept their ecological preferences for thousands of years. As insects use the strategy of dispersal rather than adaptation to local climate, insect remains can be used in climate reconstructions, archaeological reconstructions and landscape reconstructions. Several groups of insects, such as chironomids, ants, mites and beetles can be used in these studies. Of the terrestrial insect groups, beetles (Coleoptera) are most widely used because of their enormous variety, diversity and range of habitat, appearing in almost every environment. Moreover, beetle exoskeletons are one of the hardiest in the insect world, and many fossil insect assemblages consist primarily of beetle remains. Recently, the use of paleoecology in the reconstruction of natural disturbances has sparked new interest. Under current climate change, natural disturbances such as floods, drought, wildfires, windstorms and insect outbreaks are becoming more frequent, while increasing in magnitude. Paleoecology can contribute to the development of disturbance models which predict future disturbance events, by reconstructing past disturbance events to create a baseline or analogue for these past disturbance events. Currently, several reconstructions of natural disturbances related to fire or windstorms have been published, but no study has focused on reconstructing past bark beetle outbreaks. This thesis aims to demonstrate how the application of subfossil insect remains can aid in the reconstruction of former landscapes and past disturbances in central Europe, in order to better understand environmental change in this region, and to create a historical analogue of changing landscapes to evaluate current and future adaptation to anthropogenic land-use pressures and climate change. Fossil insect remains were isolated from a lake core from Šumava National Park in Czechia and from a peat bog in Tatra National Park in Slovakia. In addition to these two new study sites, a data synthesis was conducted to summarize the fossil sites with bark beetle remains currently known from Europe and North America. Results from these studies from central Europe show that conifer bark beetle remains from this region are abundant, when compared to the existing records from Europe and North America (Article I & II). The fossil beetle records produced during this PhD work provide a substantial addition to the knowledge of bark beetle remains recorded from fossil sites in central Europe. The high-resolution beetle record from Diera Hollow forest hollow (Article I) contributes to the reconstruction of the changing mountain landscape through time, affected by natural and anthropogenic 5 disturbances. Changes in beetle diversity could potentially be used to direct restoration and conservation practices in this region. A peak in conifer bark beetle remains from the beetle assemblages of Diera Hollow (Article III) could be correlated to the recent bark beetle outbreak in the region. These results allow for further interpretation of the presence of conifer bark beetle remains in sediment records. Trichoptera larvae remains from Prašilské Lake (Article IV), used to reconstruct long-term environmental conditions around the lake, show that acidic conditions of this alpine lake were not only prevailing in recent decades but are a natural feature of this glacial lake. Despite the challenges of this PhD project, due to limited local knowledge on Quaternary entomology and limited knowledge on the ecology and distribution of several montane insect species, the results of this study are encouraging further research and an expansion of the field in this region. The articles in this thesis highlight that previous methods, developed to use insect remains in environmental reconstructions, can contribute in several ways to paleoecological research in central Europe.

Keywords

Fossil insects, Disturbances, Central Europe, Norway spruce forest

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 6. 1. 2021

Obhajoba závěrečné práce

• Vedoucí: prof. Ing. Miroslav Svoboda, Ph.D.

Česká zemědělská univerzita v Praze

Fakulta lesnická a dřevařská

Doktorský studijní program / obor:
Forestry Engineering / Forest Biology