Czech University of Life Sciences in Prague Department of Forestry and Wood Sciences Reconstructing past disturbance dynamics in mountain spruce forests from fossil insect remains Author: Nick B. Schafstall, MSc Supervisor: Prof. Ing. Miroslav Svoboda, PhD Co-supervisors: Dr. Jennifer L. Clear, PhD and Dr. Niina Kuosmanen, PhD 2020 1 With this text, I confirm that this PhD thesis “Reconstructing past disturbance dynamics in mountain spruce forests from fossil insect remains” was elaborated independently with the use of quoted literature and consultations with my supervisor and other advisors. I agree with publishing this Ph.D. thesis according to Czech law n. 111/1998 Sb. about the universities in its current valid wording. This agreement is independent from the result of the official defense of this thesis. Prague, 10-12-2020 2 Acknowledgements Miroslav Svoboda has acted as my supervisor during my PhD and I want to thank him for all the good advice about working at the Czech University of Life Sciences. All the support from the department secretaries Blanka Ptačková, Marketa Chaloupková, Jana Dolejšová and Lucia Parpelová is very much appreciated and, at times, really lifesaving. Jennifer Clear and Niina Kuosmanen have been acting as my co-supervisors during my PhD. Their advices on everything that crosses one’s path in the academic world- conferences, collaborations, writing, publishing and much more- have made me what I am today in my professional career. I want to thank especially Niina for putting so much of her time and effort in reviewing all of my work. I want to thank Jennifer for hiring me on the PEDECO project, a GAČR project that ran from 2016 until the end of 2018, for her valuable advice on topics for manuscripts and for helping me in finalizing this thesis. The PEDECO project, as well as internal grants from my faculty, provided financial support to attend conferences. Jennifer introduced me to PAGES, a community dedicated to paleo-research. The early-career network of PAGES (PAGES-ECN), and my role in the steering group of this network, has been a great support in developing my soft skills. During my second year I went on a six-months study stay with Nicki Whitehouse at Plymouth University. I want to thank her for becoming my advisor and for teaching me a lot of methodology and theory behind the reconstruction of landscapes based on fossil beetle assemblages. Peter Fleischer Sr. of Tatra National Park has helped the PEDECO project with identifying sites in the Tatra National Park, but the collaboration with him on my articles was of great importance as well. He brought me in contact with other researchers in this region and provided literature about the human history in the Spiš region. Martin Fikáček of Charles University and Jan Ružička of the ČZU Environmental Faculty have helped me in great lengths to get in touch with the coleopterist community in and outside Prague. I consider them my friends. Many thanks to the curators of the different museums who allowed me access to their museum collections of Coleoptera, and to all the experts on beetle families who helped with the identification and ecological interpretation of those identifications, especially Milos Knížek (Scolytinae) and Oldřich Hovorka (Carabidae). Thanks to my colleagues Joey Pettit and Mélanie Saulnier who have helped me to deal with the statistical program R, and thanks to the colleagues from Charles University who were only sideways involved with my studies but provided much support, especially Petr Kuneš, Alice Moravcová, Vachel Carter and Daniel Vondrák. Thanks to my office mates Yumei Jiang and Krešimir Begovič and finally, I would like to thank my friends in Prague and my family in The Netherlands for their support during the last four years. 3 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 4 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. 5 Contents Acknowledgements 3 Abstract 4 List of original publications 8 List of tables and figures 9 1. Introduction 10 1.1 Paleoecology and its applications 10 1.1.1 The practice of paleoecology 10 1.1.2 Quaternary sciences 10 1.1.3 Archaeology 11 1.2 Quaternary entomology 11 1.2.1 The history and applications of Quaternary entomology 11 1.2.2 Temperature reconstructions 12 1.2.2.1 Coleoptera 12 1.2.2.2 Chironomidae 13 1.2.3 Archaeological reconstructions 15 1.2.4 Landscape reconstructions 16 1.3 Reconstructions of past disturbances in Europe 18 1.4 Aims of this thesis 19 2. Methods 20 2.1 Study area and sites 20 2.2 Sediment sampling, geochemistry and chronology 21 2.2.1 Prašilské Lake 21 2.2.2 Diera Hollow 22 2.3 Fossil beetle analysis 24 2.4 Trichoptera larvae analysis 25 2.5 Other proxies 25 2.6 Statistical analysis 26 2.6.1 Shannon’s diversity index 26 2.6.2 Hierarchical cluster analysis 27 2.6.3 Disturbance Frequency Index 27 2.6.4 CharAnalysis 28 2.6.5 Linear regressions 28 2.7 Literature studies 29 6 2.7.1 Data from databases 29 2.7.2 Human occupation data 29 3. Results 30 3.1 Using beetle remains to reconstruct changes in a montane landscape over time 31 3.1.1 Changes in species composition and diversity of a montane beetle community over the last millennium in the High Tatras, Slovakia: Implications for forest conservation and management 31 Extended summary 32 3.2 Fossil bark beetle records as indicator of bark beetle outbreaks and other natural disturbances 47 3.2.1 Late Glacial and Holocene records of tree-killing conifer bark beetles in Europe and North America: Implications for forest disturbance dynamics. 47 Extended summary 48 3.2.2 Using a fossil bark beetle record as indicator of past bark beetle outbreaks in a Norway spruce mountain forest 62 Extended summary 63 3.3 Reconstructions based on insect remains from lake sediments 106 3.3.1 Postglacial succession of caddisfly (Trichoptera) assemblages in a central European montane lake. 106 Extended summary 107 4. Discussion 124 4.1 An expansion of fossil insect records in central Europe 125 4.2 Long term environmental changes reconstructed from insects 126 4.3 Natural and anthropogenic disturbances 127 4.4 Limitations of this research 132 4.5 Future studies 133 5.