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Department of Physics, Chemistry and Biology Master Thesis Occurrence of insects in relation to short term forest fire history Fia Sundin LiTH-IFM- Ex--14/2903--SE Supervisor: Per Milberg, Linköping University Examiner: Karin Tonderski, Linköping University Department of Physics, Chemistry and Biology Linköpings universitet SE-581 83 Linköping, Sweden Institutionen för fysik, kemi och biologi Datum/Date Department of Physics, Chemistry and 2014-07-03 Biology Avdelningen för biologi Språk/Language InstutitionenRapporttyp för fysikISBN och mätteknik Report category LITH-IFM-A-EX—14/2903—SE Engelska/English __________________________________________________ Examensarbete ISRN D-uppsats __________________________________________________ Serietitel och serienummer ISSN Title of series, numbering Handledare/Supervisor Per Milberg URL för elektronisk version Ort/Location: Linköping Titel/Title: Occurence of insects in relation to short term forest fire history Författare/Author: Fia Sundin Sammanfattning/Abstract: Several boreal insect species are pyrophilic and are more or less dependent on recently burned forest. Many pyrophilic species are attracted to potential substratum-rich recently burned forest by smoke and heat. Modern forestry has dramatically reduced the amount and size of forest fires in northern Europe during the last century and as a result several of the pyrophilic species are now threatened. The aim of this study was to analyse how the occurrence of insects such as Diptera of the pyrophilic genus Microsania, pyrophilic Coleoptera, obligate saproxylic Coleoptera and Coleoptera with unknown fire-dependency were affected by the forest fire history during the last 14 years. The aim was also to analyse what effect the spatial and temporal scales of the forest fire history has on the occurrence of these insects. This was done using smoke attraction traps, a unique method for catching pyrophilic insects without an actual forest fire, and analysing the results with a unique regional short term forest fire history dataset, containing all fires between the years of 1998-2011 in Östergötland county in Sweden. The forest fires were clustered and more abundant in the eastern parts of the county. Seven out of eleven pyrophilic beetles were positively correlated with recent forest fires, mostly for the smaller spatial scales, 100 m – 5000 m. The abundance of many beetles with unknown fire-dependency were associated with recent forest fires. The general ecology for many of these species is not well known but some of these beetles might be favoured by different substrates that are created by fires. Strategically placed conservation burns can help to increase the spatial and temporal connectivity of forest fires to conserve both fire dependent and generally associated insects in the future. Nyckelord/Keyword: Coleoptera, Forest fire history, Microsania, Pyrophilic, Smoke attraction traps, Southern Sweden Content 1 Abstract ............................................................................................... 2 2 Introduction ......................................................................................... 2 3 Material & methods ............................................................................ 4 3.1 Study sites for the smoke attraction traps .................................... 4 3.2 Experimental setup for the smoke attraction traps ....................... 5 3.3 Sampling with smoke attraction traps .......................................... 6 3.4 Data analysis ................................................................................ 6 3.4.1 Forest fire history ...................................................................... 6 3.4.2 Statistical analyses .................................................................... 9 4 Results ............................................................................................... 10 4.1 Abundance of taxa ..................................................................... 10 4.2 Fire history & abundance of Coleoptera species ....................... 11 4.3 Occurrence of Microsania spp. in relation to the temporal and spatial scales of the fire history ............................................................ 16 5 Discussion ......................................................................................... 17 5.1 Conclusions ................................................................................ 20 5.2 Societal & ethical considerations ............................................... 21 6 Acknowledgement ............................................................................ 21 7 References ......................................................................................... 22 8 Appendix ........................................................................................... 26 8.1 PCA on pyrophilic beetles and connectivity or number of forest fires of 2007-2010 ................................................................................ 26 8.2 PCA on beetles with no or unknown fire-dependency .............. 28 8.3 Results from and list of all beetle species used in Figure 9 and Appendix 8.2 ........................................................................................ 30 1 Abstract Several boreal insect species are pyrophilic and are more or less dependent on recently burned forest. Many pyrophilic species are attracted to potential substratum-rich recently burned forest by smoke and heat. Modern forestry has dramatically reduced the amount and size of forest fires in northern Europe during the last century and as a result several of the pyrophilic species are now threatened. The aim of this study was to analyse how the occurrence of insects such as Diptera of the pyrophilic genus Microsania, pyrophilic Coleoptera, obligate saproxylic Coleoptera and Coleoptera with unknown fire-dependency were affected by the forest fire history during the last 14 years. The aim was also to analyse what effect the spatial and temporal scales of the forest fire history has on the occurrence of these insects. This was done using smoke attraction traps, a unique method for catching pyrophilic insects without an actual forest fire, and analysing the results with a unique regional short term forest fire history dataset, containing all fires between the years of 1998-2011 in Östergötland county in Sweden. The forest fires were clustered and more abundant in the eastern parts of the county. Seven out of eleven pyrophilic beetles were positively correlated with recent forest fires, mostly for the smaller spatial scales, 100 m – 5000 m. The abundance of many beetles with unknown fire-dependency were associated with recent forest fires. The general ecology for many of these species is not well known but some of these beetles might be favoured by different substrates that are created by fires. Strategically placed conservation burns can help to increase the spatial and temporal connectivity of forest fires to conserve both fire dependent and generally associated insects in the future. 2 Introduction Frequent fires were previously a common feature in the boreal forests (Zackrisson 1977, Niklasson & Granström 2000) and have probably exerted a strong selection pressure on many forest organisms. For instance, forest fires create substrates that many forest species depend on for their long term survival, including plants, fungi, beetles, Diptera and other arthropods (e.g. Wikars 1992, Granström & Schimmel 1993, Wikars 2002, Johansson et al. 2010, Hjältén et al. 2010, Ylisirniö et al. 2012). Due to modern forestry, the amount and size of forest fires in northern Europe have dramatically decreased in the last century, from being the major disturbance factor to being almost totally eliminated (Tolonen 1978, Niklasson & Granström 2000, Niklasson et al. 2010). Therefore many forest species that are dependent on forest fires are now threatened. 2 Numerous insect species are dependent on dead wood as well as heavily stressed, dying or recently dead trees. These insects sometimes display a pyrophilic behaviour since they are attracted to potential substratum-rich recently burned habitats by smoke and/or heat (Saint-Germain et al. 2008). In boreal forests, pyrophily, is thought to be widespread, and several studies have shown immediate and massive colonization of recent burns by insects (Gardiner 1957, Muona & Rutanen 1994, Wikars & Schimmel 2001, Saint-Germain et al. 2004). Several pyrophilic species are found at very high densities in recent burns, but are uncommon or rare in unburned forests. Thus, recently burned habitats are important for the long term survival of these species and the decline seen in some species has been consistently linked with a lengthening of the fire cycle related to fire suppression (Anhlund & Lindhe 1992, Wikars 1997, Jonsell et al. 1998). Therefore, one can hypothesize that the abundance of pyrophilic species would be positively related to a high abundance of forest fires in the landscape. North European boreal forests have been intensively managed the last few decades (Esseen et al. 1997, Angelstam 1998). This has affected the availability of dead wood as a result of active fire suppression. Today, less than 0.01 % of Fennoscandian forests burn annually (Granström 2001). Additionally, the dead wood volume has been reduced by 90–98 % under recent management when comparing managed landscapes with pristine forests in Finland (Siitonen 2001). Combined, this has led to the severe decline of numerous saproxylic