«Wood ants (Formica rufa group) in managed boreal forests: implications for soil properties and tree growth Jouni Kilpeläinen Faculty of Forest ...»
Dissertationes Forestales 66
Wood ants (Formica rufa group) in managed boreal
forests: implications for soil properties and tree growth
Faculty of Forest Sciences
University of Joensuu
To be presented, with the permission of the Faculty of Forest Sciences of the
University of Joensuu, for public criticism in auditorium M4, Yliopistokatu 7,
Joensuu, on 23rd May 2008 at 12 o’clock noon.
Title of dissertation: Wood ants (Formica rufa group) in managed boreal forests:
implications for soil properties and tree growth Author: Jouni Kilpeläinen Dissertationes Forestales 66
Prof. Leena Finér, Finnish Forest Research Institute, Joensuu Research Unit, Finland Prof. Pekka Niemelä, Faculty of Forest Sciences, University of Joensuu, Finland
Prof. Jarmo Holopainen, Department of Environmental Science, University of Kuopio, Finland Doc. Raija Laiho, Department of Forest Ecology, University of Helsinki, Finland
Prof. Heikki Setälä Department of Ecological and Environmental Sciences, University of Helsinki, Lahti, Finland ISSN 1795-7389 ISBN 978-951-651-220-7 (pdf) (2008)
Finnish Society of Forest Science Finnish Forest Research Institute Faculty of Agriculture and Forestry of the University of Helsinki Faculty of Forest Sciences of the University of Joensuu
Finnish Society of Forest Science Unioninkatu 40A, 00170 Helsinki, Finland http://www.metla.fi/dissertationes Kilpeläinen, J. 2008. Dissertationes Forestales 66. 33 p. Wood ants (Formica rufa group) in managed boreal forests: implications for soil properties and tree growth.
Available at http://www.metla fi/dissertationes/df66.htm
ABSTRACTMound-building ants, and especially wood ants (Formica rufa group), are wide-spread key species that affect ecosystem functioning in several ways in the boreal forests of Eurasia.
Forest clear-cutting harms wood ants, but the colonies gradually recover and multiply as forest succession proceeds. Thus their impact on ecosystem functioning may change with stand age.
The objectives of this thesis were to study 1) the distribution of wood ants in boreal forests,
2) the role of wood ant mounds in the distribution of nutrients and roots, and 3) the effect of wood ant-aphid mutualism on the growth of Norway spruce (Picea abies L. Karst.). The 3rd National Forest Inventory data from the 1950s was used to study the distribution of ant mounds along major ecological gradients in Finland. Ecosystem-scale studies were conducted in 5-, 30-, 60- and 100-year-old Norway spruce dominated stands in eastern Finland.
The highest mound densities were found in spruce- and birch-dominated mature forests on medium-fertile sites in southern Finland. Ant mounds were more numerous and larger in older than in younger stands. More mound-building ant species were found in younger stands, while F. aquilonia Yarr. was the only species in the oldest stands. Most ant mounds were situated near stand edges. Carbon (C), nitrogen and phosphorus concentrations were higher in ant mounds than in the surrounding soil. More fine roots were found in the mineral soil under ant mounds than in the surrounding mineral soil. Ant mounds contributed only a small proportion of the total C and nutrient pools and root biomass in forest soil. Ant-aphid mutualism significantly reduced the radial growth of individual spruce trees in the 30-year-old stands only. Overall, the impact on spruce growth was marginal at the stand level. However, wood ants increased the heterogeneity in the spatial distribution of C, nutrients, roots, and tree growth.
Keywords: Norway spruce, nutrient content, roots, spatial distribution, species turnover, succession
ACKNOWLEDGEMENTSI thank Prof. Leena Finér, who as the leader of the ANTS project (“Do wood ants play an important role in carbon and nutrient dynamics in boreal managed forests?” funded by the Academy of Finland, 2003–2006, project 200870), provided me with the opportunity to carry out the study. I am grateful to Profs. Leena Finér and Pekka Niemelä for supervising my work.
Thanks to the co-authors of articles for cooperation during these years: Prof. Leena Finér, Dr. Timo Domisch, Prof. Martin Jurgensen, Dr. Seppo Neuvonen, Prof. Pekka Niemelä, Dr.
Mizue Ohashi, Mr. Pekka Punttila, Dr. Anita Risch and Prof. Liselotte Sundström. Mr. Urho Kettunen helped in setting up and maintaining the field experiments. Mr. Pertti Karvinen and Mr. Matti Jyrkinen assisted him in 2003 and Mr. Raino Lievonen in 2006. Ms. Paula Jänönen and Dr. Timo Domisch participated in the ant mound inventory in 2003. Mr. Pekka Punttila identified the ant specimens. Dr. Timo Domisch (2003–2005), Ms. Paula Jänönen (2003), Ms.
Laura Ikonen (2003, 2005), Mr. Teuvo Vauhkala (2003), Dr. Mizue Ohashi (2004–2005), Mr.
Jouko T. Ylönen (2004), Mr. Mikko Tala (2004), Ms. Tanja Honkasaari (2004), Ms. Niina Lehikoinen (2005), Ms. Hanne Vaarala (2005) and Mr. Kai-Mikael Hyvärinen (2006) took part in the ant traffic monitoring and the tree measurements. Dr. Timo Domisch, Ms. Laura Ikonen and Mr. Teuvo Vauhkala participated in collecting the mound and soil samples in 2003, and additionally, Ms. Anita Pussinen, Ms. Seija Repo and Mr. Pekka Järviluoto helped with the preliminary treatments of the samples, and Ms. Anki Geddala, Ms. Sirpa Piirainen and Ms.
Maini Mononen with the practical arrangements for the nutrient analyses. Dr. Timo Domisch, Ms. Laura Ikonen, Ms. Marja Kuskelin, Mr. Teuvo Vauhkala, and Mr. Tapio Ylimartimo helped in measuring the tree sample plots in 2003, and Mr. Veikko Laakkonen, Ms. Hely Martikainen and Mr. Markku Tiainen in 2006. Mr. Tapio Ylimartimo performed the tree ring analyses. Ms. Leena Karvinen (2003) and Ms. Niina Lehikoinen (2005) entered part of the data. Mr. Jaakko Heinonen guided in the statistical analyses. The Koli National Park, UPM, Tornator and a private forest owner provided the study areas. The University of Joensuu, Faculty of Forestry (08/2002–10/2004) and the Finnish Forest Research Institute, Joensuu Research Unit (11/2004–2008) provided my working facilities. The study was funded by the Academy of Finland, project 200870 (01/2003–02/2006); University of Joensuu, Faculty of Forestry (03/2006–06/2006); the Finnish Society of Forest Science (07/2006-12/2006), Jenny and Antti Wihuri Foundation (2007), the Graduate School of Forest Sciences (01–06/2008), and Säätiö Gustaf B. Thordénin Karjalan lahjarahasto (2008). I acknowledge the thesis preexaminers Doc. Raija Laiho and Prof. Jarmo Holopainen for their valuable comments. I thank Dr. John Derome for revising the text and Ms. Leena Karvinen for making text layout. My sincere thanks go to all these people and bodies for making this work possible. Finally, I express my deepest gratitude to my loving wife Mia, sons Joel and Jeeli, parents, siblings, grandparents, parents-in-law, and the other close relatives and friends for their constant care and support. As a researcher I believe in the words of Sir Winston Churchill: “Now this is not the end. It is not even the beginning of the end. But it is, perhaps, the end of the beginning.” Joensuu, April 2008 Jouni Kilpeläinen LIST OF ORIGINAL ARTICLES (I–V) The thesis is based on the following articles, which are referred to in the text by their Roman numerals.
I. Kilpeläinen, J., Punttila, P., Sundström, L., Niemelä, P. & Finér, L. 2005.
Forest stand structure, site type and distribution of ant mounds in boreal forests in Finland in the 1950s. Annales Zoologici Fennici 42: 243–258.
II. Kilpeläinen, J., Punttila, P., Finér, L., Niemelä, P., Domisch, T., Jurgensen, M. F., Neuvonen, S., Ohashi, M., Risch, A. C. & Sundström, L. 2008. Distribution of ant species and mounds (Formica) in different-aged managed spruce stands in eastern Finland.
Journal of Applied Entomology 132: 315–325. doi: 10.1111/j.1439-0418.2007.01244.x.
III. Kilpeläinen, J., Finér, L., Niemelä, P., Domisch, T., Neuvonen, S., Ohashi, M., Risch, A. C. & Sundström, L. 2007. Carbon, nitrogen and phosphorus dynamics of ant mounds (Formica rufa group) in managed boreal forests of different successional stages. Applied Soil Ecology 36: 156–163. doi:10.1016/j.apsoil.2007.01.005.
IV. Ohashi, M., Kilpeläinen, J., Finér, L., Risch, A. C., Domisch, T., Neuvonen, S. & Niemelä, P. 2007. The effect of red wood ant (Formica rufa group) mounds on root biomass, density, and nutrient concentrations in boreal managed forests. Journal of Forest Research 12: 113–119. doi: 10.1007/s10310-006-0258-z.
V. Kilpeläinen, J., Finér, L., Neuvonen, S., Niemelä, P., Domisch, T., Risch, A. C., Jurgensen, M. F., Ohashi, M., & Sundström, L. Does the mutualism between ants (Formica rufa group) and Cinara aphids affect Norway spruce growth? Manuscript.
I participated in designing the study and was responsible for collecting the field data for the last four papers. I wrote the first manuscripts of the papers I–III and V, and analysed the data in paper IV and participated in the writing work. Articles I–IV are reprinted with kind permission of the publishers: Finnish Zoological and Botanical Publishing Board (I), WileyBlackwell (II), Elsevier (III) and Springer (IV).
LiST Of ORiGiNAL ARTiCLES (i-v)
1.1 Wood ant distribution
1.2 Role of wood ants in forest ecosystems
1.3 Objectives of the thesis
2 MATERiAL AND METHODS
2.1 3rd National forest inventory data (i)
2.2 intensive studies (ii–v)
Study stands (II–V)
Ant mound survey (II)
Carbon and nutrient and root sampling (III–IV)
Norway spruce growth (V)
3 RESULTS AND DiSCUSSiON
3.1 Distribution of ant mounds in boreal forests (i)
3.2 Distribution of ant species and mounds in Norway spruce stands (ii)
3.3 Carbon and nutrient concentrations and pools of wood ant mounds (iii)................ 19 3.4 Root distribution in wood ant mounds (iv)
3.5 Effect of ant-aphid mutualism on Norway spruce growth (v)
3. implications of wood ants for the prerequisites of tree growth
4 CONCLUSiONS AND fUTURE RESEARCH NEEDS
1.1 Wood ant distribution Hölldobler and Wilson (1990) stated that ”the neglect of ants in science and natural history is a shortcoming that should be remedied, for they represent the culmination of insect evolution, in the same sense that human beings represent the summit of vertebrate evolution.” However, ants are much older than humans since they evolved more than 100 million years ago. Some 12 200 ant species in 20 subfamilies have been described so far (Bolton 2003). Ant species diversity is enormous especially in the tropics where dozens of ant species can be found in a single tree (e.g. Longino et al. 2002). About 60 ant species can be found in Finland (Söderman and Vikberg 2002; Vepsäläinen 2002; Czechowski and Radchenko 2006), and 12 of them build mound nests (Collingwood 1979; Punttila et al. 1991; 1994a; Punttila 1996; Seifert 2000; Mabelis and Korczynska 2001; Sundström et al. 2005).
Mound-building ant species are wide-spread in the boreal forests of Eurasia (e.g. Gößwald et al. 1965; Baroni Urbani and Collingwood 1977; Reznikova 2003). Wood ants of the Formica rufa group (F. aquilonia Yarr., F. polyctena Först., F. rufa L., F. lugubris Zett. and F. pratensis Retz.) are extremely common in many forest habitats and can be found throughout Finland from the hemi-boreal to the sub-arctic zone (Wuorenrinne 1974; Rosengren et al. 1979; Laine and Niemelä 1989). F. aquilonia, F. polyctena and F. lugubris are abundant throughout the whole country (Wuorenrinne 1974; Baroni Urbani and Collingwood 1977; Rosengren et al.
1979; Laine and Niemelä 1989; Punttila and Kilpeläinen 2008), whereas F. rufa occurs mainly in the hemi- and south-boreal forests (Wuorenrinne 1974; Punttila and Kilpeläinen 2008). On the average, three mounds per hectare occur on the most common forest site types in Finland (Wuorenrinne 1974; Rosengren et al. 1979; Domisch et al. 2005), and the mounds are often inhabited by several hundreds of thousands ants (Hölldobler and Wilson 1990). Other moundbuilding species, F. uralensis Ruzs., F. truncorum Fabr., F. exsecta Nyl., F. fennica Seifert, F.
forsslundi Lohm., F. pressilabris Nyl., F. suecica Adlerz, are common in young, open forests, meadows or mires (Collingwood 1979; Punttila et al. 1991; 1994b; Punttila 1996; Punttila and Haila 1996; Seifert 2000; Mabelis and Korczynska 2001).
Colonization of an area by ants depends on the habitat requirements and the dispersal and colonization capacities of the species, as well as potential species interactions (Vepsäläinen and Pisarski 1982). The ant species composition also changes with stand age: pioneering ant species capable of independent colony establishment (e.g. F. fusca L.) are followed by species employing temporary social parasitism during colony founding (e.g. monogyne wood ant species). Later on, because of the intensified competition among the established colonies, only spreading through colony budding may remain a competitive colonization strategy (e.g. as in polygyne wood ant species) (Rosengren and Pamilo 1983; Punttila et al. 1991; Rosengren et al. 1993; Punttila et al. 1994b; Seppä et al. 1995; Punttila 1996; Punttila et al. 1996; see also Oinonen 1956). Long-range dispersal ability is generally considered to be better in monogyne (one queen) and weakly polygyne (a few queens) species, whereas short-range dispersal through the formation of bud nests dominates in polygyne (several queens per colony) species (Rosengren and Pamilo 1983; Rosengren et al. 1993; Sundström et al. 2005). Monogyne and monodomous (single nest colony) wood ant species (most Finnish populations of F. rufa, F.
lugubris, F. pratensis) are more common in younger stands and fragmented mature forests, whereas polygyne and polydomous species (F. aquilonia, F. polyctena) thrive in continuous mature forests (Rosengren and Pamilo 1983; Savolainen and Vepsäläinen 1988; 1989;