Group members active at European Congress of Conservation Biology in Jyväskylä

All the members of our group are sharing the highlights of our current research in the ECCB congress, starting next Tuesday, 12.6.2018 in Jyväskylä. In the congress, our sessions are at Tuesday (poster, Juni and Niko, Forest Management and Biodiversity session), Wednesdey (talk by Tuomas, Ecological processes in forest ecosystems session), Thursday (talk by Timo, Natural disturbance emulation in forest conservation and sustainable ecosystem management session, also co-chaired by Timo), and Friday (talk by Niko, Forest Management and Biodiversity II session). Tuomas also chairs the “Human-Wildlife conflicts” session at Wednesday. Come to meet us and share your ideas!

Legacies of past wildfires continue to influence the development of northern boreal forests long after the fires have disappeared

Forest fires were historically the most impor­tant disturbance agent in the northern European boreal forest, but have virtually disappeared in the 20th century. However, past fires have left persistent legacies in forest structure and, due to their strong influence on forest age structures, continue influencing forest dynamics long since their disappearance. It is hence clear that we need knowledge on past fire occurrence, to be able to attribute the changes we observe in the forest to their drivers.

We reconstructed past fires in three northern boreal landscapes (each 2 km x 2 km) in Värriö and Maltio strict nature reserves in northeastern Finland. For the reconstructions, we used dendrochronological methods (i.e., methods based on tree ring widths), and described the occurrence of fires in the past 300 years. For these three landscapes, the average fire cycles (a measure of fire activity) were 72 and 156 years in Scots pine-dominated landscapes, and 579 years in a Norway spruce-dominated land­scape. The numbers of fires during the past three centuries were clearly related with soil properties: forests on soils that retain water better had experienced fewer fires than forests on coarser soils with lower water holding capacity.

Tree age structures that we determined from 1800 live and dead trees showed strong age cohorts that were associated with large fires in two of the landscapes. The y-axis shows the cumulative number of trees – each horizontal line represents the life span of an individual tree. Years indicated fires that influenced most parts of the study landscape.

It is noteworthy that although tree growth and regeneration in these northern regions are considered highly climate-sensitive, fires have been a major driver of forest dynamics in these areas. It is also clear that the continued absence of fires will lead to considerable changes in the forest structure and species composition in the future, even if the reserves are strictly protected from direct human influence.

The study is accepted for publication in Boreal Environment Research (fully open access journal), and a link will appear here (hopefully) soon.

Dead standing pine trees in a boreal forest landscape in the Kalevala National Park

We examined and mapped the amount, structural features, site characteristics and spatial distribution of dead standing pine trees over a ten hectare area in an unmanaged boreal forest landscape in the Kalevala National Park in Russian Viena Karelia. After their death, Scots pine trees can remain standing for decades and sometimes up to 200 years, forming long-lasting and ecologically important structures in boreal forest landscapes. Standing dead pines decay very slowly and with time develop into ‘kelo’ trees, which are characterized by hard wood with silvery-colored appearance. These kelo trees represent an ecologically important, long lasting and visually striking element of the structure of natural pine-dominated forests in boreal Fennoscandia that is nowadays virtually absent from managed forest landscapes. See study here.

Above: Examples of different kelo structures contributing to forest structural and substrate diversity. (a) A fairly recently died partly debarked tree (often fall of bark is accelerated by woodpecker foraging). (b) Old kelo tree with fire scarring and charred wood in the trunk base. (c) A kelo with a cavity. The tree was made hollow by the Boreal Carpenter Ant (Camponotus herculeanus). (d) A large hollow broken kelo tree; such hollow broken trees are used for nesting by e.g. the Great Grey Owl. Photographs by Timo Kuuluvainen.


Variability in climate historically influenced forest fire occurrence at multiple time scales in Fennoscandia

By compiling all available tree ring based fire history reconstructions, and a set of temperature and precipitation reconstructions, we analyzed how climate had influenced the occurrence of forest fires in Finland and the adjacent regions in western Russia. Our analyses were based on Bayesian scale-space methods, that made it possible to assess these fire-climate linkages over different time scales. In the analyses, we saw the well-documented relationship between fires and weather conditions during individual summers (high fire activity was related to dry summers). However, and somewhat surprisingly, fires and climate (summer temperature, and especially summer precipitation) were also very clearly related to one another at longer, approximately decadal, time scales. The result of this work, as a collaboration between our group, Department of Geosciences and Geography of University of Helsinki, and the Department of Mathematical Sciences at the University of Oulu, is now available in Ecological Monographs.

Historically, the synchrony of fire occurrence in different parts of the region was related to drought.

Biological “archives” carry reliable information of past temperatures for all four seasons in Finland

In a joint study with several research groups at the University of Helsinki and Aalto University, we compiled a collection of records on different biological and physical phenomena, to assess their reliability as an indicator of past temperatures for different seasons. This collection included different characteristics of tree rings, and plant and ice phenology. Our assessment showed how different combinations of these temperature indicators provided reliable information on the temperatures of all four seasons, as well as annual temperatures. See the full paper in Plos one.

A review paper out on forest ecosystem management in Oxford Research Encyclopedia of Environmental Sciences

Kuuluvainen, T. 2016. Ecosystem management of the boreal forest. Oxford Research Encyclopedia of Environmental Sciences. DOI: 10.1093/acrefore/9780199389414.013.15

The paper reviews the current understanding and ideas of ecosystem management when applied to the boreal forest. Declines in managed forest biodiversity and structural complexity, combined with rapidly changing climatic conditions, can pose a risk to forest health and long-term provisioning of important ecosystem goods and services. I concluded that ecosystem management in the boreal forest calls for a transition from plantation-type forestry towards more diversified management inspired by natural forest structure and dynamics.

Take a look at the article here

Determining tree stem volume in R, using taper curves

Taper curves (i.e., functions describing the shape of a tree stem) can be used for conveniently computing the volume of a tree stem, using volume integrals, but they are not very commonly used in ecological research. The curves and their volume integrals are particularly convenient for computing the volume of snapped trees, where the shape of the stem (taper) is determined by the tree diameter and the height of the tree before snapping, and the volume is computed from the base of the tree to the snapping height (or any other point along the stem). Same functions can be used to compute the volume of a fallen part of a snapped tree just as easily.

We’ve written an easy-to-use R-script for several tree species in regions we are working in, based on previously published taper curves: Scots pine, Norway spruce, and birch in Finland, as well as black spruce and balsam fir in Quebec, Canada. Take a look at the script here.


North Fennoscandian mountain forests: past, present and future

Mountain forests of northern Fennoscandia are often referred to as “Europe’s last wilderness”. In a recent paper, written jointly with Bengt-Gunnar Jonsson (Mid-Sweden University) and Annika Hofgaard (Norwegian Institute for Nature Research) we reviewed the history, current state and discuss the unpredictable future of these forests.

See the full paper here, or access the pre-print version here.


New paper out in Hydrobiologia

A new paper on light availability effects on aquatic macrophyte community formation, utilizing variance partitioning approach, has been published online in Hydrobiologia. The paper was a joint effort with Hanna Luhtala, Harri Tolvanen and Risto Kalliola from the section of Geography, University of Turku.

Click here for the paper.