title: Increased tree establishment in Lithuanian peat bogs--insights from field and remotely sensed approaches.
abstract: Over the past century an ongoing establishment of Scots pine (Pinus sylvestris L.), sometimes at accelerating rates, is noted at three studied Lithuanian peat bogs, namely Kerėplis, Rėkyva and Aukštumala, all representing different degrees of tree coverage and geographic settings. Present establishment rates seem to depend on tree density on the bog surface and are most significant at sparsely covered sites where about three-fourth of the trees have established since the mid-1990s, whereas the initial establishment in general was during the early to mid-19th century. Three methods were used to detect, compare and describe tree establishment: (1) tree counts in small plots, (2) dendrochronological dating of bog pine trees, and (3) interpretation of aerial photographs and historical maps of the study areas. In combination, the different approaches provide complimentary information but also weigh up each other's drawbacks. Tree counts in plots provided a reasonable overview of age class distributions and enabled capturing of the most recently established trees with ages less than 50 years. The dendrochronological analysis yielded accurate tree ages and a good temporal resolution of long-term changes. Tree establishment and spread interpreted from aerial photographs and historical maps provided a good overview of tree spread and total affected area. It also helped to verify the results obtained with the other methods and an upscaling of findings to the entire peat bogs. The ongoing spread of trees in predominantly undisturbed peat bogs is related to warmer and/or drier climatic conditions, and to a minor degree to land-use changes. Our results therefore provide valuable insights into vegetation changes in peat bogs, also with respect to bog response to ongoing and future climatic changes.
authors.affiliation: Dendrolab.ch, Institute of Geological Sciences, University of Berne, Baltzerstrasse 1+3, CH-3012 Berne, Switzerland. Electronic address: johannes.edvardsson@dendrolab.ch.
authors.forename: Johannes
authors.initials: J
authors.lastname: Edvardsson
authors.affiliation: Department of Geography and Land Management, Faculty of Natural Sciences, Vilnius University, Lithuania.
authors.forename: Rasa
authors.initials: R
authors.lastname: Šimanauskienė
authors.affiliation: Nature Research Centre, Akademijos str. 2, LT-08412 Vilnius, Lithuania.
authors.forename: Julius
authors.initials: J
authors.lastname: Taminskas
authors.affiliation: Nature Research Centre, Akademijos str. 2, LT-08412 Vilnius, Lithuania.
authors.forename: Ieva
authors.initials: I
authors.lastname: Baužienė
authors.affiliation: Dendrolab.ch, Institute of Geological Sciences, University of Berne, Baltzerstrasse 1+3, CH-3012 Berne, Switzerland; Climatic Change and Climate Impacts, Institute for Environmental Sciences, route de Drize 7, CH-1227 Carouge-Geneva, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Stoffel
mesh_terms: D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods*; D016468:Forestry / Q000379:methods; D008097:Lithuania; D058998:Remote Sensing Technology; D012987:Soil; D014197:Trees / Q000254:growth & development*; D053833:Wetlands
chemical_list: D012987:Soil
keywords: Aerial photographs; Climate change; Dendrochronology; Historical maps; Land-use change; Pinus sylvestris L