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Ecosystems

, Volume 16, Issue 2, pp 295–309 | Cite as

Multi-scale Analysis of Environmental Conditions and Conifer Seedling Distribution Across the Treeline Ecotone of Northern Manitoba, Canada

  • Steven D. Mamet
  • G. Peter Kershaw
Article

Abstract

Treeline represents not only an important physiognomic boundary but also an important transition between disjunct mesoclimates and environmental limitations on establishment of tree species. The circumboreal treeline is controlled by some still to be understood physiological mechanism dependent on air temperatures, though younger life stages are increasingly influenced by numerous other biotic and abiotic factors at finer spatial and temporal scales. The goal of this study was to evaluate environmental and reproductive characteristics across treeline around Churchill, Manitoba, and to determine which factors are most important for successful seedling establishment by tamarack, white spruce and black spruce. We examined mid-winter snowpack, soil characteristics, seed viability, seedling establishment, and dominant vegetation at sites within forest and at treeline. Growing season was longer at treeline due to less snow accumulation, though soil temperatures were more variable throughout the year when compared with forest. Conifer seed germination was greater than 88% for most of the region and total seedling density was relatively consistent between sites. Seedlings were negatively associated with other plants within the forest, but low stature vegetation seemed to facilitate establishment at treeline. The associations between seedling establishment and habitat availability observed at several sites suggest that treeline advance in the Churchill area could be contingent on the facilitative effects of plants at and beyond treeline. The results of this study support the premise that fine-scale biotic and abiotic patterns and processes such as snowpack and facilitation by neighboring vegetation certainly cannot be overlooked in analyses of patterns at treeline in a changing Subarctic.

Keywords

treeline Churchill Manitoba habitat index soil temperature establishment snowpack germination forest–tundra 

Notes

Acknowledgments

This research was supported by grants from the Canadian Circumpolar Institute at the University of Alberta, the Northern Research Fund administered by the Churchill Northern Studies Centre (CNSC) and Earthwatch International (EI). This paper is a product under the International Polar Year (IPY) core project PPS Arctic as part of IPY 2007–08, sponsored by the International Council for Science and the World Meteorological Organization. We thank the staff and volunteers of the CNSC and EI for their contributions to this research. The efforts of L. Fishback, C. Basler, S. Adam, E. Oakham, J. Pelton and K. Harper were essential for completion of the fieldwork. C. Brown, A. Trant, L. Janowitch and J. Muffly assisted with germination trials. F. Berninger provided materials for the field decomposition experiment. S. Landhäusser and D. Froese graciously contributed lab space and logistical support. We also wish to thank two anonymous reviewers for their helpful comments on this paper.

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Copyright information

© Springer Science+Business Media New York 2012

Authors and Affiliations

  1. 1.Department of Earth and Atmospheric SciencesUniversity of AlbertaEdmontonCanada
  2. 2.Northern Plant Ecology Lab, Department of BiologyUniversity of SaskatchewanSaskatoonCanada

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