Canadian Forest Service Publications
Assessing the influence of climate–water table interactions on jack pine and black spruce productivity in western central Canada. 2015. Bouriaud, O.; Frank, D.; Bhatti, J.S. Ecoscience 21(3-4):315-326.
Available from: Northern Forestry Centre
Catalog ID: 36521
CFS Availability: PDF (request by e-mail)
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The changes in temperature and precipitation regimes predicted for boreal regions are expected to profoundly affect the productivity of trees situated on waterlogged soils, which underlie large areas of boreal forest in Canada. The consequences for productivity of climatic variation likely depend on site ecology and differ between species. To investigate potential site-dependent responses to climate, we compared the growth of jack pine (Pinus banksiana) trees growing within the same climate conditions but along a transect extending from a fen margin to a sandy ridge. On the fen-margin site, black spruce trees (Picea mariana) were also sampled, allowing for a comparison of the sensitivity of both species. Growth variations at interannual and decadal frequency were analyzed from tree-rings. Our study revealed that the response to climate varied substantially between sites, but, surprisingly, trees growing on the fen margin proved to be very sensitive to fluctuations of precipitation at both interannual and decadal time scales. Black spruce trees responded more sensitively to climate variation than jack pine sampled at the same site. Our study also showed a modest response to temperature even in the driest site. For both species, decadal signals show precipitation as a common, strong productivity driver regardless of water table constraints. These results suggest that the predicted climate warming is therefore less of a threat to the productivity of peatland forested zones than fluctuations in the precipitation regime. Changes in precipitation are expected to have much stronger consequences at both interannual and decadal time scales than projected temperature fluctuations.
Plain Language Summary
The boreal forest is expected to be profoundly affected by climate change. This study was conducted to understand how changes in temperature and rainfall might affect different tree species and trees growing in different types of soils. To do this, scientists looked at the yearly growth rings of two trees: jack pine trees growing at sites that varied in wetness, from the edge of a peatland to a sandy ridge, and black spruce trees growing at the edge of the peatland. The study showed which trees were the most sensitive to changes in climate—that is, which trees’ growth changed the most when the temperature or rainfall changed. It found that trees growing in the wettest (edge of peatland) and driest (sandy ridge) sites were the most sensitive to changes in rainfall, both from year to year and over decades. It was a surprise that tree growth is affected by rainfall even at the edge of peatlands, which are very wet areas in any case. Black spruce trees were dramatically more sensitive than jack pine, which may be because the trees have different root systems. It appears from this study that changes in rainfall affect tree growth more than changes in temperature, so higher temperatures may not be as big a threat as drought.
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