Jonathan J. Ruel, Matthew P. Ayres. (1996). Variation in temperature responses among populations of Betula papyrifera. Silva Fennica vol. 30 no. 2–3 article id 5582. https://doi.org/10.14214/sf.a9227

Keywords: Betula papyrifera; adaptation; photosynthesis; growth; temperature; climate warming; elevation

Abstract | View details | Full text in PDF | Author Info

How will global warming affect southern populations of boreal trees? In paper birch, Betula papyrifera (Betulaceae), alpine trees with an evolutionary history of relatively cool summers may be more sensitive to climate warming than valley populations. We evaluated this scenario by growing seedlings from different populations in four temperature treatments (mountain field site, valley field site, and two greenhouse rooms).

Populations from low elevations germinated earlier and had higher germination success than population from high elevations (16.8 vs. 22.0 d; 72% vs. 11%). At the valley site, seedlings from native populations grew faster than seedlings from higher elevations (mean ± SE = 0.25 ± 0.02 vs. 0.09 ± 0.04 mm · cm^-1 ·d^-1) while at the mountain site, all seedlings grew at similar rates. Seedling grown in cooler environments had higher root : shoot ratios, perhaps to compensate for temperature limitations in nutrient uptake by roots. Leaf area varied among populations but was not affected by environmental differences across the field sites. Net photosynthetic rates at valley temperatures were higher for seedlings grown in the valley than for seedling grown in the mountains or the warm greenhouse (12.0 vs. 10.3 and 5.8 μmoles · m^-2 · s^-1), perhaps due to adaptive phenotypic adjustments. Climatic warming could rapidly produce important phenotypic changes in birch trees (e.g. decreased root : shoot ratio, reduced growth in alpine populations). On a longer time-scale, warming could also result in genetic changes as natural selection favours valley genotypes in alpine sites where they are presently rare.

Ruel, E-mail: jr@mm.unknown
Ayres, E-mail: ma@mm.unknown

Category : Research article

article id 964, category Research article

Liisa Huttunen, Matthew P. Ayres, Pekka Niemelä, Susanne Heiska, Riitta Tegelberg, Matti Rousi, Seppo Kellomäki. (2013). Interactive effects of defoliation and climate change on compensatory growth of silver birch seedlings. Silva Fennica vol. 47 no. 3 article id 964. https://doi.org/10.14214/sf.964

Keywords: root; shoot ratio; biomass; Betula pendula; elevated CO2; elevated temperature; folivory

Highlights: The main components affecting growth compensation in silver birch seedlings are the timing and severity of foliage damage; The ability to compensate growth is also dependent upon the limits of temperature and nutrient availability; The responses of birches imply that folivory does not necessarily lead to reduced net productivity under changing climate

Abstract | Full text in HTML | Full text in PDF | Author Info

Atmospheric warming increases the abundance of insect herbivores and intensifies the risk of defoliation, especially in high latitude forests. At the same time, the effects of increasing temperature and CO₂ on plant responses to foliage damage are poorly understood. We examined if previous-year defoliation, varying between 0 and 75% of total leaf area, and different combinations of elevated temperature, CO₂ and nutrient availability alter the growth of two-year old silver birch (Betula pendula Roth) seedlings. We measured the greatest height growth in seedlings that were fertilized and defoliated twice at the level of 50% of total leaf area, and subjected to elevated temperature with ambient CO₂. The lowest growth was recorded in unfertilized seedlings that were defoliated twice at the level of 25% of total leaf area, and grew under ambient temperature with ambient CO₂. The total biomass increased in all seedlings that were fertilized or grew under elevated temperature. The root: shoot ratios were low in defoliated seedlings, or seedlings subjected to fertilization or temperature elevation. Our conclusion is that ability of birches to compensate height growth is highly dependent upon the magnitude and frequency of defoliation on the limits of temperature and nutrient availability. These responses imply that folivory does not necessarily lead to reduced net productivity of trees under changing climate.

Huttunen, Section of Ecology, Department of Biology, University of Turku, FI-20014 Turku, Finland E-mail: liisa.huttunen@utu.fi
Ayres, Biological Sciences, Dartmouth College, Hanover, NH 03755, USA E-mail: matt.ayres@dartmouth.edu
Niemelä, Section of Biodiversity and Environmental Science, Department of Biology, University of Turku, FI-20014 Turku, Finland E-mail: pekka.niemela@utu.fi
Heiska, The Finnish Forest Research Institute, Punkaharju Unit, Finlandiantie 18, FI-58450 Punkaharju, Finland E-mail: susanne.heiska@metla.fi
Tegelberg, Digitarium - Digitization Centre of the Finnish Museum of Natural History and the University of Eastern Finland, Joensuu Science Park, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: riitta.tegelberg@helsinki.fi
Rousi, The Finnish Forest Research Institute, Vantaa Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: matti.rousi@metla.fi
Kellomäki, Faculty of Science and Forestry, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: seppo.kellomaki@uef.fi

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