PARENT SESSION
Oral Session 81: Forest Ecology IV: Seeds, Growth, and Recruitment.
Presiding: J Kush
Wednesday, August 4, 1:30 PM to 5:00 PM, Meeting Room C 120.
Relationship between climate and seed maturation of Picea mariana: from continental to local scale.
Meunier, Celine*,1, Sirois, Luc2, Begin, Yves1, 1 Centre d'etudes nordiques Universite Laval-Quebec-Canada, Quebec2 Centre d'etudes nordiques Universite du Quebec-Rimouski-Canada, Rimouski
ABSTRACT- Variation in seed maturation is thought to be one important mechanism that could prompt the northern forest's response to climate change. The relation between growing degree-days and seed maturity was assessed at three spatial scales. At the continental scale, the development of female gametophytes and embryos from eleven sites distributed across Canada was followed according to the cumulating growing degree-days. Developing seed cones were harvested 3 to 5 times for every location during the 2001 growing season. At the regional scale, seed cones of the growing seasons 1998, 1999 and 2000 were collected from 8 sites in the northern Quebec. At the local scale, seed cones were harvested along shore-hinterland gradients and islands of a recently created, 2800 km2 reservoir. Our results confirm the 800 to 940 degree-days > 5 °C (DD) as the heat sum interval associated with the maturation of embryo in several black spruce populations across its range. Along a regional south to north climatic gradient, seed germination can be predicted as a sigmoid function of the growing degree days (y = 3.27 + 22.78 / [1 + e(x-904.49)/53.78]; R2 = 0.83, p< 0.0001) that reach a plateau around 800-940 DD. At the local scale, once the 800-940 DD interval is reached, variation in seed germination was mostly associated with sites factors. In the cold enclave created by hydrolectric reservoir percentage of germinated seeds was 13.8 +/- 3.5 (instead of 25.0 +/- 2.8), that is equivalent to germination rate observed at 1 to 2 degrees of latitude northwards. It is suggested that the 800-940 DD interval represent an isotherm that could enhance the regenerative potential of black spruce and trigger densification of subarctic forests.
Key words: climate, boreal forest, seed maturation, black spruce