PARENT SESSION
Poster Session 37: Forest Ecology.
Thursday, August 5 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.
The effect of natural atmospheric CO2 fertilization suggested by open-grown white spruce in a dry environment.
Wang, Geoff *,1, Chhin, Sophan2, Bauerle, William3, 1 Department of Forestry and Natural Resources, Clemson, SC, USA2 Department of Renewable Resources, Edmonton, AB, Canada3 Department of Horticulture, Clemson, SC, USA
ABSTRACT- Evidence of an atmospheric CO2 fertilization effect on radial growth rates was found through examining climate-growth relationships of open-grown white spruce in a mixed-grass prairie of southwestern Manitoba, Canada. Consistent upward trends of the residuals from dendroclimatic models indicated a decreased ability for climatic parameters to predict radial growth. Despite an identical amount (62%) of the total variation in radial growth index was explained for both young (chronology length from 1953-2000) and old (chronology length 1900-1997) trees, young trees (R2 = 0.551, p < 0.001) demonstrated a stronger upward trend than old trees (R2 = 0.020, p = 0.166). Similar to young trees, the early growth period (1900-1929) of old trees also demonstrated stronger (R2 = 0.388, p < 0.001) upward trend than the entire chronology (1900-1997). Likewise, a comparable period (1970-1999) of young trees also demonstrated stronger (R2 = 0.585, p < 0.001) upward trend than the early growth period (1900-1929) of old trees. In addition, post-drought growth response was much stronger (p = 0.006) for young trees (1970-1999) compared to old trees (1900-1929) at the same development stage but did not differ (p = 0.199) between early (1900-1929) and late (1970-1999) periods within old trees. Together, our results suggest that open-grown white spruce trees displayed a strong upward trend with time at their early developmental stage and (2), at the same developmental stage, greater response occurred in the late period when atmospheric CO2 concentration was high. While it is impossible to rule out other factors, these results are consistent with expectations for CO2 fertilization effects.
Key words: Global change, Dendrochronology, Picea glauca, Tree ring