Since the Intergovernmental Panel on Climate Change released its reports this year, there appears to be a general consensus that global climates are warming due to anthropogenic emissions of greenhouse gases (Globe & Mail 03/02/07). In addition to global warming, climate models predict more variable weather patterns, particularly more severe summer heat events and droughts (IPCC 2007: http://www.ipcc.ch/SPM2feb07.pdf). Changing weather patterns will likely affect British Columbia?s forest ecosystems in the long term, and in the short term, increased summer drought would have direct impact on survival of planted seedlings. Seedling mortality of planted Douglas-fir in the Sub-maritime Zone is currently a problem, and drought is a major contributor to this mortality. This situation is expected to worsen as climates change. There is, therefore, a critical need to know the range of drought tolerance in progeny from seed orchards producing seed for this zone.
The objective of this project is to quantify the range of drought tolerance in families of sub-maritime Douglas-fir from first-generation seed orchards.
The Douglas-fir breeding program led by the Forest Genetics Section, Research Branch, BC MOFR has developed over the past 30 years. A very high proportion of coastal and sub-maritime Douglas-fir seedlings planted each year are grown from improved seed produced in seed orchards. Evaluations of parents in the Douglas-fir breeding program are based on the performance of their progeny across a range of test sites in coastal BC. The primary selection trait is height growth which is evaluated at the end of the 3rd, 8th and 11th years of growth. The drought tolerance of progeny is only indirectly assessed in these tests because the resources are not available for repeated observations within one or more growing seasons. Therefore, the combination of proposed field tests and tests in nursery beds with the standard progeny trial measurements is a powerful way to test the degree of variation in traits of critical importance.
Generally, selections for second generation Douglas-fir seed orchards will be made in family blocks in progeny tests. However, we know little about the phenology, drought tolerance, cold hardiness or other physiological traits of these potential selections. We are uncertain how these traits will be affected by a changing climate and if we should be focusing selections based on particular traits. Thus, it is prudent to examine and characterize families in the sub-maritime Douglas-fir breeding program for a variety of fitness and growth traits.
This study will quantify the drought tolerance of families of sub-maritime Douglas-fir from first-generation seed orchards. Field sampling of 45 families planted in 2005 in progeny tests in three locations will reveal family differences in mid-summer whole-plant water potential measured with a plant pressure chamber. Stable carbon isotope analysis will show family differences in water use efficiency. A complementary pot trial will test 20 randomly selected families in 3 drought treatments at the UVic field test site. Whole plant biomass allocation, root morphology, plant water potential and photosynthesis will be analyzed.
We predict that we will find differences among families in long-term water use efficiency. Results will indicate which families in the sub-maritime Douglas-fir tree improvement program have the greatest long-term water use efficiency and what trade-off exists between water use efficiency and growth. The pot trial will allow us to investigate the physiological and morphological mechanisms leading to greater water use efficiency. Results will have direct application to Douglas-fir family selection in the BCMoFR Forest Genetics Program, and will help breeders to select families which will continue to perform well in the face of decreasing annual rainfall.