Douglas-fir Seedlings in the Pacific Northwest: The Genetics of Drought Adaptation Erda Celer1 (erda.celer@oregonstate.edu), Glenn T. Howe1 Oregon State University, 1Department of Forest Ecosystems and Society  Abstract  Materials & Methods (cont’d)  Results & Conclusion (cont’d) Douglas-fir (Pseudotsuga menziesii) is a widely distributed, ecologically important, and commercially valuable tree species in North America. However, climate change is expected to adversely impact Douglas-fir trees, and assisted migration may become necessary to lessen the effects of climate change. Because drought stress is one of the projected effects of climate change in the western U.S., it is increasingly important to include drought adaptation traits in breeding programs and in reforestation decisions. I will discuss the design and results of a study that help increase the understanding about the importance of climatic-driven genetic differences for drought adaptation traits in Douglas-fir. The results of this study will provide useful information for understanding drought, enhancing breeding programs, and potentially adjusting forest management to climate change impacts. Heritability differed widely among traits High heritability for bud flush Genetic gains were estimated for two backward selection scenarios Table 3. Heritabilities and genetic gains of traits measured across both plantations.   Ht14 Ht15 Hinc Flush Sprague and Lost Creek Heritabilities h2 Individual 0.72 0.08 0.64 Family 0.78 0.79 0.34 0.82 Genetic gains (%) Gain1-12.5% 44 38 25 65 Gain2-2.5% 63 55 36 93 Figure 1. Sprague site (22 reps; 427 families; 6480 Douglas-fir seedlings). Large height differences in the greenhouse persist in the field Low correlation between growth in the greenhouse and drought adaptation traits  Goals The overarching goal of this study was to understand the effects of drought on the growth and survival of Douglas-fir seedlings. The long term goal of this study is to increase the understanding of the genetic capacity of Douglas-fir trees to tolerate drought stress, obtain useful information to enhance approaches for genetically improving drought adaptation traits, and enhance approaches for appropriately deploying genotypes from breeding programs. Adding to our understanding of the potential effects of climate change will help provide information for practicing effective assisted migration.   Table 4. Correlations among breeding values for Douglas-fir seedling traits measured at Sprague and Lost Creek.   Ht14 Ht15 Htinc Flush SFlush Sprague 0.97 0.06 -0.13 -0.18 0.28 -0.20 0.23 0.45 -0.31 -0.05 -0.17 0.04 0.29 0.34 0.41 0.42 0.05 Lost Creek Figure 2. Lost Creek site (17 reps; 293 families; 3449 Douglas-fir seedlings).  Results & Conclusion The Sprague site is typically hotter and drier than Lost Creek  Objectives Table 1. Geographic and climatic characteristics of the Sprague and Lost Creek plantations. Climate variables were derived from ClimateNA (Wang et al. 2012).  Experimental conclusions Obtain baseline measurements and climate data to help in the analysis and interpretation of future measurements in the Drought Hardiness Study Characterize the quantitative genetics of drought adaptation traits Determine whether drought adaptation traits are associated with the climatic origin of Douglas-fir seedlings   Test Sites Category Unit Abbr. Sprague Lost Creek Geog. ft ELEV 1067 2920 Climate °C MAT 9.8 4.6 mm MAP 875 1677 day NFFD 275 210 Julian d. FFP 184 164 PAS 52 612 EXT 37.5 29 Hypothesis 1 In the first growing season, the drought adaptation traits were genetically controlled Hypothesis 2 Drought adaptation traits and climate variables are correlated The Sprague site was hotter and drier compared to Lost Creek, and these conditions adversely affected seedling growth, damage, and survival. This suggests that the Sprague site should be good for screening drought adaptation traits Hypothesis 3 Early flushing was associated with warmer (NFFD) and drier (MSP) climates Genotypes (families) from areas with warmer and drier climates were more likely to flush early Hypothesis 4 Low correlation between Ht14 and Mort There is no relationship between height at the time of planting (Ht14) and mortality either at Sprague or at Lost Creek  Hypotheses Drought adaptation traits of Douglas-fir seedlings are partly determined by genetics Natural selection for drought adaptation traits has been stronger in areas that are warmer and drier Because of high leaf areas, tall Douglas-fir seedlings are more prone to damage from drought Early bud flush in Douglas-fir is a genetically controlled drought avoidance strategy Abbreviations: ELEV=elevation; MAT= mean annual temperature (°C); MAP=mean annual precipitation (mm); NFFD= number of frost-free days; FFP= frost-free period; PAS= proportion of precipitation as snow; EXT= extreme maximum temperature over 30 years. The trees at the Sprague site grew less, were more damaged, and had greater mortality than the trees at the Lost Creek Site Table 2. Statistics for traits measured on families of Douglas-fir seedlings in the Sprague and Lost Creek plantations.  Materials and Methods   Sprague Lost Creek N Mean StDev Ht14 427 39.97 7.407 293 42.71 6.532 Ht15 49.19 7.837 52.43 7.248 Htinc 9.21 2.263 9.72 1.908 Flush 415 1.69 0.405 292 2.61 0.558 Sflush 0.06 0.091 0.38 0.182 FD 0.53 0.217 0.16 0.134 SD 0.10 0.120 0.04 0.063 LD 0.19 0.190 0.03 0.061 Mort 0.30 0.194 0.12 0.126  Research implications This study is designed to impose substantial drought stress by focusing on sites in southern Oregon. The experiment assess about 10,000 Douglas-fir seedlings from 429 families from western Oregon and Washington that were planted at two sites: Lost Creek and Sprague. Measured variables, which I refer to as drought adaptation traits, included height, second flushing, spring bud flush, damage (foliage, stems, and leaders), and survival. Using the growth data and climate variables from ClimateNA, a climate interpolation program, we develop a model to show how genetics and environmental factors interact. Seedlots are mostly from open-pollinated seeds from first-generation parents in orchards, some of them are half-sib families created by pooling full-sib families, and two of them are woods-run seedlots from southern Oregon. We have ≤ 60 trees per family.   There were large differences in height among families in the greenhouse (Heritabilities in the greenhouse are unusually high) Randomization should be used in the greenhouse Variation in height after one year in the field largely reflected differences in growth that occurred in the greenhouse Height increment is more relevant for understanding the genetics of field growth and drought hardiness Initial measurements can be used as covariates in later analyses Either Ht14 or Ht15 can be used as an “initial height” with later height measurements to understand drought adaptation in the field Bud flush was highly heritable Flush would be amenable to genetic improvement Flush would be a good trait to use for making seed transfer distances and assisted migration Abbreviations: Ht14 (cm) is the height of the seedlings in 2014, which corresponds to the growth of the seedlings in the greenhouse; Ht15 is the height of the seedlings in 2015 at the end of the first growing season. Htinc is the difference between Ht14 and Ht15. Flush is the bud flush score in the spring of 2016; SFlush is the presence or absence of second flushing in September 2016; FD is the percentage of dead foliage; SD is the percentage of sunscald damage on the stem; LD_bin is the leader condition (1=damaged, 0=not damaged); Mort is mortality (1=dead, 0=alive).