<p> 1Electronic Supplementary Material Legends</p><p>2</p><p>3S1 A comparison of daily averages of mean, maximum, and minimum temperatures (±1SE) in </p><p>4air (+1 m, Tair) and soil (-5 cm, Tsoil) at 2,450 and 3,000 m during the 2006 growing season </p><p>5(temperature was logged every 30 minutes from 29 June – 15 Sept 15 2006)</p><p>6</p><p>7S2. Mean (±1SE) gas exchange, growth, and nonstructural carbohydrate values for P.menziesii </p><p>8and A.lasiocarpa seedlings grown at 2,450 m and 3,000 m throughout the 2006 growing season.</p><p>9</p><p>10S3. Root respiration calculation: As a crude assessment of the reliability of our whole-plant gas </p><p>11exchange and growth measurements, we estimated a complete carbon balance for subject </p><p>12seedlings over the entire 2006 growing season. Anet of whole crowns integrated over the entire </p><p>- 132006 growing season, when averaged over all species and elevations, was 1.92 mmol CO2 crown</p><p>141 season-1 (23.01 mg C season-1), and mean dry mass gain of seedlings was 34.6 mg. Assuming </p><p>1542 to 51% of this dry mass is carbon (from Units and Conversions table in Larcher 2004), then </p><p>16mass gain of carbon per seedling would have been 14.6 to 17.7 mg C. Assuming carbon gain of </p><p>17the whole plant equals net carbon uptake of the crown plus carbon loss from roots, then 5.3 to </p><p>188.5 mg C could be attributable to root efflux. Thus, approximately 20% of the gross carbon </p><p>19uptake could be attributable to respiration or other carbon loss from roots. Although this </p><p>20estimate seems plausible, empirical data on respiration at the root or whole-plant level are scarce </p><p>21in the literature (see Atkin et al. 2005 for references), and we do not have reliable root respiration</p><p>22to verify this value. </p><p>23</p><p>1 1 24S4. Mid-season and end-season mean (±1 SE) Fv/Fm values for Pseudotsuga menziesii (square </p><p>25symbols) and Abies lasiocarpa seedlings (round symbols) grown at 2,450 m (solid) and 3,000 m </p><p>26(open).</p><p>27</p><p>28</p><p>29</p><p>30</p><p>31</p><p>32</p><p>33</p><p>34</p><p>35</p><p>36</p><p>2 2 37</p><p>38S1</p><p>39 Elevation 2,450 m 3,000 m 40 Tsoil 41 mean 13.5 ±0.7 11.6 ±0.7 max 20.6 ±0.9 22.9 ±1.3 42 min 8.3 ±0.5 5.3 ±0.4 Tair 43 mean 12.7 ±0.6 10.0 ±0.6 44 max 19.7 ±0.7 17.3 ±0.8 min 7.04 ±0.5 5.2 ±0.6 45</p><p>3 3 46S2</p><p>47</p><p>Date-of- Tissue type measurement Pseudotsuga menziesii Abies lasiocarpa 2,450 (m) 3,000 (m) 2,450 (m) 3,000 (m) Gross photosynthesis -2 -1 (μmol CO2 m d ) 7/11/2006 365.67±57.7 269.58±97.3 121.12±23.1 98.37±22.5 8/03/2006 128.42±19.7 216.7±46.9 141.07±29.4 157.02±34.3 8/19/2006 187.25±26.6 206.4±23.4 246.31±30.4 251.4152.6 9/10/2006 174.21±39.27 164.63±48.2 114.17±36.7 139.59±26.7 Respiration -2 -1 (μmol CO2 m d ) 7/11/2006 122.60±24.6 60.65±14.1 38.84±8.9 33.36±4.5 8/03/2006 41.84±5.1 48.14±6.5 55.41±9.4 37.60±6.2 8/19/2006 76.90±21.9 84.61±9.2 129.55±11.2 104.15±21.6 9/10/2006 85.08±34.4 44.92±10.8 62.25±23.5 33.84±4.6 Whole-plant mass (mg) 7/11/2006 20.1±4.0 15.0±1.6 17.0±0.7 13.6±0.6 8/03/2006 33.4±2.2 28.8±1.1 38.7±2.4 34.9±2.3 8/19/2006 36.4±1.6 30.8±4.4 55.2±4.5 39.4±4.2 9/10/2006 47.1±6.8 45.9±3.6 48.4±5.7 56.9±7.5 Needle mass (mg) 7/11/2006 10.4±2.5 7.5±0.9 9.2±0.6 6.9±0.2 8/03/2006 16.4±0.8 13.3±0.5 22.9±1.9 20.1±1.6 8/19/2006 16.8±1.4 16.5±2.7 34.7±3.1 23.5±2.8 9/10/2006 17.6±2.9 17.8±1.0 24.9±3.6 30.2±4.4 Root area (cm2) 7/11/2006 1.46±0.19 1.15±0.04 1.13±0.05 0.86±0.08 8/03/2006 2.17±0.21 2.20±0.22 2.09±0.23 1.79±0.14 8/19/2006 1.40±0.05 0.86±0.08 1.75±0.40 1.18 9/10/2006 2.79±0.51 2.69±0.47 2.77±0.87 2.14±0.24 Root mass (mg) 7/11/2006 9.7±1.6 7.6±0.7 7.8±0.3 6.6±0.4 8/03/2006 17.0±1.7 15.6±0.9 15.8±1.3 14.8±1.1 8/19/2006 19.6±1.0 14.3±2.1 20.5±2.2 16.9±1.4 9/10/2006 29.5±4.1 28.1±3.2 23.5±3.7 26.6±3.1 Specific leaf area (cm2/mg) 7/11/2006 0.15±0.01 0.15±0.006 0.14±0.009 0.14±0.01 8/03/2006 0.11±0.004 0.11±0.005 0.10±0.003 0.10±0.004 8/19/2006 0.10±0.008 0.08±0.001 0.09±0.009 0.08±0.004 9/10/2006 0.09±0.004 0.08±0.004 0.08±0.002 0.07±0.003 NSC (% dry mass) Whole-plant 7/11/2006 6.6±1.1 10.6±0.8 2.4±0.1 2.2±0.1 8/03/2006 11.2±1.0 12.0±0.4 9.8±1.0 9.5±0.8 8/19/2006 6.0±0.6 7.0±0.5 7.7±0.9 6.6±0.3 9/10/2006 9.1±0.6 9.3±0.9 7.8±0.6 10.1±0.6 Needle 7/11/2006 8.5±1.5 15.6±1.3 2.7±0.2 2.6±0.3 8/03/2006 16.1±1.4 18.5±0.6 13.3±1.4 13.2±1.1 8/19/2006 8.8±1.7 9.5±0.5 11.2±0.9 10.6±0.8 9/10/2006 10.8±0.5 11.8±1.2 9.6±0.7 12.5±0.6 Non-needle 7/11/2006 4.5±0.9 5.6±0.6 2.2±0.2 1.8±0.1 8/03/2006 6.3±0.9 6.4±0.5 4.3±0.3 4.3±0.3 8/19/2006 3.9±1.6 3.7±0.9 1.5±0.6 1.9±1.0 9/10/2006 8.1±0.7 7.4±1.2 5.8±0.5 7.4±0.9</p><p>4 4 Starch (% dry mass) Whole-plant 7/11/2006 3.4±0.7 6.4±0.7 1.6±0.1 1.3±0.1 8/03/2006 5.9±0.7 7.5±0.4 4.9±0.7 4.3±0.7 8/19/2006 1.2±0.4 1.7±0.5 1.8±0.6 1.9±0.3 9/10/2006 3.4±0.3 4.1±0.4 2.4±0.2 4.0±0.6 Non-needle 7/11/2006 1.8±0.2 2.2±0.4 1.1±0.1 0.9±0.2 8/03/2006 2.2±0.5 2.8±0.2 1.4±0.2 1.5±0.1 8/19/2006 0.7±0.3 1.4±0.2 0.3±0.2 1.0±0.3 9/10/2006 3.9±0.4 3.9±0.7 2.2±0.1 4.0±0.9 Simple sugars (% dry mass) Whole-plant 7/11/2006 3.2±0.7 4.2±0.2 0.8±0.1 0.9±0.1 8/03/2006 5.3±0.3 4.5±0.2 4.9±0.4 5.2±0.2 8/19/2006 4.8±0.3 5.2±0.5 5.9±0.4 4.7±0.4 9/10/2006 5.7±0.3 5.1±0.5 5.4±0.4 6.1±0.3 Needle 7/11/2006 3.5±0.6 5.0±0.4 0.7±0.2 0.8±0.2 8/03/2006 6.5±0.4 5.4±0.3 6.2±0.6 6.9±0.2 8/19/2006 7.0±1.3 7.7±0.8 8.7±0.5 7.7±0.8 9/10/2006 8.1±0.5 7.6±0.8 7.2±0.3 8.6±0.7 Non-needle 7/11/2006 2.8±0.7 3.4±0.4 1.1±0.2 0.9±0.1 8/03/2006 4.2±0.4 3.7±0.3 2.8±0.1 2.9±0.3 8/19/2006 3.3±1.3 2.3±0.7 1.2±0.4 1.0±0.7 9/10/2006 4.2±0.3 3.5±0.5 3.6±0.6 3.4±0.2 48</p><p>49</p><p>5 5 50S4</p><p>0.80</p><p>0.75</p><p>0.70 m F / v</p><p>F 0.65</p><p>0.60</p><p>0.55</p><p>51 18 Aug 2006 10 Sept 2006 14 Sept 2005</p><p>52</p><p>6 6</p>