1 00:00:06,390 --> 00:00:09,003 - This next talk is from Kelly French, 2 00:00:09,850 --> 00:00:11,480 with the University of Maine, 3 00:00:11,480 --> 00:00:14,200 School of Forest Resources. 4 00:00:14,200 --> 00:00:16,240 Presenting Spruce: DRIED, 5 00:00:16,240 --> 00:00:19,313 Density Reduction and Imposed Extreme Drought. 6 00:00:20,860 --> 00:00:23,190 - I am a second year masters student 7 00:00:23,190 --> 00:00:25,130 at the University of Maine. 8 00:00:25,130 --> 00:00:28,610 So this is part of my thesis research 9 00:00:28,610 --> 00:00:31,870 and I'm just gonna present some of the preliminary results 10 00:00:31,870 --> 00:00:35,040 we have from this part of my study. 11 00:00:35,040 --> 00:00:37,270 I can't get through everything today unfortunately, 12 00:00:37,270 --> 00:00:38,240 'cause there's a lot of data 13 00:00:38,240 --> 00:00:41,090 but I'm just gonna share some of the highlights with you. 14 00:00:42,810 --> 00:00:46,530 I would like to mention all of the other study authors 15 00:00:46,530 --> 00:00:47,660 that have been involved in this. 16 00:00:47,660 --> 00:00:50,160 It was a great collaborative effort 17 00:00:50,160 --> 00:00:54,390 between my team here at the University of Maine, 18 00:00:54,390 --> 00:00:56,680 including my advisor Dr. Jay Waston 19 00:00:56,680 --> 00:00:59,870 and Dr. Fraver and Dr. Kenefic on my committee, 20 00:00:59,870 --> 00:01:03,483 and Heidi's lab at the University of New Hampshire. 21 00:01:05,190 --> 00:01:07,800 So as the title of my study indicates, 22 00:01:07,800 --> 00:01:09,360 this is kind of a two-part study 23 00:01:09,360 --> 00:01:10,850 looking at thinning and drought. 24 00:01:10,850 --> 00:01:13,940 So just a little bit of brief background. 25 00:01:13,940 --> 00:01:16,490 We do know that forest density reduction 26 00:01:16,490 --> 00:01:19,410 through thinning is beneficial for residual trees 27 00:01:19,410 --> 00:01:21,410 because of the decreased competition 28 00:01:21,410 --> 00:01:23,850 for resources like growing space, 29 00:01:23,850 --> 00:01:26,720 light, water, and nutrients. 30 00:01:26,720 --> 00:01:29,290 However, something that's not thought about 31 00:01:29,290 --> 00:01:31,130 necessarily as commonly, 32 00:01:31,130 --> 00:01:35,870 is the impact of this increased exposure and temperature 33 00:01:35,870 --> 00:01:37,970 that can come from heavily thinning these stands 34 00:01:37,970 --> 00:01:40,260 and really opening up the canopy 35 00:01:40,260 --> 00:01:42,470 for all this increased light. 36 00:01:42,470 --> 00:01:43,830 This can potentially lead to 37 00:01:43,830 --> 00:01:46,440 what are called thinning shocks. 38 00:01:46,440 --> 00:01:49,220 A lot of this is due to this abrupt transition 39 00:01:49,220 --> 00:01:52,130 from shade to light in these non adapted needles. 40 00:01:52,130 --> 00:01:54,950 And some things that have been quantified thus far 41 00:01:54,950 --> 00:01:58,460 have been decreased growth, 42 00:01:58,460 --> 00:02:01,223 reduced photosynthesis, leaf mortality, 43 00:02:02,530 --> 00:02:04,460 all in these non adopted needles. 44 00:02:04,460 --> 00:02:07,530 And the reason that I am interested 45 00:02:07,530 --> 00:02:09,500 at looking at these effects, 46 00:02:09,500 --> 00:02:12,020 is due to the fact that they may be worse 47 00:02:12,020 --> 00:02:14,173 in projected future climates. 48 00:02:15,060 --> 00:02:17,230 Which kind of ties into the second part of my study 49 00:02:17,230 --> 00:02:18,630 which is looking at drought. 50 00:02:19,710 --> 00:02:22,150 As we have already talked about earlier 51 00:02:22,150 --> 00:02:25,950 in previous presentations that climate change 52 00:02:25,950 --> 00:02:28,180 is expected to drive a lot of differences, 53 00:02:28,180 --> 00:02:29,390 increased temperatures, 54 00:02:29,390 --> 00:02:31,120 increased vapor pressure deficit, 55 00:02:31,120 --> 00:02:36,120 which is a quantification of how dry the air actually is. 56 00:02:36,610 --> 00:02:38,290 So sometimes it's termed like 57 00:02:38,290 --> 00:02:40,180 atmospheric drought conditions. 58 00:02:40,180 --> 00:02:42,000 And then also drought frequency, 59 00:02:42,000 --> 00:02:44,180 as we talked about annual precipitation 60 00:02:44,180 --> 00:02:45,256 is projected to increase 61 00:02:45,256 --> 00:02:48,430 but so our risks of seasonal droughts 62 00:02:48,430 --> 00:02:51,320 particularly in the summer and the fall. 63 00:02:51,320 --> 00:02:54,940 So, as you can see from this figure above 64 00:02:54,940 --> 00:02:58,310 spruce-fir forest types and other mesic forest types 65 00:02:58,310 --> 00:03:03,170 in the Northeast are potentially going to have 66 00:03:03,170 --> 00:03:05,950 large impacts just even due to small changes 67 00:03:05,950 --> 00:03:07,910 in these different climactic variables 68 00:03:07,910 --> 00:03:11,163 because they're not adapted to these changes in climate. 69 00:03:12,470 --> 00:03:13,750 And my study species, 70 00:03:13,750 --> 00:03:15,370 which is red spruce, 71 00:03:15,370 --> 00:03:19,810 has been shown through growth climate correlations, 72 00:03:19,810 --> 00:03:23,260 to decline in growth with increased summer heat, 73 00:03:23,260 --> 00:03:25,310 and also has growth declines 74 00:03:25,310 --> 00:03:27,620 with decreased spring and fall precipitation. 75 00:03:27,620 --> 00:03:31,380 Showing that it is a particularly climate sensitive species. 76 00:03:31,380 --> 00:03:35,050 So thinking about thinning and thinking about drought, 77 00:03:35,050 --> 00:03:37,380 kind of drives the overall goal of my study. 78 00:03:37,380 --> 00:03:40,610 Which was to improve our understanding of how thinning 79 00:03:40,610 --> 00:03:43,750 and extreme drought influenced the physiology of red spruce 80 00:03:43,750 --> 00:03:45,780 and then trying to interpret these patterns 81 00:03:45,780 --> 00:03:48,600 to help better inform future management 82 00:03:48,600 --> 00:03:50,360 of this species with climate change. 83 00:03:50,360 --> 00:03:52,490 So the first objective 84 00:03:52,490 --> 00:03:56,190 is investigating the immediate impacts of thinning 85 00:03:56,190 --> 00:03:57,830 on mature red spruce, 86 00:03:57,830 --> 00:04:00,850 trying to quantify any evidence of thinning shock. 87 00:04:00,850 --> 00:04:02,920 And then the second objective is it looking at 88 00:04:02,920 --> 00:04:06,340 how these red spruce respond physiologically over time 89 00:04:06,340 --> 00:04:09,610 to this experimentally imposed extreme drought, 90 00:04:09,610 --> 00:04:12,090 I'll talk a little bit more about. 91 00:04:12,090 --> 00:04:15,850 So we had a study sample size 92 00:04:15,850 --> 00:04:18,130 of eight focal red spruce trees. 93 00:04:18,130 --> 00:04:20,820 They were all crown-suppressed on the same size, 94 00:04:20,820 --> 00:04:24,040 16 to 26 centimeters in DBH. 95 00:04:24,040 --> 00:04:27,700 And we created this factorial design of two by two 96 00:04:27,700 --> 00:04:32,160 for our thinning treatment and our drought treatment. 97 00:04:32,160 --> 00:04:33,330 So for our thin treatment, 98 00:04:33,330 --> 00:04:37,020 we had a full kind of crop tree release of the canopy 99 00:04:37,020 --> 00:04:37,990 or up the crown. 100 00:04:37,990 --> 00:04:40,220 Everything was released on all four sides. 101 00:04:40,220 --> 00:04:42,690 That's why we wanted to look at crown suppressed trees 102 00:04:42,690 --> 00:04:44,700 because we wanted to really capture 103 00:04:44,700 --> 00:04:48,370 as much effect as we could of thinning shock potentially. 104 00:04:48,370 --> 00:04:51,290 So we wanted canopies that had previously been shaded 105 00:04:51,290 --> 00:04:53,050 to fully open them up. 106 00:04:53,050 --> 00:04:55,310 And for our drought treatment, 107 00:04:55,310 --> 00:04:58,530 we did this treatment that is pretty novel 108 00:04:58,530 --> 00:05:01,730 where we actually severed the sapwood. 109 00:05:01,730 --> 00:05:03,520 So effectively cutting off the xylem 110 00:05:03,520 --> 00:05:05,780 which is transporting water from the roots 111 00:05:05,780 --> 00:05:07,590 up into the rest of the tree. 112 00:05:07,590 --> 00:05:10,000 So if we severed all of the sapwood, 113 00:05:10,000 --> 00:05:13,010 that would effectively mimic the effects of 114 00:05:13,010 --> 00:05:16,040 if there was no water in the soil to begin with. 115 00:05:16,040 --> 00:05:17,600 And our control for this treatment 116 00:05:17,600 --> 00:05:20,040 was a phloem girdled control 117 00:05:20,040 --> 00:05:22,840 because we expected that phloem girdling 118 00:05:22,840 --> 00:05:25,330 might have some sort of physiological effect as well. 119 00:05:25,330 --> 00:05:27,360 So we wanted to account for that. 120 00:05:27,360 --> 00:05:30,700 And there was a lot of different measurements 121 00:05:30,700 --> 00:05:32,300 that took place throughout the growing season. 122 00:05:32,300 --> 00:05:35,300 This is a preliminary experiment. 123 00:05:35,300 --> 00:05:37,540 So our sample size wasn't as large 124 00:05:37,540 --> 00:05:39,760 as hopefully future studies will be. 125 00:05:39,760 --> 00:05:41,900 But one of the limiting factors also 126 00:05:41,900 --> 00:05:44,630 was installation of these sap flow sensors 127 00:05:44,630 --> 00:05:47,230 which are what we use to monitor a tree water use 128 00:05:47,230 --> 00:05:51,193 alongside all of these other physiological responses. 129 00:05:52,420 --> 00:05:54,890 So let's talk first about some of the impacts 130 00:05:54,890 --> 00:05:56,363 of thinning that we saw. 131 00:05:57,710 --> 00:05:58,950 The first thing was that 132 00:05:58,950 --> 00:06:01,130 we did notice thinning did drive 133 00:06:01,130 --> 00:06:06,130 this increase in temperature and vapor pressure deficit. 134 00:06:07,100 --> 00:06:09,530 So we have five days pre-thinning 135 00:06:09,530 --> 00:06:11,640 and five days posts in these graphs. 136 00:06:11,640 --> 00:06:14,840 And the red line indicates when we conducted the thinning. 137 00:06:14,840 --> 00:06:17,060 And for the thinned trees, 138 00:06:17,060 --> 00:06:18,380 we saw an increase in temperature 139 00:06:18,380 --> 00:06:20,720 of about 2 1/2 degrees Celsius 140 00:06:20,720 --> 00:06:23,440 and a vapor pressure a deficit increase 141 00:06:23,440 --> 00:06:25,520 of about 0.64 kilopascals. 142 00:06:25,520 --> 00:06:29,060 That indicates that air was drier than 143 00:06:29,060 --> 00:06:30,483 for the non thinned trees. 144 00:06:31,370 --> 00:06:32,570 So, (keyboard clicking). 145 00:06:37,350 --> 00:06:38,183 There we go. 146 00:06:39,660 --> 00:06:41,620 So these changes in microclimate 147 00:06:41,620 --> 00:06:45,777 did end up driving some evidence of thinning shock. 148 00:06:45,777 --> 00:06:47,710 And the first way that we saw this 149 00:06:47,710 --> 00:06:51,933 was through reduced midday water potentials. 150 00:06:52,780 --> 00:06:54,080 So water potentials, 151 00:06:54,080 --> 00:06:56,210 for those who aren't really familiar with that term, 152 00:06:56,210 --> 00:06:59,070 that's basically a quantification of the pressure 153 00:06:59,070 --> 00:07:01,493 that builds up within a plant 154 00:07:01,493 --> 00:07:05,570 in order to drive the flow of water up the xylem. 155 00:07:05,570 --> 00:07:09,740 So a stressed plant that doesn't have a lot of water 156 00:07:09,740 --> 00:07:12,050 is gonna continuously increase that pressure 157 00:07:12,050 --> 00:07:13,963 to really try to drive the water up. 158 00:07:15,690 --> 00:07:17,630 So for our thin trees we did see that 159 00:07:17,630 --> 00:07:20,950 they were significantly decreased in water potential. 160 00:07:20,950 --> 00:07:22,070 They weren't really stressed 161 00:07:22,070 --> 00:07:24,670 on this cloudy and cool day as to be expected. 162 00:07:24,670 --> 00:07:26,860 But on a sunny and hot day, 163 00:07:26,860 --> 00:07:29,130 it's important to consider their turgor loss point 164 00:07:29,130 --> 00:07:31,740 which is where these needles lose turgor 165 00:07:31,740 --> 00:07:33,563 and may potentially start to wilt. 166 00:07:34,810 --> 00:07:36,340 And the fact that the thin trees 167 00:07:36,340 --> 00:07:39,070 were well below this range for turgor loss point. 168 00:07:39,070 --> 00:07:40,960 Indicating that if they persist 169 00:07:40,960 --> 00:07:42,790 in the state at this level, 170 00:07:42,790 --> 00:07:45,040 it's going to have potentially harmful effects 171 00:07:45,040 --> 00:07:46,650 on the leaves. 172 00:07:46,650 --> 00:07:49,240 And the second evidence of thinning shock that we saw 173 00:07:49,240 --> 00:07:52,100 was this decreased photosynthetic efficiency 174 00:07:52,100 --> 00:07:55,070 of the photosystems within the chloroplasts. 175 00:07:55,070 --> 00:07:58,030 So a healthy level for this is about 0.83. 176 00:07:58,030 --> 00:08:01,080 This is kind of a a more complicated metric 177 00:08:01,080 --> 00:08:03,987 using a little FluorPen that we used, 178 00:08:03,987 --> 00:08:06,900 but we did see not only immediate effects here 179 00:08:06,900 --> 00:08:09,620 in immediate decrease in photosynthetic efficiency 180 00:08:09,620 --> 00:08:11,690 very shortly after the thinning, 181 00:08:11,690 --> 00:08:13,960 but this persisted throughout the rest of the growing season 182 00:08:13,960 --> 00:08:15,560 until the end of the experiment. 183 00:08:16,470 --> 00:08:19,060 So that was quite surprising but very interesting 184 00:08:19,060 --> 00:08:21,963 to see that that effect lasted so long. 185 00:08:23,270 --> 00:08:27,340 Moving on to the effects of the imposed drought. 186 00:08:27,340 --> 00:08:30,840 We imposed this drought two weeks after we did the thinning. 187 00:08:30,840 --> 00:08:33,100 So went in with our circular saw 188 00:08:33,100 --> 00:08:35,330 and cut the sapwood at that point. 189 00:08:35,330 --> 00:08:37,420 It's important to know that we did not see 190 00:08:37,420 --> 00:08:40,060 an interactive effect of thinning and drought. 191 00:08:40,060 --> 00:08:41,410 So moving forward, 192 00:08:41,410 --> 00:08:44,380 I'm just gonna be referring to these trees 193 00:08:44,380 --> 00:08:45,813 by their drought treatment. 194 00:08:47,470 --> 00:08:49,170 So the first thing that we saw was that 195 00:08:49,170 --> 00:08:53,760 severing the sapwood did cause reductions in sap flow, 196 00:08:53,760 --> 00:08:56,740 but the only 100% reduction in sap flow 197 00:08:56,740 --> 00:08:59,550 actually imposed this extreme drought we were looking for. 198 00:08:59,550 --> 00:09:01,840 I'll get into some of the evidence of that 199 00:09:01,840 --> 00:09:03,330 in the next few slides. 200 00:09:03,330 --> 00:09:05,960 This is a graph showing five days pre-treatment 201 00:09:05,960 --> 00:09:10,890 versus post-treatment total daily water use changes, 202 00:09:10,890 --> 00:09:12,270 the percent change. 203 00:09:12,270 --> 00:09:15,220 So for two of our trees that we severed sapwood on, 204 00:09:15,220 --> 00:09:18,130 we were successful at severing a 100% of the sapwood 205 00:09:18,130 --> 00:09:21,180 which caused a 100% reduction sap flow. 206 00:09:21,180 --> 00:09:23,170 For two of the trees, 207 00:09:23,170 --> 00:09:25,330 we didn't successfully sever all the sap flows. 208 00:09:25,330 --> 00:09:27,680 So they didn't experience 209 00:09:27,680 --> 00:09:29,740 all of their water use being cut off. 210 00:09:29,740 --> 00:09:31,100 And then the phloem girdled, 211 00:09:31,100 --> 00:09:33,660 as we expected didn't have significant changes. 212 00:09:33,660 --> 00:09:37,540 So this was really interesting to us to see, 213 00:09:37,540 --> 00:09:39,830 that partially severing the sapwood 214 00:09:39,830 --> 00:09:42,280 which did cause these large declines, 215 00:09:42,280 --> 00:09:45,070 actually never caused water stress in these trees 216 00:09:45,070 --> 00:09:46,640 throughout the duration of the experiment 217 00:09:46,640 --> 00:09:49,640 which was really quite shocking to us. 218 00:09:49,640 --> 00:09:53,090 We quantified the sapwood by taking increment cores 219 00:09:53,090 --> 00:09:56,200 and measuring the area that was wet. 220 00:09:56,200 --> 00:09:59,570 We also quantified this with relative water content analysis 221 00:09:59,570 --> 00:10:03,320 and using a wood moisture meter. 222 00:10:03,320 --> 00:10:06,870 And basically I have this little schematic of a cookie. 223 00:10:06,870 --> 00:10:08,190 So if we went around, 224 00:10:08,190 --> 00:10:11,054 this is our circular saw and cut the sapwood 225 00:10:11,054 --> 00:10:13,300 cause we wanted to cut all the way through 226 00:10:13,300 --> 00:10:15,070 potentially into the heartwood. 227 00:10:15,070 --> 00:10:18,410 Some maybe thicker bark in certain areas 228 00:10:18,410 --> 00:10:21,230 or just the saw like not being able to penetrate 229 00:10:21,230 --> 00:10:23,720 all the way through caused these little inclusions 230 00:10:23,720 --> 00:10:26,820 of residual sapwood remaining into these trees 231 00:10:26,820 --> 00:10:28,640 which after we harvested the trees, 232 00:10:28,640 --> 00:10:32,450 we quantified at about 2 to 5%. 233 00:10:32,450 --> 00:10:37,060 Which is shockingly low for still being able to transport 234 00:10:37,060 --> 00:10:39,880 about like 30% of previous sap flow volumes. 235 00:10:39,880 --> 00:10:41,770 But this seemed to be enough 236 00:10:41,770 --> 00:10:44,030 for the duration of this study at least 237 00:10:44,030 --> 00:10:46,300 to prevent these trees from getting water stress. 238 00:10:46,300 --> 00:10:48,950 They never experienced water potential declines, 239 00:10:48,950 --> 00:10:51,440 trunk rot, relative water content declines 240 00:10:51,440 --> 00:10:53,870 and there was no impact on their stomatal conductance 241 00:10:53,870 --> 00:10:55,920 indicating they weren't closing their stomata at all. 242 00:10:55,920 --> 00:10:58,600 So this was one of the more shocking findings 243 00:10:58,600 --> 00:11:00,363 of this study but very interesting. 244 00:11:02,070 --> 00:11:03,330 For the trees that 245 00:11:03,330 --> 00:11:05,690 we did successfully sever all the sapwood on, 246 00:11:05,690 --> 00:11:08,130 and I'm gonna refer to them moving forward as droughted 247 00:11:08,130 --> 00:11:10,850 because they are experiencing the drought. 248 00:11:10,850 --> 00:11:13,520 Another really really surprising thing was that 249 00:11:13,520 --> 00:11:16,480 these droughted trees lasted at least 12 weeks 250 00:11:16,480 --> 00:11:19,470 without showing evidence of water stress as well. 251 00:11:19,470 --> 00:11:22,940 So I have a graph here showing midday leaf water potential, 252 00:11:22,940 --> 00:11:24,580 the droughted trees are in red. 253 00:11:24,580 --> 00:11:27,380 So you do see that they are starting to decline this week 254 00:11:27,380 --> 00:11:28,960 since the drought was initiated. 255 00:11:28,960 --> 00:11:29,870 They are declining, 256 00:11:29,870 --> 00:11:32,680 but they don't reach these kinds of detrimental levels 257 00:11:32,680 --> 00:11:34,850 until around the end of September. 258 00:11:34,850 --> 00:11:36,850 And they don't reach their P50 value, 259 00:11:36,850 --> 00:11:41,850 which is the the water potential at which 50% of the xylem 260 00:11:43,540 --> 00:11:46,390 has lost embolism and can't transport water. 261 00:11:46,390 --> 00:11:47,590 They didn't reach that level 262 00:11:47,590 --> 00:11:50,190 until 15 weeks after we initiated the drought. 263 00:11:50,190 --> 00:11:53,260 So this happened over a much longer period of time 264 00:11:53,260 --> 00:11:55,610 than we were expecting this to happen, 265 00:11:55,610 --> 00:11:57,293 kind of within a month or so. 266 00:11:58,530 --> 00:12:01,380 So we ended up looking also at stomatal conductance 267 00:12:01,380 --> 00:12:02,580 to try and see, you know, 268 00:12:02,580 --> 00:12:05,160 what is actually going on with the mechanisms. 269 00:12:05,160 --> 00:12:06,490 And we found these droughted trees 270 00:12:06,490 --> 00:12:09,120 did have greatly reduced stomatal conductance. 271 00:12:09,120 --> 00:12:12,670 So this is indicating their stomates were tightly closed. 272 00:12:12,670 --> 00:12:15,470 So when the stomata are open, 273 00:12:15,470 --> 00:12:16,940 active photosynthesis is happening, 274 00:12:16,940 --> 00:12:18,140 transpiration is happening. 275 00:12:18,140 --> 00:12:20,790 So water is being lost through these open stomata 276 00:12:20,790 --> 00:12:24,460 and our droughted trees closed up their stomata 277 00:12:24,460 --> 00:12:26,300 to prevent water loss. 278 00:12:26,300 --> 00:12:28,310 But as a result their photosynthesis 279 00:12:28,310 --> 00:12:30,413 is gonna be really greatly reduced. 280 00:12:31,950 --> 00:12:35,000 Another evidence of the drought that we did see 281 00:12:35,000 --> 00:12:39,360 was declines in relative water content in the trunk wood. 282 00:12:39,360 --> 00:12:42,100 So here is a graph of all three of our treatments 283 00:12:42,100 --> 00:12:44,320 showing there is some seasonal variation 284 00:12:44,320 --> 00:12:46,590 in relative water content that always occurs 285 00:12:46,590 --> 00:12:47,870 and that's to be expected. 286 00:12:47,870 --> 00:12:49,980 However, again, at around week 12, 287 00:12:49,980 --> 00:12:51,280 we see that the droughted trees 288 00:12:51,280 --> 00:12:53,970 are not really able to recover potentially 289 00:12:53,970 --> 00:12:57,210 due to so much of their xylem being filled with embolisms 290 00:12:57,210 --> 00:12:59,620 and being unable to refill with water 291 00:12:59,620 --> 00:13:01,550 which would cause their relative water content 292 00:13:01,550 --> 00:13:02,543 to go up again. 293 00:13:04,680 --> 00:13:05,950 It's important to note that 294 00:13:05,950 --> 00:13:08,710 while the droughted trees lasted so long 295 00:13:08,710 --> 00:13:11,320 without really true signs of stress, 296 00:13:11,320 --> 00:13:13,080 they did eventually die. 297 00:13:13,080 --> 00:13:15,050 And this is a graph showing water potentials 298 00:13:15,050 --> 00:13:17,110 of branch wood and crown-wood 299 00:13:18,010 --> 00:13:21,590 from the final harvest date which was in November, 300 00:13:21,590 --> 00:13:23,090 showing that by the experiments, 301 00:13:23,090 --> 00:13:25,420 and we did reach these catastrophic levels, 302 00:13:25,420 --> 00:13:28,830 that the tree would not be able to recover from. 303 00:13:28,830 --> 00:13:30,180 Whereas the other two treatments, 304 00:13:30,180 --> 00:13:33,330 the partially severed and the phloem girdled 305 00:13:33,330 --> 00:13:35,553 they never reached these low levels. 306 00:13:37,480 --> 00:13:39,240 So our conclusions, 307 00:13:39,240 --> 00:13:41,850 going back again to thinning shock. 308 00:13:41,850 --> 00:13:44,020 Due to increase temperature and vapor pressure deficit, 309 00:13:44,020 --> 00:13:45,930 we did see evidence of thinning shock 310 00:13:45,930 --> 00:13:47,750 which was lowered midday water potentials 311 00:13:47,750 --> 00:13:51,123 and this significantly decreased photosynthetic efficiency. 312 00:13:52,820 --> 00:13:55,870 The as little as 2% of sapwood left intact 313 00:13:55,870 --> 00:13:57,850 seems sufficient to transport 314 00:13:57,850 --> 00:14:00,490 you know, 30% of prior sap flow volumes 315 00:14:00,490 --> 00:14:01,950 and that prevented water stress 316 00:14:01,950 --> 00:14:04,340 throughout the duration of the study. 317 00:14:04,340 --> 00:14:06,950 And then our last big finding was that 318 00:14:06,950 --> 00:14:08,810 there was no clear signs of water stress 319 00:14:08,810 --> 00:14:11,650 in the needles or the trunk for about 12 weeks 320 00:14:11,650 --> 00:14:16,240 even in these trees that had 100% reductions in sap flow. 321 00:14:16,240 --> 00:14:19,970 So this has pretty big implications for future research 322 00:14:19,970 --> 00:14:21,640 and just the future in general, 323 00:14:21,640 --> 00:14:25,140 what to think about on heavily thinning stand 324 00:14:25,140 --> 00:14:28,500 of spruce-fir forest and future productive climates 325 00:14:28,500 --> 00:14:30,390 could further increase stand temperature 326 00:14:30,390 --> 00:14:33,780 and vapor pressure deficit above of where it already is 327 00:14:33,780 --> 00:14:35,040 due to chronic change. 328 00:14:35,040 --> 00:14:36,320 So more studies needed 329 00:14:36,320 --> 00:14:38,870 on how this is gonna affect tree physiology, 330 00:14:38,870 --> 00:14:40,350 the water relations, 331 00:14:40,350 --> 00:14:42,830 and just treat growth as a whole, 332 00:14:42,830 --> 00:14:44,770 by looking at, you know, increment cores. 333 00:14:44,770 --> 00:14:47,760 That's something that a longer term study doing this over, 334 00:14:47,760 --> 00:14:50,320 you know, a few years would be able to look at 335 00:14:50,320 --> 00:14:54,570 the actual effect on the growth itself. 336 00:14:54,570 --> 00:14:55,470 And then secondly, 337 00:14:55,470 --> 00:14:58,620 for the drought red spruce did show 338 00:14:58,620 --> 00:15:01,360 very strong signs of drought resistance, 339 00:15:01,360 --> 00:15:03,070 but it's important to consider that 340 00:15:03,070 --> 00:15:04,580 this is due to this trade-off 341 00:15:04,580 --> 00:15:07,640 between photosynthesis and water conservation. 342 00:15:07,640 --> 00:15:11,840 So this is really major opportunity cost for for carbon gain 343 00:15:11,840 --> 00:15:14,930 due to the fact they're closing their stomata. 344 00:15:14,930 --> 00:15:16,750 So it's still important to consider that 345 00:15:16,750 --> 00:15:19,040 the species while it may be resistant, 346 00:15:19,040 --> 00:15:20,310 is very sensitive. 347 00:15:20,310 --> 00:15:21,890 You know, they're closing their stomata 348 00:15:21,890 --> 00:15:24,200 and that's preventing them from photosynthesizing 349 00:15:24,200 --> 00:15:26,870 which is their means of survival. 350 00:15:26,870 --> 00:15:28,910 So for a natural drought, 351 00:15:28,910 --> 00:15:31,840 you know that they might be able to overcome, 352 00:15:31,840 --> 00:15:34,510 surviving a natural drought is probably going to show 353 00:15:34,510 --> 00:15:37,560 you know, a greatly reduced growth and like a CFX. 354 00:15:37,560 --> 00:15:42,023 So thinking about this more long-term is important. 355 00:15:43,360 --> 00:15:45,640 I just really quickly like to acknowledge everybody 356 00:15:45,640 --> 00:15:46,840 that was involved in this study, 357 00:15:46,840 --> 00:15:50,240 my funders, all my co-authors, 358 00:15:50,240 --> 00:15:53,780 the university forest staff and my lab mates. 359 00:15:53,780 --> 00:15:57,320 Without them I really could not have done all this work. 360 00:15:57,320 --> 00:15:58,153 Thank you. 361 00:15:58,153 --> 00:16:00,220 And I'll take any questions that you might have. 362 00:16:02,800 --> 00:16:06,300 - Tony McCullough, "should managers of spruce-fir forest 363 00:16:06,300 --> 00:16:08,680 rethink their approach to timber management 364 00:16:08,680 --> 00:16:10,537 in light of your findings?" 365 00:16:11,560 --> 00:16:16,240 - So I think that it's really important to keep in mind 366 00:16:16,240 --> 00:16:19,970 like how important and essential thinning is, 367 00:16:19,970 --> 00:16:22,000 you know, as a tool for forest managers. 368 00:16:22,000 --> 00:16:25,060 I think that the benefits that come from thinning 369 00:16:25,060 --> 00:16:28,310 due to reduced competition, 370 00:16:28,310 --> 00:16:30,930 are more than likely going to outweigh 371 00:16:30,930 --> 00:16:35,660 the negative effects of thinning shock in the future. 372 00:16:35,660 --> 00:16:38,550 But I think that it kind of has more of an impact 373 00:16:38,550 --> 00:16:43,550 on the actual mechanism of thinning that we might use. 374 00:16:43,670 --> 00:16:45,840 You know, I don't know, 375 00:16:45,840 --> 00:16:47,540 as I'm not a silviculturist, 376 00:16:47,540 --> 00:16:48,820 I'm not sure how often 377 00:16:48,820 --> 00:16:52,763 like a full crop tree release of individual red spruce is. 378 00:16:53,730 --> 00:16:54,930 But maybe, you know, 379 00:16:54,930 --> 00:16:58,560 considering using low light thinnings 380 00:16:58,560 --> 00:17:01,800 versus a very heavy crown thinning. 381 00:17:01,800 --> 00:17:03,960 Just thinking more along the terms of how can we 382 00:17:03,960 --> 00:17:07,540 still get all of the beneficial effects of thinning 383 00:17:07,540 --> 00:17:12,330 without exacerbating these potential thinning shock effects 384 00:17:12,330 --> 00:17:13,283 in the future. 385 00:17:19,090 --> 00:17:23,057 - Nancy Patch says "low thinning would have less stress." 386 00:17:24,600 --> 00:17:25,543 - Yeah, exactly. 387 00:17:30,440 --> 00:17:32,443 - You have any other questions? 388 00:17:40,340 --> 00:17:42,990 I think they take a minute to come in on my computer too. 389 00:17:42,990 --> 00:17:44,640 So I'm just giving them a second. 390 00:17:51,440 --> 00:17:54,570 - I know that was a lot of graphs and a lot of data. 391 00:17:54,570 --> 00:17:56,920 If anybody also thinks of questions later 392 00:17:56,920 --> 00:17:58,840 and wants to email me, 393 00:17:58,840 --> 00:18:00,913 that would be great as well. 394 00:18:05,870 --> 00:18:07,830 - Can you put your email in the chat there? 395 00:18:07,830 --> 00:18:09,830 - I'll do that, yes. 396 00:18:09,830 --> 00:18:12,513 - I think it might be accessible other places too. 397 00:18:13,392 --> 00:18:16,392 (keyboard clicking) 398 00:18:22,530 --> 00:18:23,740 Okay, great. 399 00:18:23,740 --> 00:18:25,460 I think we'll close it up then. 400 00:18:25,460 --> 00:18:27,600 And people can email for more questions. 401 00:18:27,600 --> 00:18:28,500 Thank you so much. 402 00:18:28,500 --> 00:18:29,333 - Yeah