From the University of Washington and the Department of Pointless NSF Grants, comes this: Shrub growth decreases as winter temperatures fluctuate up
Many have assumed that warmer winters as a result of climate change would increase the growth of trees and shrubs because the growing season would be longer. But shrubs achieve less yearly growth when cold winter temperatures are interrupted by temperatures warm enough to trigger growth.
“When winter temperatures fluctuate between being cold and warm enough for growth, plants deplete their resources trying to photosynthesize and end the winter with fewer reserves than they initially had. In the summer they have to play catch up,” said Melanie Harsch, a University of Washington postdoctoral researcher in biology and applied mathematics. She is lead author of a paper on the subject recently published in PLOS One.
The roots are especially sensitive to temperature fluctuations, Harsch said. Warming winters result in higher root respiration, which uses up carbon reserves as plants make and release oxygen, leading to less carbon available during the regular growing season.
Harsch and her colleagues studied two species of shrubs on Campbell Island, an uninhabited UNESCO World Heritage site in the southwest Pacific Ocean about 375 miles south of New Zealand’s mainland. They studied two large shrubs, Dracophyllum longifolium and Dracophyllum scoparium, which are evergreen broadleaf species that can grow up to about 15 feet tall and live up to 240 years.
Researchers found that while warmer, drier winters helped seedlings get established, it adversely affected growth of older plants.
“For growth to occur you need sufficient precipitation and temperature and nutrients. Growth should only happen during the summer on Campbell Island when temperatures are above 5 degrees Celsius,” Harsch said. Five degrees C is about 40 F. “On Campbell Island most winters are cool and below this 5 degrees Celsius, so the plants are not active. The plants we studied are evergreen and there is little snow cover, so they are sensitive to changes in temperature.”
In this study, researchers cut out discs, called “cookies,” from just above the shrubs’ root collar, and measured the width between each ring to determine growth. They found that plant growth decreased as winter temperatures went up.
“On Campbell Island the snow is ephemeral, so the plants usually are not covered,” Harsch said. “If we’re going to see an effect in changing winter conditions, we’re going to see it at Campbell Island decades before we see it at, say, Mt. Rainier, where there is a lot of snow and winters are colder.”
Harsch said plants in areas like Campbell Island may eventually adjust to warmer winters, but the transition period will be tough as temperatures bounce above and below what plants need to stay dormant, causing the plants to draw down their resources.
“It may eventually be warm enough in the winters so that plants can photosynthesize and grow year round, like they do in the tropics,” she said. “It’s this transition part that plants are not adapted for.”
Harsch plans to do a follow-up study that would measure the microbes and carbon reserves in the soil, and manipulate snow packs to see how it affects establishment and growth.
“How much of this can our tree species withstand?” Harsch said. “Will summer growth eventually compensate for these hard winters, or is this some sort of extra stressor on trees that will be one more nail in the coffin? If you think of all the different factors of increasing vulnerability in climate change, is this really significant? We just don’t know.”
Co-authors are Matt McGlone and Janet Wilmshurst at Landcare Research in New Zealand. Harsch started the work while pursuing her doctorate at Lincoln University in New Zealand and finished the analysis at the UW. The work was supported in part by the National Science Foundation.
# # #
For more information, contact Harsch at harsch.melanie@gmail.com or 253-365-1555.
NSF grant: DEB-1103734.
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Was that it. They studied two shrubs and then came to this conclusion! Unreal.
[rather: Two shrub species? Mod]
And where to find a shrubbery, and what to cut it down with?
– https://www.youtube.com/watch?v=69iB-xy0u4A
“It’s worse than we thought”- The Shrubs
It’s bushes fault.
If I understand this right, warm periods in winter will cause me to prune my shrubbery less often. Sounds good to me.
Typo in the headline “growt”
growt will out
[Fixed. Thank you. Mod]
Is there anyone out there who has ever grown an outdoor plant, who didn’t know that a warm spell during the winter followed by more winter weather would screw up the plant’s growth
Shrubbery? The knights say Ni!
Where is Roger the Shrubber when you need him?
At one time, it was common knowledge (at least in non-academic circles) that young trees and shrubs have to be shielded from sunlight (covered with snow) to prevent them from growing during periods of warmer winter temperatures. It is unlikely that depletion of nutrients is the cause of winter-kill; common sense would suggest that plants trying to grow in frozen ground are rapidly and severely stressed by the lack of available moisture.
Notice the unstated assumption that any change is for the worse if anything is affected by that change. The assumption is that this is the most perfect of worlds and any change means less perfection. Considering the vast and never ending changes in our planet’s climate, one has to look upon these true believers as utterly chauvinistic, climate-wise. Perhaps we should have them recite the names of species that have come and gone. That will take them a very long time and may finally bring them to understand that change is this planet’s middle name.
@Brian:
“Is there anyone out there who has ever grown an outdoor plant, who didn’t know that a warm spell during the winter followed by more winter weather would screw up the plant’s growth”
You have a good point, but these clever people got paid to find out for sure.
As with many of these type of research projects, this might be a bit of a boondoggle in terms of a cool place to go. The scientists have to justify the expense of going there. Reminds me of the study of growing seasons for grapes that required that every winery in France had to be visited in August. Of course they would have to stop in ChristChurch for a holiday going and coming – and take some time to see New Zealand.
so…burn more fossil fuels.
win-win for everyone and everything.
This paper is a laugh. So many problems with it as others point out. It is just another blowhard AGW, oh no the sky is falling. Here is one where I laughed.
“It may eventually be warm enough in the winters so that plants can photosynthesize and grow year round, like they do in the tropics,” she said. “It’s this transition part that plants are not adapted for.”
What a joke. Even with the most ludicrous and extreme modeled temperature rise that time will be many, many centuries down the road. The island’s yearly average temperature is 9.4 C or 48.9 F.
In order to qualify as tropical the average temperature would need to rise 25.6 C or 28.1 F. Also the coldest parts of the year would even need to warm more.
Of course some people will wring their hands and moan about it, lapping up every word as gospel.
You’d think alarmists would eventually get tired of having their panties in a twist. But no. I guess they’ve adapted to it.
This is not the first study trying to link climate change to biota at Campbell Island. For example Cunningham and Moors (1994) suggested that the declining numbers of Rockhopper a Penguins was due to rising sea surface temperatures. Unfortunately while there are decadal swings of up 0.7 degrees C, there is negligible long term trend in sea surface temperature or air temperature.
What if they found [an] increase in shrub growth? Find another ‘cherry’? You know that is the way they work. If they fail, they fail to get money. That is it.
Oh my goodness, we are doomed. TWO shrubs, are they edible? I think they meant to pick real cherries, but missed.
Please remember what happened the last time the Arctic was ice free, vegetation moved north. Most of the pending global warming, we are told, will be felt as you head away from the equator and towards the poles, in winter and at night. They can swing this one how they like but LONGER growing seasons is what will happen IN GENERAL. Don’t believe me just look at the past.
Eat these. I hear they taste yummy.
Dracophyllum longifolium
http://en.wikipedia.org/wiki/Dracophyllum_longifolium
Dracophyllum scoparium
http://nzpcn.org.nz/flora_details.aspx?ID=1816
Here is evidence of SHORTER GROWING SEASONS from Dr. Michael Mann.
A longer period of average summer temperature in the UK, Germany, France, Denmark, Poland and Russia means a shorter growing season. Please do not apply logic, use the climate models.
Another PhD thesis that should not have been granted, then hyped by PR.
Goodness, quite the academic machine grinding away to make sausage.
If this were the case…..there wouldn’t be an evergreen alive in the south
This people are idiots
New Zealand is not the best place to cut out discs to discover how our global biosphere will react to warmer temperatures. The vegetation there is more isolated than I care to remember and this is just from the top of my stupid head. In nearby Australia they even have unique fauna.
I hear it can happen with Spring frosts too. 😉