New study: Temperate Plants Love Milder Temperatures

Guest essay by Eric Worrall

A field study has suggested that plants growing in cool temperate regions respond well to milder temperatures.

The abstract of the study;

Boreal and temperate trees show strong acclimation of respiration to warming

Plant respiration results in an annual flux of carbon dioxide (CO2) to the atmosphere that is six times as large as that due to the emissions from fossil fuel burning, so changes in either will impact future climate. As plant respiration responds positively to temperature, a warming world may result in additional respiratory CO2 release, and hence further atmospheric warming. Plant respiration can acclimate to altered temperatures, however, weakening the positive feedback of plant respiration to rising global air temperature, but a lack of evidence on long-term (weeks to years) acclimation to climate warming in field settings currently hinders realistic predictions of respiratory release of CO2 under future climatic conditions. Here we demonstrate strong acclimation of leaf respiration to both experimental warming and seasonal temperature variation for juveniles of ten North American tree species growing for several years in forest conditions. Plants grown and measured at 3.4 °C above ambient temperature increased leaf respiration by an average of 5% compared to plants grown and measured at ambient temperature; without acclimation, these increases would have been 23%. Thus, acclimation eliminated 80% of the expected increase in leaf respiration of non-acclimated plants. Acclimation of leaf respiration per degree temperature change was similar for experimental warming and seasonal temperature variation. Moreover, the observed increase in leaf respiration per degree increase in temperature was less than half as large as the average reported for previous studies, which were conducted largely over shorter time scales in laboratory settings. If such dampening effects of leaf thermal acclimation occur generally, the increase in respiration rates of terrestrial plants in response to climate warming may be less than predicted, and thus may not raise atmospheric CO2 concentrations as much as anticipated.

Read more (paywalled): http://www.nature.com/nature/journal/vaop/ncurrent/full/nature17142.html

From the press release;

Plants may be better at acclimatising to rising temperatures and contribute less to carbon dioxide in a warming world than some have previously thought, a new study suggests.

Concern carbon dioxide from plant growth could make global warming worse in the future

Study suggests plants are better at acclimatising to rising temperatures than previously thought

This means they are less likely to become a net source of CO2 for the planet in the future

“Maybe some of our models are over-predicting the degree to which plant respiration will cause accelerating feedback that speeds up climate change,” said Professor Peter Reich, an ecologist and plant physiologist from the University of Minnesota who led the study published today in Nature.

Plants absorb carbon dioxide through photosynthesis and release it when they burn sugar to produce energy in a process known as respiration.

For every 10 degrees Celsius of temperature increase, plants are known to double their rate of metabolism, which has led to fears that global warming will trigger a positive-feedback loop, switching plants from being a net carbon dioxide sink — absorbing more carbon dioxide than they release — to becoming a net source of the warming gas.

According to Dr Reich, however, the jury is still out on how big this problem is.

“The best models on the planet disagree wildly about what will happen in 40 or 50 years, with some saying that the land surfaces will still be a strong sink, but others saying they will become a big source,” he said.

Read more: http://www.abc.net.au/news/2016-03-17/carbon-dioxide-from-plants-less-less-of-a-global-warming-problem/7248052

The authors of the study reference another study performed in Australia, which suggested that elevated CO2 and warmer temperatures are mildly beneficial.

In my opinion, this study is yet more evidence that plants are adaptable – that a few degrees global warming would have a negligible impact, on most of the world’s ecosystems.

Added by Anthony

Here’s the press release

Plants’ ability to adapt could change conventional wisdom on climate change, U of M study finds

UNIVERSITY OF MINNESOTA

MINNEAPOLIS/ST.PAUL (3/16/2016) – Plants speed up their respiratory metabolism as temperatures rise, leading to a long-held concern that as climate warms the elevated carbon release from a ramped-up metabolism could flip global forests from a long-term carbon sink to a carbon source, further accelerating climate change.

However, a new University of Minnesota study with more than 1,000 young trees has found that plants also adjust – or acclimate – to a warmer climate and may release only one-fifth as much additional carbon dioxide than scientists previously believed, The study, published today in the journal Nature, is based on a five-year project, known as “B4Warmed,” that simulated the effects of climate change on 10 boreal and temperate tree species growing in an open-air setting in 48 plots in two forests in northern Minnesota. Scientists measured how much carbon dioxide the artificially warmed plants respired – released into the air via their leaves – and learned that over time, the trees acclimated to warmer temperatures and increased their carbon emissions less than expected.

Researchers increased temperatures at the test plots by 3.4 degrees C, an increase that might happen by the end of the 21st century, and learned that plants grown and measured at those higher temperatures increased their leaf respiration by an average 5 percent, compared to plants in ambient temperatures. Had the juvenile plants not been acclimated to the higher temperatures, their respiration would have increased by 23 percent over the plants in ambient temperatures.

The findings are important to climate change research because prior research with tiny plants in laboratory settings had found that warming over a period of weeks accelerated plants’ release of carbon much more than the Minnesota team found in the more realistic long-term forest experiment, which measured change from 2009 through 2013 and considered both experimental and seasonal temperature variations.

“This work is important because most global C cycle models ignore this respiratory adjustment and project accelerated climate warming because of elevated respiratory CO2 release,” says Peter Reich, professor of forest resources at the University of Minnesota, who led the project and is the paper’s lead author. “Now, with better data we can make those models more realistic. ”

“Although these results are ‘good news’ in the sense that the underlying physiology of plants is not going to make the warming of the planet radically worse, the problem we have created in the first place with our greenhouse gas emissions from fossil fuel burning still exists,” he says. “So, we very much still need to cut our carbon emissions in the coming decades by enough to stop climate change.”

###