Elevated CO2 further lengthens growing season as climate warms

Apr 23, 2014
Mid-summer phenology observations by Megan Nix in a study plot under warming and elevated CO2 within the Prairie Heating and CO2 Enrichment Experiment (PHACE), near Cheyenne, WY, USA. Credit: Steve Ausmus

(Phys.org) —A new study published this week in the journal Nature by the USDA Agricultural Research Service, and Fort Lewis College and Colorado State University researchers demonstrates that higher atmospheric CO2 concentration resulting from fossil fuel pollution lengthens the growing season.

The research, published this week, shows that the starts earlier due to and ends later due to elevated CO2, especially when water availability limits plant activity. This leads to a longer growing season.

"The Earth's response to environmental change is complex" said Dr. Heidi Steltzer, a Fort Lewis College associate professor, "in part due to multiple environmental changes occurring all at once. Over the past 40 years, Earth's growing seasons have lengthened. This change has most often been attributed to warming alone, but now we are finding there is another factor: elevated CO2."

A unique data set collected by USDA researchers Melissa Reyes-Fox and Dan LeCain enabled the testing of a conceptual model published several years ago in the journal Science. The model explains a seemingly paradoxical phenomenon: earth's growing seasons could be longer in response to climate warming, even if the active period for many gets shorter.

"If some plant species shift the timing of their active period forward but are active for a shorter duration, then the active period for other species needs to be maintained or shift later for science to explain a longer growing season." explained Steltzer. "And in fact, this is exactly what we found. While warming extends the growing season for this reason, the data showed that elevated CO2 extends both the growing season and species' active period."

Spring phenology observations by Melissa Reyes-Fox, study co-lead author, with support of a research assistant in the Prairie Heating and CO2 Enrichment Experiment (PHACE), near Cheyenne, WY, USA. Credit: Dan LeCain

"As a result, there is greater continuity of green plant cover and greater plant abundance in the grassland ecosystem than under warming conditions alone" added Dr. Jack Morgan, a USDA scientist.

These results make biological sense. Elevated CO2 is known to increase plant water use efficiency, often resulting in higher soil water content. For ecosystems like the mixed-grass prairie where annual loss of leaves in deciduous plants is often triggered by low water availability, wetter soils in the autumn ought to extend the growing season.

The effect of elevated atmospheric CO2 on plants can have great yearly variation; wet autumns make a large difference. "Elevated CO2 enhanced the effect of warming on the growing season length most in years when fall soil water content was greater," Morgan explained. "More water was conserved in the soil."

For CO2-induced soil water conservation to extend the growing season, content must already be sufficient in the late summer to prevent an early wilt. Elevated CO2 and warming led to a 29-day longer growing season in one year and a 14-day mean increase relative to warming alone over the 5-year study.

Study results indicate cause for both hope and concern. Longer growing seasons are often beneficial, especially if elevated CO2 allows plant species to remain active longer as indicated by this study. However, shifts in the timing and duration of plant species' reproduction could impact which plant species can persist and remain abundant.

"For example, elevated CO2 also affected the length of the reproductive season, often shortening its duration," said Reyes-Fox. "The time from flowering to mature seeds was shorter for several species, which could lead to timing problems with pollinators like bees and seed dispersers such as birds. This could result in less successful plant reproduction in general."

Since a longer growing season due to warming and greater atmospheric CO2 concentration depends on , changes in precipitation will determine the extent to which the growing season lengthens in the future.

"Studies like ours highlight the need to better understand the impacts of environmental changes that happen at the same time," explained Steltzer. "It is important not to look at one environmental change in isolation. Similarly, the same would apply to impacts. In the broader context, elevated CO2 has other detrimental impacts, although our study shows an apparent benefit on lengthening the growing season."

Explore further: Permafrost thaw exacerbates climate change

More information: dx.doi.org/10.1038/nature13207

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Maggnus
3.9 / 5 (7) Apr 23, 2014
So it becomes a matter of adaption. Can the species involved adapt fast enough to offset the speed of the changes arising from global warming? If a way could be found to slow things down so that the environment could catch up and maybe keep pace, the final impacts could be lessoned.
ONTIME
2.3 / 5 (12) Apr 24, 2014
If there is truly any global warming then we must look up in the sky and consider taxing sunlight, as a contradiction to the warming claim, studies show that for the last 15 years there has been no warming and the claims of land loss are hysteric when you read that Fl. has had a encroachment of 33 centimeters of shore line loss since 1870...Government can create the backdrop for hysterics to set the stage for taxes and global government but then who would you have to represent you?

We must maintain what nature provides but we need not act like ninny's and pinheads to adapt and survive our environment...science based on logic and fact will do me just fine.
Mike_Massen
3.7 / 5 (9) Apr 24, 2014
ONTIME mumbled 2 paras, first proves he has no Science training, second quoted here might open the door to ONTIME getting a base appreciation of undeniable facts
We must maintain what nature provides but we need not act like ninny's and pinheads to adapt and survive our environment...science based on logic and fact will do me just fine.
Bear in mind the Science facts:-

1. Humans add CO2 & heat environment by burning of ~230,000 Litres petrol each sec.
2. CO2 levels are rising comparatively faster than any geologic times
3. CO2 has demonstrable thermal properties rEg re-radiation
4. Oceans have ~1000 times greater capacity to absorb heat than atmosphere

High School Education in Science is a base essential to understand interpreting Scientific data Eg.
http://www.woodfo....1/trend

Logic:
Add greenhouse gas, why should temperatures *not* rise then ?
bertibus
2.3 / 5 (6) Apr 24, 2014
So global warming might not lead to starvation then?
And that's before human ingenuity helps the adaptive process.
runrig
4 / 5 (8) Apr 24, 2014
So global warming might not lead to starvation then?
And that's before human ingenuity helps the adaptive process.


Did you note the need for water in the article
For water - read rain, in a world where there will be more drought.
ubavontuba
2.6 / 5 (5) Apr 26, 2014
So global warming might not lead to starvation then?
And that's before human ingenuity helps the adaptive process.


Did you note the need for water in the article
For water - read rain, in a world where there will be more drought.
What "more drought?"

The statement, "There will be more drought." is a fallicious claim.

freeiam
2.3 / 5 (6) Apr 27, 2014
Exactly as one would expect, only one sentence of climate propaganda, excellent.

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