July is summertime, when people go offline to enjoy the weather and travel, but intrepid bloggers cannot be stopped! There were 30 blog posts covering PLoS ONE articles aggregated on ResearchBlogging.org in July. And as always, really good and hard to choose from. But choose I must! This month’s winner is….
….Hannah Waters of the Culturing Science blog (with the subtitle “biology as relevant to us earthly beings”), for her post Forest canopy height: why do we care?, describing the research in the PLoS ONE aticle Recent Widespread Tree Growth Decline Despite Increasing Atmospheric CO2 by Lucas C. R. Silva, Madhur Anand and Mark D. Leithead of the Global Ecological Change Laboratory in the School of Environmental Sciences at the University of Guelph in Ontario, Canada. From the Abstract of the paper:
The synergetic effects of recent rising atmospheric CO2 and temperature are expected to favor tree growth in boreal and temperate forests. However, recent dendrochronological studies have shown site-specific unprecedented growth enhancements or declines. The question of whether either of these trends is caused by changes in the atmosphere remains unanswered because dendrochronology alone has not been able to clarify the physiological basis of such trends.
Here we combined standard dendrochronological methods with carbon isotopic analysis to investigate whether atmospheric changes enhanced water use efficiency (WUE) and growth of two deciduous and two coniferous tree species along a 9° latitudinal gradient across temperate and boreal forests in Ontario, Canada. Our results show that although trees have had around 53% increases in WUE over the past century, growth decline (measured as a decrease in basal area increment – BAI) has been the prevalent response in recent decades irrespective of species identity and latitude. Since the 1950s, tree BAI was predominantly negatively correlated with warmer climates and/or positively correlated with precipitation, suggesting warming induced water stress. However, where growth declines were not explained by climate, WUE and BAI were linearly and positively correlated, showing that declines are not always attributable to warming induced stress and additional stressors may exist.
Our results show an unexpected widespread tree growth decline in temperate and boreal forests due to warming induced stress but are also suggestive of additional stressors. Rising atmospheric CO2 levels during the past century resulted in consistent increases in water use efficiency, but this did not prevent growth decline. These findings challenge current predictions of increasing terrestrial carbon stocks under climate change scenarios.
In her blog post, Hannah says:
Lasers are cool! The LIDAR technology, originally created for studying atmospheric chemistry, reapplied to study canopy heights has allowed us to visualize our forests in a new way. (And make some beautiful pictures.) There was a lot of work put into it – and to accurately measure how our forests are changing, increasing work will have to be done to keep the maps updated to create an index of canopy height on our planet.
However, we’ve also learned that we cannot necessarily rely on traditional hypotheses in times of climate change. While trees have the capacity to remove carbon from the atmosphere and store it, other factors can confound these effects, as we read in the PLoS ONE paper. While more work certainly needs to be done on this front (using large-scale climate measures for growth instead of dendrochronology, for example), their results are certainly sobering.
I am about to notify both Hannah and the authors of the article and send them the famous PLoS ONE t-shirts as prizes. This month’s runners-up are: EcoPhysioMichelle, for blogging not one but three PLoS ONE articles last month (one, two, three), Neurosceptic (two posts – one, two), and the trio of bloggers – Kevin Zelnio, Razib Khan and Dave Munger – for discussing one of the PLoS ONE articles in their weekly podcast.
March 2009: Ed Yong
April 2009: Eric Michael Johnson
May 2009: Christie Wilcox
June 2009: Iddo Friedberg
July 2009: Toaster Sunshine and Hermitage
August 2009: Bjoern Brembs
September 2009: Alun Salt
October 2009: Andrew Farke
November 2009: John Beetham
December 2009: SciCurious
January 2010: Anne-Marie Hodge
February 2010: Princess Ojiaku
March 2010: Grrrlscientist
April 2010: Jason Goldman
May 2010: Brian Switek
June 2010: Greg Laden