Comments
Treelines Not Universally Responding to Climate Warming
WASHINGTON – In a new research, scientists have found that treelines are not universally responding to climate warming by advancing as expected.
Treelines are the elevation or latitudinal limits where trees are capable of growth or survival and are considered to be early indicators of climate warming because they are constrained primarily by cold temperatures.
Summer temperature is widely considered to be the primary control of treeline formation and maintenance, whereas winter temperatures have previously been considered less critical because of the insulative effects of snow.
This study reveals how winter warming has overturned this prevailing view.
“Average temperatures have risen over the last century, with a more pronounced and rapid change at high altitudes and latitudes,” said Melanie Harsch from the Bio-Protection Research Centre in New Zealand.
“Within these zones, treelines are thought to be more temperature sensitive and so the rise in summer temperatures should result in an advance of treeline position,” she added.
The team found that only 87 of the 166 sites (52 percent) had advanced while simultaneously the mean annual local temperatures had increased at 111 of the 166 sites at an average rate of 0.013 degrees Celsius a year (or 1 degrees C in 77 years).
Of the remaining sites, 77 (47 percent) remained stable and only two (1 percent) had treelines that receded.
Both of the receding sites showed evidence of disturbance, indicating that regardless of form, location or degree of temperature change experienced over the last century, treeline positions have either advanced or remained static.
“Surprisingly these results reveal that treelines are not universally responding to climate warming by advancing, as expected,” said Harsch.
Another surprising result of this study was the association with winter, rather than summer, warming.
These results provide no evidence of the prevailing view that high altitude and latitude treelines are controlled only by summer temperatures.
Instead, they show that treelines are more likely to advance at sites that had warmed during the winter months.
Breaking News 24/7: Treelines not universally responding to climate warming as expected
March 8th, 2010 at 10:35 am
Where have I been for 60+ years? I never heard of the long standing theory that tree lines were controlled by “Summer” temperatures. Even the regional planting zones are controlled by “Winter” temperatures. Number of days/ hours below (X) temperature or minimum winter temperature. Could it be the people doing this study and/or this press release are not familiar with “Plant Hardiness Zones”? This research project appears to have been nothing more than a means to spend money because the results are not worth mentioning. Where are the summer temperatures increasing? These people need to have looked at regional minimum temperature range to see if the minimum temperature was increasing at a steady rate because 1 or 2 cold winter nights will kill young plants trying to establish. Cold enough temperatures for (X) period of time will kill even some established plants.
Of course that was from personal observations because I wanted to stretch the boundaries by planting trees in a zone outside of the suggested zone. If planted during a warm period the trees did fine however with a cold winter certain ornamentals were killed> Just look at the crop damage in Florida this year.