Last week I had the opportunity to attend a presentation by Dr. Seth Bigelow, previously of the US Forest Service and currently doing original Forest Adaptation Research at the Huyck Biological Research Station near Rensselaerville, New York (about 20 miles southwest of Albany). Dr. Bigelow has been conducting such research for 20 years.
Bigelow’s presentation focused on the results of his latest paper published in March 2014 in the journal Climatic Change entitled: “Faster growth in warmer winters for large trees in a Mediterranean-climate ecosystem” (journal article paywalled but a free full .pdf is available here).
The study, which took place in Plumas County, California, in the conifer-covered mountains at the junction of the northern Sierra Nevada and the southwestern end of the Cascade Mountain ranges, “analyzed growth rings of five conifer species against 20th century climate trends from local weather stations” in order to predict the “likely performance of large trees [those having breast-height diameter >76 cm / ~ 30 in] in a rapidly changing climate.” This is a question of high interest because of the generally accepted view that:
“Large trees are an iconic and functionally irreplaceable element of the lower montane mixed-conifer forest, and the steady rise in surface temperature in California throughout the 20th century has rightfully engendered concern about their performance, raising the specter of a positive feedback loop in which elevated temperatures due to anthropogenic carbon emissions inhibit the ability of trees to take up carbon.”
This climate change worry seems to have been put to rest by this study – at least for the large conifers studied at this location – in which the authors state that “Our findings may help to allay such fears as regards large trees.” The authors conclude that:
“Minimum winter temperatures have been a major determinant of growth of large trees in the lower montane mixed-conifer forest in northern California over the 20th century, eclipsing even precipitation in importance. The five species studied show increased growth with higher minimum winter temperatures, a pattern that was stronger and more prevalent than decreasing growth with higher summer maximum temperatures.”
This study that shows, as with temperature-related human mortality, that the lowest temperatures may be more of a determining factor of biological success or failure than highest temperatures, at least in the temperature ranges experienced today.
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Note: Dr. Bigelow’s current study, using tree rings and tree neighborhoods to understand growth in a changing climate in sugar maple, yellow birch and hemlock, is ongoing this summer at the Huyck Preserve Biological Field Station near Rensselaerville, NY. Dr. Bigelow welcomes volunteers. Contact the Huyck Preserve at 518-797-3400.