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Forest Epidemics

April 6, 2010

A couple of articles on climate impacts on forests and forest impacts on climate.

#1-Forest epidemic is unprecedented phenomenon, still getting worse

Full Article at: http://oregonstate.edu/ua/ncs/archives/2010/apr/forest-epidemic-unprecedented-phenomenon-still-getting-worse

The Swiss needle cast epidemic in Douglas-fir forests of the coastal Pacific Northwest is continuing to intensify, appears to be unprecedented over at least the past 100 years, and is probably linked to the extensive planting of Douglas-fir along the coast and a warmer climate, new research concludes.

Scientists in the College of Forestry at Oregon State University have also found that this disease, which is affecting hundreds of thousands of acres in Oregon and Washington and costing tens of millions of dollars a year in lost growth, can affect older trees as well as young stands – in some cases causing their growth to almost grind to a halt.

The newest findings were just published in Forest Ecology and Management, a professional journal.

Swiss needle cast is a native fungal disease specific to Douglas-fir that was first described in Europe. It rarely kills trees but causes discoloration, loss of needles and growth reduction, and is common in the Pacific Northwest wherever Douglas-fir grows. However, it caused significant problems only in recent decades along the coast.

Starting in 1984, an epidemic began to develop, and it significantly worsened after 1996.

“It’s now clear that this epidemic is a new phenomenon, with far more severity and impact than anything we’ve observed from Swiss needle cast in the past,” said Dave Shaw, an assistant professor at OSU and director of a cooperative designed to fight this disease. “We’ve known of this disease for decades but it was considered a non-issue in terms of forest health. A perfect storm of conditions that favor this fungus has caused a major epidemic that is still growing.”

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Depending on the multiple factors that influence it, it’s possible it could ultimately have an impact on up to two million acres of forests near the Oregon coast, and change the face of forestry in a huge region.

The new study concluded that warmer conditions, especially from March through August, are associated with significantly reduced growth in diseased trees, which may reflect earlier fruiting of the fungus. Wet, drizzly conditions in May through July are also important. The warm, wet conditions within 20 miles or so of the Pacific Ocean make those areas a hotspot of disease in coastal Oregon and Washington.

“We now know that weather is a driver in the epidemiology and spread of this disease,” said Bryan Black, an assistant professor of forestry based at OSU’s Hatfield Marine Science Center. “We can’t say yet whether climate change is part of what’s causing these problems, but warmer conditions, milder winters and earlier springs would be consistent with that.”

Full Article at: http://oregonstate.edu/ua/ncs/archives/2010/apr/forest-epidemic-unprecedented-phenomenon-still-getting-worse

#2-Model Predicts Shifts In Carbon Absorption By Forest Canopies

Full Article at: http://www.terradaily.com/reports/Model_Predicts_Shifts_In_Carbon_Absorption_By_Forest_Canopies_999.html

An Agricultural Research Service (ARS) scientist participated in a project to fine-tune computer models that can indicate when forest “carbon sinks” become net carbon generators instead. The results will help pinpoint the effectiveness of trees in offsetting carbon releases that contribute to higher atmospheric temperatures and global climate change.

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In the summer of 2006, the team measured tree sap flow and leaf-level photosynthetic gas exchange at different canopy levels in a stand of oaks and pines in the New Jersey Pine Barrens. These data were used to calibrate the 4C-A model to simulate the amount of carbon the tree canopy absorbs and releases into the atmosphere via photosynthesis and respiration.

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The model showed that after the gypsy moths had finished foraging, the average carbon absorption rates for the growing season dropped 25 percent to around 940 grams of carbon per square meter of canopy area. This decline meant that the stand was no longer a net carbon “sink”-it ended up adding more carbon back to the atmosphere than it had absorbed.

Full Article at: http://www.terradaily.com/reports/Model_Predicts_Shifts_In_Carbon_Absorption_By_Forest_Canopies_999.html

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