The analysis, one of the first to ever quantify the effect of salvage logging and replanting on future fire severity, is being published this week in Proceedings of the National Academy of Sciences, a professional journal.
It found that fire severity was 16 to 61 percent higher in logged and planted areas, compared to those that had burned severely and were left alone in a fire 15 years earlier. The study was done in areas that had burned twice – once in the 1987 Silver Fire, and again in the massive 2002 Biscuit Fire, one of the largest forest fires in modern U.S. history.
“Many forest managers in the past have assumed that salvage logging after a severe forest fire, along with replanting new trees, will reduce future fire severity,” said Jonathan Thompson, a doctoral student at OSU in the Department of Forest Science, and lead author on the study. “This is based on the assumption that removing dead trees reduces fuel loads and planting conifers hastens the return of fire resistant forests.”
“However, those assumptions have never really been tested,” Thompson said. “This analysis showed that, after accounting for the effects of topography, Silver Fire severity and other environmental variables, the Biscuit Fire severity was higher where they had done salvage logging and planting.”
It’s not completely clear from these data, Thompson said, what the causative mechanism is – the tree removal, the addition of more fine fuels to the forest floor during the logging operation, or the growth of new trees that for several decades may be very vulnerable to new fires.
The study is not, researchers said, an indictment of salvage logging – it may still have value for economic purposes or to assure the establishment of desired tree species. However, “the hypothesis that salvage-logging, then planting, reduces re-burn severity is not supported by these data,” the scientists said in their report.
“Young forests in this region are susceptible to recurring severe fires,” Thompson said. “Compared to an older forest with branches high above the forest floor, young trees are very vulnerable, whether they are planted or naturally regenerated.”
However, in the aftermath of a wildfire, removal of large dead trees followed by planting conifer seedlings does not appear to lessen the risk of severe fires in the first 10-20 years, Thompson said. This may be because the logging process leaves more available fuel on the forest floor; the dense, homogenous replantation of young trees provides a good setting for fire; or some combination of these factors over time. “Dead woody fuel . . . is only part of the fire risk story, and it may not be the most important after a few years,” the study noted.
By contrast, natural regeneration of forests, he said, appears to result in at least slightly, and sometimes significantly less risk of severe future fires. This could be because the regenerating trees are more patchy, have open gaps, more species diversity, or other factors. But the study showed that total consumption of tree crowns in a recurring fire situation is more severe in the managed stands than the natural ones, at least when there are one to two decades between fires.
This research was done with satellite data, government agency records and aerial photography, in the mixed-conifer, mixed-evergreen hardwood zones of the Siskiyou Mountains. It analyzed burn severity patterns with a commonly used metric of fire damage on almost 45,000 acres of the Biscuit Fire that had also burned 15 years earlier.
Among its conclusions:
- Areas that burned severely in 1987 tended to re-burn at high severity in 2002.
- Areas unaffected by the initial fire tended to burn at the lowest severities in 2002.
- The findings are consistent with studies that show site history influences fire severity, and that conifer plantations are associated with high severity fire.
There are some potential environmental and management implications of the research, Thompson said.
“If we do have a warmer climate that leads to increasing frequencies of wildfire in this region,” he said, “a positive feedback of high severity re-burns may favor plant species more able to deal with that regime – manzanita, ceanothus or tan oak – that could displace conifer forests.”
Managers may have few options to reduce the risk of future high severity fire within areas that have experienced recent severe burns.
Typical fuel treatments such as thinning do not have much effect on fire risk in young forests, Thompson said. There are ongoing experiments within the Biscuit Fire region to test the effectiveness of fuel breaks for slowing the spread of severe fires.
Jonathan Thompson | EurekAlert!
A sudden drop in outdoor temperature increases the risk of respiratory infections
11.01.2017 | University of Gothenburg
Urbanization to convert 300,000 km2 of prime croplands
27.12.2016 | Mercator Research Institute on Global Commons and Climate Change (MCC) gGmbH
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction