The information comes from an e-Science Update co-authored by scientists from two U.S. Forest Service research stations, the Northern Research Station (NRS) and the Southern Research Station (SRS), and published by SRS.
“The update provides an overview of the status and extent of hemlocks in the in eastern United States based on FIA inventories conducted by SRS and NRS,” according to Randall Morin, a research forester with the NRS’ FIA program and the primary author. “It also incorporates research by NRS scientists and the results of pest surveys conducted by the Forest Service’s State and Private Forestry Program.”
Two native species of hemlock – eastern and Carolina – grow in eastern North America. Although a minor component in most of the forests of the eastern United States, high densities of eastern hemlock are found in New England and the mountains of the Southeast and Mid-Atlantic. The Carolina hemlock, similar in appearance to the eastern hemlock, is found only on rocky mountain slopes of the Southern Appalachian region.
Researchers conducted the analysis on 20 years of data collected across 433 counties stretching from southern Maine into northern Georgia. They found an overall increase in live-tree hemlock basal area in counties infested with hemlock woolly adelgid as well as those without infestations.
A tiny insect introduced into the United States from East Asia, the hemlock woolly adelgid, feeds at the base of hemlock needles, defoliating and eventually killing trees. “Since the insect was first noticed in the 1950s it has expanded its range at between 4.7 and 12.7 miles a year,” according to Andrew Liebhold, an NRS research entomologist. “Hemlock woolly adelgid currently infests about 45 percent of the range of hemlocks in the United States and 41 percent of the total hemlock basal area.” These percentages are up 26 percent and 25 percent respectively since 2004.
“The analysis also showed that the general regional trend in the East over the past 50 years has been one of increasing hemlock volume, even with infestation by the hemlock woolly adelgid,” according to Sonja Oswalt, an SRS forester and co-author. “Even though the insect has caused substantial negative impacts on hemlock at stand-level scales, analysis of FIA data suggests that infestations have not yet reduced the overall abundance of hemlock, even in states where hemlock woolly adelgid has been active for decades.”
The authors caution that the trend of increasing hemlock volume may not last much longer. “Despite increasing hemlock volume over the last four decades across most of the eastern United States, the regions with long-established populations of hemlock woolly adelgid are also the regions where hemlock is accumulating slowest,” Morin said. “Net growth rates decrease as years of infestation increase, and mortality rates increase, with mortality starting to equal net growth in areas where hemlock woolly adelgid has been present for 10 to 20 years.” As time goes on the trend of increasing abundance may begin to reverse.
The Science Update is available at: http://www.srs.fs.usda.gov/pubs/38492
The mission of the U.S. Forest Service is to sustain the health, diversity, and productivity of the nation’s forests and grasslands to meet the needs of present and future generations. The agency manages 193 million acres of public land, provides assistance to state and private landowners, and maintains the largest forestry research organization in the world. The mission of the Forest Service’s Northern Research Station is to improve people’s lives and help sustain the natural resources in the Northeast and Midwest through leading-edge science and effective information delivery.
Jane Hodgins | EurekAlert!
The personality factor: How to foster the sharing of research data
06.09.2017 | ZBW – Leibniz-Informationszentrum Wirtschaft
Europe’s Demographic Future. Where the Regions Are Heading after a Decade of Crises
10.08.2017 | Berlin-Institut für Bevölkerung und Entwicklung
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...
Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
20.09.2017 | Life Sciences
20.09.2017 | Power and Electrical Engineering
20.09.2017 | Physics and Astronomy