USFS study looks at health of Shore Pine in Southeast

The U.S. Forest Service has installed permanent monitoring locations on Wrangell Island and in other areas of Southeast Alaska to track shore pine tree survival and health status over time and to gather basic information about the insects, diseases, and other factors affecting trees.

This two-year project has a total of 50 permanent plots that are installed at five main locations in Southeast, including Wrangell Island, Prince of Wales Island, Mitkof Island, north Chichagof Island and Douglas/Juneau, with 10 plots at each location.

Shore pine grows on sites with nutrient-poor, saturated soils, such as muskegs, across the region and down to California. Since it is not a commercial timber species, little is known in Alaska or throughout its range about the factors affecting the health of this species.

The forested wetlands in which it grows are ecologically valuable habitats with diverse plant and animal communities. Moose, bear, deer, yellow-legs, sapsuckers and other animals are frequently observed in muskegs, and live and dead shore pine trees provide cavity-nesting and roosting habitat for birds and small mammals.

The project was initiated because a U.S. Forest Service “Forest Inventory Data Report” from 2011 revealed that shore pine was the only tree species in Alaska to experience a statistically significant loss of biomass, where tree mortality exceeds growth and regeneration, between the two measurement periods of 1995-2000 and 2004-2008.

According to Robin Mulvey, the Forest Pathologist with the Juneau Forestry Sciences Laboratory, plot trees are marked with small metal tags for long-term monitoring and are watched for a number of factors.

“For each tree, information is collected on tree size, crown dieback, foliage disease and insect damage, western gall rust infection on the branches and main stems, wounds caused by animals or neighboring tree-fall and stem decay fungi,” Mulvey said. “Information on how long dead trees have been dead is also gathered by looking at whether trees still retain fine branches and dead needles, or whether no coarse branches remain and the tree is largely decayed. Tracking the occurrence of recently killed trees can help us to assess whether this study picks up the pulse in mortality revealed by the Forest Inventory Plot data that prompted this project. Plots will be revisited every 5 years to evaluate tree survival and regeneration, and changes in tree health, over time.”

Preliminarily, the data shows that shore pine grows under harsh site conditions and is damaged by a variety of fungi, insects and animals. However, most damaged trees are still successfully regenerating in most shore pine stands, and shore pine is expected to persist on suitable sites over time.

“Western gall rust, caused by a rust fungus, creates circular swellings on the branches and main stems of most shore pine trees,” Mulvey stated. “These galls are often invaded by secondary fungi and insects that girdle and kill stems above/beyond the gall, causing branch dieback, topkill or whole tree mortality, depending on where the attacked gall was located.

“A species of sawfly was observed feeding on shore pine foliage in more than one-third of our monitoring plots; this species had not been previously reported in Alaska but has likely been historically present due to its widespread distribution across Southeast. Nearly half of shore pine had wounds on their main tree boles, many of these are attributable to porcupines, bears and other animals, while canker fungi may cause others,” Mulvey continued.

Mulvey added that the project is long term in its scope.

“Data from the completed plot network will be analyzed and reported in the coming year, and monitoring of the plot network will continue over time,” she said.