Sonic Tomographs Sound Out Tree Rot
Robert E. Marra, Ph.D.
Forests play a major role in drawing-down and storing atmospheric carbon dioxide. Currently, an estimated three-quarters of the carbon stored on land is locked up in forest ecosystems. But when a tree experiences internal decay, it starts to release carbon back into the atmosphere. Because this decay is often not visible from the outside, it’s not clear how extensive the phenomenon is. Might we have overestimated the amount of carbon that our forests can store?
Now scientists have developed a non-destructive way to measure the amount of decay inside a tree. The results show that internal decay needs to be incorporated into our carbon accounting models.
Robert Marra from The Connecticut Agricultural Experiment Station and Nicholas Brazee from the University of Massachusetts, both in the US, carried out tomographic scans on trees, to see if they measured internal decay reliably. Deep inside the Great Mountain Forest in Connecticut, the scientists selected 72 of the three most common hardwood tree species — American beech, sugar maple and yellow birch.
Using novel lightweight portable tomographic equipment, Marra and Brazee generated sonic tomographs of every tree, building up a picture of the interior. Thirty-nine of the trees were then felled, and the scientists compared the tomographic images with the relevant cross-section of tree trunk, to test the accuracy of the scanning technique in identifying internal rot.
The internal state of the felled trees verified that the tomographic scans were a reliable measure of internal decay, with errors of no more than 2%.
“In some cases, the results were quite a surprise, with decay occurring in a number of trees that showed no sign of decay externally,” says Marra, who published the findings in Environmental Research Letters (ERL).
Based on the tomography alone, Marra and his colleagues were able to identify decay in the interiors of 47 of the 72 trees. The amount of decay ranged from 0.13% to 36.7%
Current carbon sequestration models don’t directly account for internal decay. Marra and his colleagues hope that their non-invasive tomographic scanning methodology can now be applied to larger-scale forest studies to develop understanding of the extent of internal decay. Ultimately the aim is to feed this information into carbon sequestration models, so that we have a clearer picture of how much carbon our forests can store.
A Fieldbook: Great Mountain Forest
The Global Institute of Sustainable Forestry presents a new book
This field resource book is designed to make exploration and learning at Great Mountain Forest easily approachable. It will introduce the reader to the process of reading the landscape by bringing them to the places on the ground that tell the stories of the Great Mountain Forest. The intention behind each section is to document and share the best places on the ground to observe, learn and study the ecology and history of the Great Mountain Forest.
Former Dean of the School of Forestry, Sir Peter Crane, says this book “places Great Mountain Forest in context: as a part of the ever changing green mantle of northwestern Connecticut formed by climatic succession over millennia on an ancient landscape that has been influenced pervasively by people.”
The Connecticut Agricultural Experiment Station Department of Entomology
Chris T. Maier
Great Mountain Forest (GMF) is an important area where surveys are being conducted to detect invasive insects and to evaluate their impact. Chris Maier and his assistants from the Connecticut Agricultural Experiment Station are measuring the impact of the non-native lily leaf beetle on native Canada lilies that are plentiful in some areas of GMF. Based on the data from one field season, the weight of wild lilies, especially their bulbs, was significantly lower in plants with larval feeding than in those without feeding. In another project, longhorned beetles (Cerambycidae) are being trapped by a variety of methods to detect alien species and to develop an annotated checklist of the Cerambycidae of Connecticut. Thus far, over 30 species of cerambycids have been collected at GMF.
The varied forests of GMF also have yielded new records of two other non-native, invasive species—the barberry fly and the Eurasian spruce needleminer. Overall, these research projects will provide valuable information on the whereabouts, habits, and management of both unwanted alien insects and native wood-boring beetles in eastern forests.
The Connecticut Chapter of the American Chestnut Foundation
The Great Mountain Forest Chestnut Orchard was established in 2007 by the Connecticut Chapter of the American Chestnut Foundation (CT-TACF), in collaboration with Great Mountain Forest, Housatonic Valley Regional High School, and Chubby Bunny Farms. The orchard is home to backcross chestnut trees representing the 4th of six generations of chestnuts in the American Chestnut Foundation’s backcross breeding program to breed an American chestnut highly resistant to the chestnut blight and native to Connecticut. For more information, visit www.ctacf.org
Connecticut Agricultural Experiment Station
Dr. Carole Cheah
The northern forests represent the major portion of the range of eastern hemlock, Tsuga canendensis Carriere, under threat from the exotic pest, hemlock woolly adelgid, Adelges tsugae Annand or HWA. Populations of HWA infesting eastern USA originate from southern Honshu, Japan, but over 50 years of adaptation and range expansion has led to the extensive spread of this insect from Georgia to Maine. Current management strategies center on biological and chemical control to slow the spread of this devastating pest. There is a need for biological control agents of A. tsugae which are better adapted to these northerly climates as current imported predators from the Pacific Northwest, Japan, and China originate from temperate maritime or warm continental regions.
Great Mountain Forest, with its high elevation pristine forest in USDA Plant Hardiness Zone 5b experiences some of the coldest winters in Connecticut and represents a unique opportunity to conduct adelgid-related research in an environment that parallels that of its counterparts in northern New England. Winter survival studies of HWA and its imported ladybeetle predator, Sasajiscymnus (= Pseudosymnus) tsugae, conducted by Dr. Carole Cheah, of the Valley Laboratory, Connecticut Agricultural Experiment Station, Windsor, CT, in cooperation with Great Mountain Forest, Corp. have been ongoing since 2001 (Fig.1).
These studies have recorded the field adaptation and survival of S. tsugae on a novel prey species, balsam woolly adelgid, Adelges piceae Ratz. (BWA) (Fig. 2), and developed cold-hardy strains of S. tsugae on HWA and BWA. In addition, plots monitoring the growth and health of healthy, uninfested hemlocks (Fig. 3) in a range of habitats at Great Mountain Forest have provided important baseline data for comparison with HWA infested stands.
Laurie Fortin and Scott Heth
Monitoring Avian Productivity and Survivorship is a constant effort banding project aimed at monitoring bird populations by gathering information about PRODUCTIVITY – the ability of individual bird species to reproduce and SURVIVORSHIP of adult birds from year to year. The intent is to not only document declines as they are occurring but to attribute whether the decline is the result of adults not returning back to their breeding sites or to adults not successfully producing young on their breeding territories.
Great Mountain Forest is unique in that it is one of the few old growth coniferous based forests in Connecticut, for that reason it is home to a number of northern breeders that we do not see at any of our other banding stations. These species include Slate-colored Junco, Blackburnian Warbler, Canada Warbler and Solitary Vireo.
University of Connecticut
Michael Evans, PhD Student
A research project in collaboration with GMF that has spanned over the past three years and is aimed at quantifying the size, distribution, and response to human development of Connecticut’s black bear population.
Bears across North America are recolonizing their former range, and the population in Connecticut has grown over the past several decades. This has brought bears and people into increasingly frequent contact, and provides an opportunity to understand the ecological dynamics of this interaction.
Using non-invasive hair corrals to collect hair samples from bears across their range in the state – several of which have been located on GMF property and maintained by GMF personnel. These hair samples provide genetic material that allows me to identify different individuals, track where they are being detected, and estimate relatedness between bears that were identified. Key to the success of this approach is the systematic distribution of sampling sites across study areas of interest, and collaboration with GMF has been critical to achieving this goal.
USGS Massachusetts Cooperative Fish and Wildlife Research Unit and Highstead
Stephen DeStefano and Ed Faison
In the late 20th century, moose recolonized their former southern range limit in Massachusetts and northern Connecticut, creating a two-ungulate system with white-tailed deer for the first time in almost two centuries. Landscapes with two ungulate species are uncommon in the Eastern Deciduous Forest, as deer are the sole species in most regions; consequently very few studies have examined the effects of two large herbivores on forest regeneration and diversity.
We use two types of fenced exclosures (20 × 20 meters in size) to examine three levels of large herbivore activity – white-tailed deer, deer + moose, and ungulate exclusion on forest understories in different timber harvest types and intensities in central New England. As our southernmost study site and one of the southernmost locations where deer and moose populations overlap in eastern North America, Great Mountain Forest is an especially interesting place to conduct this research. In patch cut harvests such as the GMF site, woody stem recruitment (basal area and density) above 2 meters in height is lower in deer + moose plots than in the exclosure treatments; however, herbaceous plant richness and woody species density below 2 meters is generally highest in the deer + moose plots. This indicates that browsing by both deer and moose affects both vegetation structure and composition. As forests change through time, studies such as this exclosure research become more valuable the longer they are in place. Our goal is to continue to monitor the response of forest vegetation to ungulate browsing over the next several years.
Small Mammal Herbivory
Jackie Schnurr, PhD
Jackie Schnurr has been researching plant-animal interactions at GMF for over 20 years, starting as a Research Experiences for Undergraduate student at the Institute of Ecosystem Studies (now the Cary Institute) and continuing through her PhD research at Idaho State University to her current position as Associate Professor of Biology and Environmental Science at Wells College. Jackie has been investigating how canopy tree neighborhoods influence activity of small mammals, such as red-backed voles, white-footed and deer mice, and eastern chipmunks, which in turn affects the survival of tree seeds, eventually leading to changes in seedling recruitment. Her current research at GMF is focused on small mammal exclosures that were established in 1994. She is documenting changes in both the tree seedling community and the herbaceous community that have been protected from small mammal herbivory.
Yale School of Forestry and Environmental Studies
Professor Xuhui Lee
Professor Xuhui Lee, a biometeorologist at the School of Forestry and Environmental Studies at Yale is conducting biospheric and atmospheric research at the Great Mountain Forest. Instruments bolted on a 110-ft tower measure momentum and energy inputs to the forest ecosystem, forest water use via evaporation, forest carbon uptake, and isotopic fractionation of the water and carbon fluxes. The site, located at the upwind boundary of the Connecticut airshed, is also ideally suited for regional air quality study.
U.S. Forest Service
My goal is to help develop hyperspectral remote sensing techniques to directly assess forest decline and species distribution on a landscape scale. To date this work has focused on the detection and mapping of pre-visual decline symptoms in hemlock resulting from hemlock woolly adelgid infestation. Because foliar chemistry can also be mapped with hyperspectral instruments, we are also developing decline susceptibility models that include foliar chemistry, a potentially influential factor in forest decline rates.
More recently, my work has expanded to include hardwood decline, and forest species mapping. These techniques provide a much-needed tool for the early detection of new and existing stressors, and will allow forest management agencies to focus management efforts before stands are severely impacted. Most recently we have begun an effort to transfer this technology to commercially available sensors for more widespread application.
Diana Karwan Doctoral Candidate
My research uses tracer techniques to directly asses the source and in-stream transport of suspended sediment. In Wangum Brook of Great Mountain Forest, I collect bi-monthly samples for suspended sediment and background water chemistry and seasonally perform tracer injection experiments. The injection experiments are designed to simulate the movement of suspended sediment in natural stream channels under different flow conditions. Results of these experiments illustrate the mechanisms and relative timescale of suspended sediment transport under different seasonal flow regimes. In particular, these experiments highlight the differences in water and sediment exchange between the main stream channel and adjacent storage areas, such as pools and the streambed. This work has further implications for the transport and streambed exchange of particle-bound nutrients and contaminants, such as phosphorus, heavy metals, and small pathogens.
I attended graduate school at Boston University from 2002-2007 and during that time I completed the majority of my field research at Great Mountain Forest. I stayed at the Director’s cabin during the summers and set up research plots across 5 different sites at GMF.
I performed two independent research projects. First, I assessed the impacts of the spread of the invasive plant garlic mustard (Alliaria petiolata) to forest communities, specifically measuring changes in soil nutrient cycling, microbial communities and native plant diversity and growth. Second, I performed a large-scale field experiment to test the ecological limitations to nitrogen-fixing plants.
Connecticut DEP—Division of Wildlife
When the first settlers arrived, Connecticut was mostly forested and turkeys were plentiful. As the land cleared, turkeys lost their habitat. This loss of habitat, combined with severe weather, and unregulated hunting, caused the turkey to disappear from the state and most of the Northeast by the early 1800’s.
As Connecticut changed from farms to forests, sportsmen attempted to reintroduce turkeys. These early attempts failed because the game farm-raised birds that were released couldn’t survive the wild. By relocating birds captured in the wild, the DEP Wildlife Division was able to successfully bring the wild turkey back to Connecticut.
In 1975, 22 wild turkeys were live-captured in New York, using a rocket net, and released in Northwestern Connecticut. Great Mountain Forest, was one of those release sites. Once this turkey population was established and growing, biologists captured over 300 turkeys, and released them in other areas of the state with suitable habitat. Now, turkeys are found in all of Connecticut towns.
The Connecticut Agricultural Experiment Station Department of Forestry & Horticulture
Successful conifer plantations may require protection from browse damage in areas with large deer herds. A series of studies at nine sites examined the interaction among browse protection, overstory cover, and vegetation control on growth and survival of eastern white pine (Pinus strobus) in southern New England. Bud caps placed slightly below the height of the terminal bud protected the terminal bud without causing distorted top growth during bud expansion. Rigid mesh tubes that were 91-cm tall, but not 60-cm tall tubes, frequently folded over following a heavy wet snowfall and had to be straightened to prevent distorted terminal bud growth. Underplanted seedlings grow much slower than those planted in open clearcuts.
After five years, open-grown seedlings averaged 207 cm and were above the browse line. After nine years, underplanted seedlings were the same height (130 cm) as open-grown seedlings after three years. A system using 60-cm tall rigid mesh tubes followed up with bud caps for larger seedlings will increase growth and survival in areas with high deer populations. In areas with low deer populations where minimal browse damage is anticipated, vegetation control may be an effective method of increasing growth and survival.