Upper Peninsula Of Michigan Research Articles

Physiological Constraints on the Overwintering Potential of the Soybean Aphid (Homoptera: Aphididae)

The soybean aphid, Aphis glycines Matsumura, has a heteroecious, holocyclic life cycle. Soybean aphids overwinter as eggs, hatch in the spring, reproduce asexually, and undergo three or more generations on buckthorn, Rhamnus spp., before migrating to a secondary host such as soybean, Glycine max (L.) Merr. The ability of different soybean aphid life stages to survive low temperatures potentially experienced during fall or winter is not known. The objectives of this study were to determine the supercooling point (SCP) of various soybean aphid life stages and to determine the annual probability that winter temperatures within the North Central region of the United States would equal or fall below the mean SCP of soybean aphid eggs. Aphid eggs are considered the most cold-hardy stage; therefore, their SCP can be used as a conservative estimate for aphid overwintering mortality. In our study, eggs had the lowest mean SCP (approximately −34°C) among all life stages, whereas gynoparae and oviparae had the highest mean SCPs (approximately −15°C). During the winter, extreme low air temperatures are likely to reach or exceed the mean SCP of soybean aphid eggs in portions of northern Minnesota, northern Wisconsin, and the upper peninsula of Michigan. Thus, widespread successful overwintering in the northern United States and southern Canada is less likely than in Illinois, Indiana, Ohio, Iowa, southern Minnesota, southern Wisconsin, and the lower peninsula of Michigan.

Seasonal and Spatial Relationship of Chemistry and Toxicity in Atmospheric Particulate Matter Using Aquatic Bioassays

In light of current interest in better understanding the environmental impact of atmospheric particulate matter (PM), a new strategy has been employed to screen the relative toxicities of ambient and source aerosols. Short-term and acute aquatic bioassays using Ceriodaphnia dubia and a green alga (Selenastrum capricornutum) as test organisms have been in use for many years in the regulation of wastewater effluents. These tests have been employed in the present study to compare the toxicity of water extracts of atmospheric particulate matter and dichloromethane (DCM) extracts that have been transferred to dimethyl sulfoxide and diluted in water. Atmospheric PM was collected at four sites located near the south shore of Lake Michigan and one site in Michigan's Upper Peninsula at discrete events during three seasons. Parallel chemical analyses of the two extracts directly assessed the relation between the chemical composition and the toxicity of the extract. Inductively coupled plasma analysis of the metals in the water extract and gas chromatography-mass spectroscopy of the organics in the DCM extract showed a relationship between high toxicity and high water-soluble copper concentration and high secondary organic aerosol tracers in the extracted aerosol. Although previous fractionation studies have not looked at water-soluble copper, significant toxicity has been measured in the semipolar and polar organic fractions of ambient aerosols and diesel exhaust particles, which are the fractions in which secondary organic aerosol components would be expected. For the water extracts, the summer samples were consistently more toxic than the autumn or spring samples. There was not a seasonal pattern for the toxicity of the DCM extracts; however, spatial differences were apparent. The toxicity end points of select samples from one site qualitatively correlate with the high polycyclic aromatic hydrocarbon concentrations. Additionally, high toxicity in the July DCM extracts from another site may be tied to the presence of the insecticide carbaril. The seasonal and spatial variations captured in the toxicity results in this study tend to qualitatively correlate with trace organic components and metals and not bulk particulate matter composition.

Editorial

Editorial Rita Gross and Terry Muck For twenty-five years, this journal has come out annually. In those twenty-five years, the journal has had only two editorial teams. David Chappell, the founding editor, edited the first fifteen volumes from his post at the University of Hawai'i. Then the team of Terry Muck and Rita Gross took over, editing the next ten volumes. This is the last volume we will co-edit, and we want to acknowledge and celebrate our collegial journey. Given our many differences, we, and more importantly the success of our work together, are living proof that dialogue works. Terry describes himself as a theologically conservative Christian, and Rita, a convert to Buddhism who is theologically liberal, was brought up in an extremely conservative Christian setting. Each of us knows a lot about the other tradition. Terry has lived in Sri Lanka and has studied Theravada Buddhism for years. He teaches world religions at a conservative Christian seminary. Rita is an expert on feminist theology, including Christian feminist theology. She taught world religions at a regional state university to an almost completely Christian student body for many years. For ten years we worked together to edit this journal, and also edited two books that began as special sections in this journal. Usually we met twice a year to work as an editorial team, once at the American Academy of Religions meeting, wherever it might be, and once at Rita's house in Wisconsin. Terry has a summer home in Michigan's upper peninsula, and Rita's Wisconsin home is on the way to that summer home. In those ten years, our theological differences in no way impeded our collegiality or our ability to work together to increase interreligious understanding between Buddhists and Christians. We always enjoyed our differences, and our common fervor to promote appreciation of religious diversity. In this world in which religious differences cause so much trauma and pain, we offer our experience as a model of the fact that integrity can cope with significant theological differences. We do not share the same theological vision of the world, yet neither of us has ever doubted the integrity of the other person or thought that our theological differences were more important than our vision of a world in which people could disagree about theology without demonizing each other. The quarter century of Buddhist-Christian interchange that has been chronicled in this journal makes that point over and over. We have been happy and grateful to have had some part in fostering a new and better chapter in the history of interreligious interchange. Copyright © 2005 The University of Hawai'i Press

Impacts of Climate Variation and Catchment Area on Water Balance and Lake Hydrologic Type in Groundwater-Dominated Systems: A Generic Lake Model

Lakes are a major geologic feature in humid regions, and multiple lake hydrologic types exist with varying physical and chemical characteristics, connections among lakes, and relationships to the landscape. The authors developed a model of water fluxes through major components of groundwater-dominated lake catchments in a region containing thousands of lakes, the Northern Highland Lake District (NHLD) of northern Wisconsin and the Upper Peninsula of Michigan. The model was calibrated with data from widely differing lakes using the same set of simple equations to represent the hydrologic type, water residence time, and amount and timing of stream and groundwater flows of representative lakes in today's climate. The authors investigated the sensitivity of the water balance of a set of three connected representative lakes and their catchments to systematic increases and decreases in the precipitation regime, and contrasted results using lake-specific morphometry to those for a lake having size and shape parameters typical of the region. Results indicate that a common set of equations can successfully represent major water balance characteristics of the three basic lake hydrologic types (hydraulically mounded, groundwater flowthrough, and drainage) in the NHLD. Sensitivity of modeled lakes varied by lake type, with drainage lakes more strongly buffered against substantial hydrologic changes in extreme climate scenarios. Catchment-scale water budgets differed substantially among lakes of different types, yet can be understood along a continuum of relative catchment size. These results suggest that a simple model of lake and catchment water balance can be extended to entire lake districts, where the detailed morphometry of most lakes is not well known.

Trends in Secondary Organic Aerosol at a Remote Site in Michigan's Upper Peninsula

The trends in secondary organic aerosol at a remote location are studied using atmospheric fine particulate matter samples collected at Seney National Wildlife Refuge (NWR) in northern Michigan. Detailed analysis of particle-phase organic compounds revealed very low concentrations of primary anthropogenic emissions and relatively high levels of organic di-, tri-, and tetracarboxylic acids thought to be indicators of secondary organic aerosols. Seasonal changes in these organic compounds were tracked by analyzing composites of monthly average samples. The concentration of aromatic and aliphatic dicarboxylic acids peak in July and taper off in the fall, which coincides with fine particle organic carbon concentration. In contrast, a chemical mass balance model used to quantify primary sources of particulate matter shows higher contributions from primary emissions in the winter. Complementing the monthly average concentrations, event-based composites of high volume samples were used to track the different species of secondary organic aerosol at the Seney NWR location. The distribution of aliphatic diacids and the aromatic di- and triacids varied with different atmospheric conditions, which suggests different precursor gases for these secondary organic aerosol components. The aliphatic diacid concentrations track with ambient concentrations of particle-phase pinonic acid. In addition, back-trajectories for the eight event-based composites are compared to the organic acid distributions and are linked to the distribution of organic acids present in the composites.

Continental-scale climate forcing factors and environmental change at Glimmerglass Lake in the upper Peninsula of Michigan

Previous palaeoecological studies have shown that there have been major range shifts in Tsuga (hemlock) during the middle and late Holocene that seem to indicate climatic cooling and an increase in available moisture. We examined lake-level changes and peatland growth at Glimmerglass Lake and peatland in the Sylvania Wilderness Area to determine if the mid-Holocene increase in moisture indicated by the pollen record also influenced lakes and wetlands. Sphagnum peat began accumulating at the site at 6240 cal. yr BP. Diatom-inferred depth reconstructions show that the lake level rose 2 m and the peatland expanded out of its basin at 5300 cal. yr BP. All of these changes occurred as the last remnant of the Laurentide Ice Sheet disappeared and orbital forcing reduced seasonality relative to the early Holocene. We conclude that these continental-scale factors caused increased moisture availability in the Upper Peninsula of Michigan, resulting in rising lakewater levels and peatland expansion.

Beyond the Bench: Fish Tales to Ensure Health

Fishermen are known for telling tales of their catches that tend toward exaggeration. A new kind of fish tale, however, doesn’t stretch the truth when making a point to the Hmong community in Milwaukee, Wisconsin, about the hazards of eating fish contaminated with methylmercury and polychlorinated biphenyls. A video produced by the Community Outreach and Education Program at the NIEHS Marine and Freshwater Biomedical Sciences Center at the University of Wisconsin–Milwaukee communicates in a simple, understandable, and culturally sensitive way the risks of eating contaminated fish and teaches methods of catching and preparing fish that can reduce these risks. The Hmong, refugees from Southeast Asia, are avid anglers and traditionally fish to support large families with an average of 7–8 children. But these fishers often have little understanding of the pollution and contamination of the waterways of Wisconsin and the fish that populate them. The goal of the center program, developed in partnership with the Hmong/American Friendship Association and the Sixteenth Street Community Health Center, is to communicate to the inner-city Hmong population the hazards associated with eating contaminated fish in a way that results in active consideration of the issues within the context of the group’s fishing practices. The centerpiece of the outreach program is a bilingual Hmong–English video titled Nyob Paug Hauv Qab Thu (Below the Surface). The video presents scientifically sound information on safe fish consumption. It also acknowledges the Hmong cultural tradition of fishing while showing which fish are safest to catch and ways to make fish safer to eat prior to cooking, including how to remove fins, fat, and other parts of the fish where toxicants accumulate. The video is packaged with a laminated card that provides shorthand tips on safer catching and preparation, and a kitchen magnet with similar information. To date, approximately 750 video/card/magnet packets have been distributed by community workers through local stores, doctors’ offices, and Hmong festivals where the video has been showcased. Follow-up to assess the impact of the videos is currently under way. John Dellinger, a center researcher who studies the effects of fish consumption in Native American populations and who is featured in the film, has also shown the video or supplemental materials to audiences of Intertribal Council and InterTribal Fisheries Assessment Program officials in the Upper Peninsula of Michigan, as well as to Tahitian Ministry of Health officials. Officials of the Michigan Ojibwa and the government of Tahiti have asked that the film be adapted for their communities. Dellinger plans to work on productions for both of these groups in 2005. In an extension of the community outreach program, the center has developed a life sciences classroom module for middle-school students that explores the behavioral effects of mercury and lead contamination, both of which affect inner-city Hmong populations. The module provides a hands-on, inquiry-based experiment about a complex organism’s behavioral integration with its environment, and what happens when that environment becomes contaminated. In the module, students observe fathead minnows in the classroom to learn and characterize their normal reproductive behavior. Students then watch a video produced by the center that shows the behavior of mercury- and lead-exposed fish. Based on their understanding of normal behavior, students analyze the differences that exposure to the toxic metals makes in the fish. The differences are dramatic because although the behavior is affected, the fish show no outward physiological signs of toxicity. Teachers can then draw an analogy to human exposure to mercury through fish consumption, and to lead through paint chip ingestion, and the potential resulting effects on human behavior. Teachers were trained during a summer workshop to teach and evaluate the experiment. In the next two years, 11 teachers from Milwaukee public schools and from area suburban schools with the largest Hmong student populations will introduce this module, using the video as a cross-cultural tool to support it.

Anuran Population Monitoring: Comparison of the North American Amphibian Monitoring Program's Calling Index with Mark-Recapture Estimates for Rana clamitans

Abstract The North American Amphibian Monitoring Program uses a ranked, categorical calling index to estimate anuran abundance. However, there are few data assessing the assumption that calling index values are accurate indicators of population sizes or to suggest ranges of population sizes associated with specific values of the calling index. This study compared mark-recapture population estimates and call rates to calling index values for Green Frogs (Rana clamitans) in the Upper Peninsula of Michigan. Mean mark-recapture population size estimates and mean calls per minute were greater in ponds with larger calling index values. Similarly, calls per minute increased with increasing population size, although rate of increase declined at high population sizes possibly caused by a higher proportion of noncalling satellite males at high densities. Sex ratios in breeding habitat along the edges of ponds were increasingly male biased as population size increased. These data support the assumption that calling ...

Averting grid collapse - system control and restoration in emergency conditions

This article focuses on how the Midwest Independent Transmission Operator and American Transmission Company managed a disaster recovery event of significant proportions and duration following outages caused by a flood in the upper Peninsula of Michigan in May 2003. It is an example of how transmission system operators avoid system collapse and isolation and prevent cascading outages over a wider proportion of the electric transmission delivery system in a region.

RIPARIAN AND UPLAND BREEDING-BIRD ASSEMBLAGES ALONG HEADWATER STREAMS IN MICHIGAN'S UPPER PENINSULA

Comparative studies of riparian and upland bird communities have focused primarily on larger streams (greater than second order). We examined breeding-bird assemblages in relation to their proximity to small head-water streams in northern hardwood forests of the Otter River watershed in Michigan's Upper Peninsula, USA. At 10 study sites, we used fixed-radius point counts to survey bird assemblages and measure forest habitat characteristics along riparian and upland transects. Forest structure and composition differed between riparian and upland areas, with more conifer stems and higher conifer basal area on riparian transects. We detected 46 bird species during 1999 and 2000. During each year, total bird abundance was similar for riparian and upland areas, whereas bird species richness and evenness was higher in riparian areas. When we pooled bird species by foraging guild, we found that foliage-gleaning birds were more abundant in riparian areas. We found 12 bird species exclusively in riparian areas and only 2 species exclusively in the uplands. The northern parula (Parula americana) and Black-burnian warbler (Dendroica fusca) were among 5 species more abundant on riparian transects, whereas the least flycatcher (Empidonax minimus) and red-eyed vireo (Vireo olivaceus) were among 5 species more abundant on upland transects. Although the vegetative gradient between riparian and upland habitat was subtle along these first- and second-order streams, breeding-bird assemblages differed between riparian and upland forests. This suggests that individual bird species respond to vegetative features of even narrow riparian areas. Managers working in northern and mixed-hardwood forests therefore should consider maintaining habitat diversity in the form of native conifers, even on the smallest first-order streams.

Birthweight by gestational age and sex at a rural referral center.

Determine the distribution of birthweights in singleton births by gestational age and gender at Marquette General Hospital, a rural referral center in Michigan's upper peninsula. Birth log data were examined for prenatal factors and obstetrical outcomes. The birthweight distribution was compared to published values, and a linear regression model of prenatal factors was developed. Our median birthweights were significantly greater than published values. Males were 128 g heavier than female infants after adjusting for gestational age. In a multivariable linear regression model, birthweight was significantly associated with gestational age, sex of the infant, maternal age, primigravida status of mother, and maternal diabetes (all p<0.01). Using published standards resulted in an overdiagnosis of large for gestational age and an underdiagnosis of small for gestational age. Local birthweight distributions can differ significantly from historical or national distributions. The development of birthweight distributions accommodating for prenatal factors is needed.

Late Holocene Lake-level Variation in Southeastern Lake Superior: Tahquamenon Bay, Michigan

Internal architecture and ages of 71 beach ridges in the Tahquamenon Bay embayment along the southeastern shore of Lake Superior on the Upper Peninsula of Michigan were studied to generate a late Holocene relative lake-level curve. Establishing a long-term framework is important to examine the context of historic events and help predict potential future changes critical for effective water resource management. Ridges in the embayment formed between about 4,200 and 2,100 calendar years before 1950 (cal. yrs. B.P.) and were created and preserved every 28 ± 4.8 years on average. Groups of three to six beach ridges coupled with inflections in the lake-level curve indicate a history of lake levels fluctuations and outlet changes. A rapid lake-level drop (approximately 4 m) from about 4,100 to 3,800 cal. yrs. B.P. was associated with a fall from the Nipissing II high-water-level phase. A change from a gradual fall to a slight rise was associated with an outlet change from Port Huron, Michigan/Sarnia, Ontario to Sault Ste. Marie, Michigan/Ontario. A complete outlet change occurred after the Algoma high-water-level phase (ca. 2,400 cal. yrs. B.P.). Preliminary rates of vertical ground movement calculated from the strandplain are much greater than rates calculated from historical and geologic data. High rates of vertical ground movement could have caused tectonism in the Whitefish Bay area, modifying the strandplain during the past 2,400 years. A tectonic event at or near the Sault outlet also may have been a factor in the outlet change from Port Huron/Sarnia to Sault Ste. Marie.

Colonizing Inland Lakes: Consequences of YOY Fish Ingesting the Spiny Cladoceran ( Bythotrephes cederstroemi)

Recently the exotic cladoceran Bythotrephes cederstroemi colonized inland lakes in the Upper Peninsula of Michigan, facing warmer temperatures and greater exposure to smaller fish than in coastal waters of Lake Superior. However, the long caudal appendage (spine) of Bythotrephes protects it against young-of-the-year (YOY) fish predation. After experience, small fish (30-60 mm TL) develop aversion behavior, explaining why this prey item rarely occurs in their stomachs, despite ingestion of other prey species with core body lengths between 2-3 mm. Here we compare laboratory and field size-dependent feeding patterns for YOY of two common fish species (yellow perch, Perca flavescens; bluegills, Lepomis macrochirus) with field patterns from a typical bait-fish species (spottail shiner, Notropis hudsonius). Behavioral responses of bluegills indicate that deterrence is not a simple linear function of spine length, but that longer spines offer disproportionate protection, explaining why long spines are present at birth. Stomach contents of small perch (30–60 mm TL) confirm size-dependent avoidance, with only occasional consumption of Bythotrephes and rare puncture of stomach walls. However, examples of ingestion and frequent stomach puncture were found in the thinner-walled stomachs of spottail shiners. Out of 140 small fish collected when this species encountered high densities of Bythotrephes, 77 had Bythotrephes in stomachs or lower digestive tracts, and 50 (65%) had spines protruding through gut walls. Clearly, this bait-fish species is capable not only of ingesting large numbers of Bythotrephes, but of receiving injury in the process.

Spirit of Marshfield: Celebrating 10 years of critical care transport excellence

“You're from where?” It's a question repeated to every seasoned transport crewmember who performs public relations site visits. I doubt my colleagues in Dallas or Denver encounter the geographical unfamiliarity so common to our locale. If you visualize the midpoint of a line drawn from Minneapolis to Green Bay and go 30 miles south, you'll discover Marshfield, Wisconsin. There, situated atop “the hill,” amid an unassuming rural backdrop in a conservative town of 20,000, you'll note the medical complex that comprises the 504-bed Saint Joseph's Hospital and 350-physician Marshfield Clinic. Together, they serve as the major tertiary care and referral center for patients in central and northern Wisconsin, with extension into the upper peninsula of Michigan.

Eutypella Canker Clustering and Volume Loss in the Western Upper Peninsula of Michigan

Abstract Trees with Eutypella canker in four stands were found to cluster near other infected trees. Volume losses due to the canker were minimal. Harvest time appears to influence the likelihood of infection.

Population increase in Kirtland's warbler and summer range expansion to Wisconsin and Michigan's Upper Peninsula, USA

The threatened Kirtland's warbler Dendroica kirtlandii breeds in stands of young jack pine Pinus banksiana growing on well-drained soils in Michigan, USA. We summarize information documenting the range expansion of Kirtland's warbler due to increased habitat management in the core breeding range in the Lower Peninsula of Michigan during 1990-2000. We collected records and conducted searches for the species in Michigan's Upper Peninsula and Wisconsin over 1978-2000. During that time 25 males were found in Wisconsin and 90 males in the Upper Peninsula. We documented colonization of Michigan's Upper Peninsula by six ringed males from the Lower Peninsula of Michigan. Four ringed birds also moved back to the core breeding range, including two males that made two-way movements between the core breeding range and the Upper Peninsula. Thirty-seven females were observed with males from 1995 to 2000, all in Michigan. Nesting activities were noted for 25 pairs and at least nine nests fledged young. One male ringed as a fledgling returned to breed in two subsequent years. After a 19-year period of population stability, the Kirtland's warbler population increased four-fold during 1990-2000, most likely in response to a tripling in habitat area. This increase in sightings and documented breeding may be related to habitat availability in Michigan's Upper Peninsula and to saturation of habitat in the main breeding range. The increase in extra-limital records during 1995-1999 corresponds to the time when the population went frorn the minimum to the maximum projected population densities, and a decline in natural wildfire habitat was just offset by new managed habitat for the Kirtland's warbler.

Small Mammal Abundance and Diversity in Forests With and Without Canada Yew, &lt;em&gt;Taxus canadensis&lt;/em&gt;

Canada Yew (Taxus canadensis) has been extirpated from much of its former range in northeastern North America possibly due to logging, fire, agriculture, and browsing by White-tailed Deer (Odocoileus virginianus). We compared the relative abundance and species diversity of small mammals in five northern hardwood stands containing Canada Yew to five adjacent stands without Canada Yew in the Upper Peninsula of Michigan, during October-November 2000. Overall, 72 individuals were captured (53 in yew, 19 in non-yew); dominant species were Short-tailed Shrew (Blarina brevicauda), Deer Mouse (Peromyscus maniculatus), and Red-backed Vole (Clethrionomys gapperi). Overall mean (+ sd) capture rate (individuals/100 adjusted trap nights) in sites with yew (5.5 + 2.2) was greater (P = 0.04) than mean capture rate in sites without yew (1.9 + 1.0). Three indices of species diversity suggested greater small mammal diversity in stands with Canada Yew understories in northern hardwood forests.

The anatomy of a range expansion: changes in cranial morphology and rates of energy extraction for North American red squirrels from different latitudes

Species with expanding ranges provide unique opportunities to examine environmentally induced adaptations in ecological traits and anatomical characteristics. Since the late 1800s, the North American red squirrel (Tamiasciurus hudsonicus) has expanded its range into the central hardwoods of the United States in conjunction with increasing agricultural fragmentation. We examined whether red squirrels from the central hardwoods (west‐central Indiana, USA) displayed differences in foraging behaviors and morphology relative to red squirrels from conifer‐dominated environments (upper peninsula of Michigan, USA), a biome in which red squirrels evolved. Specifically, we measured rates of energy extraction, variation in cranial morphology, and diet preference between red squirrels from both regions. In addition, we compared foraging behaviors of red squirrels from the central hardwoods to those of a competitor that coevolved with nut‐producing trees, the gray squirrel (Sciurus carolinensis). Red squirrels from Indiana and Michigan differed significantly in the efficiency with which they used food items, with individuals from each region extracting calories at a more rapid rate for items that were common in their region. The enhanced efficiency of southern red squirrels feeding on black walnuts (Juglans nigra) was correlated with geographic differences in cranial morphology; skulls of southern squirrels were larger, with longer jaws and higher metrics associated with greater mandibular force than northern squirrels. Contrary to our expectations, red squirrels from Indiana and Michigan did not differ qualitatively in preferences for food items, suggesting that diet choice may be governed by perishability of food items rather than by rates of energy extraction. Gray squirrels were more efficient than Indiana red squirrels in using all food items, and differed only slightly from red squirrels with regard to preference for food items. Measures of efficiency of resource use, after accounting for species‐specific metabolic requirements, suggest that red squirrels are unlikely to compensate ecologically for declining gray squirrel populations in fragmented portions of the central hardwoods, with potentially adverse effects for forest regeneration and succession. Our results demonstrate that invading species can display significant flexibility in adapting to new environments, but they may not be flexible enough to exploit resources in a manner comparable to native species.

A success model: Marquette General Health System.

The Marquette General Health System (MGHS) initiated its telehealth program in 1995 with eight network sites in Michigan's Upper Peninsula. There are currently almost 30 active sites in this network that provide clinical, educational, and administrative services. In this article, MGHS is assessed against four criteria, namely, integration, evaluation, expansion, and acceptance. Several assessment data collection strategies were employed among patients, providers, administrators, and rural community members. This paper delineates the extent to which the MGHS program meets the definition of success as defined by this four-level model. Data and anecdotal evidence are presented that illustrate that the MGHS program has been successful in its attempt to increase access to medical services for the rural population of the Michigan Upper Peninsula, as well as facilitate medical and health education, and home care services.

Beech bark disease in northern hardwood forests: the importance of nitrogen dynamics and forest history for disease severity

Beech bark disease has been a major cause of mortality of American beech (Fagus grandifolia Ehrh.) in North America during the past century. Previous studies have suggested a positive relationship between disease severity and both bark nitrogen content and tree size, presumably due to higher rates of infestation by beech scale insects, which allow more extensive infection of the tree by Nectria fungi. Recent concerns about nitrogen saturation in northeastern forests, particularly in old-growth forests, led us to examine patterns of disease severity as a function of bark tissue nitrogen content in old-growth and second-growth forests in the Adirondack region of New York and northern Maine. Trees growing in old-growth stands possessed significantly higher levels of bark nitrogen than similarly sized trees in second-growth forests. The severity of disease symptoms was more acute in the old-growth forests and was positively correlated with the percent nitrogen of the bark in both forest types. Comparisons of the coefficients of variation between beech bark sampled from disease-free forests in the upper peninsula of Michigan and that sampled from diseased forests indicated that elevated bark nitrogen concentrations in diseased trees were a cause and not an effect of disease presence. While there was no difference in disease severity between control and nitrogen-fertilized forests in Maine, these forests had both been exposed to the disease for longer time periods than the other studied forests and they are likely approaching nitrogen saturation.