Robert P. Long

Sugar maple growth in relation to nutrition and stress in the northeastern United States

Sugar maple, Acer saccharum, decline disease is incited by multiple disturbance factors when imbalanced calcium (Ca), magnesium (Mg), and manganese (Mn) act as predisposing stressors. Our objective in this study was to determine whether factors affecting sugar maple health also affect growth as estimated by basal area increment (BAI). We used 76 northern hardwood stands in northern Pennsylvania, New York, Vermont, and New Hampshire, USA, and found that sugar maple growth was positively related to foliar concentrations of Ca and Mg and stand level estimates of sugar maple crown health during a high stress period from 1987 to 1996. Foliar nutrient threshold values for Ca, Mg, and Mn were used to analyze long-term BAI trends from 1937 to 1996. Significant (P < or = 0.05) nutrient threshold-by-time interactions indicate changing growth in relation to nutrition during this period. Healthy sugar maples sampled in the 1990s had decreased growth in the 1970s, 10-20 years in advance of the 1980s and 1990s decline episode in Pennsylvania. Even apparently healthy stands that had no defoliation, but had below-threshold amounts of Ca or Mg and above-threshold Mn (from foliage samples taken in the mid 1990s), had decreasing growth by the 1970s. Co-occurring black cherry, Prunus serotina, in a subset of the Pennsylvania and New York stands, showed opposite growth responses with greater growth in stands with below-threshold Ca and Mg compared with above-threshold stands. Sugar maple growing on sites with the highest concentrations of foliar Ca and Mg show a general increase in growth from 1937 to 1996 while other stands with lower Ca and Mg concentrations show a stable or decreasing growth trend. We conclude that acid deposition induced changes in soil nutrient status that crossed a threshold necessary to sustain sugar maple growth during the 1970s on some sites. While nutrition of these elements has not been considered in forest management decisions, our research shows species specific responses to Ca and Mg that may reduce health and growth of sugar maple or change species composition, if not addressed.

Temporal and spatial patterns in fire occurrence during the establishment of mixed-oak forests in eastern North America

Abstract Question: What was the role of fire during the establishment of the current overstory (ca. 1870-1940) in mixed-oak forests of eastern North America? Location: Nine sites representing a 240-km latitudinal gradient on the Allegheny and Cumberland Plateaus of eastern North America. Methods: Basal cross-sections were collected from 225 trees. Samples were surfaced, and fire scars were dated. Fire history diagrams were constructed and fire return intervals were calculated for each site. Geographic patterns of fire occurrence, and fire-climate relationships were assessed. Results: Fire was a frequent and widespread occurrence during the formation of mixed-oak forests, which initiated after large-scale land clearing in the region ca. 1870. Fire return ranged from 1.7 to 11.1 years during a period of frequent burning from 1875 to 1936. Fires were widespread during this period, sometimes occurring across the study region in the same year. Fires occurred in a variety of climate conditions, including both drought and non-drought years. Fires were rare from 1936 to the present. Conclusions: A variety of fire regime characteristics were discerned. First, a period of frequent fire lasted approximately 60 years during the establishment of the current oak overstory. Second, fire occurred during a variety of climate conditions, including wet climates and extreme drought. Finally, there was within-site temporal variability in fire occurrence. These reference conditions could be mimicked in ongoing oak restoration activities, improving the likelihood of restoration success. Nomenclature: Gleason & Cronquist (1991).

Potential Species Replacements for Black Ash (Fraxinus nigra) at the Confluence of Two Threats: Emerald Ash Borer and a Changing Climate

The emerald ash borer (Agrilus planipennis; EAB) is causing widespread mortality of ash (Fraxinus spp.) and climate change is altering habitats of tree species throughout large portions of North America. Black ash (F. nigra), a moist-soil species common in the Northwoods of Minnesota, Wisconsin, and Michigan, USA, is under a double threat of losing habitat from climate change and near annihilation from EAB. Because black ash often occurs in nearly pure stands, planting non-ash species is a management strategy already underway or being planned for thousands of acres. Tools are needed to assist managers in prioritizing sites for early treatment and to select potential species to replace black ash. This study explores the implications of threats to black ash ecosystems using analyses of field data and models to assess both the threats to, and potential replacement species for, black ash in Minnesota. For our analysis we (1) assessed the status of ashes and co-occurring species in forest inventory plots throughout Minnesota; (2) modeled the risk of EAB attack for multiple years in Minnesota; (3) modeled potential impacts of climate change on tree species with current or potential future habitat in Minnesota; (4) evaluated species co-occurring with black ash in plots in Ohio and Michigan, southeast of Minnesota; and (5) synthesized these results to provide a classification for candidate replacement species, both from within Minnesota and from points farther south. Though this process is demonstrated for black ash in Minnesota, the elements to be considered and modeled would be similar for any other location with a pest or pathogen threat for a species which simultaneously faces a changing climate.

Effects of climate change on forest insect and disease outbreaks

General circulation models (GCMs) predict dramatic future changes in climate for the northeastern and north central United States under doubled carbon dioxide (CO2) levels (Hansen et al., 1984; Manabe and Wetherald, 1987; Wilson and Mitchell, 1987; Cubasch and Cess, 1990; Mitchell et al., 1990). January temperatures are projected to rise as much as 12°C and July temperatures as much as 9°C over temperatures simulated at ambient C02 (Kittel et al., 1997). Projections of precipitation are quite variable over the region, ranging from 71 to 177% of ambient levels in January and 29 to 153% of ambient in July among several GCMs (Kittel et al., 1997). Such climate changes clearly may affect the growth and species composition of our northern forests directly in ways discussed in previous chapters. In contrast with the discussions in previous chapters, this chapter steps up one trophic level to consider the effects of climate change on the populations of microorganisms, fungi, and insects that feed in and on forest trees.

The Spotted Wing Drosophila, Drosophila suzukii (Diptera: Drosophilidae): A New Pest of Concern for Black Cherry, Prunus serotina, on the High Allegheny Plateau in Pennsylvania

ABSTRACT: Drosophila suzukii (Matsumura) is an invasive insect pest native to Southeastern Asia that is now reported to have established populations in North America. We used traps baited with red wine vinegar to detect and monitor D. suzukii in four black cherry (Prunus serotina Ehrh.) and maple (Acer spp.) stands in the Allegheny National Forest in northwestern Pennsylvania. Stands ranged in age from 70 to 110 years old, with average basal area from 40 to 45 m2/ha. All stands are characterized as the intermediate Allegheny hardwood forest type with black cherry being the dominant species making up > 70% of the total stand basal area at each site (Eyre, 1980). Traps were placed in the crowns of mature black cherry from May to October 2012. In total, 11,000 D. suzukii were collected. The appearance of D. suzukii on the High Allegheny Plateau in northwestern Pennsylvania could have negative implications for fruit production, dispersal, and seed viability of black cherry and other forest species. With D. suzukiis predilection toward Prunus spp. and its unusual method of oviposition, this could be a contributing factor that impacts black cherry regeneration on the Plateau.