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Browsing by Subject "Fraxinus nigra"

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    Host influence on the cold hardiness of the emerald ash borer, *Agrilus planipennis* Fairmaire (Coleoptera: Buprestidae)
    (2014-12) Christianson, Lindsey
    The emerald ash borer, Agrilus planipennis Fairmaire, is an invasive insect in North America that has caused extensive damage to ash trees throughout its invaded range. The range of Fraxinus spp., specifically black ash (Fraxinus nigra) extends farther north than the known A. planipennis distribution. The ability of an insect to withstand cold, or its cold hardiness, is important in limiting its northern distribution. The cold hardiness of A. planipennis from green ash and black ash was assessed using two laboratory measures, supercooling points and lower lethal temperature, in laboratory- and naturally-infested A. planipennis larvae. Supercooling points of A. planipennis larvae from black and green ash, with medians ranging from 25.5 to 32.6°C and 24.0 to 34.2°C respectively, were not significantly different during the winters of 2012-13 and 2013-14, although the laboratory infested larvae tested in November 2011 had significantly warmer supercooling points. Kaplan-Meier estimates of the likelihood of freezing of larvae from black ash and green ash were not significantly different between tree species or between years. A high proportion of larvae died after being frozen, but freezing did not kill all larvae. Lower lethal temperatures for 50% of the population (LT50) were estimated after accounting for the proportion of larvae that would survive freezing. LT50s of larvae from green ash were 35.2°C (95% CI 35.9°C, 34.7°C) in the winter of 2012-13 and 33.4°C ( 34.1°C, 32.1°C) in the winter of 2013-14. Larvae from black ash had estimated lower lethal temperatures of 33.4°C ( 34.4°C, 32.3°C) in 2012-13 and 33.1°C (≤ 37.5°C, 35.5°C) in 2013-14. Agrilus planipennis larvae overwinter under the bark of ash trees, so larvae may not be experiencing winter air temperatures. To determine temperatures under the bark of ash trees, temperature probes were placed under the bark of both green and black ash at 1.4m high and at the base of the tree on the north and south faces. Weather stations recorded air temperature. Daily minimum temperatures under the bark of green ash ranged from 0.5 to 4.7°C warmer than daily minimum air temperatures, and temperatures were 1.2 to 5 degrees warmer under the bark of black ash. Temperatures at the base of the trees provided the most insulation, possibly due to any snow cover adding to the insulative effect of the bark. During the time in which we took measurements, the air temperature fell below 30°C for an average of 16 hours during the winter of 2012-13. Temperatures under the bark of green ash did not reach -30°C, and temperatures under the bark of black ash fell below -30°C, on average, for 2.6 hours. In 2013-14, air temperature was 30°C or colder for an average of 146.1 hours, 78.1 hours under the bark of green ash, and 118.7 hours under the bark of black ash. Because of the differences in air temperatures and temperatures under the bark of trees, we cannot use air temperature to directly predict A. planipennis mortality. Because under-bark temperatures do not reach the temperature required to kill 50% of the population of A. planipennis every year, further research should consider how the larvae survive sublethal temperatures for longer periods of time.
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    Wildlife community data in black ash wetlands
    (2021-10-01) Grinde, Alexis R; agrinde@d.umn.edu; Grinde, Alexis R; NRRI Avian Ecology Research Lab
    Black ash wetlands cover approximately 1.2 million hectare of wetland forest in the western Great Lakes region, providing critical habitat for wildlife. The future of these wetlands is critically threatened by a variety of factors, including Emerald Ash Borer (Agrilus planipennis; EAB), which has been eliminating native populations of otherwise healthy ash throughout the Great Lakes Region since it was discovered in 2002. To quantify the potential impacts of tree mortality from EAB on wildlife communities, we measured seasonal bird, mammal, and amphibian diversity in black ash wetlands using a dual approach: 1) documenting bird and amphibian species across 27 mature reference black ash wetlands in northern Minnesota, USA and 2) assessing how bird, mammal, and amphibian communities respond to experimental manipulations of black ash forests that emulate mortality and management strategies related to the potential impact of EAB. A total of 85 wildlife species were recorded for the entire study including 57 bird species, 5 amphibian species, and 23 mammal species. Results from the reference sites show that hydrologic regime, percentage of ash canopy cover, and understory cover were important habitat characteristics for bird and amphibian communities. Results from the experimental sites show there may be short-term increases in species richness for mammal and bird communities associated with changes in forest structure due to ash mortality; however, anticipated changes resulting from EAB-caused mortality, particularly conversion of these sites to non-forested wetlands, will lead to significant shifts in bird and mammal community composition. Loss of ash may cause declines in forest-dependent species and increases in open-canopy and wetland-associated species. Additionally, while increased ponding extent and longer hydroperiods may be beneficial for some amphibian species, the loss of the forest canopy will result in an overall decrease in bird diversity and reduce forest connectivity for all species. Our results indicate the potential for significant large-scale impacts of black ash mortality on forest-associated wildlife. Management strategies that focus on establishing alternative trees species to maintain long-term forest cover and structural complexity in these wetlands will help maintain and conserve wildlife diversity.