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Eastern and Carolina hemlock in the eastern United States are experiencing high mortality due to the invasive non-native hemlock woolly adelgid (HWA). The most promising means of control of HWA is the importation of natural enemies from the native range of HWA for classical biological control. Prior to release, natural enemies must be tested for suitability as a control agent, including the ability to locate the target prey. Coleopteran predators, including Scymnus coniferarum and Laricobius osakensis are under consideration as a means of biological control of HWA. Laricobius nigrinus was released in hemlock forests in 2003. It was recently discovered to hybridize with the native Laricobius rubidus. Behavioral responses of these predators to HWA and host tree foliage were observed using a 4-chambered olfactometer, and genetic analysis was used to differentiate responses of L. nigrinus, L. rubidus, and hybrids. In the olfactometer, insects are allowed to amble about the arena and respond to volatile cues from each treatment. Host foliage with and without HWA was tested, as were various comparisons of eastern versus western foliage, host versus non-host foliage, and foliage containing HWA and a congeneric feeding beetle. Olfactometer bioassays demonstrated that foliage from hosts where prey is commonly found is preferable to foliage where prey is seldom found, and that the presence of HWA-induced volatile cues is the strongest driver of behavior, and trumps the presence of a competitor. There is evidence in the study that supports the reliability-detectability phenomenon common in parasitoid biological control agents. Hybrid individuals were found to behave similarly to released L. nigrinus, although in some cases intermediate behavioral traits were evident, with respect to the parental species. This study and others support the continued need for strict testing of potential biological control agents prior to release, as well as a strong impetus for the inclusion and implementation of genetic analysis as a standard component of agent evaluation.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 157-170).

The superior growth of Grand fir (Abies grandis) compared to Douglas-fir (Pseudostuga menziesii) on suitable coastal sites has previously been recognized on the basis of qualitative observations with little empirical evidence. For example, D.E. McMullan (1977, pers. comm.) reported 18% higher volume for a grand fir tree of the same height and age as a 108-year old Douglas-fir plus tree (No. 622) This study was undertaken by Bernardy (1988) to examine possible differences in the growth of grand fir and Douglas-fir growing in a mixed 40-year-old plantation of unknown origin. Trends in height, diameter and annual volume increment between the two species over time were examined. Expected growth performance (i.e. volume and form) of each species was inferred from trends identified at time of sampling.

In British Columbia, humus form identification is widely use to infer the level of plant-available soil nutrients. This identification is based on field-observable (morphological) features. We recognize three major humu forms: Mors, Moders, and Mulls - which are differentiated according to the type of F horizon, and the presence/absence of organic matter-enriched Ah horizons. Mors represent humus forms where decomposition is dominated by fungi, with slow decomposition rates and accumulations of organic matter on the soil surface. Mors are characterized by the presence of a Fm (m - mycogenous) horizon. In contrast, Mulls represent humus forms with high rates of decomposition and faunal activity resulting in organic matter being intimately incorporated into the upper mineral soil layer instead of accumulating on its surface. Intermediate on the humus form gradient from Mors to Mull are the Moders. Moders are similar to Mors in that they have accumulations of organic matter on the surface of the mineral soil but decomposition is not fungus dominated, so they lack the diagnostic Fm horizon. The central concept of the Moder is represented by the Leptomoder, which is characterized by a Fz (z - zoogenous) horizon with an active population of soil meso- and microfauna, fungal mycelia are not present or present in small amounts. When both fungal mycelia and faunal droppings can be found, but neither clearly predominate over the other, an Fa (a - amphimorphic) horizon results. Fa horizons are characteristic of Mormoders, an integrade between Mors and Moders. Considering the prevalence of Mormoders and Leptomoders in B.C. and the difficulties in identifying Fa horizons, the aim of this study was to determine whether the morphological features used to differentiate these two Moder humus forms reflects differences in their physical, chemical and biotic properties.

This full report describes both forested and non-forested ecosystems of the Mountain Hemlock (MH) zone of British Columbia (also referred to as the subalpine MH zone, coastal subalpine forest, or coastal mountain hemlock forest). It is one of 14 technical reports intended to provide a comprehensive account of the biogeoclimatic ecosystem classification (BEC) system as well as some management implications for each zone in the province. These zonal reports should fill the gap between the general description given in “Ecosystems of British Columbia” (Meidinger and Pojar 1991) and the information on site identification and interpretation given in regional field guides (e.g., Banner et al. 1993, Green and Klinka 1994).

This pamphlet provides a summary of a fuller report also issued under the title: The mountain hemlock zone of British Columbia. It describes both forested and non-forested ecosystems of the Mountain Hemlock (MH) zone of British Columbia (also referred to as the subalpine MH zone, coastal subalpine forest, or coastal mountain hemlock forest). It covers classification, reviews of vegetation regions and environmental relationships, as well as silvicultural and resource management implications.

This research was initiated to develop an understanding of the differential radial-growth response of mature mountain hemlock (Tsuga mertensiana) trees located along a line of latitude in northwestern British Columbia. Increment core samples were collected from mountain hemlock stands located at five high-elevation sites between the Queen Charlotte Islands and Smithers. Tree ring-width index chronologies were compared to historical precipitation and air temperature data from four climate stations, as well as the El Nino Southern Oscillation and the Pacific Decadal Oscillation. No two mountain hemlock stands had the same growth response to monthly air temperature and precipitation, indicating that the trees are responding to site-specific limiting factors. The response to El Nino Southern Oscillation events was consistent along the transect, while the response to Pacific Decadal Oscillation phase changes was greatest at coastal sites and decreased towards the interior.

Thesis (Ph. D.)--Oregon State University, 1994. / Typescript (photocopy). Includes bibliographical references (leaves 109-125). Also available on the World Wide Web.