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No description available.

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The Northern tamarisk beetle (Diorhabda carinulata) was introduced to the Colorado River Basin in 2004 as a biological control agent for the invasive shrub: tamarisk (Tamarix spp.). Since 2004, D. carinulata has colonized much of the Colorado River Basin, defoliating tamarisk and adapting to local abiotic cues as it has spread across the landscape. I studied the interplay of abiotic cues, tamarisk defoliation, and the population dynamics of D. carinulata along portions of the Colorado, Dolores, and San Juan rivers from 2007-2012. My results suggest that the timing and location of tamarisk defoliation can be predicted based on the abiotic cues of a location (specifically temperature and day length) and the spatial distribution of D. carinulata across the landscape. In contrast, I also found that the spatial distribution of D. carinulata was often a result of D. carinulata abandoning areas where it had defoliated tamarisk at high intensities. I found that larval abundances from the first new generation of D. carinulata produced in a year were positively linearly correlated with defoliation intensities one month later. Comparatively, generations of larvae produced later in the season were correlated with defoliation intensity along a bell curve, in which the number of D. carinulata declined in areas>50% defoliated. The timing of defoliation during the active season was correlated with the arrival of each new generation of larvae. I found the number of generations of D. carinulata produced in a year varied based on spring temperatures and fall day lengths. The timing of when spring temperatures rose above 15°C dictated when D. carinulata could begin reproductive activity, and this in turn resulted in how early in the year tamarisk could become defoliated. Day length cues governing overwintering in D. carinulata appear to have shortened by>30 min. compared to populations of D. carinulata first released in North America in 2001, resulting in longer duration of activity into the fall. We found the range of D. carinulata could grow as much as 62.8±5.6 km in a year along a linear riparian system, and populations of D. carinulata could defoliate between 24±11.2 and 116±11.2 km of river corridor tamarisk in a year.

The overall goal of this study was to develop a framework for using airborne lidar to derive inputs for the SPB infestation growth model TAMBEETLE. The specific objectives were (1) to estimate individual tree characteristics of XY location, individual bole height (IBH), diameter at breast height (DBH), length of crown (CrHT), and age for use in TAMBEETLE; (2) to estimate individual tree age using lidar-estimated height and site index provided by the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil Survey Geographic Database (SSURGO); and (3) to compare TAMBEETLE simulation results using field measurements and lidarderived measurements as inputs. Diameter at breast height, individual bole height, and crown length were estimated using lidar with an error for mean measurements at plot level of 0.16cm, 0.19m, and 1.07m, respectively. These errors were within root mean square error (RMSE) for other studies at the study site. Age was estimated using the site index provided by SSURGO and the site index curves created for the study area with an RMSE of 4.8 years for mean plot age. Underestimation of tree height by lidar and error in the site index curve explained 91% of the error in mean plot age. TAMBEETLE was used to compare spot growth between a lidar-derived forest map and a forest map generated by TAMBEETLE, based on sample plot characteristics. The lidar-derived forest performed comparably to the TAMBEETLE generated forest. Using lidar to map forests can provide the large spatial extents of the TAMBEETLE generated forest while maintaining the spatially explicit forest characteristics, which were previously only available through field measurements.

Thesis (Ph. D.) in Biological Sciences--University of Maine, 2001. / Includes vita. Advisory Committee: Eleanor Groden, Assoc. Prof. of Entomology, Advisor; Francis Drummond, Prof. of Insect Ecology; Seanna Annis, Asst. Prof. of Mycology; David Lambert, Assoc. Prof. of Plant Pathology; John D. Vandenberg, Research Entomology, USDA-ARS. Includes bibliographical references (leaves 158-175).

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The growth and productivity of British Columbia’s interior forests is largely limited by soil nutrient availability. Fertilization has been shown to be an effective silvicultural tool for increasing the development of immature stands throughout the region. This has lead to increased interest in long-term, repeated fertilization as a means of addressing timber-supply shortfalls as a result of the current mountain pine beetle (Dendroctonus ponderosae) outbreak. However, there is little information related to the impacts of repeated fertilization on the cycling of nutrients in many of these stands. This study makes use of a long-term (13-15 year) fertilization experiment in two lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm) and two interior spruce (Picea glauca [Moench] Voss and Picea engelmannii Parry) forests in the central interior of British Columbia subject to two levels (periodic and annual) of nitrogen(N)-based fertilization. The primary goal of the project was to examine the effects of different fertilizer regimes on aspects of soil chemistry. Specifically, this project was concerned with the impacts of repeated fertilization on: 1) soil carbon (C) and N cycling, and 2) soil base cation (e.g., Ca, Mg & K) availability. Soil and foliar nutrient regimes were quantified throughout the 2008 and 2009 growing seasons using ion-exchange membrane (IEM) plant root simulator (PRS) probes and traditional soil and foliar analyses. Fertilization increased N cycling at all sites, with generally elevated soil and foliar N and significant soil-foliar N relationships in several cases. Nitrate (NO3 -) increased in the fertilized plots in several cases; however, there was minimal evidence of NO3 - leaching. Greater than 90% of fertilizer-N inputs were retained onsite, suggesting these forests are not N-saturated. Soil, tree and total ecosystem C generally increased in response to fertilization, with the spruce sites exhibiting greater C accrual per unit of fertilizer N than the pine sites. Further, significant linear relationships between soil C and N were evident at all sites. At sites with poorly buffered soils (pH < 4), fertilizer treatments generally led to increased soil acidification and decreases in soil and foliar Ca. Decreases in soil Ca may have been due to significant increases in sulfate leaching; whereas foliar Ca decreases appear to be related to compromised uptake systems, potentially from increased soil aluminum. Buffering capacities, rather than forest type, appear to be the best predictor of soil and foliar Ca responses to fertilization. Despite significant changes in soil chemistry at all four sites, it does not appear that current fertilization rates are detrimentally affecting tree growth. / Graduate