Now showing items 21-29 of 29

    • The potential of lodgepole pine in Alaska

      Cushing, Alina (2005-08)
      The introduction of non-native trees should be informed by various perspectives. In the case of forestry in high-latitude regions, managers face the challenge of finding cold-hardy species adequately adapted to harsh climatic environments; Lodgepole pine (Pinus contorta Dougl. Ex. Loud.) has been introduced to three regions at or above its natural northern latitudinal extent; Alaska, Iceland, and northern Sweden. Analysis of interviews in each region revealed the structure of common arguments, including underlying assumptions and perceptions of the natural world. Results of a mail-out-survey to the Alaskan public indicate that a considerable portion of the public is concerned about the possibility for adverse ecological effects on the native ecosystem. However, acceptance of non-native trees increased under certain circumstances; e.g. small-scale ornamental plantings, and when economic benefit is demonstrated. In comparisons of twenty-year growth data of lodgepole pine in Alaska with native white spruce (Picea glauca), lodgepole pine achieved greater height, diameter, and volume. The response of lodgepole pine in all three regions to scenarios of climate change was predicted using tree-ring analysis. Results indicate a negative response (reduced growth) in the Fairbanks area, a positive response (increased growth) in Delta and Glennallen, and a positive response at all but one Icelandic site and both Swedish sites. Overall, lodgepole pine appears relatively well-adapted to the present and modeled future environments of interior Alaska, Iceland, and northern Sweden.
    • An evaluation of fuels conversion treatments in Interior Alaska

      St. Clair, Thomas Barton (2006-05)
      The study site was a permafrost-free upland site with an east-northeast aspect, west/northwest of Fairbanks at mile 10 on the Cache Creek road in a mixed hardwood/spruce stand of Betula neoalaskana Sarg., Populus tremuloides Michx., Populus balsamifera L., Picea glauca (Moench) Voss, and Picea mariana (Mill.) BSP. In treatments designed to encourage hardwood growth, four different methods were used for removing vegetation (shearblading, masticating head, drum-crusher, and chainsaw thinning), resulting material was then left in place, burned, or chunked and removed. Treatments were evaluated using man/machine hour and dollar cost data and Permanent Sample Plot (PSP) data. PSPs were installed within six different fuels conversion treatments and a control for monitoring purposes. A pilot study revealed that debris pile burning changed soil color (more red) and soil water repellency properties. All treatments that had one full growing season showed hardwood regeneration. Shearblading and leaving material on site was the least labor-intensive treatment and least costly. Burning windrows was the least labor-intensive and least costly method of removing material from the site.
    • A dendroclimatological study of long-term growth patterns of yellow-cedar trees in Southeast Alaska

      Sink, Scott E. (2006-08)
      Yellow-cedar is a very long-lived, commercially important tree species found along the coasts of Southeast Alaska and also in small populations in Prince William Sound. However, this is the first study of the tree's annual ring growth patterns in the region. Tree cores were collected from over 400 trees across a large latitudinal gradient and cross-dated using standard dendrochronological techniques. Radial tree-ring growth was measured and compared to reconstructed weather station data to gain a better understanding of the climatic conditions favoring yellow-cedar growth. We found consistent, significant positive correlations between ring widths and mean monthly temperatures in August, previous January, and previous December, and negative relationships with May and December precipitation. Climate indices we created using these variables explain approximately 25% of growth variability in five distinct yellow-cedar populations. Long-term growth patterns in tree populations going back three centuries were similar across all sites, specifically the sustained below mean growth during the 1800s. Yellow-cedar at the northern limits of its distribution shows a common growth signal which may indicate the influence of larger pressure anomalies, such as EI Nino-Southern Oscillation (ENSO), on the climate factors affecting the trees.
    • Growth response of lutz spruce saplings to the removal of a herbaceous competitor and the application of fertilizer in Southeast Alaska

      Dickson, Emily; Barber, Valerie; Sparrow, Stephan; Harris, Norman (2014-08)
      Herbaceous competitor species such as fireweed can impact future survival and growth of Lutz (Picea x lutzii Little, Pinaceae) spruce saplings. Fertilizer is applied to crop trees in order to supply more nutrients to promote growth. However, fertilizer benefits competitor species as well. Literature regarding the impacts of competition for resources between fireweed and spruce saplings are lacking, but the impacts of resource competition on seedling growth and fireweed are documented as significant. Seedlings are distinguished from saplings by differences in height and/or diameter. In order to test the influence of both competitor species and added fertilizer, we analyzed growth response of Lutz spruce saplings to fireweed removal and applied fertilizer through treatments and controls using a two by two factorial experiment. Results revealed that fireweed removal had a positive effect on sapling growth response, while added fertilizer alone showed no effect on sapling growth response. I found a strong, positive correlation between soil moisture and fireweed cover. I also found a strong, positive relationship between sapling growth and soil moisture as well as sapling growth and fireweed cover. This study demonstrates that spruce saplings positively responded to fireweed removal compared to the application of fertilizer. More importantly, the overall conclusion is that when saplings are not N limited soil, moisture is the driving factor in sapling height growth. The long-term effects of harvesting an efficient nitrogen competitor species are not well known and could be detrimental to future site fertility.
    • Freeze-thaw effect on soil microbial activity with biochar application in subarctic soils

      Castillo, Sunny M.; Soria, Juan Andres; Ping, Chien Lu; Michaelson, Gary; Leigh, MaryBeth (2013-08)
      Alaska has limited agricultural production due to extreme climatic conditions and weakly developed soils, which affect productivity. In higher latitudes, freeze-thaw cycles are common and influence soil biology and nutrient dynamics, offering a unique opportunity to investigate the use of soil amendments like biochar to enhance native biota and soil's intrinsic properties. Biochar for this study was produced from locally harvested black spruce (Picea mariana), using a fixed bed pyrolysis unit. The production of biochar was electronically controlled with temperatures kept at 550°C, and residence times manipulated by a mechanical auger, in order to yield five distinct biochar products. Chemical analyses showed differences among the biochar samples, including cation exchange capacity (CEC), micronutrients and pH. To evaluate the influence of each biochar on higher latitude native soils and biota, a response surface model was employed to design a set of experiments that measured CO₂ accumulation during a 15-day freeze -thaw cycle. Microbial activity during this experimental phase was monitored before and after freeze-thaw. Results of this study demonstrated that cultivated soils amended with biochar showed higher microbial activity before and after freeze-thaw. Forest soil on the contrary showed no significant results when amended with biochar. These results on different microbial activity were likely due to the amounts of organic carbon present in each soil type. The study serves as an evaluative tool for determining the impact that biochar may have in subarctic regions of the US that have limited agricultural potential as a result of climatic and native soil conditions.
    • Mapping landscape values and forest uses on the Tongass National Forest

      Schroeder, Britta; Verbyla, David; Brinkman, Todd; Fix, Peter (2014-05)
      Throughout the world, humans are often faced with the challenge of sustaining economic development while also promoting environmental stewardship. Such is true for the management history of the Tongass National Forest, where the U.S. Forest Service is transitioning away from harvesting old-growth and moving towards a more economically and environmentally sustainable approach. To measure the preferences of local community members affected by this transition, I conducted an interdisciplinary case study on the Wrangell Ranger District in Southeast Alaska. Community members from Wrangell mapped landscape values, acceptable and unacceptable forest uses. By assessing these landscape values and forest uses with respondents' attitudes towards forest management alternatives, I identify spatial locations of conflicting timber harvest uses and recommend forest management objectives for the district. Through public participation, communities can provide spatially explicit input during the planning process, which creates opportunities for managers to incorporate community needs and better prioritize management objectives.
    • Surface water dynamics of shallow lakes following wildfire in boreal Alaska

      Altmann, Garrett L.; Verbyla, Dave; Fox, John; Yoshikawa, Kenji (2013-12)
      Wildfire is ubiquitous to interior Alaska and is the primary large-scale disturbance regime affecting thawing permafrost and ecosystem processes in boreal forests. Since surface and near surface hydrology is strongly affected by permafrost occurrence, and wildfire can consume insulating organic layers that partially control the thickness of the active layer overlying permafrost, changes in the active layer thickness following fire may mark a distinct change in surface hydrology. In this study, we examined surface area dynamics of lakes following wildfire in four regions of Interior Alaska during a 25-year period from 1984 - 2009. We compared the surface water dynamics of lakes in burned areas relative to lakes in adjacent unburned (control) areas. Lake area changes in the short-term (0-5 years), mid-term (5-10 years), and long-term (>10 years) were analyzed. Burn severity, as a function of radiant surface temperature change, was also explored. Surface water changes were greatest during the short-term (0-5 years) period following fire, where burn lakes increased 10% and control lakes decreased -8% (P=0.061). Over the 5-10 year post-fire period, there was no significant difference in lake dynamics within burned areas relative to control unburned areas. On average, there was an 18 percent decrease in surface water within burned areas over the >10 year post fire time period, while unburned control lakes averaged a 1 percent decline in surface water. The long term declining trend within burned areas may have been due to talik expansion and/or increased evapotranspiration with revegetation of broadleaf plants. Fire had the greatest effect on radiant surface temperature within two years of a fire, where radiant temperatures increased 3-7°C in the most severely impacted areas. Temperature differences between burn and control areas remained less than 1°C as vegetation reestablished. There was no correlation between radiant temperature change and decreasing lake area change. Conversely, there was a trend between lake area differences increasing in size and increases in temperature. While fire displayed the greatest effect on lake area in the short-term, a combination of fire, climate, and site-specific conditions dominate long-term lake area dynamics in Alaska boreal forest.
    • Soil surface organic layers in the Arctic foothills: development, distribution and microclimatic feedbacks

      Baughman, Carson A.; Mann, Daniel; Verbyla, David; Valentine, David (2013-12)
      Accumulated organic matter at the ground surface plays an important role in Arctic ecosystems. These soil surface organic layers (SSOLs) influence temperature, moisture, and chemistry in the underlying mineral soil and, on a global basis, comprise enormous stores of labile carbon. Understanding the dynamics of SSOLs is a prerequisite for modeling the responses of arctic ecosystems to climate changes. Here we ask three questions regarding SSOLs in the Arctic Foothills of northern Alaska: 1) What environmental factors control their spatial distribution? 2) How long do they take to form? 3) What is the relationship between SSOL thickness and mineral soil temperature during the growing season? Results show that the best predictors of SSOL thickness and distribution are duration of direct sunlight during the growing-season, upslope-drainage-area, slope gradient, and elevation. SSOLs begin to form within decades but require 500-700 years to reach steady-state thicknesses. SSOL formation has a positive feedback on itself by causing rapid soil cooling. Once formed, mature SSOLs lower the growing-season temperature and mean annual temperature of underlying mineral soils by 8° and 3° C, respectively, which reduces growing degree days by 78%. How climate change in northern Alaska will affect the region's SSOLs is an open and potentially crucial question.
    • Growth and Yield of Black Spruce, Picea mariana (Mill.) B.S.Pl., in Alaska

      Rosner, Carolyn; Packee, Edmond; Ping, Chien-Lu; Maich, John C. (University of Alaska Fairbanks, School of Natural Resources and Agricultural Sciences, 2004-08)
      Black spruce, Picea mariana (Mill.) B.S.P., is largely overlooked in Alaska because of its small size and slow growth. Growth and yield information is therefore limited or nonexistent. Presented here are the first polymorphic site index (height-age) curves and height-diameter functions for predicting height and volume for Alaska black spruce. Models are accurate for trees up to 50 feet in height and 8 inches DBH. Predicted stem volumes range from 0.006 ft3 to 21.8 ft3 for trees between 0.5 and 11.5 inches DBH Sampled tree dimensions range from 5.5 to 78.0 feet tall and from 0.4 to 11.0 inches DBH. Sampled breast-height ages range from 49 to 257 years; average age-to-breast-height is 26 years. This research, although limited, also characterizes general stand-level structure and community composition for Alaska black spruce. 60 Permanent Sample Plots (PSPs) representing 20 stands were established throughout the Tanana Valley, with stand inventory conducted according to a consistent protocol. Stand densities range from 137 to 2,907 trees per acre; stand volumes ranged from 8 to 2,507 ft3 per acre. Stand density index values range from 6 to 453. Periodic remeasurement of PSPs will yield valuable information about stand evolution and community type change.