155 research outputs found
Mode-balancing far field control of light localization in nanoantennas
Light localization is controlled at a scale of lambda/10 in the harmonic
regime from the far field domain in a plasmonic nanoantenna. The nanoantenna
under study consists of 3 aligned spheres 50 nm in diameter separated by a
distance of 5 nm. By simply tuning the orientation of an incident plane wave,
symmetric and antisymmetric mode-balancing induces a strong enhancement of the
near field intensity in one cavity while nullifying the light intensity in the
other cavity. Furthermore, it is demonstrated that the dipolar moment of a
plasmonic particle can be fully extinguished when strongly coupled with a dimer
of identical nanoparticles. Consequently, optical transparency can be achieved
in an ultra-compact symmetric metallic structure
Distribution and Host Plants of \u3ci\u3eCorthylus Punctatissimus\u3c/i\u3e (Coleoptera: Scolytidae) in the Lower Peninsula of Michigan
(excerpt)
The pitted ambrosia beetle. Corthylus punctatissimus Zimmerman, infests woody saplings and shrubs 14 mm in diameter or less. The beetle bores an entrance hole into the main stem at soil level and constructs a main gallery tunnel which generally spirals downward in the stem. Egg-niche construction is followed by inoculation of symbiotic fungi and oviposition. The main stem of the host tree wilts as a result of the girdling activity of the beetle. Finnegan (1967) described the life history of C. punctatissimus infesting Acer saccharum Marshall in Ontario and Quebec
Observations of the Habits of \u3ci\u3eCorthylus Punctatissimus\u3c/i\u3e (Coleoptera: Scolytidae) Infesting Maple Saplings in Central Michigan
Corthylus punctatissimus, the pitted ambrosia beetle, infested and killed maple saplings that were 3-12 years of age with a basal diameter of 4-14 mm. The habits of the parental pair of adults are described. The beetles construct a spiral gallery system with about five egg niches per host. Half the brood reaches adult stage during the summer with a sex ratio of 1:1. No relationship was found between the number of niches, length of gallery system, or diameter of stem
The role of spatial data and geomatic approaches in treeline mapping: A review of methods and limitations
Long-Term Soil Productivity Study: 25-Year Vegetation Response to Varying Degrees of Disturbance in Aspen-Dominated Forest Spanning the Upper Lake States
Installations of the Long-Term Soil Productivity Study were established in northern Minnesota and Michigan at the Chippewa, Ottawa, and Huron-Manistee National Forests (NFs) in the early 1990s and have since provided a wealth of data for assessing the response of aspen-dominated forest ecosystems to varying levels of organic matter removal and soil compaction. An assessment of 25-year standing woody biomass indicates that neither whole-tree harvest nor whole-tree harvest combined with forest floor removal reduced forest productivity on silt-loam soils compared with conventional, stem-only harvest; however, moderate and heavy compaction did negatively impact aspen biomass and stem densities. In contrast, whole-tree harvest reduced standing biomass of aspen and all species combined on sandy soils at the Huron NF while compaction had no discernable impact. Neither treatment factor affected vegetation response at the Ottawa NF (clay soils), but reduced sample size at this site may have increased variability. Over all, the response of standing biomass and forest structure to organic matter removal and compaction treatments demonstrate that the sustainability of practices such as whole-tree harvesting and associated potential for soil impacts varies with site conditions, even when stands are dominated by the same species (e.g., Populus tremuloides)
The State of the System and Steps Toward Resilience of Disturbancedependent Oak Forests
Current ecological, economic, and social conditions present unique challenges to natural resource managers seeking to maintain the resilience of disturbance-dependent ecosystems, such as oak (Quercus spp.) forests. Oak-dominated ecosystems throughout the U.S. have historically been perpetuated through periodic disturbance, such as fire, but more recently show decline given shifting disturbance regimes associated with human land management decisions. We characterized the state of the social-ecological oak forest ecosystem in the midwestern U.S. through the perspectives of 32 natural resource professionals. Data from interviews with these change agents provided an integrative understanding of key system components, cross-scale interactions, dependencies, and feedbacks. Foremost, private landowner management decisions figured prominently in influencing oak regeneration success and were directly and indirectly shaped by a suite of interdependent ecological, e.g., deer herbivory, invasive shrub occurrence; economic, e.g., the cost of oak regeneration practices, the stumpage value of maple as compared to oak; and social forces, e.g., forestland parcelization, and personal relationships. Interviewees envisioned, and often preferred, a decline in oak dominance throughout the region, pointing to issues related to general landowner unwillingness to restore oak, the current trajectory of forest change, the threat of forest loss due to parcelization and housing development, and a combination of ecological and social factors that decrease the economic feasibility of restoration efforts. However, a decline in oak dominance may result in ecological communities that have no compositional equivalent on record and may not offer a desirable endpoint. Increasing social support offers the potential to enhance system capacity to manage for oak
Forest floor and mineral soil respiration rates in a Northern Minnesota red pine chronosequence
We measured total soil CO2 efflux (RS) and efflux from the forest floor layers (RFF) in red pine (Pinus resinosa Ait.) stands of different ages to examine relationships between stand age and belowground C cycling. Soil temperature and RS were often lower in a 31-year-old stand (Y31) than in 9-year-old (Y9), 61-year-old (Y61), or 123-year-old (Y123) stands. This pattern was most apparent during warm summer months, but there were no consistent differences in RFF among different-aged stands. RFF represented an average of 4–13% of total soil respiration, and forest floor removal increased moisture content in the mineral soil. We found no evidence of an age effect on the temperature sensitivity of RS, but respiration rates in Y61 and Y123 were less sensitive to low soil moisture than RS in Y9 and Y31. Our results suggest that soil respiration’s sensitivity to soil moisture may change more over the course of stand development than its sensitivity to soil temperature in red pine, and that management activities that alter landscape-scale age distributions in red pine forests could have significant impacts on rates of soil CO2 efflux from this forest type
Integrating LANDIS model and a multi-criteria decision-making approach to evaluate cumulative effects of forest management in the Missouri Ozarks, USA
Public forest management requires consideration of numerous objectives including protecting ecosystem health, sustaining habitats for native communities, providing sustainable forest products, and providing noncommodity ecosystem services. It is difficult to evaluate the long-term, cumulative effects and tradeoffs these and other associated management objectives. To demonstrate the capabilities of techniques suitable to support such evaluations we combined a spatially explicit landscape-scale, succession and disturbance model (LANDIS) with wildlife habitat suitability models and a multi-criteria decisionmaking framework to compare four management alternatives across a 700 km2 area of the Mark Twain National Forest in Missouri, USA. We estimated the combined, cumulative effects of tree species succession, fire disturbance, fuel accumulation, fire hazard, wind disturbance and timber harvest on future species composition, age class distribution, timber products, and wildlife habitat suitability for eastern wild turkey and eastern gray squirrel. We applied a structured, multi-criteria, decision-making framework (PROMETHEE) to analyse forest conditions and to derive weighted composite scores for seven criteria applied to each alternative management scenario. The approach provides a systematic, repeatable, transparent, spatially explicit framework for evaluating the long-term, landscape-scale cumulative effects of management alternatives. The methodology does not encompass all the factors that influence decisions about public land management, but it captures many important ones. The underlying models provide a way to test and accumulate knowledge about forest response to succession and disturbance and to use those relationships to support decision making with the best available science
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