Search

Laser light with photon energy near the band gap of GaAs and in Laguerre-Gaussian modes with different amounts of orbital angular momentum was used to produce photoemission from unstrained GaAs. The degree of electron spin polarization was measured using a micro-Mott polarimeter and found to be consistent with zero with an upper limit of ∼3% for light with up to ±5h of orbital angular momentum. In contrast, the degree of spin polarization of 32.3 ± 1.4% using circularly polarized laser light at the as the same wavelength, which is typical for bulk GaAs photocathodes. [ABSTRACT FROM AUTHOR]

Policy makers need research based decision analysis models that include carbon sequestration and forest products in order to make policies that are both economically viable and effective. Forests and wood products have been identified as important mechanisms for carbon sequestration and storage. Policies often cover carbon sequestration but not product storage and substitution. Furthermore, many researchers have developed and published models on carbon management. However, a gap exists in operational level models that include product substitution. We developed a model to investigate optimal stand level management with competing objectives of maximizing soil expectation value, carbon storage in the forest, and carbon dioxide emission savings from product storage and substitution. Our purpose was to produce an accurate and usable analytical product for Southeastern U.S. foresters growing loblolly pine ( Pinus taeda) in the presence of carbon policies. The decision variables were traditional stand level management variables: planting density, thinning timing and density, and rotation length. Over time these variables influence the proportion of wood going into pulp, chip-n-saw, and sawtimber where each of these classes has an expected use (carbon storage) life. Compromise programming was employed to solve the multiple-objective problem and to demonstrate the tradeoffs between the competing objectives. This type of model demonstrates a practical method for comparing tradeoffs associated with adjusting forest management for a carbon market. The difference in costs among objectives is important for decision makers considering climate change policies, as it represents the minimum value a rational landowner would accept to sequester a unit of carbon. [ABSTRACT FROM AUTHOR]

Habitat protection is a key component of endangered species conservation, but critical habitat designations are often based on limited data or habitat use during only a portion of a species' life cycle. Protected habitat around breeding pools for the endangered Jefferson Salamander (Ambystoma jeffersonianum (Green, 1827)) and their unisexual dependents (Ambystoma laterale – (2) jeffersonianum) is based upon limited movement data from primarily spring and summer seasons. Furthermore, despite their treatment as distinct species under Canada's Species at RiskAct, differences in habitat use have not been directly compared in areas where they co-occur. We used radiotelemetry to track A. jeffersonianum (JJ) and A. laterale – jeffersonianum (LJJ and LJJJ) during fall migrations to overwintering sites. We used these data and summarized available movement data from past studies that tracked movements in other periods of the annual cycle to estimate year-round critical habitat. Ambystoma jeffersonianum travelled significantly longer distances to overwintering locations than unisexuals. Individuals were more likely to overwinter next to a similar genomotype individual than not. Critical habitat encompassing the entire annual cycle of A. jeffersonianum extends up to 400–450 m from breeding ponds indicating existing regulatory habitat protections in Canada do not currently protect sufficient habitat. [ABSTRACT FROM AUTHOR]

This study analyzes the trade-off between net present value (NPV) of timber resources, and carbon sequestration and storage for a working forest, the Hofmann Forest in North Carolina, USA. Multi-objective optimization is used to determine the production possibility curves showing the relationship between NPV and carbon. We then perform a sensitivity analysis to explore alternative management strategies. For carbon yields we used aboveground pools: branches, leaves, tops and bole as estimated by the Forest Vegetation Simulator (FVS) and LOBDSS using the California Carbon Market Protocols, including product carbon. Timber yields of sawtimber, chip-n-saw and pulpwood were estimated by LOBDSS for planted stands less than 49 years of age, and FVS was used for all natural stands and planted stands 49 years and over. Our results reveal that NPV opportunity costs associated with increasing carbon sequestration at Hofmann Forest are less than the current California carbon market price. [ABSTRACT FROM AUTHOR]