Landscape-scale establishment and population spread of yellow-cedar (Callitropsis nootkatensis) at a leading northern range edge

Thesis (M.S.) University of Alaska Fairbanks, 2016Yellow-cedar is a long-lived conifer of the North Pacific Coastal Temperate Rainforest region that is thought to be undergoing a continued natural range expansion in southeast Alaska. Yellow-cedar is locally rare in northeastern portions of the Alexander Archipelago, and the fairly homogenous climate and forest conditions across the region suggest that yellow-cedar's rarity could be due to its local migrational history rather than constraints on its growth. Yellow-cedar trees in northern range edge locations appear to be healthy, with few dead trees; additionally, yellow-cedar tend to be younger than co-dominant mountain and western hemlock trees, indicating recent establishment in existing forests. To explore yellow-cedar's migration in the region, and determine if the range is expanding into unoccupied habitat, I located 11 leading edge yellow-cedar populations near Juneau, Alaska. I used the geographic context of these populations to determine the topographic, climatic, and disturbance factors associated with range edge population establishment. I used those same landscape variables to model suitable habitat for the species at the range edge. Based on habitat modeling, yellow-cedar is currently only occupying 0.8 percent of its potential landscape niche in the Juneau study area. Tree ages indicate that populations are relatively young for the species, indicating recent migration, and that most populations established during the Little Ice Age climate period (1100 -- 1850). To determine if yellow-cedar is continuing to colonize unoccupied habitat in the region, I located 29 plots at the edges of yellow-cedar stands to measure regeneration and expansion into existing forest communities. Despite abundant suitable habitat, yellow-cedar stand expansion appears stagnant in recent decades. On average, seedlings only dispersed 4.65 m beyond stand boundaries and few seedlings reached mature heights both inside and outside of existing yellow-cedar stands. Mature, 100 --200-year-old trees were often observed abruptly at stand boundaries, indicating that most standboundaries have not moved in the past ~150 years. When observed, seedlings were most common in high light understory plant communities and moderately wet portions of the soil drainage gradient, consistent with the species' autecology in the region. Despite an overall lack of regeneration via seed, yellow-cedar is reproducing via asexual layering in high densities across stands. Layering may be one strategy this species employs to slowly infill habitat and/or persist on the landscape until conditions are more favorable for sexual reproduction. This study leads to a picture of yellow-cedar migration as punctuated, and relatively slow, in southeast Alaska. Yellow-cedar's migration history and currently limited spread at the northeastern range edge should be considered when planning for the conservation and management of this high value tree under future climate scenarios

Type-II InAs/GaAsSb/GaAs quantum dots as artificial quantum dot molecules

We have studied theoretically the type-II GaAsSb capped InAs quantum dots for two structures differing in the composition of the capping layer, being either (i) constant or (ii) with Sb accumulation above the apex of the dot. We have found that the hole states are segmented and resemble the states in the quantum dot molecules. The two-hole states form singlet and triplet with the splitting energy of 4{\mu}eV / 325{\mu}eV for the case (i) / (ii). We have also tested the possibility to tune the splitting by vertically applied magnetic field. As the predicted tunability range was limited, we propose an approach for its enhancement

A foundation of ecology rediscovered: 100 years of succession on the William S. Cooper plots in Glacier Bay, Alaska

Understanding plant community succession is one of the original pursuits of ecology, forming some of the earliest theoretical frameworks in the field. Much of this was built on the long-term research of William S. Cooper, who established a permanent plot network in Glacier Bay, Alaska, in 1916. This study now represents the longest-running primary succession plot network in the world. Permanent plots are useful for their ability to follow mechanistic change through time without assumptions inherent in space-for-time (chronosequence) designs. After 100-yr, these plots show surprising variety in species composition, soil characteristics (carbon, nitrogen, depth), and percent cover, attributable to variation in initial vegetation establishment first noted by Cooper in the 1916–1923 time period, partially driven by dispersal limitations. There has been almost a complete community composition replacement over the century and general species richness increase, but the effective number of species has declined significantly due to dominance of Salix species which established 100-yr prior (the only remaining species from the original cohort). Where Salix dominates, there is no establishment of “later” successional species like Picea. Plots nearer the entrance to Glacier Bay, and thus closer to potential seed sources after the most recent glaciation, have had consistently higher species richness for 100 yr. Age of plots is the best predictor of soil N content and C:N ratio, though plots still dominated by Salix had lower overall N; soil accumulation was more associated with dominant species. This highlights the importance of contingency and dispersal in community development. The 100-yr record of these plots, including species composition, spatial relationships, cover, and observed interactions between species provides a powerful view of long-term primary succession.Ye

Exploring the Influence of BC-ADM Certification on Advanced Practice Nurses’ Clinical Practice and Knowledge of Cognitive Dysfunction in Geriatric Diabetes Care

To meet the healthcare demands of an aging population one strategy is the use of advanced practice nurses (APN) in primary care (Buerhaus, DesRoches, Dittus, & Donelan, 2015). Diabetes affects 26.9% of people aged 65 and older in the United States. Mild cognitive impairment (MCI) is often unrecognized in this population (Munshi, Hayes, Iwata, Lee &Weinger, 2012). Information on APN knowledge of this comorbidity or practice characteristics regarding cognitive function assessment is limited. This capstone project sought to increase understanding of APN practice and knowledge of MCI, comparing APNs board certified in advanced diabetes management (BC-ADM) to those without certification. An original measurement tool, created with expert consultation (Cronbach’s α =.810), was sent via a secure web-based questionnaire to a convenience sample of 743 APNs in active adult practice, who were members of the American Association of Diabetes Educators. Response rate was 29% (n=216). Measured outcomes included knowledge scores on a five-item test, and reported frequency and outcomes of cognitive function assessment. Statistical significance was demonstrated between groups for cognitive function assessment at times other than Medicare Annual Well Visits (X2 (2, n=181)=11.34, p=.003, CI 95%. More APNs without BC-ADM certification completed cognitive function assessment than APNs with BC-ADM certification. Overall, knowledge level did not differ between APN groups. Correlations were found between how APNs answered questions related to executive function symptoms (t=2.71, p=\u3c .05), situations indicating unrecognized MCI (t= 2.45, p=.016), and awareness of the ADA Clinical Practice Recommendations (t=2.034, p=.044). Further research and resource development is indicated

Emerging climate-driven disturbance processes: Widespread mortality associated with snow-to-rain transitions across 10° of latitude and half the range of a climate-threatened conifer

Climate change is causing rapid changes to forest disturbance regimes worldwide. While the consequences of climate change for existing disturbance processes, like fires, are relatively well studied, emerging drivers of disturbance such as snow loss and subsequent mortality are much less documented. As the climate warms, a transition from winter snow to rain in high latitudes will cause significant changes in environmental conditions such as soil temperatures, historically buffered by snow cover. The Pacific coast of North America is an excellent test case, as mean winter temperatures are currently at the snow–rain threshold and have been warming for approximately 100 years post-Little Ice Age. Increased mortality in a widespread tree species in the region has been linked to warmer winters and snow loss. Here, we present the first high-resolution range map of this climate-sensitive species, Callitropsis nootkatensis (yellow-cedar), and document the magnitude and location of observed mortality across Canada and the United States. Snow cover loss related mortality spans approximately 10° latitude (half the native range of the species) and 7% of the overall species range and appears linked to this snow–rain transition across its range. Mortality is commonly >70% of basal area in affected areas, and more common where mean winter temperatures is at or above the snow–rain threshold (>0 °C mean winter temperature). Approximately 50% of areas with a currently suitable climate for the species (< 2 °C) are expected to warm beyond that threshold by the late 21st century. Regardless of climate change scenario, little of the range which is expected to remain suitable in the future (e.g., a climatic refugia) is in currently protected landscapes (<1–9%). These results are the first documentation of this type of emerging climate disturbance and highlight the difficulties of anticipating novel disturbance processes when planning for conservation and management.Ye

Longitudinal association between medication adherence and glycaemic control in Type 2 diabetes

Aim Despite the widespread assumption that adherence drives glycaemic control, there is little published support for this in Type 2 diabetes. The study objective was to determine whether self‐reported medication adherence predicts future glycaemic control in Type 2 diabetes, after accounting for baseline control. Methods Medication adherence (4‐item Morisky scale), glycaemic control (HbA 1c %), and other variables were assessed in 287 adult primary care patients prescribed oral medication (40% also on insulin) for Type 2 diabetes. Glycaemic control was reassessed 6 months later. Regression analyses examined concurrent and future glycaemic control as a function of baseline medication adherence after adjustment for baseline glycaemia and other potential confounders. Results Only half of patients reported high adherence. Cross‐sectional adjusted analysis replicated prior reports of an adherence‐HbA 1c association ( P  = 0.011). Even after adjusting for baseline HbA 1c , each one‐point increase in baseline Morisky total score was associated with a 1.8 mmol/mol (or 0.16%) increase in HbA 1c measured 6 months later. Additionally, baseline endorsement of forgetting to take medication was associated with a 4.7 mmol/mol (or 0.43%) increase in 6‐month HbA 1c ( P  = 0.005). This effect persisted after adjusting for psychological distress and did not vary by key demographic and medical features. Conclusions Even after stringent adjustment for baseline glycaemic control, self‐reported adherence to diabetes medication predicts long‐term glycaemic control. The Morisky scale is an easy‐to‐use clinical tool to identify patients whose glycaemic control will subsequently worsen, regardless of age, gender and psychological distress.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96675/1/dme12046.pd