Report on Sediment Transport Events on Shelf and Slope (STRESS) field season 1 : Winter 1988-1989 Benthic Acoustic Stress Sensor (BASS)

Data on the effects of winter conditions on the transport of sediment on the continental shelf off Northern California were collected during the flrst year of the Sediment TRansport Events on Shelf and Slope (STRESS) Experiment. This experiment was done in conjunction with (Shelf Mixed Layer Experiment) SMILE and (Biological Effects on Coastal Ocean Sediment Transport) BECOST to provide a complete suite of measurements of nearshore dynamics, sediment transport, and biological interactions. This report includes a general description of the work accomplished during the frrst STRESS fleld season, carried out in the winter of 1988-1989 off the Northern California coast Three cruises were completed during the STRESS experiment, one each for deployment, turnaround, and r~overy of the instruments. This created two back-to-back sections of data, one from December 4, 1988 to January 23, 1989, and the other from January 29 to March 17, 1989. This report also documents in detail the use of the Benthic Acoustic Stress Sensor (BASS), and the associated acoustic data telemetry link in STRESS. BASS has been used in different configurations previously, but the acoustic telemetry system is new.Funding was provided by the Office of Naval Research under Contract No. N000-14-89-J-105

Mixed-Severity Fire Effects on Biological Legacies and Vegetation Response in Pseudotsuga Forests of Western Oregon's Central Cascades, USA

Mixed-severity fire occurrence is increasingly recognized in Pseudotsuga forests of the Pacific Northwest, but questions remain about how tree mortality varies, and forest structure is altered, across the disturbance gradient observed in these fires. Therefore, we sampled live and dead biological legacies at 45 one ha plots, with four 0.10 ha nested plots, stratified across an unburned, low, moderate and high-severity fire gradient. We used severity estimates based on differenced Normalized Burn Ratio (dNBR), and captured a disturbance gradient, but plots in our low-severity class underestimated fire effects because of misclassification or delayed mortality. We estimated probability of mortality for shade-intolerant (Douglas-fir, incense-cedar, sugar pine) and shade-tolerant (western hemlock, western redcedar, true fir) trees from 5,079 sampled trees and snags. The probability of mortality was higher for shade-tolerant species across all fire-severity classes, and decreased with increasing DBH except for western hemlock. Only large, shade-intolerant trees survived high-severity fire. Post-fire snag fall and fragmentation were estimated from 2,746 sampled snags and logs. The probability of snag fall decreased with increasing DBH for all species, and was positively correlated with fire severity, except for Douglas-fir that had a higher probability following low-severity fire. Snag fragmentation was positively correlated with DBH and fire severity for all species. We also estimated the coefficient of variation within- and among-plots by fire severity class, as well as across all sampled conditions. Structural attributes varied more within- than among-plots, likely a result of increasing sub-hectare patchy mortality as fire intensity increased. Although vertical and horizontal structural diversity increased at sub-hectare scales, the coefficient of variation was highest for all structural attributes when compared across all fire severity classes. Therefore, the range of fire effects observed in mixed-severity fires may be functionally important in creating structural complexity across landscapes, which is an important attribute of old-growth forests in the Pacific Northwest. Understory vegetation response to mixed-severity fires has not been characterized for these forests even though the majority of vegetation diversity is found in these vegetation layers. Therefore, we sampled forest structure (1000 m² circular plots) and understory vegetation (100 m² plots) at 168 collocated plots stratified across unburned, low, moderate and high-severity conditions 10 years (Tiller Complex) and 22 years (Warner Fire) post-fire. We focused on shrub species, but sampled forbs, graminoids, ferns and moss as functional groups. Offsite colonization and fire stimulated soil seedbanks increased the total species richness from 23 to 46. The life-history strategies of residual and colonizing species resulted in three dominant species response-curves to the magnitude of disturbance: 1) 'disturbance-sensitive', when relative abundance was highest in unburned plots and continued to decline with increasing fire severity, 2) 'disturbance-stimulated', when relative abundance was highest following low or moderate-severity fire and 3) 'disturbance-amplified', when relative abundance increased with increasing fire severity. Residual and colonizing species assemblages promoted five or six distinct understory communities, dominantly driven by legacy tree basal area rather than the proportion of basal area killed. Understory communities were rarely associated with one disturbance severity class as fire refugia, variation in overstory and understory fire severity, and compensatory conditions offset fire effects. Early-seral habitats were the most different from unburned forests, but were not the only post-fire conditions important across these burned landscapes. Interactions among live and dead forest structures following low or moderate-severity fire, and the vegetation response to these conditions, are also unique to the post-fire landscape and likely important for various wildlife species. Therefore, if ecological forestry paradigms focus dominantly on creating old-growth structure or early-seral habitats, they might exclude important conditions that contribute to the landscape structural complexity created by mixed-severity fires. Additionally, tree regeneration response to mixed-severity fires has not been characterized for these forests even though they offer insight into one aspect of the resilience of these ecosystems to disturbance. Therefore, we sampled forest structure (1000 m² circular plots) and regeneration dynamics (100 m² plots) at 168 collocated plots stratified across unburned, low, moderate and high-severity conditions 10 years (Tiller Complex) and 22 years (Warner Fire) post-fire. The largest marginal increase in tree mortality (stems ha⁻¹) occurred between unburned and low-severity fires, given preferential mortality of small trees and shade-tolerant species, but basal area mortality had the largest marginal increase moving from moderate to high-severity. Pairwise comparisons of legacy tree basal area between low and moderate-severity weren’t as significant as other comparisons, but did capture a gradient of increasing fire effects. Quadratic mean diameter and canopy base height were positively correlated with fire severity as incrementally larger trees were killed and canopy ascension followed. Regeneration density increased regardless of severity, relative to unburned forests (median density of 1,384 trees ha⁻¹), but the highest median density (16,220 trees ha⁻¹) followed low-severity fire at the Tiller Complex and moderate-severity fire (14,472 trees ha⁻¹) at Warner Fire. Plot-level average species richness was highest following these same fire severity classes, supporting the Intermediate Disturbance Hypothesis. Statistically distinct regeneration communities occurred across the fire severity gradient at both fire sites. The relative abundance of shade-tolerant tree species decreased as fire severity increased, except for a divergent response following stand-initiation at the Warner Fire. While divergent successional pathways were evident within a couple decades following stand-initiation, low or moderate-severity fires also modified successional trajectories and may be the most functionally important disturbance magnitude because it has the greatest potential to increase compositional and structural diversity. Incorporating mixed-severity fire effects into landscape management of Pseudotsuga forests could increase structural complexity at stand and landscape-scales.Keywords: biological legacies, fire ecology, wildland fire, Douglas-fir, mixed-severity fire, snag dynamics, forest succession, post-fire regenerationKeywords: biological legacies, fire ecology, wildland fire, Douglas-fir, mixed-severity fire, snag dynamics, forest succession, post-fire regeneratio

Coarse woody detritus dynamics, variable decay rates and their contribution to wildland fuel succession following high-severity fire disturbance in dry-mixed conifer forests of Oregon's eastern Cascades

Reducing future fire severity is a proposed ecological benefit of salvage logging following wildfire disturbance. Considerable debate continues over the ability of such management practices to achieve this objective given limited understanding of coarse woody detritus (CWD) dynamics, fuel bed alterations, and post-fire vegetative growth. The objective of this study was to estimate the dynamics of snags and logs in conjunction with surface fuel accumulation following high-severity fire disturbance in dry-mixed conifer forests of Oregon’s eastern Cascades. Snag dynamics (fall and breakage rates) were estimated for Abies sp., Pinus ponderosa and Pinus contorta in three DBH classes of 41 cm (large). A total of 5,103 snags in thirty 0.25-ha plots were sampled at seven different fire sites, covering a 24 year chronosequence following high-severity fire disturbance. Pinus ponderosa and Pinus contorta snags had the quickest fall rates with estimated half-lives of 7-8 and 12-13 years for small and medium sized snags, respectively. Large Pinus ponderosa snags had an estimated half-life of 17-18 years. Abies sp. snags fall rates were slower, with half-life estimates of 8-9, 14-15 and 20-21 years for small, medium and large snags respectively. Breakage rates were variable but correlated with wood strength, crown and stem weight and crown position (exposure to wind). Decomposition loss rate-constants were obtained from the same fire sites, up to seven years post-fire, by removing three cross-sections from each of sixty fire-killed Abies sp. snags, sixty Pinus ponderosa snags, and forty Pinus ponderosa logs. Abies sp. snags exhibited significant decay with an estimated decomposition loss rate-constant of k = 0.0149 yr⁻¹. Pinus ponderosa snags did not exhibit significant decay, but logs did. Sapwood and heartwood decomposition loss rate-constants equaled k = 0.0362 yr⁻¹ and k = 0.0164 yr⁻¹, respectively. These values confirm hypothesized differences in decay rates among species and between snags and logs in dry forest environments. An empirical model was developed to link snag fall and breakage with snag and log decomposition during succession in order to estimate the contribution of fire killed biological legacies to fine and coarse woody detritus accumulation. Legacy CWD is responsible for the largest total accumulation of surface fuel as snags break and fall, but primarily in 100- and 1000-hr fuel classes. Decomposition rates increase as CWD moves from standing to downed material, reducing total CWD biomass by 30-50% in 24 years. Fine fuels are primarily derived from post-fire vegetation and steadily increase over the 24-year period. Herbaceous fuel loads peak within 2-4 years but decrease rapidly as Ceanothus velutinus and Arctostaphylos patula shrubs establish quickly and steadily increase in total biomass over 24 years. Spread rates and flame lengths in post-fire environments are primarily driven by fuels generated from new growth. The dynamic process of snag fall and breakage, and decomposition of snags and logs, limits CWD's effect on fire spread and intensity if reburning occurs, although soil heating and total heat release can be exacerbated by the combustion of decayed logs. Salvage logging significantly reduces CWD fuels but has limited impacts on other fuel bed components. Results of this study suggest post-fire management decisions consider vegetation dynamics as well as dead wood dynamics if reducing fire hazard is a primary objective

Evaluation of thermal evaporation conditions used in coating aluminum on near-field fiber-optic probes

This is the published version, also available here: http://dx.doi.org/10.1063/1.1148836.The effects that the thermal evaporation conditions have on the roughness of aluminum-coated near-field fiber-optic probes were investigated using the high-resolution capabilities of atomic force microscopy. The coating conditions studied include the effects of background gas composition, base vacuum pressure, and aluminum evaporation rate. The effects of aging on the aluminum-coated tips were also evaluated. The results from topography measurements of the resulting aluminumfilm indicated that the most dramatic improvements in the tip coatings can be achieved using high aluminum evaporation rates at base vacuum pressures below 10−5 Torr. These results agree with other studies on thin aluminumfilms and reflect a decrease in oxide formation. For demanding applications of near-field microscopy requiring maximal resolution, the results presented here indicate that it may also be necessary to reduce oxygen and/or water from the vacuum chamber prior to coating

An Existential-Humanistic View of Personality Change: Co-Occurring Changes with Psychological Well-Being in a 10 Year Cohort Study

Increasingly, psychological research has indicated that an individual’s personality changes across the lifespan. We aim to better understand personality change by examining if personality change is linked to striving towards fulfilment, as suggested by existential–humanistic theories of personality dynamics. Using the Wisconsin Longitudinal Study, a cohort of 4,733 mid-life individuals across 10years, we show that personality change was significantly associated with change in existential well-being, represented by psychological well-being (PWB). Moreover, personality change was more strongly related to change in PWB than changes in other well-being indicators such as depression, hostility and life satisfaction. Personality changed to a similar degree and explained greater variation in our well-being measures than changes in socioeconomic variables. The findings indicate personality change is necessary for the holistic development of an individual, supporting a greater need to understand personality change and increasing room for use of personality measures as indicators of well-being and policy making

Effects of two contrasting canopy manipulations on growth and water use of London plane (Platanus x acerifolia) trees

Aims: Two contrasting canopy manipulations were compared to unpruned controls on London plane trees, to determine the effects on canopy regrowth, soil and leaf water relations. Methods: ‘Canopy reduction’, was achieved by removing the outer 30 % length of all major branches and ‘canopy thinning’, by removing 30 % of lateral branches arising from major branches. Results: Total canopy leaf areas recovered within two and three years of pruning for the canopy-thinned and reduced trees respectively. Canopy reduction increased mean leaf size, nitrogen concentration, canopy leaf area density and conserved soil moisture for up to 3 years, whereas canopy thinning had no effects. Another experiment compared more severe canopy reduction to unpruned trees. This produced a similar growth response to the previous experiment, but soil moisture was conserved nearer to the trunk. Analysis of 13C and 18O signals along with leaf water relations and soil moisture data suggested that lower boundary layer conductance within the canopy-reduced trees restricted tree water use, whereas for the canopy-thinned trees the opposite occurred. Conclusions: Only canopy reduction conserved soil moisture and this was due to a combination of reduced total canopy leaf area and structural changes in canopy architecture

Probing single molecule orientations in model lipid membranes with near-field scanning optical microscopy

This is the published version, also available here: http://dx.doi.org/10.1063/1.481367.Single molecule near-field fluorescence measurements are utilized to characterize the molecular level structure in Langmuir–Blodgett monolayers of L-α-dipalmitoylphosphatidylcholine (DPPC).Monolayers incorporating 3×10−4 mol % of the fluorescent lipid analog N-(6-tetramethylrhodaminethiocarbamoyl)-1,2-dihexadecanoyl-sn- glycero-3-phosphoethanolamine, triethylammonium salt (TRITC–DHPE) are transferred onto a freshly cleaved mica surface at low (π=8 mN/m) and high (π=30 mN/m)surfacepressures. The near-field fluorescence images exhibit shapes in the single molecule images that are indicative of the lipid analog probe orientation within the films. Modeling the fluorescence patterns yields the single molecule tilt angle distribution in the monolayers which indicates that the majority of the molecules are aligned with their absorption dipole moment pointed approximately normal to the membrane plane. Histograms of the data indicate that the average orientation of the absorption dipole moment is 2.2° (σ=4.8°) in monolayers transferred at π=8 mN/m and 2.4° (σ=5.0°) for monolayers transferred at π=30 mN/m. There is no statistical difference in the mean tilt angle or distribution for the two monolayer conditions studied. The insensitivity of tilt angle to filmsurfacepressure may arise from small chromophore doped domains of trapped liquid-expanded lipid phase remaining at high surfacepressure. There is no evidence in the near-field fluorescence images for probe molecules oriented with their dipole moment aligned parallel with the membrane plane. We do, however, find a small but significant population of probe molecules (∼13%) with tilt angles greater than 16°. Comparison of the simultaneously collected near-field fluorescence and force images suggests that these large angle orientations are not the result of significant defects in the films. Instead, this small population may represent a secondary insertion geometry for the probe molecule into the lipidmonolayer