Competition for canopy space is a fundamental structuring feature of forest ecosystems and remains an enduring focus of research attention. We used a spatial neighborhood approach to quantify the ...influence of local competition on the size of individual tree crowns in north-central British Columbia, where forests are dominated by subalpine fir (
Abies lasiocarpa), lodgepole pine (
Pinus contorta) and interior spruce (
Picea glauca
×
engelmanii). Using maximum likelihood methods, we quantified crown radius and length as functions of tree size and competition, estimated by the species identity and spatial arrangement of neighboring trees. Tree crown size depended on tree bole size in all species. Given low levels of competition, pine displayed the widest, shortest tree crowns compared to the relatively long and narrow crowns found in spruce and fir. Sensitivity to crowding by neighbors declined with increasing tree height in all but the pine crown radius model. Five of the six selected best models included separate competition coefficients for each neighboring tree species, evidence that species generally differ in their competitive effects on neighboring tree crowns. The selected crown radius model for lodgepole pine, a shade-intolerant species, treated all neighbors as equivalent competitors. In all species, competition from neighbors exerted an important influence on crown size. Per-capita effects of competition across different sizes and species of neighbors and target trees varied, but subalpine fir generally displayed the strongest competitive effects on neighbors. Results from this study provide evidence that species differ both in their response to competition and in their competitive influence on neighbors, factors that may contribute to maintaining coexistence.
Social support (SS) is typically associated with lower emotional distress (e.g., stress and depression) in individuals. However, SS is a multifaceted construct that can vary by quality, quantity ...(amount), and type (i.e., it can be emotional or instrumental in nature).
The current study examined the relationships between characteristics of SS, stress, and depression in aging African Americans.
Analyses focused on data from 705 participants aged 22-92 years from the Carolina African American Twin Study of Aging.
Measures included the quality and quantity of emotional and instrumental support received, as well as stress and depression.
A series of univariate and increasingly complex multivariate regression models were conducted in MPlus (using the cluster option to control for family structure) to examine the relationships between SS and emotional distress variables.
Overall, better quality of emotional SS predicted fewer depression symptoms and less perceived stress, after controlling for age, gender, socioeconomic status variables, and the other subtypes of SS. However, more instances of emotional SS were associated with higher levels of perceived stress, depression symptoms, and more stressful life events within the past year. Likewise, more instrumental SS predicted more perceived stress, while holding the other variables constant.
African Americans who experience more emotional distress report more SS, but the quality of emotional support appears to play an important role in the association between reduced levels of stress and depression. These findings suggest that interventions should include approaches to reduce emotional distress as well as enhance the quality SS.
•Emotional, not instrumental, social support is directly associated with reduced daily drinking.•In African Americans, higher levels of depressed mood are associated with heavier daily smoking.•The ...protective effects of social support on daily smoking is mediated by negative emotionality.
The current study explored whether social support (SS) from family and peers, influences the relationship between depressed mood (DM) and substance use (SU). We hypothesized that SS would have a protective effect on DM, and moderate the association between DM and SU.
Analyses focused on 703 individuals from the Carolina African American Twin Study on Aging (mean age = 49.78 years, STD = 14.52; 51% female). Participants reported on past year frequency of cigarettes and alcohol consumption, depressed mood, and stressful life events. Social support (SS) was assessed on two domains (i.e., emotional and instrumental), as well as for perceived quality and quantity of each type. Hypotheses were tested using ordinal logistic regression in Mplus while controlling for socioeconomic status, age, and gender.
Quality of emotional support was negatively associated with drinking. Smoking, but not drinking was associated with depressed mood. While individuals with high levels of depressed mood received more support, receiving better quality emotional support was associated with fewer mood and stress symptoms. Individuals who reported receiving better quality emotional support typically smoked fewer cigarettes.
Quantity of emotional support was associated with higher levels of negative emotionality, whereas the opposite was found for quality of emotional support. Emotional support may indirectly influence smoking via depressed mood. Effecting the perceived quality of support appears to be the mechanism by which emotional support helps to reduce smoking in adult African Americans.
Evolved gas analysis (EGA) data from the Sample Analysis at Mars (SAM) instrument suite indicated Fe‐rich smectite, carbonate, oxidized organics, Fe/Mg sulfate, and chloride in sedimentary rocks from ...the Glen Torridon (GT) region of Gale crater that displayed phyllosilicate spectral signatures from orbit. SAM evolved H2O data indicated that the primary phyllosilicate in all GT samples was an Fe‐rich dioctahedral smectite (e.g., nontronite) with lesser amounts of a phyllosilicate such as mixed layer talc‐serpentine or greenalite‐minnesotaite. CO2 data supported the identification of siderite in several samples, and CO2 and CO data was also consistent with trace oxidized organic compounds such as oxalate salts. SO2 data indicated trace and/or amorphous Fe sulfates in all samples and one sample may contain Fe sulfides. SO2 data points to significant Mg sulfates in two samples, and lesser amounts in several other samples. A lack of evolved O2 indicated the absence of oxychlorine salts and Mn3+/Mn4+ oxides. The lack of, or very minor, evolved NO revealed absent or very trace nitrate/nitrite salts. HCl data suggested chloride salts in GT samples. Constraints from EGA data on mineralogy and chemistry indicated that the environmental history of GT involved alteration with fluids of variable redox potential, chemistry and pH under a range of fluid‐to‐rock ratio conditions. Several of the fluid episodes could have provided habitable environmental conditions and carbon would have been available to any past microbes though the lack of significant N could have been a limiting factor for microbial habitability in the GT region.
Plain Language Summary
The Mars Science Laboratory Curiosity rover carried out a comprehensive investigation of the sedimentary rocks in the Glen Torridon (GT) region in Gale crater, Mars, to better understand Martian geologic history. The rover’s Sample Analysis at Mars instrument suite was used to heat samples from GT and detect gases that were evolved to help identify the volatile‐bearing mineralogy of the samples. Results indicated the presence of Fe‐rich smectite, carbonate, oxidized organics, Fe and Mg sulfate, and chloride while oxychlorine salts, Mn3+/Mn4+ oxides, and nitrate/nitrite salts were either not detected or occurred in trace amounts. This mineralogy data implied that geochemical conditions and fluid‐to‐rock ratios varied over time and that the conditions of GT depositional and diagenetic environments would have been amenable to microbial life with sufficient carbon but nitrogen abundances could have been limiting.
Key Points
Sample Analysis at Mars data indicated Fe‐smectite, carbonate, oxidized organics, Fe/Mg sulfates, and chlorides in Glen Torridon (GT) rocks
GT’s environmental history involved fluids of variable redox potential and chemistry under a range of fluid‐to‐rock ratios
Fluid episodes could have provided habitable environments and carbon was present, but nitrogen could have been a limiting factor
Tree mortality is a critical driver of stand dynamics, influencing forest structure, composition, and capacity for ecosystem service provision. In recent years, tree mortality has been gaining ...attention as dramatic occurrences of forest die-off have been linked to climate change. Using permanent sample plot data, we examined tree mortality rates in mature forests in west-central Alberta from 1956 to 2007. We quantified mortality risk at an individual-tree level as a function of size, local competition, and calendar year, a proxy for increasing temperature, and used maximum likelihood methods to estimate species-specific model parameters. Tree size and local competition were both important predictors of mortality risk. However, once these factors were included in our model, no additional variation could be attributed to calendar year, indicating that the trend of increasing tree mortality over time found in our raw data is primarily a result of stand development processes. This finding is supported by the changes in forest structure and composition that we documented over the study period. Stands generally increased in basal area and stem density, and lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson) declined in abundance relative to the more shade-tolerant black spruce (Picea mariana (Mill.) B.S.P.) and white spruce (Picea glauca (Moench) Voss). Our results indicate that warming-related changes did not affect background tree mortality rates in mature forests in the Alberta foothills over the study period. These results also provide critical information for future studies of forest dynamics in the region.
Recently developed structural retention harvesting strategies aim to improve habitat and ecological services provided by managed forest stands by better emulating natural disturbances. The potential ...for elevated mortality of residual trees following such harvests remains a critical concern for forest managers, and may present a barrier to more widespread implementation of the approach. We used a harvest chronosequence combined with dendrochronological techniques and an individual-based neighborhood analysis to examine the rate and time course of residual-tree mortality in the first decade following operational partial "structural retention" harvests in the boreal forest of Ontario, Canada. In the first year after harvest, residual-tree mortality peaked at 12.6 times the preharvest rate. Subsequently, mortality declined rapidly and approached preharvest levels within 10 years. Proximity to skid trails was the most important predictor both of windthrow and standing death, which contributed roughly equally to total postharvest mortality. Local exposure further increased windthrow risk, while crowding enhanced the risk of standing mortality. Ten years after harvest, an average of 10.5% of residual trees had died as a result of elevated postharvest mortality. Predicted cumulative elevated mortality in the first decade after harvest ranged from 2.4% to 37% of residual trees across the observed gradient of skid trail proximity, indicating that postharvest mortality will remain at or below acceptable rates only if skidding impacts are minimized. These results represent an important step toward understanding how elevated mortality may influence stand dynamics and habitat supply following moderate-severity disturbances such as partial harvests, insect outbreaks, and windstorms.
THORPEX RESEARCH AND THE SCIENCE OF PREDICTION Parsons, D. B.; Beland, M.; Burridge, D. ...
Bulletin of the American Meteorological Society,
04/2017, Letnik:
98, Številka:
4
Journal Article
Recenzirano
Odprti dostop
The Observing System Research and Predictability Experiment (THORPEX) was a 10-yr, international research program organized by the World Meteorological Organization’s World Weather Research Program. ...THORPEX was motivated by the need to accelerate the rate of improvement in the accuracy of 1-day to 2-week forecasts of high-impact weather for the benefit of society, the economy, and the environment. THORPEX, which took place from 2005 to 2014, was the first major international program focusing on the advancement of global numerical weather prediction systems since the Global Atmospheric Research Program, which took place almost 40 years earlier, from 1967 through 1982. The scientific achievements of THORPEX were accomplished through bringing together scientists from operational centers, research laboratories, and the academic community to collaborate on research that would ultimately advance operational predictive skill. THORPEX included an unprecedented effort to make operational products readily accessible to the broader academic research community, with community efforts focused on problems where challenging science intersected with the potential to accelerate improvements in predictive skill. THORPEX also collaborated with other major programs to identify research areas of mutual interest, such as topics at the intersection of weather and climate. THORPEX research has 1) increased our knowledge of the global-to-regional influences on the initiation, evolution, and predictability of high-impact weather; 2) provided insight into how predictive skill depends on observing strategies and observing systems; 3) improved data assimilation and ensemble forecast systems; 4) advanced knowledge of high-impact weather associated with tropical and polar circulations and their interactions with midlatitude flows; and 5) expanded society’s use of weather information through applied and social science research.
Tendon injury is thought to involve both damage accumulation within the matrix and an accompanying cell response. While several studies have characterized cell and matrix response in chronically ...injured tendons, few have assessed the initial response of tendon to overload‐induced damage. In this study, we assessed cell response to cyclic loading. Fascicle bundles from the equine superficial digital flexor tendon were exposed to cyclic loading in vitro, designed to mimic a bout of high‐intensity exercise. Changes in cell morphology and protein‐level alterations in markers of matrix inflammation and degradation were investigated. Loading resulted in matrix damage, which was accompanied by cells becoming rounder. The inflammatory markers cyclooxygenase‐2 and interleukin‐6 were increased in loaded samples, as were matrix metalloproteinase‐13 and the collagen degradation marker C1,2C. These results indicate upregulation of inflammatory and degradative pathways in response to overload‐induced in vitro, which may be initiated by alterations in cell strain environment because of localized matrix damage. This provides important information regarding the initiation of tendinopathy, suggesting that inflammation may play an important role in the initial cell response to tendon damage. Full understanding of the early tenocyte response to matrix damage is critical in order to develop effective treatments for tendinopathy.
Variants of partial harvesting are gaining favour as means to balance ecosystem management and timber production objectives on managed boreal forest landscapes. Understanding how residual trees ...respond to these alternative silvicultural treatments is a critical step towards evaluating their potential from either a conservation or a wood supply perspective. We used dendroecological techniques combined with a chronosequence approach to quantify the temporal radial growth response pattern of residual black spruce (Picea mariana (Mill.) BSP) trees to partial harvest in northeastern Ontario. At its peak, 8-9 years after harvest, radial growth of residual trees had doubled. The growth pattern was characterized by a 2-year phase of no response, a subsequent period of increase 3-9 years after harvest, and a stage of declining rates 10-12 years after harvest. The magnitude of tree growth response depended strongly on tree age: peak postharvest growth was substantially higher for young trees, while old trees displayed only modest growth increases. Both the large magnitude and the time delay in postharvest growth responses have important implications for the development of more accurate quantitative tools to project future yields and, more generally, for determining whether partial harvesting is a viable management option for the boreal forest.
PDF
