Tripartite association in alder: effects of Frankia and Alpova piplophloes on the growth, nitrogen fixation, and mineral acquisition of Alnus tenuifolia. Plant and Soil

Abstract The role of tripartite associations among Frankia, Alpova diplophloeus (an ectomycorrhizal fungus) and Alnus tenuifoliain growth, nitrogen fixation, ectomycorrhizal formation, and mineral acquisition of A. tenuifolia was investigated. Seedlings of A. tenuifolia were planted in pots containing a mixture of ground basalt-perlite, or perlite alone, which served as the control. The seedlings were inoculated with Frankia isolated from root nodules of alder, followed by spores of A. diplophloeus and grown for 5 months in a greenhouse. The seedlings grown in the pots with a mixture of ground basalt-perlite after dual inoculation with Frankia and A. diplophLoeus had the heaviest shoots and root nodules in dry weight, and showed the greatest nitrogen-fixing ability measured by acetylene reduction. Ectomycorrhizas formed with A. diplophloeus increased when this fungus was inoculated together with Frankia. The mineral composition (P, K, Ca, Fe, Mg, Mn, Na, Si and Al) in the seedlings was also determined. The results of these experiments showed that the tripartite association could improve the growth, nitrogen fixation and mineral acquisition (rock solubilization) of A. tenuifolia

Forest Structure Affects Soil Mercury Losses in the Presence and Absence of Wildfire

Soil is an important, dynamic component of regional and global mercury (Hg) cycles. This study evaluated how changes in forest soil Hg masses caused by atmospheric deposition and wildfire are affected by forest structure. Pre and postfire soil Hg measurements were made over two decades on replicate experimental units of three prefire forest structures (mature unthinned, mature thinned, clear-cut) in Douglas-fir dominated forest of southwestern Oregon. In the absence of wildfire, O-horizon Hg decreased by 60% during the 14 years after clearcutting, possibly the result of decreased atmospheric deposition due to the smaller-stature vegetative canopy; in contrast, no change was observed in mature unthinned and thinned forest. Wildfire decreased O-horizon Hg by >88% across all forest structures and decreased mineral-soil (0 to 66 mm depth) Hg by 50% in thinned forest and clear-cut. The wildfire-associated soil Hg loss was positively related to the amount of surface fine wood that burned during the fire, the proportion of area that burned at >700 °C, fire severity as indicated by tree mortality, and soil C loss. Loss of soil Hg due to the 200 000 ha wildfire was more than four times the annual atmospheric Hg emissions from human activities in Oregon

Postwildfire Soil Trajectory Linked to Prefire Ecosystem Structure in Douglas-Fir Forest

Changes in soil C and N pools following wildfire are quite varied, but there is little understanding of the causes of the variation. We examined how the legacies of prefire ecosystem structure may explain the variation in soil trajectories during the first decade following wildfire. Five years prior to wildfire in a southwestern Oregon forest dominated by mature Douglas-fir [Pseudotsuga menziesii var. menziesii (Mirb.) Franco], ecosystem structure was experimentally manipulated by thinning or clearcutting for comparison with unthinned forest. Repeated measurements of replicated experimental units were made before wildfire and during the first decade following wildfire. In the unthinned forest, the O-horizon soil C and N pools were decreased to 24–39% of prefire levels by wildfire, then increased to 53–70% during the first year postwildfire by deposition of fire-killed needles from overstory trees. The mineral soil (0–6 cm depth) C pool was decreased by wildfire, then increased in the following decade, while no change in the N pool was detected. In contrast, in the clearcut treatment, the O-horizon soil C and N pools were nearly totally consumed during the wildfire, lacked fire-killed overstory as a source of needle and fine and coarse wood inputs, but regained 20% of prefire masses in the following decade via foliar and root inputs from regenerated shrubs and herbaceous vegetation. Surface mineral soil C and N pools were decreased 35–50% by wildfire and showed no sign of recovery during the following decade. In contrast to wildfire, unburned ecosystem structures showed no changes in O horizon and increased mineral-soil N pool in the clearcut. We propose a conceptual model of soil C and N response following wildfire that includes legacy influences resulting from prefire ecosystem structures: residual live trees that generate continual litterfall and root turnover; fire-killed trees that produce needle-fall, dead roots, and fine- and coarse-wood detritus; and surviving roots and burls that contribute to postwildfire shrub regeneration. Consideration of prefire ecosystem structure and legacies in quantitative models may improve forecasts of postwildfire C budgets at stand to regional scales.Keywords: legacy, soil nitrogen, fine woody debris, soil carbon, postwildfire change, forest management, wildfir

Managing early succession for biodiversity and long-term productivity of conifer forests in southwestern Oregon

Early-successional stages have been truncated and altered in many western U.S. forest landscapes by planting conifers, controlling competing vegetation, suppressing fire, and focusing on maintaining late-seral species and undisturbed riparian zones. Declining area of early-successional stages may be reducing resilience and sustainability on landscapes that experience elevated disturbance related to future climate changes. In this study, two post-harvest early-successional treatments were compared to each other and to two mature-forest treatments using 20 years of evidence from replicated 7-ha experimental units in a southwestern Oregon forest dominated by Douglas-fir (Pseudotsuga menziesii Mirb. Franco). One early-successional treatment (Douglas-fir plantation) planted Douglas-fir and was followed by a brushing to reduce hardwood competition to move quickly to the conifer stem-exclusion stage; the other (Early-seral plantation) favored natural sprouting and regeneration of hardwood shrubs and trees and planted scattered knobcone pines (Pinus attenuata Lemmon) and Douglas-fir. Plant diversity in the Early-seral plantation was 56% (year 2) and 26% (year 6) higher than in the Douglas-fir plantation. Both early-successional treatments far exceeded plant diversity in Unaltered and Thinned mature stands. Fifteen years of growth of shrubs and hardwood trees in the Early-seral plantation was remarkable, resulting in total aboveground biomass increment (18 Mg ha⁻¹ yr⁻¹) double that of the Douglas-fir plantations. Important process effects related to primary productivity were noted: losses of soil organic matter from the B horizon in young Douglas-fir, and, after wildfire, increases in N₂-fixing plant cover in Early-seral plantation. The burl-sprouting and deep rooting of many hardwoods also created opportunities for nutrient retention and release from primary minerals as well as deep-profile water supply. Recognizing the importance of intentionally managing for shrubs and hardwood trees is particularly relevant at this site, because stand reconstruction and historical records indicate these species, along with knobcone pine, dominated the site for 40 years before the current mature Douglas-fir forest started gaining dominance. In contrast, the prolific natural regeneration of Douglas-fir after recent harvest and wildfire suggests that what comes back ‘‘naturally’’ in modern times will not allow this history to be repeated.Keywords: N₂ fixation, Early-seral, Long-term productivity, Biodiversity, Early successionKeywords: N₂ fixation, Early-seral, Long-term productivity, Biodiversity, Early successio

Dynamics of Hot Bulk QCD Matter: from the Quark-Gluon Plasma to Hadronic Freeze-Out

We introduce a combined macroscopic/microscopic transport approach employing relativistic hydrodynamics for the early, dense, deconfined stage of the reaction and a microscopic non-equilibrium model for the later hadronic stage where the equilibrium assumptions are not valid anymore. Within this approach we study the dynamics of hot, bulk QCD matter, which is expected to be created in ultra-relativistic heavy ion collisions at the SPS, the RHIC and the LHC. Our approach is capable of self-consistently calculating the freeze-out of the hadronic system, while accounting for the collective flow on the hadronization hypersurface generated by the QGP expansion. In particular, we perform a detailed analysis of the reaction dynamics, hadronic freeze-out, and transverse flow.Comment: 55 pages, 15 figure

A global experiment on motivating social distancing during the COVID-19 pandemic

Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e., a controlling message) compared with no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared with the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing. Controlled motivation was associated with more defiance and less long-term behavioral intention to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges

A global experiment on motivating social distancing during the COVID-19 pandemic

Significance Communicating in ways that motivate engagement in social distancing remains a critical global public health priority during the COVID-19 pandemic. This study tested motivational qualities of messages about social distancing (those that promoted choice and agency vs. those that were forceful and shaming) in 25,718 people in 89 countries. The autonomy-supportive message decreased feelings of defying social distancing recommendations relative to the controlling message, and the controlling message increased controlled motivation, a less effective form of motivation, relative to no message. Message type did not impact intentions to socially distance, but people’s existing motivations were related to intentions. Findings were generalizable across a geographically diverse sample and may inform public health communication strategies in this and future global health emergencies. Abstract Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e., a controlling message) compared with no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared with the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing. Controlled motivation was associated with more defiance and less long-term behavioral intention to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges

A global experiment on motivating social distancing during the COVID-19 pandemic

Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e. a controlling message) compared to no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly-internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared to the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly-internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing: Controlled motivation was associated with more defiance and less long-term behavioral intentions to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges

Stand density in young red alder plantations : production, photosynthate partitioning, nitrogen fixation, and an optimal initial spacing model

Dimension analysis, acetylene reduction and canopy structure measurements were used to evaluate the relationship between density and dry weight production, nitrogen (N₂) fixation and photosynthate partitioning (as indicated by dimension analysis) in 5-year-old red alder (Alnus rubra Bong.) plantations established at three initial spacings. Density strongly affected most dry weight components and N₂ fixation. Low density stands (9 x 9 ft initial spacing) had the highest values per tree for all measured weight, volume, and surface area components and N₂ fixation. Mid-density stands (4 x 6 ft initial spacing) had the highest per unit area values for leaf weight, canopy volume, branch weight and surface area, root and stump weight, net branch production, aboveground net production and N₂ fixation. The highest density stands (2 x 4 ft initial spacing) had the highest values per unit area of the variables:wood volume, bole and total aboveground dry weight and net bole production. Nodule weight per unit area was approximately equal in the mid- and high-density stands averaging 146 kg/ha. Correlation coefficients for dimension analysis were high (eg. leaf wt.: r =0.952; branch wt.: r =0.963; bole wt.: r =0.995; root wt.: r =0.971; nodule wt.: r =0.931). Stand density, as an independent variable, improved the correlation coefficient for many of these equations, indicating that density strongly affected photosynthate partitioning. The high correlation between per tree N₂ fixation and leaf weight (r =0.892) supports the hypothesis of Gordon and Wheeler (1978). Leaf weight and N₂ fixation per unit area (averaging 2.15 metric tons/ha and 70 kgha⁻¹yr⁻¹, respectively), however, were not highly correlated suggesting that less photosynthate was allocated to nodules in high density stands. Component net production to total aboveground net production ratios changed with density also suggesting that density strongly affects photosynthate allocation patterns. Crown structure related well to observed allocation patterns: a higher proportion of leaves close to the ground corresponded to higher N₂ fixation rates per tree. An optimal spacing model is proposed that may eventually aid in economic evaluation of alder plantation designs and rotations. The model predicts optimal spacings for wood products (pulpwood, sawlogs) and uses variables that are physiologically tied to competition-linked processes (live-crown-ratio, crown volume and leaf density). Estimated spacing for sawlogs is similar to that predicted in the literature but projected pulpwood spacing appears too close. Assumed live-crown-ratio seems to have the greatest effect on projected spacing but crown shape and leaf density are also important. It may be possible to modify the model to produce estimates of alder yield under management. Thus, it could aid in an economic evaluation of alder investment opportunities. Additional research, especially on live-crown-ratios, is needed before this model can be widely used