Increasing evidence that thinning and burning treatments help restore understory plant communities in ponderosa pine forests

There is a general consensus that throughout their range, contemporary ponderosa pine forests exist outside of their natural range of variability in terms of overstory structure such as tree density (trees ac-1) and basal area (ft2 ac-1). As a result these ecosystems are increasingly susceptible to landscape-scale, high-intensity wildfires. Over the last century, a number of factors—particularly intensive livestock grazing, selective logging, and fire suppres- sion—have combined to favor pine establishment at the expense of understory diversity and productivity. This has given rise to uncharacteristically high tree densities with closed canopies, lower light availability, and deeper forest floor litter and duff layers (Covington and Moore 1994). A major consequence of this has been the degra- dation of understory integrity, including declines in understory cover, productivity, and diversity. Restoration techniques for mitigating these changes include mechanical thinning, prescribed fire, or a combina- tion of the two. Empirical studies assessing treatment success have shown that a combination of mechanical thin- ning plus prescribed fire is most successful at reaching overstory restoration targets (Fulé et al. 2002; Roccaforte et al. 2015). Yet consensus on meeting understory objectives remains mixed and few studies have defined quanti- tative targets to assess understory response (Laughlin et al. 2006). Therefore, developing more specific restoration objectives for the understory plant community represents an under-developed and challenging area of research. However, a primary goal of ecological restoration for understory plant response following treatments is to max- imize cover and diversity of native vegetation. Our first objective in this study was to evaluated understory response to alternative restoration treatments. We measured understory cover and species richness five years after treatments in the Mineral Ecosystem Manage- ment Area (Mineral) located in east-central Arizona and part of the Ecological Restoration Institute’s Long-term Ecological Assessment and Restoration Network (LEARN). An untreated control (Untreated) was used for com- parison of two alternative restoration treatments 1) thinning followed by prescribed fire (Thin + Burn) and 2) pre- scribed fire only (Burn-only). Our second objective was to compare the understory response patterns we observed at Mineral with those following similar treatments at other LEARN sites. To make comparisons we quantified a range of variability associated with understory cover and species richness to restoration using three comparison LEARN sites located in ponderosa pine forests of northern Arizona: Fort Valley (FV), Mount Trumbull (MT), and Grandview (GV). All three sites are located across a gradient of precipitation and soil types, representing a broad range of ponderosa pine forest types with characteristic differences in the contribution of species and func- tional groups to understory cover and diversity

Survival Rates Indicate that Correlations Between Community-Weighted Mean Traits and Environments can be Unreliable Estimates of the Adaptive Value of Traits

Correlations between community-weighted mean (CWM) traits and environmental gradients are often assumed to quantify the adaptive value of traits. We tested this assumption by comparing these correlations with models of survival probability using 46 perennial species from long-term permanent plots in pine forests of Arizona. Survival was modeled as a function of trait-by-environment interactions, plant size, climatic variation, and neighborhood competition. The effect of traits on survival depended on the environmental conditions, but the two statistical approaches were inconsistent. For example, CWM specific leaf area (SLA) and soil fertility were uncorrelated. However, survival was highest for species with low SLA in infertile soil, a result which agreed with expectations derived from the physiological tradeoff underpinning leaf economic theory. CWM trait-environment relationships were unreliable estimates of how traits affected survival, and should only be used in predictive models when there is empirical support for an evolutionary tradeoff that affects vital rates

Impact of the North Atlantic Oscillation on transatlantic flight routes and clear-air turbulence

The variation of wind-optimal transatlantic flight routes and their turbulence potential is investigated to understand how upper-level winds and large-scale flow patterns can affect the efficiency and safety of long-haul flights. In this study, the wind-optimal routes (WORs) that minimize the total flight time by considering wind variations are modeled for flights between John F. Kennedy International Airport (JFK) in New York, New York, and Heathrow Airport (LHR) in London, United Kingdom, during two distinct winter periods of abnormally high and low phases of North Atlantic Oscillation (NAO) teleconnection patterns. Eastbound WORs approximate the JFK–LHR great circle (GC) route following northerly shifted jets in the +NAO period. Those WORs deviate southward following southerly shifted jets during the −NAO period, because eastbound WORs fly closely to the prevailing westerly jets to maximize tailwinds. Westbound WORs, however, spread meridionally to avoid the jets near the GC in the +NAO period to minimize headwinds. In the −NAO period, westbound WORs are north of the GC because of the southerly shifted jets. Consequently, eastbound WORs are faster but have higher probabilities of encountering clear-air turbulence than westbound ones, because eastbound WORs are close to the jet streams, especially near the cyclonic shear side of the jets in the northern (southern) part of the GC in the +NAO (−NAO) period. This study suggests how predicted teleconnection weather patterns can be used for long-haul strategic flight planning, ultimately contributing to minimizing aviation’s impact on the environmen

The Economics of Debt Collection: Enforcement of Consumer Credit Contract,”

Abstract In the U.S., third-party debt collection agencies employ more than 140,000 people and recover more than $50 billion each year, mostly from consumers. Informational, legal, and other factors suggest that original creditors should have an advantage in collecting debts owed to them. Then, why does the debt collection industry exist and why is it so large? Explanations based on economies of scale or specialization cannot address many of the observed stylized facts. We develop an application of common agency theory that better explains those facts. The model explains how reliance on an unconcentrated industry of third-party debt collection agencies can implement an equilibrium with more intense collections activity than creditors would implement by themselves. We derive empirical implications for the nature of the debt collection market and the structure of the debt collection industry. A welfare analysis shows that, under certain conditions, an equilibrium in which creditors rely on third-party debt collectors can generate more credit supply and aggregate borrower surplus than an equilibrium where lenders collect debts owed to them on their own. There are, however, situations where the opposite is true. The model also suggests a number of policy instruments that may improve the functioning of the collections market

On the Stratospheric Chemistry of Midlatitude Wildfire Smoke

Massive Australian wildfires lofted smoke directly into the stratosphere in the austral summer of 2019/20. The smoke led to increases in optical extinction throughout the midlatitudes of the southern hemisphere that rivalled substantial volcanic perturbations. Previous studies have assumed that the smoke became coated with sulfuric acid and water and would deplete the ozone layer through heterogeneous chemistry on those surfaces, as is routinely observed following volcanic enhancements of the stratospheric sulfate layer. Here, observations of extinction and reactive nitrogen species from multiple independent satellites that sampled the smoke region are compared to one another and to model calculations. The data display a strong decrease in reactive nitrogen concentrations with increased aerosol extinction in the stratosphere, which is a known fingerprint for key heterogeneous chemistry on sulfate/H2O particles (specifically the hydrolysis of N2O5 to form HNO3). This chemical shift affects not only reactive nitrogen but also chlorine and reactive hydrogen species and is expected to cause midlatitude ozone layer depletion. Comparison of the model ozone to observations suggests that N2O5 hydrolysis contributed to reduced ozone, but additional chemical and/or dynamical processes are also important. These findings suggest that if wildfire smoke injection into the stratosphere increases sufficiently in frequency and magnitude as the world warms due to climate change, ozone recovery under the Montreal Protocol could be impeded, at least sporadically. Modeled austral midlatitude total ozone loss was about 1% in March 2020, which is significant compared to expected ozone recovery of about 1% per decade

Agency Problems and Risk Taking at Banks

Abstract The moral hazard problem associated with deposit insurance generates the potential for excessive risk taking on the part of bank owners. The banking literature identifies franchise value --a firm's profit-generating potential --as one force mitigating that risk taking. We argue that in the presence of owner/manager agency problems, managerial risk aversion may also offset the excessive risk taking that stems from moral hazard. Empirical models of bank risk tend to focus either on the disciplinary role of franchise value or on owner/manager agency problems. We estimate a unified model and find that both franchise value and ownership structure affect risk at banks. More important, we identify an interesting interaction effect: The relationship between ownership structure and risk is significant only at low franchise value banks --those where moral hazard problems are most severe and where conflicts between owner and manager risk preferences are therefore strongest. Risk is lower at banks with no insider holdings, but among other banks, there is no relationship between the level of insider holdings and risk. This suggests that the owner/manager agency problem affects the choice of risk for only a small number of banks --those with low franchise value and no insider holdings. Most of these banks increase their insider holdings within a year, and these changes in ownership structure are associated with increased risk. This suggests that owner/manager agency problems are quickly addressed.

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Ancient DNA Suggests Dwarf and ‘Giant’ Emu Are Conspecific

) is unclear. King Island Emu were mainly distinguished by their much smaller size and a reported darker colour compared to modern Emu. oxidase subunit I (COI) region (1,544 bp), as well as a region of the melanocortin 1 receptor gene (57 bp) were sequenced using a multiplex PCR approach. The results show that haplotypes for King Island Emu fall within the diversity of modern Emu.These data show the close relationship of these emu when compared to other congeneric bird species and indicate that the King Island and modern Emu share a recent common ancestor. King Island emu possibly underwent insular dwarfism as a result of phenotypic plasticity. The close relationship between the King Island and the modern Emu suggests it is most appropriate that the former should be considered a subspecies of the latter. Although both taxa show a close genetic relationship they differ drastically in size. This study also suggests that rates of morphological and neutral molecular evolution are decoupled