Projecting the impact of climate change on ungulate population dynamics: the importance of trophic interactions

Many projections of climate change impacts on ecological communities do not consider population dynamics or trophic interactions in species responses to climate. Therefore, they do not produce the estimates of population growth needed by wildlife managers. As herbivores, roe deer (Capreolus capreolus) are clearly affected by climate and by interactions with other trophic levels. They are dependent on vegetation for food and subject to predation by multiple species. Consequently, long-term datasets on this ungulate provide the opportunity to explore the importance of trophic interactions while estimating how population dynamics respond to changing climatic conditions. I used the relationship between temporal variation in climate and an index of net primary productivity to project increases in vegetation production for three study sites under future climate scenarios. Analyses of annual variation in the survival and reproductive rates of roe deer at two sites in Sweden demonstrated the importance of indirect effects of climate via changes in vegetation, in addition to the effects of predation and harvest on roe deer demography. Roe deer population growth in response to climate change was estimated using models incorporating both vegetation changes and vital rates into mechanistic simulations. These simulations highlighted the potential for climate change to increase deer population growth and for an increase in harvest and predation to reduce that growth. However, the uncertainty surrounding each level of these analyses was high. Additionally, an investigation of the factors affecting predation of roe deer by the wolf (Canis lupus) identified additional ecological complexities and sources of uncertainty that warrant consideration. This pervasive uncertainty indicates a need for cautious interpretation of results in this thesis, but also provides insight into priorities for future research. Collectively, these analyses demonstrate the theoretical and management value of taking a holistic and demographically explicit approach to estimating species responses to climate change

Volatility and Dispersion in Business Growth Rates: Publicly Traded versus Privately Held Firms

We study the variability of business growth rates in the U.S. private sector from 1976 onwards. To carry out our study, we exploit the recently developed Longitudinal Business Database (LBD), which contains annual observations on employment and payroll for all U.S. businesses. Our central finding is a large secular decline in the cross sectional dispersion of firm growth rates and in the average magnitude of firm level volatility. Measured the same way as in other recent research, the employment-weighted mean volatility of firm growth rates has declined by more than 40% since 1982. This result stands in sharp contrast to previous findings of rising volatility for publicly traded firms in COMPUSTAT data. We confirm the rise in volatility among publicly traded firms using the LBD, but we show that its impact is overwhelmed by declining volatility among privately held firms. This pattern holds in every major industry group. Employment shifts toward older businesses account for 27 percent or more of the volatility decline among privately held firms. Simple cohort effects that capture higher volatility among more recently listed firms account for most of the volatility rise among publicly traded firms.

COVID-19 Pandemic Impacts on Mammalian Carnivore Activity in the Eastern United States

Lockdowns and restrictions associated with the 2020 Covid-19 pandemic altered human activity, with potential impacts on wildlife. In particular, the activity of reclusive mammalian carnivores, which often avoid humans, may have been affected with ramifications for population connectivity and viability. Here, I evaluate changes in the capture rates of humans and mammalian carnivores between 2019 and 2020 across 31 sites in the Eastern United States. Site-specific capture records were obtained from the Snapshot USA camera trapping survey. Differences in carnivore activity were modelled as a response to human activity changes and the development level of the site (urban, suburban, rural or wild) using generalized linear models. Results indicated that, when compared with 2019, there was an overall decrease in human activity at camera sites in 2020, but human activity at urban and wild sites increased slightly. The mean capture rates of all carnivores examined did not change significantly between 2019 and 2020. Capture rates of all individually examined carnivore species varied significantly among development types, with most showing the lowest activity in urban areas. Of seven species modelled individually, only fisher (Martes pennanti) activity responded positively to decreases in human activity between years. Overall, with limited exceptions, changes in human activity caused by the COVID-19 pandemic may not have impacted mammalian carnivore activity as much as expected. This lack of a relationship with human activity could imply that some reclusive carnivore species make more use of human-occupied landscapes than was previously thought, but simply go undetected

Finding Cyclic Redundancy Check Polynomials for Multilevel Systems

This letter describes a technique for finding cyclic redundancy check polynomials for systems for transmission over symmetric channels which encode information in multiple voltage levels, so that the resulting redundancy check gives good error protection and is efficient to implement. The codes which we construct have a Hamming distance of 3 or 4. We discuss a way to reduce burst error in parallel transmissions and some tricks for efficient implementation of the shift register for these polynomials. We illustrate our techniques by discussing a particular example where the number of levels is 9, but they are applicable in general

New Families of Semi-Regular Relative Difference Sets

We give two constructions for semi-regular relative difference sets (RDSs) in groups whose order is not a prime power, where the order u of the forbidden subgroup is greater than 2. No such RDSs were previously known. We use examples from the first construction to produce semi-regular RDSs in groups whose order can contain more than two distinct prime factors. For u greater than 2 these are the first such RDSs, and for u = 2 we obtain new examples

Measuring the Dynamics of Young and Small Businesses: Integrating the Employer and Nonemployer Universes

We develop a preliminary version of an Integrated Longitudinal Business Database (ILBD) that combines administrative records and survey data for all employer and nonemployer business units in the United States. Unlike other large-scale business databases, the ILBD tracks business transitions from nonemployer to employer status. This feature of the ILBD opens a new frontier for the study of business formation, early lifecycle dynamics and the precursors to job creation in the U.S. economy. There are 5.4 million nonfarm business firms with employees as of 2000 and another 15.5 million with no employees. Our analysis focuses on 40 industries that account for nearly half of nonemployers and 36 percent of nonemployer revenues. Within these industries, nonemployers account for 14 percent of business revenues. About 220,000 of the seven million nonemployers in our selected industries hire workers and migrate to the employer universe over a three-year horizon. These Migrants account for 20 percent of revenue among young employers (three years or less since first hire). Compared to other nonemployers, the revenue of Migrants grows very rapidly in the year prior to and the year of transition to employer status.

Statistical Physics in Meteorology

Various aspects of modern statistical physics and meteorology can be tied together. The historical importance of the University of Wroclaw in the field of meteorology is first pointed out. Next, some basic difference about time and space scales between meteorology and climatology is outlined. The nature and role of clouds both from a geometric and thermal point of view are recalled. Recent studies of scaling laws for atmospheric variables are mentioned, like studies on cirrus ice content, brightness temperature, liquid water path fluctuations, cloud base height fluctuations, .... Technical time series analysis approaches based on modern statistical physics considerations are outlined.Comment: Short version of an invited paper at the XXIth Max Born symposium,Ladek Zdroj, Poland; Sept. 200