Keeping the Board in the Dark: CEO Compensation and Entrenchment

We study a model in which a CEO can entrench himself by hiding information from the board that would allow the board to conclude that he should be replaced. Assuming that even diligent monitoring by the board cannot fully overcome the information asymmetry visà- vis the CEO, we ask if there is a role for CEO compensation to mitigate the inefficiency. Our analysis points to a novel argument for high-powered, non-linear CEO compensation such as bonus pay or stock options. By shifting the CEO’s compensation into states where the firm’s value is highest, a high-powered compensation scheme makes it as unattractive as possible for the CEO to entrench himself when he expects that the firm’s future value under his management and strategy is low. This, in turn, minimizes the severance pay needed to induce the CEO not to entrench himself, thereby minimizing the CEO’s informational rents. Amongst other things, our model suggests how deregulation and technological changes in the 1980s and 1990s might have contributed to the rise in CEO pay and turnover over the same period

An experimental assessment of active and passive dispersal of red snow algae on the Harding Icefield, southcentral Alaska

Red snow algae seasonally color glacier and alpine snow surfaces with characteristic red blooms. These blooms significantly reduce the albedo of the snow surface resulting in increased snow ablation. The global cryosphere is sensitive to the melt effect of expansive reoccurring blooms; however, the primary dispersal path by which snow algae seasonally recolonize snow surfaces is currently unresolved. Using an experimental field approach that inhibited resurfacing populations with a physical barrier, then sampled algal surface abundance the following growing season, we assessed two pathways of algal surface colonization on the Harding Icefield, Alaska. Our results provide the first experimental depiction of active resurfacing as the primary pathway of seasonal snow surface colonization by red snow algae above the equilibrium line elevation on an Alaskan glacier. Results suggest that, at the peak of the growing season, 65 percent of surface abundance was derived from actively resurfacing cells and 35 percent from passively dispersing cells

Species turnover in ant assemblages is greater horizontally than vertically in the world's tallest tropical forest.

Abiotic and biotic factors structure species assembly in ecosystems both horizontally and vertically. However, the way community composition changes along comparable horizontal and vertical distances in complex three-dimensional habitats, and the factors driving these patterns, remains poorly understood. By sampling ant assemblages at comparable vertical and horizontal spatial scales in a tropical rainforest, we tested hypotheses that predicted differences in vertical and horizontal turnover explained by different drivers in vertical and horizontal space. These drivers included environmental filtering, such as microclimate (temperature, humidity, and photosynthetic photon flux density) and microhabitat connectivity (leaf area), which are structured differently across vertical and horizontal space. We found that both ant abundance and richness decreased significantly with increasing vertical height. Although the dissimilarity between ant assemblages increased with vertical distance, indicating a clear distance-decay pattern, the dissimilarity was higher horizontally where it appeared independent of distance. The pronounced horizontal and vertical structuring of ant assemblages across short distances is likely explained by a combination of microclimate and microhabitat connectivity. Our results demonstrate the importance of considering three-dimensional spatial variation in local assemblages and reveal how highly diverse communities can be supported by complex habitats

Sequence composition diversity in Alaskan glacier and other metagenomes

Abstract Metagenomics by next generation sequencing has become an important tool for interrogating complex microbial communities. In this study we analyzed several pairs of metagenomic samples obtained by different methods and observed biases, resulting in different nucleotide composition of the sequenced reads. The pairwise sample comparison was based on the principal component analysis of dinucleotide word frequencies in sequences obtained from different platforms. We found bias in the sequences obtained from the different platforms for the amplified hypervariable regions in 16S rRNA but not in shotgun metagenome reads aligned to such hypervariable regions. The differences and consistency of the distributions of the nucleotides suggest that the biases are likely due to a combination of biases introduced by PCR and different sequencing protocols, and they are related to the GC content of the reads produced. For this reason, caution should be exercised when interpreting the results of comparative metagenomics studies, as they may vary depending on the sequencing technology

Historical Biogeography Of The North American Glacier Ice Worm, Mesenchytraeus Solifugus (annelida: Oligochaeta: Enchytraeidae)

North American ice worms are the largest glacially-obligate metazoans, inhabiting coastal, temperate glaciers between southcentral Alaska and Oregon. We have collected ice worm specimens from 10 new populations, completing a broad survey throughout their geographic range. Phylogenetic analyses of 87 individuals using fragments of nuclear 18S rRNA, and mitochondrial 12S rRNA and cyctochrome c oxidase subunit 1 (CO1) identified 18 CO1 haplotypes with divergence values up to similar to 10%. Phylogeographic interpretations suggest a St. Elias Range, Alaskan ancestry from an aquatic mesenchytraeid oligochaete during the early-Pliocene. A gradual, northward expansion by active dispersal from the central St. Elias clade characterizes a northern clade that is confined to Alaska (with one exception on Vancouver Island, British Columbia), while a distinct southern clade representing worms from British Columbia, Washington and Oregon was likely founded by a passive dispersal event originating from a northern ancestor. The geographic boundary between central and southern clades coincides with an ice worm distribution gap located in southern Alaska, which appears to have restricted active gene flow throughout the species\u27 evolutionary history

Data from: Thermal segregation drives patterns of alder and willow expansion in a montane ecosystem subject to climate warming

1.Tall-shrub expansion into low-statured communities, a hallmark of recent vegetative change across tundra ecosystems, involves three major genera: Alnus, Betula, and Salix. Which genus expands most into tundra landscapes will determine ecosystem properties. 2.We show that Alnus and Salix shrubs segregate thermal space (elevation x insolation) and colonize tundra landscapes differently in response to climate warming, thereby replacing different tundra types. 3.Vegetative change estimated from repeat photography should account for hill-slope. Methodologically, slope determines surface area estimated from orthophotos as projected pixel area times secant of pixel slope. Ecologically, the change in thermally-responsive vegetative area is sensitive to terrain steepness, scaling as the cosecant of hill-slope, so that studies should expect more shrub expansion in areas of shallow slopes than steep slopes. 4.Repeat aerial photography in Alaska's Chugach Mountains from 1972-2012 orthorectified on high-resolution lidar DEM indicated tall Salix was rare in 1972 and colonized warmer slopes by 2012. Tall Alnus colonized steeper, cooler slopes both by 2012 and by 1972. Salix and forest colonized similar thermal space. Colonization probability for both shrub genera was maximized at intermediate elevations. 5.Alnus colonization adjacent to dwarf-shrub tundra was twenty-times as likely as Salix colonization. Salix colonization adjacent to low-shrub/herbaceous tundra was three-times as likely as Alnus colonization. Replacement of dwarf-shrub tundra by Alnus and of low-shrub/herbaceous communities by Salix will affect herbivores and soil properties. 6.Good agreement between observations of plant functional type and multinomial predictions in a thermal space defined by elevation and insolation suggested that these two variables were sufficient for forecast modeling. Spatially explicit, climate-driven GLM multinomial and random forest classification models in available thermal space forecast surface areas of forest, Alnus, Salix, and tundra over a range of warming, modeled as upward shifted isotherms, including expected IPCC scenarios. Both modeling approaches indicated that shrubs may respond non-linearly to warming. 7.Synthesis The provision of taxon-specific coefficients for climate-driven, spatially-explicit models using high resolution digital elevation models is necessary for accurately forecasting vegetative change due to climate warming in montane and arctic regions

Soil pit moisture data

Soil pits with location and moisture content. This file has the location data for temperature data loggers listed in the file Soil Temperature data file

VegClass

VegClass is an ArcMap version 10.4.1 shapefile of polygon-features (SpatialPolygonsDataFramein R) with four attributes giving the “Subarea” of the study area, the area in ha (“area_ha”) of the polygon-feature, the functional class of the polygon in 1972 (“Veg1972”), and the functional class of the polygon in 2012 (“Veg2012”). Projection is UTM zone6 with datum of WGS84. Please see VegClass_README.rtf for further details

Soil Temperature Data

Soil temperatures at 15 cm for up to one year. The samples were blocked by location for up to three vegetation classes (alder, willow, and tundra) but unbalanced

2000 random points for statistical modeling

2000 random points across the three study sub-areas were selected for statistical modeling in binomial generalized linear mixed models. These points have digital elevation model (DEM) variables (elevation, slope, aspect, potential insolation in four seasons) and vegetation classifications for 1972 and 2012