Answering one question often begets another. We present a decision-theoretic model that describes how this affects the sequencing of decisions over time. Because answering an easy question may raise a more difficult one, a rational judge may delay resolution even if he has perfect information about the correct decision. Furthermore, because otherwise unrelated questions may raise similar follow-ups, he may optimally clump decisions together. Our theory thus generates an endogenous economy of scale in dispute resolution and contributes to the literature on punctuated equilibrium theory. We illustrate the results of our model with a case study from legal history in the United States.

Proglacial lakes, formed during retreat of the Laurentide ice sheet, evolved quickly as outlets became ice-free and the earth deformed through glacial isostatic adjustment. With high-resolution digital elevation models (DEMs) and GIS methods, it is possible to reconstruct the evolution of surface hydrology. When a DEM deforms through time as predicted by our model of viscoelastic earth relaxation, the entire surface hydrologic system with its lakes, outlets, shorelines and rivers also evolves without requiring assumptions of outlet position. The method is applied to proglacial Lake Oshkosh in Wisconsin (13,600 to 12,900 cal yr BP). Comparison of predicted to observed shoreline tilt indicates the ice sheet was about 400 m thick over the Great Lakes region. During ice sheet recession, each of the five outlets are predicted to uplift more than 100 m and then subside approximately 30 m. At its maximum extent, Lake Oshkosh covered 6600 km2 with a volume of 111 km3. Using the Hydrologic Engineering Center-River Analysis System model, flow velocities during glacial outburst floods up to 9 m/s and peak discharge of 140,000 m3/s are predicted, which could drain 33.5 km3 of lake water in 10 days and transport boulders up to 3 m in diameter.

Background: Sellar masses (SM) are mostly benign growths of pituitary or nonpituitary origin that are increasingly encountered in clinical practice. To date, no comprehensive population-based study has reported the epidemiology of SM from North America. Aim: To determine the epidemiology of SM in the province of Nova Scotia, Canada. Methods: Data from all pituitary-related referrals within the province were prospectively collected in interlinked computerized registries starting in November 2005. We conducted a retrospective analysis on all patients with SM seen within the province between November 2005 and December 2013. Results: A total of 1107 patients were identified, of which 1005 were alive and residing within the province. The mean age at presentation was 44.6±18 years, with an overall female preponderance (62%) and a population prevalence rate of 0.1%. Of patients with SM, 837 (83%) had pituitary adenomas and 168 (17%) had nonpituitary lesions. The relative prevalence and standardized incidence ratio, respectively, of various SM were: nonfunctioning adenomas (38.4%; 2.34), prolactinomas (34.3%; 2.22), Rathke’s cyst (6.5%; 0.5), growth hormone–secreting adenomas (6.5%; 0.3), craniopharyngiomas (4.5%; 0.2), adrenocorticotropic hormone–secreting adenomas (3.8%; 0.2), meningiomas (1.9%), and others (3.9%; 0.21). At presentation, 526 (52.3%) had masses ≥1 cm, 318 (31.6%) at <1 cm, and 11 (1.1%) had functioning pituitary adenomas without discernible tumor, whereas tumor size data were unavailable in 150 (14.9%) patients. The specific pathologies and their most common presenting features were: nonfunctioning adenoma (incidental, headaches, and vision loss), prolactinomas (galactorrhea, menstrual irregularity, and headache), growth hormone–secreting adenomas (enlarging extremities and sweating), adrenocorticotropic hormone-secreting adenoma (easy bruising, muscle wasting, and weight gain) and nonpituitary lesions (incidental, headaches, and vision problems). Secondary hormonal deficiencies were common, ranging from 19.6% to 65.7%; secondary hypogonadism, hypothyroidism, and growth hormone deficiencies constituted the majority of these abnormalities. Conclusions: This is the largest North American study to date to assess the epidemiology of SM in a large stable population. Given their significant prevalence in the general population, more studies are needed to evaluate the natural history of these masses and to help allocate appropriate resources for their management.

In this study, we investigated whether landscape-scale variation of soil P accounts for 13C and 15N composition of detrital invertebrates in a lowland tropical rain forest in Costa Rica. The top 10-cm soil, leaf-litter samples and plant foliage were collected among 18 plots representing a three-fold soil P gradient during 2007–2009. Body tissue of litter invertebrates (extracted from leaf-litter samples) along with soil, leaf litter and green foliage were analysed for total C, total N, δ13C and δ15N values. Differences in δ13C and δ15N signatures across plots and relative trophic distances of detrital food webs (Δ δ15N), and their variation with soil P gradient were evaluated. We found soil P gradient had a significantly positive correlation with δ15N of Asterogyne martiana foliage, leaf litter, collembolans and oribatid mites. The δ15N of the collembolans and pseudoscorpions positively correlated to leaf-litter δ15N. Δ δ15N between the trophic levels remained consistent across the soil P gradient. Higher δ15N in the collembolans and oribatid mites might be derived from their consumption on 15N-enriched decayed debris or fungal hyphae growing on it. It suggests that fine-scale soil P variation can affect trophic dynamics of detrital arthropods via regulation of microbial community and nutrient dynamics.

Relations between crown width and tree height and trunk diameter and tree height were measured for trees of all sizes of six large emergent species (Balizia elegans, Dipteryx panamensis, Hieronyma alchorneoides, Hymenolobium mesoamericanum, Lecythis ampla and Terminalia oblonga) in the lowland tropical wet forest at La Selva, Costa Rica. Thirty to 45 individuals were chosen per species to provide a relatively even height distribution from 1 m up to the maximum encountered height. Among small juveniles, the crown widths of the two species with the smallest leaves and horizontally spreading branches were greater than those of the four large-leaved species. On reaching and exceeding the canopy, all but one species showed pronounced increases in crown width with increasing height. These patterns are linked to leaf size and first branching height in small juveniles and low densities of emergent trees at La Selva and other tropical forests, where crown expansion in all directions enhances light interception under the equatorial sun in trees that are not crowded by neighbours of similar height.

We evaluated occurrence and abundance of lianas and woody hemiepiphytes on canopy and emergent tree species in primary tropical wet forest at the La Selva Biological Station, Costa Rica. Two pioneers, Cecropia obtusifolia and C. insignis, lacked both lianas and hemiepiphytes. The seven non-pioneer species differed significantly in their loads of lianas and hemiepiphytes. For all non-pioneer species, two measures of liana and hemiepiphyte loads (the percentage of the crown occupied and the combined basal area of descending hemiepiphyte and liana roots and stems) increased significantly with tree diameter. In all non-pioneer species, most trees ∵ 70 cm diameter (50–97%) were colonized. Lianas occupied more trees and had a smaller mean host diameter than did hemiepiphytes; however, basal area of descending roots or stems was equivalent for the two life forms in occupied trees. We used partial correlations controlling for tree diameter to evaluate the relationship between annual tree diameter growth and loads of hemiepiphytes and lianas for six non-pioneer species. Five of the six species showed a significant negative correlation between loads and diameter growth. Existing published data show that the high incidence of lianas and hemiepiphytes at La Selva is paralleled in most other Neotropical wet forests.

Light environment, leaf physiological characteristics, and growth were compared for forest-grown saplings of three species of tropical trees with known life histories. Light environment was assessed both by hemispherical canopy photography and a quantitative visual index of crown illumination. Leaf gas exchange characteristics were measured by infrared gas analysis. The species tested included Lecythis ampla, a species tolerant of understorey conditions, Pithecellobium elegans, a species found in relatively bright sites, and Simarouba amara, a fast-growing, light-demanding species.

Annual height and diameter growth did not significantly differ between the three species, but highest average rates were found for Simarouba. Likewise, saplings of the three species were found in similar low light environments although Simarouba saplings were found in slightly brighter sites and Lecythis saplings were found in the lowest light environments. Despite similar light regimes, the species differed markedly in leaf area and gas exchange. Leaf areas of Lecythis saplings were five and ten-fold greater than Simarouba and Pithecellobium saplings, respectively. Light-saturated leaf photosynthesis and leaf dark respiration rates of Lecythis were about half those of Simarouba; rates of Pithecellobium were intermediate. Lecythis had the highest leaf photosynthesis at understorey diffuse light levels. Measures of annual growth were positively correlated with estimates of both direct and diffuse light with the strongest correlations between sapling performance and diffuse light.

Estimation of tree growth is generally based on repeated diameter measurements. A buttress at the height of measurement will lead to overestimates of tree diameter. Because buttresses grow up the trunk through time, it has become common practice to increase the height of measurement, to ensure that measurements remain above the buttress. However, tapering of the trunk means that increasing measurement height will bias estimates of diameter downward by up to 10% per m of height. This bias could affect inference concerning species differences and climate effects on tree demography and on biomass accumulation. Here we introduce a hierarchical state space method that allows formal integration of data on diameter taken at different heights and can include individual variation, temporal effects or other covariates. We illustrate our approach using species from Barro Colorado Island, Panama, and La Selva, Costa Rica. Results include trends that are consistent with some of those previously reported for climate responses and changes over time, but differ in relative magnitude. By including the full data-set and accounting for bias and variation among individuals and over time, our approach allows for quantification of climate responses and the uncertainty associated with measurements and the underlying growth process.