Relationship between soil and groundwater salinity in the Western Canada Sedimentary Basin.

Saturated soil paste extracts indicate soluble ions in soil pore water that are available to vegetation. As such, they are thought to accurately describe the relationship between soil and groundwater salinity. To test this assumption, soil and groundwater samples were collected from 575 monitoring wells in saline regions of the Western Canadian Sedimentary Basin (WCSB). Samples were analyzed for electrical conductivity (EC) and Cl-, Na+, Ca2+, Mg2+, K+, SO42-, and HCO- 3 content. We compared groundwater ionic concentrations to paste extracts derived from matching soils, finding that differences from in situ soil porosity cause saturated pastes to underestimate groundwater salinity. Therefore, we provide pedotransfer functions for accurately calculating groundwater quality from soil data. In addition, we discuss the effects of porosity and soil composition on the saturated paste method, as measured through hydraulic conductivity, saturation percent, and sample lithology. Groundwater salinity may also influence further leaching of salts from soil. As produced water (NaCl brine) spills are common across the sulfate-rich soils of the WCSB, we considered the effects of NaCl on leaching of other ions, finding that influx of Na+ into groundwater is associated with increased sulfate leaching from soil. Therefore, considering the secondary effects of produced water on groundwater quality is essential to spill management.

Mathematical modeling of appendicular bone growth in glaucous-winged gulls.

Development of locomotor activity is crucial in tetrapods. In birds, this development leads to different functions for hindlimbs and forelimbs. The emergence of walking and flying as very different complex behavior patterns only weeks after hatching provides an interesting case study in animal development. We measured the diaphyseal lengths and midshaft diameters of three wing bones (humerus, ulna, and carpometacarpus) and three leg bones (femur, tibiotarsus, and tarsometatarsus) of 79 juvenile (ages 0-42 days) and 13 adult glaucous-winged gulls (Larus glaucescens), a semiprecocial species. From a suite of nine alternative mathematical models, we used information-theoretic criteria to determine the best model(s) for length and diameter of each bone as a function of age; that is, we determined the model(s) that obtained the best tradeoff between the minimized sum of squared residuals and the number of parameters used to fit the model. The Janoschek and Holling III models best described bone growth, with at least one of these models yielding an R(2) > or = 0.94 for every dimension except tarsometatarsus diameter (R(2) = 0.87). We used the best growth models to construct accurate allometric comparisons of the bones. Early maximal absolute growth rates characterize the humerus, femur, and tarsometatarsus, bones that assume adult-type support functions relatively early during juvenile development. Leg bone lengths exhibit more rapid but less sustained relative growth than wing bone lengths. Wing bone diameters are initially smaller than leg bone diameters, although this relationship is reversed by fledging. Wing bones and the femur approach adult length by fledging but continue to increase in diameter past fledging; the tibiotarsus and tarsometatarsus approach both adult length and diameter by fledging. In short, the pattern of bone growth in this semiprecocial species reflects the changing behavioral needs of the developing organism.