APPLICATION OF THE RHESSys MODEL TO A CALIFORNIA SEMIARID SHRUBLAND WATERSHED1

ABSTRACT: Distributed hydrologic models which link seasonal streamflow and soil moisture patterns with spatial patterns of vegetation are important tools for understanding the sensitivity of Mediterranean type ecosystems to future climate and land use change. RHESSys (Regional Hydro‐Ecologic Simulation System) is a coupled spatially distributed hydroecological model that is designed to be able to represent these feedbacks between hydrologic and vegetation carbon and nutrient cycling processes. However, RHESSys has not previously been applied to semiarid shrubland watersheds. In this study, the hydrologic submodel of RHESSys is evaluated by comparing model predictions of monthly and annual streamflow to stream gage data and by comparing RHESSys behavior to that of another hydrologic model of similar complexity, MIKESHE, for a 34 km² watershed near Santa Barbara, California. In model intercomparison, the differences in predictions of temporal patterns in streamflow, sensitivity of model predictions to calibration parameters and landscape representation, and differences in model estimates of soil moisture patterns are explored. Results from this study show that both models adequately predict seasonal patterns of streamflow response relative to observed data, but differ significantly in terms of estimates of soil moisture patterns and sensitivity of those patterns to the scale of landscape tessellation used to derive spatially distributed elements. This sensitivity has implications for implementing RHESSys as a tool to investigate interactions between hydrology and ecosystem processes.     

The prenatal diagnosis of joubert's syndrome of familial agenesis of the cerebellar vermis

The prenatal diagnosis by ultrasound examination of Joubert's syndrome of familial agenesis of the cerebellar vermis is described allowing termination of pregnancy ai 26 weeks gestation. The diagnosis was made by a comparison of the prenatal ultrasound examination with computerized axial tomography obtained from the siblings with the same condition.     

Amniotic fluid acetylcholinesterase measurements: Comparing immunochemical and polyacrylamide gel techniques

In the present study, a recently reported immunochemical technique for measuring acetylcholinesterase (AChE) in amniotic fluid utilizing the 4F19 antibody was compared with the widely utilized polyacrylamide gel technique to determine whether the immunochemical assay provided an advantage in separating unaffected pregnancies from those associated with open spina bifida (OSB) and open ventral wall defects (OVWD). The study included (1) 73 amniotic fluid samples from unaffected pregnancies [alpha-fetoprotein (AFP) < 2 MoM] with no visible gel AChE band, (2) nine bloodstained samples from unaffected pregnancies (AFP 2·2–4·0 MoM) with visible gel AChE bands, (3) 18 samples associated with OSB (AFP 2·2–7·0 MoM) with visible gel AChE bands, and (4) 20 samples associated with OVWD (AFP 3·2–53·5 MoM) with visible gel AChE bands. The immunochemical assay produced ranges of measurements in the four respective categories as follows: (1) 2–60 arbitrary units (AU): (2) 14–69 AU, (3) 61–593 AU, and (4)22–476 AU. Eight of the nine unaffected pregnancies with visible gel AChE bands had immunochemical measurements below the highest measurement for the samples with no visible AChE band (60 AU), as did five out of 20 OVWD pregnancies. Two of the OSB cases had values of 61 and 62 AU. These data indicate that the 4F19 specific monoclonal antibody to AChE is capable of distinguishing unaffected from affected pregnancies with reasonable reliability but that more work needs to be done to establish the extent of overlap between the unaffected and affected populations.     

Different modes of resource variation provide a critical test of ideal free distribution models

Ideal free distribution (IFD) models are perhaps the group of mathematical models of behavior that have been the most widely and successfully applied by empiricists. These models can be applied to nearly any situation in which consumers compete—by any mechanism—for resources that are patchily distributed in their environment. Although IFD models have come to be broadly accepted, experiments that simultaneously test more than a single prediction are rare. Instead, investigators normally either test (1) for a relationship between the distribution of consumers and the distribution of resources or (2) whether average fitnesses are equal across resource patches. We conducted experiments with pea aphids (Acyrthosiphon pisum Harris) feeding on two patches of fava beans (Vicia faba L.) to fully independently parameterize an IFD model with interference competition and then test quantitative predictions about aphid spatial distributions and the payoffs of patch choice. We found a precise fit between aphids’ predicted and observed reproductive successes. Furthermore, by varying patch “quality” in two ways, we were able to show that aphid distributions vary with the mode of resource variation in the predicted manner: aphids (1) matched resources when patches varied in size but not quality and (2) overmatched the good patch when patches varied in quality but not size (predicted as a consequence of weak interference). The close correspondence between quantitative predictions of the model with observed behaviors suggests that IFD theory is a framework with more explanatory power than is generally appreciated.     

Nitrogen inputs promote the spread of an invasive marsh grass.

Excess nutrient loading and large-scale invasion by nonnatives are two of the most pervasive and damaging threats to the biotic and economic integrity of our estuaries. Individually, these are potent forces, but it is important to consider their interactive impacts as well. In this study we investigated the potential limitation of a nonnative intertidal grass, Spartina alterniflora, by nitrogen (N) in estuaries of the western United States. Nitrogen fertilization experiments were conducted in three mud-flat habitats invaded by S. alterniflora in Willapa Bay, Washington, USA, that differed in sediment N. We carried out parallel experiments in San Francisco Bay, California, USA, in three habitats invaded by hybrid Spartina (S. alterniflora x S. foliosa), in previously unvegetated mud flat, and in native S. foliosa or Salicornia virginica marshes. We found similar aboveground biomass and growth rates between habitats and estuaries, but end-of-season belowground biomass was nearly five times greater in San Francisco Bay than in Willapa Bay. In Willapa Bay, aboveground biomass was significantly correlated with sediment N content. Addition of N significantly increased aboveground biomass, stem density, and the rate of spread into uninvaded habitat (as new stems per day) in virtually all habitats in both estuaries. Belowground biomass increased in Willapa Bay only, suggesting that belowground biomass is not N limited in San Francisco Bay due to species differences, N availability, or a latitudinal difference in the response of Spartina to N additions. The relative impact of added N was greater in Willapa Bay, the estuary with lower N inputs from the watershed, than in San Francisco Bay, a highly eutrophic estuary. Nitrogen fertilization also altered the competitive interaction between hybrid Spartina and Salicornia virginica in San Francisco Bay by increasing the density and biomass of the invader and decreasing the density of the native. There was no significant effect of N on the native, Spartina foliosa. Our results indicate that excess N loading to these ecosystems enhances the vulnerability of intertidal habitats to rapid invasion by nonnative Spartina sp.     

Amniotic fluid alpha-fetoprotein and acetylcholinesterase measurements in pregnancies associated with gastroschisis

In this study we define for the first time the distribution of alpha-fetoprotein levels and acetylcholinesterase ratios in amniotic fluid samples associated with fetal gastroschisis. Elevated alpha-fetoprotein levels and positive acetylcholinesterase measurements are found in virtually all cases, indicating that these combined measurements are highly reliable in detecting this lesion.     

Shoaling decisions in three-spined sticklebacks (<Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>)—familiarity,kinship and inbreeding

Shoaling with familiar kin is a well-known phenomenon. It has been described both for adult and for fry of three-spined sticklebacks (Gasterosteus aculeatus). However, evidence of preference for kin independent of familiarity is scarce. Furthermore, inbreeding effects have not been studied for shoaling preferences and there is a lack of studies about changes in individuals’ ability to recognise kin during different phases of life history. We gave inbred and outbred, nonreproductive sticklebacks of different age the choice to shoal with a group of familiar siblings vs unfamiliar non-siblings and with unfamiliar siblings vs unfamiliar non-siblings. Subadult sticklebacks preferred to shoal with familiar kin over unfamiliar non-kin, but inbred and outbred individuals had similar preferences. When given the choice between unfamiliar siblings and unfamiliar non-sibs, adult outbred fish preferred the shoal of kin, while inbred fish behaved indifferently. Body characteristics of the group such as body mass, standard length and condition of its members did not significantly explain the shoaling preferences for kin. Thus, sticklebacks were capable of recognising familiar and unfamiliar kin. The latter capability was lost by inbreeding.     

Glycerol as a green solvent for high product yields and selectivities

Organic synthesis is usually performed in solution to dissolve both reactants and catalysts and to deliver heat. Here, we show that glycerol, which is a non-toxic, biodegradable, and recyclable liquid manufactured from renewable sources, has a high potential to serve as alternative green solvent for organic reactions. Several catalytic and non-catalytic reactions were successfully performed in glycerol. High products yields and selectivities were achieved. Besides solubility of the reactants and the catalysts and easy separation of the product, glycerol offers several other benefits such as catalyst recycling, microwave assisting reaction, and biphasic and emulsion modes.     

Transferable discharge permits and economic efficiency: The fox river

Recent emphasis on reforms of environmental regulation has led to suggestions for strategies which maintain environmental standards but allow the needed flexibility and cost effectiveness. The transferable discharge permit (TDP) is one such strategy for water pollution control recently adopted in Wisconsin. In this article, the potential for substantial cost savings from trading TDPs is demonstrated using data on the Fox River in Wisconsin. A simulation model of water quality (Qual-III) and a linear programming model of abatement costs determine the optimum pattern of discharge. Reaching that optimum from proposed pollution abatement orders is shown to be feasible. Varying conditions of flow and temperature can be accommodated using trade coefficients which can be accurately estimated through interpolation. The calculations demonstrate the value and feasibility of flexible regulations governing water pollution abatement.