When asked to report the color of a target letter in a briefly presented word or pseudoword, Ss were more likely to report the color of letters from the same syllablelike unit than the color of other letters. Because Ss were not required to make a lexical decision or naming response, the multiletter units that are revealed by this task arise automatically. It was found that the syllablelike units are not phonological but correspond to orthographic patterns and morphemes. These units affect performance regardless of changes in letter-case, suggesting that the units are based on abstract letter identities. Unit formation was also not affected by visual field of presentation. Several experiments demonstrated that the morphological and orthographic units arise from different processes: The morphological units depend on lexical access, and the orthographic units do not. Finally, the effects of orthography are stronger for good readers than for poor readers.

[1] Aeolian transport is an important characteristic of many arid and semiarid regions worldwide that affects dust emission and ecosystem processes. The purpose of this paper is to evaluate a recent model of aeolian transport in the presence of vegetation. This approach differs from previous models by accounting for how vegetation affects the distribution of shear velocity on the surface rather than merely calculating the average effect of vegetation on surface shear velocity or simply using empirical relationships. Vegetation, soil, and meteorological data at 65 field sites with measurements of horizontal aeolian flux were collected from the Western United States. Measured fluxes were tested against modeled values to evaluate model performance, to obtain a set of optimum model parameters, and to estimate the uncertainty in these parameters. The same field data were used to model horizontal aeolian flux using three other schemes. Our results show that the model can predict horizontal aeolian flux with an approximate relative error of 2.1 and that further empirical corrections can reduce the approximate relative error to 1.0. The level of error is within what would be expected given uncertainties in threshold shear velocity and wind speed at our sites. The model outperforms the alternative schemes both in terms of approximate relative error and the number of sites at which threshold shear velocity was exceeded. These results lend support to an understanding of the physics of aeolian transport in which (1) vegetation's impact on transport is dependent upon the distribution of vegetation rather than merely its average lateral cover and (2) vegetation impacts surface shear stress locally by depressing it in the immediate lee of plants rather than by changing the bulk surface's threshold shear velocity. Our results also suggest that threshold shear velocity is exceeded more than might be estimated by single measurements of threshold shear stress and roughness length commonly associated with vegetated surfaces, highlighting the variation of threshold shear velocity with space and time in real landscapes. n number of field sites P d (x/h) probability that a point on the landscape is distance from the nearest upwind plant measured as x/h P U probability distribution of wind speeds, U, during measurement period P u à probability distribution of wind shear velocity, u * , during measurement period et al., 1997b]

Beryllium‐7 is a potentially powerful tracer of atmospheric deposition and recent sediment transport, but the quantity and distribution of 7Be on arid landscapes have not been described. We measured 7Be in soil, vegetation, and dust in Owens Valley, California, and describe its distribution in aridisols and mollisols to evaluate its potential as a sediment tracer in desert environments. Beryllium‐7 in vegetation and the upper few cm of soil is low but detectable (>20 Becquerels [Bq] m−2). Surface inventories of 7Be at sites on the valley floor vary by a factor of five between the end of the rainy season (April) and the end of the dry season (November). In mollisols, live grasses hold ∼50 Bq 7Be m−2, which is on the order of half of the total springtime surface inventory. We find that within‐site variability at the 5 m scale is 5 to 22% (1 relative standard error) and can be explained by localized rain shadowing and erosion, but between site variability at the km scale can be explained by differences in rainfall. Our alpine site has more than triple the inventory that is predicted from the rainfall‐7Be flux relationship that we generate using our springtime soil measurements and previously reported deposition data. Dust deposition does not appear to contribute significantly to 7Be inventories, but anomalously high 7Be on the eastern flank of the Sierras may be explained by a higher altitude air mass source and better scavenging efficiency of snow.

[1] Wind erosion is a significant environmental problem that removes soil resources from sensitive ecosystems and contributes to air pollution. In regions of shallow groundwater, friable (puffy) soils are maintained through capillary action, surface evaporation of solute-rich soil moisture, and protection from mobilization by groundwater-dependent grasses and shrubs. When a reduction in vegetation cover occurs through any disturbance process, there is potential for aeolian transport and dust emission. We find that as mean gap size between vegetation elements scaled by vegetation height increases, total horizontal aeolian sediment flux increases and explains 58% of the variation in total horizontal aeolian sediment flux. We also test a probabilistic model of wind erosion based on gap size between vegetation elements scaled by vegetation height (the Okin model), which predicts measured total horizontal aeolian sediment flux more closely than another commonly used model based on the average plant area observed in profile (Raupach model). The threshold shear velocity of bare soil appears to increase as gap size between vegetation elements scaled by vegetation height increases, reflecting either surface armoring or reduced interaction between the groundwater capillary zone and surface sediments. This work advances understanding of the importance of measuring gap size between vegetation elements scaled by vegetation height for empirically estimating Q and for structuring process-based models of desert wind erosion in groundwater-dependent vegetation.Citation: Vest, K. R., A. J. Elmore, J. M. Kaste, G. S. Okin, and J. Li (2013), Estimating total horizontal aeolian flux within shrub-invaded groundwater-dependent meadows using empirical and mechanistic models,

To calculate total 137 Cs atmospheric fluxes to each site we used direct measurements of atmospheric fallout collected by the Department of Energy during 1956-1972 (US ERDA, 1977) and monthly precipitation at each site calculated by the PRISM Climate Group, Oregon State University. Detailed records of weapons-derived 90 Sr wet deposition fluxes (Bq m-2) per cm of rainfall were collected in Alabama, U.S.A. during the weapons testing era which we use to extrapolate total fluxes for each site's