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Research on retention in the 4-H youth development program has consistently shown that one of the primary indicators for youths' dropping out of 4-H is being a first-year member. Extension 4-H professionals from California, Idaho, Wyoming, and New Jersey formed a team to study this issue. Our team surveyed first-year members and their parents/guardians to better understand why youths were not reenrolling in 4-H after their first year. This article introduces the survey used to assess the first-year experience and intent to reenroll. We discuss the survey development process, survey testing, lessons learned, and conclusions related to its future use.

The prediction of snowmelt in mountainous forests strongly depends on the accurate description of sensible and latent heat turbulent fluxes. Uncertainty about the within‐canopy wind conditions especially poses a challenge, with relatively few studies examining both above‐ and below‐canopy turbulent fluxes. In this study, turbulent flux predictions from a state‐of‐the‐art watershed model GEOtop were verified against eddy covariance data from one above‐canopy tower and two below‐canopy towers in a snow‐dominated coniferous forest in south‐eastern Wyoming. The model was applied in one‐dimensional vertical mode using field‐observed vegetation parameters and laboratory‐measured soil water retention data. The model was calibrated by identifying optimum values for the canopy fraction and the within‐canopy eddy decay coefficient using the brute‐force method. Above‐canopy sensible heat flux at the Glacier Lakes Ecosystem Experiments Site was predicted reasonably well (r2 =.851). The prediction of above‐canopy latent heat flux was weaker (r2 =.426). For latent heat flux, errors in 30‐min values offset each other when fluxes were aggregated over time, resulting in realistic mean diurnal trends. Below‐canopy turbulent flux at two sites in the Libby Creek Experimental Watershed were predicted with variable success with r2 =.031–.146 for sensible heat flux and r2 =.445–.581 for latent heat flux. Modelled below‐canopy sensible heat flux was too low due to the underestimation of daytime ground surface temperature, because of not enough solar radiation reaching the soil surface. This study suggests that future work on GEOtop and related models should include better parameterizations of the ground surface energy balance to more reliably predict snowmelt and streamflow from mountainous forests. [ABSTRACT FROM AUTHOR]

Questions Do the spectral patterns recorded by Landsat Thematic Mapper ( TM) for various sagebrush species differ from each other? Could ancillary data derived from topographic variables (elevation, slope and aspect) strengthen the relationship between sagebrush and spectral characteristics? Location Rawlins, Wyoming, USA. Methods Field data on sagebrush species and structural characteristics collected in 2005 were regressed against spectral values and transformed indices derived from Landsat TM data. Step-wise regression methods were used to build (1) a combined model that ignored species and physical differences in sagebrush, and (2) four different models that took those differences in account. Parsimonious models were selected with significant independent variables that accounted for the largest amount of the ground-measured variation in cover. Results In the combined model, a subset of Landsat bands and topographic values accounted for 65% ( P < 0.001) of variance in sagebrush canopy cover. However, when separate regression models were fitted based on species type (big and low sagebrush) and height (for big sagebrush only), Landsat data accounted for 71-85% ( P < 0.001) of the ground measured variance. Conclusions Spectral patterns of sagebrush species and their physical characteristics were distinguishable with Landsat TM data. Transformed indices derived from Landsat data accounted for more variance than the original spectral bands. Future research should focus on testing the relationship between Landsat TM data and sites where sagebrush is present with other vegetation to facilitate landscape and regional mapping of changing sagebrush ecosystems. [ABSTRACT FROM AUTHOR]

To quantify the relationship between temporal and spatial variation in tree transpiration, we measured sap flow in 129 trees with constant-heat sap flow sensors in a subalpine forest in southern Wyoming, USA. The forest stand was located along a soil water gradient from a stream side to near the top of a ridge. The stand was dominated by Pinus contorta Dougl. ex Loud. with Picea engelmannii Parry ex Engelm and Abies lasiocarpa (Hook.) Nutt. present near the stream and scattered individuals of Populus tremuloides Michx. throughout the stand. We used a cyclic sampling design that maximized spatial information with a minimum number of samples for semivariogram analyses. All species exhibited previously established responses to environmental variables in which the dominant driver was a saturating response to vapor pressure deficit (D). This response to D is predictable from tree hydraulic theory in which stomatal conductance declines as D increases to prevent excessive cavitation. The degree to which stomatal conductance declines with D is dependent on both species and individual tree physiology and increases the variability in transpiration as D increases. We quantified this variability spatially by calculating the spatial autocorrelation within 0.2-kPa D bins. Across 11 bins of D, spatial autocorrelation in individual tree transpiration was inversely correlated to D and dropped from 45 to 20 m. Spatial autocorrelation was much less for transpiration per unit leaf area and not significant for transpiration per unit sapwood area suggesting that spatial autocorrelation within a particular D bin could be explained by tree size. Future research should focus on the mechanisms underlying tree size spatial variability, and the potentially broad applicability of the inverse relationship between D and spatial autocorrelation in tree transpiration. [ABSTRACT FROM AUTHOR]

Abstract: Sonic thermometry and anemometry are fundamental to all eddy-covariance studies of surface energy balance. Recent studies have suggested that sonic anemometers with non-orthogonal transducers can underestimate vertical wind velocity (w) and sensible heat flux (H) when compared to orthogonal designs. In this study we tested whether a non-orthogonal sonic anemometer (CSAT3, Campbell Scientific, Inc.) measures lower w and H than an orthogonal sonic anemometer (SATI/3Vx, Applied Technologies, Inc.) and through experimental manipulation we tested if this difference can be attributed to errors in the CSAT3. Four CSAT3s and one SATI/3Vx were mounted symmetrically in a horizontal array on top of the Glacier Lakes Ecosystem Experiments Site (GLEES) AmeriFlux scaffold (southeastern Wyoming, USA) and in close enough proximity to allow covariance measurements between neighboring sonic anemometers. The CSAT3s were paired and measurements of the three orthogonal wind velocities (u, v, and w) were tested by alternatively rotating each sonic anemometer 90° around its u-axis, essentially forcing the sonic v-axis transducer system to measure w. Analysis was performed on data corresponding to gusts of wind located within the 15° cone defined around the u-axis to ensure operation within manufacturer specifications. We found that the CSAT3 measured 8% lower H than the SATI/3Vx and that was associated with a 6–12% lower measurement of w. From the CSAT3 manipulations we found w was underestimated by 6–10% which led directly to an 8–12% underestimate of the kinematic heat flux, the fundamental covariance of H. These results have implications for ecosystem flux research and the energy imbalance problem considering the prevalence of the CSAT3 and the non-orthogonal sonic anemometer design. [Copyright &y& Elsevier]