Quantifying Soil and Groundwater Chemistry in Areas Invaded by Tamarix spp. Along the Middle Rio Grande, New Mexico

Tamarix spp. (a.k.a. saltcedar, tamarisk) invasion is considered a major ecological threat at both national and global levels, with supposed impacts on soil and water chemistry. One of the most often cited mechanisms of ecosystem change by Tamarix is through its ability to deposit salty exudates and salt-rich leaf litter. The degree to which Tamarix relates to elevated soil and groundwater salinity, however, has not been adequately quantified, especially in the context of environmental factors that may also influence salinity. If Tamarix does elevate localized salinity by means of uptake, concentration and exudation by plant tissues, then we might expect that the magnitude of its impact would be influenced by stand features such as density and age. Therefore, we analyzed soil and groundwater salinity associated with Tamarix stands across a gradient of densities and aboveground ages along an arid reach of the Middle Rio Grande in Central New Mexico. Stands were sampled both in areas exposed to and deprived of flooding to account for potential hydrologic impacts on soil and groundwater chemistry. Paired soil samples were collected underneath Tamarix canopies and in adjacent open areas to compare solute concentrations associated with Tamarix cover to those in soils exposed to greater rates of surface evaporation. Results indicate that flooding may be the most important factor for assessing floodplain salinity as the presence of this flushing mechanism was related to the lowest salt levels. Surface soil salinity was observed to increase with greater Tamarix stem diameter (a predictor of age) in areas deprived of flooding; however a hyperbolic pattern where salt level is highest under intermediate-aged growth and lowest underneath younger and older canopies seems to better explain the variability associated with salt level change by age. Tamarix density was not observed to influence soil salinity, but higher densities were associated with elevated groundwater salinity in flood-suppressed areas. Soils under Tamarix canopies had lower surface soil salinity than open areas deprived of flooding suggesting that surface evaporation may contribute more to surface soil salinity than Tamarix or may exacerbate contributions by leaf exudates. This research provides a unique opportunity to quantify the degree to which an invasive species can alter its environment. Results can be used to guide management decisions related to native species revegetation of Tamarix-invaded areas

Perceptions of Effectiveness of School Counselors with Former Graduates in a TRIO College Program

The context and variables that affect at-risk students are constantly changing. It is imperative that school counselors understand the risk factors for students and the cultural and social contexts the individual lives within. Working with at-risk students is even more challenging with the millennial generation. The culture in this generation promotes instant gratification as society has reinforced that all individuals will succeed. At-risk students in this generation can be in disbelief of even being at-risk and may assume that others will solve their problems. Federally funded TRIO programs have shown to a positive impact on at-risk student development. Although there has been sufficient evaluation and review of TRIO programs’ impact on disadvantaged college students, there is a lack of research of student evaluation of their high school counselors after they graduate. It is important to consider the high school counselor’s impact on postsecondary success. College students involved in TRIO completed surveys rating their high school counselor. School counselor rating scores were correlated with the number of school counselors in that school, r(20) = 0.45, p = .043. This study has implications for school counselors and emphasizes the importance of school counselor contact. This research is the first step in the evaluation of high school counselors from students even when they are no longer high school students

Synthetic Studies Toward Boron-containing Nucleosides

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Mob Grazing Results in High Forage Utilization and Reduced Western Snowberry Size

Mob-grazing strives to maximize forage utilization and minimize selective grazing by using high stocking densities in small paddocks for short durations (12–24 hr). Rotational-grazing uses low stocking densities for a longer time period, retaining about half of the original available forage; although selective grazing can occur. Three cattle (Bos taurus × Bos indicus) grazing intensities: mob- (stocking densities from 32,000 to 67,000 kg ha−1; duration—24 hr); rotation (stocking density—2500 kg ha−1; duration—35 d); and non-grazed systems were compared based on forage utilization and changes to western snowberry (Symphoricarpos occidentalis) (WS) patch volume in a 2-year South Dakota study. Pre- and post-grazing forage height was measured every 2.5 m along multiple 50-m transects with WS patch volume measured every 5 m. Forage utilization (consumed and trampled) ranged from 42 to 90% in mob-grazed areas, and harvest efficiency (forage consumed) ranged from 15 to 64%. WS patch volumes decreased by ≥45% in mob-grazed treatments compared with no change in rotational-grazing and increased cover in non-grazed areas. WS pre-graze patch size influenced mob-grazing impact; patches >6500 cm3 were browsed or trampled to a greater extent than smaller patches

Mob vs. Rotational Grazing: Impact on Forage Use and Artemisia absinthium

Short duration (≤24 h), high stocking density grazing systems (e.g., mob grazing) mimics historic prairie grazing patterns of American bison (Bison bison), and should minimize selective grazing. We compared mob [125 cow-calf pairs on either 0.65 ha for 12 h; or 1.3 ha for 24 h] vs. rotational [25 cow-calf pairs on 8.1 ha for 20 days starting in mid-May with or without 2,4-D application prior to grazing; and 15 days starting mid-April (no herbicide)] grazing systems based on forage utilization and impact to Artemisia absinthium (absinth wormwood) in a tall grass pasture of Eastern South Dakota. Grass height and density, and Artemisia absinthium patch volume were quantified pre- and post-grazing at sampling points along multiple transects. Mob grazing had >75% forage utilization, whereas rotational grazing averaged 50% (all consumption). Within a grazing season, three grazing systems suppressed Artemisia absinthium patches with rotation/spray (100% decrease) > mob (65 ± 10% decrease) > mid-May rotation (41 ± 16% decrease), whereas Artemisia absinthium patches in the mid-April rotation followed by summer rest dramatically increased in size. Artemisia absinthium patches <19,000 cm3 were browsed, whereas larger patches were trampled in mob-grazed areas, but avoided in rotational grazing. All Artemisia absinthium patches had regrowth the year following any grazing event

Spring Clipping, Fire, and Simulated Increased Atmospheric Nitrogen Deposition Effects on Tallgrass Prairie Vegetation

Defoliation aimed at introduced cool-season grasses, which uses similar resources of native grasses, could substantially reduce their competitiveness and improve the quality of the northern tallgrass prairie. The objective was to evaluate the use of early season clipping and fire in conjunction with simulated increased levels of atmospheric nitrogen deposition on foliar canopy cover of tallgrass prairie vegetation. This study was conducted from 2009 to 2012 at two locations in eastern South Dakota. Small plots arranged in a split-plot treatment design were randomized in four complete blocks on a warm-season grass interseeded and a native prairie site in east-central South Dakota. The whole plot consisted of seven treatments: annual clip, biennial clip, triennial clip, annual fire, biennial fire, triennial fire, and undefoliated control. The clip plots consisted of weekly clipping in May to simulate heavy grazing. Fire was applied in late April or early May. The subplot consisted of nitrogen applied at 0 or 15 kg N · ha−1 in early June. All treatments were initially applied in 2009. Biennial and triennial treatments were reapplied in 2011 and 2012, respectively. Canopy cover of species/major plant functional groups was estimated in late August/early September. Annual clipping was just as effective as annual fire in increasing native warm-season grass and decreasing introduced cool-season grass cover. Annual defoliation resulted in greater native warm-season grass cover, less introduced cool-season grass cover, and less native cool-season grass cover than biennial or triennial defoliation applications. Low levels of nitrogen did not affect native warm-season grass or introduced cool-season cover for any of the defoliation treatments, but it increased introduced cool-season grass cover in the undefoliated control at the native prairie site. This study supports the hypothesis that appropriately applied management results in consistent desired outcomes regardless of increased simulated atmospheric nitrogen depositions

Water Deficit Transcriptomic Responses Differ in the Invasive Tamarix chinensis and T. ramosissima Established in the Southern and Northern United States

Tamarix spp. (saltcedar) were introduced from Asia to the southern United States as windbreak and ornamental plants and have spread into natural areas. This study determined differential gene expression responses to water deficit (WD) in seedlings of T. chinensis and T. ramosissima from established invasive stands in New Mexico and Montana, respectively. A reference de novo transcriptome was developed using RNA sequences from WD and well-watered samples. Blast2GO analysis of the resulting 271,872 transcripts yielded 89,389 homologs. The reference Tamarix (Tamaricaceae, Carophyllales order) transcriptome showed homology with 14,247 predicted genes of the Beta vulgaris subsp. vulgaris (Amaranthaceae, Carophyllales order) genome assembly. T. ramosissima took longer to show water stress symptoms than T. chinensis. There were 2068 and 669 differentially expressed genes (DEG) in T. chinensis and T. ramosissima, respectively; 332 were DEG in common between the two species. Network analysis showed large biological process networks of similar gene content for each of the species under water deficit. Two distinct molecular function gene ontology networks (binding and transcription factor-related) encompassing multiple up-regulated transcription factors (MYB, NAC, and WRKY) and a cellular components network containing many down-regulated photosynthesis-related genes were identified in T. chinensis, in contrast to one small molecular function network in T. ramosissima

A Rapid Method for Measuring Feces Ammonia-Nitrogen and Carbon Dioxide-Carbon Emissions and Decomposition Rate Constants

A rapid approach is needed for determining the eff ectiveness of precision conservation on soil health as evaluated using CO2 and NH3 emissions. Th is study demonstrated an approach for calculating CO2–C and NH3–N emissions and associated rate constants when feces were applied to bare soil or soil + vegetation. In addition, point CO2–C emission measurements were compared with near continuous measurements. The CO2–C emissions were measured at 2 h intervals over 20 d, whereas ammonia volatilization was measured three times daily for 7 d. Total CO2–C emissions over 20 d were 5% lower [186 g CO2–C (m2 × 20 d) –1] than point measurement collected at 1100 h every day (197 g CO2–C (m2 × 20 d) –1), and about 10% lower than if collected every 2 d [206 g CO2–C (m2 × 20 d) –1]. A Fast Fourier transformation (FFT) showed that temperature and NH3–N and CO2–C emissions followed diurnal cycles and that they were in-phase with each other. Over 7 d, 20% of feces NH4–N was volatilized and that this loss was similar when feces were applied over vegetation or mixed into the soil. Feces additions increased the amplitude of the CO2–C diurnal cycle, and the fecal-C first-order rate degradation constants were higher when mixed with soil [0.0109 ± 0.0043 g(g×d) –1, p = 0.1] than applied over vegetation [0.00454 ± 0.00336 g(g×d) –1, p = 0.1]