Calibration of Pulse-Shape Discriminating NaI(Tl) Detectors

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Phosphorus source--sink relationships of stream sediments in the Rathbun Lake watershed in southern Iowa, USA

The surface waters of Rathbun Lake watershed in southern Iowa are impacted by agricultural sources of sediments and nutrients, including phosphorus (P). Because stream sediments often play an important role in regulating P concentrations in stream water, we investigated sediment-water column P relationships in four creeks within the watershed and then evaluated the relationship between sediment properties and indicators of the risk of P loss. Based on Mehlich-3-extractable P (17 to 68 mg kg -1) and degree of P saturation (2 to 12 %), stream bank and bed sediments at the four sites were unlikely to serve as major sources of P. However, equilibrium P concentrations, which ranged from 0.02 to 0.12 mg L-1, indicated that bed sediments could release P to the water column depending on dissolved P (DP) concentrations in the stream water and the time of year. The likelihood of P desorption from the sediments increased with increasing pH (r=0.92, p \u3c 0.01) and sand content (r = 0.78, p \u3c 0.05), but decreased with clay content (r = −0.72, p \u3c 0.05) and iron (Fe) (r = −0.93, p \u3c 0.001) associated with organic matter. From these results, we speculate that changes in land use within the riparian areas may, at least initially, have little effect on P concentrations in the streams. Low concentrations of DP relative to total P (TP) in these streams, however, suggest that P loads to Rathbun Lake can be reduced if P inputs from eroded bank sediments are controlled

Modeling Phosphorus Capture by Plants Growing in a Multispecies Riparian Buffer

The NST 3.0 mechanistic nutrient uptake model was used to explore P uptake to a depth of 120 cm over a 126 d growing season in simulated buffer communities composed of mixtures of cottonwood (Populus deltoids Bartr.), switchgrass (Panicum virgatum L.), and smooth brome (Bromus inermis Leyss). Model estimates of P uptake from pure stands of smooth brome and cottonwood were 18.9 and 24.5 kg ha−1, respectively. Uptake estimates for mixed stands of trees and grasses were intermediate to pure stands. A single factor sensitivity analysis of parameters used to calculate P uptake for each cover type indicated that Imax, k, ro, and Lo were consistently the most responsive to changes ranging from −50% to +100%. Model exploration of P uptake as a function of soil depth interval indicated that uptake was highest in the 0–30 cm intervals, with values ranging from 85% of total for cottonwood to 56% for switchgrass

Riparian land-use, stream morphology and streambank erosion within grazed pastures in southern lowa, USA: A catchment-wide perspective

Factors influencing streambank erosion at the field/reach scale include both watershed andriparian land-uses, stream hydrology and channel morphology at the catchment scale. This studyassesses the relationship of riparian land-uses, stream morphologic characteristics and catchmentscale variables to streambank erosion within grazed riparian pastures in the Southern Iowa DriftPlain. Thirteen cooperating beef cow–calf farms and their catchments ranging from 2.5 to 12.9 km2in the Rathbun Lake watershed in South Central Iowa (USA) were chosen to conduct this study.Results suggest that the integration of stream morphologic characteristics and riparian land-uses atboth the reach and catchment scale are necessary to explain the current level of streambank erosionmeasured at the reach scale. Larger catchment size or catchments with more total channel lengthwere found to experience more bank erosion at the reach scale. A significant positive relationshipbetween percent sand-and-silt in the bank soil and bank erosion rates implies that bank soils with lesscohesiveness are more erodible. Catchment-scale assessments of the thirteen watersheds showedthat within the 50 m corridor on both sides of the stream, 46 to 61% of riparian area was devoted toagricultural use and only 6 to 11% was in ungrazed perennial vegetation, much of it enrolled in theUSDA Conservation Reserve Program. Overall, this and previous Rathbun watershed studies haveshown that intensive agricultural use of riparian areas over such extents of time and scale could bedirectly (in field scale) and/or indirectly (watershed scale) related to excessive amounts of streambankerosion (ranging from 8.6 to 38.3 cm/yr) to receiving streams and lakes leading to their impairmentand reduction in ecological services. Exclusion of cattle grazing in the riparian areas along bufferedstream lengths (2.1% of the total watershed area) of the Rathbun watershed would reduce this impact.This approach could also be applicable to other similar watersheds with extensive land-use undergrazed management.United States Department of Agriculture (USDA) National Institute of Food and Agricultur

Psychosocial Contexts of Diabetes and Older Adulthood: Reciprocal Effects

The present study was conducted to assess the reciprocal effects between the psychosocial contexts of diabetes and older adulthood. Data were collected from 191 community-dwelling adults over the age of 60 with non-insulin-dependent diabetes mellitus. Results indicate that older adults with diabetes reported higher rates of selected chronic illnesses, lower self-rated physical health, and higher levels of depression than did comparison samples of older adults without diabetes. Compared with younger adults with NIDDM, the present sample of older adults perceived fewer impacts of diabetes, including fewer symptoms of poor metabolic control, less emotional impact, fewer barriers to adherence, and less complex regimens. Overall levels of social support and regimen adherence were high. Older adults in this sample reported wanting minimal help from their family and friends with self-management activities and receiving more help than desired with following a meal plan and taking medications. Implications of the unique context of older adulthood for diabetes self-management are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69058/2/10.1177_014572179101700507.pd

Impacts of Cattle Grazing Management on Sediment and Phosphorus Loads in Surface Waters

In 2001 (yr 1), 2002 (yr 2), and 2003 (yr 3), three blocks of five 1-ac paddocks were grazed by beef cows on hills at the Iowa State University Rhodes Research and Demonstration Farm to determine the effects of grazing management on phosphorus (P) and sediment runoff from pastureland. Grazing management treatments included an ungrazed control (UG), summer hay harvest with winter stockpiled grazing (HS), grazing by continuous stocking to a residual sward height of 2 in. (2C), rotational stocking to a residual sward height of 2 in. (2R), and rotational stocking to a residual sward height of 4 in (4R). At four times (late spring, mid-summer, early autumn, and early the subsequent spring) in each year, rainfall simulations were conducted at 6 sites within each paddock. Rainfall simulators dripped at a rate of 2.8 in./hr over a 5.4-ft2 area for a period of 1.5 hours. Runoff was collected and analyzed for total sediment, total P, and total soluble P. Simultaneous to each rainfall simulation, ground cover, penetration resistance, surface roughness, slope, the contents of P and moisture of the soil, sward height and forage mass were measured. Sediment flow was not affected by forage management practice. There was no difference between UG, HS, 4R in the amount of total P or soluble P lost in runoff, but greater amounts of total and soluble P were lost from 2C and 2R than from the other management practices (P\u3c0.05). A greater amount of sediment was lost from the pastures during the late spring period than during other parts of the year (P\u3c0.05). Losses of sediment, total P, and soluble P from pastures can be controlled by suitable grazing management practices

Effects of Grazing Management on Selected Stream Bank Characteristics and Stream Bank Erosion

Six 30-acre cool-season grass pastures, containing predominantly smooth bromegrass and bisected by a 642- foot stream segment, were grouped into 2 blocks and assigned one of three treatments: continuous stocking - unrestricted stream access (CSU), continuous stocking - restricted stream access (CSR), and rotational stocking (RS). Stream bank condition and surface roughness and stream morphology were evaluated pre-, mid-, and post-grazing from 2005 to 2007. Stream bank erosion was monitored monthly from May through November over the same three years. Stream banks in CSU pastures had greater vegetative cover, stability, and condition scores than did the CSR or RS pastures implying that the stream banks in pastures in which cattle had unrestricted access were more susceptible to erosion than stream banks in pastures in which cattle access to stream banks was restricted or controlled. However, no effect of grazing management on the rate of change of stream cross sectional area, net stream bank erosion, or erosion deposition activity was observed in any of the three years