Central Minnesota Research Articles

Unsaturated‐zone wedge beneath a large, natural lake

Lake Belle Taine (480 ha) in north central Minnesota receives on average 76,000 m3 d−1 of water from Little Sand Creek but has no outlet. Water seeps out of the lake, flows through glacial outwash, and discharges into three nearby lakes with stages 13–14 m lower than Belle Taine. Seepage‐meter data indicate water is seeping out of Belle Taine at velocities up to 263 cm d−1 . Hydraulic‐head measurements made in the lake bed indicate the sediments are unsaturated beneath a portion of the lake edge, and a wedge of unsaturated sediments extends beneath the lake bed as much as 20 m from the shoreline. At the shoreline the water table is as much as 6.7 m below the lake surface. Modeling results of a similar hypothetical setting indicate that the horizontal extent of an unsaturated zone beneath a lake depends on (1) the permeability contrast between the outwash and the lake bed, (2) anisotropy, (3) lake bed slope, and (4) thickness of the lower‐permeability lake bed sediments. Although rarely documented, unsaturated sediments beneath a lake may not be extremely uncommon. Similar, much smaller unsaturated‐zone areas also have been observed beneath two other lakes in Minnesota.

Oviposition and Diapause Behavior in Colorado Potato Beetle (Coleoptera: Chrysomelidae) Populations from East Central Minnesota and the Valley of the Red River of the North

Oviposition and diapause behavior were compared among populations of Colorado potato beetle, Leptinotarsa decemlineata (Say), from six locations in 1994 and 1995. Locations ranged from Winnipeg, Manitoba (49° 49′ N), to Rosemount in east central Minnesota (44° 44′ N). Newly emerged first summer generation adults were held in field cages at each location for 7–14 d, then observed for 7 d in the laboratory for frequency of oviposition and frequency of burrowing behavior associated with diapause. Females from the Red River Valley seldom oviposited and although frequency of burrowing varied among locations it was independent of field and laboratory conditions. Under long-day laboratory conditions, 9–15% of females from east central Minnesota oviposited with frequency dependent on photoperiod experienced in the field, the critical photoperiod was 15.8 h. Under long-day laboratory conditions, 18–52% of beetles from east central Minnesota burrowed with frequency dependent on cumulative temperatures experienced in the field. Cool conditions were associated with higher frequencies of burrowing. Beetles from Rosemount exhibited identical responses under short-day and long-day laboratory conditions. In contrast, under short-day conditions, beetles from Big Lake did not oviposit and frequency of burrowing was not dependent on field conditions. We concluded that there is local geographic variation in Colorado potato beetle populations not only between the Red River Valley and east central Minnesota, but also among the different locations within these two areas.

Eastern White Pine (Pinus strobus) Growth Response to Partial Hardwood Overstory Release

Abstract We measured the response of white pine (Pinus strobus L.) saplings after partial release of a hardwood overstory on three sites in central Minnesota. Both height and diameter growth increased quickly after release compared to prerelease growth. Diameter growth response was related to prerelease diameter growth, but not to initial size of the sapling (diameter at time of release). On the other hand, height growth response was strongly influenced by the initial height of all trees, but not related to prerelease height growth in the largest saplings (initial heights > 8.76 m). Increased release intensity (i.e., difference between prerelease and postrelease overstory densities) resulted in higher diameter and height growth responses. The height/diameter ratios decreased after release, indicating that stability as well as growth increased after the release. North. J. Appl. For. 17(3):89–94.

Long-term corn grain and stover yields as a function of tillage and residue removal in east central Minnesota

Because the adoption of conservation tillage requires long-term evaluation, the effect of tillage and residue management on corn ( Zea mays L.) grain and stover yields was studied for 13 seasons in east central Minnesota. Three primary tillage methods (no-till (NT), fall chisel plow (CH), fall moldboard plow (MB)) and two residue management schemes (residue removal versus residue returned) were combined in a factorial design experiment on a Haplic Chernozem silt loam soil in Minnesota. No significant effects on grain yield were seen due to tillage treatments in 9 out of 13 years. The NT treatment resulted in lower yields than CH and MB treatments in years 6 and 7, and lower than the MB in year 8, indicating a gradual decrease in yield over time with continuous use of NT. There were differences due to residue management in 8 out of 13 years. The residue-returned treatments contributed about 1 Mg ha −1 greater yields in intermediate level dry years such as years 3 and 6, which had cumulative growing season precipitation 20 and 30% below the 9-year average, respectively. In excessively dry or long-term-average years, residues resulted in little yield difference between treatments. The most pronounced effects of residues were with the CH treatment for which yields were greater in 8 out of 13 years. The ratio of grain to total dry matter yield averaged 0.56 and did not vary with time or between treatments. These results apply primarily to soils wherein the total water storage capacity and accumulated rainfall are insufficient to supply optimum available water to the crop throughout the growing season. Under conditions with deeper soils or in either wetter or drier climates, the results may differ considerably.

RED-SHOULDERED HAWK NEST SITE SELECTION IN NORTH-CENTRAL MINNESOTA

We evaluated characteristics at Red-shouldered Hawk (Buteo lineatus) nest sites at two study areas with different topography and forest types in north-central and central Minnesota to identify nest site commonalities across geographically distinct areas. During the breeding seasons of 1994–1995, we located nests of Red-shouldered Hawks at the Camp Ripley Army National Guard Training Site and the Chippewa National Forest using a combination of broadcast surveys, helicopter searches, and systematic foot searches. All 38 nests at Camp Ripley and 18 nests in the Chippewa National Forest were in upland hardwood stands; the remaining two nests in the Chippewa National Forest were in aspen (Populus spp.) stands. We aged cores from 19 nest trees at Camp Ripley and measured habitat characteristics in a 0.04 ha circle centered on each nest tree and at a paired random site within the nest stand. We compared habitat variables at nest and random sites to identify habitat characteristics that were consistent predictors of nest sites versus random sites for each study area and for all nests combined. Compared to random sites, nest sites in the Chippewa National Forest had larger diameters at breast height (dbh) of the nest tree, taller nest tree height, and higher canopy height. At Camp Ripley, nest sites differed from random sites with regard to many more variables; nests were located in portions of the stand with larger trees and closer to surface water. Nest trees ranged in age from 50–89 years. Logistic regression models indicated that, for both study areas combined, nest tree dbh, basal area, canopy height, and distance to water were the most important variables in distinguishing nest sites from random sites.

Changes in two Minnesota forests during 14 years following catastrophic windthrow

Abstract. We measured tree damage and mortality following a catastrophic windthrow in permanent plots in an oak forest and a pine forest in central Minnesota. We monitored changes in forest structure and composition over the next 14 years. Prior to the storm, the oak forest was dominated by Quercus ellipsoidalis, and the pine forest by Pinus strobus. The immediate impacts of the storm were to differentially damage and kill large, early‐successional hardwoods and pines. Subsequent recovery was characterized by the growth of late‐successional hardwoods. In both forests the disturbance acted to accelerate succession. Ordination of tree species composition confirmed the trend of accelerated succession, and suggested a convergence of composition between the two forests.

Accumulation of Polychlorinated Biphenyls and Polycyclic Aromatic Hydrocarbons in the Snowpack of Minnesota and Lake Superior

The winter snowpack is a significant reservoir of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), and may be utilized as a surrogate receptor for assessing net atmospheric deposition. Seasonal snow cores were collected in late winter before snowmelt in northern and central Minnesota and at Eagle Harbor, Michigan on Lake Superior between 1982 and 1992. Snowpack concentrations of ∑-PCBs ranged from 1 to 14 ng/L with no significant decrease in concentrations from 1986 through 1992. ∑ 21-PAH concentrations in 1989 and 1992 ranged from 35 to 3280 ng/L with significantly higher concentrations nearer urban areas. Similarities between chemical accumulations in the snowpack and collection of integrated snowfall at Eagle Harbor support the hypothesis that dry deposition to accumulated snow is negligible at these remote locations. Tributary discharges from spring snowmelt to Lake Superior in 1992 contributed 7 to 11 kg of ∑-PCBs and 220 to 350 kg of ∑ 21-PAHs.

Tolerance for Freezing in Hatchling Turtles

Tolerance for Freezing in Hatchling Turtles

Biodiversity in Southeastern, Seasonally Ponded, Isolated Wetlands: Management and Policy Perspectives for Research and Conservation

BRIDGES is a recurring feature of J-NABS intended to provide a forum for the interchange of ideas and information between basic and applied researchers in benthic science. Articles in this series will focus on topical research areas and linkages between basic and applied aspects of research, monitoring policy, and education. Readers with ideas for topics should contact Associate Editors, Nick Aumen and Marty Gurtz. Isolated wetlands have received little attention as a specific ecosystem type, yet many development and regulatory programs affect them. This lack of recognition may stem from their small size, their variable hydrology, and lack of recognition of their regional significance in the southeast US. In recognition of this problem, and in response to a US National Research Council recommendation for more research in support of wetland protection, a group of individuals convened a workshop to discuss information needs and to develop strategies to protect southeastern isolated wetlands and their biodiversity. Because the organizers perceived a lack of linkage between researchers and managers, workshop participants included scientists, natural resource managers of public and private lands, and conservationists.

Irrigation and Nitrogen Management Effects on Potato Yield, Tuber Quality, and Nitrogen Uptake

Irrigation and N management are perhaps the most important aspects of successful potato (Solanum tuberosum L.) production in central Minnesota. With rising concern about current irrigation and N management practices and ground water quality, a two‐year study was undertaken to evaluate the impact of alternative irrigation and N management practices on potato yield, tuber quality, and N uptake. The treatments were different irrigation schemes (sprinkler and drip), irrigation triggers (70 and 40% of available water [AW] remaining), drip tape placements (surface or buried at 25 cm), N sources (urea, turkey manure, sulfur‐coated urea [SCU]), and timings of inorganic N fertilizer application. Rainfall in the area was less in 1994 (260 mm) than in 1995 (380 mm). As a result, irrigation applications in 1994 were greater than in 1995. Drip irrigation amounts were less than half of that applied by sprinkler irrigation treatments in both years. Except for the buried drip with fertigation (43.0 and 27.8 Mg ha−1 in 1994 and 1995) and the control (36.5 and 13.3 Mg ha−1 in 1994 and 1995), total tuber yields were similar regardless of irrigation and N source treatment. The turkey manure treatments in 1994 had significantly higher marketable tuber yields than the control, averaging 48.3 Mg ha−1 for both years. Total N uptake in 1994 was nearly 100% of that applied, while in 1995 it accounted for only 60% of the application. Lower N uptake was observed for the control (85.3 and 30.2 kg N ha−1 in 1994 and 1995, respectively), SCU (165.2 and 111.3 kg N ha−1 in 1994 and 1995), and BDF (157.2 and 80.1 kg N ha−1 in 1994 and 1995) treatments. The results showed that the use of unconventional N sources such as turkey manure and SCU are viable alternatives for potato production, provided they are managed properly.

Binomial Sequential Sampling for Management of Aster Leafhopper (Homoptera: Cicadellidae) and Aster Yellows Phytoplasma in Carrot: Impact of Tally Threshold on the Accuracy of Treatment Decisions

We sampled aster leafhopper, Macrosteles quadrilineatus (Forbes), populations in 1996 and 1997 from central and southern Minnesota to develop a binomial sequential sampling plan for the leafhopper in carrot, Daucus carota (L.). Both conventional and organic farms were sampled with a sample unit consisting of 10 sweeps. Mean density ranged from 0.13 to 16.15 leafhoppers per 10 sweeps. Resampling simulation software was used with the Wald sequential probability ratio test to validate a binomial sampling plan from field data. Action thresholds were chosen based on aster yellows infectivity level (the proportion of individuals vectoring the phytoplasma) and varietal tolerance combinations. We used 2 infectivity levels (1 and 5%) and 3 varietal tolerance levels (resistant, intermediate, and susceptible) to represent 6 scenarios encountered in the field. Results from resampling validation analyses were used to select a final tally threshold (number of insects in a sample needed to consider the sample infested), based on the probability of making a decision to treat (i.e., operating characteristic). The operating characteristic was analyzed to determine which tally threshold provided the highest proportion of correct decisions. A tally threshold of 3 was selected as the overall optimum across infectivity level and varietal tolerance combinations. For the 6 possible infestation scenarios, 4–10 samples (10 sweeps each) were required to make a treat or no treat decision. Stop-line graphs are provided for field use for all 6 scenarios. Use of binomial sequential sampling plans should provide effective management of M. quadrilineatus in carrots and minimize sampling time and cost.

Estimating the ground-water contribution in wetlands using modeling and digital terrain analysis

Wetland classification and management often requires information on the contribution of ground water to a wetland’s water budget. Direct estimation of this parameter, however, is time-consuming, expensive, and can typically only be accomplished for small areas. Thus, a method to characterize ground-water flow in wetland areas and regions may be useful in many applications. The estimation technique described combines the use of a digital elevation model (DEM) with transient numerical modeling and assumes that the water table reflects the general pattern of surface topography. The DEM grid elevations are used as initial heads in the model. Stepwise ground-water drainage from the flow domain is simulated until a reasonable match is obtained between the observed and model water tables. By knowing or assuming hydraulic conductivity and using the model water-table configuration, an estimate for ground-water flow to and from each discretized grid node can be estimated from Darcy’s Law and the Dupuit approximation. The net result, when mapped, shows the simulated distribution of recharge and discharge within and surrounding the wetland. Two examples from the Shingobee River headwaters in central Minnesota indicate how the method may be used. Geologically recent development of glacial landforms has led to numerous lakes, ponds, and wetlands in the region. Using a 30-m, 1∶24,000 scale DEM grid in combination with data from the U.S. Fish and Wildlife National Wetlands Inventory, the model predicts the most likely areas of ground-water interaction in and near wetlands and lakes. More quantitative results can be obtained by applying observed water budget and soil/aquifer parameter data.

Prevalence and initiation of preferential flow paths in a sandy loam with argillic horizon

Numerous studies have reported on preferential solute transport, giving evidence that preferential flow is widespread. However there has been little field documentation of the relative importance of different preferential transport mechanisms. This study used a dye tracer to examine the extent and relative importance of different preferential transport mechanisms in a glacial outwash-derived soil that is used extensively for high input agriculture in central Minnesota, USA (Verndale sandy loam: coarse loamy over sandy, mixed, frigid, Udic Argiborolls). Experimental treatments included three initial soil water contents (WET, MEDIUM, and DRY) and three dye solution application rates (FLOOD, SPRINKLER-High, and SPRINKLER-Low). Thirteen cm of FD&C Blue no. 1 (also known as Brilliant Blue FCF) food dye solution (200 g l −1) were applied to replicated 1 m×1 m plots in a recently tilled 5 year old alfalfa stand and to two additional plots with no history of alfalfa. Vertical soil profile faces were exposed at 10-cm increments across each plot. Extensive and deeper preferential dye movement occurred under FLOOD conditions regardless of initial soil moisture or recent vegetation history. The two SPRINKLER rates generally resulted in relatively shorter preferential flow paths (PFPs). Within-plot variability of dye patterns—including depth and number of PFPs—was very high. Most PFPs observed were associated with roots and decayed roots, or with patterns in the abruptness and topography of the boundary between the Ap and Bt horizons. Open burrows were uncommon, but contributed to extensive preferential flow in the two NO-ALFALFA plots. Our findings indicate that preferential transport is prevalent under the variety of application rate and soil moisture conditions evaluated, and that observable soil features appear to be initiators of the majority of the PFPs. Only a few (10 of 126) of the profiles excavated had preferential flow paths that were not associated with visible soil features. The observed high variability gives support to the idea that observations of spatial variability in pesticide transport studies is due to preferential transport. Our initial goal of elucidating the relationship between rate of application and the relative number and depth of PFPs was aimed at evaluating water flow patterns. However, subsequent research found that dye retardation was increased at slower application rates, indicating that the dye patterns we observed were due to both the rate and the pattern of water movement. As a result, we caution that our findings of generally deeper and more extensive preferential dye transport under the higher velocity FLOOD application rate do not necessarily indicate more extensive preferential water (or non-adsorbing solute) transport at this rate compared to the intermittent SPRINKLER rate. It is possible that our observations may be indicative of patterns in movement of adsorbed solutes such as pesticides, however this contention would require further research.

Ecological effects of mosquito control on zooplankton, insects, and birds

AbstractWe completed an integrated, 6–year study on the potential ecological effects of two mosquito control agents, methoprene (applied as AltosidTM sand granules) and Bacillus thuringiensis var. israelensis (Bti, applied as Vectobac‐GTM granules), on zooplankton, insects, and breeding birds in wetlands of central Minnesota, USA, from 1988 to 1993. The study was a before‐and‐after design with pretreatment (1988‐1990) and posttreatment (1991–1993) of 27 wetlands. Study sites were randomly selected and placed within one of three groups of sites, nine control, nine Bti‐treated, and nine methoprene‐treated. Selected populations of zooplankton, insects, and breeding birds were sampled within each of these wetlands. Insect densities were reduced by 57 to 83% and biomass was reduced by 50 to 83% in the second (1992) and third (1993) years of treatment. No negative effects on zooplankton or breeding birds could be attributed to treatment or changes to insect communities. Many factors may explain the lack of effects on breeding birds including, reductions in insects occurred after the nesting season was over, nest loss rates due to predation were very high (70%) and may have been a greater limiting factor to birds than mosquito control, and the density of breeding birds may be below carrying capacities, especially because not all wetlands in the landscape were treated and sufficient food may have been available. It is unclear what the long‐term consequences of insect reductions mean to wetland health. The lack of close coupling between zooplankton, insects, and breeding birds probably reflects the ecological complexity of these wetlands such as the presence of other limiting factors on population distribution and abundance. Although the study period was relatively long (3 years of treatment) compared with most ecological studies of pesticides, it may not have been long enough to fully predict the effects of decades of continued mosquito control.

Characterizing Seasonal Variations in Flexible Pavement Material Properties

As agencies progress toward mechanistic-empirical flexible design procedures, it is critical to quantify the relationships between climate factors and the resulting seasonal variations in pavement layer moduli for a given region. This was investigated for flexible pavement structures and climate conditions specific to Minnesota. The objective of this study was to quantify the relationships between climate factors, subsurface conditions, and pavement material properties for use in a mechanistic-empirical design procedure that reflect conditions specific to Minnesota. The approach used to establish these relationships may suggest possible directions for similar studies in other regions. The data used in this study were obtained from the Minnesota Road Research Project, located on Interstate 94 in central Minnesota. The extensive instrumentation, on-site weather station, and deflection testing performed at this facility provide valuable environmental and pavement response data. The results show that the maximum stiffness for the pavement layers occurs in the winter, and the minimum stiffness occurs at different periods in a typical year for the different layers. The asphalt concrete modulus is at a minimum in the summer when temperatures are high. The base layer modulus is at a minimum in the spring thaw period, and the subgrade layer modulus is at a minimum in the late spring and summer months. The seasonal variations in pavement layer moduli are used to establish seasonal factors for each layer which describe the modulus cycling in a typical year. These factors may be applied to a mechanistic-empirical design procedure specific to Minnesota.

Synovial chondromatosis in raptors.

Fourteen raptors, consisting of 13 great horned owls (Bubo virginianus) and one red-tailed hawk (Buteo jamaicensis), from central and north central Minnesota, western Wisconsin, and eastern South Dakota (USA) were admitted to a raptor rehabilitation center between June 1992 and June 1995, with perisynovial and synovial chondromatosis affecting multiple joints. Birds were severely debilitated primarily due to loss of shoulder motion. The etiology of these lesions in raptors is unknown.

Development and Validation of a Fixed-Precision Sequential Sampling Plan for Aster Leafhopper (Homoptera: Cicadellidae) in Carrot

From 1995 to 1997, data sets (351) were collected from 30 fields in central and southern Minnesota to determine the most efficient, fixed-precision, sequential sampling plan for density estimation of aster leafhopper, Macrosteles quadrilineatus Forbes, in carrot, Daucus carola (L.). Conventional and organic farms were sampled to obtain a range of leafhopper densities likely to be encountered with various management practices. Densities ranged from 0.01 to 6.97 leafhoppers per sweep. Taylor's a and b parameters were estimated fromp 266 data sets and used in conjunction W ith 15 independent data sets to validate the sampling plan with resampling software, The results showed that, for a density range of 0.01-1.61 leafhoppers per sweep, 20 samples of 10 sweeps each must be taken to achieve an average precision level of 0.25 (SE/mean). In subsequent analyses, results were partitioned into low ( 0.25) Final density can be compared with the aster yellows index for control guidelines.

Winter soil microclimate altered by corn residue management in the northern Corn Belt of the USA

Management of crop residue is important for promoting soil water recharge and early spring thaw in the northern Corn Belt of the USA. This study assessed the impact of residue management in no tillage, continuous corn ( Zea mays L.) production systems on the soil thermal and water regime during winter in west central Minnesota. Residue treatments were initiated in the fall over three years and included the removal of stubble and loose residue (RR) from the soil surface, all residue lying prostrate (PR) on the soil surface, and stubble standing and loose residue lying (SR) on the soil surface. Soil (to 0.3 m depth) temperatures were recorded hourly whereas soil water content, frost depth, and snow cover were measured weekly. The SR treatment effectively trapped more snow, which resulted in warmer soil (2°C or less), shallower frost penetration (as much as 0.5 m), and earlier soil thaw (up to 20 d) as compared with the RR or PR treatments. Winter soil temperatures and depth and duration of soil freezing were the same for the RR and PR treatments. Soil water content was the same for all treatments prior to fall freezing, but was less for the PR treatment than for the SR or RR treatment during winter due to less snowmelt infiltration for the PR treatment. Corn production utilizing no tillage in the northern USA necessitates the retention of stubble on the soil surface for promoting warmer soil during the winter as well as earlier spring thaw as compared with removing or chopping stubble.

Temperature of upland and peatland soils in a north central Minnesota forest

Soil temperature strongly influences physical, chemical, and biological activities in soil. However, soil temperature data for forest landscapes are scarce. For 6 yr, weekly soil temperatures were measured at two upland and four peatland sites in north central Minnesota. One upland site supported mature aspen forest, the other supported short grass. One peatland site was forested with black spruce, one supported tall willow and alder brush, and two had open vegetation — sedges and low shrubs. Mean annual air temperature averaged 3.6 °C. Mean annual soil temperatures at 10- to 200-cm depths ranged from 5.5 to 7.6 °C among the six sites. Soils with open vegetation, whether mineral or peat, averaged about 1 °C warmer annually and from 2 to 3 °C warmer during summer than the forested soils. The tall brush peatland was cooler than all other sites due to strong groundwater inputs. The mineral soils warmed more quickly in the spring, achieved higher temperatures in the summer, and cooled more quickly in the fall than the peat soils; however, the greatest temperature differences between mineral and peat soils occurred at or below 50 cm. In the upper 20 cm, vegetation and groundwater had greater effects on temperature than did soil type (mineral or peat). Summer soil temperatures were higher, relative to air temperature, during periods of greater precipitation. This effect was minimal at upland sites but substantial in the peatlands. In spite of the persistent sub-freezing air temperatures typical of Minnesota winters, significant frost developed in the soils only in those years when severe cold weather arrived before an insulating cover of snow had accumulated. Key words: Soil temperature, vegetation effects, forest soils, groundwater, peatlands

Use of non‐contacting electromagnetic inductive method for estimating soil moisture across a landscape

There is a growing interest in real‐time estimation of soil moisture for site‐ specific crop management. Non‐contacting electromagnetic inductive (EMI) methods have potentials to provide real‐time estimate of soil profile water contents. Soil profile water contents were monitored with a neutron probe at selected sites. A Geonics LTD EM‐38 terrain meter was used to record bulk soil electrical conductivity (ECA) readings across a soil‐ landscape in West central Minnesota with variable moisture regimes. The relationships among ECA, selected soil and landscape properties were examined. Bulk soil electrical conductivity (0–1.0 and 0–0.5 m) was negatively correlated with relative elevation. It was positively correlated with soil profile (1.0 m) clay content and negatively correlated with soil profile coarse fragments (>2 mm) and sand content. There was significant linear relationship between ECA (0–1.0 and 0–0.5) and soil profile water storage. Soil water storage estimated from ECA reflected changes in landscape and soil charactenstics.