Northwestern Wisconsin Research Articles

Vegetational Associations of Host-seeking Adult Blacklegged Ticks, Ixodes scapularis Say (Acari: Ixodidae), on Dairy Farms in Northwestern Wisconsin

As a measure of the risk for exposure to Lyme disease, we estimated the distribution of host-seeking adults of the blacklegged tick, Ixodes scapularis Say, on dairy farms in Barron County in northwestern Wisconsin. Vegetation ecotypes that were common to 18 farms that were representative of the county were surveyed by flag sampling. Tick prevalence and abundance, which were similar during fall and spring periods, were very low in farmhouse yards and forage croplands; only a single male was collected from 17 lawns. Sampling of 18 pastures with lactating cows also yielded only a single I. scapularis. In contrast, I. scapularis adults were captured in 9 of 37 samples from 18 pastures with heifers and dry cows; in those pastures, ticks were associated with woods and secondary vegetation or margins of pastures adjacent to woodlands. Blacklegged ticks were most prevalent and numerous in ungrazed woodlands; adults were captured in 27 of 53 samples on 13 of 15 farms, particularly when evidence of white-tailed deer, Odocoileus virginianus (Zimmermann), was apparent. The risk of encountering adult blacklegged ticks on dairy farms in Barron County, Wisconsin is therefore greatest in woodlands habitat. The presence of adult ticks in pastures with heifers and dry cows establishes an ecological basis for the exposure of dairy cattle to adult I. scapularis. Pastures with lactating cows, farmhouse yards, and forage croplands represent negligible risk.

Edge-Related Nest Losses in Wisconsin Pine Barrens

Predation of artificial nests in pine barrens savanna patches in northwestern Wisconsin was correlated significantly with proximity to edge (P = 0.02). Densities of blue jays (Cyanocitta cristata) and brown-headed cowbirds (Molothrus ater) were significantly greater along edge transects than savanna interior transects (P < 0.001 and P = 0.001). Land management practices in the pine barrens may influence edge-related nest loss.

Prevalence of granulocytic Ehrlichia infection among white-tailed deer in Wisconsin.

Human granulocytic ehrlichiosis (HGE) is caused by an agent that is nearly indistinguishable from the veterinary pathogens Ehrlichia equi and Ehrlichia phagocytophila. The deer tick, Ixodes scapularis, is a vector of the HGE agent, and the white-tailed deer is the primary host for adult Ixodes ticks. We assessed the distribution of granulocytic Ehrlichia infection among deer living within (Wisconsin) and outside (western and southern Iowa) the geographic range of L. scapularis. Whole-blood samples were tested for HGE 16S ribosomal DNA (rDNA) by PCR, and E. equi antibody was detected by indirect immunofluorescence assay (IFA). Antibody titers of > or = 1:64 were defined as positive, and all positive samples were retested with a second lot of substrate antigen. E. equi antibody was present in 14 (8%) of 187 Wisconsin deer and 0 of 60 Iowa specimens (rate ratio undefined; P = 0.025). An additional 30 serum samples from Wisconsin deer were excluded because IFA results were discrepant between substrate lots. The reciprocal antibody titers ranged from 64 to 512 (geometric mean, 141) for positive samples. PCR results were positive for 27 (15%) of 181 Wisconsin deer. The prevalence of infection in northwestern Wisconsin deer was not significantly different from that in central Wisconsin deer, as determined by IFA and PCR. In two samples that were sequenced, the 16S rDNA was nearly identical to that of the granulocytic Ehrlichia species but distinct from that of Anaplasma marginale. The DNA sequences of the samples differed from the published sequences for E. equi, E. phagocytophila, and the HGE agent by 1 or 2 nucleotides (> or = 99.1% homology) at phylogenetically informative sites. Granulocytic Ehrlichia organisms in deer are widely distributed within the geographic range of L. scapularis in Wisconsin. Deer may serve as useful sentinels for areas where HGE transmission to humans may occur.

Effects of Edge Type and Patch Shape on Avian Communities in a Mixed Conifer-Hardwood Forest

Forest bird communities were sampled along line transects in northwestern Wisconsin during June of 1985 through 1992 to determine whether edge type and patch shape affect avian abundance. Landscape structural characteristics quantified along these transects included: (1) edges that defined the habitat patches they separated, (2) fractals to quantify patch shapes, and (3) areal extent of different patches. Three multiple-regression models were constructed for 10 bird species and the mean number of individuals and species using the following sets of independent variables: (1) edge variables and fractals, (2) area variables, and (3) the first six components from a principal components analysis based on all independent variables. Multiple-regression analysis indicated that edge variables and fractal dimension explained the most variation in abundance for Black-capped Chickadees (Parus atricapillus), Red-breasted Nuthatches (Sitta canadensis), Hermit Thrushes (Catharus guttatus), and American Robins (Turdus migratorius). In contrast, area variables explained the most variation in abundance for Red-eyed Vireos (Vireo olivaceus), Chestnut-sided Warblers (Den- droica pensylvanica), and Ovenbirds (Seiurus aurocapillus). Abundances of Yellow-bellied Fly- catchers (Empidonax flaviventris), Common Yellowthroats (Geothlypis trichas), and White-throat- ed Sparrows (Zonotrichia albicollis) were equally correlated with both edge and area variables. Results of our study show that, for selected species, forest management strategies must be developed that consider not only stand characteristics, but also the edges created between these stands. Received 8 March 1995, accepted 30 August 1995.

Lyme disease spirochetes in ticks collected from birds in midwestern United States.

In a tick-spirochete survey conducted from all 1989 through fall 1992 in north-western Wisconsin, 4,256 birds (composed of 91 species) were examined for ticks. Infestations were recorded for 400 birds (composed of 30 species). Of 1,184 ticks taken from 335 birds (composed of 26 species), 60 (5%) Haemaphysalis leporispalustris (Packard) from 8 species of birds were infected with the Lyme disease spirochete. Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner. Similar surveys conducted in 1990 and 1991 in Minnesota and Michigan yielded 223 H. leporispalustris from 61 birds (composed of 23 species), all free of spirochetes. However, 1 B. burgdorferi-infected Ixodes scapularis (Say) was found on 1 bird species in Minnesota. Most ticks were collected in fall from ground-foraging birds such as thrushes and sparrows. These results confirm that tick-infested birds are important in disseminating Lyme disease spirochetes and may also play a role as sources for infecting ticks.

A Quantitative Approach to Developing Regional Ecosystem Classifications

Ecological land classification systems have recently been developed at continental, regional, state, and landscape scales. In most cases, the map units of these systems result from subjectively drawn boundaries, often derived by consensus and with unclear choice and weighting of input data. Such classifications are of variable accuracy and are not reliably repeatable. We combined geographic information systems (GIS) with multivariate statistical analyses to integrate climatic, physiographic, and edaphic databases and produce a classification of regional landscape ecosystems on a 29 340‐km2 quadrangle of northwestern Wisconsin. Climatic regions were identified from a high‐resolution climatic database consisting of 30‐yr mean monthly temperature and precipitation values interpolated over a 1‐km2 grid across the study area. Principal component analysis (PCA) coupled with an isodata clustering algorithm was used to identify regions of similar seasonal climatic trends. Maps of Pleistocene geology and major soil morphosequences were sued to identify the major physiographic and soil regions within the landscape. Climatic and physiographic coverages were integrated to identify regional landscape ecosystems, which potentially differ in characteristic forest composition, successional dynamics, potential productivity, and other ecosystem‐level processes. Validation analysis indicated strong correspondence between forest cover classes from an independently derived Landsat Thematic Mapper classification and ecological region. The development of more standardized data sets and analytical methods for ecoregional classification provides a basis for sound interpretations of forest management at multiple spatial scales.

Bobcat (Lynx rufus) Home Range Size and Habitat Use in Northwest Wisconsin

Bobcats were radio-tagged and monitored to estimate and compare annual and seasonal patterns in home range size and habitat use in northwestern Wisconsin. Annual and seasonal male home ranges extensively overlapped those of other males and females, whereas females maintained more exclusive areas. Annual male home ranges (60.4 km2 ? 23.4 kM2) were 112% larger than those of females (28.5 km2 + 3.7 kM2). Females expanded and contracted their home ranges seasonally; the largest home ranges occurred in winter. Males shifted similar-sized ranges seasonally resulting in larger annual ranges. Male bobcats selected lowland conifer forests, and avoided upland conifer stands, upland deciduous forest and mixed savanna cover-types. Females exhibited similar preferences but also selected for lowland deciduous forests and avoided unforested areas. Seasonal shifts in habitat use were evident for males and females; both used lowland conifer stands more, and unforested areas and upland deciduous forests less, in winter. The selection of lowland coniferous forests by males and females during all seasons suggest these areas are important range components

New Structural and Stratigraphic Interpretation of Lake Superior Basin from Hydrocarbon Exploration Geophysics and Geology: ABSTRACT

Between October 1987 and April 1992, two deep boreholes were drilled along the south shore of Lake Superior in a test of the hydrocarbon potential of the conglomerate, sandstone and shale composing the Middle Proterozoic Oronto Group ({approximately}1 billion years). These drilling ventures, preceded by geophysical programs, and combined with wireline and core information, support new interpretations of the structural and stratigraphic geology associated with the Midcontinent Rift System in the Lake Superior district. No.7-22 Terra-Patrick: A stratigraphic, but not structural fit. This borehole in Bayfield County, Wisconsin, drilled an expected sequence of Oronto Group clastic redbeds. No viable hydrocarbon shows were encountered. Six second reflection seismology profiles collected in northwestern Wisconsin indicate the Douglas Fault decreases in throw in an easterly direction, changing to a fold northeast of the borehole. This termination is associated with the south flank of White`s Ridge, a pre-rift residual high identified through modeling studies and seismic interpretations by local absence of Midcontinent Rift volcanics and overlying strata. To the southwest of Isle Royale, the pre-rift Grand Marias Ridge exhibits similar characteristics. No.1-29 St. Amour: A structural, but not stratigraphic, fit. Drilled in Alger County, Michigan, the St. Amour well appears to bottom in pre-riftmore » metamorphic basement rocks. This hole was 100% cored. No hydrocarbon shows were reported. Reflection seismology profile analyses verify a change in strike, from northeast to southeast, of the Keweenaw Fault in the eastern Lake Superior Basin. The drilled section included 6,000 feet of pre-Paleozoic red-beds containing cross-bedding, ripple marks, and multiple fining-upward strata.« less

Babesiosis in Wisconsin: A Potentially Fatal Disease

Babesiosis is emerging as an important tick-borne zoonosis in the United States. Most reported cases of this parasitic disease have been acquired in the Northeast. To date, only two clinical cases of Babesia microti infection acquired in the upper Midwest have been described. We report eight more cases. Most if not all of the 10 total cases probably were acquired in northwestern Wisconsin. Three cases (30% of 10) we now report were fatal and occurred in elderly patients (65-75 years old) who died after complicated hospital courses. One patient probably had had a latent Babesia infection that activated because of immunosuppression attributable to high-dose corticosteroid therapy and to splenic infarctions caused by cholesterol emboli. All three fatal cases were diagnosed incidentally and highlight the importance of considering the diagnosis of babesiosis in febrile patients who have been in babesiosis-endemic areas; examining their blood smears carefully; and treating promptly with clindamycin and quinine, and, if indicated, exchange transfusion. Medical personnel should be knowledgeable about this zoonosis, which is not limited to the northeastern United States, and is potentially serious, sometimes fatal.

Pollen Source Area and Pollen Productivity: Evidence from Forest Hollows

1 Although fossil pollen from forest hollows (~ 5 m in diameter) is often interpreted as a record of stand-scale forest changes, this assumption has not previously been tested by comparing pollen percentages in modern sediment to vegetation from a range of sampling radii. I compared pollen in surface sediment with distance-weighted basal area of trees in radii from 10 to l00 m, to test a model (Sugita 1994) that predicts the 'relevant pollen source area' for forest hollows is 50-100 m, and that about 40 % of the pollen comes from trees growing within this radius. 2 Maximum likelihood estimates of pollen productivity, based on the relevant source area, are used to test for differences in species pollen productivity between a pinedominated region in north-western Wisconsin, and a hemlock-northern-hardwoodsdominated region of upper peninsula Michigan. 3 Likelihood function scores, which measure the goodness-of-fit of the pollen-vegetation relationship based on the maximum likelihood method, show that estimates of pollen productivity (ac) and relative background pollen loading (co) improve as radius of distance-weighted vegetation sampling increases from 10 to 50 m. There is little further improvement from 50 to lOOm. Linear regression analysis of pollen percentages on distance-weighted basal area also shows little improvement in pollenvegetation correlation when vegetation samples from beyond 50 m are included. Predictions of pollen percentages therefore are not improved by increasing the vegetation sampling radius beyond 50-100 m. These results support Sugita's (1994) model prediction and confirm that fossil pollen in hollows records stand-scale vegetation heterogeneity at a scale of 50-lOOm. 4 Estimates of background pollen (co) indicate that on average, only 40-50% of the pollen in forest hollows comes from trees growing within 50-lOOm of the hollow. However, this is sufficient to record the stand scale vegetation heterogeneity because larger areas of vegetation are recorded as homogeneous regional background, even in patchy vegetation. 5 Relative pollen productivity of three monospecific pollen taxa (red maple, sugar maple, basswood) is similar for two regions, supporting the implicit assumption in palynology that pollen productivity is a species-specific constant. Productivity estimates of birch are similar between regions, although yellow birch dominates in one region and paper birch in the other.

Annual Variation in Bird Populations of Mixed Conifer-Northern Hardwood Forests

We examined annual variation in breeding bird populations at sites in northwestern Wisconsin and in the Upper Peninsula of Michigan from 1986 to 1992 to determine (1) the extent to which different bird species vary in abundance over time and (2) whether or not patterns of variation differ when viewed at local and regional spatial scales. Total abundance of long-distance migrants (species that winter in the tropics) declined during the first few years in both states but subsequent increases returned abundance to levels close to those that occurred at the start of the study. Short-distance migrants (species that winter in temperate regions) showed the greatest similarity between states in the extent and direction of variation in abundance among years; abundance reached a low in both states during 1990. Unlike migrant groups, abundance of permanent residents was not correlated between states. Permanent residents declined in abundance from 1987 to 1988 in Michigan, for example, but increased in abundance in Wisconsin. Fluctuations in abundance generally were poorly correlated among groups within a state. Repeated-measures analysis of variance (one-way) revealed that abundances of 13 and 21 (62%) common, long-distance migrants, 13 of 16 (81%) short-distance migrants, and 7 of 9 (78%) permanent residents varied significantly among years in one or both states. Fluctuations in abundance likely occurred in response to events on the breeding grounds. Factors likely to have affected populations include severe drought, particularly during 1987 and 1988, as well as successional changes in habitat. It is unlikely that events on tropical wintering grounds caused population fluctuations observed in neotropical migrants. Two-way ANOV A indicated that patterns of variation differed between the two study regions (significant interaction effects) for a number of species, particularly permanent residents. Results of this study thus ill~trate the importance of considering temporal variation in abundance at more than one spatial scale.

Influence of macroinvertebrates and macrophytes on waterfowl utilization of wetlands in the Prairie Pothole Region of northwestern Wisconsin

Influence of macroinvertebrates and macrophytes on waterfowl utilization of wetlands in the Prairie Pothole Region of northwestern Wisconsin

Jack pine budworm population behaviour in northwestern Wisconsin

Long-term (17–31 year) density estimates of jack pine budworm, Choristoneurapinuspinus Free. (Lepidoptera: Tortricidae), populations from 31 townships in northwestern Wisconsin were analyzed to investigate variation in population behaviour. Populations had varying combinations of cyclic components with periods of 5, 6, and 10 years. Populations that fluctuated with higher frequencies (shorter periods between outbreaks) tended to be found in locations where the habitat type was indicative of nutrient-poor and extremely dry soils. Many populations in these habitat types had high mean densities, and the coefficient of variation in density was smaller than that in other populations. Just under half (14) of the populations were regulated by statistically significant second-order density-dependent processes. Nevertheless, second-order processes were present to some extent in all populations examined. These results demonstrated that detection of density dependence and population regulation of jack pine budworm depends on the local site where studies are undertaken. Population fluctuations encountered in these populations are of the phase-forgetting quasi-cyclic kind. Studies of mechanisms that account for these cycles and cause populations to fluctuate at three different characteristic frequencies promise to be rewarding.

Growth and Size-Selective Mortality of Stocked Muskellunge: Effects on Size Distributions

Sport fisheries for muskellunge Esox masquinongy are often sustained by stocking. Size-selective mortality has been identified as an important factor affecting stocked muskellunge, However, this mortality is difficult to assess because its effects on the population can be confounded by growth. To partition observed shifts in length frequencies of stocked muskellunge into growth and mortality effects, two lots each of approximately 1,000 hatchery-reared muskellunge fingerlings were sorted into 10-mm size-groups, marked with size-specific fin clips, and stocked into two northwestern Wisconsin lakes. Beginning 30 d after stocking, we used electrofishing to examine length distributions and estimate abundance of stocked fish. Shifts in the length-frequency distributions after stocking were found to be caused by size-selective mortality and growth. Mortality was highest for the smallest fish. A size-based analysis indicated that growth in fall contributed far more than size-selective mortality contributed to changes in length distributions. Our analysis suggests that it may be important to monitor the fate of size-classes within cohorts if cohort dynamics are to be fully understood.

Wisconsin train accident costly, but not deadly

A disaster was avoided in late June when a train derailed in northwestern Wisconsin. Three railroad tankcars fell off a trestle and only luck prevented a liquid petroleum gas (LPG) tankcar from rupturing, with potentially explosive consequences. However, a noxious gas cloud that formed after a benzene mixture leaked from one car (C&EN, July 6, page 5) resulted in hundreds of thousands of dollars in claims against the rail carrier, and at least $1 million in initial cleanup costs. Toxicity studies following the accident are still under way. The June 30 accident involved three Burlington Northern tankcars, which fell 135 feet from a trestle into the Nemadji River outside Superior, Wis. Two tankcars, one containing explosive LPG and one containing butadiene, fell onto the soft, muddy riverbank and did not break open. The third, however, fell onto the rocky riverbed and cracked open, spilling most of its 26,200 gal of a benzene mixture of hydrocarbons. ...

Effects of nitrogen fertilization on young jack pine (Pinus banksiana) and on its suitability as a host for jack pine budworm (Choristoneura pinus pinus) (Lepidoptera: Tortricidae)

Effects of nitrogen fertilization on growth, foliar nitrogen concentration, and monoterpenes were determined on 7- to 11-year-old jack pine (Pinusbanksiana Lamb.) on two sites in northwestern Wisconsin. One site established after wildfire; the other after clear-cutting. Jack pine budworm (Choristoneurapinuspinus Free.) larvae were caged on fertilized and unfertilized trees on each site. Relations among foliar nitrogen, monoterpenes, larval survival, and adult budworm weight were examined. Foliar nitrogen concentration, needle weight, shoot and diameter growth, and monoterpene production were lower on wildfire site trees than on clear-cut site trees, and were significantly increased on both sites by fertilization. Fertilization increased production of staminate cones on the wildfire site. Height growth differed between sites but was unaffected by fertilization. Contrary to expectations based on the resource availability theory, foliar nitrogen and monoterpene levels were positively related. Survival of jack pine budworm larvae was greater on clear-cut than on wildfire site trees, but was not significantly affected by fertilization. Larvae on low-nitrogen trees on the wildfire site clipped more foliage than those on the clear-cut site, suggesting compensatory feeding. Adult female weight was higher for larvae on wildfire than clear-cut site trees. Two monoterpene compounds and site-related differences were the best predictors of adult female weight based on regression.

Nutrient dynamics in decomposing leaf litter of four tree species on a sandy soil in northwestern Wisconsin

The dynamics of 12 elements in decomposing leaf litter of jack pine (Pinusbanksiana Lamb.), paper birch (Betulapapyrifera Marsh.), trembling aspen (Populustremuloides Michx.), and northern pin oak (Quercusellipsoidalis E.J. Hill) were examined on a Typic Udipsamment (Orthic Regosol) in northwestern Wisconsin. Whereas the concentrations and absolute amounts of N, Ca, S, Zn, Mn, Fe, Cu, and Al generally increased after 1 year of decomposition, the levels of P, K, Mg, and B in decomposing leaf litter decreased. Two-way analysis of variance tests revealed significant differences in dry matter and concentrations and contents of most elements as a function of species and time elapsed. Macronutrients commonly were released from decomposing leaf litter in the following order (fastest to slowest): aspen &gt; oak = birch &gt; pine. The changes in N, P, Ca, and S in decomposing leaf litter generally followed the three-phase process described for N by other investigators. A cubic function described the initial-loss, accumulation, and final-release phases of these nutrients in decomposing leaf litter.

Foliar nutrient dynamics and nutrient-use efficiency of oak and pine on a low-fertility soil in Wisconsin

Seasonal changes in 10 nutrients were investigated in the foliage and current twigs of jack pine (Pinusbanksiana Lamb.) and northern pin oak (Quercusellipsoidalis E.J. Hill) growing on a sandy, nutrient-poor soil in northwestern Wisconsin. Midsummer (July 26) concentrations of all nutrients except Zn were significantly greater in oak foliage than in current needles of pine. Whereas the absolute amounts of N, P, K, Mg, S, B, and Fe in oak foliage peaked in midsummer, generally in late July, the amounts of Ca, Zn, and Mn continued to increase until leaf abscission. The absolute amounts of all 10 nutrients in current needles of pine increased over the growing season. Absolute amounts of nutrients in 2- and 3-year-old needles generally decreased from midsummer to leaf abscission. The two species differ in mechanisms of nutrient-use efficiency. Northern pin oak has a greater requirement for all macronutrients except Mg than jack pine. Although the absolute amounts are greater, proportionally lower amounts of required nutrients are retained in perennial tissues of northern pin oak than in jack pine. A large portion of the nutrient requirement in oak is met by recycling of nutrients contributed by litterfall, throughfall, and fine-root turnover. Northern pin oak resorbed greater amounts of N and K prior to leaf abscission than jack pine. In contrast, jack pine conserves nutrients by investing low amounts of nutrients per unit of leaf or bolewood production and by returning a low proportion of nutrients in litterfall per unit aboveground tissue produced.

Usefulness of natural regions for lake management: Analysis of variation among lakes in northwestern Wisconsin, USA

A map of summer total phosphorus in lakes was compiled recently for a three-state area of the upper Midwest for purposes of identifying regional patterns of total phosphorus in lakes and attainable lake trophic state. Spatial patterns in total phosphorus from approximately 3000 lakes were studied in conjunction with maps of geographic characteristics that tend to affect phosphorus balance in lakes to identify regions of similarity in phosphorus concentrations in lakes or similarity in the mosaic of values as compared to adjacent areas. While degrees of relative homogeneity are apparent at many scales, the map was designed at a scale that would yield regions with sufficient homogeneity to be useful for lake management throughout the area. In this study, data from 210 lakes in a 1560-mi2 area in northwestern Wisconsin, sampled by the Wisconsin Department of Natural Resources in the spring of 1988 (subsequent to the compilation of the phosphorus map), were examined to: (1) substantiate the existence of the regions depicted on the map in northwest Wisconsin, (2) determine the nature and relative precision of the regional boundaries, (3) determine the relative importance of natural and anthropogenic watershed characteristics, lake types, lake area, and lake depth in explaining within-region differences in lake phosphorus, and (4) demonstrate how the regions might be used by local lake managers.

Sulfur, Nitrogen, and pH Levels in Wisconsin Precipitation

AbstractPrecipitation is an important source of S and to a lesser extent N for agricultural crops and natural ecosystems. Reductions in S and N emissions have occurred and additional revisions in air quality standards will be expected to further reduce the amounts of nutrients such as S and N in precipitation. This study was conducted to determine current nutrient deposition rates and precipitation pH levels at 10 sites in important agricultural areas of Wisconsin. Bulk precipitation samples were collected at 10‐d intervals for a 2‐yr period from Nov. 1985 to Oct. 1987. Average annual SO4‐S deposition was 11 kg S ha−1 in northwestern Wisconsin and 23 kg S ha−1 in the south. These S deposition rates are approximately 42% less than the amounts found in a Wisconsin study conducted from 1969 to 1971. Despite this apparent decrease in S deposition, most of the S requirement for crop production is still likely to be provided by S in precipitation in most areas of the state. Annual average NO3‐N deposition also differed geographically with 4.2 kg N ha−1 deposited in the northwest and 8.4 kg N ha−1 in the south. Average annual NH4‐N deposition was 8.7 kg N ha−1 but showed no geographical trend, and variations among sites were probably influenced by point sources. For most sites, annual deposition amounts of nutrients were similar both years, although concentrations were lower during a year with above‐normal precipitation. The annual volume‐weighted mean pH ranged from 5.1 to 5.9 in a year with above‐normal precipitation and from 3.4 to 4.5 in a year with slightly below‐normal precipitation.