Effect of Artificial Nesting Structure Density on Canada Goose Reproductive Success

We sampled earthworms in Lexington, Kentucky, and compared populations in high-maintenance lawiis (maintained by professional lawn-care companies) to those in low-maintenance lawns (maintained by indi- vidual owners without the use of lawn-care chemicals).We sampled 15 high-maintenance and 15 low- maintenance lawns with similar distributions in terms of geographic location within Lexington, age of house, and length of time the lawn was managed under the current maintenance regimen.Earthworms were col- lected during the period 6 Apr-10 Apr 1998 in each lawn by using formalin as an extractant.Significantly more earthworms per unit area were collected from high-maintenance as from low-maintenance lawns.Conversely, low-maintenance lawns had significantly greater earthworm dn' mass per unit area and dn-mass per individual earthworm.These results suggested that high-maintenance lawn care resulted in stunted growth of earthworms.Since earthworms are one of the most important members of the soil fauna, we suggest that organic methods and alternative plant systems be substituted for chemically maintained lawns.' Corresponding author.biological indicators of soil qualit)- (Blair et al.Journal of the Kentuck)' Academy of Science 61(1) 1996).In turf ecosystems, including lawns, rollini^karst plain underlain hy phosphatic earthworms are positi\el\' associatcil with Lcvin^ton Limestone ol Ordo\ician au;e.Al- many favorable soil characteristics inchidint^tliouu;h the study area is largeh' urbanized, na- low amounts of thatch, low bulk densit\, hiu;h ti\e soils are mapped as the Maur\-McAfee water infiltration and percolation rates, hit^h Association (Sims et al. 1968).About 85% of organic matter concentrations, di'ep rooting, the map unit is deep and moderateK-deep, low plant wilting proneness, low plant disease well-drained soils in residuum on uplands, severitv, and unitorm dispersion ol microbes with silt loam A horizons, silt\ cla\ loam B (Christians 1998; Turgeon 1999).horizons, and clay C horizons (Alfisols and Ul-Professional lawn-care sendees utilize man\' tisols in the USDA taxonomy); the remaining types of chemicids including fertilizers, fungi- 15% is silt loam soils in alluvium in sinkholes cides, herbicides, insecticides, and plant and drains (Mollisols and Inceptisols).growth regulators.Standard sources (e.g..The climate is temperate, humid, and con- Christians 1998; Vengris and Torello 1982)tinental.Mean annual temperature and prerecommend as many as nine fertilizer appli-cipitation, respectively, are 13C and 1148 cations and six herbicide applications annually, mm.Weather during the 5-day sampling pe- with insecticidi's applied as needed.Even riod of 6 Apr-lO Apr 1998 was normal, with when used at labeled rates some registered maximum and mininuun daily temperatures of lawn-care chemicals are highly to.xic to earth- 18C and 7C, and 30 mm of total precipita- worms and other soil invertebrates, while oth-tion.Soils were near optimal moisture content ers are less toxic but still cause chronic effects during the sampling period since there had and significant mortality' (Potter 1994; Potter been no extended dry periods and since rain-).To date, much research dealing fall during the preceding 12 months was ca.with the to.xicitv of lawii care chemiciils has 8% above average (Universit)-of Kentucky Ag- been performed in laboratories or under con- ricultural Weather Center 1999).trolled conditions at research facilities.Edwards and Bohlen (1996, Appendix A), for ex-^'^"""^^^are Survey ample, pnnided a summar\of the specific ef-A Lawn Care Survey was used to locate cofects of about 200 indi\idual chemicals on operators and to provide a pool of potential earthworms, and Potter et al. (1990, 1994) de-experimental lawns.The survey asked whether scribed the effects of 40 commonly used pes-the lawn was maintained using lawn-care ticides and plant growth regulators on earth-chemicals (herbicides, fertilizers, etc.), and, if worms in turf.so, if the lawn was maintained by a profes-UnHke controlled research plots, real lawns sional lawn-care senice.In addition, the sur- are simultaneously subject to many t)pes of vey identified age of the house, length of time chemicals and to other types of stress such as the lawn was maintained under the current dessication and compaction.In our study, we maintenance regimen, and other factors that sampled earthworms in real lawns and com-could influence our research.A totd of 340 pared populations in high-maintenance lawns survey forms was distributed through the ad-( maintained by professional lawn-care com-ministrative offices of the Math, Science & panics using syntheUc chemicals) to those in Technology Center and the University of Kenlow-maintenance lawns (maintained by indi-tucky.Two hundred and four completed sur-\idual owners by mowing but without using vey forms were returned.To minimize vari- chemicals).abilitv' in mtiintenance regimen, we first eliminated idl lawns that were maintained by own-MATERIALS AND METHODS ers themselves using lawn-care chemicals.We ^, , also eliminated lawns with underground irrigation systems and fenced-in pets.We thenOur study was conducted in Lexington, carried out a stratified-random sampfing of the Fayette Count)', the second largest cit\' in remaining lawns to select 15 high-mainte- Kentucky Lexington, founded about 1779, nance and 15 low-maintenance lawns with presently occupies about 12,000 ha and has a about equal distributions in terms of geopopulation of ca.242,000.The landscape is a graphic location within Lexington, age of Earthworms in Lawns -Jones and Kalisz Table 1.Characteristics of eart:hworm populations and of mature and immature earthworm specimens in lawns main- tained by individual owners without the use of lawn care chemicals (low-maintenance) and in lawnis maintained by professional lawn care services (high-maintenance) in Lexington, Kentuck)'.Within a row, different letters indicate that the characteristic differed between maintenance types at the indicated level of significance (P) using Mann-Whitney tests; n = 15 of each type lawn.Low-maintenance 11 it^ll-Miainrnancf Earthworm cliaracteristic M(?dian value p Number (no/sample frame) Total dry mass (mg/sample frame) Individual dry mass, mature (mg/individual) Individual dry mass, immature (mg/individual) 3.7 b 320 a 130 a 43 a 6.0 a 187 b 68 b 19 b 0.03 0.02 0.007 <0.001house, and length of time the lawn was manspecies (mature); anaesthetized length and av aged under the current maintenance regimen, erage diameter were measured.Thirty lawns were chosen since this was the number that could be sampled within 1 week, the maximum samphng period that we judged still short enough to avoid variabihty in weather or other factors that could cause earth- worms to move deep into the soil or to aesti- Calculations and Statistical Analysis Dry mass of each specimen was calculated by using anaesthetized length and diameter to calculate volume, assuming the anaesthetized shape to be a right circular cylinder Volume vate.All experimental lawns were associated was then converted to dry mass using Ed- with single-family homes, were regularly ward's (1967) average values for density (1.064 g/cm^) and percentage dry matter (26%) of lumbricids.Non-parametric Mann-Whitney tests were used to compare high-maintenance versus low-maintenance lawns in terms of the number and total dry mass of earthworms collect- ed per plot and the dry mass of individual mowed, and were less than 4000 m^in size. Field and Laboratory MethodsEarthworms were collected during the pe- riod 6 Apr-10 Apr 1998.The sequence of sampling alternated between high-mainte- nance and low-maintenance lawns, with ran- domized order within each type of lawn.On earthworms.This was done for all specimens each lawn, a single random point was chosen together and for immature and mature speci- away from the influence of structures, walk- mens separately.Spearman's correlations were ways, trees, and plant beds.Grass was chpped used to examine relationships between numand thatch removed from a small area sur-ber and mass of earthworms, age of house, rounding the point, and a square 0.1-m^frame some lawn and agricultural chemicals may ad-come more popular with homeowners as in- versely affect non-target organisms including formation on organic practices (e.g., WSHUearthworms and other soil invertebrates (Pot-FM and Duesing 1999) and commercial ser-

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