Forest soils adjacent to urban interstates:Soil physical
and chemical properties,heavy metals,disturbance
legacies,and relationships with woody vegetation
Tara L.E.Trammell &Brad P.Schneid &
shrimpMargaret M.Carreiro
Published online:5July 2011#Springer Science+Business Media,LLC 2011
Abstract While urban ecology is an expanding field of study,some natural areas within the urban environment remain under-examined.The include naturally regenerating forest communities adjacent to urban interstates.In addition,the status of interstate soils and their relationships with the community composition of forested interstate verges has received little ecological study.The purpo of this study was to examine variation in soil conditions along forested interstate corridors in Louisville,KY and to explore the extent to which soil characteristics (e.g.,bulk density,pH)and heavy metals (e.g.,Pb,Zn)vary with respect to three factors:interstate (e.g.,traffic density),surrounding urban environment (e.g.,industrial land u),and interstate construction legacies.Additionally,we explored the relationships buttercup
between veral edaphic factors and woody vegetation structure in the forested verges.We found that the degree and direction of the slope of land towards the interstate and the distance to the interstate pavement were strong determinants of soil characteristics and heavy metal concentrations,suggesting that the movement of de-icing salts,heavy metals,and other pollutants from the interstate was important in determining forest soil conditions along urban interstates.Since within our study area the highways did not extend into rural lands,variation in urban land us and cover within 26km of the city center was not large enough to explain variation in soil characteristics or heavy metals,except for a positive correlation between chromium and surrounding industrial land u.We did find that past physical soil disturbance caud by interstate construction (e.g.,imported fill)left an important legacy on soil characteristics,heavy metal retention,and woody plant growth patterns in forests adjacent to urban interstates.The legacy of interstate construction on the current forest community structure (e.g.,lower species richness)and the future forest (e.g.,reduced tree regeneration)may further alter ecosystem productivity and ecosystem rvices provided by the forests and their soils.Keywords Urban soils .Urban forests .Interstate highways .Heavy metals .Woody vegetation .Disturbed soil profiles .Road ecology Urban Ecosyst (2011)14:525–552
DOI 10.1007/s11252-011-0194-3
T.L.E.Trammell (*):M.M.Carreiro
Department of Biology,University of Louisville,Louisville,KY 40292,USA
B.P.Schneid
Department of Biological Sciences,Auburn University,Auburn,AL 36849,USA
Introduction
Cities are receiving more ecological attention due to the increasingly critical need to understand the larger scale conquences of people’s interactions with their immediate environment in areas of high population density(Grimm et al.2000).However,some natural areas within the urban environment remain under-examined.The forest communi-ties adjacent to urban interstates are among the natural areas.In a landscape where a large portion of the total land area is ud for anthropogenic activities,roadside environments may provide important opportunities for conrving local natural ecosystems(Saunders and Hobbs1991).The majority of the land area in the urban environment is ud for residential, commercial,industrial,and institutional purpos,resulting in a landscape that is cmz
highly fragmented,covered with impervious surface and intenly ,lawns,gardens). Forested communities along urban interstates may be extremely important in conrving native plant species,which in turn can provide resources for other organisms.As in all ecosystems,the community composition,physical structure,biomass,and productivity of plant communities along urban highway corridors(and hence their effectiveness as plant and wildlife corridors in urban ecosystems)depends on the underlying soil matrix. However,the status of soils adjacent to urban highways and their relationship with plant communities has received little ecological attention.doubt的用法
Soil conditions along urban highway verges are important to study becau soils affect water and pollutant movement across the landscape and they may differentially constrain or promote growth of native and exotic plant species and hence affect primary productivity and other ecosystem process.In addition,they provide a basis for understanding how historical ,soil disturbance during highway construction)and current anthropogenic ,from the surrounding urban matrix,interstate vehicle travel) affect highway verge forests and the ecosystem rvices they provide to people.The combined effects of current road conditions,past road construction,and the surrounding urban environment create a mosaic of soil conditions alongside roads that need to be considered when attempting to explain variation in plant community composition and ecosystem process along urban roadside habitats.
dance with meRoads have well known effects on the chemical and physical properties of soils adjacent to them(Forman et al.2003).The constant vibration of road u and deposition of fine textured soil particles can increa soil compaction(Craul1985).De-icing salts chemically modify roadside soil by increasing its osmotic potential,altering pH,and increasing the mobility of heavy metals and cations(Forman and Alexander1998).Heavy metal concentrations are high alongside roads(Quarles et al.1974;Trombulak and Frisll2000). Thus,roadside environments have exhibited elevated soil compaction,and salt and heavy metal concentrations.Since roads have numerous effects on the physical and chemical condition of nearby habitats(Spellerberg1998),a“road-effect zone”has been calculated and found to cover22%of the land area in the contiguous United States(Forman2000).
Conditions and materials originating from the surrounding city can also affect soils and soil process along urban interstates.Urban environments have altered environ-mental conditions and elevated pollutant loads(Grimm et al.2008;Pickett et al.2011). Most urban areas exhibit elevated temperatures,incread inorganic nitrogen and hydrogen ion deposition,and higher heavy metal concentrations relative to surrounding rural areas(Botkin and Beveridge1997;Carreiro et al.2009;Gatz1991;Lovett et al. 2000;Parker et al.1978;Pouyat and McDonnell1991;Pouyat et al.2008).Therefore, soils along roads are affected by conditions and chemical inputs from the greater urban surroundings as well as from the nearby road itlf.The alterations can affect soil
nutrient cycling(Kuperman1999),soil moisture content(Pickett et al.2011),and other variables that in turn affect plant growth.
In addition to the direct effects from recent and current road u and the city at large, historical legacies from past soil disturbance during road construction may also influence highway soil conditions and process(Trombulak and Frisll2000).Road construction is an important disturbance becau it not only results in habitat loss and fragmentation,but also leaves a long-term legacy of greatly altered soil horizon structure.The disturbances include topsoil removal,burial of upper soil horizons,compaction,and import of soil and fill.The removal of topsoil during road construction not only alters topography,but may also deplete soil organic matter(stored carbon)and nutrients,ed and spore banks,and decompor communities.Such structural modification could reduce rates of soil functions, such as nutrient cycling,until organic matter accumulates and soil communities are reconstituted to pre-disturbance conditions.Therefore,filling with imported soil may be needed to create desirable soil structure for subquent vegetation planting.Such activity may result in buried A horizons and altered soil horizon development(Short et al.1986). The legacy effects from interstate construction and current interstate impacts on soils are likely to determine the conditions for subquent plant productivity along urban interstate forests for decades.
The combined impacts of the interstate,surrounding urban environment,and past road construction create a mosaic of soil conditions along urban interstates that need to be considered when attempting to explain variation in plant community and ecosystem process in roadside habitats.While there have been studies that have examined either urban soils or road impacts on soils,few have examined roadside soils along interstates in cities.Previous studies on soils adjacent to urban roads primarily examined the road zone directly adjacent to the pavement or the mow zone alongside ,Ho and Tai1988;Turer et al.2001).Our study focus on the soils in forest communities adjacent to urban interstates.
The goal of this study was to examine variation in soil conditions along forested interstate corridors in Louisville,KY,and to explore the extent to which soil properties may vary due to three primary factors:interstate usage and hard ,traffic density),the surrounding urban environment,and construction legacies.We addresd the following questions:1)Which local interstate-scale site ,degree and direction of the land’s slope toward the interstate)are most strongly correlated with variation in soil characteristics and heavy metals?;2)How do soil ,pH,bulk density,texture)and heavy metals vary along interstates passing through a county that differs in urbanization intensity?;3)Do soil characteristics and heavy metals vary with pmssql是什么
ast interstate construction practices?We expected that soil conductivity(measures of de-icing salt residues)and heavy metals would be higher clor to the city center and where traffic densities were greatest. Gradients of soil conductivity and heavy metals were expected to decline steeply with increasing distance from the interstate road edge since they originate from pollutants emanating from the road itlf(Forman and Alexander1998).We also expected soils that were disturbed during construction to have altered soil properties with respect to undisturbed soils.However,directionality of patterns associated with soil bulk density, texture,organic carbon,and total nitrogen were difficult to predict becau they are affected by multiple ,vehicle vibrations and emissions)and biotic factors,as well as past construction disturbance.We did not expect variation in soil characteristics and heavy metals to be related to variation in soil ries or parent material in our city since local scale impacts such as disturbance and pollutants emanating from the interstate were expected to be more important in determining soil conditions than larger scale patterns in soil ries.左手边
英文翻唱歌曲An additional objective of this study was to relate the patterns in ,soil) conditions to the patterns in woody vegetation ,adult tree density,tree edling density)obrved along Louisville interstates(e Trammell2010for details).We addresd the question:Does the vegetation structure of Louisville interstate forests relate to patterns in soil characteristics and heavy
metals?We had no preconceived predictions about relationships between soil conditions and vegetation becau many factors contribute to relationships between soils and vegetation composition.
Methods
Study area
Louisville,Kentucky(38°15′N,85°46′W)is located along the Ohio River in the Interior Low Plateau,Bluegrass Section(National Atlas of the U.S.2009)and encompass an area of1,032km2.Louisville has a total population of713,877with a mean density of695 persons km−2(U.S.Census Bureau2008).The mean annual precipitation is113cm,which is evenly distributed throughout the year.The mean annual temperature is13.8°C,the mean minimum temperature is−3.9°C in January,and the mean maximum temperature is30.6°C in July(National Climate Data Center2009).
flatteryInterstate sites
Three interstate highways pass through Louisville Metro(equivalent to Jefferson County after a2003c
ity-county government merger).From the city center,Interstate-64(I-64) extends to the east,I-65to the south,and I-71to the northeast(Fig.1).To determine soil characteristics and heavy metal concentrations along urban interstates,a total of twenty-six 100-m2plots were established along I-64,I-65,and I-71within Louisville Metro.Plots were lected in a stratified random manner within1km intervals from the city center to the county boundary.Since it was difficult to determine a priori the areas along the highway that had been greatly disturbed in the past,our experimental design was chon to improve our ability to detect whether there are relationships between edaphic factors and ongoing disturbance related to traffic density and distance from the city center.Determinations of soil disturbance legacies occurred after plots were chon.Due to more inten urban development clo to the city center along I-65,no forest plots were found along this highway within10km of the city center,whereas a more even study plot distribution was possible along I-64and I-71.The width of forested vegetation varied along the highways and usually there was space for only one10×10m plot at each location.However,in a few instances additional10×10m plots could be placed at50m and100m from the interstate road edge along I-64and I-65.
To provide an index for current road conditions,traffic density values were ud as a surrogate in our analys for vehicle emission concentrations.The data were obtained from the Kentucky Transport
韩国语在线翻译ation Cabinet(KYTC Traffic Count Program2007).The average daily traffic density by highway within the Louisville Metro boundary varied with I-65having the highest volume(52,406vehicles km−1d−1),I-64having an intermediate volume(29,129vehicles km−1d−1),and I-71having the lowest traffic volume(14,162 vehicles km−1d−1).The locations of highest traffic volume for I-65and I-64(141,000 and131,282vehicles d−1,respectively)occurred approximately14km from the city center,where they crosd a ring road,I-264.Maximum traffic density for I-71(69,965
Fig.1Map of Jefferson county,metro Louisville,showing the location of21forest plots(black circles) along I-65,I-64,and I-71and five additional forest plots along I-65and I-64(50-m and100-m from the plot adjacent to the interstate)
vehicles d−1)was approximately half that of I-65and I-64and occurred2km from the city center,where all three highways converge.
Soil pedon descriptions
Soil scientists from the USDA Natural Resources Conrvation Service(NRCS)visited each of the twenty-one forest plots adjacent to I-64,I-65,and I-71to provide detailed soil descriptions.Each pedon description provided information on soil classification and horizon ,pH;Appendix1,Table9).NRCS pedon descriptions provided a basis for determining the type of soil disturbances caud by interstate construction in our plots.The construction of I-64,I-65,and I-71was completed approximately40years ago(1968–1972)for all three interstates(KYTC Projects Archive 2008).Due to the experimental design we ud across the three interstates,statistical analysis of the frequency of different soil disturbance categories for this study was neither possible nor the initial primary goal.Instead,we ud pedon data to determine if soil distu
rbance categories could provide additional explanatory power for edaphic conditions and forest community composition at our interstate plots.We distinguished four types of soil disturbance categories across our plots:imported fill(n=3),local fill(n
