Modeling military trampling effects on glacial soils in the humid continental climate of southern New York
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<ul><li><p>Journal of Environmental Management 8</p><p>ecf</p><p>al</p><p>ilita</p><p>ilita</p><p>d fo</p><p>ine</p><p>l co</p><p>on</p><p>ies3</p><p>disturbance caused by off-road vehicles and heavy foot</p><p>In this construct, the military must ensure it does every-thing possible to protect and maintain its training lands.The impact of military vehicle trafc on soil is well known;</p><p>The preponderance of research on trampling impact on</p><p>In a study by Young and Gilmore (1976) on threecampgrounds in Illinois, they suggest that compaction maystabilize and not increase with use. This assertion was</p><p>ARTICLE IN PRESSsupported with evidence that although compaction tendedto be greater at the center of all campsites than at theperimeters, these differences were not statistically different.</p><p>0301-4797/$ - see front matter r 2006 Elsevier Ltd. All rights reserved.</p><p>doi:10.1016/j.jenvman.2006.06.012</p><p>Corresponding author. Tel.: +1845 938 6511; fax: +1 845 938 5522.E-mail address: email@example.com (K.W. McDonald).trafc often leads to disruption of soil structure, reducedplant cover, degradation of biological and physical soilcrusts, soil compaction, reduced water inltration, in-creased runoff, and accelerated erosion (Doe, 1993;McCarthy, 1996; Kade and Warren, 2002; Gilewitch,2004). By its nature, military training constitutes anextreme form of land use and degrades training landsusefulness if not maintained. Because of the limitedamount of available training land, maintaining this landoften conicts with established military training practices.</p><p>soil properties has focused on recreational use and impact.Research into the effect of induced foot trafc onsoil properties is limited. Work by researchers (Lutz,1945; Dotzenko et al., 1967; LaPage, 1962; Monti andMackintosh, 1979; Bryan, 1977) focused on measuringtrampling effects in recreation areas and public forestparks. A subsequent qualitative (low-, moderate-, high-use)labeling approach to describe the impact of trampling onthese areas was developed without denite qualitativeconstraints.experiment. Mathematical models were created based on empirical data from a trampling experiment using a more standard logistical</p><p>growth curve as well as curves based on Weibull and gamma cumulative distribution functions (CDFs). The experiment and the resulting</p><p>models give quantiable continuous inference on the effects of trampling, as opposed to the existing qualitative assessments. These</p><p>baseline models will be the foundation for future studies of land management when trampling occurs.</p><p>r 2006 Elsevier Ltd. All rights reserved.</p><p>Keywords: Soil compaction; Math modeling; Trampling; Bulk density; Military training; West Point</p><p>1. Introduction</p><p>The purpose of this research is to create a baseline modelof soil compaction response to trampling and a methodol-ogy to model the effects of trampling on soil. Surface</p><p>however, little is known concerning the impact of militarytrampling on soil. Compaction as a soil condition indicatoris well established. Soil compaction by its nature is a directmeasure of use and can be applied as an indirect measure ofthe impact of military training.at an increasing rate for several hundred passes and nally leveled and remained at or below 1.30 g/cm through the remainder of theModeling military trampling effcontinental climate o</p><p>LTC Kenneth W. McDonaDepartment of Civil and Mechanical Engineering, United States M</p><p>bDepartment of Mathematical Sciences, United States M</p><p>Received 23 July 2004; received in revise</p><p>Available onl</p><p>Abstract</p><p>The purpose of this research is to create a baseline model of soi</p><p>effects of trampling on soil. Although trampling studies have been c</p><p>a different perspective and approach. The data showed bulk densit4 (2007) 377383</p><p>ts on glacial soils in the humidsouthern New York</p><p>da,, LTC Andrew Glenb</p><p>ry Academy, Bldg 752, Mahan Hall, West Point, NY 10996, USA</p><p>ry Academy, Thayer Hall, West Point, NY 10996, USA</p><p>rm 7 June 2006; accepted 13 June 2006</p><p>2 April 2007</p><p>mpaction response to trampling and a methodology to model the</p><p>ducted in the past, the analysis of military training in part provides</p><p>remained relatively constant for a time and then began to increase</p><p>www.elsevier.com/locate/jenvman</p></li><li><p>A similar nding was noted in a study on military campingimpact on soil properties at Fort Leonard Wood, Missouri.Trumball et al. (1994) found that although bulk densitiesincreased at low- and high-use sites compared to undis-turbed sites there was not signicant difference betweenlow- and high-use areas. In another military study,Whitecotton et al. (2000) conducted an extensive studyon the impact of military encampment at the US Air ForceAcademys Jack Valley Training Area. Their researchfound no signicant differences between the bulk densitieson low- and high-use camp sites. In a cattle tramplingstudy, Guthery and Bingham (1996) looked at a theoreticalbasis for management of trampling by cattle. Of importand applicability, their study developed quantitativepredicative models from which they used empirical resultsto assist in developing range management techniques.In a series of studies, David Cole and others analyzed the</p><p>effects of trampling and compaction. In 1992, Cole et al.found that differences in bulk density as a measure ofcompaction were not much different between moderate-and high-use sites. In a series of trampling studies</p><p>Finally several studies have looked at tramplingscompactive effect on vegetation. McNearney et al. (2002)investigated tramplings effect on the germination andvigor of prairie grass. Their study found a direct correla-tion between foot trafc, compaction and reduced germi-nation and stunted growth of prairie grass. Likewise,Roovers et al. (2004) conducted a 2-year study in thechanges in vegetation structure and found short-termeffects consist of the mechanical deterioration of plantmaterial, whereas long-term effects of trampling includedirect as well as indirect effects on the total system ofvegetation and soil (e.g. compaction on root functions).These results clearly illustrate that vegetation coverdeclines when trampling intensity increases.</p><p>2. Methodology</p><p>2.1. Study area</p><p>The West Point Military Reservation is located on the</p><p>ARTICLE IN PRESSK.W. McDonald, A. Glen / Journal of Environmental Management 84 (2007) 377383378conducted in 1985, Cole looked at the effects of tramplingon vegetation cover and soil condition and found that themost rapid increase in compaction occurred within the rst5075 passes, and then a decreasing rate occurred up toabout 400 passes until the compaction resistance leveledout. In 1988, Cole concluded a 3-year trampling andrecovery analysis and noted that compaction increasedfrom year 1 to 2, but showed no marked increase incompaction from year 2 to 3. Cole noted this as anunexpected result when considering the trampling rateremained constant and continued throughout the 3-yeartrampling experiment.Fig. 1. The West Point Militarbanks of the Hudson River in southeast New York,approximately 50 miles north of New York City andencompasses an area of approximately 16,080 acres(cantonment area2250 acres and training area13,830acres) (Fig. 1). The training land, southwest of thecantonment area, is characterized by mountainous terrainwith open elds, forests, training areas, weapon ranges,and impact areas. Additionally, several ponds and lakes areused for public recreation areas and reservoirs. The areaincludes the watershed for the West Point MilitaryReservation and the local community of Highland Falls(M. Anderson, 2002, USMA, pers. comm.).y Reservation, New York.</p></li><li><p>ARTICLE IN PRESS</p><p>n B</p><p>,500rval </p><p>the</p><p>viroPrecipitation is well distributed throughout the year andis adequate for all vegetation. The total annual precipita-tion is 121.9 cm of which 50% usually occurs in Aprilthrough September. In winter, the average temperature is1.7 1C and the average daily minimum temperature is6.1 1C. In summer, the average temperature is 22.8 1C andthe average daily maximum temperature is 28.9 1C (Olsson,1981).This region is characterized by narrow elevated moun-</p><p>tainous terrain composed mostly of metamorphic Precam-brian gneiss and granite formed during the Proterozoic era.</p><p>L1L2</p><p>L4L5</p><p>L3</p><p>L6L7</p><p>L8L9</p><p>T1</p><p>T2</p><p>T3 T4</p><p>-Climbing Wall-Hurdle-Parry-Rock Wall-Bridge-Contour-Stream-Bunker-Culvert-Stairs-Low Crawl</p><p>230</p><p>236</p><p>230</p><p>Bataa</p><p>Experiment Site</p><p>1 : 2Inte</p><p>Fig. 2. The Bataan Bayonet Assault Course on</p><p>K.W. McDonald, A. Glen / Journal of EnThis provides the basis for the mineral content associatedwith the soil. The predominant soil minerals are vermicu-lite, quartz, chlorite and iron oxide (US Geological Survey,1958; McDonald, 2003).The soils in this area are Inceptisols specically dened</p><p>as Hollis soils having a thin very dark grayish browngravelly ne sandy loam topsoil and yellowish brownsubsoil. These soils form in well drained to somewhatexcessively drained, sloping and gently sloping areas inglacial till deposits derived from crystalline rock (schist,gneiss, and granite). Soil size distribution (45% sand; 40%silt; 15% clay-base on the International Soil ScienceSociety Size denition) was determined using manual sieveanalysis (Automatic Tray Shaker) and laser diffractionparticle size analysis (Beckman Coulter LS Series based onthe Fraunhofer and Mie theories of light diffraction).Gravel percentage was minimal to none. Due to time andavailable equipment, the organic matter content (8.5%)was determined by burning and washing the soil (Olsson,1981; McDonald, 2003).The area vegetation is mainly deciduous trees with</p><p>shrubs and low lying vegetation below the tree canopy. Thevegetation cover and ground litter consisted of deciduoustree leaf material, shrubs and vine vegetation. Thethickness of the material was approximately 2.55 cmbefore the experiment began.This research is part of a greater research effort to</p><p>measure the effects of trampling on the Bataan BayonetAssault Course (BBAC) (Fig. 2). Therefore, an experimentsite was selected southwest of the BBAC. The experimentalsite has similar soil as the BBAC, it is level without adiscernable slope and it has not previously been used fortraining. Additionally, placing the experiment site close tothe BBAC allowed the use of cadets without impacting thetraining. The BBAC consistently has a high degree</p><p>N</p><p>T5 T6T7</p><p>T8T9</p><p>ayonet Assault Course</p><p> Contour2 meters</p><p>West Point Military Reservation, New York.</p><p>nmental Management 84 (2007) 377383 379of training use. Every year, approximately 1500 cadetstraverse this training course during the summer trainingcycle. The course is rectangular in shape, oriented south-west to northeast (Fig. 2), and approximately 40m wide by300m long. The course consists of nine lanes, each lanecontaining identical stationary obstacles that a soldiermight commonly encounter in a wartime environment.Examples of the stationary obstacles include: ladder walls,parry structures, bunkers, and culverts (Fig. 2). All lanesare identical and all obstacles are positioned uniformlythroughout the course.</p><p>2.2. Laboratory analysis</p><p>The Standard Proctor test (hand method) was used togenerate a compaction curve for the soil sample at theBBAC test site. The Standard Proctor test is a geotechnicalengineering test that consists of compacting soil in a15.2 cm diameter mold by dropping a 2.5 kg hammer ontothe sample from a height of 30.5 cm replicating thecompactive effort of 600 kN-m/m3. A moisture-densitycurve is developed for determining the maximum compac-tion of a particular soil at the optimum moisture contentbased on the applied compactive effort. The test was</p></li><li><p>adjusted to reect the compactive effort of the averageweight and shoe size of a cadet. The impulse momentumtheorem was used to determine the compactive effort of theaverage cadet (1624N). Applying this force to the forceequation mv Ft the fall height for the compactionhammer was determined to be 20.8 cm. Likewise, the effectof vegetation was replicated by using vegetation as acushioning layer during the compaction test and a nalcurve was generated for a total of three curves (Fig. 3).</p><p>2.3. Field methods</p><p>The trampling experiment conducted at the BBACfollowed a modied version of the standardized proceduresdeveloped by Cole and Bayeld (1993). Cadets arrive at theBBAC for initial instruction prior to negotiating thecourse. After the initial instruction, cadets walk throughthe experiment site and traverse a path approximately 1mwide by 10m long to get to their particular starting points.Cadets continued this procedure throughout the summertraining cycle for a total of 3088 passes. Bulk densitymeasurements were recorded approximately every 100150</p><p>moisture content was 32%. Bulk densities were plotted tocorresponding number of passes.</p><p>2.4. Numerical modeling</p><p>The modeling phase combined laboratory experimentaldata and the eld data into mathematical models toreplicate the trampling response curve. The general shapeof the soil bulk density response curve is an increasingfunction that is bounded below at an initial bulk densityand above at a maximum bulk density based on a speciedapplied load. Cumulative distribution functions (CDFs)from probability and statistics theory also carry the sameabove and below bounding characteristics (Devore, 2000).Two CDFs, the Weibull and the Gamma, can be used toportray a soils response to trampling. By shifting theCDFs, models were developed to replicate the soilsresponse to trampling. Additionally, a logistical growthcurve can also replicate this type of bounding characteristicand, by adjusting the rate of growth; a soil-response curvecan replicate the trampling effect on the soil (Polking et al.,2002). These three approaches were adjusted to t the</p><p>ARTICLE IN PRESS</p><p>act</p><p>w/H</p><p>stur</p><p>K.W. McDonald, A. Glen / Journal of Environmental Management 84 (2007) 377383380passes. A total of 22 soil samples were taken periodically atthe end of each training event using an ELE Internationalhammer-driven core sampler: 7.62 cm diameter densitytube with a 2.83 104m3 capacity. The depth of samplewas 7.62 cm and included the surface layer material.Sample holes were not backlled but were marked withred ags along the path to ensure subsequent sampleswould not be taken from the same location. Samples weretaken to the laboratory, weighed, dried at 107 1C for 24 h,reweighed and bulk density determined. The average</p><p>1.15</p><p>15 20 25</p><p>Dry</p><p> Uni</p><p>t Wei</p><p>ght (g</p><p>m/cm</p><p>3 )</p><p>Comp1.40</p><p>1.35</p><p>1.30</p><p>1.25</p><p>1.20</p><p>1.10</p><p>1.05</p><p>1.00</p><p>Standard 20.8 cm </p><p>MoiFig. 3. Standard Proctor test with modication to reect actual impact in natural curve obtained at the BBAC and compared todetermine the best t model.Laboratory experiments and the eld collection data</p><p>mentioned earlier were required to determine the boundedlimits for the soil bulk density. Combining the data fromthe laboratory experiments (maximum density) with theeld data (minimum density and natural curve), thebounded upper and lower portions of the curve wereestablished and applied to the three mathematical functionsto identify an accurate model for soil response to</p><p>30 35 40 45</p><p>ion Test</p><p>eel 20.8 cm w/Heel and Vegetation</p><p>e Content (%)eld co...</p></li></ul>
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