Accelerating landscape change on the slopes and grazing country
Effects of simulated elk grazing and trampling (II): Frequency
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Transcript of Effects of simulated elk grazing and trampling (II): Frequency
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EFFECTS OF SIMULATED ELK GRAZING AND TRAMPLING (I):INTENSITY
Susan P. Rupp1.3, Mark C. Wallace1, David Wester1, Stephen Fettig2, and RobertMitchelJ1
1 Department of Range, Wildlife, and Fisheries Management, Box 42125, Texas Tech University,Lubbock, TX 79409-2125, USA; 2 Bandelier Nationa! Monument, HCR 1 Box 15, Los Alamos, NM87544-9701, USA
.ABSTRACT: Vegetative impacts caused by Rocky Mountain elk (Cervus elaphus nelsoni) grazingand trampling have been a growing concern for natural resource managers. The threat toarcheological resources and naturally functioning ecosystems as a result of excessive elk trampling
.and grazing now rank as the highest management priority at Bandelier National Monument (BAND),New Mexico. In summer 1998, BAND erected a series of ungulate exclosures and paired referenceareas to evaluate elk impacts on the vegetative community in pinon-juniper (Pinus edulis -Juniperus spp. [PJ]), ponderosa (Pinus ponderosa) grassland, and mixed-conifer (MC) habitattypes. We evaluated simulated grazing/trampling treatment combinations applied at differentintensities from January through May of 1999 and 2000. Litter cover was negatively correlated withclipping intensity in PJ and MC sites. Trampling more consistently impacted parameters and maystimulate plant productivity at an intermediate intensity, especially in terms of forb response.Longer time periods may be needed to detect vegetative responses to changes in grazing pressureespecially in ecosystems that have developed with a history of grazing pressure.
ALCES YOLo 37 (1): 129-146 (2001)
Key words: Cervus elaphus nelsoni, elk, grazing, New Mexico, trampling
Grazing systems are partially defined soil characteristics, individual plant and com-by the intensity (amount of plant material munity characteristics (e.g., density, mor-removed) and frequency (the number of phology,physiology),andtemporalandspa-times a plant is defoliated) of use which, in tial variation in environmental conditionsturn, affects both the quality and quantity of influence the type and degree of impactforage produced (Motazedian and Sharrow (Weigel et al. 1990, Bastrenta et al. 1995).
.1990). Few studies have attempted to iso- Divergent management objectives oflate the effects of intensity or frequency of the state of New Mexico, Los Alamosuse (Gillen et al. 1990) and it is often unclear National Laboratory (LANL), Bandelier
.whether effects are caused by the removal National Monument (BAND), tribal com-of vegetation or associated trampling. Stud- munities, and private lands hamper effec-ies have isolated effects of grazing tiveelkmanagement(Allen 1996). Hunting(Oesterheld 1992) or trampling intensity on BAND is prohibited by Code of Federal(Warren et al. 1986, Abdel-Magid et al. Regulations (CFR), Title 36, Part 2, Sec-1987,Tollneretal.1990),buthaveignored tions 2.1-2.4 (Fettig 1997); any direct re-possible interactive effects. In addition, duction of the elk herd would require akind of animal, season and intensity of use, legislative act of Congress. Before any
3 Present address: Los Alamos National Laboratory, ESH-20 (Ecology Group), MS M887, LosAlamos, NM 87545, USA
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ELK GRAZING INTENSITY -RUPP ET AL. ALCES YOLo 37 (1), 2001
actions can be taken, however, there is a Vegetative patterns are dependent onneed for quantitative, scientific information elevation and topography (Wilcox andon the potential impacts of the Bandelier elk Breshears 1994). Lower elevations (1,680herd. Population dynamics must be evalu- -2,015 m) are characterized as pinon-juni-ated and impacts to vegetative and soil per (PJ) woodland and are composed ofcommunities, if any, must be quantified. stands of pinon pine (Pinus edulis) andThe objectives of this study were to assess one-seed juniper (Juniperus monosperma)changes in density, percent foliar/litter with understory shrubs of wavy leaf oakcover, basal area, species richness, and (Quercus undulata), Apache plumecomposition through the application of dif- (Fallugia paradoxa), and mountain ma- '
ferent intensities of simulated clipping and hogany (Cercocarpus montanus) (Browntrampling within elk exclosures. 1982). Mid-elevational transitional
ponderosa (Pinus ponderosa) grasslandSTUDY AREA (PG) areas (2,015 -2 ,440 m) include an
Bandelier National Monument is located overstory of ponder os a pine and understoryin the Jemez Mountains of north central of Gambel oak (Quercus gambelii), NewNew Mexico (35:53:38N 106: 17:02W) ap- Mexican locust (Robinia neomexicana),proximately 8 km south of Los Alamos in and mountain mahogany. Typical grassesthe Pajarito Plateau (Fig. 1). It is bordered in PG include mutton grass (Poaby Santa Fe National Forest to the west, fendleriana), Junegrass (KoeleriaLANL to the east, and private lands to the cristata), and mountain muhlynorth and south. Native American reserva- (Muhlenbergia montana). Upper eleva-tion lands are also found throughout the tion mixed-conifer (MC) areas (2,440 -surrounding areas. The monument's 13,290 3,240 m) have a variety of overs tory spe-ha range in elevation from 1,680 m in the cies that include Douglas fir (Pseudotsugalower canyons near the Rio Grande to about menziesii), white fir (Abies concolor), blue3,240 m near the summit of Cerro Grande. spruce (Picea pungens), and quaking as-
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.
.
t01234: ,
Fig. 1. Study area on Bandelier National Monument, New Mexico, 1998-2000, showing extent of the1977 La Mesa fire and locations of the 15 elk exclosures erected in 1997.
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ALCES YOLo 37 (I), 2001 RUPP ET AL. -ELK GRAZING INTENSITY
pen (Populus tremuloides). Gambeloak, NG r;:-l r-;;lr;:lrock spirea (Holodiscus dumosus), and cccc NT L:J L.:J L.:Jccccwaxflower (Jamesia americana) are typi- CCCC ~G ~G 0G ~G
NT LT MT HT
cal understory shrubs and slender
wheatgrass (Agropyron trachycaulum), ~@]~~Canada bluegrass (Poa compressa), and L.:J L.:J
Parry oatgrass (Danthonia parryi) arecommon grasses in the MC zone. Canyonbottoms have riparian communities that in- Fig. 2. Designation of clipping X trampling treat-
1 d 1 f tt d (P I ment combinations inside exclosures. Clip-cue narrow ea co onwoo opu us. .
..pIng treatments were applIed at 100% stand-
angustifolla) and boxelder (Acer ing crop removal either 0 (none), I (light), 2
negundo).. (moderate),or3 (heavy) times while tramplingIn 1977, approxImately 6,180 haofland was applied at 0, 5, 25, or 100 footfalls/m2 atO
in Santa Fe National Forest, BAND, and (none), I (light), 2 (moderate), or 3 timesLANL burned in the "La Mesa" fire (Fig. (heavy), respectively. Clipping treatments1). Sixty-nine percent, or 4,250 ha, of the are designated with 'G' while trampling istotal area burned was on BAND (Foxx designated with 'T'. Treatments were ran-1984). The 1977 La Mesa fire changed domly assigned to l-m2 experimental units.
available forage conditions and is believedto have contributed to a population increase exclosure. While, because of vegetativeof the elk herd (Allen 1996). complexity and diversity, experimental units
Average annual precipitation on the in MC sites were 0.25 m2.Pajarito Plateau is 330 to 460 mm (National A two-factor factorial, randomized blockOceanographic and Atmospheric Adminis- design (Steel and Torrie 1980) was used totration, Climatological data, Los Alamos, evaluate the impacts of clipping, trampling,NM, http://www.ncdc.noaa.gov, 2001) of and their interaction. Treatments werewhich about 45% occurs in July, August, applied at 3 clipping intensities (none [0%]and September. Average daytime tem- moderate [40-60%], or heavy [100%] stand-peratures range from 32.2°C in the summer ing crop removal) and4 trampling intensities(max. = 41.1°C) to -9.4°C in the winter (none [0 footfalls/m2], light [5 footfalls/m2],(min. = -30.6°C). Over this study, 1998 -moderate [25 footfalls/m2], or heavy [1002000, temperatures were generally higher footfalls/m2]) during a single treatment ap-
.than the 1920 -1999 average, except for an plication (Fig. 2). A split-plot arrangementunseasonalcoldfrontinApril1999. Annual with time as a subplot factor allowed forprecipitation during the 1998 -1999 and analysis over the 2 years of the study.
.1999 -2000 field seasons was also lower Treatments (clipping and/or trampling) werethan average. randomly assigned to experimental units (1
m2/0.25 m2 plots) within each block
METHODS (exclosure).Experimental Design Clipping was used to simulate grazing
During summer of 1998, 1560 m x 60 m while trampling was simulated using anungulate exclosures (5 exclosures in each artificial hoof cast from dental acrylic (Proof 3 different habitats -MC, PG, and PJ) Orthodontic Services, Racine, Wisconsin,were erected on BAND. In October of USA) molded from the front hoof print of an1998, a plot consisting of 12 1 m2experimen- elk (Acorn Naturalists@, Tustin, California,tal units was established inside each USA). Two of these artificial hooves were
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ELK GRAZING INTENSITY -RUPP ET AL. ALCES YOLo 37 (1), 2001
securely bolted to the bottom of a pair of class were treated as sampled units and
sandals which could then be strapped on the zeroes were added to the dataset. Basal
feet of the investigator. The average front area, species richness, and litter cover were
hoof load of an elk is approximately 685 g/ only analyzed within habitats. For all analy-
cm2 (Telfer and Kelsall 1984). For pur- ses, significance was delineatedata=0.10.
poses of this study, applied hoof load was
calculated to be in the range of 673 -818 g/ RESULTS
cm2. This design attempted to emulate the We report results of combinations of
rocking or churning effect caused by a hoof intensity of clipping and trampling treat-
when the animal is walking, which has been ments. Rupp et al. (2001) examined the
overlooked in other simulated studies where effects of frequency of treatments. Analy-
mechanical devices have been used (War- ses of pre-treatment plot data revealed block
ren et al. 1986). Trampling in the MC plots (i.e., exclosure) X treatment interactions
was applied to a full 1 m2 area even though (FI,43 = 31.61, P < 0.001) for density in the
effects were measured only on 0.25 m2. PJ habitat type as well as for foliar cover in
Pre-treatment data were collected and MC (F I43 = 4.09, P = 0.049) and PJ (F =, 1,43
treatments were applied in January through 22.46, P < 0.001) habitats. Initial block X
May 1999 when elk normally would use treatment interactions were also detected
each habitat type. Post-treatment data in PG habitat, but removal of exclosure PG-
were collected and treatments were applied 5 that had been burned in 1998 and exclosure
again during the same time periods in 2000. PG-l that had been burned in 1999 rem-
Variables measured included density, foliar/ edied this effect for both density (P= 0.334)
litter cover, basal area, productivity, spe- and foliar cover (P = 0.226) estimates.
cies richness, and composition. Plants were Because differences among habitats ex-
identified to the species level allowing for isted before treatments were applied, pre-
further analysis by sub-class (i.e., grasses treatment densities or foliar cover estimates
and forbs). Unknown plants were collected were used as covariates in analysis of
in the field and numbered for later identifi- covariance (ANCOV A) for subsequent
cation. analyses. Litter and basal area were
analyzed using ANOV A. All pre-treatment
Statistical Analysis data for total density, foliar cover, and spe-
Analysis of variance (ANOV A) and cies richness were normally distributed ex-
mean separation were used to determine cept for foliar data in the MC zone. Littertreatment effects within and across habitats data were normally distributed in MC and '
for total density and foliar cover. Habitat PG habitats, but failed to meet normality in
effects were tested using the Type III mean the PJ zone. Attempts to normalize these .
square for block (habitat) as an error term. data via transformation were unsuccessful
Potential block (exclosure) X treatment in- and litter results for the PJ habitat type
teractions were tested using Tukey's test should be interpreted with caution.
for non-additivity. When sub-divided by
grass and forb growth classes, density data Habitat Effects
and foliar percentages that were not nor- A habitat effect (F2,10 = 15.39, P =
mally distributed were transformed using 0.001) was detected for density data with
square root or arcsine transformations, re- more plants/m2 in MC than in either PG or
spectively(SokalandRohlfI995). Experi- PJ habitats. There was a habitat by tram-
mental units which lacked a grass or forb pIing interaction for foliar cover (F 6,110 =
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ALCES YOLo 37 (1). 2001 RUPPET AL. -ELK GRAZING INTENSITY
30
2S H.bltatii" --MC
':" 20 --PG.~ .& .PJ
U.! 15'0II.
C.10i --
5
.H M L N
Trampling Intensity
Fig.3. Adjusted mean foliar cover (%) by habitat in response to trampling intensity (Spring 2000).The trampling X habitat interaction was significant(F 6,110 = 3.23,P= 0.006). Trampling was applied
at 100 (heavy), 25 (moderate), 5 (light), or 0 (none) footfalls per unit area.
3.23, P = 0.006) indicating that trampling intensity for density measures. Mean sepa-treatments were not having the same effect ration of adjusted means indicated that heav-in each habitat (Fig. 3). Moderately tram- ily clipped plots had higher plant densitiespled experimental units in PG sites had than moderately clipped or unclipped plotssignificantly higher foliarcover(X =25.7%) (Table 1). There was a trampling effectregardless of clipping intensity. Incontrast, (F343 = 2.33, P = 0.088) on foliar cover.moderately trampled plots in the MC habitat Moderately (X = 10.1 %) trampled plotshad less foliar cover (X = 6.7%) than any had less foliar cover than lightly trampledother trampling treatment regardless of clip- units (X = 12.9%, P = 0.031), but heavilyping intensity. No other significant differ- (X = 10.4%) and non-trampled (X =
ences were detected in density or foliar 12.1%) areas were not different from eithercover for clipping, trampling, or their inter- one.action across all habitat types. Analysis by vegetative type revealed an
effect (F 3.43 = 2.50, P = 0.072) of trampling
Pinon-Juniper Habitat intensity on total forb cover but not on grassWe detected a clipping effect (F 2,43 = cover. Lightly trampled plots had higher
3.55, P = 0.038) regardless of trampling forb cover than heavily trampled and mod-
, .5 ~ ~~=;~~Z' . ., .. ., .
-..'~4 ~...' '.' ."~ -..'> .-~ .' --'-"0 3 =-- ,u .--'.~ .'
~ 2 p. 0.059 _High Trampling
--Low Trampling
1 .& -Mod.rats Trampling
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0H M N
Clipping Intensity
Fig. 4. Mean foliar cover (%) of grasses for different intensities of clipping X trampling treatmentcombinations in mixed-conifer exclosures (Spring 2000) -Bandelier National Monument, NewMexico. Clipping was applied at 0 (none), 40-60 (moderate), or 100% (heavy) standing cropremoval whiletramplingwasappliedatO (none), 5 (light), 25 (moderate), or 100 (heavy) footfalls/
unit area.133
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138
ALCES YOLo 37 (1), 2001 RUPP ET AL. -ELK GRAZING INTENSITY
~ ~ ~ ~ ~ "} 0') plant was significantly less in 2000 than in~-I,o--O- 1999 (Fi.4S= 27.06, P < 0.001). No other~ effects for clipping, trampling, or their inter-
~ ~ ~ ~ ~ ~ ~ ~ action were detected for any other variable.~ Shifts in species composition were pro-
1,0 0 S nounced (Table 4). Wild strawberry~ ;;; ~ I ~ ~ ~ 8 (Fraga ria americana) decreased in rela-
~ tive composition at intermediate levels of~ ~ 0 10; 1,0 IrI ] clipping and trampling, but increased at the~ :::) I"'i I ~ oo:r= N 8: extremes. White clover (Trifolium repens)
~ increased (+4.8%) at the highest trampling~ ~ I") ~ ~ 0') OC! ~ intensity, but decreased at all other levels..-M N -0 -:E In addition, white clover increased 2.7% in
S' non-clipped units, but decreased about 2.5%~ !3 ~ ~ ~ ~ ~ ~ when moderate or heavy clipping was ap-
::a plied. The relative contribution of0'1 ~ IrI ~ bluegrasses (Poa spp.) increased with in-~ ~ ~ I ~ § I ~ creasing clipping intensity (+ 1.0%, 1.2%,
~ and 3.7% for none, moderate, and heavy~ ~ ~ I ~ ") I go clipping, respectively). Moderate intensitiesM -IrI -N ~ of clipping and trampling increased the rela-
..§ tive contribution of sedges (Carex spp.).B Pussytoes (Antennaria spp.) increased with
~ ~ ~ ""' 0') 1,0 ~ increasingclippingintensity(+1.0%,+1.2%,andMIrI .-,~ ..Q) .~ -M ---N ~ +4.2%fornone,moderate,andheavyclippmg,
! respectively). Heavy intensities of clipping in-~ ~ 0') 10; ~ 0; I") =oQ) creased the relative contribution of fleabanesM-MO-MN
~ (Erigeron spp.) (+4.9%) and Western yarrow~ (Achillea lanulosa) (+ 1.1 %). However, when
-IrI 0~ ~ ~ ~ ??i ~ ~ ~ ~ combined with the heaviest intensity of tram-
e ~ pIing, Western yarrow increased 0.8% in rela-1,0 r-- g .§ tive composition compared to a 4.7% decrease0\ roo: IrI r-- 00 0'1 1,0 ~.. h 1.. 1. 1. dN -NO"" I"'i N 6 8. w ennoc Ippmgortramp mgwasapp Ie .
0 '"1,0-,-~ -' 0; 0; ~ "} OC! ~~ ~ DISCUSSION
.M -IrI -N N -~ ~ During this study, BAND experienced
~ ~ two unseasonably warm years. Plant com-IrI 1,0 ~ ~ ~ ... fl d h .
f;:EJ: :!:J ~ ~ ~ ~ ~ 0' c murntIesarem uence asmuc , I not more,~ ~ by abiotic variables (e.g., inter-annual differ-
+-' §.~ ~ ~ ; ences ingrowing season precipitation) than by~ .~ '" ~ ~ -~ ~ ~ ungulate populations (Peterson et al. 1997).Q) -;:: c ~ C" -;:; Co ...~ ~.ij E ~ 1i; e go C Winkel and Roundy (1991) found seedling
~ ~ ~ :- ~ ~ '" IrI ..= 8. 5:0'~ e. § ~ ~ '" ~ ""' emergence m response to cattle tramplmg0... ~ ~ .-~ '" ~ ...£ d.f~ d d 1 .u~ § § ~ ~ ~ .t: .~ .5 ~ e I tere among years an treatments re atIve~""CE:~~~~' ...Q) ... d . d f .
1~ §] ~ ~ .§ ~ .~ .~ e: -g to precIpItation patterns an peno s 0 avaI-~ !5 '5 ~ .E ~ '0 "§ ~ b ~ able water. Olson et al. (1985) indicated thatE-- ~~<.~~~~~ -'-'
139
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each species reacts to precipitation regimes in these sites. A clear explanation for thisand grazing pressure in a unique manner. is not available, although other studies have
Given the migrational behavior of elk, advocated use of grazing or trampling toelevationalpartitioning occurs in different sea- stimulate forage production (Savory andsons resulting in heavier use of certain habi- Parsons 1980, McNaughton et al. 1983).tats during some parts of the year. Impacts Though not supported by results in othercaused by clipping and/or trampling may be habitats, it is possible that moderateconfounded when looking at individual plant intensities of clipping and trampling comple-species or differing precipitation regimes ment each other providing optimum grow-(Olsonetal. 1985; Cole 1995a,b, 1998) all of ing conditions for grasses in MC habitats.which vary from one elevational zone to an- One result that appeared to be consist-other. This may be somewhat illustrated by ent regardless of habitat was the effect ofthe inconsistent, but significant habitat X tram- clipping intensity on total litter cover, LesspIing interaction we detected for total foliar litter cover was found in heavily clippedcover. Moderatelytrampledunitsinponderosa plots in PJ and MC exclosures. A negativehabitats had 2.5 times more foliar cover than correlation of grazing intensity to litter coverin PJ, and nearly 4 times more than in MC has been documented elsewhere (Biondinisites. However, within habitat analysis in PG et al. 1998). Litter plays a crucial role indid not reveal any trampling effects on foliar ecosystems as a source of organic materialcover whereas a significant effect was de- and reducing soil erosion (Biondini et al.tected in Pl. 1998).
Plant densities were higher in heavily Measures of basal area did not changeclipped plots in PJ habitat versus moderately with this first year's treatments and speciesor non-clipped experimental units. It is possi- richness was only affected by treatments inble that bunchgrasses in PJ sites responded to MC sites where heavy intensities of tram-heavy clipping pressure coupled with above pIing resulted in fewer species. Such incon-average seasonal temperatures and lower sistencies or lack of response can be ex-moisture with a breakup of the original plants, plained in two ways. First, only a singlewhich were then counted as more individual year has elapsed between initial treatmentplants the following year. Trampling applied applications and the resultant data collec-to those plots exacerbated this effect by pul- tion reported here. Much longer time peri-verizing the dead or dying connective portions ods-periods in the range of20 years -may
.of bunchgrasses. However, the dominant be needed to detect some vegetative re-species in this habitat type was blue grama, sponses to changes in grazing pressurewhich is deemed to be tolerant of grazing and (Chong 1992) especially in ecosystems that
, trampling (USDA Forest Service, Fire Ef- have developed with a history of grazingfects Information System, http:// pressure. Changes in basal cover for indi-www.fs.fed.us/database/feis, March 12, vidual plant species may be highly suscep-1998). tible to precipitation (Olson et al. 1985)
Intensity of clipping did not have any indicating that dominant species and theirdetectable effect on overall plant densities response to precipitation fluctuation need toin PG habitat; however, clipping appeared be identified over the long-term prior toto interact with trampling intensity in MC evaluating grazing/trampling effects. Sec-sites. Moderately grazed and trampled ondly, all vegetative parameters measuredunits tended to have relatively higher grass had high intrinsic variability.cover than any other treatment combination At lower elevations blue grama in-
141
ELK GRAZING INTENSITY -RUPP ET AL. ALCES YOLo 37 (I), 2001
creased with a subsequent decrease in Forest Service 1937), but it is known to bemountain muhly. Blue grama is known to be less tolerant to clipping at higher tempera-tolerant of grazing (Santos and Trlica 1978, tures than blue grama (Boryslawski andBock and Bock 1986) and may even in- Bentley 1985). To date our results supportcrease in overgrazed range (USDA Forest this observation.Service, Fire Effects Information System, Other notable shifts in species compo-http://www.fs.fed.us/database/feis, March sition in PG included the disappearance of12, 1998). In contrast, mountain muhly is goosefoot species and an increase in trailingconsidered intolerant to grazing (Arnold fleabane. Trailing fleabane is relatively1950). In an Arizona study using long-term poor forage because of its ground-levelexclosures, Arnold (1950) indicated that growth form and generally increases onmountain muhly showed the greatest in- grazed lands (U.S. Forest Service 1937).crease in ungrazed quadrats, occurred in The disappearance of goosefoot species in"patches" when moderately grazed, and our sites cannot be explained because of adisappeared when overgrazed. Similarly, in lack of information on responses to grazingColorado cover increased as grazing de- and trampling in the literature. However,creased (Johnson 1956) comprising 20% of treatments were applied at the earliest partthe composition in ponderosa habitat on of the growing season when these plantsheavily grazed areas compared to 45% on were seedlings and were probably unable tothose not grazed. Results of this study tolerate such extreme conditions.support these patterns. Arizona three-awn decreased in rela-
Seasonal progression of environmental tive composition when heavy clipping orvariables and phenological development of trampling was applied, but increased onindividual plants may confound effects of non-treated units. Little information existsdefoliation intensity (Briske and Richards in the literature regarding response to graz-1995). Climate may confound interpreta- ing pressure, but it is generally thought totion since blue grama is more commonly have poor forage value because of its promi-known to be drought-tolerant (U.S. Forest nent awns (U.S. Forest Service 1937). InService 1937; Menke and Trlica 1981; mixed-conifer regions, noticeable shifts inUSDA Forest Service, Fire Effects Infor- relative composition occurred with white-mation System, http://www.fs.fed.us/data- clover, bluegrasses, sedges, and pussy toes.base/feis, March 12, 1998) -a condition White clover is considered excellent foragewhich appears to be prevalent the last cou- for ungulates (USDA Forest Service, FirepIe of years in this region of the Jemez Effects Information System, http://Mountains. Boryslawski and Bentley (1985) www .fs.fed. us/database/feis, March 12,reported an interaction between tempera- 1998) and withstands trampling well (U.S.ture regime and clipping treatment with blue Forest Service 1937), but it is not tolerant ofgrama being less sensitive to clipping at drought conditions (Gibson and Cope 1985).higher temperatures than western Our results support this observation withwheatgrass. the greatest relative increases in white clo-
At mid-elevational ponderosa grassland ver occurring at the heaviest intensity ofsites, western wheatgrass proliferated in trampling. Though not evident with thisresponse to moderate levels of trampling. study, plants can adapt to severe defoliationWheatgrass is drought- and grazing-toler- by developing smaller leaves and moreant and is good winter forage for elk and stolons (Ryle et al. 1989) and it has beenmule deer (Odocoileus hemionus) (U.S. reported that this plant may grow stronger
142
ALCES YOLo 37 (I), 2001 RUPP ET AL. -ELK GRAZING INTENSITY
and bulkier (i.e., become more robust) when heavily trampled sites. Finally, MC sitesgrazed (U.S. Forest Service 1937, Hay et had more species in lightly trampled loca-al. 1989, Chapman et al. 1992). In addition, tions compared to heavily treated areas, butwhite clover is a species with a high degree not when compared to moderately or non-of phenotypic plasticity that can result in trampled quadrats. In total, these observa-large fluctuations in size of individual plants tions suggest that there may be an interme-(Hay et al. 1989). diatethreshold at which trampling may stimu-
Individual species of Carex, Poa, and late plant productivity, especially in terms ofAntennaria respond to grazing pressures forb response.
.and climate differently (U.S. Forest Serv- Similar responses to trampling have beenice 1937) making it difficult to interpret our reported in the literature. Cole and Spildieresults which are based on generic classifi- (1998) concluded forb-dominated sites were
.cations. In general, Poa spp. are known to highly vulnerable to trampling effects, butbe good to excellent forage and resistant to recovered rapidly. The ability of a vegeta-heavy trampling, grazing, and drought con- tion type to tolerate recurrent tramplingditions (U.S. Forest Service 1937, disturbance may be more a function toStubbendieck et al. 1985) because growing recover from damage than its ability topoints are below ground throughout the resist being damaged (Cole 1995a, b). Colegrowing season for most species (Ehrenreich (1995a, b) further stated that certain veg-and Aikman 1963). Results from this study etation types might exhibit thresholds ofsupport these observations as Poa spp. vulnerability in response to trampling that,increased with increasing clipping intensity. when exceeded, may result in even greaterSimilarly, Carex spp. did not appear to be damage to the plant.negatively impacted by grazing and tram- There are 3 explanations for the vari-pIing treatment combinations. Intermediate able results we found in this study. First,intensities of clipping and trampling in- there may be a possibility that heavy wintercreased the relative contribution of Carex and variable spring grazing, with associatedin our study and it did not appear to benefit trampling, may not cause extensive plantwhen protected from grazers. Likewise, mortality or progressive changes in basalAntennaria spp. increased with clipping area (Houston 1982), especially during dor-intensity. One species, A. parvifolia, has mant phases of plant life cycles. Secondly,been shown to decrease slightly under light much longer time periods (periods in the
.to moderate grazing, but increase in heavily range of 20 years) may be needed to detectgrazed areas (Smith 1967). In ponderosa vegetative responses to changes in grazingcommunities, it has also been shown to pressure (Chong 1992), especially in eco-
, survive heavy trampling (Smith 1967). systems that have developed with a historyTrampling, in general, more consist- of grazing pressure. Finally, the amount of
ently affected variables. In PJ communi- inherent variability present in the vegetativeties, moderately trampled plots had less communities of BAND may have precludedtotal foliar cover than lightly trampled units. detection of changes.Further inspection indicated that lightly tram-pled treatments had significantly higher forb ACKNOWLEDGEMENTScover in this community. In contrast, mod- We would like to thank Cindy Caplen,erately trampled units had a higher density Erika Hersch, Salinda Daley, Doug Krantz,of plants than non-trampled areas in PG, but Christine Evans, and Eric Wolf for theirdensities were not different from lightly or assistance in the field as well as Bandelier
143
ELK GRAZING INTENSITY -RUPP ET AL. ALCES YOLo 37 (1), 2001
National Monument for their financial and Journal of Ecology 73: 113-121.research assistance. This is Texas Tech BRISKE, D. D., and J. H. RICHARDS. 1995.University, College of Agricultural Sciences Plant responses to defoliation: a physi-and Natural Resources technical publica- ological,morphologicalanddemographictionT-9-892andLosAlamosNationalRe- evaluation. Pages 635-710 in D. J.search Laboratory publication LA-UR-Ol- Bedunah,editor. Wildland plants: physi-1955. ological ecology and developmental mor-
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146
CONTENTS
FOREWORD i
JOURNAL NEWS ,., "'" ii
IN MEMORIAM -Eric Wynn Cox """""""""'."""""""""" iii
SUMMER FOOD HABITS OF GRAY WOLVES IN THE BOREAL FOREST OF THE LACJACQUES-CARTIER HIGHLANDS, QUEBEC
Jean-Pierre Tremblay, Helene Jolicoeur, and Rolland Lemieux 1
ACCURACY IN MOOSE MANDIBLE SIZE VERSUS TOOTH WEAR ASSESSMENTS'.'..'..'..."...'...".""'.".' Brian McLaren and Richard Curran 13
MOOSE HUNTERS' PERCEPTIONS OF FOREST HARVESTINGRehaume Courtois, Jean-Pierre Ouellet, and Anne Bugnet 19
MOOSE HUSBANDRY AT THE COLUMBUS ZOO: THE NUTRITION ASPECTLori Monska 35
MODELING MOOSE SIGHTABILITY IN SOUTH-CENTRAL BRITISH COLUMBIAJames F. Quayle, A. Grant MacHutchon, and Douglas N. Jury 43
LOCAL COMMUNITY BASED MOOSE MANAGEMENT PLANS IN NORWAYJohan Danielsen 55
REDUCED COST OF REPRODUCTION IN MOOSEALCESALCESTHROUGH HUMAN
HARVEST Goran Ericsson 61
AN ASSESSMENT OF CATCH PER UNIT EFFORT TO ESTIMATE RATE OF CHANGEIN DEER AND MOOSE POPULATIONS Ian W. Hatter 71
CHANGES IN THE RELATIONSHIP BETWEEN PALMATE AND CERVINE ANTLERS INMOOSE (ALCESALCES) IN SOUTHEASTERN NORWAY Jens H. Engan 79
FOREST OWNERS AS MOOSE HUNTERS IN FINLANDRisto Heikkila and Jukka Aarnio 89
THE ECONOMIC VALUE OF MOOSE IN NORWAY-A REVIEW..., Torstein Storaas, Hege Gundersen, Hege Henriksen, and Harry P. Andreassen 97
SEXUAL SEGREGATION IN MOOSE: EFFECTS OF HABITAT MANIPULATIONR. Terry Bowyer, Becky M. Pierce, Lawrence K. Duffy, and Dale A. Haggstrom 109
PECULIARITIES OF DAILY MILK PRODUCTIVITY OF PECHORA TAIGA DOMESTICATEDCOW MOOSE AND THEIR INTERCONNECTION WITH REPRODUCTIVE FUNCTION
Tatyana F. Vasilenko, Irine N. Sivoxa, Mikhail V. Kozhykhov, and Patrick R. Lemons II 123
EFFECTS OF SIMULATED ELK GRAZING AND TRAMPLING (I): INTENSITYSusan P. Rupp, Mark C. Wallace, David Wester, Stephen Fettig, and Robert Mitchell 129
EFFECTS OF SIMULATED ELK GRAZING AND TRAMPLING (II): FREQUENCY, Susan P. Rupp,
Mark C. Wallace, David Wester, Stephen Fettig, and Robert Mitchell 147
CO-MANAGEMENT -THE MANITOBA EXPERIENCE Vince Crichton 163
GENETIC VARIATION OF MICROSATELLITE DNA IN MOOSE IN QUEBECMatthew A. Cronin, John C. Patton, Rehaume Courtois, and Michel Crete 175
REPRODUCTIVE LIFE HISTORY AND FERTILITY OF MOOSE IN NORTH ASIAN.K. Zheleznov and L.M. Fox 189
(Continued on inside back cover)
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