Zilverberg, Cody, W. Carter Johnson, Arvid Boe, Vance Owens, David Archer, Craig Novotny, Malia ...

12 Pages·2014·0.72 MB·English

Wetlands
DOI10.1007/s13157-014-0548-8
ORIGINALRESEARCH
Spartina pectinata
Growing in Previously Farmed Prairie
Wetlands for Economic and Ecological Benefits
CodyJ.Zilverberg&W.CarterJohnson&ArvidBoe&
VanceOwens&DavidW.Archer&CraigNovotny&
MaliaVolke&BrettWerner
Received:11December2013/Accepted:14May2014
#SocietyofWetlandScientists2014
Abstract WetlandsinthePrairiePotholeRegionoftheU.S. second experiment, 2 years after establishing plants by
arethreatenedbycontinueddrainageandconversiontocrop- transplanting at 0.9- or 1.5-m spacing, biomass no longer
land.Commercialincentivesmayincreasewetlandrestoration differedbetweentreatments.Oureconomicanalysisindicated
in lieu of easements. Therefore, we evaluated two commer- establishment costs could be recovered with < 10 years of
cially available populations of prairie cordgrass (Spartina biomassandseedharvests.Becauseprairiecordgrasscanbe
pectinata Link) by comparing two planting techniques and establishedusingconventionaltechniquesandprovidesposi-
identifying zones ofmaximum plantvigor and biomasspro- tivenetrevenue,itshouldbeconsideredforincorporationinto
duction along a wetland-upland environmental gradient of a shallowwetlandsinproductionfields.
restored temporary wetland in east-central South Dakota. In
thewetlandcenter(maximumwaterdepth:0.4–0.5m)plants Keywords Biomass .Biofuel .Wildlife .Establishment .
wereeffectivelyestablishedbytransplanting,butnotbydril- Transplant .Agroecology.Conservation
ling.Bothtechniqueswereeffectiveabovethewetlandcenter.
Thezoneofmaximumvigorvariedbyyear,rangingfromthe
wetland bottom (0.5-m maximum water depth) to 0.25 m Introduction
above the wetland-upland boundary. Biomass yield did not
differbetweenpopulationsbutwasaffectedbyelevation.Ina Wetlands are among the most transformed ecosystems on
earth(MitschandGosselink2000;BatzerandSharitz2006).
Wetland drainage, primarily by ditching and tiling, has ex-
Electronicsupplementarymaterial Theonlineversionofthisarticle pandeduplandagricultureintolowgroundthatwasprevious-
(doi:10.1007/s13157-014-0548-8)containssupplementarymaterial,
lyunsuitableduetofloodingandsedimentation(vanderValk
whichisavailabletoauthorizedusers.
: : 2012). While expansion of cropland area into lowlands has
C.J.Zilverberg(*) W.C.Johnson M.Volke
hadshort-termeconomicbenefits,lossesofecosystemgoods
Dept.ofNaturalResourceManagement,SouthDakotaState
andservicesintheformofbiodiversity,fishandgamehabitat,
University,Brookings,SD,USA
e-mail:[email protected] floodattenuation,surfaceandgroundwaterpurification,stock
: watering, and carbon storage have been recognized and in
A.Boe V.Owens
somecasesquantified(Galatowitsch2012).
Dept.ofPlantScience,SouthDakotaStateUniversity,Brookings,
Wetlands in the American Midwest, including the Prairie
SD,USA
PotholeRegionofcentralNorthAmerica,whichwasidenti-
D.W.Archer fiedasaglobalconservationpriority(Keddyetal.2009),have
AgriculturalResearchService,UnitedStatesDept.ofAgriculture,
beendecimatedbydrainageforagriculture(Prince1997).The
Mandan,ND,USA
subregions most favorable for agriculture had lost the large
C.Novotny majorityoftheirwetlandsbythemid-20thcentury;currently,
EcoSunPrairieFarms,Brookings,SD,USA Iowaandwestern Minnesota haveretainedonlyseveralper-
centoftheirhistoricprairiewetlands,whiledrierareasfarther
B.Werner
west(theDakotas)thatare lesssuitableforgrainproduction
PrograminEnvironmentalStudies,CentreCollege,Danville,KY,
USA haveretainedabout halfoftheirhistoricwetlands(Dahland
Wetlands
Johnson1991).Despitediscoveryofthebenefitsofwetlands switchgrassonwell-drainedfarmland.Boeetal.(2009)noted
tosocietyandpassageoffederalprotectionlawsintheUnited the need for gradient studies to determine the optimal
States,manyofthefewremainingwetlandsandsurrounding topographic and edaphic position for planting and growing
grasslandsimportantforwildlifehaverecentlybeenconverted cordgrass.
to farmland in response to record grain prices (Tiner 2009; Cordgrassmaybepropagatedbyseed,orvegetativelyby
Johnston2013;WrightandWimberly2013). dividingandplantingrhizomes.FraserandKindscher(2001)
Whileprotectionoftheremainingwetlandsmustremaina successfully transplanted cordgrass plugs from an existing
high conservation priority, restoration isincreasingly needed wetland into an eastern Kansas floodplain using a tractor-
to recover lost ecosystem goods and services and to avoid mountedtreespade,butfoundthatsuccesswasmediatedby
extirpationandextinctionofspecies.Prairiewetlandrestora- water depth. Though effective, transplanting plugs from
tion projects thus far have had limited success; function has existing wetlands is probably not practical for large scale
beenachievedmorethanbiodiversity(Galatowitschandvan plantings.Alternativemethodsofestablishingcordgrassfrom
derValk1994;vanderValk2012).Governmentorganizations seedmustbefound.
are common partners in restoration projects contributing Littleinformationexistsforthecultivationofcordgrass.In
funds, establishing policies, and passing laws; however, be- addition, the Red River population was the only
cause of the “start-stop” nature of public funding, lack of commercially-available seed (Jensen 2013) until the Prairie
policycontinuity,andcurrentbudgetcrises,governmentsup- Farm population was released in 2011 by EcoSun Prairie
portmaybelessassuredinthefuture(Galatowitsch2012). Farms. Red River was released by the United State Depart-
An alternative approach to stimulate restoration has been mentofAgriculture(USDA)NaturalResourcesConservation
adoptedbyEcoSunPrairieFarms,anon-profitSouthDakota Service (NRCS) Plant Materials Center in Bismarck, North
corporation. Their approach is to generate income from the Dakota and is a composite of plants from eastern North
sale of grassland products, including those from restored Dakota, western Minnesota, and northeastern South Dakota
wetlands, to pay for the costs of restoration and to produce (NRCS 2012). Because cordgrass is native to most of the
profitablefarmingoperationsbasedonperennialcrops.More United States, the small, northern geographic region from
than a million farmed wetland basins in the eastern Dakotas whichRedRiverwasselectedleavespotentialtomakeaddi-
currentlyunderconservationeasementprotectionbytheU.S. tional selections that might outperform Red River in other
FishandWildlifeService(KurtForman,personalcommuni- locations. The Prairie Farm population originated from seed
cation, U.S. Fish and Wildlife Service) are potentially avail- collectedfromanaturalpopulationinthesoutheasterncorner
able for restoration and commercial production. These wet- ofSouthDakota.
lands are often too wet tobe planted to annualcrops and, if This paper reports on two experiments conducted at the
planted, frequently yield poorly due to saturated soil condi- EcoSunPrairieFarm:onecomparesvigorandbiomassyield
tions.Ifplantedtoperennialwetlandplantswithcommercial of the two populations of cordgrass for which seed was
value, they could be managed to regain some of the former commercially available to determine how drilled seed or
goodsandserviceslostbyrepeatedtillage. hand-planted plugs grown from seed in the greenhouse
Fundamentaltothesuccessofthisapproacharethechoices responded to a strong environmental gradient from wetland
made among commercially-available species and ecotypes, bottom to upland habitat. In a second experiment, we com-
identifying the optimal positioning of plants along environ- pared biomass of two transplant densities to determine how
mentalgradients,anddeterminingeffectivemethodsofestab- rapidly cordgrass spread vegetatively and filled interplant
lishmentonlow,oftenwet,ground.Prairiecordgrass(Sparti- spacesinatemporarywetland.
napectinataLink;hereaftercordgrass)wasoneofthespecies
chosen for planting experiments during the restoration of
formerly drained shallow wetlands on EcoSun’s “Prairie MaterialsandMethods
Farm.” Cordgrass is native, vigorously competitive, often
dominant in temporary and seasonal wetlands in the Prairie GradientExperiment
Pothole Region, and has commercial value as seed and bio-
mass (hay and future biofuel feedstock) (Dix and Smeins TheresearchsitewaslocatedattheEcoSunPrairieFarmnear
1967;Johnsonetal.1987;BoeandLee2007).Prairiecord- Colman,SD(44.029,−96.850).Theexperimentwasconduct-
grass biomass yieldsof 14Mg ha−1 measured on temporary ed in a shallow basin (1.4 ha) classified as a temporary
wetlandsonEcoSun’sPrairieFarmwerecomparableto‘Sun- wetland(StewartandKantrud1971)thattypicallyfillsupto
burst’,‘Summer’,and‘NE28’switchgrass(Panicumvirgatum a 50-cm depth with runoff in spring and dries out by mid-
L.) yields in nearby uplands on productive cropland soils summer. Wetland soils included Worthing (fine, montmoril-
(Zilverberg etal.2014).Boe andLee (2007) foundduringa lonitic, mesic, Vertic Argiaquolls) in the basin, Chancellor
4-yearsexperimentthatcordgrassproductionexceededthatof (fine, montmorillonitic, mesic Vertic Argiaquolls) in the
Wetlands
swale, and Wakonda (fine-silty, mixed, mesic Aquic (7.5kgPLSha−1).Noherbicideortillagewasusedthrough-
Calciustolls) on the ridge surrounding the wetland, as inclu- outthe experiment, but the wetland wasmowed onceabove
sionsinthesoilassociationWentworth-Chancellor-Wakonda thegrassheighttocontrolannualweedsduringtheestablish-
silty clay loam with 0 to 2% slopes (NRCS 2011). Mean mentyear.
annualprecipitation(1981to2010)attheMadison,SDweath- SamplingoccurredinOctober-Novembereachyearbegin-
erstationwas655mm,with495mmfromApriltoSeptember ning in 2011, the second growing season, and continuing
(NOAA 2013). The wetland had been cultivated for annual through2013.Becauseoferraticestablishmentinsomesub-
crops for a century or more prior to its restoration by this plots,wevisuallydeterminedwhichrowofthethreerowsof
experiment. In the year prior to planting, the field contained eachsubplothadthemostuniformstandfromthecenterofthe
soybeans and post-harvest stubble remained at the time of wetland to beyond the wetland-upland border, and used that
planting cordgrass. Four sampling transects oriented north- row for all sampling except biomass. Plant height (distance
west,northeast,southwest,andsoutheastwereestablishedin from ground to top of natural leaf blade height), maximum
an“X”patterninthewetlandbasin(Fig.1).Transectsbeganat inflorescence height (distance from ground to top of tallest
thebottomofthebasinandextendeduptheslopesbeyondthe inflorescence), and numberofinflorescencesweremeasured
50-cmdepthcontourandintoplanteduplandvegetationdom- or counted within a 1 × 1 m quadrat at 2-m intervals along
inated by big bluestem (Andropogon gerardii Vitman). Dif- eachtransectfrom2011to2013.Establishmentsuccesswas
ferentslopesinthefourdirectionsresultedindifferenttransect defined as at least one cordgrass tiller within a sampling
lengths (57 to 83 m). Each transect was divided into two quadrat.Aplantvigorindexwascreatedusingthefollowing
contiguous plots that were randomly assigned to planting equation:
type:drillingorplugging.Eachplotwasfurtherdividedinto
2subplots,eachrandomlyassignedtoapopulation:RedRiver
Vigor¼½PH=maxðPHÞþIH=maxðIHÞþNI=maxðNIÞ(cid:2)=3
orPrairieFarm.
Cordgrass plants of both populations were started from
seed in cone-shaped containers (“cone-tainers”; Stuewe &
Sons, Tangent, OR) in a greenhouse in the spring of 2010. wherePHisplantheight,max(PH)isthemaximumPHofany
PrairieFarmplugsweretransplantedtothefieldon26May. sample,IHisinflorescenceheight,max(IH)isthemaximum
Transplanting of Red River was delayed until mid-late June IHofanysample,NIisthenumberofinflorescencesm−2,and
becauseofpoorplantvigorduetogrowingconditionsinthe max(NI)isthemaximumNIofanysample.
greenhouse. Eachtransplantsubplotconsisted ofthreerows, Biomasssamplingwasconductedin2013.Foreachtran-
with inter- and intra-row plant spacing of 0.9 m. Drilled sect, one point was randomly selected within each ~0.08-m
subplots also consisted of three rows, with two rows spaced change in elevation from 0 to 0.40 m elevation, and 2 addi-
at0.8mandtworowsspacedat0.6mbecauseofequipment tionalpointswererandomlyselectedintheremaining,upper
restrictions.On22April2010,bothpopulationswereplanted elevations. At each sampling point, all four treatments were
usinga1.6-mwideTruaxFLXII-88grassdrill(TruaxCom- sampledbycuttingprairiecordgrassatgroundlevelbyhand
pany; New Hope, MN) at a rate of 10 kg bulk seed ha−1 withacurved,serratedblade(riceknife)withina1.5×1.0-m
Fig.1 Left,overheadimage(toscale)oftheexperimentinarestoredtemporarywetlandattheEcoSunPrairieFarm.Right,plotdiagramshowinglayout
ofdifferenttreatments(nottoscale)
Wetlands
quadrat(N=84).Thequadratwascenteredonthemiddlerow inthecenterofthewetlandswaspulledbyhandinMay-June
ofeachtreatmentandthequadrat’swidthensuredthatallthree of2011and2012.
rowsweresampled.Inter-rowandinter-plantspaceshadbeen Wetland biomass was determined by cutting samples at
filled in by new tillers, so that rows were no longer distinct ground level with a rice knife in autumn before seed was
fromoneanotherinmanylocations.Speciesotherthanprairie harvested. In 2009, the year after establishment, individual
cordgrasswereexcludedfromsamples.Inthewetlandbasin, plantswerestill discernible and wereharvested individually.
the most common other species were river bulrush Insubsequentyears,plantshadgrowntogether,soallbiomass
(Schoenoplectusfluviatilis[Torr.]M.T.Strong),dock(Rumex within1-m2quadrats,includingplantsotherthanprairiecord-
maritimus L.), cocklebur (Xanthium strumarium L.), and grass, was harvested. Wetlands were divided into multiple
smartweed (Polygonum coccineum L.). In the uplands the zones of equal width, and one east–west sampling transect
most common species was big bluestem. Other species pro- was randomly located within each zone. Each transect was
videdlittlegroundcoverexceptatelevationextremeswhere further divided into subzones of equal width, and one sam-
prairiecordgrassdidnotperformwell.Biomasssampleswere plingquadratwasrandomlylocatedwithineachsubzone.The
weighedinthefield.Subsamplesweredriedandweighedto eastwetlandwassampledeveryyearfrom2009to2013.The
estimate percentage dry matter. Elevation above the wetland westwetlandwassampledin2009and2011only.Ameanof
bottom was measured at 2-m intervals along transects using 24quadratswetland−1year−1werecollected,foratotalof165
conventionalsurveyequipment. samples.
Abandofthewetlandnearthe0.5-melevationcontourwas
drilledwithPrairieFarmatthesametimeexperimentaltran- StatisticalAnalysisofGradientExperiment
sectswereestablished.Thenorthernportionofthisbandwas
sampledinautumn2011bycuttingatgroundlevelwithin1- Establishment success of all treatments was plotted against
m2quadrats(N=16).Resultsofthissamplingwerenotstatis- elevation.Anelevational‘threshold’wasvisuallyidentifiedat
tically analyzed but are presented as yield estimates under 0.1m;below0.1m,successwaslowbutabove0.1msuccess
larger-scaleproduction.Yieldsfromthisbandwererepresen- wasalmostcertain.Dataweregroupedbyplantingtechnique,
tativeofapproximately1/3ofthewetlandwhereyieldswere population, elevation (above or below 0.1 m), and year, and
greatestandthereforecannotbeextrapolatedtotheentire1.4- percentageofsuccessfulsamplingpointswascalculated.Red
hawetland. Rivertransplantdatawereexcludedfromthisanalysisandall
others because of poor vigor relative to Prairie Farm at
TransplantDensityExperiment transplanting.
Foranalysisofvigor,plantheight,andinflorescenceden-
Thetransplantdensityexperimentwaslocatedintwotempo- sity, samples without a cordgrass plant were not included.
rary wetlands (“eastern wetland” and “western wetland”) on Similarly,foranalysisofmaximuminflorescenceheight,sam-
thesamefarmapproximately0.75kmsoutheastofthegradi- ples without an inflorescence were not included. The loess
entexperiment.Maximumwaterdepthofbothwetlandswas functionofR(RCoreTeam2012)withaspanparameterof
approximately 0.4 m. Wetlands were 0.5 and 0.6 ha in size. 0.85wasusedtodrawsmoothedlineswiththelocalpolyno-
Thewetlandshadbeenfarmedinpreviousyearswithacorn mialtechniqueforeachplantingtechniquexpopulationxyear
(ZeamaysL.)-soybean(GlycinemaxL.Merr.)rotation.They combination,plottedwithvigoronthey-axisandelevationon
were prepared for planting by spraying glyphosate the x-axis. After line estimation, vigor was aggregated by
(N-[phosphonomethyl] glycine) at 4.7 L ha−1 on 21 May elevation groups of 0.05 m height before plotting points, to
2008.PrairieFarmcordgrassplantswerestartedinthegreen- improve interpretation of graphs. Range of maximum vigor
houseandtransplantedintothewetlandsbetween23Mayand foreachpopulationxplantingtechniquexyearcombination
10July2008. Eachwetland was divided intotwo plots,one wascalculated,withrangeofmaximumvigordefinedasthe
north and one south. Within each wetland, one plot was upperquartileofvigorvaluesaftertakingthemeanofvalues
randomlyassignedtoeachtransplantdensity treatment (0.9- withinelevation rangesof0.05 m. When a value was in the
or 1.5-m spacing). In October 2008, transplant survival was upper quartile but was at least 0.10 m from the rest of the
determined for all plants and percentage success calculated. upper quartile points, it was considered an outlier and not
Wetlandswereharvestedforseedintheautumnofeachyear includedinthemaximumvigorrange.
from2009to2012.Post-harvestresiduewasleftinthefield Dependent variables plant height, inflorescence density,
exceptin2011,whentheeasternwetland(0.5ha)wasburned and maximum inflorescence height were evaluated using
in autumn. In 2012, the western wetland was burned in the analysisofvariance.Theeffectofpopulationwasdetermined
spring.Canadathistle(CirsiumarvenseL.)wasspot-sprayed for drilled plots, with a model including population in the
with Milestone (2-pyridine carboxylic acid, 4-amino-3,6- main plot, elevation in the subplot, and year as repeated
dichloro-) as needed. Hybrid cattail (Typha X glauca Godr.) measure. Transect was considered a random blocking
Wetlands
variable.Theeffectofplantingtechniquewasdeterminedfor forcheckingandwateringplants.Alaborrateof$14.00per
thePrairieFarmpopulation,usingthesamemodelexceptthat hour(Lazarus2013)wasusedfortheanalysis,sototallabor
plantingtechnique replacedpopulationinthe mainplot. For costwas$126.40perthousandplants.Greenhousespacerent
theseanalyses,elevationwastreatedasacategoricalvariable wascalculatedusingarentalcostof$4.31m−2ofbenchspace
withfourbins:0to0.14,0.15to0.44,0.45to0.74,and0.75to permonthand3monthsofuse.Eachconerackwas0.186m2
1.25 m. For bins containing more than one sampling point, and held 98 cones, so 1.9 m2 bench space was used per
meanswerecalculatedbeforeanalysis.Descriptivesummary thousand plants for total rent of $24.60 per thousand plants.
statisticswerealsocalculatedwithoutaggregatingintoeleva- Seedcostwas$0.71perthousandPLS,basedonalocalretail
tionbins. priceof$276kg−1(JasonTronbak,personalcommunication,
Evaluation of the dependent variable biomass was also Millborn Seeds) and seed weight of 386,000 seeds kg−1.
carriedoutusinganalysisofvariance.Theeffectofpopulation Potting soil cost was $10.30 per thousand plants. Total cost
was determined for drilled plots, with a model including forproducingplantsfortransplantingwas$200.21perthou-
population in the main plot, elevation in the subplot, and sand plants. Based on actual labor use, transplanting in the
transectasarandomblockingvariable.Theeffectofplanting fieldrequired8.89hoflaborperthousandplants,or$124.50
technique was determined for the Prairie Farm population, perthousandplants.Basedonfieldrecords,itwasestimated
usingthesamemodelexceptthatplantingtechniquereplaced that, in the year after establishment, 198 h ha−1 was used to
populationinthemainplot.Elevationwasacategoricalvar- remove hybrid cattail by hand. For comparison, we also
iablewithsevenlevels. estimated costs to establish a cordgrass wetland by drilling
FixedmodelswereanalyzedwiththelmfunctionofR(R seed(7.5kgPLSha−1)ratherthantransplanting.
Core Team 2012). Mixed model analyses from both experi- Machinerycostsforspraying,seeding,andharvestingwere
mentswerecarriedoutusingthelme4(Batesetal.2012)and estimatedusingUniversityofMinnesotamachinerycostdata
nlme (Pinheiro et al. 2012) packages of R. Statistical tests (Lazarus2013).Thesecosts includedownership and operat-
frombothexperimentswereconsideredsignificantwhenp<= ingcostsforfarmequipment,includingoperatorlabor.Annu-
0.05. All data plots were created with ggplot2 version 0.9.3 almaintenancecostsincluded7.4hlaborand$0.99herbicide
(Wickham2009). ha−1.Sincecostsforestablishmentoccurbeforeanyincomeis
generated,costsandincomewereallaspresentvaluesrelative
StatisticalAnalysisofTransplantDensityExperiment totheestablishmentyearusingadiscountrateof4%.Cumu-
lative net present value was then annualized assuming a 10-
Years were analyzed independently because both wetlands year life and a 20-year life to provide annual net income
were not sampled in all years. For years in which both wet- estimates. Land rent that could have been earned in crop
landsweresampled,weusedamixedmodelwithbiomassas productionwasusedasacomparisontotheannualnetincome
thedependentvariable,wetlandasarandomeffect,andspac- fromgrassproductionusingthe2013countyaveragedryland
ing as a fixed effect. For years when only one wetland was croplandrateof$472ha−1(NASS2013).Thepaybackperiod
sampled, there was no random effect in the model. Samples foragrassstandtorecoverestablishmentcostswasindicated
wereconsideredpseudo-replicates. bythefirstyearthatcumulativenetpresentvaluewas≥0.The
payback period for a grass stand to exceed the opportunity
EconomicAnalysis costofcroprentwasindicatedbythefirstyearcumulativenet
presentvalueexceededthecumulativenetpresentvaluefrom
Apreliminary economicanalysiswasconducted toillustrate cropland.
thepotentialrevenuefromarestoredcordgrasswetlandatthe
two transplant densities and direct seeding. Major costs in-
cluded producing a plant for transplanting and transplanting
into the field. Costs to produce a plant included labor to Results
preparesoilandconesforplanting,plantingseeds,anddaily
watering. Other costs included greenhouse space rent, seed, Precipitation
pottingsoil,andcones.Coneswereassumedtobereusedfor
5 years, so were annualized to a single year at $38.20 per Precipitation in 2008, 2009, and 2011 was slightly below
thousand cones based on a purchase price of $170.00 per normal (Table 1). The establishment year of the gradient
thousand cones and using an interest rate of 4 %. Based on experiment,2010,receivedabove-normalannualandgrowing
actuallaborusedinproducingplantsforthetransplantdensity seasonprecipitation(Table1;Fig.2).Thesummerofthethird
study, total labor for producing the plants was estimated at year of the gradient experiment, 2012, was the driest on
9.03hperthousandplants,including2.55hforpreparingsoil record,althoughannualprecipitationtotalswereonlyslightly
andconesforplanting,5.46hforplantingseeds,and1.02h belownormalduetoalargerainfallevent(150mm)inearly
Wetlands
Table 1 Precipitation (mm) at the Madison, SD weather stations, ap- plants expanded vegetatively by rhizomes into unoccupied
proximately25kmfromtheresearchsite(NOAA2013)
plots.
Year Annual Apr-Sept June-Sept
2008 615 395 276 VigorComponentsAlongGradient
2009 604 416 305
2010 912 801 692 Ingeneral,plant vigor atlowelevationswas similarin2011
2011 607 501 313 and 2012, but was reduced in 2013 (Fig. 3). At high eleva-
2012 634 490 164b tions, plant vigor was greatest in 2011. Peak vigor values
2013 a 376 200 occurred at lower elevations in 2012 and 2013 than 2011
30-yearmean 655 495 343 (Fig.4).Differencesbetweendrilledpopulationsweregreatest
in2012,whenPrairieFarmvigorwasgreaterthanRedRiver.
aNotavailableatthetimeofwriting
Plant height was correlated with all measured variables, in-
bLowestsincerecordsbeganin1981 cludingbiomass(ρ=0.47;p<0.01).Inflorescencedensityvar-
ied much more than plant height or maximum inflorescence
height (Table S1). All three measurements were affected by
May.Thedryautumnof2012coupledwithaverageprecipi-
elevationxyearinteractions(TablesS2andS3).Plantheight
tationinspring2013resultedina verybriefperiodofinun-
was also affected by a planting x year interaction and a
dationbyshallowwaterrestrictedtothecenterofthegradient
populationxyearinteraction.Maximuminflorescenceheight
experiment wetland. The wetlands of the transplant density
alsodifferedbypopulation.Inflorescencedensitywasaffected
experimentdidnothavestandingwaterin2013.
byapopulationxyearinteraction.
DensityofPrairieFarminflorescenceswasgreatestin2012
EstablishmentAlongGradient andlowestin2013atthelowestelevations(<0.44m),butat
0.45 to 0.74 m was greatest in 2011 (Table 3; Fig. S1). In
ForthePrairieFarmpopulation,plantingtechniqueinteracted drilled treatments, the number of Red River inflorescences
with relative elevation to influence establishment success. declined every year, whereas Prairie Farm did not change
Transplanting plugs was more successful than drilling seed from2011to2012beforedecliningsharplyin2013(Table4).
regardlessoftheelevation;however,thisdifferencewasgreat- Inflorescence density of Red River was greater than Prairie
er near the wetland bottom than on the slopes (Table 2). Farmin2011butPrairieFarmwasgreaterthanRedRiverin
Success on the wetland bottom was less than on the slopes 2012(Table4).
regardlessofplantingmethod.LikePrairieFarm,drilledRed Mean maximum inflorescence height was greater for
River was more successful on higher slopes than on the drilledPrairieFarmthanRedRiver(2.0vs.1.5m;Table4).
wetland bottom. Success of both populations and planting There was also an interaction effect of year x position, with
techniquesincreasedfrom2011to2012,becauseestablished height at the lowest position greater in 2012 and 2013 than
Fig.2 Thirty-year(1981to
2010)meanmonthlyprecipitation
(horizontallines)andmonthly
precipitation(verticalbars)from
January2010toSeptember
2013atMadison,SD(NOAA
2013)
Wetlands
Table2 Percentagesuccessof
twodifferentplantingtechniques Population Plantingtechnique Relativeelevation Year
fortwopopulationsofprairie
cordgrass,asaffectedbyrelative 2011 2012 2013
elevation.Successwasdefinedas
atleastonetillerbeingpresent PrairieFarm Plug 0to0.1m 65 94 100
withinthesamplingquadrat. PrairieFarm Drill 0 0 31
Plantingoccurredin2010
RedRiver Drill 10 11 15
PrairieFarm Plug >0.1m 86 96 90
PrairieFarm Drill 67 74 78
RedRiver Drill 57 75 66
2011,butheightathigherelevations(0.45to0.74m)greater the yearafter planting, but did not differ from2010to2013
in2011than2012(Table3). (Table6).Meanyieldfrom2010to2013was12.1Mgha−1,
PlantheightwasgreaterfordrilledPrairieFarmthanRed harvestedatgroundlevel.
Riverinallyears(Table4).Plantheightwasgreatestatmidto
upperelevationsin2011butshiftedtothelowestelevationsin EconomicAnalysis
2012and2013.
Cordgrass biomass yield was 8.3 Mg ha−1 harvested by
BiomassAlongGradient field-scale equipment to a 12-cm stubble height in the
eastern wetland (0.5-ha) at the experimental site in 2012
Biomassdidnotdifferbetweenpopulationsorplantingtech- (Zilverberg et al. 2014). The harvest occurred after cord-
niquesin2013.Biomasswasgreatestatthemiddleelevations grass had been combined for seed and some biomass
(0.16 to 0.40 m; Table 5). Within the same wetland, 16 consequently removed. Harvest with field-scale equip-
samples were harvested at ground level along the northern ment was 60 % of total above ground biomass
edgeofthewetlandin2011.Meanbiomassofthesesamples (Zilverberg et al. 2014). Using this harvest fraction with
was14.7Mgha−1,withastandarddeviationof5.5Mgha−1. measured annual biomass production (Table 6), estimated
Thesesampleswerenotincludedintheexperimentaldesign. hay production ranged from 5.4 Mg ha−1 in 2013 to
8.9 Mg ha−1 in 2011, with an average of 7.3 Mg ha−1
TransplantDensityExperiment from 2010 to 2013. Farm-gate prices received for grass
hay harvested at the Prairie Farm from 2010 to 2013
Plugsurvivalattheendofthefirstgrowingseasonwas91%. ranged from $55 Mg−1 in 2011 to $110 Mg−1 in 2012,
Biomassdifferedbetweenthetwoplantingdensitiesin2009, with an average of $81 Mg−1. Costs for establishing
Fig. 3 Vigor index of two populations of prairie cordgrass along an drilled.Sampleswithoutaplantwereremovedfromthedatasetbefore
elevation gradient, measured in 2011 (solid line with open circles), analysis. Lines were drawn using the second degree local polynomial
2012(dashedlinewithexes), and2013(solidlinewithfilledcircles). technique.Beforeplottingpoints,valueswereaveragedacrosstransects
ThePrairieFarmpopulationwastransplantedfromgreenhouseplugsor andelevationrangesof0.05mtoimproveclarityofgraphs
Wetlands
Fig. 4 Range of maximum vigor for each combination of population dashedline).Rangeofmaximumvigorwasdefinedastheupperquartile
(PF=PrairieFarm;RR=RedRiver)xplantingtechnique(DrillorPlug), ofvigorvalues,excludingoutliers.Outliersaregraphicallyindicatedby
measuredin2011(solidline),2012(shortdashedline),and2013(long filledcircles
cordgrass were estimated at $4,040 for the 0.9-m spacing, net incomewas -$134,$48,and $0ha−1 for a 20-year stand
$1,476 for the 1.5-m spacing, and $2,153 ha−1 for direct life with the 0.9 m, 1.5 m, and direct seeding, respectively.
seeding, excluding land rent. Establishmentcostswerenotrecoveredovera20yearperiod
Usingthe2010–2013averagehayyieldandprice,annual- for the 0.9-m spacing. The payback periods for the 1.5-m
ized net income was estimated at -$496,−$192, and spacinganddirectseedingwere17and20years,respectively.
−$273 ha−1 for a 10-year stand life with the 0.9-m spacing, Recovering the opportunity cost of cropland rent was not
1.5-m spacing, and direct seeding, respectively. Annualized achievedovera20yearperiodforanyestablishmentmethod.
Table3 Meanvaluesofmeasuredplantcharacteristics,asaffectedby lowercaseletterarenotdifferent(p>0.05).Withinarow,valuesfollowed
population,year,plantingtechnique,andrelativeelevationalongaprairie bythesameuppercaseletterarenotdifferent(p>0.05)
wetland-uplandgradient.Withacolumn,valuesfollowedbythesame
Dependentvariable Population Plantingtechnique Year Relativeelevation
<0.15m 0.15to0.44m 0.45to0.74m 0.75to1.38m
Plantheight Prairiefarm&Redriver Drilled 2011 1.0aZ 1.1aZY 1.1aY 1.1aY
2012 1.1aX 1.2bY 1.0bX 0.7bZ
2013 1.3bX 1.2bX 1.0bY 0.7bZ
Plantheight Prairiefarm Drilled&plugged 2011 1.1aY 1.3aZ 1.3aZ 1.2aZ
2012 1.4bX 1.4bX 1.1bY 0.8bZ
2013 1.3bX 1.3aX 1.1bY 0.8bZ
Maximuminflorescenceheight Prairiefarm&Redriver Drilled 2011 1.5aY 1.7aZ 2.0aZ 1.9a
2012 1.9bY 1.9aY 1.6bZ 1.2a
2013 2.0bY 1.8aZ 1.7abZ 1.8a
Inflorescencedensity Prairiefarm&Redriver Drilled 2011 8.0aY 10.2aY 10.3aY 4.0aZ
2012 8.5aY 10.8aY 3.3bZ 0.7bZ
2013 1.2bZ 1.2bZ 0.2bZ 0.0bZ
Inflorescencedensity Prairiefarm Drilled&plugged 2011 9.0aY 12.1aY 10.8aY 4.1aZ
2012 16.1bY 16.2bY 4.0bZ 1.0aZ
2013 1.0cZ 0.9cZ 0.2cZ 0.0bZ
aNotsubjectedtostatisticalanalysisduetothesmallnumberofobservations
Wetlands
Table4 Meanvaluesofmea-
suredplantcharacteristics,asaf- Dependentvariable Population Planting Year
fectedbypopulation,year,plant- technique
ingtechnique,andrelativeeleva- 2011 2012 2013
tionalongaprairiewetland-up-
landgradient.Withacolumn, Plantheight Prairie Drilled 1.2aZ 1.2aZ 1.1aZ
valuesfollowedbythesame farm Plugged 1.3aY 1.2aZ 1.1aZ
lowercaseletterarenotdifferent
Plantheight Prairie Drilled 1.2aZ 1.2aZ 1.1aZ
(p>0.05).Withinarow,values
farm
followedbythesameuppercase
Redriver 0.9bY 0.8bZ 0.9bY
letterarenotdifferent(p>0.05)
Inflorescencedensity Prairie Drilled 7.0aY 7.9aY 0.4aZ
farm
Redriver 9.9bX 3.7bY 0.9aZ
Population
PrairieFarm RedRiver
Maximuminflorescence Drilled 2.0Y 1.5Z
height
Discussion two populations (p=0.58). Mean yield was greatest
(6.0Mgha−1) from0.16to0.39mrelativeelevation,which
Gradientanalysisrevealed a zone ofmaximum prairie cord- corresponded to a maximum water depth of 0.11 to 0.34 m.
grassvigorthatshifteddownslopetothecenterofthewetland The most-suited areas for cordgrass production are likely
beginning in 2012, the driest summer on record (Fig. 4). In shallowtemporarywetlandsandseasonalwetlandswithshort
2012, the basin recharged with rainwater early in the spring hydroperiods.Byusingthisinformationtostrategicallyplace
(326mmprecipitationfromApril-May)butdriedoutbecause cordgrassinappropriatewetlandenvironmentswithinproduc-
little moisture was received from June to September tion agriculture fields, field-scale biodiversity, and perhaps
(164mm).Thus,plantswerefloodedforlesstimeinthedry biomassyield,couldbeincreased.
summerandprobablyextendedrootsdeepertoreachground- The two plantingtechniquesresultedinsimilar vigor and
water. This was most detrimental to plants in the upper por- biomassproductionexceptinthewetlandcenter,wheredril-
tions of the basin and the upland surrounding the wetland, lingwasineffectiveatestablishingplants.Withinthisregion
wherevigordecreasedmorerapidlywithincreasingelevation from 0 to 0.1 m elevation from the wetland bottom, the
thanin2011,whenthewetlandreceivednormalprecipitation equivalent of 0.4 to 0.5 m maximum water depth, standing
(Fig. 3).However, the shallow water in2012was beneficial waterinthecenterofthewetlandeitherpreventedgermination
for those plants in the basin center, which had presumably or killed small seedlings. In contrast, starting plants in the
beenstressedbyextendedinundationin2011.Effectsofthe greenhouse before transplanting to the field was effective
2012 drought extended into 2013, when the wetland held alongtheentireelevationalgradient.Thistechniqueusedless
much less water despite receiving average precipitation in seedthandrillingat7.5kgPLSha−1,butwasmorecostlyat
thespring(Fig.2). the0.9-mspacingbecauseitrequiredgreenhouseaccessand
Zones of maximum production for the two populations morelabor.However,forseedpricesgreaterthan$185kg−1,
overlapped. There was nodifference inbiomass yield ofthe transplantingatthe1.5-mspacingwaslesscostlythandirect
Table5 Biomassproduction (Mgha−1)bytwo populations ofprairie a row, values followed by the same lowercase letter are not different
cordgrassplantedusingtwotechniquesatdifferentelevationsabovethe (p>0.05).Valuesaremeansoffourblocksandtwoplantingtechniques
floorofawetlandbasinin2013.Sampleswerecutatgroundlevel.Within (firstrow)orfourblocksandtwopopulations(secondrow).N=84
Population Planting Relativeelevation
technique
< 0.08to 0.17to 0.23to 0.33to 0.41to 0.81to
0.08m 0.16m 0.22m 0.32m 0.40m 0.80m 1.13m
PrairieFarm Drill/Plug 1.50a 4.49b 6.13b 5.91b 6.39b 1.35a 0.18a
Prairiefarm/Red Drill 0.00a 3.06b 5.04c 5.89c 6.69c 1.56ab 0.04a
river
Wetlands
Table6 Biomass and/or N fertilization can partially offset yield declines after
(Mgha−1)ofwetlands Year Plantspacing,m
thesecondyear(unpublisheddata).
plantedtoprairiecord-
grassat0.9-or1.5-m 0.9 1.5 Theplantingdensityexperimentfoundthatbiomassdiffered
spacingin2008.Within betweenplantingdensitiesforonly1yearafterestablishment.
arow,treatmentsfollow- 2009 3.8a 2.0b At that point, stands were still immature and biomass yields
edbythesamelowercase 2010 10.7a 11.0a were probably too low to justify harvesting. Therefore, it is
letterwerenotdifferent
2011 16.0a 13.8a unlikelythattheadditionaltimeandmaterialsrequiredtoplant
(p>0.05).N=165
2012 14.2a 13.3a at0.9-mspacingratherthan1.5-mspacingwerejustified.
2013 9.9a 8.2a Cordgrassbiomassyielddataintheliteraturearescant,but
our yields at the highest elevations, upslope of a temporary
wetland, were similar to yields from another experiment on
gravellyuplandsoils(1.4Mgha−1;Boeetal.2009).Prelim-
seeding.Therefore,anoptimumestablishmentstrategywould inaryyielddatacollectedinthegradientexperimentin2011
be to transplant into the wetland bottom (maximum water (datanotshown)suggestedthatyieldsdeclinedfrom2011to
depth > 0.4 m) and drill the higher reaches if seed can be 2012, presumably due to the dry summer through winter in
obtainedforlessthan$185kg−1.Transplantingwouldbethe 2012. Within our zone of optimal production and after a
optimumestablishmentstrategyovertheentirewetlandareaat severe drought, yield in the gradient experiment was lower
higherseedcosts.InnortheasternKansas,overallsurvivalof thanotherexperimentsongoodsoils(6.4and11.7Mgha−1;
transplanted cordgrass plugs was 90 % after 3 years, but BoeandLee2007andBoeetal.2009)andinnaturalstands
decreased to 73 % for small plugs at low elevations (Fraser (9Mgha−1;AlbertsonandWeaver1944).Yieldsobtainedin
and Kindscher 2005). Our results after 1 year were similar. this experiment within the optimum production zone were
Fraser and Kindscher (2001) found that cordgrass plugs tri- similartoswitchgrassyieldsatothersitesontheexperimental
pledinareafrom0.51to1.57m2over3yearsandthatfastest farm, collected using similar techniques (unpublished data).
growth occurred at shallow maximum water depth (0.11 to Yield from the transplant density experiment peaked at
0.20m).BoeandLee(2007)notedthatplotswithaninter-row 14.9Mgha−1(in2011)andweresimilartoyieldstakenfrom
spacing of 90 cm and intra-row spacing of 35 cm formed thenorthernborderofthewetlandinthegradientexperiment
dense sods by the third production year. Although we did (14.7Mgha−1)in2011.Bothweresimilartotheplotyieldof
not measure basal area, our results indicated thatestablished 14.6Mgha−1reportedbyBoeetal.(2009).
plantsspreadintounoccupiedspace(Table2). Based on the economic value of the biomass, recovering
We observed the Red River population to have a more theopportunitycostofcroplandrentwasnotachievedovera
tussock-like growth form, compared to Prairie Farm, which 20 year period for any establishment method. However, this
spreadrapidlyandobscuredthelocationoftheoriginalrows wasonlandthatwouldbesubjecttofrequentcropfailuresdue
planted. Prairie Farm’s natural leaf height and inflorescence towet conditions, and thus may not be generating sufficient
heightwerebothgreaterthanRedRiver,butthepopulations revenue from conventional crops to cover cropland rent. In
didnotdifferinbiomass.Theheightdifferencemightimpact addition, our analysis included the use of a large amount of
benefitstowildlifebecauseifleftunharvestedoverwinter,the labortoremovehybridcattail—anexpensiveactivitythatwas
tallerPrairieFarmpopulationmightcontinuetoprovidewild- conductedontheexperimentalfarmbutwould probablynot
lifecoverafterRedRiverwasburiedbydeepsnow.Popula- beundertakeninatypicalproductionfield.Hadthiscostnot
tion interacted with year to impact inflorescence density but been incurred, establishment costs were estimated to be re-
had no effect on biomass; both biomass and inflorescence covered in 17, 7, and 9 years for the 0.9-m spacing, 1.5-m
densityweresensitivetotheeffectofelevation. spacing,anddirectseeding,respectively.Establishmentcosts
The decline in inflorescence density from 2012 to 2013 werehigherfordirectseedingthanfortransplantingatthe1.5-
could have been caused in part by drought. However, it has m spacing due tothe larger amountofseedusedwithdirect
alsobeenobservedthatcordgrassinflorescencedensitytypi- seedingandthehighcostofseed.
cally peaks in the second year (unpublished data) and seed Harvesting cordgrass seed offers a highly variable but
productiondeclinesdramaticallybythe5thyear,presumably potentially profitable supplement to biomass harvesting.
because stands become sodbound (Jensen 2013). For com- Acrossthe farm, seedyield was ~5to15kgPLSha−1 from
mercial seed production, plants are usually grown in wide 2010 to 2013. These yields were lower than the “average”
rows (2 to 5 m) and cultivated to promote seed production. range of 34 to 84 kg ha−1 reported by the NRCS (2012),
A challenge for commercial seed production is that insects presumably because the areas were not intensively managed
thatfeedintheseedheadsandonbelowgroundgrowingpoints forseedproduction.Thatistosay,theywereneverfertilized
destroy ovules and reduce seedhead density, especially in andonlyrarelyburned.Inaddition,manywerenarrowstrips
stands at least 3 years old (Boe et al. 2009, 2013). Burning that were difficult to harvest mechanically. However, in the