Plant Biomass and Productivity of Prairie, Savanna, Oakwood, and Maize Field Ecosystems in Central Minnesota Author(s): J. D. Ovington, Dale Haitkamp, Donald B. Lawrence Reviewed work(s): Source: Ecology, Vol. 44, No. 1 (Jan., 1963), pp. 52-63 Published by: Ecological Society of America Stable URL: http://www.jstor.org/stable/1933180 . Accessed: 01/02/2012 13:44 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected].

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52

J. D. OVINGTON

AND OTHERS

Ecology,Vol. 44, No. 1

slowlythroughthemoreopen savanna woodlands. Botting,G. 1956. "Black Sunday" and its effectson The dense exotic scrub communities,however, Adelaide Hills orchards. J. Agric. South Australia 57: 256-61. constitutethe greatestfirehazard. Cochrane,G. Ross, S. M. Burnard,and J. M. Philpott. diagramsshow the general Cover stratification 1962. Land use and forest-fires in the Mount Lofty lack of a dense, completeground cover of low Ranges, South Australia. AustralianGeographer8: 143-160. vegetationunder savanna woodlandsand also indicate the much densertree canopyand well de- Glaessner,M. F., and L. W. Parkin (eds.). 1958. The geologyof South Australia. MelbourneUniv. Press, finedshrubunderstoryof sclerophyllforests. Melbourne,Australia. 163 p. The "stringybark"tree stratumof sclerophyll Marshall,Ann. 1958. Climate,p. 76-83. In R. J. Best forestsis defoliatedbut not greatlyaffectedby (ed.), IntroducingSouth Australia. MelbourneUniv. fireand recoversrapidlyby growthfromadventi- Press, Melbourne,Australia. the in- Prescott,J. A., and J. A. Thomas. 1948-49. The length tious lateral shoots. In contradistinction, of the growingseason in Australia as determinedby digenous shrub stratumof these forestsis deof the rainfall. Proc. Roy. Geogr. the effectiveness though Soc. Australasia (South Australia) 50: 42-46. stroyedbyfireand undergoesa well-defined rapid seral developmentfromfire-razedcondition Specht,R. L., and R. A. Perry. 1948. Plant ecologyof to climax vegetationin 7-10 years. Five definite the Mount Lofty Ranges. Trans. Roy. Soc. South stages can be recognizedin the sclerophyllforest Australia 73: 91-132. R. C. 1942. The geologyof the Eden-Moana pyric sere, limited,however,to the understory Sprigg, Fault Block. Trans. Roy. Soc. South Australia. 66: only. Exotic vegetationis generallykilled by 185-214. bushfires,but exotic scrub regrowth,particularly . 1946. Reconnaissancegeologicalsurveyof portion of the westernescarpmentof the Mount Lofty of broomand gorse, is vigorous,dense, and very Ranges. Trans. Roy. Soc. South Australia.70: 313rapid. are notchangedbyfire, 47. The climaxcommunities Trumble,H. C. 1939. Climatic factorsin relationto successionbeinga rapidprocess. However,if the the agriculturalregionsof South Australia. Trans. indigenousvegetationis disturbedby cultivation, Roy. Soc. SouthAustralia.63: 36-43. vigorous, exotic, scrub growth can replace the Wood, J. G. 1937. Vegetation of South Australia. Government Printer,Adelaide, S.A. 164 p. slower growing, less dense, indigenous scrub . 1958. The vegetationof SouthAustralia,p. 84forms.

95. In R. J. Best (ed.), IntroducingSouth Australia. MelbourneUniv. Press, Melbourne,Australia. LITERATURE CITED Wood, J. G., and R. J. Williams. 1960. Vegetationof Black, J. M. 1943-57. Flora of South Australia. 4 Australia,p. 67-84. In C.S.I.R.O., The Australianenparts. 2nd edition. GovernmentPrinter,Adelaide, vironment,3rd ed., Melbourne Univ. Press, MelS.A. 1008%. bourne,Australia.

PLANT

AND PRODUCTIVITY BIOMASS OF PRAIRIE, AND MAIZE FIELD OAKWOOD, ECOSYSTEMS IN CENTRAL MINNESOTA

J.D.

SAVANNA,

OVINGTON

The Nature Conservancy, London,England DALE HEITKAMP

AND DONALD

B.

LAWRENCE

Department of Botany,University of Minnesota,Minneapolis,Minnesota INTRODUCTION

Cedar Creek Natural HistoryArea is situated 50 km (30 mi) northof Minneapolisand St. Paul, Minnesota, and is about 1,620 hectares (4,000 acres) in area. In view of its nearnessto these urban centers,the influenceof the early settlers and theirsuccessorshas been surprisinglysmall. The firstwhitesettlersarrivedin 1856 and found in part the efa patchworkvegetationreflecting fectsof burningby Indians (Pierce 1954). Settlementby theEuropeanpioneerswas neververyinof the tensive,probablybecause of the infertility

sand and peat soils, so thatmanyfieldsstakedout by theearlysettlerswere soon abandoned,in some cases afteronly one crop had been planted and failed. The wooded areas were selectivelylogged, particularlyforwhitepine,Pinus strobus,and no doubt burningand forestdestructionfrequently followedloggingbut usually natural regeneration restoredsome form of tree cover. Eventually, large blocks of land were purchased by private landownerswho,because theyappreciatedthe solitude and wildernessvalues of the area, protected it fromfurtherdevelopmentand terminatedvir-

Winter 1963

BIOMASS

AND

PRODUCTIVITY

tuallyall agriculturaland forestryoperationsso that the general landscape has probablyaltered littleand the regionretainsits wildernesscharacteristics. Throughthe generosityof a numberof people the area is now undertheguardfarsighted ianship of the Universityof Minnesota and the MinnesotaAcademyof Science,who are continuing the past policyof preservingits naturalstatus whilstencouragingsuitablebiologicalresearch. Since the land surfaceis gentlyundulatingand the plantcover varies locallydependingupon differencesof soil, climate,and past land use, the Cedar Creek Natural History Area provides a types to compareverydifferent uniqueopportunity ecosystemswithina fairly of relativelyundisturbed compactarea, and thesecan be contrastedwiththe highlyartificialcommunitieson adjacent agriculturalland. Some of the pioneerwork on the dynamics of naturalecosystemswas done at Cedar Creek,notablyby Lindeman (1942). The presentaccountis concernedwithcomparisonsof areas of prairie,savanna,and oakwood,and a neighboring fieldof maize, all of whichare on an upland, sandysoil type,and in close proximity.

OF

ECOSYSTEMS

53

Oil whlether it was green or nlot) and non-living plant material. From the same 20 quadrats all the abovegroundplant litter was removed and separated into amorphousmatterand relatively undecomposedplant material,which was further sortedaccordingto whetherit originatedfromthe herbaceousor woodyplantlayers. Samplingof the shrubswas not done by quadrat clippingbut was based on aerial stemlengths. In the winterof 1958-59,priorto the main sampling season of 1959, the heightsof all shrubs in the type plot were measured. Subsequently,at each samplingperiodseveralaerial stemsof each shrub species were collected,theirheights(exclusive of new stem produced in the sample year) being within10 cm of the average heightmeasurement recordedforthe speciesthe previouswinter. The numberof shrubstemstaken varied accordingto the abundance of the species but was normally about ten foreach species at each samplingoccasion. These stems were collectedfromthe type examplebutoutsideofthetypeplot,sincerepeated samplingsof shrubsin the type plot would have seriouslymodifiedthe vegetation. The collected shrubstemswere dividedinto theirvarious comMETHODS ponentsas given-in the tables and the weightsof A general surveyof the Cedar Creek Natural the parts per uniitlengthof old stemwere calcuHistoryArea was made in autumn1958 in order lated. Asstumingthat the weights of the comsystemsand ponentsper tinitlengthof old stemwere the same the main plantcommunity to identify to select single examples of typical prairie, sa- forthe collectedshrubsand forthosemeasuredin vanna, and oakwood for detailed study in 1959. the plot the previouswinter,the shrubweightfor None of the selectedexamplesshowedevidenceof the plot could be determinedon an area basis by theaveragemeasuredweightsper unit burning,or grazingby multiplying recenthumaninterference, domesticanimals. Toward thecenterof each type lengthof old stemby the total lengthof old stem a plot 30 by 30 m square was pegged out for de- in theplot. Tree samplingwas more difficult than that of tailed monthlysampling,hereafterdesignatedas the typeplot. The same samplingmethodswere the herbs or shrubsand throughoutmost of the tech- observation period monthlysampling was reused in all threetypeexamples,but different niqueshad to be adoptedto sampletheherb,shrub, strictedto the new shoots. Living brancheswere and treelayers. For comparisonwiththe natural cut fromthe generaltree canopy of the type exareas, a field of maize on land adjacent to the amplesoutsideof thetypeplotsusingan extension NaturalHistoryArea was sampledusingdifferent prunier. The average weightsof leaf, fruit,and methods,and we are gratefulto the owner,Alvar new stemfora large numberof shootsformedin the samplingyear were determined. In August Peterson,forpermissionto samplehis crop. To sample the herb layer (here all non-woody and Septemberof 1959 some treeswere felledjust plants) each plot was subdividedinto quarters, outsidethe sampleplots; size rangeapproximated across each of which a 15- by 15-m grid was thatof the treesin theplots. Three trees (northmarked out to give 225 squares, each a square ern red oak) were harvestedin the oak woodland meter. At each samplingdate,fivemetersquares and six in the savanna (three northernpin and were selectedrandomlyin each quarter. Within three bur oak). The numbersof currentyear each meter square, the abovegroundvegetation stems per felledtree were countedso as to give froma centralsquare quadratof 20 by 20 cm was an estimateof thenumbersof new stemsproduced the numberof new clipped. No quadrat was sampledtwice and this in the plots. By multiplying permittedaccess and samplingwith- shoots by the average shoot weight the total arrangement out risk of serious tramplingof futuresample weightof the shootsformedin 1959 could be estiquadrats. Later, the clippedvegetationwas sepa- matedon an area basis. The felledtreeswere also rated in the laboratoryinto living (mainly based separated into bole, living branches older than

54

J. D. OVINGTON

AND OTHERS

Ecology,Vol. 44, No. 1

those of the sample year, dead branches,stems beginningin the second week of each monthand produced in the currentyear, and leaves. The being completedwithin the following2 weeks. various tree parts were weighed and the results The sampleswere usuallytaken in sequence,viz. herbaceouslayer and litter,shrubs,trees,and ficonvertedto an area basis forthe sampleplots. To obtain informationon the subterranean nallyroots. Each plantlayerwas sampledforall plantparts,in each typeplot cylindricalsoil cores communitiesbeforestartingon the next layer to approximately77.7 sq cm in cross section and make comparisons between communitiesmore 50 cm deep were extractedmonthlyfromten of meaningful. Detailed recordsand statisticalanalyseswill be the quadratsfromwhichthe herbaceouslayerhad been removed. The soil so collectedwas washed providedon requestto the Departmentof Botany, with a jet of water througha finemesh sieve on Universityof Minnesota,or to the Nature Conwhichrootsand subterraneanstemswere retained servancy,London, England. forlatersortingby hand. Weaver (1959a, b) has DESCRIPTION OF SAMPLE PLOTS describedin detail the developmentof the underPlant species seen in the sampleplots and their groundpartsoftypicalprairieplants,and although many roots and subterraneanstems go deeper immediatevicinityare listed in Table I; nomenthan 50 cm theytend to be concentratedin this clatureis thatof Fernald (1950) and the identificationswerecheckedby Dr. J. W. Moore to whom upperzone. The maize was sampled as follows. Towards we are most grateful. Herbariumspecimensare the centerof the fielda plot was markedout 40 filedat the Cedar Creek field laboratoryand at rows. the Herbarium of the Universityof Minnesota. rows wide and 60 m along the north-south At each monthlysampling20 maize plants were The prairie and oakwood vegetationswere quite taken, one fromevery alternaterow, the plants distinct,havingonly two species in common; the beingselectedin therowsby randomnumbers.At savanna floracontaineda numberof speciespresthe same time the heightsof 400 maize plants in ent in the othertwo areas and can be regardedas in character,althoughthe threeplots theplot were measured. To determinethe weight intermediate of maize plantsper unit area, the average weight do not representa successional sequence from per unitlengthof the 20 sampleplantswas multi- prairieto forest. The prairietypeplot (Fig. 1, upper) was in the plied by the total lengthof maize plants per hectare,based on a figurederivedfromthe measure- same generalarea as stand3 of Bray (1960) who mentof the 400 plantsand countsof the number reportedan old residentas saying that the area of maize plants in the plot. Each sample maize was never completelyploughed or grubbed,the plantwas dividedintostem,leaves,and ear (grain, crop being planted in single furrows. Soil procob, and husk) which were weighed separately. filesover the area showed no evidenceof earlier The weeds were collectedby takinga distanceof ploughingand since the yield would have been ifmade, 1 m along the row of maize northof each of the poor any desultoryattemptsat cultivation, 20 sample maize plants and collectingall weeds were probablysoon abandoned. The vegetation betweenthe sample row and the next row to the was tall-grassprairieand themostcommonplants east overthemeterlength. The rootsof themaize were the threegrasses Stipa spartea,Poa pratenplants and the weeds were removedas carefully sis, and Andropogongerardi,which occurredin as possibleby looseningand diggingthe soil to a patches. Althoughthetwo shrubsRosa arkansana depth of about 50 cm and attemptingto remove var. suffultaand sand cherryPrunus pumilawere abundant (101 stems of rose and 115 of sand completeroot systems. Samplingwas always done whenthe vegetation cherryin theplot of 900 sq m), theydid not form was dry (free of dew and rain), and smallersam- a dominantfeatureof the vegetationsince they ples such as the herbaceouslayer and soil cores were not bushy and their average heightswere wereplacedin plasticbags to avoid excessivewater only 18 and 36 cm, respectively.The vegetation loss and fortransportto the laboratory. Usually was fairlyopen and burrowingrodentsand low samples were taken to the laboratorywithinan contentof soil colloids probablypreventedthe of a close cover. Deer were seen in the hour of collectionwhere theywere quicklysepa- formation ratedout forweighingfresh. All or a large por- area but no deer-browsedor -grazed plants were tion of each typeof freshplantmaterialwas then observed. Tree seedlingswere completelyabsent cut up and thoroughlymixed, and three sub- even thoughthe prairie area was surroundedby samples of each were dried at 80?C to determine savannahavinga fairdensityof seed-bearingoaks. The savanna type plot (Fig. 1, middle) contheovendryweight. From April to November1959, a completese- tained 17 treesand 8 shrubbyclumps (average of ries of sampleswas taken everymonth,sampling 10 stemsper clump) of bur oak, Quercus macro-

Winter 1963

BIOMASS

AND

PRODUCTIVITY

Species

__

Typeof plant Prairie Savanna Oakwood oy ____ __ bodyl

~~ ~ ~ ~ ~ ~ ____

BromuskalmiiGray................ BoueelouahirsutaLag............... Panicum capillareL............,. CyperusfiliculmisVahl............. L ................ Mollugoverticillata Anemonepatens var. cvolfgangiana Bess. Nutt........... Delphiniumvirescens Helianthuslaetifiorus var. rigiduts Cass. Achillealanulosa Nutt.............. Senecio plattensisNutt.............. Equisetumhyemalevar.affine Engelm.. Poa pratensisL .................... Stipe sparteaTrin.................. Panicum virgatum L ................ Andropogon gerardiVitman......... Carex muhlenbergii Schkuhr......... TradescantiaoccidentalisBritt........ Bickn........ Sisyrinchiumcampestre Nutt...... Chenopodium leptophyllum Mirabilis hirsutaPursh............. Ranunculusrhomboideus Goldie...... PotentillaargutaPursh............. Rosa arkansanavar. suffultaGreene.. PrunuspumilaL ................... Lathyrusvenosusvar. intonsusButt.. . EuphorbiageyeriEngelm............ G. Don............. Viola pedatifidao Nutt......... Oenothera rhombipetala Asclepias tuberosaL ................ Asclepias ovalifolia Dene............ canescensMichx....... Lithospermum Scutellariaparvulavar. leonardiEpling MonardafistulosaL ................. Physalis virginianaMill............. Nutt......... Penstemongrandifiorus L ........... Campanula rotundifolia Liatris aspera Michx................ Solidago nemoralisvar. decemfiora

H H H H H H H H H H H H H H H H H H H H H H S S H H H H H H H H H H H H H

P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P

P P P P P P P P P P P P P P P P P P P P P P P P P P P

H

P

H

P

P

CoreopsispalmataNutt............. Artemisialudovicianavar. gnaphalodes

H

P

Smilacina stellataL ................. AmorphacanescensPursh ........... ElymuscanadensisL ................ QuercusmacrocarpaMichx...... QuercusellipsoidalisE. J. Hill....... Petalostemum purpureumVent....... Rhus glabraL...................... Rhus radicansL.................... CorylusamericanaWalt............. Prunus virginianaL ................ PteridiumaquilinumL .............. Carex pensylvanicaLam............. AlliumstellatumFraser............. Maianthemumcanadensevar. interius

H H2 H T T H S

(DC.) Fern .....................

Nutt..........................

Fern ..........................

S3

S S H H H

H

P P

Table I (continued) Species

Typeof plant Prairie Savanna Oakwood body'

Quercusrubravar. borealisMichx..... Arenarialateriflora L............... Anemonequinquefoliavar. interior

T H

AquilegiacanadensisL .............. Fragaria virginianaDuchesne....... Rubus idaeus var. strigosusMichx .. Rosa blanda Ait.................... AmiphicarpabracteataL ............. AcernegundoL .................... Parthenocissus insertaL ............. Vitis riparia Michx................. Vacciniumangustifolium Ait......... GaliumborealeL ................... AsterazureusLindl ................. Astersagittifolius Wedemeyer ........ Taraxacumofficinale Weber......... Agropyron repensL.4............... Zea maysL.4 ...................... Setaria glauca L.4..................

H H S S H T S L S H

P P P P P P P P P P

H H

P P

Fern .........................

H

H H H H

P P

P

P P

1 H=herb;S=shrub;L=liana; T=tree. Has someaerialwoodystems. Considered an herbin thepresent study;onlyaboutsixshootswerepresent. Present in themaizefield.

2 3 4

P

P

P P P P P P P P P P

55

OF ECOSYSTEMS

I. Plant speciespresent(P) in prairie,savanna, in centralMinnesota and oakwoodecosystems

TABLE

P P

P P P P P

P

carpa,and 3 treesand 6 shrubbyclumps (average of 6 stemsper clump) of northernpin oak, Quercus ellipsoidalis. The largerbur oaks in the plot were about 90 years old and 10 m high,whilethe largerpin oaks were about 17 years old and 9 m high. The average diameterover bark at breast heightof the bur oak trees was 22 cm and of the pin oak 6 cm. When the trees were in full leaf, thetreecrownsappearedto coverjust overa quar-

ter of the plot. FourteenQuercus seedlingswere present,and the wide rangeof ages of the treesin the area indicatedno rapid ecologicalchange and no heavy burningfor some time. The frequency and scattereddistribution of old treessuggeststhat the area had not been cultivated;almostcertainly it was grazed,thoughprobablynotheavily.Shrubs were a muchmore significant featureof the vegetationin the savanna than in the prairie,locally dominatingthe herbaceouslayer. Withinthe plot therewere 132 stemsof hazel, Corylusamericana, withan averageheightof 72 cm, 365 stemsof the same species of rose as in the prairie with an average heightof 32 cm, and 52 stems of choke cherry,Prunus virginiana,withan average height of 57 cm. The grasses formedthe dominantfeature of the herbaceous layer which was much denser and more continuousthan in the prairie. Ants were very abundantin the savanna, many more being presentthan in any otherarea investigated. The oakwood type plot (Fig. 1, lower), containing72 trees of Quercus borealis,was part of a ratheruniformstand withina mixed coniferangiospermforestcomplex which also included Pinus banksiana,P. strobus,Quercus ellipsoidalis, and Q. mtcrocarpa. The foresthad been heavily logged over, or burned,or both,about 60 years previously. The treesdid notvarygreatlyin age; ringcountsof the threefelledtreeswhichcovered the size rangein the plot,gave ages of 45, 56, and 58 years. The treesaveraged20 cm dbh and had a maximumheightof just over 17 m, theircrowns forminga dense and continuouscanopy. The

56

J. D. OVINGTON

JEI' .4. .1

FIG.~~~~Prir

e

upe) *

svna(ide,

.,

an

oak

wroodlanid (lower) typeplots. Views northward.Camera is 5 m southof southedgeofplot. The twoverticalscales 10 fttall are placed10 m and 20 m northof camera. The more distantscale is at centerof plot which is 30 m square. Lawrencephotos: prairieand savanna,Aug. 7, 1962; oak woodland,Sept.20, 1962.

AND OTHERS

Ecology,Vol. 44, No. 1

stems Acer negundo,average height95 cm. In was additionblueberry,Vacciniurm angustifolium, fairlyabundanit,being recordedin about 70% of the quadrats. Compared with the prairie and savanna plots, the herbaceous layer was poorly developedand was absentfromabout a quarterof the 20- by 20-cm quadrats, leaving exposed the surfaceorganic layers which completelycovered the sandymineralsoil. The fieldofmaize was plantedon May 19, 1959, using Kings Crost Hybrid K-5-3 seed planted singly at a spacing of approximately20 cm in north-south rows about 0.9 m apart. In laboratorytests2%s of the seed failedto germinatebut, accordingto fieldcounts of the plants 1 montlh afterplantinig, 32% of the seed failedto produce plants. The increased mortalityis tentatively attributedto birds, insects,and mammalseating seed and youngseedlings. Afterthe firstmonth, mortalitywas negligibleand counts in the type gave about 31,220 plantsper hecplot consistenitly low tare. The soil althoughsandyand inherenitly in nutrients, exceptpotassium,has been reasonably well managed with annual additionsof cow manure. The land was also well fertilizedwithammoniumiinitrate containinig33%s nitrate broadcast

at a rate of 200 lb/acre on May 15 when the area was plouglhed. At the time of planting on May 19 fertilizercontaininignitrogeni,phosphorus, and poin the proportion 4:12:36 was applied at tassitumii 190 lb/acre and on June 3 a further 167 lb/acre of 33% nitrate fertilizerwas added as a side dressing. Weed growth, includinigAgropyron repens andl Setar-ia glauca, although fairly luxuriant, was not regarded as excessive by the farmers of the district. The greatest average height of maize was recorded in August wheni the average from soil level to the top of the tassel (male inflorescence') wvas208 cim. The maize crop was harvested for silage on September 10, but the type plot with a surrounidinigprotective strip of three to four rows was left to permit a final sampling in October. The moisture contents of the top 10 cm of mineral soil in the differentareas were determined as percentages of the ovendry weight, and the trend was for higlhermoisture contenit (max 41% ) in spring, a consistently low moisture contenit (mim 3% ) fromiiJune to September, and increasing moisture content in October. In general, the soil of the oakwood was wettest and the soils of the prairie and maize field were driest. These differences became less marked during the summer so that by midsummer there were no significant differencesbetweenithe four areas in soil moisture

shrub layer was remarkably well developed, the type plot conitaining1,344 stems of Corylus arnericana, average height 87 cm; 23 1 stems Prtmnus v'irginiana,average height 119 cm; 86 stems Rubus idaeiis, var. strigosus, average height 53 cm; 21 stems Rosa blanda.,average hei.ght90 cm; 17 seedlings Pinus strobus, average height 47 cm; and 7 content.

Winter 1963 TABLE II.

AND

BIOMASS

57

OF ECOSYSTEMS

PRODUCTIVITY

Ovendry weight of vegetation in the prairie type-expressed in kilograms per hectare SAMPLINGDATE

Vegetationsample

April 13

Living vegetation

May 12

24

Herb layer............... Shrublayer

Flowersandfruit.. . . 9. in 1959 Stemsformed

July10

1 4

1985

August 10

642

488

59

0

Leaves.........

June10

J7

J

September October November 9 12 2

944

900

358

178