Plant Biomass and Productivity of Prairie, Savanna, Oakwood, and Maize... Central Minnesota

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 .
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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
<8
<1
<1
<1
2
6
13
858
4,558
0
2
6
8
771
2,983
0
1
5
6
832
3,582
6
6
782
5,913
5
392
3,656
4
9
549
4,162
16
1,067
4,972
2
6
16
763
2,748
6,695
6,725
4,049
4,113
4,711
5,208
6,039
6,697
3,511
4,471
5,416
6,329
3,754
4,120
4,414
4,605
Dead vegetation
Litter...................
2,871
2,044
2,453
3,047
2,687
2,374
3,023
3,805
Total weightofvegetation....
9,596
6,157
7,661
9,744
7,158
8,703
7,143
8,410
Olderstems...........
Total forshrublayer.*
Subterraneanstems ......
Roots...................
Roots and subterranean
stems................
Total forlivingvegetation.
TABLE III.
Ovendry weight of vegetation in the savanna type-expressed in kilograms per hectare
SAMPLING DATE
Vegetationsample
April 14
Living vegetation
August 11
September October November
12
3
14
564
1,188
1,916
0
30
30
3
325
341
28
24
27
25
50
35
76
7
28
68
4
29
56
4
25
34
4
28
33
0
0
0
(13,511)
(16,645)
(30,156)
1,061
12,010
0
76
20
(13,511)
(16,645)
(30,252)
915
12,048
15
1,570
139
(13,511)
(16,645)
(31,880)
1,083
11,785
21
1,277
135
(13,511)
(16,645)
(31,589)
1,563
10,335
1,090
1,480
263
(13,511)
(16,645)
(32,989)
1,807
6,317
0
1,469
241
13,511
16,645
31,866
1,023
13,878
0
86
250
(13,511)
(16,645)
(30,492)
1,004
7,807
0
88
312
(13,511)
(16,645)
(30,556)
1,627
10,049
13,071
(43,287)
12,963
(43,362)
12,868
(45,362)
11,898
(44,751)
8,124
(43,097)
14,901
48,397
8,811
(39,799)
11,676
(42,569)
(
4,024)
8,169
(12,193)
(
4,024)
6,884
(10,908)
(
4,024)
8,848
(12,872)
(
4,024)
10,280
(14,304)
4,024
10,767
14,791
(
4,024)
12,527
(16,551)
(
(55,555)
(56,270)
(57,623)
(57,401)
63,188
(56,350)
(59,062)
30
Stemsformedin 1959..
Older stems...........
Total forshrublayer
Tree layer
Flowersand fruit......
Leaves ...............
Branchesformedin 1959
Older branches*.......
Boles* ...............
Total fortreelayer....
Subterraneanstems.......
Roots..................
Roots and subterranean
stems................
Total forlivingvegetation.
0
0
Leaves...............
Dead vegetation
( 4,024)
Dead stemson trees*.
Litter.7........
..
7,060
Total fordead vegetation.. (11,084)
*
July9
120
Herb layer...............
Shrublayer
Flowersand fruit.
Total weightof vegetation....
June11
May 12
(54,371)
5
462
1,574
1
304
1
22
1
4
0
4,024)
12,469
(16,493)
arebasedonthesevaluesin theSept.14column.
3 whentreeswerefelled.Data in parentheses
SampledonlyAug.31-Sept.
RESULTS
relatThe resultsnot only provideinformation
and
ing to plant biomass, primaryproductivity,
of organicmatterbut also demthe decomposition
onstratethe broad differencesin plant biomass
betweenthe fourecosystemsand the changesoccurringin each ecosystemthroughoutthe year
It is important,however, to
(Tables II-V).
recognize the limitationsof the data. For example,the weightsof the threemain plant strata
are not givento the same degreeof accuracy; this
situationis inevitablewith such enormousdifferences in total weightsper unit area as exist betweenthe tree and herbaceouslayers of the oakto estimatethe
wood. It is notoriouslydifficult
weightof the root mass accurately,and the data
58
TABLE IV.
Ecology,Vol. 44, No. 1
AND OTHERS
J. D. OVINGTON
Ovendry weight of vegetation in the oakwood type-expressed in kilograms per hectare
SAMPLINGDATE
Vegetationsample
April 15
Living vegetation
Herb layer.25
Shrublayer
Flowersand fruit .
..............
Leaves .
June15
July10
37
91
81
159
207
66
41
67
67
52
1
218
l
184
140
33
57
244
311
368
520
371
589
407
613
458
638
464
555
490
547
0
853
53
( 49,019)
(111,888)
(161,813)
51
15,409
3
2,389
115
( 49,019)
(111,888)
(163,414)
48
19,249
7
2,626
172
( 49,019)
(111,888)
(163,712)
114
20,630
11
2,848
292
( 49,019)
(111,888)
(164,058)
126
13,517
20
3,543
483
49,019
111,888
164,953
122
15,738
0
975
220
( 49,019)
(111,888)
(163,297)
90
11,844
0
1,274
280
( 49,019)
(111,888)
(162,461)
192
9,889
15,460
(177,621)
19,297
(183,322)
20,744
(185,126)
13,643
(178,473)
15,860
181,658
11,934
(175,852)
10,081
(173,130)
(
2
in 1959..
Stemsformed
)
J
319
Older stems...........
321
Total forshrublayer. . .
Tree layer
0
Flowersand fruit......
0
....
Leaves ...
0
Branchesformedin 1959
( 49,019)
Older branches*.......
(111,888)
Boles* ...............
Total fortreelayer.... (160,907)
74
Subterraneanstems.......
12,881
Roots..................
Roots and subterranean
.
stems..........
12,955
Total forlivingvegetation. (174,208)
August 12
September October November
4
15
13
May 13
22
40
58
Dead vegetation
( 21,838)
Dead stemson trees*.
34,226
Litter...................
Total fordead vegetation.. ( 56,064)
(
21,838)
37,122
58,960)
( 21,838)
51,944
( 73,782)
( 21,838)
38,622
( 60,460)
( 21,838)
23,917
( 45,755)
21,838
31,511
53,349
( 21,838)
41,249
( 63,087)
( 21,838)
35,279
( 57,117)
Total weightof vegetation.... (230,272)
(236,581)
(257,104)
(245,586)
(224,228)
235,007
(238,939)
(230,247)
* Sampled
arebasedonthesevaluesin theSept.14column.
onlySept,23-24whentreeswerefelled.Data in parentheses
TABLE
V.
Ovendry weight of vegetation in the field of
maize 1-expressed in kilograms per hectare
DATE
SAMPLING
Vegetation
sample
June12
September October
10
15
July14
August20
1,881
1,848
1,740
4,719
1,689
5,537
1, i44
2,275
628
2,029
589
1,567
472
2,873
6,491
9,026
8,720
302
1,019
1,011
889
309
611
155
1,174
83
1,094
108
997
3 3,394 7 7,665
10,120
9,717
Maize
Fruit(including
grain,cob,and
husk)..
Leaves.18
Stem (includingI
maleinflorescence)........
Roots.8
Total .26
Weeds
Shoots.4
Roots and sub-
terranean
stemrs. 2
Total.6
Totalweight
of
32
vegetation.
J
902
1 Fieldploughed
weight,
May15andplantedMay19with8 kg,ovendry
seed/
hectare.
tree trunksand main brancheswere not determined until near the end of the growingseason
and consequentlythe monthlychangesin the tree
layer weights reflectdifferencesonly in stems,
leaves, flowers,and fruitformedin the sample
year. Finally,no attemptwas made to assess the
amountof photosynthate
used in plant respiration
or the weightof living plant materialeaten by
animals.
Differencesof plant biomassamong
thefourecosystems
On all occasionswhenthe fourcommunity
systems were sampled,the amountsof the different
types of organic matterpresentdifferedgreatly
fromarea to area. For example, in September
the fieldof maize, the savanna, and the oakwood
had, respectively,112, 8, and 28 times as much
livingvegetationper hectareas the prairie. The
weightsof living vegetationin the savanna and
oakwood were much greater than those of the
prairieor maize fieldmainlybecause of the high
proportionof woody plants present,but the herbaceous layer of the savanna, even thoughpartly
shaded,was double the weightof thatof the prairie. The woodlandherbaceouslayerwas thepoorest developed. The distributionof living' plant
for these weightsare probablythe least accurate
of all the measurementsobtained. Errors result
fromfailureto cut the large tree roots with the
soil corerand the loss of finerootsin washingthe
in the
soil away. Unexpectedlylarge differences
total weightsof roots recordedfor the soil cores
fromeach plotoccurred,and in view of thisvaria1"Living"hererefersto wholeplantbodiesoftheliving
bilitymoresoil coresper plotwouldhave increased plants,exceptfor main roots and stumpsof the woody
the precisionof the estimate. The weightsof the plants,whichwere not sampled.
Winter 1963
BIOMASS
AND
PRODUCTIVITY
matter among the herbaceous, shrub, and tree
layersvaried,but theoverallaveragesfortheyear
expressedas percentagesoftheabovegroundliving
vegetationwere for the prairie98, 2, and 0; for
the savanna 2, 0.1, and 98; and for the oakwood
0.05, 0.4, and over 99; so thatin none of thethree
communitysystemsdid the shrublayer represent
a largeproportionof thetotallivingplantbiomass.
Althoughthe values given for the weightsof
roots and subterraneanstems are probably too
small, particularlyfor the roots of the wooded
part of the plant biomass was
area, a significant
below groundlevel. The averageweightsof roots
and subterraneanstems in the prairie, savanna,
oakwood, and field of maize are 4,824, 11,789,
14,977,and 650 kg/ha respectively(Table VI),
equal to 91%, 27%, 8%, and 1% of the living
OF
TABLE VII.
Ovendry weight of plant material in the
ground litter-expressed in kilograms per hectare (averages of all observations in sample period, April-November)
Vegetationsample
Litterfromtreesand shrubs
VI. Plant biomass,ovendryweight,in fourecoLeaves ..................
Acorns,twigsand bark. . .
systems-expressedin kilogramsper hectare (averages
Litterfromherbaceouslayer.
of all observations
in sampleperiod)
TABLE
ECOSYSTEMANDSAMPLEPERIOD
Vegetationsample
Herbaccouslayer............
Shrublayer.................
Tree layer..................
Roots and subterraneanstems.
Total livingvegetation.......
Litteron ground.............
Total dead plant material.....
Total plant material.........
Prairie
(Apr.Nov.)
Savanna
(Apr.Nov.)
Oakwood
(Apr.Nov.)
(June-Oct.)
449
10
0
4,824
5,283
2,788
2,788
8,071
770
47
31,223
11,789
43,829
9,625
13,650
57,479
88
512
163,076
14,997
1; 8,673
36,735
58,572
237,245
5,536
0
0
650
6,186
0
0
6,186
59
ECOSYSTEMS
it originatedfromthe plantsof the herbaceousor
woodylayers,but in theoakwoodtherewas a considerableaccumulationof blackamorphousorganic
matterover the mineralsoil, almostfourtimesthe
weight of relativelyfresh litter overlyingthe
highlydecomposedorganic matter (Table VII).
Virtuallyall of the plant materialpresenthad
been producedwithineach type plot. The most
notableexceptionwas the prairie into whichoak
Amorphousplant material. .
Total litter................
ECOSYSTEM
Prairie
13
0
2,775
0
2,788
Savanna Oakwood
1,337
1,447
6,841
0
9,625
3,550
3,873
97
29,215
36,735
Maize
plant biomass. The subterraneanstemscollected
in the soil cores were mainlyfromplants of the
herbaceous layer and when separated from the
roots gave average weights of 741, 1,208, and
fortheprairie,savanna,and
87 kg/harespectively
oakwood, i.e., 165%, 155%, and 101% of the
weightof the herbaceouslayerpresent.
Considerableamountsofdead plantmaterialhad
accumulated aboveground in the three natural
systems;thustheaverageweights
plantcommunity
of obviouslydead organicmatterper hectarefor
the prairie, savanna, and oakwood were 2,788,
13,650,and 58,572 kg, respectively. Such material as the heartwoodof the treeswas includedin
the living biomass althoughthe cells are mainly
dead. In the savanna and oakwood the dead organic matterwhichhad not fallento the ground
but remainedattachedto the trees and shrubsas
dead branchesamountedto about one-thirdof the
total dead plant matterin the savanna and just
undera half in the oakwood. In the prairieand
savanna virtuallyall of the dead organic matter
overlyingthe mineralsoil was undecomposedand
could be readily separatedaccordingto whether
leaves were blown fromthe surroundingsavanna
areas and held betweenprairie plants, but oak
leaves were nevermorethan2%oby weightof the
prairielitter.
Changesin thefourecosystems
throughout
theyear
The total dry weightsof all types of organic
matter recorded in the four ecosystemsvaried
considerablythroughout
the samplingseason from
32 to 10,120 kg/hain the fieldof maize,6,157 to
9,744 in the prairie, 54,371 to 63,188 in the
savanna,and 224,227 to 257,103 in the oakwood.
These differencespartly reflectinherentdifferences in the chosen samples,and partlychanges
in amountsof accumulatedphotosynthate.Except
forthe maize field,wheretherewas a progressive
increasein the totalweightof the vegetationfrom
April to Septemberand a decrease in October
and November,the totalweightof organicmatter
in the ecosystemsvaried irregularlythroughout
the year,partlya resultof the varietyof factors
influencing
the totalplantbiomassvalue estimates
of thenaturalcommunities.
Before the onset of spring growth,there was
little significantdifferencebetween the prairie,
savanna,and oakwood in the weightsof the living
herbaceouslayers. In all threeareas the weight
of the herbaceous layer increased from April
to August or September,and there was a rapid
fall in dry weight in October and November;
sincetheNovembervalues weregreaterthanthose
of April therewould possiblybe furtherdecrease
()()
J. D. OVINGTON
AN'D
OTHERS
i
y)1O04v, Vol. 44, No. 1
are only a small l)art of the total imiass. \Whentlhe
April samples were collected, the tree buds hiad
not opened. Growth of the iieNw slhoots was rapid
in the following months,and the maximumllweights
were reached in August or September, after which
the weight decreased rapidly to November Nhein
much of the fruit anid leaves had fallen. ILeaves
constituted the largest part of the shoot production, but in the savanna large amounts of acorns
were produced wlhiclhincreased rapidly in veiglht
inicrease in the savanna was 19 times and in the
and
of ANuglust
oakwood 4 timies,hut dur-iingmost of this period at the end of July and( beginnin'11g
of active growth, the field of maize was bare and were shed before the Septemiber samiplinig. rhe
tiii)rodtuctive. Although the production of or- samp)le year imay have beenI unusual in the large
was delayed in the planted crop, wlhen amount of acornis produced oii the trees of the
ganiicimiatter
the imiaizeaiid its associated weeds started growing, savainina,but the abundance of o0l( acorn cuptnles
inicrease wvascomiparativelyrapid, and oIn the grounid suggestedI that ligh acorni prodtlcthe wveiglht
fromiijune to July dry weiglht increased over a tioIn was a fairlyregular evenitin tlhesavanniiaarea,
so that the weight of living vegetation possiblv because virtually the wh-oleof each tree
hulnd(redfold
in the iaize fiel(d in July greatly exceeded the crowniwas in fulll lighlt.
Thle weights of otlher comiponeintsof the ecoweights of the herhaceous layers in the natural
systeimirecorded at each sampling period, namiely
ConilIUinlity systems, (lespite their earlier start.
of all the shrub layers increased roots, subterranean stems, and litter,did niotshoW
rhe w,veights
froImllow values in April, whein the buds of the marked progressive changes through the year. In
woodland shrubs had just begun to open, to maxi- the case of root systems this lack of change may be
iiitiiii values about August, after which leaf fall due to inadequacy of sampliing,but in the case ot
eighIts
steimis chainge in gro'1ss. Wn
occtirre(land(Iweicht (lecreased rapidly to Novem- subterranean
the year cotuldin fact Ic imir,aSince a-s
her. Thlie recorded weights of the older shrubl) tlhrouglhout
are exhausted niew rhizomlles may 1e
stemiisin the prairie and savanna were nIot greatly old rlhizonmes
nlot
(lifferelit at the beginining and einl of the growiing forme(d aIndI the total rhizolllmemIaSs w\-otuld
se.asonlo,i.e., in April anid Novemilber,but in the chanige greatly. Greater weights of litter .ccnlmed
monithswhleni leaf fall
oa),kwoodthere hadlbeen a large itncreasein weiglht to be present in the autumniiiii
as
of the older slhrul) stemiis. OIn the wlhole, the occurre(l, but inicreases wver-eniot ats imarl-ked
major clhanigesin the weiglhtsof the shrub layers mlight be expected. While bur oak leav-es fall
throughout the year can be attributed to the pro- promptly in October, many of the leaves are redutctioniof new shoots, the magnitude of change tainled oIn northerinpin, nortlhernred, anld wvhite
and the l)roportion of stemi, leaves, flower, and oaks througlhoutthe winiterand( they fall only a
before bud expansioin in sprinig. In1frtit v-aryingaccordiing to the species of shrub, week or tws-o
timie of year, and shrubl)size. \When the shrub creasing litter fall may hlave been compensate(l to
weights, the weight some extent by increasiig decomposition in the
layers attainiedtheir mlaximiiumii
of the new shloots formed a large proportion of warmil,wet autumin weatlher,and(Ieveen if, in the
thle g-ross weight, in the case of the prairie and oakwoo-o(l
of the
for inistaince,all the leav-esand(Ifi-ruit
savainia mior-etlhanithe wveightof the oldler stems. herbaceouts and shrul) and tree layers bad falleni
I eaves constittited the largest part of the new froimiAugust to Nov-emb)er,the av erage mionthly
shoot weight. After leaf fall in November the fall would have been only,about 1.000 kgy'/ha
onito
weight of the newvstems wvasotnlyabout 12%7cof a litter nmassweigg-hing
about 40,000 kg 'ha. The
that of the old stems so that if the weights of the increase in weight would be (liffictult
to demiionishrub layers are constant from year to year, this strate more intensive sampling.
12% increase in stem xveightmust be counterbalanicedby a correspondinigimortalityof either old or
Prodiction of organic msa-tter
new stems in the winter period. Lawrence, who
Aninual productiv,ityis Inot synonymous with
has visited these areas regularly for imany years,
believes that the shrub layer has gradually becomie plant biomass nor with gross changes in plant
cltieto receintlprotectionfrombtirn- biomass from year to year, for a plant com-iunity
more lutxtrianlt
may not is normally composed of many differentspecies and
ing so that stemiiproduction aindIimiortality
individuals of the same species which do not necesbe exactly equal.
The tree layers differfrom the shrub layers in sarily attain theirgreatest itndividualweights at the
that the new shoots formed in the sample year time of maximum community biomass. Further-
period. Over the whole
(luriingthe overwiniterinig
growing perio(1the greatest increase in dry weight
of the herbaceous layer occurred in the savanna
and the least in the oakwood. The herbaceous
layers of the inaturalcommunities had made about
onie-thirdof their total growth in early spring before the imaize wvasplanted. By June the herbaceous layer of the prairie had increased to about
20 times the April Neight while the corresponding
Winter1963
AND
BIOMASS
PRODUCTIVITY
OF ECOSYSTEMS
61
annualproductivity
was greaterin thecommunities
wheretheproportionof woodyplantswas greater.
The shrubs and trees ratherthan the forbsand
grasses became the most productivemembersof
the community,as the zone of photosynthetic
activitybecamemorecompleteand extendedhigher
above the earth'ssurface.
Despite its short growing season the field of
maize gave a high annual productionof organic
mattereven thoughit containedno woodyplants,
but in thiscase the soil had been greatlymodified
and the high level of organic matterproduction
was dependentuponheavyapplicationoffertilizers
to the soil. Bray,Lawrence,and Pearson (1959)
have shown the large differences
in productivity
betweenmaize grownwithand withoutfertilizers.
Provided soil conditionsare suitable,maize, althoughrelativelylate in startingactivegrowth,is
able to grow rapidlyand, by virtueof its height
and density,carries a large weightof photosyntheticorgans,muchgreaterthanthe prairievegetation. Most of the organic matteris produced
betweenmid-Mayand mid-September
over a periodof about 125 days,whichamountsto an average daily productionof about 85 kg/ha for both
ovendry maize and weed plantstogether.
Annualprimarynet productivity,
more some of the organicmatterproduced,e.g.,
flowers,bud scales,and lowerleaves,are shed before individual plants attain their maximum
complicatedwhen
weights.The situationis further
containsbiennialsand perentheplantcommunity
nials. Finally,samplingcan rarelybe so frequent
thatthereis no dangerofmissingthepeak weights
oftheplants.Odum (1960), workingwiththerelaof the early
tivelysimpleecosystemscharacteristic
successionalstages followingthe abandonmentof
assofields,has overcomesome of the difficulties
of organicproducciated with the determination
tionand turnoverby weighingtogetherat monthly
intervalsall plants of a given species, also litter
of thesespecies,separately. In the presentinvestigation the maize, the shrubs,and to a more
limitedextentthe trees,have been sampledseparatelyby species. The herbaceouslayer,consisting
mainlyof perennials,was so complexthat it was
consideredonly as a whole, and estimatesof its
annual productivityare thereforebased on the
betweenthe recordedmaximumweight
difference
and lowest overwinteringweight of the aboveestimates
groundparts. Consequentlyproductivity
(Table VIII) will tendto be low.
TABLE
VIII.
weight-expressedin kilogramsper hectare
DISCUSSION
ECOSYSTEM
Vegetation
samp)le
_._
Prairie Savanna
182
389
9,456'
412
0
2,833
4,046
0
0
5033
5,263
3,5753
1,886
Herbaceouslayer.920
.10
Shrublayer
Treelayer
Shootsofsampleyear...
older
Bolesandbranches
thancurrent
year
Total foraerial parts.
Rootsandsubterranean
stems.-
Oakwood
_
Maize
930
-
8,192
-
0
0
9,456
1,211
1 Peakbiomass
pluspeakofweedsin August.
ofmaizein September
2 Peakof1959stems,
ofwoodin older
in July;increment
leaves,and flowers
stemsconsidered
tobe zero(seeTableIII).
3 Thesevaluesmayseriously
sincetheyaremeanvaluesobtained
underestimate
theexisting
biomass
bytreeage.
bydividing
The amounts of organic matterproduced annually in the ecosystemsdiffergreatly (Table
Site factorssuch as soil conditionswere
VIII).
not exactly comparable, since the prairie and
savanna areas were on dune sand fromwhichthe
mineral colloids have been winnowedby wind,
whereas the oakwood was on glacial outwash,a
surfacewitha muchhigher
primaryphysiographic
colloidal content(Cooper 1935). In the case of
the three natural communitiesit seems unlikely
were sufficiently
great to
that the site differences
in annualproducaccountforthelarge differences
tivity. Differencesof formand structureof the
vegetationseem to be the more importantfactors
that
and it is significant
productivity,
influencing
All fourcommunitysystemswere very heterogeneous and the variabilitychangedconsiderably
throughtheyear (Tables II-V). The maize field
was the simplestand mostuniformecosystem,but
in July the 400 measuredcorn plants varied in
heightfrom73 to 153 cm, while in the,following
monththe heightrange was from128 to 276 cm.
In additionto thisspatialand timediversity,
each
plant communitywas composedof plants with a
wide rangeof forms,e.g. frommosses to treesin
the savanna and oakwood,and the plant material
exhibitedall stages of decomposition.With such
diverseorganic matterso irregularlydistributed,
multiplesamplingis necessaryto characterizeeach
ecosystemas a whole. Froma practicalviewpoint,
however,the intensityof samplingalso depends
upontheavailableman-hoursand theneedto avoid
samplingso intensivelythat the vegetationis seriouslymodifiedfor futurework. The sampling
techniquesrepresenta compromisebetweenthese
different
considerationsbut neverthelessserve to
demonstratebroad differencesin plant biomass
and some of the seasonal changesoccurringin the
fourecosystems.
Over the wintermonthsthe maize fieldis bare
of vegetationand the soil surfaceis exposedto the
weather. In contrast,the threenaturalcommunities alwayshave a plantcoverand withtheadvent
of springare able to initiategrowthquicklyand
62
J. D. OVINGTON
effectively.It is clear, however,that duringthe
periodwhen the maize plantsare well established
use is made
and cover the ground,very efficient
productiontemporarofthesiteso thatthemonthly
ily exceeds thatof the naturalcommunities.The
of the maize fieldat this stage
higherefficiency
comparedto the oakwood may be due to the high
levels of soil nutrientsavailable as a resultof the
fertilizerapplicationsand to the factthat a much
higherproportionof the livingcells are photosyntheticin themaize thanin the oakwoodplants.
under
The data have been analyzedstatistically
the guidanceof M. D. Mountford,and the main
describedamong the four ecosystems
differences
provedto be significant.To give some indication
of the samplingtechnique,data
of theeffectiveness
forthe herbaceouslayerand rootmass were summarizedin termsof the fourquartersof each type
plot (Table IX). Throughouttheyearthe smallest weightof the herbaceouslayer recordedfora
IX. Ovendry weights of the aerial herbaceous
layer and of the subterranean organs of the quarters of
the type plots-expressed in grams
TABLE
TYPE PLOT
Prairie
_
Month
_
Oakwood
Savanna
Ecology,Vol. 44, No. 1
AND OTHERS
primarilyto the presenceof woody perennialscapable of makingfulleruse of site conditions.
In contrast,the artificialcommunityof the
maize fielddoes not containwoodyperennials,but
the recordedannual productivity
is relativelyhigh
and appears to be about equal to thatof oakwood.
The recordedestimateof annual productivity
of
the oakwoodis certainlytoo low, however,forthe
annualproductionof treeboles and mainbranches
is an averageforthelifeof thetrees,duringwhich
growthhas increasedgreatly,and withinthe ecosystemas a whole some treesand possiblyshrubs
and herbaceousplants will have been suppressed,
killed, and decomposed. Consequentlyit seems
thatthe oakwood is the mostefficient
producerof
organic matter. Furthermore,the maize can be
sustainedon a long-term
basis onlybyconsiderable
human effortand the applicationof considerable
amountsof fertilizer. In contrast,the oakwood
has receivedno input of human energyand no
applicationof fertilizers.
The organicmattercollectedin thisinvestigation
has been analyzedforchlorophyll,
energy,and nutrientcontent,and later papers will considerthe
fourecosystemsfromtheseaspects.
SUMMARY
Sample plots were markedout in typicalareas
of prairie,savanna, and oakwood, and in a field
0.1
0.2
0.1
0.1
April.......
of maize, at Cedar Creek Natural HistoryArea,
0.1
0.3
0.3
0.2
May .......
Minnesota. Plant biomass determinationsfor
0.3
1.0
2.9
1.1
JUne.......
0.3
0.6
1.9
2.9
July.......
monthlyintervalsfromApril to Novembershow
0.6
0.9
4.4
1.5
August.......
the seasonal rhythms
of the different
characteristic
0.8
1.5
4.2
September... 2.8
0.4
0.3
1.7
October.... . 1.2
ecosystemsand the large differences
betweeneco0.1
0.3
0.9
November... 0.6
systemsin the amount of organic matterthey
Subterraneanorgars per ccre
contain.
While it is recognizedthatthereare great dif7.3
9.2
15.9 10.7
6.3
6.3
12.5
3.0
4.5
April.......
7.2
16.9 11.8
5.2
9.2
2.8
16.5
1.7
3.6
May.......
ferencesin the accuracyof the estimatedproduc9.2 19.5 14.8
9.0
3.1
5.6
13.9
4.7
June.......
1.9
tivityvalues,the maize estimatesbeingmostaccu6.4
10.1
8.9
19.9 15.8
7.9
3.1
4.1
3.8
July.......
rate and the woodlands the least, primarynet
11.7 10.4
5.4
8.5
4.4
4.8
2.8
2.7
1.6
August.......
14.4 10.6 10.6 13.7 12.1
3.5
6.0
3.9
September... 2.5
productivityprobably increases from prairie to
9.1
7.3
11.0
2.3
4.3
6.0
6.9
1.8
2.9
October.....
savanlnato oakwood. The annual productivity
of
11.4
5.7
7.6
7.7
2.1
2.7
4.0
9.0
3.9
November..
the naturalwoodlandis probablyhigherthanthat
.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
of theintensively
managedmaize field.
greaterthan
quarterin the savanna is consistently
It is suggestedthat in the upland communities
themaximumforany quarterof the oakwoodplot. of the Cedar Creek region,the presenceof woody
Similarly,for root mass, the smallestvalue for a perennialplants is associated with an increasein
greaterthan three of the dynamicprocesses in materialand
quarterin theoakwoodis consistently
the largestvalue forany quarterof the typeplot energy flow of ecosystems,i.e., the production,
in the prairie.
and decomposition
oforganicmatter.
accumulation,
The living plant biomass decreases fromoakwood to savanna to prairie,as do the amountof
ACKNOWLEDGMENTS
and ordead plant material,annual productivity,
This study owes much to a number of people who coganic matterturnover,if our assumptionis cor- operated in it, especially to Gerald Martin, Allan Bonde,
Philip Neumann, and Joyce Ovington who assisted with
rect that the weight of dead organic matteris the
collection and sorting of the plant material, and to
relativelyconstantfromyear to year. These dif- Elizabeth Lawrence who kindly checked the manuscript.
ferencesin ecosystemdynamicsseem to relate We are indebtedto Alvar Peterson who planted and culMin
Max
Avg
Min
Max
Avg
Min
Herbaceous layer per clip quadrat
0.1
0.1
0.1
0.2
0.1
0.1
0.4
0.2
0.5
0.5
0.1
1.8
2.6
2.0
2.3
0.2
5.5
4.8
2.6
3.9
0.3
14.4
7.7
3.8
3.8
0.4
3.2
6.3
8.9
3.6
0.1
1.4
2.7
1.0
1.9
0.1
1.2
0.7
0.5
1.9
Max
Avg
Winter 1963
SYMPATRIC
63
GASTROPODS
tivated the maize on his own farm and permittedsampling
beyond the stage at which he would have harvested it for
silage. Gratefulacknowledgmentis made to the Louis W.
and Maud Hill Family Foundation, the National Science
Foundation, and the Graduate School of the Universityof
Minnesota for financial assistance. Permission to sample
at the Cedar Creek Natural History Area was given by
the Universityof Minnesota and the Minnesota Academy
of Science.
Time. Univ. Minnesota Press, Minneapolis, Minn.
116 p.
Fernald, M. L. 1950. Gray's manual of botany. Amer.
Book Co., New York. 1632 p.
Lindeman, R. L. 1942. The trophic-dynamic aspect of
ecology. Ecology 23: 399-418.
Odum, E. P. 1960. Organic production and turnover in
old field succession. Ecology 41: 34-49.
Pierce, R. L. 1954. Vegetation cover types and land
use history of the Cedar Creek Natural History
CITED
LITERATURE
Reservation, Anoka and Isanti Counties, Minnesota.
M.Sc. Thesis, University of Minnesota, Minneapolis.
Bray, J. R. 1960. The chlorophyll content of some
137 p.
native and managed plant communities in central
Minnesota. Canadian J. Bot. 38: 313-333.
Weaver, J. E. 1958a. Summary and interpretation of
underground development in natural grassland comBray, J. R., D. B. Lawrence, and L. C. Pearson. 1959.
munities. Ecol. Monographs 28: 55-78.
Primary production in some Minnesota terrestrial
communities for 1957. Oikos 10: 38-49.
. 1958b. Classification of root systems of forbs
of grassland and a consideration of their significance.
Cooper, W. S. 1935. The history of the Upper MisEcology 39: 393-401.
sissippi River in Lake Wisconsin and Postglacial
TROPHIC
RELATIONSHIPS
OF 8 SYMPATRIC
PREDATORY
GASTROPODS
ROBERT T. PAINE
of Zoology, Universityof Washingtont,Scattic
Dcpartmnent
observerto concentratehis effortson a functional
INTRODUCTION
1lexusin whichthe speA commonapproachto ecologicalproblemsin- unitwithinthecommunity
is limited. Where theseunitsare
volves the descriptionof food habitsof singlespe- cies membership
in mind,offoodchains recognizabletheyshould serve as a naturalintercies or,withthecommunity
interactions
and webs and their energeticimplications. In mediarybetweensimplepredator-prey
recentyears food chains have receivedrelatively in whichsome of the basic biologyfor each comlittle quantitativeattention,except as an entity ponentis known,and analysesof wholecommuniexisting within and contributingto community ties whiclhtend to ignore specificdetails. The
organization. Elton (1927) describedone type presentanlalysishas been concernedwithdescribof food chain as originatingfromherbivoresof ing such a subdivisioninvolving8 large (shell
various sizes, radiatingout fromthese,and even- length5-35 cm) predatorygastropodsand their
in some ultimatepredatorwith- prey,and with examiningthe associationfor any
tuallyculminating
out consequentialpredators of its own. Food propertiescharacterizingthe functioningof the
chainstendto be shortbecauseofcontinuedenergy whole assemblage.
The authoris gratefulto Florida State Univerdegradation at each transfer,and Hutchinson
forpermissionto resideat the AlligatorHarsity
(1959) suggeststhata maximumof 5 linksexists.
Laboratory,FranklinCounty,Florida,
Food chains thus are concise units of community bor i\'Iarine
wherethe data were obtained,and to R. B. Root
structure.
However, the ideally realized food chain is an and C. E. King forcriticism.
abstractionsince it may be said thatall organismis
BIOTOPE AND BIOTA
eithereat or are eaten by more than one other
Shallow water marine habitats of western
species (Allee et al. 1949). It is thus probably
difficult
to describe a naturallyoccurringmulti- Florida provideexceptional,and perhaps unique,
to observepredatorygastropods.Not
linkedfood chain in whicheach successivepreda- opportunities
tor eats only a single prey species and when the only is the fauna diverse,but some of the gastrofood consumedat each trophiclevel is completely pods are amongthelargest,and hencemostreadily
known. It is possible, though,to describe the observable,in the world. Sandbars such as the
communityfood web and, because a numberof one to be describedare inhabitednormallyby 8
to sub- species attaininga length greater than 5.0 cm:
"top predators"exist in each community,
dividethefoodweb intomoreor less discreteunits PleuroplocagiganteaKiener,Fasciolaria tulipaL.,
in its own "top predator." Such F. hunteriaPerry, Busycon contrariumConrad,
each culminating
a divisionis oftendesirablebecause it permitsthe B. spiraturnLamarck,Murex floriferReeve, Poli-