O sis,
5:
91
-111
(1990)
Qua e na y palaeoecology and ecological heo y
Valen í
Rull
IVIC. Cen o de Ecologia.
Ap. 21827. Ca acas 1020-A. Venezuela
Key wo ds:
climax, ecosys em e olu ion, models, palaeoecological heo y, p edic abili y, Qua-
e na y, s abili y, succession.
Abs ac .
A
e iew showing he po en ial con ibu ion o Qua e na y palaeoecology o he ecolo-
gical heo y, ocused on he ecosys em e olu iona y p ocesses, is p esen ed. By analyzing oceanic
and con inen al Pleis ocene and Holocene eco ds, some e lec ions abou ecological succession,
di e si y, hy hms, p edic abili y, s abili y, and modelling a e made, and compa ed wi h heo e i-
cal s a emen s de i ed om neoecology.
As a gene al conclusion, he necessi y o conside ing palaeoecological indings in ecological
heo y is emphasized. In addi ion, i seems essen ial o place palaeoecology in a mo e ecologi-
cal amewo k.
Resum.
Paleoecologia del qua e na i
i
eo ia ecologica.
Aques a icle e isa la possible con ibu-
ció que la paleoecologia del qua e na i po eni , en e s la eo ia ecolbgica, especialmen en els
p ocessos que es an elaciona s amb I'e ol~lució dels ecosis emes. L'anBlisi
de
seqüencies pleis o-
cenes i holocenes, an con inen als com oceAniques, pe me en e una sk ie de e lexions sob e
concep es com: successió ecolbgica, di e si a , es abili a , i mes, p edic ibili a i modela ge, o
con as an -les amb aquelles so gides de l'es udi neoecolbgic.
S'a iba a la conclusió gene al que els esul a s paleoecolbgics són necessa is en Teo ia Ecolo-
gica. També es p oposa la necessi a de si ua la Paleoecologia en un ma c més ecologic.
In oduc ion
The e ymological de ini ion o palaeoecology is he sho es one
-ccpalaeoecology is he ecology o he pas >>- (Bi ks
&
Bi ks
1980).
I is, howe-
e , su icien since i con ains he essen ial concep s in ol ed: ecology and
ime. The empo al s udy o ecosys ems needs pas e idences o s ic ness,
becoming specula i e when p edic i e models a e pu sued. In he middle lies
he s udy
o
he p esen li ing communi ies (neoecology), whose empo al do-
main is sca cely ep esen a i e o he ecosys em e olu ion. Ideally, ecology
should be conce ned wi h all hese iews: pas , p esen , and u u e.
The sea ch o egula i ies in he ecosys ems, which allow de i a e explana-
o y and p edic i e models, ha is, he heo iza ion o ecology (Ma gale
1977),
a ises gene ally om neoecologial s udies. Thus, models in which ime
is an essen ial componen a e de i ed om sho pe iods o obse a ion. The
92
V.
RULL
e idence is insu icien , and analogies wi h mo e de e minis ic sciences, like
ma hema ics o physical he modynamics, become necessa y. This is a easo-
nable p ocedu e, because li ing sys ems and beings a e no less han complex
physico-chemical en i ies, bu , undoub ely, he possibili y o ob aining a mo e
ex ended ime-dep h is be e han ex apola ion. The e o e, he in e ac ion
be ween'palaeoecology and neoecology is a mo e app opia e app oach o a
empo al unde s anding o ecosys ems.
Up o e y ecen ly, palaeoecology was no capable o p o iding much sui-
able da a o gene aliza ion and modelling pu poses (Valen ine 1972). The e-
o e, heo e ical ecology g ew, o a g ea ex en , on he basis o neoecology.
A p esen , al hough gene aliza ion o palaeoecological esul s, wi h ends
owa d he de elopmen o heo e ical bases a e inc easing, mos s udies
depend upon da a de i ed om neoecology wi h he esul an limi a ions in
he independence and uniqueness o in e p e a ions (Olson 1985). The book
(<Models in Paleobiologyn (Schop 1972) is a good example o his app oach.
Fu he mo e, some w i e s do no ag ee wi h he possibili y o heo iza ion in
palaeoecological (Ho man 1979, Olson 1985). Thei opinion is la gely sup-
po ed by he use o he so-called cccommuni y econs uc ion app oach,,,
which is, acco ding o hese wo ke s, he only alid way o s udy communi y
e olu ion and, he e o e, o make gene aliza ions in ime. Since good e-
cons uc ions o pas ecosys ems a e di icul and sca ce, due o inhe en p o-
blems o he ossil eco d, de ailed knowledge a he in a-communi y le el
seems no gua an eed by palaeoecology.
The p esen wo k is an a emp o analyze he con ibu ion o palaeoeco-
logy o ecological heo y, based on e y di e en p emises. Fi s , de ailed
knowledge o a communi y is no he only way o unde s and i s e olu ion.
The e a e indica o pa ame e s which a e associa ed o he ends in a ia ion
and endences o he ecosys em (Pielou 1974). Second, he palaeoecological
s udy is conce ned wi h ex a-ecosys em a ia ions, ac ing as impo an
o cing mechanisms, whose s udy con ibu es o elucida e causal ela ionships
o he obse ed phenomena. Concep s such as succession, s abili y, climax
hy mici y, p edic abili y, and modelling in ime will be he main objec o he
p esen e iew.
In his a icle, e olu iona y p ocesses a e no conside ed. Undoub ely, e o-
lu ion occu ed in he Qua e na y, jus like in o me imes, in e mingled wi h
ecological succession. Howe e , only such p ocesses ope a ing and de elo-
ping on unchanged species will be conside ed. The ela ions be ween succes-
sion and e olu ion a e o g ea ecological signi icance (Ma gale 1986), and
need special ea men .
~ime scales: he Qua e na y
The ecological phenomena eco ded a e a unc ion o he ime in e al consi-
de ed. Se e al classi ica ions o ime scales a e a ailable, bu since coinciden-
QUATERNARY PALAEOECOLOGY
93
ces a e clea , ha o Delcou e al. (1983) may be used as example. Acco ding
o hese wo ke s, h ee empo al domains can be dis inguished in he 's udy o
ege a ional dynamics:
1.
Mic oscale: cha ac e is ic phenomena a his le el a e physiological
e en s (0-10 yea s), coloniza ion, mo ali y, and g ow h a es (10-100 yea s),
in e especi ic ela ionships (50-500 yea s), such as compe ence, p eda ion,
and o he s a ec ing he ecological succession.
2.
Mac osale: he mos impo an phenomena a e clima ic changes, mig a-
ion, ex inc ion, and specia ion p ocesses, a ec ing he ecosys em e olu ion.
3.
Megascale, e en s which lie in his ca ego y p oduce biological e olu-
ions exceeding he ecosys em ame. Examples a e pla e ec onics and biolo-
gical e olu ion.
Neoecological s udies p oduce mic oscale da a, wi h he longe p ocesses
being e ec i ely obse ed o no mo e han decades o , a mos , a ew cen u-
ies. Fu he mo e, a ela i ely comple e unde s anding o he p esen biosp-
he e may be conside ed as a c oss sec ion o a complex o ecosys ems in di e-
en e olu iona y s ages. This ins an aneous pic u e may be compa ed o a
de i a e, a he ime ,, o a hypo he ical unc ion F( ), desc ibing he his o y
o he ecosys ems. Fo a eal unde s anding o he biosphe e, as was ecogni-
zed long ime ago by Donnan (1936), he in eg a ion o F( ) be ween o and ,
is he mos sui able p ocedu e. Howe e , whe e does one loca e poin o?
Since we a e in e es ed in he p esen li ing communi ies, he poin o ep e-
sen s he <<momen >> in which he o igina ed and, he e o e, i is a ma hema i-
cal a i ac . Bu a easonable, al hough no conc e e, depa u e poin is possi-
ble. The ossil eco d shows ha p esen li ing species a e gene ally no olde
han he Qua e na y o La e Te ia y, whe eas o me o ganisms haye beco-
me ex inc . As a consequence, he Qua e na y pe iod and, he e oie, he ma-
c oscale le el, will be he ime ame o he p esen issue.
Qua e na y e olu iona y a es ha e been low, and ex inc ion, as well as
some deg ee o€ specia ion we e he mos signi ican p ocesses. Mig a ion, dis-
placemen , mixing, isola ion, and o he spa ial eo ganiza ions, co ela ed
wi h clima ic a ia ions, a e cha ac e is ic o his pe iod (Dunba 1952, Flin
1971, Bowen 1978). As a consequence, in e -and in a- ecosys em in e play
has been in ense, p oducing complex e olu iona y p ocesses as he commu-
ni y le el, and esul ing in he p esen , s ill dynamic, si ua ion. The u u e is
no less ha he con inua ion o F( ), so any p edic ion mus be based on i .
Succession and subs i u ion
The classical concep o ecological succession e e s o a communi y de elop-
men p ocess which is cha ac e ized by s uc u al and unc ional, ime-
o de ed, changes (Odum 1971). This p ocess esul s om he modi ica ion o
he physical en i onmen by he communi y, which is he con olling agen ,
while ime and speed o change a e de e mined by he en i onmen . The
94
V.
RULL
hypo he ical culmina ion o succession is a s abilized and equilib a ed ecosys-
em, called climax. Some gene al c i e ia ha e been p oposed o ecognize di -
e en successional s ages. Among hem, he endence o a biomass, comple-
xi y, and di e si y inc ease in ime dese e men ion (Ma gale 1977). I has
also been s a ed ha s abili y and independence om ex e na1 condi ion aug-
men wi h succession (Ma gale 1968). These p inciples a e de i ed om
neoecological s udies, mainly om expe imen al, cyclic ( equenly annual),
and seconda y successions. Hypo he ical econs uc ions, based on he simul-
aneous obse a ion o se e a1 communi ies, which a e in e p e ed as di e-
en successional s ages o he same p ocess, a e also used. As a consequence,
hese eco ds a e ime-limi ed, and he long- he m in luence o en i onmen al
changes is implici ly ejec ed. Be ween he longe p ima y successions eco -
ded, hose de eloped on ecen ly deglacia ed a eas a e especially in e es ing.
Fo ins ance, Reine s
e
al. (1971) s udied he coloniza ion o Glac e Bay
(Alaska) by he ege a ion, du ing he las 250 yea s. A e deglacia ion,
abou 100 km o ba e soil we e apidly exposed, and some he baceous com-
muni ies we e he pionee s. The ollowing s ages we e cha ac e ized by Picea,
and la e by Tsuga, o es s. The inal communi y is he baceous again. Rela i-
ely s able en i onmen al condi ions p e ailed du ing his succession. Di e -
si y showed a apid ini ial inc ease, ollowed by a p og essi e a enua ion, and
a la e asymp o ic s abiliza ion, which is main ained a p esen . The a e o in-
c ease o di e si y was con olled by he addi ion o new species in he ea lie
s ages, and he equi abili y o hei abundances, nea he s abiliza ion. The as-
sumed clima ic communi y showed maximum di e si y, associa ed wi h a
complex mic ohabi a pa e n, suppo ing he iew ha s abili y a ou s di-
e si ica ion by p og essi e niche-subdi ision (Ma gale 1963, Connell
&
O ias 1964, Sande s 1968): Simila coinciden di e si y ends ha e been
ound in o he s udies (Bi ks 1980).
A
longe successional eco d, co e ing
he en i e Holocene ( he las 10 000 yea s), and de eloped in a s able en i on-
men , was ound in he Galapagos islands (Colin aux
&
Scho ield 1976 a and
b). The ansi ion om he las glacial pe iod o he Holocene was cha ac e i-
zed by inc ease in humidi y, and he es ablishmen o opical ain o es s. The
ecoloniza ion p ocess abou 1000 yea s. F om abou 9000 yea s be o e p e-
sen (BP), bo h clima e and ege a ion emained unchanged, un i1 oday. This
su p isingly long pe iod o s abili y seems o be an excep ion among palaeoe-
cological eco ds; ecen indings e eal empo al changes in he communi y
composi ion. Du ing he Holocene, clima ic luc ua ion ha e been eco ded,
including mean empe a u e cha ges o abou 3°C (Den on
&
Ka lén 1973).
The li ing communi ies we e undoub ely a ec ed by hese a ia ions, as
shown, o example, by dia om communi ies o some Finish lakes (Koi o
1970). The pos glacial coloniza ion, as well as di e si y ends o hese Holo-
cene communi ies, a e e y illus a i e conce ning his poin . The gene al ule
o a apid, ichness-dependen , ini ial di e si y inc ease was also eco ded
he e. Asymp o ic s abiliza ion, howe e , was no eached. On he con a y,
I
QUATERNARY PALAEOECOLOGY
95
di e si y a ia ions, co ela ed wi h clima e and ophic s a us we e obse ed.
The maximum di e si y coincided wi h phases o oligo ophy and highe em-
pe a u e, whe eas dis ophy and empe a u e dec eases we e associa ed wi h
low di e si y alues. Thus, no only he in e na1 communi y 'o ganiza ion, bu
also ex e na1 o cing ac o s a ec he successional p ocess.
In he o me examples, i was assumed ha di e si y measu es, in some
way, he complexi y and o ganiza ion o he ecosys em. Howe e , hese
poin -di e si y alues may be biased by sampling limi a ions. In palaeoeco-
logy, addi ional sou ces o e o mus be conside ed, mainly hose de i ed
om di e en ial sedimen a ion (Smol 1981), and p ese a ion o ossils (Las-
ke 1976). Ma gale (1968) p oposed a spec al app oach, which conside s he
cumula i e di e si y om a sequen ial sampling o an ecosys em, wi h p o-
g essi ely lange sample size. These di e si y spec a, like o he measu es o
he pa e n-di e si y (Pielou 1966), a e be e measu es o he s uc u al ea-
u es o he ecosys em, pe mi ing a mo e clea ela ion be ween di e si y and
p ope ies such as o ganiza ion, ene gy luxes, ma u i y, and o he s. A simple
communi y, ha is, one ha has ew, homogeneously dis ibu ed compo-
nen s, some o hem dominan , has a di e si y spec um wi h an ea ly sa u a-
ion poin . On he con a y, an ecosys em composed by many species, none
dominan , and wi h complex spa ial pa e ns (like mos opical o es ), p o i-
des di e si y spec a di icul o sa u a e. I he spa ial dimension is subs i u ed
by a empo al one, he spec um may be used o s udy s uc u al a ia ions in a
successional p ocess.
To es his me hod, a pollen eco d om he opical Venezuelan Andes is
used. Glacie s e ea ed om
3
000 o 4 700 m al i ude, be ween he las gla-
cial maximum (p obably 18 000 yea s BP; Schube 1974,1984) and he p e-
sen . In a locali y si ua ed a abou 4 000 m, he coloniza ion by ege a ion
s a ed a ound
12
000 BP (Rull 1985).
The pollen di e si y spec um (whose alues did no coincide wi h hose o
ege a ion ep esen ed, bu hei ends a e necessa ily co ela ed) shows ha
di e en pollen ypes a i ed by wa es (Fig.
1).
To a g ea ex en , equi abili y
de e mines he di e si y endences. This implies ha addi ion o disappea an-
ce o ypes a e no esponsible o he composi ional changes. The eo ganiza-
ion o ela i e equencies is he de e mining ac o . Independen e idence,
such as ee line posi ion, indica o axa, and o he s, we e he basis o he cli-
ma ic his o y o he si e, showing ha abou 9 000 yea s BP he glacie was lo-
ca ed nea he bo ing si e locali y, and no mo e han sca e ed he baceous
s ands li ed he e. Poo and luc uac ing communi ies a e sugges ed by he
spec um, o his phase.
A
ypical succesional end, wi h a sa u a ion poin ,
can be obse ed la e ; howe e , a u he inc ease, coinciding wi h a mean
empe a u e ise o abou
1.2"
C,
occu ed, a ound
2
500 BP. Since all he
ypes we e al eady p esen , equi abili y was he esponsible o he composi-
ional cha ge. Al hough cha ges in pollen abundances as a consequence o a-
ia ions in pollen p oduc i i y o he species in ol ed canno be disca ded, he

96
V.
RULL
10.000
YEARS B.P.
o
PRESENT
Figu e
1.
Va ia ions o he Shannon-Wea e index o di e si y (Pielou 1966), equi a-
bili y (E=H/Hmax), and ype ichness (R), om pollen assemblages ound in he s a-
ig aphical analysis o a pos glacial pea bog, om he Venezuelan Andes. Da a in
Rull (1985).
succession was modi ied, bu main ained. The e m ccmodula ed succession))
seems app opia e o his si ua ion.
En i onmen al a ia ions may in e up he successional p ocess, i some
h eshold is su passed. As is well known, sea le el changes occu ed-du ing he
La e Glacial-Holocene ansi ion (Flin 1971, Kidson 1982). As a consequen-
ce, many empe a e coas al lakes expe ienced successi e connec ions.and iso-
la ions om he sea. In No way, mos o hem we e saline 10,000 yea s ago,
when seale el was abou 40 m abou he p esen (Mange ud e al. 1974). A
his ime, dia om communi ies we e domina ed by polihalobious species (S a-
bell 1985). A subsequen seale el d op p oduced he isola ion and, he e o e,
desaliniza ion o lakes which became eshwa e bodies. As a consequence,
he o me li ing communi ies we e eplaced by o he s consis ing o halopho-
bus and indi e en species (S abell1985). This ep esen s a signi ican ecolo-
gical change, simila o he eplacemen o o es communi ies by open sa an-
nas, eco ded in A ica (Bonne ille 1980), and o he opical places, du ing
he las glacial epoch. The e m (( o ced subs i u ionn is mo e sui able o des-
c ibe his phenomenon because, no only eo ganiza ion, bu subs i u ion o a
communi y by ano he accu ed. In his case, a di e si y spec um looks like
ha esul ing om a spa ial ansec , c ossing an eco one, an,d go in o ano he
con iguous ecosys em. Fig.
2
shows he h ee main si ua ions discussed, which
a e cha ac e ized by he magni ude o en i onmen al a ia ion, as well as
QUATERNARY PALAEOECOLOGY
97
communi y ole ance. The clima ologic e minology may p o ide some use ul
e ms. Majo a ia ions, such as glacia ions, a e called changes. whe eas luc-
ua ion means mino oscilla ions (G i i hs
1976).
Thus, we can ela e change
wi h subs i u ion, luc ua ion wi h modula ion, and he di e si y spec a a e
use ul ools o disc imina e be ween hem, and also om non-dis u bed suc-
cessional p ocesses.
S abili y and he concep o climax
I is a widesp ead opinion ha he mo e complex ecosys ems, al hough well
adap ed o he p edic able en i onmen in which he e ol ed (May
1975),
a e
T
IME
-
Figu e
2.
Hypo he ical examples o h ee possible successional si ua ions:
A)
Nondis u bed succession.
B)
Modula ed succession.
C)
Induced
subs i u ion.
98
V.
RULL
no able o esis ex e na1 dis u bances. The opical o es is equen ly ci ed
as an example o bo h bio ic and en i onmen al cons ancy (Fische 1961, Fe-
do o 1966, Schawabe 1968). Howe e , ecen indings showed ha clima ic
changes also occu ed in low la i udes. E idences a e ound e e ywhe e (Wal-
ke
&
Chen 1987), and a e o e y di e en na u e, including: pollen analysis,
high-moun ain mo aines, allu ial e aces, o me lake basins, dia oms and
au ogenic mine als in lake sedimen s, s abilized dunes, and o he s (Li ings o-
ne 1980). The glacial pe iods o empe a e zones coincided wi h opical a i-
di y, and o es s we e eplaced by open ege a ion and dese s. Thus, he gla-
cial-in e glacial al e na ion was cha ac e ized in he opics, by he al e na ion
o sa anna (o dese ) and o es (Ga ne 1975).
A
e uge hypo hesis was p o-
posed o explain he pe sis ence o opical ain o es , in spi e o en i onmen-
al changes occu ed; o es e uge a eas a e assumed o be locali ies ha we e
no a ec ed by he a ia ions, owing o local condi ions, and in which he o-
pical o es p obably su i ed (Ha e 1982). The successi e con ac ions (gla-
cial) and expansions (in e glacial) o he o es con ibu ed o gene a e mo e
bio ic di e si y he e, as a esul o al e na i e mixing and isola ion (P ance
1982). Howe e , he lack o di ec e idence o he e uges (B adbu y e al.
1981, Salgado-Labou iau 1980, Schube
&
F i z 1985, Schube 1988) inci ed
o he al e na i e explana ions o he di e si y o he opical ain o es . The
mos popula a e: 1) The occu ence o ex ensi e Holocene e osiona1 and de-
posi ional e en s, due o mino clima ic luc ua ions (Campbell
&
F ailey
1984); 2) Fo es egene a ion by la e al mig a ion o i e s and i e meande s
(Salo e al. 1986);
3)
Fluc ua ions in he in ensi y and du a ion o d y seasons
(Absy 1986); and 4) Occu ence o na u al i es du ing he las 6 000 yea s
(Sand o d e al. 1985, Salda iaga
&
Wes 1986). In sho , luc ua ions we e
conside ed mo e impo an han changes, in de e mining he o es composi-
ion. O he w i e s conside ha no sub an ial changes in he ex ension, bu in
he composi ion o o es occu ed, as a consequence o glacia ion (Conno
1986).
Summa izing he p eceding in o ma ion, he his o y o opical lowlands is
cha ac e ized by bo h subs i u ions and modula ed successions (see also Flen-
ley 1979, Colin aux 1987). The o me ly p esen ed case o he Galapagos Is-
lands is an excep ion and, as such, i me i s u he conside a ion.
The classic"a1 concep o s abili y conside s en i onmen al dynamism o
some deg ee. Ecological s abili y e e s o he endency o an ecosys em o e-
main close o some equilib ium poin , o o e u n o i a e a dis u bance
(Odum 1971, Ma gale 1977), as a consequence o i s in e na1 p ocesses. Se e-
al p ope ies, such as cons ancy, ine ia, elas ici y, ampli ude, and o he s,
may be use ul o desc ibe ecosys em beha iou . Fo example, a high ine ia
(capaci y o assimila e ex e na1 dis u bances) bu low elas ici y and ampli ude
(capaci y o e u n, a e a modi ying dis u bance) a e assumed o opical o-
es s, while he con a y would be he ule o empe a e o es s (O ians 1975).
The concep s o esilience and a ac ion domain we e in oduced by Holling
QUATERNARY PALAEOECOLOGY
99
(1973). Acco ding o him, mo e han one po en ial equilib ium poin (al -
hough no anyone) would be possible o a gi en communi y, he sum o hem
o ming hei a ac ion domain. Thus, an ecosys em is mo e o less edien ,
depending on i s abili y o e u n o he domain. Al hough mo e han wel e
meanings o s abili y exis (Wi ake 1975), esilience is a sa is ac o y concep
in palaeoecology (Delcou e al. 1983). The Qua e na y p o ides good exam-
ples o dis u bed ecosys ems, and hei esponses. As shown, plan communi-
ies ecolonized he new open spaces c ea ed by glacie e ea , in a successio-
nal way. I is in e es ing o s udy he composi ion o hese la e communi ies,
and compa e hem wi h hose o me ly inhabi ing he a ea, ha is, be o e
he glacial dis u bance.
A
ecu en cycle in o es ege a ion was eco de o he
h ee las in e glacials in G ea B i ain (Godwin 1975, 1977).
All
o hem a e
cha ac e ized by common ends in p o oc a ic (Be ula, Pinus), mesoc a ic
(Que cus, Tilia, Ulmus, Alnus), and eloc a ic (Abies, Picea, Fagus), o es
ees. Thus, a s anda d in e glacial may be di ided in ou subs ages: 1) p e-
empe a e, domina ed by p o oc a ic ees;
2)
ea ly- empe a e, wi h mesoc a-
ic ees; 3) la e- empe a e, wi h eloc a ic ees; and 4) pos - empe a e, wi h
p o oc a ic ees again (Tu ne
&
Wes 1968). The mos in e es ing ea u e in
ou con ex , is he ac ha ela i e abundances o hese axa we e di e en du-
ing he h ee in e glacials. The same ege a ional ypes, bu wi h di e en
composi ions, de eloped a e each glacial pe iod. In o he wo ds, hese
ecosys ems adop ed h ee o hei po encial composi ional sa es, as exp ession
o hei esilience.
Phenomena o his na u e in ol e di e en bio ic esponses o he same
o cing in luence. The communi y esponse is a esul o he indi idual speci ic
beha iou o i s componen s. Da is (1969, 1976, 1981) showed he g ea
in luence o di e en ial mig a ion a es (a he species le el) on he ege a io-
nal composi ion o No h Ame ican ecosys ems, du ing he Holocene ecolo-
niza ion. La e , di e ences in esponse ime ( ime lag) we e added as a signi i-
can ac o (Da is 1984). The ime lags a e ela i ely sho o some
componen s (insec s, bi ds), bu can las a cen u y o mo e in plan s. These
di e ences depends on li e his o ies, gene a ion imes, beha iou , means o
dispe sal, compe i i e abili y, and o he s, and a e decisi e o de e mine he
communi y composi ion a a gi en si e, a a gi en ime (Da is 1984, W igh
1984).
In he ligh o his e idence, he en i onen al a ia ions, and he speci ic
di e ences in esponse, Da is (1984) p oposed ha ecosys ems ne e a ain
an equilib ium, being in cons an adjus emen o he ex e na1 changing condi-
ions. This con inuous disequilib ium hypo hesis is some imes c i icized, on
he basis o indings ha indica e long pe iodes o en i onmen al and ecologi-
cal s abili y (Wa s 1970, 1979). The al e na ion o s able and uns able phases
is also p oposed; bu s abili y canno mean cons ancy, because luc uac ions
a e always p esen . Mo consis en wi h palaeoecological e idence is he idea
o dynamic equilib ium (Delcou
&
Delcou 1983), acco ding o which
V.
RULL
pa e ns. The model also explained some o he e ec s o changing i e e-
quency, sugges ing mechanisms by which i e, compe i ion, and clima e, com-
bine o p oduce long- e m composi ional changes.
Final
commen s
Ecology is no an en i onmen al science, because i is conce ned wi h he
whole biosphe e, a he communi y o ganiza ion le el. Biosphe e is a mix u e
o spa ial g adien s, and empo al ends. The hough on which ecology is
based is ha nei he ends no g adien s a e a andom, ha ing egula i ies,
and o ganiza ion le els. Ecological heo y is he a m by which ecology a -
emp s o ind gene al ules.
Palaeoecology is no en i onmen al econs uc ions. I is a pa o ecologi-
cal s udy, which possesses a undamen al alue o ecological heo y, becuse i
p o ides e idence no a ailable om neoecology. Obse a ions a he human
scale (mic oscale) a e insu icien o gene alize abou ecosys em e olu ion.
On he o he hand, palaeoecology is a heo izable discipline. Theo y gi es
mo e s imuling goals han desc ip i e econs uc ion o pas .en i onmen s, o
local clima ic his o ies. I is hus necessa y, no only o gene a e mo e and
mo e in o ma ion, bu also hink abou i , unde an ecological amewo k.
Hil1
(1981)
posed he ques ion: -Why s udy palaeoecology?-. The answe
seems o me: -Fo a be e unde s anding o biosphe e-, he same han o :
-Why s udy ecology?-.
I
Acknowledgemen s
The o iginal nanusc ip was i np o ed a e he c i ica1 e ision o
R.
Ma gale ,
C.
Schube , and
T. Vegas-Villa ubia. The e ision
by
wo unknown e e ees is also acknowledged. This wo k was
ca ied ou du ing he de elopmen o he esea ch p ojec SI-1843, suppo ed
by
CONICIT (C.
Schube , esponsible in es iga o ).
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