A paleobotanical and palynological study of holocene peat from the El Bosque mire, located in a volcanic area of the Cordillera Central of Colombia

Review of Palaeobotany and Palynology, 55 (1988): 19-72

19

Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

A PALEOBOTANICAL AND PALYNOLOGICAL STUDY OF HOLOCENE PEAT FROM THE EL BOSQUE MIRE, LOCATED IN A VOLCANIC AREA OF THE CORDILLERA CENTRAL OF COLOMBIA P. KUHRY Hugo de Vries Laboratory, Department of Palynology and Palaeo/Actuoecology, University of Amsterdam, Kruislaan 318, 1098 SM Amsterdam (The Netherlands) (Received September 22, 1987)

Abstract Kuhry, P., 1988. A paleobotanical and palynological study of Holocene peat from the E1 Bosque mire, located in a volcanic area of the Cordillera Central of Colombia. Rev. Palaeobot. Palynol., 55: 19-72. The influence of volcanic activity and climatic change upon regional and local vegetation developments during the last 5800 years in the area of the El Bosque mire has been traced t h r o u g h examination of a peat section collected from this mire, located ca. 4°45'N, 75°27'W, at a n elevation of 3650 m, in the Cordillera Central of Colombia. The 11 m long peat section was examined for all kinds of microfossils and macroscopical plant remains. At approximately 5800 yr B.P. a lava flow of the Nevado S a n t a Isabel volcano obstructed the E1 Bosque depression, resulting in the formation of a n area of impeded drainage in which a mire vegetation developed. The former vegetation in the surroundings of the depression was seriously affected by the eruptive phase and was mainly replaced by pioneer grasslands. After about 125 years forest vegetation re-appeared. From ca. 5675 to 2160 yr B.P. the vegetation surrounding the mire consisted mainly of a dense high-Andean dwarf forest of Polylepis. The stands of vegetation at the boring site itself developed from a n aquatic vegetation in small pools with Azolla and Drepanocladus to relatively drier vegetation types with Carex, Disterigma and Campylopus. During this period regional and local vegetation types were little affected by volcanism, with the exception of a n interval between ca. 3900 and 3300 yr B.P. From ca. 2160 yr B.P. onwards the influence of volcanic activity upon the vegetation cover in the E1 Bosque area increased, Polylepis dwarf forest being replaced by a more open type of high-Andean forest. Disturbances due to volcanic activity also resulted in consecutive vegetational successions in the mire. Although volcanic activity has been the main factor to which changes in the regional vegetation types can be attributed, a more or less gradual lowering of the forest line as a result of a slight deterioration of the climate during the late Holocene can also be deduced from the E1 Bosque pollen diagrams.

Resumen Por medio del arAlisis de u n a secci6n de t u r b a se estudi6 la influencia de la atividad volcAnica y de los cambios dim~ticos sobre el desarrollo de la vegetaci6n regional y local durante los dltimos 5800 afios en el Area del p a n t a n o de E1 Bosque, localizado ca. 4°45'N, 75°27'W, a u n a a l t u r a de 3650 m, en la cordillera Central de Colombia. En la secciSn de t u r b a de 11 m de longitud se examinaron toda clase de microfSsiles y restos bot~ni~os macrosc6picos. En aproximadamente 5800 afios A.P., u n flujo de lava del volcAn Nevado S a n t a Isabel obstruy5 la depresiSn de El Bosque, form~ndose un Area pantanosa. La vegetaciSn en los alrededores de la depresi6n fu~ seriamente afectada pot la(s) erupci6n(es), desarrollAndose comunidades pioneras de gramineas. DespuAs de unos 125 afios u n a vegetaciSn arbSrea reapareciS. Desde aproximadamente 5675 a 2160 afios A.P. la vegetaci6n en los alrededores del p a n t a n o consistia E K q R A . ~ 7 1 ~ I ~ N . q .~N

( ~ 1Q~R ~ 1 ~ { ~ v

~ei~nr~ P n h l ~ h A r ~

R V

20 principalmente de un denso bosque enano alto-andino de Polylepis. La vegetaciSn local en el sitio del sondeo se desaroll0 de una vegetaci6n acuAtica de Azolla y Depranocladus a tipos de vegetaci0n relativamente m~s secos con Carex, Disterigma y Campylopus. Durante este periodo la vegetaciSn regional y local fueron poco afectadas por volcanismo, con la excepci6n de un periodo entre aproximadamente 3900 y 3300 afios A.P. Desde aproximadamente 2160 afios A.P. la influencia de ]a actividad volc~nica sobre la vegetaci6n en el ~rea de E1 Bosque aument6. E1 bosque enano de Polylepis fu~ reemplazado por un tipo de bosque alto-andino m~s abierto. En el pantano tuvieron lugar sucesiones vegetales consecutivas como consecuencia de la inestabilidad causada por el volcanismo. Aunque ta actividad volcAnica ha sido el factor principal orginando los cambios en la vegetaci6n regional, tambi~n es evidente un descenso mAs o menos gradual del llmite del bosque durante el Holoceno tardio, como consecuencia de un ligero empeoramiento del clima. d e p r e s s i o n is b o u n d e d b y n e a r l y v e r t i c a l w a l l s o n its n o r t h e r n , e a s t e r n a n d s o u t h e r n sides, a n d is o p e n to t h e s o u t h w e s t . L a v a flows f r o m the Nevado Santa Isabel volcano have spilled d o w n i n t o the n o r t h w e s t e r n q u a d r a n t of the d e p r e s s i o n (Figs.2 a n d 3). I n A p r i l 1979, a 9 m l o n g p e a t s e c t i o n (EB I) w a s c o l l e c t e d i n t h e m i r e (see Fig.3). T h e b a s e of t h e s e d i m e n t a r y s e q u e n c e w a s n o t r e a c h e d .

Introduction

T h e E1 B o s q u e m i r e (ca. 4°45'N, 75°27'W; e l e v a t i o n : 3650 m) lies o n t h e w e s t e r n s l o p e s of t h e C o l o m b i a n C o r d i l l e r a C e n t r a l i n t h e volc a n i c p a r t of E1 P a r q u e N a c i o n a l N a t u r a l Los N e v a d o s (Figs.1 a n d 2), o c c u p y i n g t h e v a l l e y b o t t o m of a s m a l l c r a t e r f o r m e d s h o r t l y a f t e r t h e e n d of t h e l a s t g l a c i a t i o n (Herd, 1974). T h e

80 o

750

70 o

10 o .

5o_

00

rL

0

,0 20

30 40

s0ko

y

)

Fig.1. Schematic map of the Parque Nacional Natural Los Nevados area. The E1 Bosque area is located within the dotted quadrangle which is enlarged in Fig.2. Also indicated are the E1 Cedral weather station (point A) and the vegetation transects (see section on "vegetation and climate").

21 75025'W

0'N

~5'N

"~'~

River

Q

Lake Lava flow

i

0

1 .~

2

3

4

5km

Boring site

Fig.2. Schematic map of the SW part of the Parque Nacional N a t u r a l Los Nevados, showing the location of the E1 Bosque area.

A pollen diagram of the EB I section was published by Kuhry et al. (1983). This paper reported the results of the first palynological study in this area, comprising 4 sections of peat and lake sediments along an altitudinal gradient (3650-4180 m) through the upper part of the Otfin valley. In August 1981, another drilling was carried out at approximately the same place as the first (see Fig.3). In this section (EB III) the subsoil was reached at a depth of 11.15 m. The complete EBI section (9m) and the lower part of the EB III section (9-11.15m) have been used for the present study. This composite section has been called the EB I and III section. The handborings were carried out with a Dachnovsky sampler. The deposits consist of peat with intercalated tephra layers (ashes and sands). At several depths the sedimentary sequence is interrupted by water layers. The composite sedimentary column of the EB I and III section is presented in detail in Fig.4. A chronostratigraphy of the tephra layers deposited over the last 20,000 years, in the E1 Parque Nacional Natural Los Nevados area is

Fig.3. View of the E1 Bosque depression from the top of the lava flow (N). The boring site is indicated by a n arrow.

22 0 m

14

EL BOSQUE I & l l l 1

(3.650m)

2

3

4

5

6

7

LEGEND

~

light

brown

peat

~

dark

brown

peat

8

9 volcanic ash

10

volcanic sand and iapilli

water

plant remains were taken in between the microfossil samples, their volume varying from 20 to 50 cm 3. They were treated for 5 min with a gently boiling 5% aqueous KOH solution for deflocculation, and subsequently cleaned of fine debris by rinsing through a 175 #m sieve. As mentioned above, microfossil and macrofossil samples were taken in an alternate fashion. Therefore, we may in some cases, expect disconformities between the local elements in the microfossil diagrams and the macrofossil record. A major change in the local vegetation elements might be anticipated at the 9 m level, because the E B I and E B I I I sections were probably not collected at exactly the same place. At four levels samples were cut out for 14C dating (see Fig.4). These samples were dated at the 14C Laboratory of the Groningen State University (see Table I). Approximate time calculations have been carried out with the help of these datings, by assuming that the rates of peat deposition between any two 14C samples were constant. With the aid of the time calculations it was possible to estimate the duration and age of the different periods corresponding with the subzones and local phases as distinguished in the EB I and III diagrams.

layers

11

Fig.4. Composite sedimentary column of the EB I and III section.

presented by Herd (1974), Thouret (1984) and Salomons (1986). The palynotogical and paleobotanical analyses of the material were carried out by the author at the Hugo de Vries Laboratory, Department of Palynology and Palaeo/Actuoecology, in Amsterdam. In the laboratory, 1-cm thick samples (2-4 cm 3) were taken at every 12.5 cm for the analysis of microfossils (pollen, spores, etc.). For the preparation of the slides, the samples were treated for 10 min with a boiling 10% aqueous KOH solution followed by acetolysis. Samples for the analysis of macroscopical

Present climate and vegetation

The E1 Bosque area, located ca. 4°45'N of the equator and about 3650 m above sea level, has a tropical montane climate. The mean annual temperature is abo~at 6-7°C. Throughout the year the amplitude of the mean monthly temperature is very small. However, daily differences in temperature may be considerable. There are two wet and two dry seasons, the wet ones occurriztg i n April to May and in October to November. The mean annual precipitation is about I500~-2{E~ ram. No exact climatological d a t a from the E1 Bosque area are avai~ble. T e m p ~ a t u r e and rainfall graphs, rel~resentingthe conditions at the E1 Cedral weather station (4°47'N, 75°32'W; elevation 2150 m) are given in Fig.5.

23

TABLE I Radiocarbon dates, EB I and III section Section

Laboratory number

Sample number

Depth (cm)

Age estimated (yr B.P.)

EB EB EB EB

GrN GrN GrN GrN

COL COL COL COL

287.5-297.5 887.5-897.5 947-955 1100-1110

2040 _ 80 4790 + 70 5240 ± 90 5760±80

I I III III

10268 9753 11885 11886

306 282 364A 365

The area surrounding E1 Bosque mire lies just below the timberline of the high-Andean forest belt, but nowadays little is left of the original vegetation cover in the area. Especially during the last 15 years, large areas of forest have been destroyed by human interference. Only patches of partly secondary highAndean dwarf forest occur locally on the slopes of the crater wall and the surface of the EL

CEDRAL

mean

(2150m)

yearly precipitation: 2 7 7 5 . 7 m m

(1961 -1982> 500

400

300

200

100 film

J mean

F

M

A

M

J

J

A

S

0

N

D

yearly temperature: 1 4 . 3 ° C

16 14

12 0C Fig.5. Temperature and rainfall conditions at the E1 Cedral weather station (for location see Fig.l).

lava flow (see Fig.3). These stands are mainly composed of Compositae (Gynoxis, Diplostepiurn) and Rosaceae (Hesperomeles, Polylepis). Other frequently represented woody taxa include Vallea, Gaiadendron, Rapanea, Oreopanax, Miconia and Monnina. The stands of vegetation in the mire are characterized by several floating plant communities forming a mosaic pattern. The community at the boring site is dominated by Carex cf. bonplandii and Senecio latiflorus with several moss genera (Pleuroziurn, Campylopus and Breutelia). Another community is dominated by Calarnagrostis ligulata and Epilobium. In small pools a pleustophytic community mainly consisting of Azolla filiculoides has developed. The regional vegetation types of the western slopes of the Cordillera Central will be discussed here only briefly in terms of indicator taxa useful from the palynological point of view for the reconstruction of the vegetation development in the surroundings of the E1 Bosque mire. The vegetation will be described on the basis of the altitudinal zonation of the Colombian tropical Andean vegetation as proposed by Cuatrecasas (1958) and the data of the Dutch-Colombian ECOANDES expedition of 1980 that included, among other things, a botanical exploration along transects through the western and eastern slopes of the Cordillera Central in the E1 Parque Nacional Natural Los Nevados area (see Fig.l). The preliminary results of the upper part of the transects have been published by Cleef et al. (1983). Characteristic taxa in the subandean forest belt are Acalypha, Alchornea and Cecropia. They are abundant in this zone and do not

24

extend beyond its upper limit at approximately 2350 m. The next vegetation belt, the Andean forest, in the E1 Bosque area reaches to approximately 3500m. It is dominated by Weinmannia forest (Weinmannietum) with Rapanea, Viburnum and Ilex. In relatively wet places Alnus is present. Between an elevation of approximately 3500m and 3700m highAndean (dwarf) forest elements are more frequently represented. Characteristic taxa include Compositae (Gynoxis, Senecio), Ericaceae (Gaultheria, Macleanea), (Hesperomeles and, locally, Polylepis). Hedyosmum, Urticales (excluding Cecropia) and Cyatheaceae have a rather wide altitudinal range but are especially frequent in the (upper) subandean and lower Andean forest belts. Melastomataceae (including Miconia), Solanaceae and Oreopanax are more or less equally represented in the subandean, Andean and high-Andean vegetation belts. Quercus, Podocarpus, Juglans and Myrica have not been recorded from the western slopes in the ECOANDES transect, but Quercus forms a distinct forest (Quercetum) in the Andean vegetation belt on the eastern slopes of the Cordillera Central. Dodonaea is a pioneer on eroded soils in the Andean forest belt. The altitudinal position of the forest line is mainly determined by the prevailing temperature, but differences in precipitation also have some influence. Generally speaking, the forest line rises with increasing precipitation. The grass paramo belt in the E1 Bosque area extends from approximately 3700 to 4300 m. The vegetation is characterized by bunchgrass communities (Calamagrostis, Festuca) with stem-rosettes of Espeletia (Compositae). Dwarf forest and scrub of Polylepis, Escallonia, Compositae (Ageratina, Senecio), Ericaceae (Vaccinium) and Hypericum occur as isolated patches in the grass paramo. The highest vegetation belt in the tropical Andes, the superparamo, is found above an elevation of about 4300m where the plant cover becomes sparser with increasing altitude. The highest peaks in the area, above an elevation of approximately 4800 m, have a permanent ice cap. Data on open water, mire and peatbog

communities in the area studied are very scarce. Cleef et al. (1983) have presented a first overview of these vegetation types, and Salamanca (1984) has given some phytosociological data concerning these communities, especially on those occurring above an elevation of 4000 m, but little is known of the mire vegetation types involved in the present study.

Results of the palynological and paleobotanical analyses

General remarks For the microfossil analysis of the samples, pollen counting usually continued until the arboreal elements within the pollen sum (trees and grasses) had reached a value of about 100. However, in some cases it was not possible to attain this number. The frequencies of pollen, spores and other microfossils recorded during the analysis were calculated as percentages of the: )ollen sum. The results of the microfossil analysis of the EB I and III section are shown in Figs.6, 7, and 8. The descriptions and illustrations of the newly recognized microfossils for this area are given separately at the end of the paper. In Fig.6 separate curves are drawn for all identified taxa (both those included and those not included in the pollen sum) that are indicative of regional vegetation development. In the general diagram, to the left of the separate curves, four groups of pollen sum taxa are distinguished, which express as clearly as possible the main composition of the regional vegetation in terms of altitudinal belts. These groups are given in Table II. Compositae, Ericaceae and Hypericum have been excluded from the pollen sum. These elements are of frequent occurrence in the high-Andean forest and also occur as isolated patches of dwarf forest and scrub in the grass paramo, but they are also present in certain mire vegetation types. At several levels in the EB I and III section macrofossils of these taxa have been found. The sharp fluctuations in the pollen curves of Compositae, Ericaceae and

EL BOSQUE I & III (3650m)

~E 2 ~.J

Oeneral REGIONAL

diogram

..J

VEGETATION 100

age in y r's B.P.

,~ -i ~m

20, l GrNI0265 2o4o~8o |

309

331

~.~

"~-'~

i i

562

~

....

755

f GrN 9753 4790+_70 ]

-----

7

GrN 118e5 5240+_.90 |

GrN 11886~ 576o± BO Subandean 0

((Sob andean -,~ AnOean 10

Fig.6. Regional vegetation diagram, EB I and III section.

20

30

Highandean 40

50%

6. . . . . . Param~ / Pioneer

300

o~

o

c~

c~D

y

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I & III

(3650mI LOCAL

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I

5** 607

E G

-FE

0

t

I

C

B

A

Di---+Hl-+b--il

0 100 0 10 20 30 40 50 60 70 90 90100 %

Fig.7. Local vegetation

diagram (pollen), EB I and III section.

~~

~ L

t

"7----

'

F

v

co m Go

r-.

\

\

EL

BOSQUE

I &Ill

(3650m) LOCAL age in yr's B.P.

VEGETATION

,~ -] cm se -1_ 72 169 207

GrN

0268 2040 ~ 80

I 90

L

1 /

309 331

J

J

I

562 607 -~- 616

V ese

H G F

736 755

E

°

k__

GrN 9753 479o~70 I GrN 11885 5 2 4 0 ~ 90 I

GrN 11886 5 7 6 0 ,:l: 8o I

0 100 0 10 20 30 4 0

Fig.8. Local vegetation diagram (fern spores and other mi~

{r,1~)

i

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60 70 80 90 100 %

~fossils), F,B I and III section.

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pp. 31-34

=,z~

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,AIdf'p LOCAL PHASES

H G F E

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pp. 35-38

r.n

EL

BOSQUE (3650m)

I & Ill c~ r_l

LOCAL

~ir~

= o_

•6 r e ' -

VEGETATION r.~

age

in

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yr's

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se -'1._ 72

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GrN 0268 2 0 4 0 : E 80 I

1 309 33!

J

mm

K

IE3 J m m n m m m m m m mm m m m m

562 607 "1._ 016 I - 8~s

hi

mm

G

Mm -

-

-

-

736 755

16

me

mmm m'--" mm ~P

mm m

m

E D

W, m

._._ m

•

m

m

._._ GrN 0753 4790*-70

J

C

m

mmm

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m

,,,

m

ml•mm

m

~=

m

m

-.--:,

mm

m

m

m mmmmmm m

G r N I1885 5 2 4 0 - 90 1

B

mm

m ,___.__ A

m

mira

m

m

G r N 11886 I 5760:[: 80

0 '5 110 ' 2'0 ' 3'0 ' 4'0'

5'0 i

500

Fig.9.Local vegetation diagram (macrofossils),EB I and III section.

I , I , I , I

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I '51

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E L B O S Q U E I & III, 3650M 14 C-DATINGS IN YEARSB.F

DEPTH IN CMS

R E G I O N A L V E G E T A T I O N DEV]

APPROXIMATE

U'I"HO~0GY

AGE IN YEARS B.P.

DISPLACEMENTSOFTHE VE(~TATIONBELTS IN ~ ~ATION (~.~-~ZONI~ EL BOSQUE A R E A DOMINANT T.~ ANDEANHIGHANDEANPARAMO I ~ BOSQUE

o ~ cm se -1_ ?2

t69 ~-- 90 Il l

2O7

GrN 10268 2040~:S0

I

309 331

dwarf for sUmdsoi and Pol

2160

,562 607 "1.- 616 736

--I 656

Den ~ghaE dwarf fc

755 -4300

GrN 9753 47904-70 GrN 11885

524o_+9o

I

5675 CaN 11886

57eo~.so I

I

1115 ^

5800 II

Fig.10. S u m m a r y of t h e m o s t i m p o r t a n t d a t a c o n c e r n i n g t h e r e g i o n a l a n d l o c a l v e g e t a t i o n d e v e l o p m e n t s i n t h e a r e a of t h e E B o s q u e mire, r e c o r d e d in t h e EB I a n d III section.

~LOPMENT BELTAND XAIN THE ;AREA

nt with Vallea yie~

DATA ON OTHER VEGETATION BELTS

G ~ A E MAXIMA

CHARCOAL LAYERS

~ A LAYERS

. . ; .. • ....-

71. ."

Position of the mdean forest belt and paramo vegetation belt u at p r e s e t Dodoeaea in the andean fon=t belt, indicating some instability.

APPROXIMATE LOC, AGE IN YEARS B.P.

WATERLAYERS

L

II00 K 1865 J 2160

:.:-:::.

I

Andean forest with Weinnumnia near the ~ Seeque are,. Paramo vegetlionata shorter distance from the area than before 4300 B.P.,but mill further away thaa at pnmmt

3330 3415

ss

H G

3735 3875

F E

t of 4230

I pi'

D 4610

C

.-.:-.:..-...!

Wet ande~ forest with Weinmmmia and Alnus very near the El Be~lue are& Pammo veget~on belt far ~ o v e the area.

5275

I

B 5525 A

58OO

I

1

c

J

t

pp. 39-44

LOCAL VEGETATION DEVELOPMENT CHA~GES IN THE VEGEFATION TYPES AT THE BORINGSITE IN THE MIRE OF EL BOSQUE AQUATIC RELAT.WET RELAT.DRY

J

IX~[INANT TAXA AT THE BORINGSITE IN T I ~ MIRE OF F.,LBOSQUE

Bn=utelia c l a ' y ~ a

Rumea

C~ex cf bonplandii, Hypcricum, Compositae

Hym©uophyllum,C.ampylOlpUS

Rhyachostcgiella compacta, Plcurozium schttberi Disterigma empetrifolium Colobaathua quit=nsis,Lac~milla, D/sterigma empetritolium Carex elboW.and// Rhymhoaqzlla compaOa, Ca~x cf bonplandii Encace|e (probably Dis~ngma cmpelritolium) Cam ( ~ b , h ~ C b o n ~ m ~ B . ~ m i , pleurozium schreberi3?.hvnchosteaiella comDacta

Carex cf bonplandii,Disterigma empcUifolium, Carapylopc=

"Ualli[nche Dr¢ nocladus a d ~ Campylopua, Dimm'igmt empetrifolium J C.

OTHER IMPORTANT TAXA AT THE BORINGSIT~ IN THE MIRE OF EL BOSQUE

Azolla filiculo/d~ Dn~paaockghmaduncua, Tillaea ~ludosa Lachmilla. Hyl~cum, C.m'cx cf bcaplandii, C.ampylopm

J /

Azolla filiculoi&s, Tillaea paludosa, Momia meriden*¢, Cruciferae (probably Cardamim bonariensis) S¢~¢~gnummageUanicum ozium Khrcberi Oen~anacca¢, Campylopus $i~anum Sc~ Cu~oidata Azol1"afdicu]oidcs

)N T.A UE

for ~o! Po]

[-lymenoc~yllum Bryum, Briichythecium

Bryum

Pletwozium ~ r e b e r i ~NlonUa mendcfls¢, L~al'cg~ boflo plandii, C.arda,mine bonariensis l.¢ptdopflum d mu~llen Breutelia ch~sea, CalliergoQ cf s~ntolgim Ludwij~a, Br,/aua, Brachythecium gall~tric~e . . . . Lm"o~mltic oofllrlCnSm L~l~odontium lonsicaule Brachythecium S ~ a a a m Sea C ~ d a t . Bryum

~en ha~ ~fc lyl,

Tillaea paludcsa,

SphagnumSectCmpida~

Azollt fdiculo~a.'s, Drcpanocladta aduao~

Ludwigia, Carex, Hy¢h-ocotyl©ranunoulcg&s, Eleachm'is acicularis, Tillaea paludosa, C.ardamia¢ boaar/emfis, Canitricl~, BiA-ns

/ m

E

45 TABLE II Groups of pollen sum taxa in the general diagram, EB I and III section (see Fig.6) Subandean e l e m e n t s

Acalypha Alchornea Cecropia Vismia Hieronima Eugenia Heliocarpus Billia Subandean-Andean and Andean e l e m e n t s Urticales (excl. Cecropia)

Hedyosmum Brunellia Clusia Abatia Sapium Weinmannia Rapanea Viburnum Ilex Alnus Coriaria Salix

Hypericum seem to be of local origin, and for this reason they are included in the local vegetation diagram. Some gramineous taxa (e.g. Calamagrostis ligulata) also occur in mire vegetation types, but not a single plant remain or seed of these taxa was encountered in the macrofossil analysis. Therefore, the changes in the pollen curve of Gramineae do not seem to be of local origin. The pollen, fern spore and other microfossil curves shown in Figs.7 and 8 are used to reconstruct, in combination with the macrofossil record, the local vegetation development. For the macrofossil analysis of the samples, macrobotanical remains were counted (seeds, leaves, etc.) or alternatively assessed as volume percentages (epidermal remains, mosses, etc.) of the sample used (Fig.9). Countings were recalculated on the basis of a constant sample volume of 25 cm 3. The descriptions and illustrations of the macrofossils found in the

Subandean-Andean and Andean e l e m e n t s (continued)

Drimys Ternstroemia Bocconia Melastomataceae (incl. Miconia) Solanaceae

Oreopanax Quercus Podocarpus Juglans Myrica Panopsis Proteaceae (excl. Panopsis)

Dodonaea High-Andean elements

Hesperomeles Monnina Gaiadendron Vallea Polylepis Paramo and/or pioneer grassland elements Gramineae

EB I and III section are given separately at the end of the paper. The regional vegetation diagram (Fig.6) and the local vegetation diagram (Figs.7-9) have been zoned independently. The zonation of the regional vegetation diagram is based on major fluctuations in the representation of the groups in the general diagram. Subzones are additionally distinguished on the basis of changes in the representation of individual taxa, the pollen production ratios (Grabandt, 1980, 1985; Melief, 1985) of these taxa being taking into account. For instance, Weinmannia, Rapanea, Dodonaea, Polylepis and VaUea are poor pollen producers. The zones are indicated by roman cypher symbols and are numbered from bottom to top while subzones are indicated by letter symbols. The subdivision of the local vegetation diagram is primarily based on the macrofossil record. On the basis of fluctuations in the representation of

46 the local vegetation elements a sequence of local phases, indicated by capital letter symbols and also named from bottom to top, have been distinguished. A description of the zones and subzones, and subsequently of the local phases, is given below.

Zonation of the regional vegetation diagram (Fig.6) Zone I (1115-1080 cm) This zone is characterized by high percentages of Gramineae (up to 40%) and low percentages of Polylepis. Alnus attains relatively high values.

Zone H (1080-323 cm) The percentages of Polylepis are high (_> 25%) throughout the zone. The percentages of Gramineae are, generally speaking, low (_< 25%). Weinmannia reaches, over the whole, relatively high values.

Subzone IIa (1080-811 cm). In this subzone the percentages of Polylepis are somewhat higher than in subzone IIb. The Gramineae values are very low. Alnus reaches relatively high values as does Rapanea in the lower part of the subzone. Subzone IIb (811-323 cm). The percentages of Gramineae are higher than in subzone IIa, while the curve of Polylepis shows slightly lower percentages.

Zone III (323-0 cm) This zone is characterized by high values for the Gramineae (up to 50%). At the beginning of the zone there is a sharp decline in the curve of Polylepis. In the remaining part of the zone the percentages of Polylepis remain low (_< 10%). VaUea and Dodonaea are present. In addition to the general tendency of the Gramineae curve described in the zones, fourteen maxima of Gramineae, also numbered from bottom to top, can be distinguished in the diagram.

Subdivision of the local vegetation diagram (Figs. 7- 9) Local phase A (111~1035 cm) Macroscopic plant remains of Azolla filiculoides and Drepanocladus aduncus are very abundant. Seeds of Eleocharis acicularis and Bidens, and megaspores of Azolla filiculoides are found in large quantities. Seeds of Cardamine bonariensis and Carex sp. 3 are relatively frequent. In the microfossil diagrams, pollen of Cyperaceae and Cruciferae show very high frequencies. The curves of Callitriche, Hydrocotyle and Ludwigia pollen and of Azolla massulae show some maxima.

Local phase B (1035-961 cm) This phase is characterized by high percentages of Cyperaceae remains (T2). The fungal microfossils t l l , Anthostomella fuegiana, t13 and Gaeumannomyces cf. caricis are very frequent. Callitriche, Ludwigia and Tillaea pollen, and fungal spores of type t14 show maxima.

Local phase C (961-862 cm) In the macrofossil diagrams, Azolla filiculoides and Drepanocladus aduncus are very abundant. Tillaea paludosa remains are present at the base and the top of the phase. Seeds of Eleocharis acicularis and Hydrocotyle ranunculoides are found in large quantities. Seeds of Carex sp. 3 in the lower part and of Cardamine bonariensis and Bidens in the upper part of the phase are relatively abundant. The pollen spectra of Cyperaceae, Hydrocotyle, Callitriche and Ludwigia, and the fungal microfossils t l l , Anthostomella fuegiana and t13 show maxima.

Local phase D (862-800 cm) Epidermal remains of Tillaea paludosa are very frequent. Remains of Azolla filiculoides, Drepanocladus aduncus and Sphagnum sect. Cuspidata are also abundant. In the microfossil diagrams, pollen of Cyperaceae and Callitriche, monolete verrucate

47 spores, and the fungal microfossils t11, Anthostomella fuegiana and t13 show high maxima.

Local phase E (800-722 cm) This phase is characterized by the continuous presence of Campylopus remains. In the lower part of the phase Bryum and Sphagnum sect. Cuspidata are frequent. In the upper part Brachythecium and T21 remains are abundant, and Leptodontium longicaule is also found. Seeds of Lachemilla are very frequent. Seeds of Carex cf. bonplandii and Hypericum are found in relatively high amounts. T39 branches are also found. The percentages of Cyperaceae and Compositae pollen are high, and fungal microfossils of type t13 show maxima. In the middle part of the phase shells of Assulina and conidia of Helicoon pluriseptatum are abundant. At the end of the phase Ericaceae pollen, loricae of Callidina and the fungal spores t14 and t16 show maxima.

Local phase F (722-698 cm) Macroscopic remains of Azolla filiculoides and type T21 are continuously present in high frequencies. In the middle part of the phase remains of Tillaea paludosa and Drepanocladus aduncus, and in the upper part seeds of Callitriche and Cardamine bonariensis are very abundant. The fungal microfossils tll, Anthostomella fuegiana, t13 and, at the end of the phase, Gaeumannomyces cf. caricis are very frequent.

Local phase G (698-582 cm) In the macrofossil diagrams, Campylopus and T21 remains are abundant. Furthermore, from the base to the top of this phase the following sequence of mosses is found: first, Brachythecium and Bryum; halfway up, Breutelia chrysea and Calliergon cf. sarmentosum; and finally, Lepidopilum cf. muelleri. All kinds of macrofossils of Ericaceae (seeds, Disterigma empetrifolium fruits, flowers, branches, and D. empetrifolium leaves) are found. The pollen spectra of Ericaceae, Compositae

and Ludwigia, fungal microfossils of type t13, and loricae of Callidina show high maxima.

Local phase H (582-547 cm) Macroscopic remains of Drepanocladus aduncus and Sphagnum sect. Cuspidata are very frequent. Seeds of Callitriche and Montia meridense, and to a lesser extent of Carex cf. bonplandii and Cardamine bonariensis are abundant.

Local phase I (547-323 cm) Macroscopic remains of Campylopus are very abundant. At the base of this phase there is a very high maximum of Pleurozium schreberi, while in the middle part Bryum reaches very high values. Seeds of Carex cf. bonplandii and all kinds of macrofossils of Ericaceae (seeds, Disterigma empetrifolium fruits, flowers, branches, and D. empetrifolium leaves) are frequent. The pollen spectra are characterized by high frequencies of Cyperaceae, Ericaceae, Compositae and Gentianaceae. Furthermore, loricae of Callidina and shells of Assulina show high maxima, while conidia of Helicoon pluriseptaturn are relatively abundant.

Local phase J (323-277 cm) In the lower part of this phase Rhynchostegiella compacta and Pleurozium schreberi, and, in minor abundance, Brachythecium and Bryum remains are found. Seeds of Carex sp. 2 are abundant. In the middle part of this phase the sample taken for ~4C dating left no material for the analysis of macrofossils. The percentages of Cyperaceae pollen are high. Furthermore, the following sequence of microfossils is found from the base to the top of the phase: in the lower part a maximum of ascospores of Anthostomella fuegiana; in the middle part maxima of Umbelliferae pollen (belonging to the genus Eryngium) and of Hymenophyllum spores; and in the upper part minor maxima of pollen of Ericaceae, loricae of Callidina and the fungal microfossil t13.

48

Local phase K (277-188 cm) In the lower part of phase K macroscopic remains of RhynchostegieUa compacta and Azolla filiculoides, and seeds of Carex cf. bonplandii are present. In the middle part, first Sphagnum sect. Cuspidata and seeds of Carex cf. bonplandii, and then Campylopus, seeds of Colobanthus quitensis and Lachemilla, and macrofossils of Ericaceae (seeds, Disterigma empetrifolium fruits, branches and D. empetrifolium leaves), are found. Finally, in the upper part macroscopic remains of Pleurozium schreberi and Sphagnum magellanicum are very frequent. Here Disterigma empetrifolium leaves also show a maximum. The pollen spectra of Caryophyllaceae (Colobanthus/Arenaria-type), Lachemilla, Ericaceae and Gentianaceae show maxima. Ascospores of Anthostomella fuegiana in the lower part, loricae of Callidina in the middle part and conidia of Helicoon pluriseptatum in the upper part, also show maxima. Charcoal is found at the base and at the top of this phase.

Local phase L (188-0 cm) In the lower part of phase L, RhynchostegieUa compacta and Pleurozium schreberi remains are abundant, and Tillaea paludosa and AzoUa filiculoides are present. Here, seeds of Montia meridense are found. In the middle part Campylopus and seeds of Carex cf. bonplandii are frequent. Breutelia chrysea and seeds of Rumex are abundant in the upper part of the phase. In the microfossil diagrams, Cruciferae, Compositae and Hypericum show maxima. Hymenophyllum spores are very frequent halfway up the phase. The fungal microfossils Gaeumannomyces cf. caricis, t16 and t18, and loricae of Callidina and shells of Assulina are abundant in the upper part. Fungal spores of type t14 are frequent throughout the phase. Charcoal is found in this phase.

Remarks on the regional v e g e t a t i o n development The development of the regional stands of vegetation in the surroundings of the E1

Bosque depression shows two different features that are described below. The first corresponds with a general development of the stands of vegetation in the area. After a short period (zone I), from ca. 5800 to 5675 yr B.P., in which pioneer grasslands covered large areas in the surroundings of the E1 Bosque depression, a vegetation dominated by a dense high-Andean dwarf forest of Polylepis developed (zone II). During this period (ca. 5675-2160 yr B.P.) the Andean forest belt was closer to the area than it is at present, as indicated by the relative abundance of the Andean element Weinmannia in the pollen diagram. The relative abundance of Alnus between ca. 5800-4300 yr B.P. (subzone IIa) is most probably indicative of a wetter type of Andean forest. Especially during this period the paramo vegetation belt lay far above the E1 Bosque depression. After ca. 2160 yr B.P. the area covered by Polylepis dwarf forest became strongly reduced and the paramo vegetation belt, dominated by bunchgrass communities shifted closer to the E1 Bosque depression (zone III). However, a more open type of highAndean forest was still present in the area as indicated by the presence of Vallea and Polylepis. The relative abundance of Dodonaea in the pollen diagram reflects an increased instability in the Andean forest belt during this period. In addition to the general development of the regional stands of vegetation described above, including the more or less gradual approach of the paramo vegetation belt to the E1 Bosque depression during the late Holocene, a second feature can be distinguished. The maxima of Gramineae pollen superimposed upon the general tendency of this curve correspond with short intervals in which forest vegetation types were (partially) replaced by open grasslands. These intervals can be correlated with the beginning of the sediment deposition (maximum 1), tephra layers (maxima 2, 3, 4, 7, 8, 13, and 14), water layers (maxima 5, 7, 10, and 12) and/or charcoal layers (maxima 11, 12, 13, and 14).

49

Reconstruction of the local vegetational development A first survey of the macrofossil and local microfossil diagrams shows that almost all taxa are not clearly restricted to definite local phases. Therefore, the reconstruction of the local vegetational successions is based on dominance of the different taxa in the various local phases. From local phases A - D (ca. 5800-4230 yr B.P.) the local stands of vegetation were dominated by a pleustophytic community in small pools with Azolla filiculoides and Drepa. nocladus aduncus. Small patches of Ludwigia scrub, with Carex and Hydrocotyle ranunculoides, were also present (local phases A-C). Occasionally, stands of other aquatic taxa, such as Eleocharis acicularis, Tillaea paludosa, Cardamine bonariensis, Callitriche and Bidens were growing at the boring site. The succession towards the drier vegetation types of local phase E is characterized by a higher abundance of TiUaea paludosa and Sphagnum sect. Cuspidata (local phase D). From local phases E to I (ca. 4230-2160 yr B.P.), relatively drier vegetation types tended to dominate at the boring site, twice interrupted by short intervals in which aquatic or relatively wet vegetation types re-appeared (local phases F and H). During local phase E (ca. 4230-3875 yr B.P.) a community dominated by Carex cf. bonplandii, LachemiUa and Campylopus, with Hypericum dwarf shrub developed locally. Mosses characteristic of this vegetation type, such as Bryum, Brachythecium and Leptodontium longicaule, were present. Occasionally, Sphagnum sect. Cuspidata was also growing locally. In local phase F (ca. 3875-3735 yr B.P.) an aquatic vegetation type dominated by Azolla filiculoides re-appeared, with some stands of

Tillaea paludosa, Cardamine bonariensis, Callitriche and Drepanocladus aduncus. The beginning of this phase lies just above a water layer. During local phase G (ca. 3735-3415 yr B.P.) a relatively drier vegetation type developed with

Disterigma empetrifolium, Campylopus, Calliergon cf. sarmentosum, Lepidopilum cf. muelleri

and Breutelia chrysea. The succession from the previous aquatic phase towards this drier vegetation type started with stands of Ludwigia scrub, with Bryum and Brachythecium. The presence of Lepidopilum cf. mueUeri coincides with a maximum of branches and leaves of Ericaceae, probably indicating that this epiphytic moss has been growing upon Disterigma empetrifolium, a dwarf shrub. Relatively wetter vegetation types re-appeared for a short timespan (ca. 3415-3330 yr B.P.) in phase H. Stands of Callitriche, Montia meridense and Carex cf. bonplandii, with Drepanocladus aduncus and Sphagnum sect. Cuspidata were present locally. The beginning of this phase coincides exactly with the top of a water layer. During local phase I (ca. 3330-2160 yr B.P.) stands of Carex cf. bonplandii, Disterigma empetrifolium and Campylopus dominated at the boring site. Occasionally, Pleurozium schreberi and Bryum were present. In local phases J, K, and L (ca. 2160 yr B.P.-present) successions from relatively wet or even aquatic vegetation types towards drier ones have been grouped in individual local phases. The beginning of the local phase J (ca. 2160-1865 yr B.P.) correlates with the top of a water layer. First, stands of Pleurozium schreberi and Rhynchostegiella compacta, with Brachythecium and Bryum (also present at the beginning of local phases E and G) were present. Subsequently, stands of Carex (probably C. cf. bonplandii), Eryngium, Hymenophyllum, and finally also of Ericaceae (probably Disterigma empetrifolium) developed. The presence of RhynchostegieUa compacta at the beginning of this and the next two local phases is remarkable. This moss, which seems to be reliably identified, has not been previously recorded from South America. Further, the ecology of the species, which is said to prefer seepage areas on rocky subsoils, does not agree with my findings. Again in phase K (ca. 1865-1100 yr B.P.) a vegetational succession took place. The beginning, which coincides with a charcoal layer, is marked by the presence of Carex cf. bonplandii, Azolla filiculoides and Rhynchostegiella compacta. Later

50 on, the vegetation was more dominated by Carex cf. bonplandii and Sphagnum sect. Cuspidata. Subsequently, a vegetation type dominated by Colobanthus quitensis, Lachemilla, Disterigma empetrifolium, Gentianaceae and Campylopus was present at the boring site. Finally, stands of Disterigma empetrifolium, with Pleurozium schreberi and Sphagnum magellanicum, occurred locally. In local phase L (ca. 1100 yr B.P.-present) the succession started with Rhynchostegiella compacta and Pleurozium schreberi, but also Azolla filiculoides, Tillaea paludosa, Montia meridense and Cruciferae (probably Cardamine bonariensis) were present. The beginning correlates with the top of a water layer and some charcoal has been found. Subsequently, stands of Carex cf. bonplandii, Hypericum, Compositae, Hymenophyllum and Campylopus developed, Prior to the modern vegetation stands at the boring site, a vegetation type with Rumex and Breutelia chrysea was present locally. C o n c l u s i o n s and d i s c u s s i o n In Fig.10, the most important data concerning the regional (B) and local vegetation (D) developments are summarized. The intervals with maxima of Gramineae, tephra layers, charcoal layers and water layers are indicated schematically (C). At the left side of the figure, the 14C datings and the sedimentary column are also given (A). The general development in the regional vegetation types (Fig.10B) can be ascribed to climatic changes. During the middle Holocene the mean annual temperature was slightly higher than at present. A dense Polylepis dwarf forest dominated in the area. The Andean vegetation belt with Weinmannia was closer to the E1 Bosque depression than at present, while the paramo vegetation belt lay far above the area, especially during the period lasting until ca. 4300 yr B.P. The very high position of the timberline in this period was due, in addition to a higher mean annual temperature, to a higher effective precipitation which is reflected in a wetter type of Andean Weinman-

nia forest with Alnus. In the late Holocene the climate became colder, resulting in the conditions prevailing at present. The vegetation cover in the surroundings of the E1 Bosque depression changed towards a more open type of high-Andean forest, with stands of Vallea and Polylepis. The paramo vegetation belt shifted closer to the area. Obviously, the warmer period in the middle Holocene corresponds with the Hypsithermal period also recorded in other sections in the Parque Nacional Natural Los Nevados area (Kuhry et al., 1983; Melief, 1985; Salomons, 1986) and the Cordillera Oriental (Van Geel and Van der Hammen, 1973). At approximately 5800 yr B.P. a lava flow of the Nevado Santa Isabel volcano obstructed the E1 Bosque depression, giving rise to an area of impeded drainage in which a mire vegetation developed. This age corresponds rather well with the age (ca. 5400 yr B.P.) calculated by extrapolation in the Laguna de O t f n IIb section (Kuhry et al., 1983) for the same lava flow that also caused the formation of the Laguna de Otfn. In the local vegetation development (Fig.10D) a general tendency towards drier vegetation types can be recognized. First, predominantly aquatic communities with, among others, Azolla filiculoides and Drepanocladus aduncus were dominant. Later on, drier vegetation types developed with Carex cf. bonplandii, Disterigma empetrifolium and Campylopus as dominant elements. The transition towards generally drier vegetation types took place around ca. 4230 yr B.P., a date that corresponds rather well with the end of the wetter period also recorded in the regional vegetation development. Therefore, the general development in the local vegetation types seems to be partially induced by climatic changes, although autogenic processes, such as the filling up of the sedimentary basin, also played a role. Furthermore, both the regional and local vegetation types show short intervals in which remarkable changes took place. The beginning of manifest local successions always coincides with the top of a water layer or a charcoal

51 layer (see Fig.10C-D), while periods in which grassland replaced large areas of forest generally correspond with tephra layers (lava flow, ashes and sands), charcoal layers and/or water layers (see Fig.10C). These changes seem to be induced by volcanic activity. Also the water layers and, subsequently, the local vegetational successions are most probably the result of volcanic activity. Generally speaking, the water layers can be correlated with the highest maxima in the Gramineae curve (see Figs.6 and 10C) indicating that during these periods the influence of volcanic activity upon the vegetation cover in the E1 Bosque area was most disastrous. As a consequence of volcanic eruptions large areas of forest were replaced by grasslands. The water storage and/or evapotranspiration changed with the vegetation cover, which resulted in a higher water level in the E1 Bosque depression. This phenomenon is also very clearly recorded in another small sedimentary basin located in the Colombian Andes (Helmens and Kuhry, 1986; Kuhry, 1988). Subsequent to the rise of the water table, a vegetation succession started from aquatic or relatively wet communities towards again drier vegetation types. The exclusive deposition of tephr a layers had a less pronounced influence upon the local vegetational development. Especially in the period from ca. 2160 to 1100 yr B.P. the influence of volcanic activity seems to have been important. Consecutive local successions, charcoal layers in the peat and the presence of Dodonaea in the Andean forest belt are all indicative of higher instability during that time. The periods with a high volcanic activity at approximately 5800, 3900-3300 and 2160-1100 yr B.P. correspond rather well with those mentioned in the literature (Herd, 1974; Kuhry et al., 1983; Thouret, 1984; Melief, 1985; Salomons, 1986). The behavior of individual taxa such as Polylepis and Vallea in the regional vegetation types, and of all local vegetation elements, is difficult to explain in detail, because of the lack of precise phytosociological and autecological data. For example, the sharp decrease of

Polylepis after ca. 2160 yr B.P. could be the result of the deterioration of the climate, of the increased volcanic activity or even of other aspects such as low fire resistance, human influence, etc. Local vegetational successions cannot be interpreted in a more comprehensive manner until the modern mire ecosystems have been studied in greater detail, including all biotic and abiotic factors involved. Nevertheless, the present study is a fine example of the influence of volcanic activity and climatic changes upon regional and local ecosystems in a tropical Andean area. Descriptions and illustrations o f the microfossil types

Pollen types tl:

t2:

t3:

t4:

t5:

t6:

Abatia (Flacourtiaceae). Plate I, la, b. Grain prolate to subspheroidal, amb triangular, tricolporate, microreticulate. Colpi long, with a colpus transversalis and costae colpi. Size: 33-28 × 25-20 gm. Ternstroemia (Theaceae). Plate I, 2a, b. Grain prolate to subspheroidal, amb circular, tricolporate, microreticulate, the sculpturing becoming finer towards the equator. Colpi long with costae colpi. Size: 35-26 x 25-20 ~m. Tillaea (Crassulaceae). Plate I, 3a, b. Grain subspheroidal, amb circular, tricolporate, scabrate. Colpi long and wide, constricted at the equator. Costae colpi present. Size: 22-19 x 21-19 ~m. CaUitriche (Callitrichaceae). Plate I, 4a-c. Grain subspheroidal, inaperturate, reticulate with clavae. Exine >1pro. Size: 28-26 x 27-23 ~m. Bartsia-type (Scrophulariaceae). Plate I, 5a-c. Grain subspheroidal, arab circular, tricolporate, psilate. Dense carpet of fine distinct columellae rendering a very regular scabrate appearance. Colpi thin with ragged edges. Size: 41-31 x 32-26 pm. Lupinus (Papilionaceae). Plate I, 6a, b. Grain prolate, arab circular, tricolporate, reticulate. Colpi long and narrow, slightly

52 constricted at the equator. Pore indistinct. Size: 45-37x30-27 #m. (Hooghiemstra, 1984). t7: Elaeagia-type (Rubiaceae). Plate II, 7a, b. Grain subspheroidal, amb circular, tricolporate, microreticulate. Colpi with a colpus transversalis. Size: 20-19 x 18-17 gm.

Fern-spore types t8:

Azolla (Azollaceae). Plate II, 8a, b. Mas-

sula with spores more or less spheroidal, 180-160 #m in diameter. Glochidia ca. 100 pm long, uncinate. (Hooghiemstra, 1984). t9: Hymenophyllum (Hymenophyllaceae). Plate II, 9a, b. Spore amb circular to subtriangular-convex, trilete, the laesurae extending almost to the equator. Sclerine with echinae. Equatorial diameter: 72-53 gm. (Hooghiemstra, 1984). tl0: Ophioglossum (Ophioglossaceae). Plate II, 10a, b. Spore amb circular, trilete, the laesurae 2/3 to 3/4 of the radius. Sclerine fossulate to foveolate. Equatorial diameter: 72-67 #m (Hooghiemstra, 1984).

Fungal types tll:

t12:

t13:

t14:

t15:

Plate II, 11. Spores (conidia?), 5-8 septate, septa colorless to brown. Size: 190130 x 15-10 ~m. Anthostomella fuegiana Speg. (Ascomycetes). Plate II, 12. Ascospores, inequilateral (one side almost straight), brown, tapering apically into a sharp point; basal end truncate. Size: 23-19 x 7-6 ~m. (Van Geel, 1978). Plate II, 13. Coiled cluster of 8-12 globose fungal cells, cells colorless to brown. Greatest diameter of the cluster: 48-36 pm. Individual cells variable in size. Plate II, 14. Spores ellipsoidal, one-celled, brown, smooth-walled, with a protruding apical pore ca. 1.5ttm wide. Size: 40-35 x 27-18 #m. Gaeurnannomyces cf. caricis J. Walker (Diaporthaceae). Plate II, 15. Hyphopodia irregular in outline, brown, always with blunt lobes and a prominent clear spot of

ca. 2 #m diameter in the central area. Diameter: 26-22 #m. (Hooghiemstra, 1984). t16: Plate III, 16. Spores ellipsoidal, darkbrown to black, smooth-walled, with a truncate end. Size: 50-30 x 30-23 #m. t17: Helicoon pluriseptatum Van Beverwijk (Hyphomycetes). Plate III, 17. Conidia helically coiled forming a biconical spore body, colorless to brown. Diameter: 29-25 gm. (Hooghiemstra, 1984). t18: Plate III, 18a, b. Ascospores, one-septate, constricted at the septum, brown. Size: 60-52 × 34-30 #m, inclusive of the ca. 4 ~m thick, undulating epispore which is attached to the spore wall at irregular intervals.

Algal types t19: Spirogyra cf. scrobiculata (Stockmayer) Czurda (Zygnemataceae). Plate III, 19a, b. Spores, 90-70 #m in diameter. Wall with pits ca. 2 pm in diameter. (Helmens and Kuhry, 1986).

Zoological types t20: Assulina (Rhizopoda). Plate III, 20. Shell brown, densely and regularly ornamented with imbricate silicic plates. Size: 60-55 x 48-43 ttm. (Hooghiemstra, 1984). t21: Callidina (Rotifera). Plate III, 21. Loricae. Size: 180-120 #m long, greatest width 100-85 m, mouth ca. 26-19 tim in diameter. (Van Geel, 1978). t22: Amphitrema (Rhizopoda). Plate III, 22. Shell more or less cylindrical, with a pseudostoma at each end, opposite one another. Size: 55-50 x41-31 ~m. (Hooghiemstra, 1984). Descriptions and illustrations o f the m a c r o f o s s i l types The identification of the macroscopic fossil plant remains found in the EB I and III section was carried out by comparison with the Hugo de Vries Laboratory collection of recent material assembled by the author. This includes all

53 cormophytes and bryophytes that are common in open water, mire and peatbog communities in the high Andean areas of Colombia. The collection contains significant parts of cormophytes, such as branches, leaves, flowers, fruits, seeds, megaspores, stem-, leaf- and rootepidermis, and mosses and liverworts.

Plant remains of cormophytes TI: AzoUa filiculoides Lamarck (Azollaceae). Plate IV, la, b. Plant remains. Stems densely covered with small, overlapping, alternate leaves. Leaves with broad hyaline margins. T2: Cyperaceae. Plate IV, 2a, b. Stem and]or leaf remains. Parallel venation. Epidermis with costal and intercostal zones. Epidermal cells arranged in longitudinal rows parallel to the long axis of the stem and]or leaf. Intercostal cells with sinuous walls. T3: Cyperaceae. Plate IV, 3a-c. Basal leaf remains. Leaves variable in size. Parallel venation. T4: Carex sp. (Cyperaceae). Plate IV, 4a, b. Leaf epidermal remains. Intercostal (and costal?) cells with sinuous walls. Stomata arranged at intervals in longitudinal rows of cells lying parallel to the long axis of the leaf. Stomata paracytic, with clear dome-shaped, sometimes almost triangular, subsidiary cells. T5: Tillaea paludosa Schlechtendahl (Crassulaceae). Plate IV, 5a, b. Leaf remains, cylindrical. Epidermal cells elongated in the direction of the longitudinal axis of the leaf. Stomata anisocytic, present on all parts of the leaf surface. T6: Equisetum sp. (Equisetaceae). Plate IV, 6. Rhizome remains, cylindrical. Epidermal cells elongated in the direction of the longitudinal axis of the rhizome. Cell walls sinuous. T7: CaUitriche sp. (Callitrichaceae). Plate IV, 7. Rhizome remains, cylindrical. Epidermal cells large (ca. 250 ~m long), inflated, elongated in the direction of the long axis of the rhizome. Cell walls dark colored.

Plant remains of bryophytes The identification of fossil mosses is generally based on leaf characters, because of the lack of intact plants. Determinations have been checked with collections from the Herbarium of the Utrecht State University, The Netherlands. Nomenclature is principally based on Florschfitz-de Waard and Florschfitz (1979), and Gradstein and Hekking (1979). T8: Drepanocladus aduncus (Hedwig) Warnst. (Amblystegiaceae). Plate V, 8a-g. Plants irregularly branched. Leaves falcate, acuminate, unicostate, the costa ending near the apex. Leaf margin entire. Leaf cells smooth, linear. Distinct group of alar cells. According to Crum and Anderson (1981) the entire leaf margin separates D. aduncus from other related species such as D. fluitans (Hedwig) Warnst. and D. exannulatus (B.S.G.) Warnst. T9: Campylopus sp. (Dicranaceae). Plate V, 9a-c. Plants unbranched. Leaves lanceolate, acuminate, unicostate, the costa percurrent (excurrent?) and broad, more than 113 width of the leaf base. L e a f cells smooth, upper leaf cells short rectangular to rhomboidal. T10: Sphagnum sect. Cuspidata (Sphagnaceae). Plate V, 10a, b. Leaves ovatelanceolate, sometimes slightly falcate, slightly concave, ecostate. Leaves with regular pattern of alternating green and hyaline cells reinforced with spiral fibers. Green cells more exposed on dorsal surface. Pores small, less than 12 ~m. Tll: Bryum spp. (Bryaceae). Plate VI, l l a - f . Plant unbranched. Leaves ovate-lanceolate, acute to shortly acuminate, unicostate, the costa ending near the apex, margin entire. Leaf cells smooth, elongated hexagonal or rhomboidal, distinct border of narrower cells. T12: Brachythecium sp. (Brachytheciaceae). Plate VI, 12a-e. Leaves ovate-lanceolate, longly acuminate, plicate, unicostate, the costa ending above mid-leaf, upper leaf

54 PLATE I la, b. tl. 2a, b. t2. 3a, b. t3. 4a-c. t4. 5a-c. t5. 6a, b. t6.

Abatia pollen, × 1000. Ternstroemia pollen, x 1000. Tillaea pollen, x 1000. Callitriche pollen, x 1000. Bartsia-type pollen, x 1000. Lupinus pollen, × 1000.

PLATE II (see p. 56) 7a, b. t7. Elaeagia.type pollen, × 1000. 8a, b. t8. Azolla massula; (a) massula, x 100; (b) glochidia, x 250. 9a, b. t9. Hymenophyllum spore, × 400. 10a, b. tl0. Ophioglossum spore, × 400. 11. t l l . F u n g a l spore, conidium?, × 400. 12. t12. Anthostomella fuegiana ascospore, x 1000. F u n g a l cells, x 1000. 13. t13. 14. t14. F u n g a l spore, × 1000. 15. t15. Gaeumannomyces cf. caricis hyphopodium, x 1000.

P L A T E III (see p. 57) 16. t16. F u n g a l spore, x 1000. Helicoon pluriseptatum conidium, × 1000. 17. t17. 18a, b. t18. Aseospore, × 1000. 19a, b. t19. Spirogyra cf. scrobiculata spore, × 500. 20. t20. Assulina shell, × 500. Callidina lorica, x 500. 21. t21. Amphitrema shell, × 500. 22. t22.

PLATE IV (see p. 58) la, b. T1. Azolla filiculoides remains; (a) plant, x 10; (b) leaf, x 25. Cyperaceae stem and/or leaf remains; (a) epidermis, x 100; (b) epidermis, x 250. 2a, b. T2. 3a c. T3. Cyperaceae basal leaf remains; (a) basal leaf, × 10; (b) parallel venation, × 100; (c) epidermis, × 250. 4a, b. T4. Carex sp. epidermal remains; (a) epidermis, x 100; (b) epidermis, × 400. Tillaea paludosa leaf remains; (a) epidermis, x 100; (b) epidermis, x 400. 5a, b. T5. Equisetum sp. rhizome remains; (a) epidermis, × 100; (b) epidermis, × 250. 6a, b. T6. 7. T7. Callitriche sp. rhizome remains; epidermis, × 100.

PLATE V (see p. 59) 8a-g. T8. Drepanocladusaduncus remains; (a) plant, × 10; (b-d) leaves, x 10; (e) leaf margin, × 250; (f) leaf cells, × 250; (g) group of alar cells (partly decayed), x 250. 9a-c. T9. Campylopussp. remains; (a) plant, x 10; (b) leaf, × 10; (c) upper leaf cells, × 250. 10a, b. T10. Sphagnum sect. Cuspidata remains; (a) leaf, x 40; (b) leaf cells, × 250.

PLATE V! (see p. 60) l l a f. T l l . Bryum spp. remains; (a, b) plants, × 10; (c, d) leaves, x 10; (e) leaf margin, x 250; (f) leaf cells, x 400. 12a-e. T12. Brachythecium sp. remains; (a) leaf, x 40; (b) leaf, × 10; (c) leaf margin, × 250; (d) leaf cells, × 250; (e) group of alar cells (partly decayed), x 250. 13a-d. T13. Leptodontium longicaule remains; (a) leaf, x 10; (b) upper leaf margin, x 400; (c) upper leaf cells, x 400; (d) lower leaf cells, x 400.

iml

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56

PLATE II

(for explanation see p. 54)

o

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1 D <

D T

58 PLATE

IV

i

(for explanation see p. 54)

59

PLATE V l

0 I i:!

m

(for explanation see p. 54)

60

PLATE VI

(for e x p l a n a t i o n see p. 54)

61

T13:

T14:

T15:

T16:

T17:

margin denticulate. Leaf cells smooth, linear. Distinct group of alar cells. Leptodontium longicaule Mitt. (Pottiaceae). Plate VI, 13a-d. Leaves lanceolate, vaginate, unicostate, the costa e~ding near (in?) the apex, upper leaf margin dentate. Upper leaf cells rounded with papillae restricted to a high central prominence, basal leaf cells smooth, elongated. Calliergon cf. sarmentosum (Wahlenberg) Kindb. (Amblystegiaceae). Plate VII, 14a-c. Leaves ovate, slightly concave, faintly plicate, unicostate, the costa ending above mid-leaf. Leaf cells smooth, linear. Distinct group of alar cells. C. sarmentosum is the only nerved Calliergon species recorded from Colombia (G. van Reenen, pers. comm., 1985). Lepidopilum cf. muelleri (Hamp.) Spruc. (Daltoniaceae). Plate VII, 15a, b. Leaves ovate-lanceolate, longly acuminate, bicostate, the costa ending near mid-leaf, not bordered. Leaf cells smooth, linear. L. muelleri is the only Lepidopilum species that occurs in the high-Andean vegetation belt of the Colombian Cordillera Central (G. van Reenen, pers. comm., 1985). Pleurozium schreberi (Brid.) Mitt. (Entodontaceae). Plate VII, 16a-f. Plants branched. Leaves ovate, concave, costa bifurcate and confined to lower half of leaf, leaf apex notched. Leaf cells smooth, linear. Distinct group of alar cells. Especially, the notched apex is a differential character that separates P. schreberi from other similar mosses, such as Calliergon cuspidatum (Hedw.) Kindb. (Crum and Anderson, 1981). Rhynchostegiella compacta (Hooker.) Loesk. (Brachytheciaceae). Plate VIII, 17a-d. Plants branched according to literature, but not seen. Leaves ovatelanceolate, longly acuminate, unicostate, the costa ending near apex, margin serrulate. Leaf cells smooth, linear. This is the first record of R. compacta in South America. The marshy habitat dif-

T18:

T19:

T20: T21:

fers from the records of R. compacta in Central and North America. Nevertheless, the plant agrees with the description in Crum and Anderson (1981). The only difference seems to be the slightly longer apex and longer acumen cells in the fossil moss recorded in the present study. Sphagnum magellanicum Brid. (Sphagnaceae). Plate VIII, 18a-c. Plants branching in fascicles. Cortical cells of stem and branches fibrillose. Leaves broadly ovate, deeply concave, hood-shaped, ecostate. Leaves with a regular pattern of alternating green and hyaline cells reinforced with spiral fibres. Green cells completely enclosed on both surfaces of leaf. Breutelia chrysea (C. Mueller) Jaeg. (Bartramiaceae). Plate VIII, 19a-f. Leaves ovate-lanceolate, acuminate, plicate at base, unicostate, the costa ending near the apex, leaf margin serrulate. Leaf cells with papillae projecting from the posterior end of leaf cell wall, narrowly rectangular. Upper leaf cells mostly five times as long as wide. Basal leaf margin with many rows of enlarged cells extended along leaf margin, sometimes up to the widest part of the leaf. Determination following the key of Robinson (1967). Marchantia sp. (Marchantiaceae). Plate IX, 20a, b. Thallus remains with pores. Plate IX, 21a-c. Undetermined remains. Undifferentiated cells, unicellular rhizoids. Thallus of Hepaticae?

Fruits and Seeds Descriptions are based on morphological characters. Terminology is mainly taken from Montgomery (1977) and Berggren (1969, 1981). Abbreviations: 1.s. = longitudinal-section; c.s. = cross-section. T22: Eleocharis acicularis (L.) Roemer et Schultes (Cyperaceae). Plate IX, 22. Achenes elliptic to obovate in 1.s., triangular-convex, occasionally quadrangularconvex, to almost circular in c.s. Size: ca. 1.0 x 0.4 × 0.4 mm. Wall surface with 3-4

62

T23:

T24:

T25:

T26:

T27:

T28:

T29:

T30:

ridges on e a c h side with t r a n s v e r s e striations. Style-base and bristles not found. Bidens sp. (Compositae). P l a t e IX, 23. A c h e n e s o b o v a t e in 1.s. flattened, oblong in c.s. t e n d i n g to be c o n c a v e - c o n v e x or piano-convex. Size: ca. 1.8 x 1.1 x 0.2 mm. Pappus of 2 awns. Carex sp. 3 (Cyperaceae). P l a t e IX, 24. A c h e n e s o v a t e to elliptic in 1.s., triangular slightly c o n v e x in c.s. Size: ca. 1.7 x 0.8 x 0.7 mm. Wall surface areolate. P e r i g y n i a not found. Carex pichinchensis H u m b o l d t B.K., C. acutata B o o t t and C.jamesonii B o o t t are Colombian Carex species with triangular achenes. T h e y all p r e d o m i n a n t l y or exclusively o c c u r in mire v e g e t a t i o n types. Hydrocotyle ranunculoides L.f. (Umbelliferae). Plate IX, 25. T h e fruit is a dry schizocarp t h a t splits into two one-seeded mericarps. M e r i c a r p s semi-elliptic in 1.s., flattened, oblong in c.s. Size: ca. 1.7 x 1.2 x 0.5 mm. Cardamine bonariensis J u s s i e u et Persoon (Cruciferae). P l a t e X, 26. Seeds campylotropic, elliptic in 1.s., flattened slightly biconvex, elliptic in c.s. Size: ca. 1.2 x 1.0 x 0.4 mm. M a r g i n with a n o t c h between the tip of the radicle and t h a t of the cotyledons. Wall surface finely reticulate. Carex cf. bonplandii K u n t h (Cyperaceae). P l a t e X, 27a, b. A c h e n e s elliptic to o v a t e in 1.s., flattened biconvex, elliptic in c.s. Size: ca. 1.4 x 0.8 x 0.4 mm. Wall surface striate with an o v e r l y i n g a r e o l a t e pattern. P e r i g y n i a not found. Hypericum sp. (Hypericaceae). P l a t e X, 28. Seeds oblong in 1.s., elliptic in c.s. Size: ca. 0.8 x 0.2 x 0.2 mm. Lachemilta sp. (Rosaceae). P l a t e X, 29. Achenes? o b o v a t e in 1.s., elliptic in c.s. Size: ca. 0.8 x 0.5 x 0.3 mm. Callitriche sp. (Callitrichaceae). P l a t e X, 30a, b. F r u i t s splitting into four oneseeded nutlets. Nutlets semi-circular in 1.s., flattened slightly biconvex, elliptic in

T31:

T32:

T33:

T34:

c.s. Size: ca. 1.0 x 0.5 x 0.3 mm. Wall surface areolate. Ericaceae. P l a t e X, 31a, b. Seeds o b o v a t e in 1.s., flattened slightly biconvex, elliptic in c.s. Size: ca. 0.7 x0.5 x0.2 mm. Wall surface r e t i c u l a t e with m a n y small pits. Montia meridense F r i e d r i c h (Portulacaceae). P l a t e X, 32a, b. Seeds campylotropic, c i r c u l a r in 1.s., o b o v a t e in c.s. Size: ca. 1.0 x 1.0 x 0.6 mm. Tip of the radicle projected forming a m a r g i n a l n o t c h b e t w e e n itself and the tip of the cotyledons. Wall surface colliculate. Rumex sp. (Polygonaceae). P l a t e XI, 33. A c h e n e s elliptic in 1.s., triangular-concave in c.s. Size: ca. 2.5x 1.2x 1.2 mm. A c h e n e s sometimes found with the persist e n t calyx. Carex sp. 2 (Cyperaceae). P l a t e XI, 34a, b. A c h e n e s o v a t e in 1.s., flattened biconvex, elliptic in c.s. Size: ca. 1.4 x 0.7 × 0.4 mm. Wall surface striate with an o v e r l y i n g a r e o l a t e pattern. P e r i g y n i a not found. This seed type is p r o b a b l y a s o m e w h a t a n o m a l o u s form of type T27 seeds (Carex

cf. bonplandii). T35: Colobanthus quitensis (H.B.K.) Bartl. (Caryophyllaceae). P l a t e XI, 35a, b. Seeds campylotropic, elliptic in 1.s., slightly reniform, flattened, oblong in c.s. Size: ca. 0.6 x 0.5 x 0.2 mm. Tip of the radicle incurved, a b o u t as long as t h a t of the cotyledons. Wall surface with "puzzlepiece" like cells. T36: Cerastium sp. (Caryophyllaceae). P l a t e XI, 36a, b. Seeds campylotropic, o b o v a t e in 1.s., o b o v a t e in c.s. with s o m e w h a t c o n c a v e faces. Size: ca. 0.9 x 0.6 x 0.5 mm. Tip of the radicle not extended, equal in l e n g t h to t h a t of the cotyledons. Wall surface with elliptic papillae. T37: O t h e r seeds.

Other macrobotanical remains T38: AzoUa filiculoides L a m a r c k (Azollaceae), megaspores. Plate XI, 38a, b. M e g a s p o r e s with pitted wall, sometimes found with

63 P L A T E VII (see p. 64) 14a-c. T14. Calliergon cf. sarmentosum remains; (a) leaf, x 40; (b) leaf cells, x 250; (c) group of alar cells, x 250. 15a, b. T15. Lepidopilurn cf. rnueUeri remains; (a) leaf, x 40; (b) costae and leaf cells, × 250. 16a-f. T16. Pleurozium schreberi remains; (a, b) plants, x 10; (c) leaf, x 40; (d) leaf cells, x 400; (e) leaf apex, x 400; (f) group of alar cells (partly decayed), x 400.

P L A T E VIII (see p. 65) 17a-d. T17. Rhynchostegiella compacta remains; (a) plant, x 10; (b) leaf, x 100; (c) leaf m a r g i n and leaf cells, x 250; (d) leaf apex a n d a c u m e n cells, x 250. 18a-c. T18. Sphagnum rnageUanicum remains; (a) leaf, x 40; (b) leaf cells, x 250; (c) cortical cells, with fibrils, x 100. 19a-f. T19. Breutelia chrysea remains; (a-c) leaves, x 10; (d) leaf cells, x 250; (e) a c u m e n cells, × 250; (f) basal m a r g i n a l cells, x 100.

P L A T E IX (see p. 66) 20a, b. T20. Marchantia sp. remains; (a) thallus cells, x 100; (b) pore, x 400. 21a-c. T21. U n d e t e r m i n e d remains; (a) thallus? with rhizoids, x 40; (b) thallus? cells, x 100; (c) rhizoids, x 100. 22. T22. Eleocharis acicularis achene, x 50. 23. T23. Bidens sp. achene, x 25. 24. T24. Carex sp. 3 achene, x 30. 25. T25. Hydrocotyle ranunculoides mericarp, x 30.

P L A T E X (see p. 67) 26. T26. Cardamine bonariensis seed, x 50. 27a, b. T27. Carex cf. bonplandii achene; (a) achene, x 45; (b) wall surface, × 500. 28. T28. Hypericum sp. seed, x 50. 29. T29. Lachemilla sp. achene?, x 50. 30a, b. T30. Callitriche sp. nutlet; (a) nutlet, x 50; (b) wall surface, × 500. 31a, b. T31. E r i c a c e a e seed: (a) seed, x 50; (b) wall surface, x 500. 32a, b. T32. Montia meridense seed; (a) seed, x 50; (b) wall surface, × 500.

P L A T E XI (see p. 68) 33. T33. Rumex sp. achene, x 25. 34a, b. T34. Carex sp. 2 achene; (a) achene, x 50; (b) wall surface, × 500. 35a, b. T35. Colobanthus quitensis seed; (a) seed, x 50; (b) wall surface, × 500. 36a, b. T36. Cerastium sp. seed; (a) seed, x 50; (b) wall surface, x 500. 38a, b. T38. Azolla filiculoides megaspore; (a) megaspore, x 100; (b) m e g a s p o r e (with massulae attached), x 100.

P L A T E XII (see p. 69) 39. T39. Branches, x 10. 40. T40. Disterigma empetrifolium fruit, x 25. 41a, b. T41. E r i c a c e a e flower; (a) a n t h e r with pollen, x 100; (b) pollen, x 250. 42a, b. T42. Disterigma empetrifolium leaves, x 10. 43a, b. T43. Leaves, x 10. 44. T44. E r i c a c e a e branches, x 10.

PLATE XIII (see p. 70) 45. T45. Operculum, x 40. 46. T46. Operculum, x 40. 47. T47. Sphagnum sp. operculum, x 40. 48. T48. Peristome, x 40. 49. T49. Copepoda (Cyclopoidae), x 10. 50a, b. T50. Acaridae, x 40. 51. T51. Cocoons of Olig0chaeta?, × 10. 52. T52. P u p a r i a of Insecta?, x 40.

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PLATE VIII

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71

massulae attached. Size (exclusive of the massulae): ca. 0.5 x 0.2 ram. T39: Branches. Plate XII, 39. Branches with decussate leaf arrangement, circular in C.S.

T40:

T41:

T42:

T43:

T44:

T45: T46: T47:

T48:

This branch type is among others found in Hypericum species. Disterigma empetrifolium (H.B.K.) Drude (Ericaceae), fruits. Plate XII, 40. Fruit a berry; persistent calyx of four sepals that are fused at the base, two bracts; ovary inferior, style simple. Ericaceae, flowers. Plate XII, 41a, b. Flowers with anthers carrying Ericaceae pollen. Disterigma empetrifolium (H.B.K.) Drude, leaves. Plate XII, 42a, b. Leaves simple, lanceolate, obscurely serrulate; venation pinnate, petiole short. Size: ca. 0.7 × 0.2 mm. Leaves. Plate XII, 43a, b. Leaves simple, lanceolate, margin entire or obscurely serrulate; venation pinnate, petiole absent. Size: ca. 0.2 x 0.1 mm. This type of small leaves is among others found on Disterigma empetrifolium stems. Ericaceae, branches. Plate XII, 44. Branches with alternate leaf arrangement. Stipules present. Branches circular in c.s. Opercula. Plate XIII, 45. Opercula mammilate, ca. 1 mm in diameter. Opercula. Plate XIII, 46. Opercula rostrate, ca. 0.6 mm in diameter. Sphagnum sp. (Sphagnaceae), opercula. Plate XIII, 47. Opercula convex, ca. 1 mm in diameter. Peristome. Plate XIII, 48. Peristome with teeth, ca. 0.8 mm in diameter.

Some zoological remains T49: T50: T51: T52:

Copepoda (Cyclopoidae). Plate XIII, 49. Acaridae. Plate XIII, 50a, b. Cocoons of Oligochaeta? Plate XIII, 51. Puparia of Insecta? Plate XIII, 52.

Acknowledgements I wish to thank Dr. J.B. Salomons and Dr. J.C. Thouret (Grenoble, France) for their assistance in collecting the EB I section (1979), and Dr. A.B.M. Melief and Prof. T. van der Hammen for the collection of the E B I I I section (1981). I am very indebted to the following persons: Dr. D. Griffin III (Gainesville, U.S.A.) and Mr. G. van Reenen (Utrecht, The Netherlands) for their help in the general identification of the mosses; Dr. H.A. Crum (Michigan, U.S.A.) for the determination of Rhynchostegiella compacta; Dr. R. Zander (Buffalo, U.S.A.) for checking the determination of Leptodontium longicaule; Dr. H. Ochi (Tottori, Japan) for the determination of Bryum; Dr. H.P. Frahm (Duisburg, W. Germany) for checking the determination of Campylopus; Dr. H. Bischler (Paris, France) for the identification of Marchantia; Dr. L.E. Constance (Berkeley, U.S.A.) for sending me recent seeds of Hydrocotyle ranunculoides; and, Prof. W.G. Mook (Groningen, The Netherlands) for providing the radiocarbon dates. Finally, I wish to express my thanks to Prof. T. van der Hammen for the critical revision of the text, Prof. A.D.J. Meeuse for the correction of the English text, Mrs. E. Beglinger for her assistance in taking the scanning electron micrographs of the fruits and seeds, and Dr. K.F. Helmens for drawing the figures. This study was carried out with the financial support of the Netherlands Foundation for Advancement of Tropical Research (WOTRO).

References Bartram, E., 1949. Mosses of Guatemala. Fieldiana, 25: 1-442. Berggren, G., 1969. Atlas of Seeds, Part 2: Cyperaeeae. Swed. Nat. Sei. Res. Counc., Stockholm, 68 pp. Berggren, G., 1981. Atlas of Seeds, P a r t 3 : SalicaceaeCruciferae. Swed. Nat. Sci. Res. Counc., Stockholm, 261 pp. Cleef, A.M., Rangel, Ch., O. and Salamanca, V., S., 1983. Reconocimiento de la vegetaci6n en la parte alta del Transecto Parque Los Nevados. In: T. van der Hammen, A. Perez P., and P. Pinto E. (Editors), Studies on Tropical Andean Ecosystems, Vol.I. La Cordillera Cen-

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