Trees (2005) 19: 661–670DOI 10.1007/s00468-005-0430-7

ORIGINAL ARTICLE

F. Abdoun · A. J. T. Jull · F. Guibal · M. Thinon

Radial growth of the Sahara’s oldest trees : Cupressus duprezianaA. Camus

Received: 15 April 2004 / Accepted: 7 April 2005 / Published online: 27 April 2005C© Springer-Verlag 2005

Abstract The radial growth of Duprez’ cypress (Cupres-sus dupreziana A. Camus), a tree endemic to the Tassilin’Ajjer in the Central Sahara, was measured from corestaken in 1967 and 1997 from the same trees. A compari-son of these cores, spanning 30 years, reveals that even inthis hyper-arid climate, this species has a juvenile vigourcomparable to other Mediterranean Cupressaceae. Wideindividual variability was found, however, which was in-duced by the strong influence of microhabitat factors. Tra-ditional dendrochronological methods of cross-dating areimpossible to apply in the case of these trees. Ages of eightindividuals were estimated with the help of radiocarbondating, yielding an age range from 600 to 2400 years fortrees of the most usual girths.

Keywords Cupressus dupreziana, Radial growth . Treeages . Tassili n’Ajjer . Sahara

This work is dedicated to the memory of Francoise Serre.

F. Abdoun (�)UMR EcoBio 6553, Universite Rennes-1,Bat 14-A Campus Beaulieu,35042 Rennes Cedex, Francee-mail: fatabdoun@yahoo.frTel.: 33-(0)-2-35-14-66-56Fax: 33-(0)-2-35-14-66-55

A. J. T. JullNSF Arizona AMS Laboratory, The University of Arizona,Physics Building,1118 East Fourth,St. Tucson, AZ 85721, USA

F. GuibalInstitut Mediterraneen d’Ecologie et de Paleoecologie, CNRSUMR 6116, Europole Mediterraneen de l’Arbois,Pavillon Villemin,BP, 8013545 Aix-en-Provence Cedex 04, France

F. Abdoun · M. ThinonInstitut Mediterraneen d’Ecologie et de Paleoecologie, CNRSUMR 6116,case 462,13397 Marseille cedex 20, France

Introduction

The very presence of Duprez’ cypress (Cupressusdupreziana A. Camus) in the hyper-arid climate of theCentral Sahara constitutes a considerable botanic curios-ity. First encountered by scientists in 1924 (Maire 1933),the species only exists in the wild in the Tassili n’Ajjerin south-eastern Algeria. Initial observations made in the1920s led to the view that the handful of elderly trees foundwere the remains of a forest that had grown in an earlier,wetter climate (Lavauden 1926). Based on this view, onewould conclude today’s infrequent and irregular rainfallshould not allow these seedlings to develop. Some authors(Lavauden 1926; Barry et al. 1970) considered that the sur-vival of these trees was due to a powerful root system draw-ing water from underground aquifers. It also appeared thatthese trees would eventually die of old age without repro-ducing and germinations would not survive the drought,whereupon the species would inevitably become extinct(Barry et al. 1970). Duprez’ cypress was accordingly clas-sified by the IUCN (International Union for Conservationof Nature) as among the 12 most endangered species in theworld (Lucas and Synge 1978).

Of the first trees observed, ten of them have impressivetrunks of up to 12 m in girth, giving credibility to the hy-pothesis of a “forest relic” condemned to disappear by thedrying of the climate (Barry et al. 1970; Lucas and Synge1978; Stewart 1969). For these trees, ages of many thou-sands of years had been proposed, which would go backto times when the area was occupied by Bovidian pas-toralists who painted many of the famous cave frescoesnearby (Lhote 1958). Knapp (1973) suggested an age of4700 years, referring to Meyer (1961/1962) and his sum-mary paper on the world’s oldest trees. The latter authorin turn refers to Simonneau and Debazac (1961) who useQuezel’s scenario in which the Sahara started drying outaround 2800 bc (Quezel 1960). That date matches the ageof ancient organic traces (Rock Hyrax droppings) contain-ing a rich pollen load and radiocarbon-dated to 4680±300years bp (Pons and Quezel 1958). As early as the 1950s,

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Capot-Rey (1954) and Balachowsky (1955) reported theexistence of young trees which they said could not be morethan 200 years old, however, the few studies that have beenwritten on the species have taken only the older, palyno-logical interpretations into account.

A dendrochronological approach was attempted in 1967by F. Serre (University of Aix-Marseille III, France). Anal-ysis of the cypresses’ growth rings very quickly showedthat radial growth was irregular and cross-dating difficult,hence she concluded that Duprez’ cypress does not lend it-self to the usual methods of dendrochronology (Dobry andKyncl 1989, 1992). The only objective information avail-able on the age of these trees was a 14C date (1640±80 bp,referred Bern-2523) obtained from a sample taken from thecentre of a dead stump 1.40 m in diameter (Messerli andKienholz 1981).

The present population of Duprez’ cypress, enumeratedbetween 1997 and 2001, includes 233 living trees over anarea of some 1000 km2 along the south-western edge of theplateau of the Tassili massif in Algeria, between 1430 mand 1830 m above sea level and between 25◦5′ N, 9◦1′ Eand 24◦19′ N, 9◦50′ E (Abdoun and Beddiaf 2002) (Fig. 1).The population is found in groups or as isolated trees, infissures in the Palaeozoic sandstone and in a great variety oftopographical situations, from mountain tops to the bottomsof valleys and canyons. The shapes of the trees can varyconsiderably, and seems to be due in great part to humandamage (wood-gathering, grazing). The conical or fasti-giate shape formed by natural growth accounts for 19% ofthe total population (Abdoun 2002). The trees vary in heightfrom 3 m up to 22 m, and in girth from 0.32 m to 12 m, witha continuous distribution between these extremes, whichhints at continuous regeneration over at least the last 2000years (Abdoun and Beddiaf 2002). The discovery of twoyoung trees, 0.32 m and 0.37 m in girth, resulting from ger-minations which took place during the second half of thelast century (Abdoun and Beddiaf 2002), reveals that the

species has a capacity for regeneration in situ and is adaptedto the Sahara’s present climate (Abdoun and Beddiaf 2002).It seems important, therefore, to look into the radial growthpatterns of these trees over time in these extremely dryconditions.

The climate of the Tassili is still not well known(Dubief 1999). Extrapolations on the basis of records fromthe Djanet weather station (located some 20 km from thesouth western edge of the Tassili plateau, in a lower-lyingplain at an altitude of 1054 m) give an annual mean pre-cipitation of about 30 mm, with great variations from yearto year (Dubief 1963). The annual mean temperature is es-timated to be 18.5◦C at 1600 m altitude and the mean ofminimum temperatures in the coldest month (February) at3◦C (Abdoun 2002).

The objective of this study is to document the radialgrowth patterns of this population by comparing samplingcores taken in 1967 and 1997 from the same trees, and tospecify the age of the cypresses by a twin approach usingboth growth rings and radiocarbon dating.

Materials and methods

Samples

In January and December1967, on the initiative of the den-drochronologist F. Serre, two expeditions to the Tassili re-gion gathered 123 cores representative of 37 trees.

In March-April 1997, thirty trees were re-sampled, ata few centimetres’ distance from the earlier holes whichcould sometimes still be seen on the trunks. 1 to 5 coreswere taken from each tree (Table 1). Cores were not takenagain from fused (anastomosed) stems, nor from trees thathad died since 1967. It was possible to locate the sitesof the earlier samplings thanks to the unpublished notes(from a travel diary) of the samplers (J.L. Borel and Salisse

Fig. 1 Map of the study region

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Table 1 Sites, numbers of trees and geographical locations of thevarious trees cored in 1967 and 1997

Station 1967 1997 Latitude N Longitude E

Adhar n’Taclit 1 1 24 24 469 9 51 063Adjedjoum 2 1 24 36 839 9 42 494Ahahedjrine 1 1 24 29 081 9 47 607Amassadjou 1 1 24 29 337 9 43 653Amazar 7 1 24 24 605 9 50 745Ibendaradj 1 1 24 27 474 9 49 267Ihahaneha-djroutnine

2 1 24 29 605 9 48 096

Imalaoulitene 4 2 24 28 958 9 49 056In-ghaldjiwene 1 1 24 23 439 9 51 252In-gharohane 1 3 24 27 830 9 47 121Tabarakat 1 1 24 29 441 9 45 362Tamghit 10 12 24 37 228 9 38 920Tibdjoudjine 2 1 24 26 895 9 49 067Tichouinet 2 2 24 29 278 9 49 229Tin-damaıne 1 1 24 29 283 9 45 093Total 37 30

unpublished data), and the guidance given by Aıssa AgDjebrin Machar, who had acted as guide to the Borel mis-sion. Some of the authors met him at Djanet in March 1997(Aıssa Ag Djebrin Machar, personal comm.).

Technical preparation

The cores were prepared by gluing them to calibrated rodsand sanded according to current dendrochronological meth-ods (Schweinguber 1988).

We visually examined over 200 cores under a binocularmagnifier and eliminated complex cases in which it provedimpossible to match cores across the 1967–1997 time inter-val. By the end of the selection process 17 trees remained,which had grown on various substrates and with girthsranging from 0.8 m to 6.95 m. These trees had been iden-tified by a number painted on their trunks by Grim (1992unpublished data) at the time of his 1971–1972 inventory;these numbers are given in Table 2.

Determining the radial growth made between 1967and 1997

We examined the 1967 and 1997 cores superposed un-der an optical microscope, and the 1967 core boundarieswere cross-correlated with the 1997 cores. We made a slidefrom the 1967 core, which was placed in front of the 1997core, so that the two growth ring series could be comparedand adjusted. The growth rings formed between 1967 and1997 were counted on the 1997 cores using the last ringpresent in 1967 as the starting-point, though it should beunderstood that ring is not necessarily laid down in 1967.This uncertainty particularly affects the wider trees, wherethe functioning of the cambium seems most irregular, with

many cases of missing or discontinuous rings. Taking intoaccount that the term “ring” as a unit of time (one ring =1 year) was liable to be inappropriate in this case, we shallbe using it to denote an anatomical unit, the expression of aradial growth event that might or might not take place eachyear.

Since the comparison of many cores side by side underthe stereoscopic microscope was hampered by high mag-nification, we opted for an X50 epidiascope with digitalimage recording by means of a video camera connectedto a computer. A combined image was reconstructed usingPhotoshop image-processing software (version 7.0, AdobeSystems Inc., 1999–2002).

Mean annual growth was calculated on the basis of theincrease in the radius over the 30 years from 1967 to 1997.Under the optical microscope, we were able to recognizethe last ring of a core taken in 1967 on a newer core collectedin 1997. Then, we measured the length of the core betweenthis limit and the ring formed in 1997. This width is whatwe call the “radial growth” of the tree between 1967 and1997. Differences in the number of rings formed during thisperiod were studied in relation to tree girth, two classes ofgirth being definedfor this purpose:

1. under 2.5 m, single trunk (young trees),2. over 3 m (old trees, including trees branching below the

coring site).

Similar ring-width patterns between different cores fromthe same tree were sought first, and then those amongdifferent trees growing in the same site conditions. Thecomparison was made using the reconstituted images ofcores.

Age of the trees from cross-dating of ring sequences

A sub-sample of the eight largest-diameter trees was se-lected for determining their age by taking the longest coreof each tree (though the length of the coring tools, no morethan 0.4 m, did not enable us to reach their pith). Ringwidths were measured to within 1/100 mm with an Eklunddevice linked to a computer for direct recording of thesemeasurements.

Age of the trees using radiocarbon dating

Radiocarbon level measurements were made for the sameeight trees. Two samples were taken from each core, thefirst at the innermost (oldest) end, the position of thesecond varied from core to core depending on the trendof their growth graph, according to an inflection of thegrowth curve, that is, a point of decrease of the treegrowth.

The raw dates (Table 3) were first calibrated using OxCal(OxCal Program v3.5 (c) Copyright Christopher BronkRamsey 2000) and the number of intervening years wasthen calculated from the calibrated ages to within 1σ withan adequate relative probability of 98% to 115%. This

664

Tabl

e2

Gen

eral

cond

ition

ofth

etr

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stud

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No.

tree

Plac

ekn

own

asR

elie

fSu

bstr

ate

Tem

pora

ryw

ater

pond

Ram

ifica

tion

noL

evel

(m)

Hei

ght

(m)

Cir.

(m)

Len

gth

ofth

eex

pose

dro

ots

(m)

Los

sof

bark

Cut

ting

Folia

geG

ener

alSt

ate

Form

2Ta

mgh

itR

iver

bed

Roc

ky-s

andy

Und

erth

etr

ee2

2.5

121.

9N

ull

Nul

l3

12

Con

e-sh

aped

7Ta

mgh

itR

iver

bed

Dee

psa

ndU

nder

the

tree

3A

tthe

base

101.

2-2-

1.6

Nul

lN

ull

31

2Sp

heri

cal

8Ta

mgh

itR

iver

bed

Ston

ysa

ndN

ear

ther

tree

notv

ery

impo

rtan

t

11

12.5

3.3

150

%3

33

Sphe

rica

l

9Ta

mgh

itR

iver

bed

Roc

kN

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101.

02N

ull

Nul

l3

22

Con

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10Ta

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212

3.6

150

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44

Def

omed

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utila

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mgh

itR

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bed

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ky-s

andy

No

32

135.

52

20%

22

3Ir

regu

lar

form

13Ta

mgh

itR

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bed

Dee

psa

ndU

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the

tree

31

152.

17N

ull

Nul

l1

11

Con

e-sh

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16Ta

mgh

itR

iver

bed

Roc

ky-s

andy

No

12

153.

782

10%

31

2C

one-

shap

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8T

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No

31.

58

3.14

20%

31

3Sp

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cal

179

Am

assa

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dSa

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No

30.

515

4.95

5N

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21

3Py

ram

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29T

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tR

iver

bed

Sand

yN

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110

4.3

2015

%3

13

Sphe

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Tic

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net

Riv

erbe

dSa

ndy

No

>7

218

6.95

150

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33

Sphe

rica

l90

Imal

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dSa

ndy-

ston

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0.6

124

Nul

l10

%3

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mid

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hane

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dR

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-san

dyN

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315

3.95

530

%2

43

Pyra

mid

al66

Adh

arn’

Tacl

itR

iver

side

Sand

y-st

ones

No

010

1.58

Nul

lN

ull

21

2C

one-

shap

ed17

Ihah

aneh

a-dj

rout

nine

Riv

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dR

ock

No

011

0.8

Nul

lN

ull

21

2C

one-

shap

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97In

-gha

roha

neR

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ocky

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dyN

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2.22

210

%3

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Cut

ting

–4:

very

freq

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requ

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2:no

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nt,1

:inf

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carc

e,2:

fair

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entif

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ener

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–4:

deca

ying

,3:

stab

le,2

:goo

d,1:

very

good

665

Table 3 Dating measurements

No.Tree

SampleID

LAB 14C age (bp) Cal. age range (1 s)

8 S1 T14743A 1,314±44 680–775 ad8 S2 T14744A 1,202±44 770–865 ad10 S1 T14745A 674±53 1273–1321 ad10 S2 T14746A 413±42 1458–1506 ad11 S1 T14747A 1,208±46 760–880 ad11 S2 T14748A 1,006±40 1000–1120 ad16 S1 T14749A 1,081±52 910–1000 ad16 S2 T14750A 856±40 1155–1245 ad32 S1 T14735A 1,153±40 880–929 ad32 S2 T14736A 1,032±42 980–1029 ad50 S1 T14737A 1,713±39 255–340 ad50 S2 T14738A 1,682±44 335–420 ad178 S1 T14739A 923±41 1510–1660 ad178 S2 T14740A 656±40 1670–1820 ad179 S1 T14741A 282±37 1035–1115 ad179 S2 T14742B 183±41 1310–1390 ad

LAB.: laboratory code, 14C age (bp): radiocarbon age, Cal.age range(1 s): calibrated radiocarbon age with 1 sigma confidence range

calculation is carried out by the method of “Wiggle-matching”, taking the best fit to the two radiocarbon datapoints and using a variable number of intervening years inthe OxCal program.

The growth rate of the juvenile phase of these trees wasestimated from the difference between the calibrated 14Cdates, when taken with the radial distance between the twosamples. The dates themselves only refer to the ages ofthe cored portions of the trees, since the cores from whichthe dated samples came did not extend to the pith, so wecannot establish the initial age, at which the tree began togrow.

Results and discussion

Radial growth between 1967 and 1997

The cumulative radial growth over 30 years varies from10 mm to 73 mm for the young trees, and from 2 mmto 8 mm for the older ones (Fig. 2). Mean annual growthvalues range from 0.38 to 2.23 mm/year in the former case,and from 0.07 to 0.27 mm/yr in the latter.

Tree no. 13 now has a girth of 2.17 m and has recorded amean radial growth of 67 mm in the 30 year period, whiletwo other trees of comparable size (nos. 7 and 97) havemanaged only 12 mm and 11 mm respectively. Tree no 17,which looks younger, has recorded only 12 mm over thesame period, a rate of growth 2.5 times lower than that ofTree no.13.

These measurements show a very considerable individualvariability, probably indicating that microhabitat factorshave a strong influence on the growth rhythms of thesetrees. Tree no. 13 appears to have optimal microhabitat

0

10

20

30

40

50

60

70

80

0 1 2 3 4 5 6 7 8

Circumference (m)

Rad

ial g

row

th (

mm

)

Young trees

Old trees

Fig. 2 Variation of the radial growth between 1967 and 1997 ac-cording to the circumference of the trees

conditions (Table 2). This tree is growing at over 1700 maltitude, at a location where a temporary pool of waterforms in a completely level section of a wadi (dry streambed). The roots of this tree are also in a layer of sand almost2 m deep, which probably means that it has a water stock todraw on for long periods of time. On the other hand, it doesnot seem to have suffered from disturbances such as pruningand grating, which has only been done to a slight extent.The other trees are subject to less favourable conditions,growing on a slab of sandstone or between rocks, and theyhave been more seriously mutilated by human action, atboth the crown and the roots.

The performance of tree no.13 can therefore be seen asexceptional in terms of the samples considered here; yetthe total number of trees living under similar conditions isnot insignificant. Tree no.13 shows a vigour comparable tothat of the Atlas cypress Cupressus atlantica or Cupressusdupreziana var. atlantica according to Farjon (2005) whosemean annual growth rate is of 1.4 mm for a populationbetween the ages of 67 and 120 years (Alifriqui et al. 1996).This attests the astonishing potential productivity of thisspecies, and a remarkable adaptation to the aridity of theTassili in modern times.

The Atlas cypress, regarded as a close relative of theTassili cypress (Gaussen 1968; Farjon 2005), thrives in theMoroccan High Atlas, where it is endemic in the consid-erably wetter conditions there (400 mm to 500 mm/year).It grows above 1500 m altitude on a lithosol where slopesare between 20% and 40%. Its mean annual growth, as re-ported by Alifriqui et al. (1996), is 0.47 to 0.98 mm/yearfor trees 70 years old, an age which corresponds to the 0.4–0.5 m class of girth (Alifriqui, personal communication).This tree takes 9 to 18 years to grow from 0.025 m to 0.05 min radius (Alifriqui et al. 1996). The Tassili cypresses of ra-dius less than 0.70 m have shown radial growth of 0.023 m,0.028 m or even 0.067 m in 30 years. The figures givenfor the Atlas cypress are means from a sample of 33 trees,i.e. double the sample size of our study; they are providedhere to understand the potential of Duprez’ cypress and itscapacity to make the most of the scanty resources of theTassili.

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Age of the trees

Cross-dating of the ring sequences

From counting of the rings laid down between 1967 and1997, we were unable to assign individual rings to particularcalendar years. The number of rings varied greatly (Fig. 3),and was seldom equal to the number of years in the intervalstudied, since a considerable proportion of rings (7% to13%) was missing from trees in the “young trees” group.On the other hand, tree no. 13 which we have alreadydiscussed, laid down 16 extra rings. In the “old trees” group,where the proportion of rings missing was high (33% to63%), the number of rings was less than 30 in virtuallyevery case, the only exception being tree no. 178, for which38 rings were counted on one core. Tree no. 10, which hassuffered damage to its roots, has laid down 27 rings ina total radial growth of 6 mm on its least damaged side(WNW), while on its SSE side (a branch, damaged by barkloss and/or lopping), no rings were counted. This disparityreflects wedging rings (Kaennel and Schweingruber 1995)due to local failure of cambial activity, which could bedistinctly seen on cross-sections taken from dead portionsof the trees. This type of growth is not unique to the Tassilicypress but characteristic of many species in Cupressaceae(Dobry and Kyncl 1992; Glock and Agerter 1963; Corona1970) as well as species from other families (Pinaceae,Nyctaginaceae) (Cherubini et al. 2003).

In the case of trees nos. 8 and 29, the number of ringslaid down in 30 years is 20 and 11 respectively, and the

0

5

10

15

20

25

30

35

40

45

50

0 1 2 3 4 5 6 7 8

Circumference (m)

Num

ber

of g

row

th r

ing

Young treesOld trees

Fig. 3 Variation of the number of growth rings laid down between1967 and 1997 according to the circumference of the trees

sequences on their various cores are similar, which couldbe an indication that the cypress’ radial growth may beinterrupted for periods which may extend over many years(Figs. 4 and 5). Such interruptions might well correspondto years of unfavourable conditions, although they couldalso obey internal processes.

Radiocarbon estimates of the ages of the trees

Our assessment of the ages of the trees by radiocarbon dat-ing (Table 4) is based on the two assumptions of a singlecentrally-located pith and an initial growth rate (in the un-cored portion of the trunk) equal to the later one, which wehave been able to calculate. This latter assumption seemsreasonable to us, since annual increments are more frequent

Fig. 4 Radial growth between1967 and 1997 for cypressno. 8. 1/67: January 1967, 3/97:March 1997, X: a section ofnarrow rings, +: a wide ring

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Fig. 5 Radial growth between1967 and 1997 of the cypressno. 29. 12/67: December 1967

Table 4 Restatement of radial measurements

No.tree

Cir. (m) R (m) L. core (m) Ro (m) R1 (m) Cir.1 (m) R2 (m) Cir.2 (m) Diff.(years)

S1-S2

(mm)Accr1(mm/y)

Estimatedage (years)

8 3.3 0.525 0.287 0.238 0.251 1.58 0.377 2.37 90 126 1.4 150010 3.6 0.573 0.272 0.301 0.31 1.95 0.441 2.77 185 131 0.71 111011 5.5 0.876 0.286 0.59 0.602 3.78 0.739 4.64 240 137.7 0.57 225016 3.78 0.602 0.268 0.334 0.343 2.16 0.407 2.56 245 64 0.26 235032 6.95 1.106 0.26 0.846 0.852 5.35 0.987 6.2 100 135.3 1.3550 3.95 0.629 0.275 0.354 0.364 2.28 0.419 2.64 80 55.9 0.7 2200178 3.14 0.5 0.253 0.247 0.253 1.59 0.381 2.4 275 128 0.47 1260179 3.74 0.595 0.308 0.287 0.298 1.87 0.458 2.88 160 160.3 1 650

In this table are summarized the variables from which our suggested interpretations are derived. Considering the circumference (Cir.)measured tree, one deduces its radius (R), by supposing that the pith of the tree is centered. L core.: is the length of core, Ro: is the distanceseparating the inner extremity of core from pith, R1, Cir1: are the radius and the circumference of tree, respectively, at the level of the sampledated S1 (included), R2, Cir2: are the radius and the circumference of tree on the level of the sample dated S2 (included), Diff.: the differencein years for the calibrated dates corresponding to the distance S1-S2, Accr1: the estimated rate of growth

per unit of radial length in samples during the juvenile phasethan during the adult phase. On the other hand, the periodduring which the young tree becomes established in so dryan environment is probably characterized by slow annualgrowth (Fig. 6).

Some observations about specific trees are given below:

– Cypress no. 8 has laid down a radial increase of 126 mmin the 90 years between the two radiocarbon dates, givinga growth of 1.4 mm/year at this stage of its life. It wouldthus have taken 180 years to reach a girth of some 1.58 m,and its present age must be estimated to be approximately1500 years.

– With a growth rate of 0.71 mm/year, cypress no. 10 wouldhave taken 437 years to reach a girth of 1.95 m and weestimate this would make it approximately 1110 yearsold.

– In the case of cypress no. 11, its estimated growth rate of0.57 mm/year seems to us rather high, for an individualof 4.64 m girth, by comparison with the growth ratesfound for other trees of similar size. We believe this maybe an indication of lobed growth. Subject to that possiblesource of error, we can estimate the age of this tree at noless than 2250 years.

– Cypress no. 16 (girth 2.56 m) has an estimated growthrate of 0.26 mm/year, hence, we can estimate its presentage could be over 2350 years.

– The radiocarbon-estimated growth rate for cypress no. 32appears very high (1.35 mm/year) by comparison with itsgirth of 6.20 m. We suppose we may be dealing here withlobed growth, in which the cambium only functions overone part of the tree’s circumference, producing wedg-ing rings which are often wider than continuous rings.

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Cypress no. 8

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0 100 200 300 400 500 600 700 800 900 1000

Number of rings available

0 100 200 300 400 500 600 700 800 900 1000

Number of rings available

0 100 200 300 400 500 600 700 800 900 1000

Number of rings available

0 100 200 300 400 500 600 700 800 900 1000

Number of rings available

Cumulated ring-widths (mm) Cumulated ring-widths (mm)

Cumulated ring-widths (mm) Cumulated ring-widths (mm)

Cumulated ring-widths (mm)Cumulated ring-widths (mm)

Cumulated ring-widths (mm) Cumulated ring-widths (mm)

1967

Accr 1 = 1,4 mm/year

715 + 65 AD

805 + 65 AD

Accr 2 =0,08 mm/year

Cypress no. 50

1967

315 + 75 AD

460 + 10 ADAccr 1 = 0,7 mm/year

Accr 2 = 0,1 mm/year

Cypress no. 10

1967

1325 + 75AD

Accr 1 = 0,71 mm/year

1510 + 80AD

Accr 2= 0,1 mm/year

Cypress no. 11

1967

805 + 85 AD

Accr 1 = O,57 mm/year

1045 + 85 AD

Accr 2=0,07mm/year

Cypress no. 16

1967

955 + 75 ADAccr 1= 0,26 mm/year

1195 + 75 AD

Accr 2= 0,13 mm/year

Cypress no. 32

870 + 80 AD

Accr 1 = 1,25 mm/year

995 + 55 AD

1967

Cypress no. 178

1967

1075 + 55 AD

Accr 1 = 0,47 mm/year

1345 + 55 AD

Accr 2 = 0,14 mm/year

Cypress no. 179

1967

Accr 2 = 0,27 mm/year

1800 + 150 AD

Accr 1 = 1 mm/year

1640 + 150 AD

Fig. 6 Growth curves andcalibrated ages for some cypresstrees from the Tassili region.Accr1: the estimated rate ofgrowth, Accr2: the rate growthbetween 1967 and 1997

Alternatively, this could be a multi-stemmed tree whosedifferent trunks develop simultaneously as happens withyew, Taxus baccata (Uddelbuttel 1935) and the incensejuniper, Juniperus thurifera (Bertaudiere 1999). Cypressno. 32 consists of a massive trunk branching at a heightof 2 m into seven impressively large branches; we maysuppose that it is in fact a fusion of anastomosed stems,and that this gives the tree its “candelabra” shape. De-spite these interpretative complications, we estimate thatit has taken 1130 years for this tree to set up the last0.26 m of radial growth.

– The growth of cypress no. 50 was estimated at0.7 mm/year over the time it took for the tree’s girthto increase from 2.28 m to 2.64 m. It would accordinglyhave taken 1680 years to put on its last 0.275 m of radial

growth, and so we estimate that its present age would bealmost 2200 years.

– The growth rate of cypress no. 178, at a girth of 2.40 m,is estimated at 0.47 mm/year. With the assumption thatthe initial rate was the same, this tree would now be 1260years old.

– From a girth of 1.87 m to one of 2.88 m, the meangrowth rate of cypress no. 179 is estimated to have been1 mm/year. If so, we estimate its age now would beapproximately 650 years.

The eight 14C-dated trees have estimated ages rangingfrom 600 to 2400 years and they represent girth classesfrom 3 m to 7 m. These girth classes account for twothirds of the total population. This gives us some reasonto believe that the estimates offered here cover the

669

best-represented age groups and confirm the powerfulinfluence of differences in the microhabitat of the trees,as already discussed. The trees over 7 m in girth appear ingeneral to be over 2000 years old, while those under 3 mwould be less than 600 years old, and probably constituteregeneration that has occurred throughout the second halfof the last millennium, having withstood human activity(pastoralism, trampling, wood-cutting and bark-stripping).These results corroborate the observations made in thefield during 1971/1972 and 1997/2001 concerning thepresent population dynamics of this cypress (Grim 1992unpublished; Abdoun 2002; Abdoun and Beddiaf 2002).

Conclusion

The results presented here are a first attempt at quantify-ing the growth of Duprez’ cypress in its natural range. Asstated in the conclusions, this is an initial report of newwork and we believe that the conclusions section is appro-priate for an initial report. Our results illustrate the species’juvenile vigour, which can produce radial growth of up to2.23 mm/year, implying a remarkable degree of adaptationto present-day conditions in the Saharan mountains. Thisshows that its potential for reforestation in arid zones iswell worthy of attention. Its long-term performance is il-lustrated by the estimated ages which range from 600 to2400 years for the commonest sizes of this tree.

So far as the growth rhythms of this cypress are con-cerned, great variation is found among trees of similargirth, even at the same site, showing the strong influenceof microhabitat. In the case of some trees, we observedan interruption of cambium activity for a period of years,which could be a genetic adaptation to drought. Moreover,the cambium of the younger trees is capable of producingmore than one complete, clearly-defined growth ring in asingle year. Ring-width can vary from a few tens of micronsto 10 mm, but it appears very difficult to establish any linearrelationship with particular climatic conditions. The diffi-culties of cross-dating ring sequences confirm that it is im-possible to apply normal approaches of dendrochronologyand dendroclimatology to these trees. These results raisequestions about the ecophysiology of these trees: their ca-pacity to stop their growth over several consecutive yearsand their capacity to exploit atmospheric condensation fortheir water supply. This capacity would be an interestingtopic for future investigations.

This cypress appears to be little threatened by droughtand we have good evidence for its capacity for spontaneousregeneration in situ. Nevertheless it is still difficult, givenour present knowledge, to quantify the frequency of regen-eration well, due to human damage to these trees and theirenvironment. Though the trees which exist today give usthe assurance that the species is capable of surviving in itsnatural range, they cannot survive the constantly-growingdemands for wood that arise from tourist and pastoral ac-tivities. These activities have been responsible for a loss of8% of the population between 1972 and 2001 (Abdoun andBeddiaf 2002). The fact that the habitat of the trees is inside

the Tassili National Park (created in 1972) has not helpedit at all. We may hope that the tourist industry, now veryactive in the Tassili region, will involve itself more in theprotection of the area in general, for that industry’s pros-perity comes from and is dependent on the conservationand proper appreciation of this region as a whole.

Acknowledgements The authors express their heartfelt thanks to thefollowing: Sid Ahmed Kerzabi, former Bureau manager of the Tas-sili National Park, Jean-Louis Borel of the University of Provence,Mohamed Alifriqui of Semlalia University, Marrakech, Brigitte Talonof IMEP (Mediterranean Ecology and Palaeoecology Institute) andAljos Farjon of the Royal Botanic Gardens, Kew for their advice,Dick Nowell for the translation of the text of this article, Mohamedand Aıcha Touati, Mohamed Beddiaf and Omar Ghanem of the TassiliNational Park for their contributions in the field, and our guides andcamel-drivers (Mohamed Ag Ahmed, Wawa Iknan, Bilal Machar,Aıssa Taloum, Mamadou Hamid, Warzaghen Machar and Sid AliKaradji). We also thank the staff of the NSF-Arizona AMS Labo-ratory. The radiocarbon dating work at the University of Arizonawas supported in part by US National Science Foundation grant no.EAR01-15488.

References

Abdoun F (2002) Etude de la dynamique spatio-temporelle des pop-ulations de Cupressus dupreziana A. Camus au Tassili n’Ajjer,Algerie. PhD thesis Univ Aix-Marseille

Abdoun F, Beddiaf M (2002) Cupressus dupreziana A. Camus,repartition, deperissement et regeneration au Tassili n’Ajjer,Sahara Central. Comptes Rendus Biol 325:617–627

Alifriqui M, M’hirit O, Peltier J-P, Tessier L (1996) Analysecomparee de la croissance radiale du Pin d’Alep et duCypres de l’Atlas dans le Haut Atlas Occidental marocain. Den-drochronologia 14:71–87

Balachowsky AS (1955) Une relique rarissime du Sahara Central: lecypres de Duprez. La Nature 3237:20–24

Barry JP, Belin B, Celles JC, Dubost D, Faurel L, Hethener P,(1970) Essai de monographie du Cupressus dupreziana A. Ca-mus cypres endemique du Tassili des Ajjer (Sahara Central).Bull Soc Hist Nat Afrique Nord 61, 112:95–178

Bertaudiere V (1999) Dendroecologie du genevrier thurifere (Junipe-rus thurifera L.) dans la haute montagne mediterraneenne (hautAtlas, Maroc) et dans une station xerothermique des Pyreneescentrales (France). PhD thesis Univ P. Sabatier Toulouse

Capot-Rey R (1954) Une crue de l’O. Edjreou. Trav Inst Rech SaharXI:111–116

Cherubini P, Gartner BL, Tognetti R, Braker OU, Schoch W, InnesJL (2003) Identification, measurement and interpretation of treerings in woody species from Mediterranean climates. Biol Rev78:119–148

Corona E (1970) Valore dendrocronologico del cipresso sempre-verde. Monti Boschi 19(5):21–25

Dobry J, Kyncl J (1989) Cupressus dupreziana–Ohrozeny jehlicnanstrelitz sahary. Lesnictvi 35(4):371–384

Dobry J, Kyncl J (1992) Tree-ring density profiles in Cupressaceae.In: Tree rings and environment. Proc Internat DendrochronolSymp Ystad, South Sweden, Sep. 1990, Lundqua Rep 34:83–84

Dubief J (1963) Le climat du Sahara. Trav Inst Rech Sahar h.s. IIDubief J (1999) L’Ajjer, Sahara Central. Karthala, ParisFarjon A (2005) A monograph of Cupresseae & Sciadopitys. Royal

Botanic Gardens, KewGaussen H (1968) Les gymnospermes actuelles et fossiles. X, Les

cupressacees. Trav Lab Forest ToulouseGlock WS, Agerter S (1963) Anomalies observees dans les anneaux

de croissance des arbres. Endeavour 22:9–13Kaennel M, Schweingruber FH (1995) Multilingual Glossary of Den-

drochronology. Swiss Fed Inst For Snow Landscape Res, PaulHaupt, Bern

670

Knapp R (1973) Die Vegetation von Afrika. Vegetationsmonogra-phien der einzelnen Grossraume, Band III. G. Fischer Verlag,Stuttgart

Lavauden L (1926) Sur la presence d’un cypres dans les montagnesdu Tassili des Azdjers. Comptes Rendus Acad Sci 182:541–543

Lhote H (1958) A la decouverte des fresques du Tassili. Arthaud,Paris

Lucas G, Synge H (1978) The IUCN plant Red Data Book. IUCNand Natural Resources, Morges

Maire R (1933) Etude sur la flore et la vegetation du Sahara Central.Mem Soc Hist Nat Afrique, Mission du Hoggar 2:1–272

Messerli B, Kienholz H (1981) Sahara - Exkursion 1973. Geogr Univ,Bern

Meyer F (1961/1962) Das Altern der Baume. Mitt Dtsch dendrol Ges62:59

Pons A, Quezel P (1958) Premieres remarques sur l’etude paly-nologique d’un guano fossile du Hoggar. Comptes Rendus AcadSci 244:2290–2292

Quezel P (1960) Flore et palynologie saharienne. Quelques aspectsde leur signification biogeographique et paleoclimatique. BullInst Franc Afr Noire A 22:353–360

Schweinguber F-H (1988) Tree rings, basics and applica-tions of dendrochronology. Kluwer Academic Publishers,Dordrecht

Simonneau P, Debazac EF (1961) Les Cypres des Ajjer. Rev ForestFranc 2:60–67

Stewart P (1969) Cupressus dupreziana, threatened conifer of theSahara. Biol Conserv 2(1):10–12

Uddelbuttel H (1935) Zur Altersbestimmung von Eiben. Mitt Dtschdendrol Ges 47:147–154