BIG PELICAN

ATOLL RESEARCH BULLETIN NO. 130

A BOTANICAL DESCRIPTION OF BIG PELICAN CAY, A LITTLE KNOWN ISLAND OFF THE SOUTH COAST OF JAMAICA

by C. D. Adams

Issued by

THE SMITHSONIAN INSTITUTION Washington, D. C., U. S. A .

A u g u s t 15, 1969

BIG PELICAN

Scale

^A

CAY,

ST. CATHERINE,

JAMAICA

-4

25rnett-es

2.

Strand -dune associes 3.Strand - scmb associes 4. Strand- w o o d l a d

association

A BOTANICAL DESCRIPTION O F BIG PELICAN CAY, A LITTLE KNOWN ISLAND OFF THE SOUTH COAST OF JAMAICA

by C . D . Adams

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1/

A b s t r a c t

Big P e l i c a n Cay is an i s l a n d of 5-1/2 a c r e s composed e n t i r e l y of c o r a l sand and l y i n g about t h r e e m i l e s o f f t h e s o u t h c o a s t o f Jamaica.

The i s l a n d h a s a n a t u r a l f l o r a o f 44 s p e c i e s of v a s c u l a r p l a n t s com- p r i s i n g a v e g e t a t i o n o f s e v e r a l s e r a 1 u n i t s , comparable w i t h u n i t s d e s c r i b e d f o r t h e F l o r i d a Keys, and a woodland dominated by Conocarpus e r e c t u s . Within a s m a l l a r e a t h e v e g e t a t i o n r e a c h e s a h i g h l e v e l o f complexity and i n c l u d e s no% only common t r o p i c a l s e a s h o r e p l a n t s o f more o r l e s s xeromorphic t y p e b u t , w i t h i n t h e woodland, h e r b s , s h r u b s and t r e e s of more mesophytic c h a r a c t e r . The v e g e t a t i o n i s unusual i n t h a t n o t only i s t h e climax dominated by Conocarpus, which i s elsewhere a t r a n s i t i o n a l o r marginal s p e c i e s , b u t i t l a c k s any s i g n i f i c a n t mangrove community. This cay e x e m p l i f i e s w i t h i n t h e West I n d i a n phytogeographical r e g i o n , t h e v e g e t a t i o n o f a sand cay.

Acknowledgements

A l l i n f o r m a t i o n given i n t h i s account o t h e r t h a n t h a t o b t a i n e d from c i t e d r e f e r e n c e s o r acknowledged h e r e , i s t h e r e s u l t of t h e

a u t h o r ' s o b s e r v a t i o n s d u r i n g February/March 1963 and October 1967. The c o o p e r a t i o n o f D r . Walter C a r t e r , formerly of F . A . O . , and o f M r . Michael Campbell of Kingston, whom I accompanied on v i s i t s t o t h e i s l a n d , i s g r a t e f u l l y acknowledged. I am a l s o g r a t e f u l t o M r . Richard Wiczens, l a t e l y o f t h e Jamaican Survey Department, who arranged f o r me t o have t h e u s e o f an a e r i a l photograph from which Figure 1 was drawn, and t o M r . R. A . Gardiner o f t h e Royal Geographical S o c i e t y , f o r answering i n q u i r i e s about o t h e r maps. M r . D. 0. Vickers, D i r e c t o r o f t h e Jamaican M e t e o r o l o g i c a l S e r v i c e provided i n f o r m a t i o n about windspeeds.

P o s i t i o n and g e n e r a l d e s c r i p t i o n of Big Pelican Cay

Big P e l i c a n Cay i s an i s l a n d s i t u a t e d 2.9 miles SSW of Coleman's Bay o f f t h e southernmost t i p o f zhe H e l l s h i r e H i l l s i n t h e p a r i s h of S t . C a t h e r i n e , Jamaica. Owing t o i t s d i s t a n c e from t h e mainland, t h i s cay does n o t appear on t h e t o p o g r a p h i c a l s u r v e y maps of Jamaica

(1:50,000 e d i t i o n ) , b u t i t s p o s i t i o n i s i n d i c a t e d on t h e maps showing t h e P o r t l a n d Bight Cays accompanying t h e papers of S t e e r s , Chapman e t a l . (1944) and Chapman (1944). Admiralty Chart No. 457 (1954) also-

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1 !

S e n i o r L e c t u r e r i n Botany, U n i v e r s i t y o f t h e West I n d i e s , Mona, Kingston 7, Jamaica.

shows t h e cay on a r a t h e r s m a l l s c a l e . The i s l a n d i s one of few s c a t t e r e d along t h e almost continuous a r c o f r e e f e x t e n d i n g n o r t h - eastwards from P o r t l a n d P o i n t .

The a r e a o f t h e cay above s e a - l e v e l i s 22,650 square meters

(5.6 a c r e s ) and a t no p o i n t i s i t more than 1 . 6 meters ( 5 . 4 f e e t ) above s e a - l e v e l . The o l d e s t p a r t i s probably a t t h e e a s t e r n end and t h e i s l a n d seems t o be i n c r e a s i n g i n a westward d i r e c t i o n by d e p o s i t i o n of c a l c a r - eous sand l a r g e l y composed of fragments of Halimeda o p u n t i a and s h e l l s . This sand forms an u n d u l a t i n g s u r f a c e t o t h e whole i s l a n d where t h e r e i s v e g e t a t i o n and dhere a r e no outcrops of smashed c o r a l a s a t Lime Cay. Lime Cay i s one o f t h e well-known P o r t Royal Cays o u t s i d e Kingston h a r b o r , and i s almost t h e same s i z e a s P e l i c a n Cay. While Asprey and Robbins (1953) r e f e r t o Lime Cay a s c o n s i s t i n g o f "sand c o n t a i n i n g a h i g h p r o p o r t i o n of t h e remains of t h e l i m e - e n c r u s t i n g Halimeda opuntia"

without q u a l i f i c a t i o n , t h i s i s only t r u e of i t s leeward a s p e c t s . S t e e r s (1940) c l e a r l y d i s t i n g u i s h e s between s h i n g l e cays composed l a r g e l y o f exposed c o a r s e broken c o r a l m a t e r i a l o f which Lime Cay i s an example, and sand cays such as P e l i c a n Cay where even a t t h e v u l n e r a b l e windward

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end, t h e i s l a n d c o n s i s t s uniformly o f sand. The 1939 Cambridge expe- d i t i o n made a v e r y b r i e f survey of t h i s cay and no d e t a i l e d b o t a n i c a l d e s c r i p t i o n was i n c l u d e d i n t h e i r p u b l i c a t i o n s .

C l i m a t i c d a t a a r e l a c k i n g f o r any of t h e s e cays b u t it i s c e r t a i n t h a t one o f t h e most i m p o r t a n t f a c t o r s d e t e r m i n i n g t h e i r shape and p h y s i c a l e v o l u t i o n , a s w e l l a s t o some e x t e n t , t h e c h a r a c t e r o f t h e i r v e g e t a t i o n , i s t h e c o n s i s t e n t e a s t e r l y b r e e z e . Wave a c t i o n and s a l t s p r a y depend on t h i s wind which a t c e r t a i n times of t h e y e a r , e s p e c i a l l y i n June and J u l y , blows a t s t r e n g t h s up t o Force 5 f o r s e v e r a l d a y l i g h t h o u r s . The windward s o u t h e r n and e a s t e r n a s p e c t s a r e p r o t e c t e d by a shallow lagoon s e v e r a l hundred meters broad o u t s i d e which t h e p r i n c i p a l r e e f l i e s . Wave a c t i o n on t h e s e beaches i n normal weather amounts t o

l i t t l e more t h a n a g e n t l e l a p p i n g , b u t s a l t s p r a y from t h e r e e f i s o f t e n e v i d e n t .

Vegetation o f P e l i c a n Cay

The f o u r main communities d e s c r i b e d by Davis (J. H. Davis, 1942) f o r t h e F l o r i d a Keys can be recognized on P e l i c a n Cay and account f o r a l l t h e communities which occur t h e r e . These a r e 1. t h e Strand-beach a s s o c i e s ; 2. t h e Strand-dune a s s o c i e s ; 3. t h e S t r a n d - s c r u b a s s o c i e s and 4 . t h e Strand-woodland a s s o c i a t i o n ( t h e map, Figure 1, shows t h e i r d i s t r i b u t i o n ) .

1. The Strand-beach Associes

The p i o n e e r v e g e t a t i o n o c c u r r i n g almost a l l around t h e i s l a n d i n a narrow marginal zone

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i s not uniform and h a s t h r e e more o r l e s s d i s t i n c t f a c i e s depending on t h e o t h e r communities w i t h which it happens t o b e i n c o n t a c t :

a) Where t h e beach i s backed d i r e c t l y by t h e s t r a n d - d u n e a s s o c i e s and woodland o r t h i c k e t i s a b s e n t , t h e p i o n e e r f l o r a forms a d i s t i n c t zone w i t h s e v e r a l r e c o g n i z a b l e sub-zones. The f i r s t c o l o n i z e r s , of low cover v a l u e , a r e Sesuvium p o r t u l a c a s t r u m and Ipomoea

p e s - c a p r a e , t h e former b e i n g c o n s t a n t l y p r e s e n t and more abundant.

On t h e s h a r p l y r i s i n g upper beach t h i s open sub-zone i s r e p l a c e d a b r u p t l y by P h i l o x e r u s v e r m i c u l a r i s which t h e n by l e s s a b r u p t and i n t e r m i n g l i n g s t a g e s g i v e s way through sub-zones dominated by Euphorbia mesembrianthemifolia and t h e n Canavalia maritima t o t h e more s t a b l e dune community of almost p u r e Sporobolus v i r g i n i c u s on t h e h i g h e r b e t t e r d r a i n e d p a r t s and Paspalum d i s t i c h u m w i t h Sporobolus on t h e lower.

T h i s s e r i e s i s w e l l shown a l o n g t h e w e s t e r n h a l f o f t h e s o u t h e r n s h o r e . The most obvious i r r e g u l a r i t i e s a r e t o be found towards t h e extreme w e s t e r n t i p of t h e cay where t h e common primary i n v a d e r s may b e r e p l a c e d l o c a l l y by Paspalum d i s t i c h u m and o t h e r forward dune s p e c i e s , namely Euphorbia mesembrianthemifolia, C a n a v a l i a maritima and Cenchrus t r i b u l o i d e s . A l l t h e s e s p e c i e s , except Euphorbia mesembrianthemifolia, have t r a i l i n g branches and a r e d i c o t y l e d o n s w i t h f l e s h y l e a v e s o r a r e g r a s s e s . P l a n t s of Euphorbia mesembrianthemifolia a r e u s u a l l y bushy and may r i s e t o 45 cm (18 i n . ) t a l l . A l l t h e o t h e r s p e c i e s i n t h e t ~ i c a l

. .

exoosed p i o n e e r t o forward dune s e r i e s a r e o f lower s t a t u r e , b u t P h i l o x e r u s t e n d s t o have ascending form even i n exposed p l a c e s .

b ) Where t h e beach i s backed d i r e c t l y by t h e s t r a n d - s c r u b c a c t u s t h i c k e t , a s a l o n g t h e northwest f a c i n g s h o r e , t h e upper beach i s eroded and f r e q u e n t l y h a s a d i s t i n c t s t e p about two f e e t h i g h . Below t h e s h e l f s o formed o n l y a few t r a i l i n g stems o f Sesuvium o c c u r . On t h e t o p of t h i s s h e l f , which i s composed of deep f i n e s a n d , t h e r e i s a t h i n cover of t h e more e r e c t bushv b u t s t i l l f l e s h v leaved herbaceous s p e c i e s o f which C a k i l e l a n c e o l a t a , P h i l o x e r u s

v e r m i c u l a r i s , Euphorbia mesembrianthemifolia and S t a c h y t a r p h e t a j a m a i c e n s i s a r e t h e most conspicuous.

c) Around t h e e a s t e r n end o f t h e i s l a n d woodland e x t e n d s t o w i t h i n a meter of h i g h - w a t e r and t h u s o n l y a v e r y narrow zone of herbaceous p i o n e e r v e g e t a t i o n e x i s t s t h e r e . T h i s c o n s i s t s of o f t e n i s o l a t e d

r a t h e r p u r e s t a n d s o f C a k i l e l a n c e o l a t a , Sesuvium p o r t u l a c a s t r u m , A l t e r n a n t h e r a h a l i m i f o l i a , P h i l o x e r u s v e r m i c u l a r i s and Paspalum d i s t i c h u m . Owing t o t h e s h e l t e r provided by t h e nearby t r e e s o f Conocarpus e r e c t u s , t h e s e herbaceous p l a n t s grow t a l l e r t h a n e l s e - where on t h e i s l a n d and some of them even t e n d t o scramble among t h e lower b r a n c h e s o f t h e t r e e s . The o n l y s p e c i e s which i s conspic- uous i n a l l t h r e e f a c i e s of t h e p i o n e e r zone i s Sesuvium

p o r t u l a c a s t r u m .

S p e c i e s of t h e Strand-beach Associes

A l t e r n a n t h e r a h a l i m i f o l i a (Lam.) S t a n d l . A t r i p l e x p e n t a n d r a ( J a c q . ) S t a n d l

.

~ a k i l e l a n c e o l a t a ( ~ i l l d . ) 0 . E . Schulz C a n a v a l i a m a r i t i m a (Aubl .) Urb

.

Cenchrus t r i b u l o i d e s L .

I / Frequency

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0

Explanation of a b b r e v i a t i o n s : o , o c c a s i o n a l ; 1, l o c a l ; f , f r e q u e n t ; v r , v e r y r a r e ; f - a , f r e q u e n t t o abundant; a , abundant; o - r , o c c a s i o n a l t o r a r e ; I d , l o c a l l y dominant.

C o l u b r i n a a s i a t i c a (L.) Brongn.

Euphorbia mesembriantbemifolia J a c q . ( E . b u x i f o l i a Sw.)

Ipomoea p e s - c a p r a e ( L . ) R . B r . s s p . b r a s i l i e n s i s (L.) O o s t s t r . Paspalum d i s t i c h u m L . (P. vaginatum Sw.)

P h i l o x e r u s v e r m i c u l a r i s (L.) Beauv.

Rhizophora mangle L . ( s e e d l i n g s o r s a p l i n g s only) Sesuvium p o r t u l a c a s t r u m ( L . ) L .

Sporobolus v i r g i n i c u s (L.) Kunth S t a c h y t a r p h e t a j a m a i c e n s i s (L.) Vahl

1 f - a v r a 1

0-r

2. The Strand-dune Associes

T h i s v e g e t a t i o n comprises t h e low g r a s s l a n d community occupying t h e e x t e n s i v e d e p r e s s i o n - i n t h e middle of t h e i s l a n d and a l s o much o f t h e w e s t e r n h a l f . A t v a r i o u s p o i n t s it a b u t s on t o a l l t h e o t h e r com- m u n i t i e s and i s t h e only one which i s continuous a t t h e p r e s e n t t i m e .

I t s s e r a 1 s t a t u s i s b e l i e d by t h e s h a r p b o u n d a r i e s e x i s t i n g between t h e g r a s s l a n d and t h e t h i c k e t s o r woodlands with which i t i s i n c o n t a c t . T h i s a p p a r e n t l y s t a b l e f e a t u r e may b e a s s o c i a t e d with a h i s t o r y of goat g r a z i n g (removed i n t h e l a t t e r p a r t of 1962) and p o s s i b l y f i r e . On t h e o t h e r hand a t c e r t a i n p l a c e s i s o l a t e d o r g r e g a r i o u s shrubs o f Morinda royoc, Capparis f l e x u o s a and C a e s a l p i n i a bonduc i n young s t a g e s o f growth i n d i c a t e a developmental t r e n d towards t h i c k e t . There i s a l s o probably a slow f r o n t a l encroachment upon t h e g r a s s l a n d by t h e l a r g e r

c o n t i n u o u s a r e a s o f Opuntia d i l l e n i i which might proceed i n o p p o s i t i o n t o a g r a z i n g f a c t o r b u t be s t a b i l i z e d by f i r e . A s t h e Opuntia s c r u b i s d i s t r i b u t e d more towards s l i g h t l y h i g h e r ground a drainage o r s o i l s a l i n i t y f a c t o r might a l s o be i n v o l v e d i n d e t e r m i n i n g t h e p o s i t i o n of t h e boundary w i t h t h e g r a s s l a n d .

The g r a s s l a n d v a r i e s i n c o v e r v a l u e t o a c o n s i d e r a b l e e x t e n t , b e i n g t h i n n e s t towards t h e s o u t h w e s t , where i t i s p a t c h i l y dominated by

Paspalum, and i s i n continuous c o n t a c t w i t h t h e s t r a n d - b e a c h a s s o c i e s . Cover approaches completeness a l o n g t h e boundary w i t h t h e Conocarpus woodland i n t h e n o r t h e a s t . I t i s f a i r l y c e r t a i n t h a t t h e most dense a s p e c t s o f t h e Sporobolus g r a s s l a n d would burn with a h o t damaging f i r e a f t e r a long p e r i o d o f drought, b u t t h e i n d i c a t i o n from t h e amount o f l i v i n g and dead p l a n t m a t e r i a l which h a s accumulated i s t h a t t h i s does n o t happen f r e q u e n t l y .

I n t h e extreme n o r t h e r n p a r t o f t h e i s l a n d t h e Sporobolus g r a s s l a n d r e a c h e s t h e eroded beach and a l i t t l e west of t h a t t h e r e i s a r e l a t i v e l y p u r e and e x t e n s i v e s t a n d o f Panicum maximum.

A s a r e s u l t of human a c t i v i t y a l o n g t h e middle r e g i o n o f t h e

n o r t h w e s t e r n s h o r e and t h e p r e s e n c e o f a s m a l l house, s e v e r a l c u l t i v a t e d p l a n t s and weeds o c c u r i n d e p e n d e n t l y of t h e more n a t u r a l dune g r a s s l a n d .

S p e c i e s o f t h e Strand-dune Associes a) Dune g r a s s l a n d s p e c i e s

C a e s a l p i n i a bonduc (L.) _Roxb. woody i n v a d e r

~ a n a v a i i a m a r i t ima (Aubl

.

^{) Urb}

.

t r a i l i n g i n v a d e r Capparis f l e x u o s a (L.) L . woody i n v a d e r Cyperus p l a n i f o l i u s L . C . Rich t i g h t - h e a d e d

r u f o u s v a r i a n t E c h i t e s umbellata J a c q .

Morinda royoc L . woody i n v a d e r

Panicum maximum J a c q . n o r t h s i d e only Paspalum d i s t i c h w n L . southwest a r e a Sporobolus v i r g i n i c u s (L.) Kunth

T r i b u l u s c i s t o i d e s L .

Turnera u l m i f o l i a L. Bushy h i r s u t e v a r i a n t

Frequency

0

f - a

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b) C u l t i v a t e d p l a n t s and weeds

Agave s i s a l a n a P e r r i n e 1

Boerhavia c o c c i n e a M i l l . a l s o i n nearby dune o

C a s u a r i n a e q u i s e t i f o l i a J . R . & G . F o r s t . 1 p l a n t

Cenchrus brownii Roem. & S c h u l t . r

Cocos n u c i f e r a L. s e e d l i n g s and 6 p l a n t s

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Delonix r e g i a (Boj

.

ex Hook.) Raf. 1 p l a n t

Nerium o l e a n d e r L . 1 p l a n t

P o r t u l a c a o l e r a c e a L. a l s o i n nearby dune f

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A l l e x i s t i n g specimens of

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Cocos were removed i n 1963 i n p r e p a r a t i o n f o r an e x p e r i m e n t a l p l a n t i n g of s e e d l i n g s i n t h e n o r t h - c e n t r a l g r a s s l a n d a r e a . 3 . The S t r a n d - s c r u b Associes

T h i s comnlunity i s t h e most p a t c h y and d i s s e c t e d v e g e t a t i o n

r e p r e s e n t e d on t h e i s l a n d . I t a l s o l a c k s u n i f o r m i t y i n t h e o c c u r r e n c e w i t h i n t h e p a t c h e s of g r e g a r i o u s shrubby s p e c i e s surrounded by Opuntia d i l l e n i i . A l l examples of s c r u b have b o u n d a r i e s w i t h t h e g r a s s l a n d and most of t h e l a r g e r a r e a s a l s o have b o u n d a r i e s with Conocarpus woodland.

The d i s p o s i t i o n of s c r u b i n r e l a t i o n t o woodland i s c o n s i s t e n t l y towards t h e northwest o r leeward s i d e .

Undoubtedly t h e s t r a n d - s c r u b a s s o c i e s i s t h e most obviously s e r a 1 and u n s t a b l e v e g e t a t i o n of P e l i c a n Cay. As p l a n t s of Opuntia d i l l e n i i a r e almost everywhere contiguous i n each p a t c h o f s c r u b and form narrow hedges around t h e l a r g e r clumps o f s h r u b s , i t i s n o t p o s s i b l e f o r man o r g r a z i n g animals t o e n t e r . Being t o t h e leeward of woodland t h e s e a r e a s a r e l e a s t l i k e l y t o be a f f e c t e d by wind o r s a l t s p r a y and e x c e p t a t t h e margins would n o t b e damaged by f i r e . The community could t h e r e - f o r e be expected t o follow t h r o u g h a sequence of n a t u r a l s t a g e s l e a d i n g t o woodland.

A t t h e n o r t h e r n end of t h e l a r g e Conocarpus woodland t h e r e i s a c l e a r i n d i c a t i o n of t h e replacement of Opuntia by S u r i a n a m a r i t i m a . Here a s u b s t a n t i a l l y pure s t a n d o f S u r i a n a r i s i n g t o 2 . 5 meters (about e i g h t f e e t ) , forms a l o c a l i z e d t h i c k e t and t h i s s p e c i e s i s e v i d e n t l y competing s u c c e s s f u l l y with t h e c a c t u s i n t h a t t h e r e a r e dead o r d y i n g p l a n t s o f t h e l a t t e r w i t h i n t h e t h i c k e t . Nearby a narrow c o n t i n u a t i o n

o f t h e c a c t u s f r i n g e i s s e p a r a t e d by a h i g h e r hedge of Capparis f l e x u o s a between it and t h e woodland. The same woody s p e c i e s , a s w e l l a s Cordia

s e b e s t e n a , occur i n clumps i n t h e l a r g e s c r u b a r e a i n t h e w e s t e r n p a r t o f t h e i s l a n d . Here e n c l o s e d by c a c t u s , and a g a i n p r o b a b l y competing s u c c e s s f u l l v w i t h i t a r e Cordia s e b e s t e n a t o 3 . 5 meters (about 12 f e e t ) . . . C a p p a r i s f l e x u o s a t o 2 . 5 meters (about e i g h t f e e t ) and S u r i a n a maritima t o 1 . 5 meters ( f i v e f e e t ) . A t one p o i n t o n l y was it e v i d e n t t h a t

Conocarpus was i n v a d i n g t h e c a c t u s s c r u b d i r e c t l y .

I t i s noteworthy t h a t everywhere a s s o c i a t e d with Opuntia d i l l e n i i i n t h e more open s c r u b a r e numerous herbaceous o r woody s c r a m b l e r s and v i n e s . These t e n d t o cover and p o s s i b l y s u p p r e s s t h e c a c t u s . The sequence of e v e n t s i n t h e s u c c e s s i o n i s t h u s :

1) Opuntia d i l l e n i i and a few shrubby s p e c i e s i n v a d e t h e dune.

The l a t t e r would p o s s i b l y succumb t o f i r e and g r a z i n g , t h e c a c t u s only t o f i r e and only t h e n where d i r e c t l y i n c o n t a c t w i t h combustible m a t e r i a l such a s dead Suorobolus ²⁾ t h e c a c t u s

-

i s weakened o r s u p p r e s s e d by v i n e s such a s Canavalia : m a r i t i m a , Ipomoea t u b a and E c h i t e s u m b e l l a t a which t h e r e b y c r e a t e openings

-

w i t h i n t h e c a c t u s a r e a now p r o t e c t e d from g r a z i n g , f i r e and wind f o r , 3) t h e e s t a b l i s h m e n t o f e r e c t s h r u b s , S u r i a n a m a r i t i m a , Capparis f l e x u o s a and Cordia s e b e s t e n a . T h e r e a f t e r t h e f i e l d l a y e r i s e l i m i n a t e d by shade and

4) Conocarpus e v e n t u a l l y t a k e s o v e r . S p e c i e s of t h e S t r a n d - s c r u b Associes

C a e s a l u i n i a bonduc IL.1 Roxb.

.

^, o r i c k l v s c r a m b l e r Canavalia maritima (Aubl.) Urb.

Capparis f l e x u o s a ( L . ) L . Cordia s e b e s t e n a L .

E c h i t e s w n b e l l a t a J a c q .

Ipomoea t u b a ( S c h l e c h t . ) G . Don Morinda royoc L .

Opuntia d i l l e n i i (Ker-Gawl.) Haw.

S u r i a n a maritima L . T r i b u l u s c i s t o i d e s L .

t w i n e r

s t r a g g l i n g s h r u b s h r u b o r s m a l l t r e e t w i n e r

t w i n e r t w i n e r e r e c t s h r u b t r a i l i n g h e r b

Frequency

0

f 0-f 1 r f - a

0

d f r

4. The Strand-woodland A s s o c i a t i o n

The most advanced and s t a b l e community on P e l i c a n Cay, and t h a t which must b e r e g a r d e d a s t h e l o c a l climax, i s t h e woodland dominated by Conocarpus e r e c t u s . T h i s woodland occupies one q u a r t e r of t h e t o t a l

a r e a a t t h e e a s t e r n end and occurs a l s o i n two s m a l l e r p a t c h e s i n t h e s o u t h - c e n t e r and s o u t h w e s t . The t r e e s i n t h i s woodland a r e r a t h e r e v e n l y s p a c e d , b e i n g on an average about f o u r meters (13 f e e t ) a p a r t , r i s e t o a g e n e r a l h e i g h t of about s i x meters (20 f e e t ) w i t h o c c a s i o n a l t a l l e r examples and form a n e a r l y c l o s e d canopy. A few o t h e r s p e c i e s , n u m e r i c a l l y i n s i g n i f i c a n t i n t h e v e g e t a t i o n , grow t o t h e same dimensions a s t h e Conocarpus and i n c l u d e B u r s e r a simaruba, Metopium brownei and Citharexylum f r u t i c o s u m . Around t h e margins of t h e woodland t h e

Conocarpus t r e e s t e n d t o be of lower s t a t u r e e x c e p t along t h e n o r t h e r n s h o r e . This i s e v i d e n t l y due t o wind i n t h e s o u t h e r l y and e a s t e r l y margins b u t may b e due t o youth a l o n g t h e boundary w i t h t h e dune. The

t r e e s seem t o b e i n v a d i n g t h e dune s l o w l y and a r e mixed h e r e with t h e shrubby Capparis f l e x u o s a

.

Within t h e woodland t h e o l d t r u n k s o f Conocarpus, greyish-brown i n c o l o r and deeply long- and c r i s s - c r o s s - f i s s u r e d , a r e mainly t i l t e d and g n a r l e d s o t h a t some o f t h e l a r g e r branches r e a c h t h e ground. G i r t h s o f t h e s e t r e e s range from 89 cm (35 i n . ) t o 140 cm (55 i n . ) . There i s a s u b s i d i a r y t h i n l y d i s p e r s e d s t r a t u m of s h r u b s and s m a l l t r e e s with Capparis f l e x u o s a , t h e commonest s p e c i e s , o c c a s i o n a l l y r e a c h i n g t r e e s t a t u r e . Although t h e l e a v e s o f s p e c i e s o f Capparis v a r y g r e a t l y i n s h a p e , b e i n g narrowly l i n e a r on young s a p l i n g s and r a n g i n g t o b r o a d l y oblong (C, f l e x u o s a ) o r l a n c e o l a t e ( C . f e r r u g i n e a ) , t h e two s p e c i e s a r e e a s i l y d T s t i n g u i s h e d by t h e l e a v e s

07

t h e former b e i n g e n t i r e l y g l a b r o u s and t h o s e of t h e l a t t e r h a v i n g s t e l l a t e s c a l e s on t h e a b a x i a l s u r f a c e .

The western boundary o f t h e main a r e a o f woodland i s i n c o n t a c t w i t h t h e dune g r a s s l a n d a t t h e s o u t h e r n p a r t and with s c r u b a t t h e n o r t h e r n p a r t where a narrow s t r i p o f Opuntia d i l l e n i i e x t e n d s between t h e woodland and dune. The margin o f t h e woodland a l o n g t h i s boundary comprises younger p l a n t s o f Conocarpus mixed with Capparis f l e x u o s a and C . f e r r u g i n e a . The herbaceous s p e c i e s R i v i n a h w n i l i s and Turnera

-

u l m i f o l i a a r e a l s o p r e s e n t . Exposed more open and b e t t e r i l l u m i n a t e d p a r t s o f t h e woodland have a few p l a n t s o f t h e c l i m b e r s Ipomoea t u b a and

-

C a n a v a l i a maritima which may be r e l i c t from t h e s c r u b a s s o c i e s . Along t h e e a s t e r n s e a s h o r e t r e e s come c l o s e t o t h e beach, being s e p a r a t e d from it by a narrow mixed herbaceous l i t t o r a l zone ( s e e 1, c ) .

There i s no obvious i n d i c a t i o n of edaphic d i f f e r e n c e s d e t e r m i n i n g t h e boundary between t h e woodland and t h e dune b u t t h e woodland i t s e l f produces a deep l e a f l i t t e r and s u p e r f i c i a l humus i n t h e i n t e r i o r where t h e r e i s very l i t t l e herbaceous v e g e t a t i o n . I t i s noteworthy t h a t Cyperus p l a n i f o l i u s and Turnera u l m i f o l i a occur t h e r e i n forms d i s t i n c t from t h o s e which t h e s e s p e c i e s adout i n t h e e r a s s l a n d . The woodland

-

forms have a much more mesophytic appearance t h a n t h e i r c o u n t e r p a r t s o u t s i d e t h e woodland a n d , combined with t h e p r e s e n c e of R i v i n a h w n i l i s and a w e l l e s t a b l i s h e d p a t c h o f Wedelia t r i l o b a t a , i n d i c a t e t h e dependence o f t h e s e h e r b s on t h e shade and lower t e m p e r a t u r e s o f t h e woodland

i n t e r i o r .

S p e c i e s o f t h e Strand-woodland A s s o c i a t i o n Frequency A l t e r n a n t h e r a h a l i a i f o l i a (Lam.) S t a n d l . b e t t e r lit

seaward margins 1

Avicennia g e n i n a n s ( L . ) L . s e a s h o r e margins r & 1

Bursera simaruba ( L . ) S a r g . r

C a e s a l p i n i a bonduc ( L .) Roxb. marginal c l i m b e r r Canavalia maritima (Aubl .) Urb. marginal c l i m b e r r

Capparis f e r r u g i n e a L . o

Capparis f l e x u o s a

(L.)

L . f

Citharexylum f r u t i c o s u m L . v r

Coccothrinax j a m a i c e n s i s R.W. Read ( 2 p l a n t s ) r

Conocarpus e r e c t u s L . d

Cyperus p l a n i f o l i u s L . C . Rich d i f f u s e - h e a d e d g r e e n v a r i a n t Gossypium h i r s u t u m L . v a r . m a r i e - g a l a n t e

(Watt) J . B . Hutch. ( 1 p l a n t )

Ipomoea t u b a ( S c h l e c h t . ) G . Don marginal c l i m b e r L a g u n c u l a r i a racemosa (L.) G a e r t n . f . s e a s h o r e margins Metopium brownei ( J a c q . ) Urb.

T o r r u b i a o b t u s a t a ( J a c q . ) B r i t t o n ( 1 p l a n t ) R i v i n a h u m i l i s L .

Solanum bahamense L .

T r i c h o s t i g m a octandrum (L .) H . Walt. i n t e r i o r c l i m b e r Turnera u l m i f o l i a L . a t t e n u a t e d g l a b r e s c e n t v a r i a n t V a l l e s i a a n t i l l a n a Woodson ( 1 p l a n t )

Wedelia t r i l o b a t a (L.) H i t c h c .

R e p r e s e n t a t i o n o f Mangrove S p e c i e s on P e l i c a n Cay

While a l l t h r e e o f t h e commonly o c c u r r i n g American s p e c i e s o f mangroves have been r e p o r t e d from P e l i c a n Cay t h e y have f a i l e d t o e s t a b l i s h themselves s u f f i c i e n t l y t o form a community o r t o c o n t r i b u t e s i g n i f i c a n t l y t o any o f t h e communities a l r e a d y d e s c r i b e d . Avicennia germinans i s r e p r e s e n t e d by t h r e e p l a n t s ; one o l d t r e e mentioned by S t e e r s (1940), which had reached q u i t e l a r g e dimensions grew a t t h e most e a s t e r l y p o i n t o f t h e i s l a n d b u t was f e l l e d i n about 1964. Other younger p l a n t s o c c u r w i t h a few p l a n t s o f Laguncularia along t h e

s o u t h e r n margins of t h e Conocarpus woodland.

S t e e r s (1940) and p a r t y i n 1939 r e p o r t e d t h a t "near t h e s o u t h e r n end o f t h e windward s i d e a t l e a s t f o u r s e e d l i n g s o f Rhizophora have t a k e n r o o t on t h e r e e f n e a r t h e cay." One s e e d l i n g of Rhizophora mangle was s e e n r o o t e d i n t h e s h a l l o w lagoon about two meters o f f t h e western s h o r e i n 1963. This p l a n t was n o t s e e n i n 1967 b u t f i v e young p l a n t s have s i n c e become e s t a b l i s h e d o f f t h e s o u t h e r n s h o r e . Two o f t h e s e a r e s a p l i n g s about one meter t a l l . I t i s obvious t h a t many s e e d l i n g s o f t h i s s p e c i e s must be c a r r i e d t o t h e cay from t h e e a s t b u t although some o f them r o o t on t h e r e e f o r i n t h e lagoon t h e y seem t o be t r a n s i e n t and none h a s s u r v i v e d t h e r e t o make a s t a b l e u n i t of mangrove v e g e t a t i o n .

The c o n t r a s t between t h e n e g l i g i b l e c o n t r i b u t i o n o f mangroves t o t h e v e g e t a t i o n of t h i s i s l a n d and t o t h a t o f o t h e r i s l a n d s where man- groves form d i s t i n c t communities o f t h e i r own, emphasizes one o f t h e main d i f f e r e n c e s between t h i s sand cay and t h e s h i n g l e cay, e x e m p l i f i e d by Lime Cay.

A f f i n i t i e s o f t h e F l o r a

Common widespread t r o p i c a l l i t t o r a l s p e c i e s comprise t h e e a r l y s e r a 1 s t a g e s a s would be e x p e c t e d . Among t h e woody components o f t h e more s t a b l e phases a r e West I n d i a n u l a n t s o f more l i m i t e d d i s t r i b u t i o n

e . g . S u r i a n a m a r i t i m a , Cordia s e b e s t e n a and Capparis f e r r u g i n e a . I t i s among t h i s group o f l i f e forms, t h e s h r u b s and t r e e s , t h a t t h e most s i g n i f i c a n t comparisons i n f l o r i s t i c composition can be made between t h e i s l a n d s and a d j a c e n t mainland f o r m a t i o n s .

P e l i c a n Cay i s n e a r e s t t o t h e s o u t h e r n H e l l s h i r e H i l l s which s u p p o r t a v e g e t a t i o n o f t h i c k e t and woodland on l i m e s t o n e . This a r e a i s c a l c a r - eous and rocky o r sandy t o t h e s e a .

S e v e r a l non-maritime s p e c i e s a r e common t o t h e H e l l s h i r e H i l l s t h i c k e t s and P e l i c a n Cay; a l l have b a c c a t e o r drupaceous f r u i t s and have n o t been r e p o r t e d from Lime Cay. These i n c l u d e :

Bursera simaruba

Citharexylum f r u t i c o s u m Coccothrinax j a m a i c e n s i s Metopium brownei

Solanum bahamense T o r r u b i a o b t u s a t a T r i c h o s t i g m a octandrum V a l l e s i a a n t i l l a n a

For comparison Lime Cay, which i s c l o s e t o t h e s h i n g l e , p e b b l e and n o n - c a l c a r e o u s sand s p i t known a s P a l i s a d o e s , h a s t h e f o l l o w i n g s p e c i e s i n common with P a l i s a d o e s which a r e a b s e n t from P e l i c a n Cay:

~ a n ~ r o v e s

Avicennia germinans

form in^

communities

~ h i z o ~ h o r a - m a n g l e

-

I I 1 ,

Languncularia racemosa ^{" I I} Non-mangroves

Acacia t o r t u o s a B a t i s maritima C a s s i a e m a r g i n a t a Coccoloba u v i f e r a

Alteramnus l u c i d u s (Gymnanthes l u c i d a ) Lemaireocereus h y s t r i x

P i s c i d i a p i s c i p u l a

P i t h e c e l l o b i u m u n g u i s - c a t i Stigmaphyllon emarginatum T h e s p e s i a populnea

These non-mangroves a r e a l l s p e c i e s o f some importance i n Jamaican, i f n o t West I n d i a n , c o a s t a l f o r m a t i o n s and it i s remarkable t h a t t h e y do n o t o c c u r on P e l i c a n Cay. The f r u i t s a r e mostly d r y and q u i t e d i f - f e r e n t from t h o s e o f t h e p l a n t s i n t h e P e l i c a n Cay l i s t . I t i s p o s s i b l e t h a t f r u i t - e a t i n g b i r d s have been r e s p o n s i b l e f o r a r e l a t i v e l y g r e a t e r c o n t r i b u t i o n t o t h e P e l i c a n Cay f l o r a t h a n t o t h e p l a n t c o l o n i s a t i o n of Lime Cay. P e l i c a n Cay i s much f a r t h e r t h a n Lime Cay from t h e mainland and i t i s l e s s f r e q u e n t l y v i s i t e d by man. Thus d i f f e r e n c e s can be

a t t r i b u t e d t o p r o x i m i t y and o p p o r t u n i t y t o some e x t e n t , b u t i t i s b e l i e v e d t h a t t h e s e d i f f e r e n c e s a l s o r e f l e c t an e c o l o g i c a l d i s t i n c t i o n

r e s u l t i n g from t h e

-

sand and s h i n g l e s t r u c t u r e r e c o g n i z e d by S t e e r s . These two cays each have 44 s p e c i e s o f v a s c u l a r p l a n t s b u t o n l y 24 s p e c i e s i n common. P e l i c a n Cay h a s a more mesophytic a s p e c t t h a n Lime Cay, emphasized by t h e absence o f b o t h xeromorphic woody legumes and h a l o p h y t i c mangroves. Both i s l a n d s l a c k e p i p h y t e s .

LITERATURE CITED

Asprey, G . F . & Robbins, R . G . 1953. The v e g e t a t i o n o f Jamaica. Ecol.

Monogr. 23: 359-412.

Chapman, V. J . 1944. The 1939 Cambridge U n i v e r s i t y E x p e d i t i o n t o Jamaica. P a r t I . A s t u d y o f t h e b o t a n i c a l p r o c e s s e s concerned i n t h e development o f t h e Jamaican s h o r e - l i n e . J o u r n . Linn.

Soc. London 52: 407-447.

Davis, J . H . 1942. The ecology o f t h e v e g e t a t i o n and topography of t h e sand keys o f F l o r i d a . Pap. T o r t . Lab. 33: 113-195 o r Carnegie I n s t . Washington Publ. 524.

S t e e r s , J . A. 1940. The c o r a l cays o f Jamaica. Geog. J o u r n . 95 ( 1 ) : 30-42.

S t e e r s , J . A . , Chapman, V. J . ,

- -

e t a l . 1940. Sand cays and mangroves i n Jamaica. Geog. J o u r n . 96 ( 5 ) : 305-328.

Other r e f e r e n c e s

Bengry, R . P . 1954. Lime Cay. N a t u r a l H i s t . Notes, I n s t . Jam. 6 5 : 69-70.

S t e e r s , J . A . 1940. The Cays and t h e P a l i s a d o e s , P o r t Royal, Jamaica.

Geog. Rev. 30 (2) : 279-296.

P l a t e 1. South s h o r e and s o u t h e a s t t i p . P i o n e e r zone on beach ~. ^~~~

(Sesuvium) backed by ~ ~ o r o b o i u s and C a n a v a l i a . Conocarpus woodland a t e a s t e r n end s e p a r a t e d from g r a s s l a n d by t h i c k e t i n middle d i s t a n c e . Note absence o f o f f s h o r e p l a n t s o f Rhizophora (hiarch 1963).

P l a t e 2 . S o u t h e a s t s h o r e and t i p . Conocarpus woodland i n c o n t a c t w i t h Sesuvium a t l e f t . Note f i v e s a p l i n g s o f Rhizophora o f f s h o r e

(October 1 9 6 7 ) . I h e r e e f i s j u s t below t h e h o r i z o n .

P l a t e 3 . Boundary of Sporobolus g r a s s l a n d and t h i c k e t n e a r t h e n o r t h - c e n t r a l p a r t of t h e i s l a n d . Sporobolus and C a n a v a l i a i n l e f t foreground. Hedge of 9 u n t i a s e p a r a t e s g r a s s l a n d from

S u r i a n a b e h i n d .

P l a t e 4 . Typical o l d t r e e of Conocarpus i n woodland. Note s a p l i n g s of Conocarpus and s o l i t a r y p l a n t of O p u i ~ t i a ( i n lower l e f t c o r n e r ) i n otherwise open f i e l d l a y e r .