Page 3 - Calvo_e_al_1995

Dense llnll eJCtensive bcds Iii!. in facl, alung U1e wurl~-eii.Stem. non.h·wcslcm 3Dd
we.ow:rn eoas&S (Fit> l) to co•n&:lde wirh rhe mOSt lmponant carl!onatic IUld calc:u'Cllitk
outcrops.ln 5UCh ueas;. PosldM/4 ocrtllfieil abo de~elops on rocky bouom, sometimes

CO<eted by ~ IIUll laycr o( CKpDOgttUc scdiroeoL Beside$, llloa& the \\"eSicm coastS of
Slcily, fav0111'8ble ecological eonditions and fli< natura! degrecs allowcd the settkment

and lhc developmcnt of onc or che rnost powcrfuf Posidonio oceanica mcadows in lhe

Meditr:rranell1 Sea. Mon:over, lhc de\>clopment or tbc mclldow near the shor:e-Tinc.

ractliwed by \\'ide sb.allow bou.om.s. OÒIÌMICd panicular P.osidotd<J oeMJ~Ìca reer-

(Oilfl;ltions(plDI~tndrldfbarriùc)(CAI..VO&.I'RADA'ORES'TANO,J!M)and

comributed 10make up and 10 rmaiouin nllllmlllagooo cc05btems (Sugnonc di Marsnla)
and anlficiat OIICS (s:~llillll$),

In p.vtkular. the sh311ow COòiSIII wat!'IS &long Westm~ S1clly sbowchnractcrisries of
"Q4lur.ll bboc'IIOI)'" in \\Mb u is possible l<J IC$1 mnoce scnsing leChniquos mapping
ph)'lllllcnlbk rom!Dimities and e'llllu:uing biOIIU$$ dalsÌI)' dism1)utiòo .under favourable
condirions (CAI.\'0 n o!•• 199S).

f'osidoni<J oceonictJ meado"s ~ ~ along d~e Tyrrhcni~~nlllldlonìan north-easti!m
coasts of Siclly. They an) clnuxterized by rvgged mountains cr~d by tomnl-lìke
rivcrs.(fwman:) l.nd mewnorphlc, lgtrOUs and sWimental)' rocl;s (Pcloritani Voits) and
volca.ok roda CEw MOUlluin).

In the sovt~&Sitm eoast of SiciTy muddy and unstablc sediment:s end low water
trasp;ueney cut off the sucmsiQnal stagc or Cymodoc~o trodosa (llcria) Ascherson
communities (tdaphi<- climu), especìally in lhe Gutror Gela. wbere CymoJua:a nodosa
JCtSupezte~Ui,-elllld da!sebtdsaboul 15 me11X$dqllh(TOCCAceu &RIOOIO. 1989).

Wìile m! dtllSe PO!Ìifolli4 «WJnit:O m~-s Ile on llle bociDms o(~ E,"Bdt
ortd l.!mpedu$1 i~lllnds, wllile in llle vokanic islands (Eolie. Usr~ l'llltcllcri:l and
Llllosa) Pnsidoni<J oceJJnlca bcds seule on rock a.- voleanic s~~nds mixed •vith biogcnic
cak=o-JS detritus.

On lhe whole. Potidoiii<J aua11ka me.:ld<lws are frequcnlly round along Skilion
tO!SII, sbowi~ c~itkru ~ton sio,nats up to c:omp!cte dis.1ppearnncc, ~lly ncar
lar&e urtnn8lld lndusui:ll de\'Ciopnlcru1IR&

LEAF STRUCTUREAND PHENOLOGY

Slruetdrali!IOII)'Sk daJa (IDZ'I'O andmicrodìstriburion), n:1a!cd toSIIldic.scaried 0111 in
dle Wl 6 yem aloa.g the COiUI$ of Western and Solllb-Ea.mm SicUy, an: sllowo in
Tllble l. Al10gcdlcr 2.086 Posidonia O«<nico shoou. for a tocal or 15,230 J>:aves. have
bccn collcctcd nnd cxlln\lned rn 44 samplln~ statìons rrom dcpths ur .l.S to 14 m.
Shallow Posidonia Dr:Lanicu meudows. sllow thc hlghest dc:n,~ity values which ccrrespond
ID dense and Yer)' dense pnines acconfing ID Giraud's dmifit'llrion (GIRAUO, l977).

while lof mnnber rrr slloot re:~ehcs lbt: hichcst Yllluts in autumn a.xonlina 10 lcaf

phcnol~y.

Leaf Are~ lndex (t..A.I.) and rncan leni' surface ~r shout show thc highcst v~lucs
alol'\1: the 1\Jan,l or Ustica and lhe western coast of Sidly. probably mlated lo vinu:tl
bc:k of pollution wur.el. Tbe ,-~lucs found at P.ta Bnca!ttO reflcct. iMI<:ad, 1M
premioos devclopmentof lbc prairie whìchlhows 11 patclly dl3tributioo :llld scules on
O<pDic coaa-etioos crosstd b) muddy scdimo!nts.

A prime olassifi~ion "as pcf(onned on 38 autunm sampl~ sites uslng mru:ro-
mlctodistribuu<>n variables collection. Thrce m:Un clustcrs. dwsen 11 the highes1
bim.rcltial lc•cl. scem to chanc~Ct'iu badlytllQ!nC3! rancc rather !han J'!C)arapltical

GIORfoiALE BO't'ANI(;() rTAUANO- VOL\IME l.l9, l, 1'193