NGHIN CU MI LIN H GIA C TNH PHN B CA THC VT NGP MN VI MN T, TN SUT NGP TRIU TI VNG VEN SNG RCH C MAU

Hong Vn Thi Phn vin Nghin cu Khoa hc Lm nghip Nam B

TM TT Nghin cu c thc hin ti vng ven sng rch tnh C Mau, vi mc tiu nghin cu v thnh phn loi thc vt v xc nh mc nh hng ca cc nhn t mi trng n phn b cc loi thc vt rng ngp mn, nhm c c cc cn c khoa hc xut cc bin php la chn loi cy trng thch hp cho vic ti to rng phng h ven sng mt cch bn vng. Tin hnh lp 3 tuyn iu tra thng gc vi hng b bin, i din cho cc dng ngp triu khc nhau, mn nc bin khc nhau trong vng nghin cu, iu tra thnh phn loi, o phu din, ly mu t su 0-10cm v 40-50cm, cm cc o thy triu. Kt qu cho thy khu vc nghin cu c 33 loi ca 20 h thc vt . Gm nhm cy ngp mn chnh thc, bao gm 23 loi, nhm loi cy kt hp vi rng ngp mn gm 10 loi. Loi c mt cy chim nhiu nht l loi Mm trng (AA) tip theo l c (RA), cc loi Trang (KC), Vt tch (BP), Bn chua (SC) c mt thp nht l 0,1% cc loi. Loi c v Mm trng c s ln xut hin trung bnh l 70,1% v 54,5%. Cc loi ng, D vi, Bn trng, Bn chua, Ch l, Trang t t l xut hin thp nht ch c 1,3- 3,9%. c c phm vi phn b rt rng, nhng thch hp mn t 30-35 v vng c tn sut ngp triu trung bnh cao. Loi D qunh phn b thch hp trong phm v mn t t 30 -39, c tn sut ngp triu t 3- 6 ngy/thng. Loi D vi t 30-35 v phn b nhiu ngp t trung bnh n trung bnh cao. Vt d phn b kh tp trung mn 24,5-32,5 v gp nhiu vng ngp 5-13 ngy/thng. Mm trng phn b tp trung mn cao t 30-38,5 ngp t L1-L3. Mm en phn b nhiu mn thp t 19,8 -38 v ngp 1 - 10 ngy/thng. T kha: Loi cy, Ngp mn, mn, Ngp triu, Phn b T VN Rng ngp mn(RNM) hin nay b suy thoi mt cch nhanh chng, k c v s lng v cht lng rng. C nhiu nguyn nhn, trong nguyn nhn quan trng l s thiu hiu bit v vai tr, chc nng v cu trc rng, cng nh mi quan h gia RNM v mi trng. iu dn n cch ng x khng cng bng i vi RNM, kt qu l hoch nh chnh sch ch ch trng n li ch kinh t m khng ch n gi tr kinh t mi trng m chng c th mang li. H sinh thi rt nhy cm, khi s dng h sinh thi ny cn phi ch ti hai nhm nhn t bn trong v cc nhn t bn ngoi h thng. qun l rng bn vng rt cn hiu bit v cc nhm nhn t bn trong ca h sinh thi rng nh cu trc sinh thi: thnh phn loi, tnh a dng sinh hc cu trc h thng theo khng gian v thi gian m h sinh thi tn ti v pht trin. Hn na, cn phi c s hiu bit v cc tc ng ca cc yu t mi trng ln s pht trin ca RNM nh iu kin t ai, ch ngp triu, mn cc nhn t ny tc ng rt khc nhau ln tng loi cy RNM cng nh phm vi phn b ca chng. Cc tc ng ca cc nhn t mi trng cng ht sc a dng v khng tun theo quy lut, iu rt d gy tn thng cho RNM. Do , vic nghin cu v thnh phn loi thc vt RNM phn b ven sng rch v xc nh mc nh hng ca cc nhn t mi trng nh thun thc, mn t v tn sut ngp triu n phn b cc loi thc vt RNM l vic lm cn thit, nhm c c cc cn c khoa hc xut cc bin php la chn loi cy trng thch hp v c cc gii php ti to rng phng h ven sng mt cch bn vng. PHNG PHP NGHIN CU

Phng php iu tra thc a

+ Lp 3 tuyn iu tra thng gc vi hng b bin, i din cho cc dng ngp triu khc nhau, mn nc bin khc nhau trong vng nghin cu. Trn cc tuyn lp cc o m c din tch 100m2. + V tr c b tr theo tuyn iu tra, c mi khi c s xut hin ca mt loi mi th lp nghin cu, c ly cc nghin cu trung bnh 2000m + Ch tiu o m: o m thnh phn loi, xc nh chnh xc tn loi. + Khoan phu din n su 50cm bng D-corer, ly mu su 0-10cm v 40-50cm + Cm cc theo di mc ngp triu, mi cm 1 cc +Thu thp ti liu v t ai, ch ngp, thm thc vt khu vc nghin cu

Phng php o mn t: o trc tip ngoi ng sau khi khoan, bng my o mn theo phng php ca English et al (1994)

Phng php o tn sut ngp triu + Cm cc o mc ngp triu ti cc nghin cu, o mc nc ngp v i chiu vi ct theo di chun ti C Mau. Vic theo di mc nc thu triu ln xung hng ngy, bao gm triu cao nht v triu thp nht c thc hin bng cch ghi chp mc nc trn ct o thu triu chun t thng 5 nm 2005 n thng 4 nm 2006. + Tn sut ngp triu khu vc nghin cu c phn chia theo cch phn chia ngp ca (de Hann,1931), ngp triu c phn chia thnh 5 lp:

Tnh ton cc gi tr c trng ca qun x thc vt + Mt tng i (Relative density) = 100 * ni/ N (a) +Tn sut tng i (Relative frequency) = 100 * fi/ F (c) Trong : - ni l s c th ca loi th i

- N l tng s c th - fi tn sut xut hin ca loi th i - F tng tn sut

Phn tich mi lin h: gia s phn b thc vt RNM v mn t, ngp triu theo

phng php hi quy. KT QU V THO LUN Thnh phn loi thc vt RNM

Kt qu iu tra kho st cc im nghin cu dc theo cc tuyn C Mau - Ci Nc - Ca sng By Hp, C Mau - Nm Cn - Ca ng Trang v tuyn C Mau - m Di - H Gi, xc nh c thnh phn loi thc vt gm 33 loi hin c ca 20 h thc vt (Ph lc 1). Phn chia theo iu kin mi trng sng thnh 2 nhm thc vt chnh.

Nhm cy ngp mn chnh thc, bao gm 23 loi thuc 11 h thc vt, trong c 19 loi thn g, 4 loi dng cy bi v thn tho. Trong nhm cy thn g th h c (Rhizophoraceae) c 8 loi chim u th v c th v s loi, tip n l h bn (Soneratiaceae), h mm (Avicenniaceae), h xoan (Meliaceae), h cau da (Palmeae) mi h c 2 loi. Trong nhm cy thn tho th h r (Acanthiaceae) c 2 loi, cc h khc mi h c mt loi Kt qu nghin cu cho thy khu vc c s lng loi cy ngp mn chnh thc kh phong ph gm 23 loi/ 34 loi cy ngp mn ca Vit Nam (Phan Nguyn Hng & nnk, 1997), trong khi c ch hn c mt loi v Bangladesh ch hn c hai loi. Khu tr sinh quyn Cn Gi, thnh ph H Ch Minh c tng s 33 loi cy rng ngp mn chnh thc (L c Tun & nnk, 2002). Nh vy, chng t rng thc vt RNM phn b ven cc sng rch C Mau l kh phong ph v a dng, a dng c v loi v dng sng.

Nhm cy tham gia RNM c 10 loi thuc 9 h thc vt, cc loi cy thn g hin din c Bnh bt (Annona glabra), Tra nht (Hibicus tiliaceus), Trm (Melaleuca cajuputy) v Ga

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(Ficus microcarpa). Loi dng cy bi v thn tho c cc loi nh: Lc(Pluchea indica), Rau mui (Wedelia biflora), Cc kn (Derris trifolia), Choi (Stenocholena palustric), Chm gng(Clerodendrum inerme) v U du (Cyperus elatus) ( Ph lc 2)

Kt qu tnh ton cc ch s c trng ca qun x thc vt RNM ti cc im nghin cu Mt s c trng ca qun x c th hin trong Bng 1 di y:

Bng 1. Kt qu tnh ton v mt , tn sut xut hin ca cc loi trong qun x thc vt

RNM

Mt Tun sut Loi cy

Tn khoa hc

Trung bnh

Tng i (%)

T.sut (ln)

Trung bnh

Tng i (%)

c Rhizophora apiculata 11,3 20,6 54 70,1 19,9 ng Rhizophora mucronata 0,2 0,3 2 2,6 0,7 D vi Ceriops tagal 0,2 0,4 3 3,9 1,1

D qunh Ceriops decandra 3,0 5,5 17 22,1 6,3

Vt d Bruguiera sexangula 3,9 7,1 23 29,9 8,5 Vt tch Bruguiera parviffora 0,1 0,3 4 5,2 1,5 Mm trng Avicennia alba 13,4 24,4 42 54,5 15,4 Mm en Avicennia officinalis 5,3 9,6 26 33,8 9,6 Xu sng Xylocarpus moluccensis 0,5 0,9 8 10,4 2,9 Xu M.K Xylocarpus mekonggensis 0,6 1,0 12 15,6 4,4

Gi Excoecaria agallocha 2,9 5,2 22 28,6 8,1

Cc trng Lumnitzera racemosa 1,0 1,9 4 5,2 1,5 Bn trng Sonneretia alba 0,2 0,4 3 3,9 1,1 Bn chua S.caseolalis (L.) Engler 0,1 0,1 3 3,9 1,1 Ch l Phoenix paludosa 0,2 0,3 1 1,3 0,4

Da nc Nipa fruticans 8,3 15,0 21 27,3 7,7 Quao nc Dolichandrone spathacea

0,5 0,9 9 11,7 3,3 Tng cng 54.9 100.0 353.2 100.0

Bng 1 ch ra mt trung bnh ca cc loi cy thn g chim c trong cc im nghin

cu l 54,9 cy/100m2 hay 5.490 cy/ha; tuy nhin, mt trung bnh ca mi loi li rt khng ng u. Loi c mt cy chim nhiu nht l loi Mm trng (AA) v ba loi c s lng c th trung bnh thp nht l Trang (KC), Vt tch (BP), Bn chua (SC) vi 10 cy/ha v vi mt tng i ch l 0,1% cc loi.

V tn sut xut hin ca loi ti cc nghin cu th c v Mm trng c s ln bt gp cao nht. iu cho thy 2 loi trn phn b rng ri trong khu vc rng ngp mn C Mau.

Cc loi Quao nc, Xu sng, Vt tch, Cc trng c s ln bt gp t. Nh vy, cc loi ny t ph bin v ch phn b trong nhng iu kin nht nh .

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Cc loi c s ln bt gp rt thp nh ng, D vi, Bn trng, Bn chua, Ch l, Trang chng t rng cc loi trn rt t gp trong cc qun x thc vt ngp mn v phn b rt hn ch trong khu vc nghin cu. Kt qu kho st mn t, tn sut ngp triu ven sng rch C Mau

Kt qu kho st mn t Khu vc nghin cu c mn t tp trung mn 30 - 35 (cp mn M4) chim

ti 34/76 (44,7%) nghin cu. K tip l mn 35-40 (cp mn M5) chim t l ln th 2 l 27,6% (21/76) tng s . mn 25-30 (cp mn M3) chim 13,2% cc nghin cu .

Hai cp mn t t 15-20 (cp mn M1) v mn t t 20-25 (cp mn M2) c t l t nht, mi cp c s hin din ch 1 v 4 nghin cu, chim t l 1,3% v 5,3 %. mn t 40-45 (cp mn M6) c 6 im kho st vi t l 7,9%

mn t cng c s thay i tng mt v gn bng vi mn ca nc, tng mt thng c mn cao hn v gim dn xung cc tng su k tip. Kt qu kho st ngp triu Kt qu o ngp triu ti cc nghin cu v s liu theo di thu triu hng ngy ti ct o thu triu chun lp c bng tn xut ngp triu cho tng nghin cu. Cc im nghin cu tri rng khp cc dng ngp triu. Tuy nhin, ngp triu ca khu vc ch yu tp trung vng ngp triu trung bnh cao (cp ngp L3), vi 27 im chim ti 35,5% cc nghin cu, tip n l vng b ngp do triu trung bnh cao cp ngp L2, vi 22 im chim 28,95% cc nghin cu.

Vng ngp triu thp (cp ngp L1) c 14 im, chim t l 18,4% cc nghin cu, tp trung khu vc gn ca sng By Hp v ca sng ng Trang. c trng ca khu vc ny l gn nh ngp nc 2 ln trong ngy vi ngp bnh qun cao (70cm), thc vt phn b y ch yu l Mm trng, Bn trng.

Vng ch b ngp khi triu cng (cp ngp L4) xut hin khu vc c dng t cao, y l vng t c cc loi thc vt nh gi, ch l, lc, rau mui... pht trin mnh. Cp ngp ny phn b 10 nghin cu chim t l t khong 13,2% s iu tra.

Vng b ngp bi triu bt thng (cp ngp L5), ch vi 3 im chim 3,9% cc nghin cu Thit lp mi lin h v xy dng phng trnh tng quan gia phn b ca cc loi thc vt RNM v mn t, tn sut ngp triu

Nguyn tc xy dng m hnh tng quan phi c chui s liu tng i y , ni chung l s cp n phi kh ln (thng thng n>= 5) m bo cho m hnh c chnh xc cao (Bi Vit Hi, 2003)

T cc nguyn tc nu trn vic xy dng m hnh tng quan ch thc hin c i vi mt s loi. Trong tng s cc loi cy ngp mn thn g chnh thc c mt ti khu khu vc nghin cu, th ch c 11 loi l cc iu kin a vo xy dng phng trnh tng quan.

Tuy nhin, vic thit lp cc phng trnh tng quan ch thc hin c i vi 5 loi cy RNM chnh thc ti khu vc nghin cu v kim tra s tn ti ca phng trnh. Phng trnh hi quy c thit lp gia s phn b ca loi cy RNM (Yi) v mn t (X1). Tn sut ngp triu ( X2) c m t cho tng loi cy RNM. Phn b ca loi c (RA) v loi ng (RM)

Phn b ca loi c c phm vi phn b theo mn t t 19,8 44,6, mn 30-35 chng mc thnh qun x thun loi vi 100% s cy l c. iu th hin rng mn 30-35 l thch hp nht cho c sinh trng v pht trin. Theo Phan Nguyn Hng (1990) th c thuc loi chu c mn tng i rng, chng loi chu c mn trung bnh t 15-30. Bunt (1982) cho rng R.apiculata phn b ch yu pha di mn cao. Khi

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nghin cu tng quan gia gradient mn vi loi cy RNM min ng -Bc Queenland William and Clay (1982) cho rng loi R. apiculata c tng quan thun, chng ch mc ni c mn cao m khng c ni c mn thp.

Gp c phn b cc nghin cu trn tt c cc vng t t khng thun thc n thun thc v c thy ph bin dng gn thun thc n bn thun thc. Phn b ca c (RA) tri rng t vng c triu thp L1 n triu cao L5, nhng gp nhiu ngp triu L2, L3; vi s lng ca loi ng o chim ti 70-100% chng t rng phn b ca loi (RA) thch ng vi t c ngp triu cao. Qun th R. apiculata thch hp vi iu kin cao hn mc triu bnh thng trn t mn ngp mn (Mochida et al,1999).

i vi loi (R. apiculata) mn ca nc, t thch hp nht vo khong 2530, ngp triu trung bnh t 100 300 ngy/ nm, l thch hp cho s sinh trng ca c (ng Trung Tn, 2000) - Phng trnh tng quan gia phn b ca RA v mn t (phng trnh n bin) c dng:

YRA = 1/(0.0275209 + 0.451739/X1) (1) Vi R2= 0.12; Ftnh = 7,22; vi P= 0.0096(P

- Phng trnh tng quan gia phn b ca BS v mn t (phng trnh n bin) c dng:

YBS = 1/(-0.0324106 + 1.78375/X1) (2) Vi R2= 0.23; Ftnh =5.93; vi P= 0.0244 (P

Phn b ca loi Gi (EA), Da nc (NF) v Quao (DS) Gi (EA) phn b mn kh rng t 28,5-41,5, tp trung nhiu mn 30-35,8.

Hai loi Da nc (NF), Quao nc (DS) c v tr phn b theo mn t ging nhau u t 24,3 - 36,5; tuy nhin, loi NF thch hp mn 28,5 - 33,5, loi DS li l 29.

Kt qu nghin cu khu a dng sinh hc RNM C Mau cho thy phn b ca loi gi (EA) tp trung mn t 24,2 38,3; loi da nc (NF) ch tp trung mn t 21,3 26,3 (Hong Vn Thi, 2004). Trong phm vi khu vc nghin cu th y l loi thch ng vi bin dao ng mui hp, iu c s khc bit vi nhn xt ca Phan Nguyn Hng (1990) cho rng loi gi l loi chu c bin ng ln v nng mui. Tuy nhin, theo Bunt (1982), th Excoecaria agallocha phn b ch yu pha trn ni c mn thp, E. agallocha c vng c mn thp (William and Clay, 1982). i vi loi NF trong phm v khu vc nghin cu th y l loi thch ng vi bin dao ng mui hp v l loi sinh sng mn thp nht so vi cc loi cy ngp mn khc, iu ph hp vi nhn xt ca Phan Nguyn Hng (1990) cho rng loi da nc l loi hp mui. Theo ng th y l loi cy nc l in hnh .

Loi EA, NF, DS phn b tn sut ngp triu t L2- L4 vi s ngy ngp t 2- 19 ngy/thng; Loi EA phn b nhiu cp ngp L3 v L4, tc l t ngp nc t 4 - 6 ngy/thng; loi DS tp trung mc ngp L3; trong khi loi NF tp trung cp ngp L2- L3 (tn sut ngp 6-14 ngy/thng) Phn b ca Cc trng (LR), Bn trng (SA), Bn chua (SC) v Ch l (PP)

Cc trng (LR) phn b vng c mn cao 30-40. C tc gi cho rng loi Lumnitzera racemora c th chu c mn ln ti 90 (Macnae, 1968), trong khi Phan Nguyn Hng (1990) cho rng loi Cc trng l loi chu c mn cao trung bnh t 15 30. V tn sut ngp triu v thnh thc t th loi LR phn b mc ngp triu t L3-L4 v phn b vng c t bn thun thc n gn thun thc.

Bn trng (SA) phn b 30-40, trong khi Bn chua (SC) li t 25-35; ngp m SA thng gp l L2-L3 trong khi SC ch gp ngp L2.

i vi loi Ch l(PP) gp phn b mn 30-35, vi ngp triu L4 v dng t gn thun thc n thun thc. Kt lun 1. Khu vc nghin cu c 33 loi ca 20 h thc vt. Trong , nhm cy ngp mn chnh thc,

bao gm 23 loi thuc 11 h thc vt v nhm loi cy kt hp vi rng ngp mn gm 10 loi cy thuc 9 h thc vt.

2. Loi c mt cy chim nhiu nht l loi Mm trng (AA) tip theo l c (RA), cc loi Trang (KC), Vt tch (BP), Bn chua (SC) c mt thp nht l 0,1% cc loi. Loi c v Mm trng c s ln xut hin trung bnh l 70,1% v 54,5%. Cc loi ng, D vi, Bn trng, Bn chua, Ch l, Trang t t l xut hin thp nht ch c 1,3- 3,9%.

3. Loi c c phm vi phn b rt rng trong vng ngp mn, nhng thch hp mn t 30-35 v vng c tn sut ngp triu trung bnh cao.

4. Loi D qunh phn b thch hp trong phm v mn t t 30 39, c tn sut ngp triu t 3- 6 ngy/thng. Loi D vi t 30-35 v phn b nhiu ngp t trung bnh n trung bnh cao.

5. Vt d phn b kh tp trung mn 24,5-32,5 v gp nhiu vng ngp 5-13 ngy/thng.

6. Loi Vt tch, Trang thy xut hin mn 25-40, vi ngp triu t L1 - L2. Vt tr (BC) tp trung mn t 39,2 n 43,2, tn sut ngp triu l 1 -12 ngy/thng.

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7. Mm trng v Mm en phn b mn rt rng, AA phn b tp trung mn cao t 30-38,5; AO phn b nhiu mn thp t 19,8 -38; Loi AO phn b nhiu ngp t 1 - 10 ngy/thng, AA tp trung nhiu ngp L1-L3. 10. Xu Mekong phn b thch hp mn 31,3 - 35,3, ni t ngp triu t 3-22 ngy/thng. Xu sng 32,8; v thi gian ngp triu 3-16 ngy/thng. 11. Loi Gi phn b nhiu mn 30-35,8, Da nc 28,5 - 33,5, Quao nc 29. Gi phn b tn sut ngp triu t 4 - 6 ngy/thng; Quao mc ngp 6-14 ngy/thng 12. Cc trng phn b vng c mn cao 30-40, ngp triu t L3-L4. Bn trng phn b 30-40. Kin ngh Ngoi cc ch tiu v mn t, thnh thc t v tn sut ngp triu cn iu tra thm mt s ch tiu v mi trng t nh pH, thnh phn dinh dng t... tm ra cc nhn t tc ng tng hp ln s phn b ca thc vt lm c s cho vic xc nh loi cy trng ngp mn cho cc vng sinh thi khc nhau.

TI LIU THAM KHO

BUNT,J.S.,W.T.WILIAMS AND H.J. CLAY, 1982. River water salinity and the distribution of mangrove species along several rivers in North Queesland. Agust.J.Bot. 30(4):401-12. DE HAAN, J. H, 1931. Het een en ander over de Tjilatjapsche vloedbosschen. Tectona24:39-76. GROOMBRIDGE, B, 1992. Global biodiversity status of the earths living resources. World Conservation Monitoring Centre. New York: Chapman and Hall. MACNAE, S.E, 1968. A general account of fauna and flora of mangrove swamps and forests in the Indo- West Pacific region. Adv. Mar.Biol.6:73 -270. SEANGER, P., HEGERL, E.J. AND DAVIE, J.D.S, 1983.Global status of Mangrove ecosystems. IUCN Commission on Ecology Papers (3): 1-88. Bi Vit Hi, 2003. Gio trnh thng k trong lm nghip. Trng i hc Nng Lm tp H Ch Minh. Phan Nguyn Hng, Trn Vn Ba, Hong Th Sn, L Th Tr, Nguyn Hong Tr, Mai S Tun, L Xun Tun, 1997. Vai tr ca rng ngp mn Vit Nam - k thut trng v chm sc. Nh xut bn Nng nghip, H Ni. ng Trung Tn, 2000. c im sinh l sinh thi cy c. Trung tm Nghin cu v ng dng k thut rng ngp Minh Hi. Hong Vn Thi, 2004. Xc nh mt s c im cu trc rng v mi lin h gia s phn b thc vt vi mn t, ngp triu ti khu a dng sinh hc rng ngp mn C Mau. Trng i hc Cn Th. Trung tm Nghin cu H sinh thi rng ngp Mn, 1990. Nghin cu s dng hp l h sinh thi rng ngp mn Vit Nam. Trng i hc s phm H Ni I, H Ni. L c Tun, Trn Th Kiu Oanh, Ct Vn Thnh, Nguyn nh Qu, 2002. Khu d tr sinh quyn rng ngp mn Cn Gi. Nh xut bn Nng nghip - Thnh ph H Ch Minh.

Ph lc 1. Thnh phn loi cy ngp mn chnh thc ti cc nghin cu STT Loi cy Tn khoa hc Dng sng

H c Rhizophoraceae 01 c Rhizophora apiculata G 02 ng Rhizophora mucronata G 03 D vi Ceriops tagal G

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04 D qunh Ceriops decandra G

05 Vt d Bruguiera sexangula G 06 Vt tch Bruguiera parviffora G 07 Vt tr B.cylindrica(L.)Blume G 08

Trang Kandel candel G

H Mm Verbenaceae 09 Mm trng Avicennia alba G 10 Mm en Avicennia officinalis G H Xoan Meliaceae 11 Xu sng Xylocarpus moluccensis G 12 Xu M Kng Xylocarpus mekonggensis G

H Thu du Euphorbiaceae 13 Gi Excoecaria agallocha G

H Bng Combretaceae 14 Cc trng Lumnitzera racemosa G H Bn Sonneratiaceae 15 Bn trng Sonneretia alba G 16 Bn chua S.caseolalis (L.) Engler G H Cau da Arecaceae 17 Ch l Phoenix paludosa G

18 Da nc Nipa fruticans G

H inh Bignoniaceae 19

Quao nc Dolichandrone spathacea G

H r Acanthaceae 20 r trng Acanthus ebrateatus Vahl. C 21 r tm Acanthus ilicifolius L. C

H Rau trng t Aizoaceae 22 Rau sam bin Sesuvium portulacastrum Willd. C H Rng Pteridiaceae 23 Rng i Acrostichum aureum L. DX

Ph lc 2. Thnh phn loi thc vt tham gia rng ngp mn ti cc im nghin cu

STT Loi cy Tn khoa hc Dng sng H Na Annonaceae 01 Bnh bt Annona glabra L. G

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H Bng Malvaceae 02 Tra nht Hibicus tiliaceus L. G H sim Myrtaceae 03 Trm Melaleuca cajuputy L. G

H Du tm Moraceae 04 Ga Ficus microcarpa L.f.. G H Rng Pteridiaceae 05 Choi Stenocholena palustris (Burm.) DL H u Fabaceae 06 Cc kn Derris trifolia Lour. B

H Mm Verbenaceae 07 Chm gng Clerodendrum inerme Gaertn. B H Cc Asteraceae 08 Lc Pluchea indica (L.) Lees B 09 Rau mui Wedelia biflora (L.) D.C in Wight C

H Ci Cyperaceae 10 U du Cyperus elatus C

Ghi ch: G: dng cy thn g C: c DB: Cy dng bi Gn: g dng bi DX: dng x DL: Dy leo RESEARCH RELATIONSHIPS BETWEEN CHARACTERISTICS OF THE DISTRIBUTION OF MANGROVE PLANTS AND SOIL SALINITY, THE FREQUENCY AT COASTAL TIDE FLOODED RIVERS MAU Hoang Van Thoi Forest Science Sub-Institute of South Vietnam SUMMARY The study was conducted in coastal and canals in Ca Mau province, with the goal of research on plant species composition and determine the influence of environmental factors to the distribution of mangrove plant species, to there are grounds to propose scientific measures selected plant species suitable for reforestation riparian protection in a sustainable way. There are three transect surveys up perpendicular to the direction the coast, representing different types of flood tide, sea water salinity in different areas of research, investigating the species composition, collection soil sampling at 0-10cm deep and 40-50cm, then plug the tidal deposits. Results showed that study area has 33 species of 20 plant families. The true mangrove trees, including 23 species, species group with 10 species. Tree species density species occupied most Avincennia alba(AA), followed by Rhizophora apiculata(RA), the Kandelia cadel(KC), Bruguiera parviflora(BP), Sonneratia caseolalis (SC) has the lowest density is 0.1% of species. A. alba and R.apiculata species have catched the average number is 70.1% and 54.5%. R.mucronata, Ceriop tagal, S.alba, S.caseolaris, Phoenix padulosa, K.cadel Species rate appeared lowest only 1.3 to 3.9%. RA range very widely distributed, but suitable land at 30-35 salinity and tidal flooding frequency regions with high average. Ceriop decandra distributed in appropriate soil salinity range from 30 to -39, with tidal

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flooding frequency from 3-6 days per month. CT from 30-35 and distribution of flooding in many medium to medium high. BS distributed fairly concentrated in salinity from 24.5 to 32.5 and a lot of flooding in 5-13 days per month. AA distribution concentrated in high salinity from 30 to 38.5 in the flood level from L1-L3. A.officinalis distribution in many low salinity from 19.8-38 and submerged in 10-10 days per month. Keywords: Species, Mangrove, Salinity soil, Flood tide, Distribution

NGHIN CU MI LIN H GIA C TNH PHN B CA THC VT NGP MN VI MN T, TN SUT NGP TRIU TI VNG VEN SNG RCH C MAUT VN Trong : - ni l s c th ca loi th iKT QU V THO LUN

Phng trnh hi quy c thit lp gia s phn b ca loi cy RNM (Yi) v mn t (X1). Tn sut ngp triu ( X2) c m t cho tng loi cy RNM.Kt qu nghin cu khu a dng sinh hc RNM C Mau cho thy phn b ca loi gi (EA) tp trung mn t 24,2 38,3; loi da nc (NF) ch tp trung mn t 21,3 26,3 (Hong Vn Thi, 2004). Trong phm vi khu vc nghin cu th y l loi thch ng vi bin dao ng mui hp, iu c s khc bit vi nhn xt ca Phan Nguyn Hng (1990) cho rng loi gi l loi chu c bin ng ln v nng mui. Tuy nhin, theo Bunt (1982), th Excoecaria agallocha phn b ch yu pha trn ni c mn thp, E. agallocha c vng c mn thp (William and Clay, 1982). i vi loi NF trong phm v khu vc nghin cu th y l loi thch ng vi bin dao ng mui hp v l loi sinh sng mn thp nht so vi cc loi cy ngp mn khc, iu ph hp vi nhn xt ca Phan Nguyn Hng (1990) cho rng loi da nc l loi hp mui. Theo ng th y l loi cy nc l in hnh . Kin nghRhizophoraceaeH Thu duAcanthaceaeAizoaceaePteridiaceae Pteridiaceae