HQl NGHI KHOA HQC T O A N Q U Q C V E SINH THAl VA TAl N G U Y E N SINH VAT L A N THCT 5
NGHIEN ClTU HIEN TRANG VA Sy*BIEN DONG VE DIEN TICH CUA RlTNG PHONG HQ VEN BIEN P H I A B A C - V I E T NAM
v u MANH HUNG, PH^UVI VAN LU"giNG, DAM ©ITC TIEN, CAO VAN LlTCfNG Vi^n Tdi nguyen vd Mdi tru&ng Biin, Vien Hdn ldm Khoa hgc vd Cong ngh? Vi$t Nam Rirng phdng hg (RPH) ven biln dugc xay dyng v i phat trien phuc vy cho muc dich ngan cin sdng, chong sat Id, bao vg cac cdng trinh ven bien, tang dg bdi ty phu sa, md rgng dien tich bai boi ra biln, han chl xam nhap man vao ndi ddng, bio ve va phat trien ben vung nguon Igi thiiy sin. Tren thi gidi va d Vigt Nam RPH ven bien phin Idn la rirng ngap man (RNM), ngoii ra cdn cd tham thyc vat phi lao, keo lai dugc trdng tren cdn va bai cit cd tic dyng chin gid, chin cit bay. Rirng phdng hg ven biln thuc sy trd thanh "Birc tudrig xanh" bio ve tai san vi nhin din ven biln. Tuy nhien, trong thdi gian qua dien tich va chit lugng rung phdng hp ven bien suy giam nghiem trgng. Trong dd dign tich RNM suy giim Idn nhat. Sy bien dgng cua RNM cd inh hudng idn doi vdi bien dgng RPH ven bien. Ngoii ra, RNM cdn li khu h?
sinh thii cd tr& Iugng sinh hgc Idn, dem lgi ngudn Igi thuy sin to Idn cho ngudi din, gdp phan binh dn kinh te, xa hgi vimg ven bien.
I. DOI TU*gfNG, MVC DICH VA PHU'aNG PHAP NGHIEN ClTU 1. fioi tuong nghiSn cmi
Ddi tugng nghien ciru Ii rimg RPH ven bien, tap trung vio thim thuc vat d nh&ng viing mang tinh chat xung yeu phia Bic Vigt Nam.
Hinh I. Bdn do khu v^rc nghien cuu
HQI NGHI KHOA HQC T Q A N Q U O C V £ SINH T H A I V A T A I N G U Y £ N SINH VAT L A N THO' 5 2. Muc dich Dghieu cuu
Nghien cuu thanh phin loai v i su bien ddng ve dien tich cua hg thdng RPH ven biln phia Bic Viet Nam
3.Fbuang phap nghien cihi
Dieu tra v i quan sat thuc dia, nhim kilm tra va dieu chinh hoac cap nhit nhung vin dl da dugc phat hien trong qua trinh phan tich bg tu lieu hien cd, cu thi:
* Phirang phdp xdc dinh thdnh phan lodi cay
Phuang phip niy dya vio tai lieu: Vo Van Chi vi Duong Due Tiln (1978), Wim Giesen vd cs. (2006):
+ Xac dinh ting tin ciy bing each do chieu cao cua cic ting cay bing thudc do (5m).
+ Xic dinh vj tri khio sit, ranh gidi tham thuc vit ngap man bing thilt bj dinh vj vg tinh Mobile Mapper 6 vi xiy dyng ban dd phan bd cua RPH ven biln theo mdc thdi gian: 1990, 2000,2008 bing ky thugt vien thim.
Thiet lap bdn do- Bin dd chuyen dh dugc giii doan tir inh ve tinh vi xay dung tren ca sd ban do dia hinh ty le 1: 50.000. Ludi chieu UTM, he tga do, do cao: Nha nude VN 2000, NXB Ban dd, nim 2004.
* Phirang phdp quan sdt khdch quan va ddnh gid chuyen gia
Dua tren kit qui dieu tra thyc tl va sd lieu thu thap dugc tir tii lieu tham khio dya theo Phan Nguyen Hdng (2003).
II. KET QUA NGHIEN ClTU
\. Dien tich rung phdng hg ven bien /./. Hien trang phan bo vd dien tich
Theo ket qua nghien ciru thuc te cho thiy rung phdng hp ven bien phia Bic chii yeii la rung ngap man, chinh vi vay nen phan bd tap trung d khu vuc cac cira cic song ldn nhu: KaLong, Tien Yen, Bgch Dang, Vin Uc, Thii Binh, Hdng, Day thudc khu vyc bai trieu ven bien phia Bac. Bang ky thuat vien thim chiing toi da xac djnh dugc dien tich RPH ven bien phia Bac phin bo tai cic tinh nhu sau:
Bdng 1
TT
1 2
Dien tich ptian
~ ^ „ I 3 i f n tich (ha) D6i tifp-ng rong ~^-..„^^^
Rirng ng^p m^n Phi lao ven bien T6ng cpng
bo rirng pliong ho phia Bac nam 2008 Quang
Ninh 21,397,03
160.01 21.457,04
Hal Phong 2 345.36
41.12 2.386,48
Thai Binh 2.139.45
109.24 2.248,69
Nam Djnh 2.229.81
108.18 2.337,99
Ninh Binh 366.49
0.00 366,49 Qua sd Ii?u bang 1 cho thiy Quing Ninh li tinh cd dien tich RPH ven bien ldn nhat, trong do RNM chilm phan Idn yi cung Ii khu vuc cd di?n tich RNM ldn nhit trong khu vyc. Do Quing Ninh la tinh cd chieu dii ven bien Idn nhat khu vyc phia Bic lai dugc che chin bdi he thdng dao di vdi phia ngoii nen tgo dieu kien cho RNM phat trien. Tiep theo do la khu vuc
HQI NGHI KHOA HQC T O A N Q U Q C V £ SINH T H A I VA TAI N G U Y £ N SINH VAT L A N THU' 5 Hai Phdng, Thii Binh v i Nam Djnh. Diy la ba tinh thudc luu vyc sdng Hdng vdi luu Iugng phii sa do ra biln hang nim rat Idn. Chinh vi vky, khu vyc nay cd di?n tich bii trieu rgng, tgo dilu ki?n cho nhilu loii cay ngap man phat trien. Qua bang 1 cho thiy d ca 3 tinh tren thi di?n tich RNM chilm sd lugng chii yeu diSn tich RPH ven biln trong khu vyc. Trong dd khu vyc Hai Phdng RNM tgp trung nhilu d khu vyc ciia Bgch Ding, ciia Van Uc; khu vyc Thai Binh tap trung d khu vyc Thai Thyy va Tien Hii; khu vyc Nam Djnh tgp trung nhieu d khu vyc Giao Thiiy, Giao Xuan, NghTa Hung. Tinh cd di?n tich RPH nhd nhit d khu vyc phia Bic li Ninh Binh. Day la vimg cd tde dg boi tu nhanh nhit vung chau tho sdng Hong. Qua trinh hinh thinh bai bdi tiln ra biln phat triln lien tyc. Diy li dieu ki?n thuan Igi cho cay ngap m5n phit triln. Nhung do viec dip de lan biln diln ra qui nhanh gay anh hudng Idn den tham thyrc vat ngap man trong khu vyc. Dii Phi lao {Casuarina equysetifolia) phan bd d khu vyc ven biln Ninh Binh rit it, rii ric ven khu vyc din cu, nen khdng dii dieu kien hinh thanh RPH ven biln (Nguyen Nggc Binh, 2006).
1.2. Bien dpng ve dien tich cua he thong RPH
Cic hogt dgng ciia con ngudi nhu chat cay lam gd, phi rimg lim dim nuoi thiiy sin hay cac cdng trinh ven bien (cau cing, khu cdng nghiep) va cic boat dgng phit trien dd thi da va dang tilp tyc lam suy giim dien tich rung phdng hg ven bien. Mac du, nhi nude da cd che tii ch|t che va chuang trinh trdng phuc hdi cic khu rirng phdng hg. Nhung ket qua thyc te nghien ciru cho thiy dien tich rirng ngap man vin dang giim (hinh 2).
0.00
Di$n tich RNM Diln tich Phi lao
^ Rifng ng^p mgn
Hinh 2. Bien dgng di?n tich rung phdng hg ven bien phia Bdc
Qua ket qui hinh 2 cho thiy dien tich r&ng ngap man cd su suy giim rat nhanh chi trong vdng 10 nam (1990-2000), dien tich rirng ngap man trong khu vyc da suy giim 5.632,89havi dien tich niy tilp tuc suy giim vio 8 nam tilp (2000-2008) vdi didn tich suy giim la 7.588,2ha ldn han ciia 10 nim trudc. Kit qui niy cho thiy di?n tich rirng ngap man vin dang cd nguy ca suy giam vl dien tich rit ldn trong nh&ng nam gin day. Mac dii dugc quan tim va cd nhieu chuang trinh giiip phuc hdi va bao ve cac khu vyc rirng nggp man.
HQI NGHI KHOA HQC T O A N Q U Q C V £ SINH T H A I VA T A I N G U Y £ N SINH VAT L A N THlJ 5
Cung qua hinh 2 cho thay dien tich rimg phi lao trong khu vyc ciing ed nhung biln ddng diaig kl. Trong nh&ng nam 1990-2000 dien tich rirng phi lao trong vimg hiu nhu khdng thay ddi nhung chi trongvdng cd 8 nim sau dd (2000-2008) dien tich rimg phi lao cd nh&ng biln ddng Idn theo hudng giam di khoing 528,98ha.
1.3. Plian tich nguyen nhdn cda sir bien dgng dien tich
Qua qua trinh khio sat va nghien cuu nhdm tic gii da danh gii va ghi nhan mgt sd nguyen nhan bien dgng di^n tich rimg phdng hg ven bien phia Bic nhu sau:
- Su phit triln thilu quy hoach cic dy in nudi trdng thiiy sin: Day la nguyen nhin chinh gay suy giam dien tich r&ng phdng hg ven biln phia Bic. Dac biet li rirng ngap man trong khu vyc, vdi su phit trien cua viec phi rung lam dim torn da lam cho hing ngan hecta rimg ngap man bj phi v i chuyen ddi thinh dam nuoi thiiy sin.
- Qui trinh do thi hoi: Su bung phit ve dan sd vi nhu cau xay dung nha d ciia mgt sd thanh phd ven bien da gay inh hudng khdng nhd den dien tich rirng phdng hd ven biln nhu sy phat trien khu vuc Cai Dim (Quang Ninh) da lim mat di dien tich rirng ngap man phan bd d khu vyc nay.
- Xay dyng cau cang venbien: Viec xay dung cing bien khu vyc ven bien phi'a Bic dien ra rat manh. Nhung dy in nay can cd dien tich xiy dyng rat ldn d ven biln. Chinh vi vgy khi phit trien cic dy in nay giy inh hudng Idn din dien tich rimg phdng hg ven biln. Nhu sy phit triln cang Hai Phdng, cac khu vuc dong tau da lam mat di dien tich Idn rirng ngap man va rirng phi lao ven biln. Ngoii ra, mgt sd du in xay dyng cing khic nhu d khu vyc cira sdng Diy dang cd ke hoach thyc hien. Vi vay, nhung dy in nay can cd su quy hoach phii hgp dl khdng lim inh hudng ldn den dien tich rirng phdng hg ven bien.
- Qui trinh lin bien: Day la qua trinh tat ylu vi da cd tu rit lau ddi. Nhung viec quy hoach va lan bien dien ra nhanh lim anh hudng den su phan bd ciing nhu dien tich rirng phdng hg ven bien, nhu vi?c phit trien cic du an xay dyng tuyen de lan bien d Kim San (Ninh Binh); Dinh Vu (Hai Phong).
2. Thanh phan loai cay rirng phong ho ven bien
Qua ket qui nhieu dgt khao sit thuc te va dgt khio sat toan bg khu vuc ven bien phia Bac chung tdi di xic dinh dugc thinh phan loai phan bd d khu vyc rirng phdng hg ven bien la 31.
Ioai thuc vat thudc 29 chi, 22 hg va 2 nganh (Duong xi va Hat kin) (bang 2). Nhung theo thdng ke ciia Le Thi Thanh (2009) dya theo danh muc cac loai thyc vat rirng ngap man Viet Nam ciia Phan Nguyen Hdng (1994) thi khu vuc ven bien Quang Ninh cd3I loai thyc vit rimg ngap man.
Doi chieu ket qui thiy cd su sai khic ve cic loai bdi tic gii cd dua them mgt sd loii ciy gia nhap CO mat tai khu vyc rung ngap man nhu: Cd nan {Eleocharis diilsis (Burm.f.) Hensel), Ca gai leo {Solanum procuinbens Lour.).
Thanh phan loai thuc vat rung ngap man khu vyc ciia Thii Binh da cd nhieu tac gia nghien ciru vdi sd loii ghi nhan dugc khac nhau nhu: Mai Sy Tuan (2008) ghi nhin d khu vuc Tien Hai CO 181 Ioai, trong dd 11 loai cay ngap man chii yeu, 37 loai cay tham gia ngap man va 133 loai cay ngi dja di cu ra; Le Thi Thanh (2009) tdng hgp khu vyc Thai Binh cd 36 loai trong dd 12 loai cay ngap m^n chii ylu, 14 loii cay tham gia va 10 loai cay noi dia di cu ra. Cd sy khac bi?t ve sd lugng thanh phan loai cay phan bd d khu vuc nay la do quan diem ciia tirng tac gii. Cd tac gia dua toan bg Ioai cay cd mat trong khu vyc vao danh muc, nhung cd tic gii lgi chi dua nhung loai ciy cd mat d trong va ven thim thuc vat ngap man. Ddi chieu vdi ket qua tren chiing tdi nhgn thay ve thanh phin loii ciy tuy sd lugng loai cd khac nhau nhung ve co ban thi thanh phan Ioai cay trong nhdm cay ngap man chinh thuc khdng khac nhau ldn.
1375
HOI NGHI KHOA HQC T O A N Q U Q C V £ SINH THAI VA TAI N G U Y E N SINH VAT LAN THCr 5
Jang 2 Thanh phan loai cay rimg phdng ho ven bien phia Bic
TT loai 1
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
Ten khoa hgc Tenhg (Vi^t Nam) PHYLUM 1. P O Y P H O D O P H Y T A Reridaceae | Hg Rang seo g i PHYLUM 2 ANGLOSPERMAE Class 1- Dicotyledoneae Ancanthaceae Aizoaceae Asteracea Convolvulaceae Euphorbiaceae Fabaceae Malvaceae Myrsinaceae Avicenniaceae Portulacaceae Rhizophoraceae
Solanaceae Sonneratiaceae Combretaceae Vertjenaceae
Apocynaceae Goodeniaceae Pandanaceae Annonaceae Casuarinaceae
HgQro Rau ding dat CCic Ho Bim bim TTiaudau HgDgu Hp Bong Hp Dan nem Ho Mam Ho Rau sam Hp Duoc
HoCa HgBan Ho Bang Ho Cd roi ngga
Hp TnJc dao HpHep Hp DiKa dgi HpNa Hp Phi lao Class 2, Monocotyledoneae
28 29 30 31
Amaiyllidaceae Cyperaceae
Hg Thuy tien Hgcdi
Ten khoa hgc N G A N H DU'ONG Xl Acmstichum aureum L.
NGANH HAT KIN Ldp 1. Hai l i mim Ancanthus ebracteatus Vahl.
Sesuvium portulacastrum L.
Wedefia bifora (L.) DC ipomoea pes-caprea (L.J R. Br. Roth.
Excoecaiia agallocha L.
Denis tripfoliata (Benth) Barker Hibiscus tiliaceus L Thespesia populnea (L.) Soland Aegiceras corrvculatum (I.) Blanco Avicennia lanata Ridley Avicennia marine Potulaca oleracea L. Sam.
Bruguirea gymnorrhiza (L.) Kandelia obovata L. Daice Rhizophora stylosa Giff Datura metel L.
Solanum procumbens Lour.
Sonneratia caseolans L Lumnitzera racemosa Willd.
Clerodendmm inerme L. Graertn Lantana camara L Cerbera manghas L.
Scaevola taccada (Gaertn.) Roxb.
Pandanus tectonus Sol.
Annona glabra L.
Casuarina equyseUfolia Forst &
Forst Ldp 2. Mpt la mam Crinum aslaticum L Cypems rotundus L.
Cyperus stoloniferus Retz Eleocharis dulsis (Bumi.f.) Hensel
Ten Vift Nam
Rang bien
0 ro bien Sam biln Sai dat bgi Muong bien Gia Cdc ken Tra lam chieu Tra lam vo Su Mam quan Mim bien Rau sam Vetdii Trang Oudc vol C i dgc dugc Ca gai leo Ban chua, Liu Cdc vang,c6c trang Nggc nu" bi4n, Vgng hdi Ngu sac, tham 6i Mudp xac Hep Dua d?i Na bien Phi lao
Nang Cd cu, Cd giu Cd gau bien Cdnan
Logi cay
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+ Ghi chii: *: Cay ngip mgn chinh thuc.+: Cay tham gia rung ngSp mgn.
HQI NGHI KHOA HQC T O A N Q U O C V E SINH T H A I V A T A I NGUYEN SINH VAT L A N THO' 5 3. c i u true phan ting trong rimg phdng hg ven bien phia Bic
He thdng rung Phi lao (C. equysetifolia Forst) 8-1.0 nim tudi phan bd tren bai cit thudng cd chilu cao tren 4-8m.
Trong h? thong rimg ngap man sy phan tang thudng dien ra nhu sau:
- d dg cao 4-8m chii yeu la Ban (5. caseolaris) tip trung phin bd thanh dai dgc theo cac con sdng, lach trong rung ngap man, hay phin bd rai ric xen trong quan xa Trang {K. obovata) trong 4-10 tudi.
- 0 do cao 2-4m: Diy la tang cay chinh d khu vyc vdi nhieu toai phin bd d ting ciy niy nhu: Dude {K stylosa), Mam bien {A. marina), Trang {K. obovata). Vet dii {Bruguirea gymnorrhiza),...
- CJ dg cao l-2m: Ting cay nay cung chilm thj phan kha Idn vdi sy phan bd ciia mdt sd loii cay nggp man chinh nhu Dude, Cdc ving, Sii, Trang trong cac sinh cinh ty nhien.
- CJ do cao dudi 1 m: Ting cay niy thudng phin bd dudi tin cay ngap man, dd li nhGng cay con tii sinh, Ring va mdt sd loii cd.
IIL KET LUAN
Rirng phdng hg ven bien phia Bac chii yeu li rung ngap man va phan Idn dien tich tip trung d tinh Quing Ninh.
Di thdng ke dugc trong he thdng rung phdng hd ven bien d khu vyc nghien cuu cd 31 Ioai thuc vgt thugc 29 chi, 22 hg va 2 nginh (Duong xi va Hat kin).
Trong nhung nim gin diy, dien tich rung phdng hd ven bien, dac biet la rung ngap mgn bj suy giam rat manh chu yeu la do phi rirng de nudi trdng thuy hii sin.
TAI LIEU THAM KHAO
1. Nguyen Tien Bin, 1997. Cam nang tra ciiu va nhin bilt cic hp Ihuc vat hat kin d Viet Nam. NXB.
Ndng nghiep. Hi Npi. 532 trang.
2. Nguyen Ngpc Binh, 2006. Chuang 111. Cam nang nganh lam nghiep. Bg Nong nghi?p va PTNT, 72 trang.
3. VS van Chi vi Duo-ng Due Tien, 1978. Phan logi hpc thyc vat bac cao. NXB. Khoa hoc va Ky thugt. Hi Noi. 549 trang.
4. Phan Nguyen H^ng, 1991. Sinh thii tham thyc vat ngap man Viel Nam. Luan an Tien sT Khoa hpc Sinh hpc. Trudng Dgi hgc Su pham Ha Npi. 336 trang.
5. Phan Nguyen Hong, 2003. Phuang phap dilu tra rirng ngap m3n. S6 tay huong dan dilu Ira va giam sat da dang sinh hpc. NXB. Ndng nghiep. Ha Npi. 422 trang.
6. WimCicscn, Stephan Wclffraat, Max Zicrcn and Liesbth Sholten, 2006. "Mangrove guidebook for Southeast Asia". FAO and Wetlands International 769 p (2006).
7. Le Thi Thanh, 2009. Thu thap vi danh gii cac ngudn tu lieu da co ve quan xi thirc vat ngap m3n ven bd phia Bic, tap Irung d tinh Thai Binh-Bao cao chuyen dl de tai. Danh gia miic dg suy thoai cac h? sinh th^i ven bd bien Viet Nam va de xuat cac giai phap quan ly ben vung, 36 tr.
8. Mai Sy Tuan, Phan H6ng Anh, 2008. Tham thuc vat viing rimg ngap ni3n thuoc Khu Bao ton thien nhien dap ngap nude Tien Hai, Thai Binh. Tuyen tap Phuc hdi rirng ngSp man irng pho voi biln doi khi hgu hudng tdi phat triln bin vung. NXB. Ndng nghiep, 305-319. 389 tr.
HQI NGHI KHOA HQC T O A N Q U Q C V £ SINH T H A I V A TAI N G U Y £ N SINH VAT L A N T H l j 5 STUDY ON STATUS AND CHANGE OF THE AREA OF THE COASTAL PROTECTION FOREST
IN THE NORTH OF VIETNAM
VU MANH HUNG, PHAM VAN LUONG, DAM DUC TIEN, CAO VAN LUONG SUMMARY
Coastal protection forests are established and developed for the purpose of waves preven^ng, erosion controling, coastal alluvial deposits preventing, expanding the area of see mud flat, limiting the saltwater infiltration into the rice field, fisheries resources protecting and sustainable developing.
Coastal protection forests in the North of Vietnam concentrated mainly in the large estuanes. Quang Nmh province has the largest area of coastal protection forests in the region. The area of coastal protection forests has declined during last decades. The area of mangrove forest declined rapidly, in just 10 years (1990-2000) the loss amounted to 5.632.89ha, and in the next 8 years (2000-2008) the loss was 7,588 2ha- The loss of Casuarina forest in 10 years (1990-2000) was 3,2 hectares, but in last 8 years (2000-2008) it amounted to 52a.98ha. There are several layers in coastal protection forests: 400-800cin, 200-400cm, 100-200cm and below 100cm. The layer 200-400cm is dominated by tree species
