HQI NGHI KHOA HOC T O 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 THCf 5
PHAN LOAI THAM THlTC VAT TlT >fHIEN VA NGUYEN NHAN GAY SUY THOAI RlTNG
d HUYEN VI XUYEN, TINH HA GIANG
DOKHACHtJNG Trudng Cao ddng Suphgm Hd Giang LE NGQC CONG Tntang Dgi hgc Suphgm, Dgi hgc Thdi Nguyin Vj Xuyen Id huyen vimg thdp ciia tinh Ha Giang, cd tdng dien tfch dat tu nhi6n Id HS.lOOha, dien tich rimg Id 102.072,06ha (chilm 67,5%) trong dd cd 26.139,8ha riJmg dac dvng. Do dja hinh hilm trd va cd Ban Quan ly rimg dgc dung rieng nfin mpt so nai cdn giir dugc d$c dilm nguyen sinh ciia rung vd cd thdnh phdn thuc vat rat da dang va phong phii.
Dan so huy?nVi Xuyen cd96.168 ngudi vdi 15 dan tgc cimg sinh sdng, trongdd ngudi Tay chiem ty 1? cao nhat (36,1%), sau dd Id ngudi Dao 22,9%, ngudi Kinh 15,2%, ngudi Mdng 11,0%, ngudi Niing 7,8%, cdn lai Id cdc dan tgc khde... Vdi hoat dpng sdn xuat va khai thdc tdi ngin'Sn rimg truyen thdng nhu chat phd riJrng, ddt, lay dat Idm nuong rdy, Idm nai chan tha... nen nhieu dien tich rirng bj thu hpp, nhieu lodi cay cd gid trj kinh te cao nhu: Nghien, po mu, dinh...
(H bj khai thdc kiet que va tham th^rc v^t rirng bj suy thoai rdt nghiem trpng. Trong bai bao nay chiing tdi trinh bdy kit qud nghien cuu phdn loai tham th^rc v^t tu nhien va tim hieu nhirng nguyen nhdn chinh gdy ra suy thodi rimg d dia phuong. Ket qud thu dugc gdp phdn vdo viec quan ly, bdo vp ngudn tai nguyen rimg d huyen Vi Xuyen, tinh Ha Giang.
I. PHtrONG PHAP NGHIEN CUtJ
Thu thdp so lipu ngodi thyc dja dugc thuc hien theo phuong phdp tuyen dieu tra va d tieu chuan. D\ra vao bdn dd thdm thuc vat ciia tinh, thiet lap cdc tuyen dieu tra di qua tdt cd kieu thdm thyc vdt trong khu virc. Tren tuyen dieu tra lap 30 d lieu chudn lam thdi cd kich thudc 5Dm X 50m, dl dieu tra thu thap sd lieu ve thanh phdn Iodi va cau triic Iham thuc val. Thu thap sd lieu theo cdc phuang phdp thdng thudng dang dugc su dung trong nghien cuu sinh thdi hgc vd Idm hpc hi?n nay.
Sir dung phuang phdp ciia Thdi Van Triing (1970) de md td cdu triic ciia thdm thuc vat. Ten cdc Ioai cdy dugc xdc djnh theo Danh lyc cac lodi thuc vdt Viet Nam tap 1, 2, 3 (2003-2005). Su dyng khung phan loai ciia UNESCO (1973) dk phdn loai thdm thuc vdt.
n. KfeT QUA NGHIEN CtTU
1. Phan loai cdc kieu tham thuc vat d huyen Vi Xuyen
Theo khung phdn lo^i cua UNESCO (1973), thdm thuc vdt huyen Vi Xuyen cd 4 Idp quan h?: Rimg kin, rimg thua, thdm cay bui va Iham cd vdi cac quan he nhu sau:
I. Ldfp quan he rirng kin (Closed forest)
IA.LL Quan hg rirng kin thirdng xanh mua miia & dia hinh thap vd nui thap LA. 1.1.1. Phdn qudn h? cdy Id rgng. Trong phan quan h? ndy thudng gap mot sd trang Ihdi
• ^ g nhu sau.
HQl NGHj KHOA HQC T O A N Q U Q C V £ SINH T H A I V A T A I N G U Y E N SINH VAT L A N THLf 5
* Trang thai rimg ttr nhien it bj tde ddng cd mat hau hit dai dipn ciia cdc hg thuc vat nhi?t dm Viet Nam nhu: Trdm trdng {Canarium album), Gdi bdng sung {Aglaia gigantea). Bdi ldi nhot {Lilsea gluiinosa), Rdng rang mit {Ormosia balansae), Ngdt {Gironniera subaequalis), Mudng lac {Cassia alala), Gidi Idng (Michelia balansae). My {Lysidice rhodostegia). De gai {Caslanopsis indica), Bua {Garcinia oblongifolia). Mau chd Id nhd {Knema coslicosa), Trdm me gd {Slerculia lanceolala)... Kieu rirng nay da bj khai thdc mdt sd lodi cay gd quy hiem nhung ca ban van giii dugc tinh nguyen sinh cua rimg. Kieu rimg nay chi gap d hai xa Cao Bd vd Thanh Thuy.
* Trang thai riing thu sinh phuc hoi sau khai thdc: Kieu rirng nay cdn khdng nhieu, phan bo d Thanh ThCty vd Cao Bd. Do bj ldc ddng manh qua khai thdc chgn Idy di nhiing cay gd ldn, go tdt va quy hiem nen trong lam phdn chi cdn lai nhirng cdy gd chat lugng kem nhu Ngdt {Gironniera subaequalis), Da bdng (Ficus championi). Rang rang mit {Ormosia balansae), Ldi thp {Gmelina arborea), Vdng anh (Saraca dives)...
* Trang thai rirng thu sinh phuc hdi sau nuong rdy: Ki^u rirng nay tap trung chu yeu gan cdc lang bdn, cdc khu rirng dugc hinh thanh sau canh tac nuong rdy tai cdc xd Thanh ThuJ, Cao Bd, Quang Ngan. Thanh phdn thuc vdt chii yeu Id cdc cdy lien phong ua sang, sinh irtidng nhanh nhu: Hu day {Trema orentalis). Mdng lang {Lilsea cubeba), Ldng mang fPlerospermwIi iruncaiolobalum), Bd de {Styrax tonkinensis), Co ke {Microcos paniculala), Sdi tia {Sapium discolor). Bdi ldi giay {Lilsea monopetala). Tram trang {Canarium album) vd mgt sd loai Nih {Neohouzena dulloa) mpc xen ke.
LA.I.2. Quan hi rieng nhiet d&i thudng xanh mica miia a niii trung binh
I.A.1.2.1. Phdn qudn he cdy Id rgng. Trong phdn qudn he ndy cd gap mgt sd trang thai rimg nhu sau:
* Trang thdi rung nguyen sinh la kieu rirng tuy cd tde dgng nhimg khdng ddng ke, con giif dugc linh nguyen sinh co bdn. Kieu rimg ndy gap d cdc xa Phuang Tien, Phucmg Dp, Cao Bo, Qudng Ngan, Lao Chai. Thdnh phdn thuc vdt chu yeu vdn la cac loai thuc v^t nhiet ddi nhu: Ul hoa {Chukrasia tabularis), Lat khet {Toona surenii). Tram trdng {Canarium album), Vang {Endospermum sinensis), Gdi nude hoa to {Aphanamixis grandifolia). De gai {Caslanopsis indica). Sdi qud del {Quercus helferiana), Sdi tay {Quercus fleuryi), Bdi ldi nhdt {Litsea gluiinosa), Tram den {Canarium Iramdenum), Hodng linh bac bg {Peltophorum tonkinensis), Rdng rdng xanh {Ormosia pinnata), Cheo {Engelhardtia chrysolepis), Cdng Id {Betula alnoides), Pa mu {Fokienia hodginsii)...
* Trang thai rirng thu sinh phuc hoi sau khai thae: Do bj khai thdc chgn vdi cudng dp manh nen trong Idm phan chi cdn lai nhirng cay gd chat lugng kem nhu Ngdt {Gironniera subaequalis). Rang rang mit {Ormosia balansae)... Dac biet d nhii'ng noi cd dp cao tu I600ni trd len van cdn nhiing cay Po mu {Fokiennia hodginsii) cd dudng ki'nh khodng 12-15cm.
* Trang thai rirng thir sinh phuc hdi sau nuong ray: Phdn bo d tat ca cdc xS Cao B6, Thanh Diirc, Minh Tan, Thanh Thuy. Ddt ngheo kift, dd bj bd hoang nhieu ndm. Cay cd chieu cao trung binh 10-I2m, dudng kinh dudi 15cm. Cdc lodi chilm uu thi Id Bd dl {Styrax tonkinensis), Mang tang {Lilsea cubeba), Hu day {Trema orientalis), Thdi ba {Alangium chinenses), Trin {Schima walUchii). Tdng qua su {Alnus nepalensis). Rang rang mit {Ormosia balansae), Ch?o trdng {Engelhardtia spicata)... Dudi tan rimg da xudt hl?n cay tai sinh ciia cac loai gd t6t nhU Chd chi {Parashorea chinensis), Gii huong {Cinnamomum balansae)...
HQI NGHj KHOA HQC TOAN QUOC Vg SINH THAI VA TAI NGUYEN SINH VAT LAN THC 5
IA.1.3. Quan he ritng nhigt ddi thudng xanh nura mua tren nui da vol J.A.I.3.1. Phdn qudn h$ cdy Id rgng
Kilu rimg nay phdn bd tai xa Thanh Thuy, Lao Chai, Sin Chai, Minh Tan. Ddy la kieu rimg dac bif t phdt triln tren ddt do da vdi phong hda vdi nhung loai cay cd chdt lugng gd rdt tdt va thudng sinh trudng rat ch^m nhu: Nghien {Excentrodendron tokinense). Chd ndu {Dipterocarpus tonkinensis), Chd chi {Parashorea chinensis), Trai {Garcinia fagraeoides), Ldt hoa {Chukrasia tabularis). Lat khet {Toona sureni)...
IA.1.4' Quan hi rirng tre, nira (Bambusoidae) I.A.I.4.I. Phdn qudn h? rimg tre nira mgc thudn lodi
Kilu rimg nay g^p d cdc xa Cao Bd, Quang Ngan, cd ngudn gdc tir kieu rirng la rdng thudng xanh, song do sir phd rirng bira bai va hoat dpng canh tac nuong rdy ddn tdi nhiing cay g6 khdng cdn, t?o dilu kipn cho tre, mia phdt trien, chimg thudng phdn bd d dp cao dudi 1000m. Loai Vau la map {Indosasa crassiflora) chiem uu the, chiing mpc tdn vd thuan loai thanh timg dam rpng, nhu'ng noi l|ip dja cdn tdt, cd dp ddc trung binh va thdp xudt hien lodi Niia {Neohuzeana dullosa), Tre gai {Bambusa spinosa), Hdp {Bambusa multiplex), Giang {Ampelocalamus patellaris). Tren ddt bdi tu ven sudi viing thap cd loai Dien trung {Dendrocalamus latiflorus), Tre vdng spc {Bambusa vulgaris var. striata).
I.A.I.4.2. Phdn qudn hg rimg tre nua mgc xen val cdy Id rgng
Kilu rimg ndy gap d cdc xd Thanh Thuy, Thanh Due, Phuang Tien, Phuong Dp, Cao Bd va Quang Ngan, cd ngudn gdc tir kieu rirng Id rgng thudng xanh nhiet ddi dm, song do sir khai Ihac kift va hoat ddng canh tac nuang rdy thieu kiem sodt.
Kilu rirng nay cd cau triic 2 tang rd ret: Cdy gd tang tren va tre nira tang dudi. Tdng tdn cay g6 khong lien tyc, dien hinh Id cdc lodi Tram trdng {Syzygium wighlianum), Trdm trang {Canarium album), Gidi ba {Michelia balansae), Gidi la lang {Michelia foveolala). Ldi thp {Gmelina arborea), Dung cd ranh {Symplocos yunnaensis), Ngat {Gironniera subbaequalis).
Rang rdng xanh {Ormosia pinnata). Trin {Schima wallichii), Vang {Endospermum chinensis)...
Tang dudi la tre nira chii yeu la Vau la mgp {Indosasa crassiflora), Niia {Neohuzeana dullosa), Tre gai {Bambusa spinosa). Hdp {Bambusa multiplex). Giang {Ampelocalamus patellaris).
IA.1.S. Quan he rung cay Id kim
l.A.1.5.1. Phdn qudn he rimg hdn giao cdy Id kim vdi cdy Id rgng tren niii cao Kieu rirng ndy phdn bd d dp cao lir 1800m trd len, thugc cdc xa Lao Chai, Phuang Tien vdi cdc dai dien diln hinh nhu Gioi bd {Michelia balansae), Kim giao {Nageia fleuryi). Thdng tre {Podocarpus neriifolirus). Pa mu {Fokienia hodginsii). Hodng ddn {Cupressus torulosa). Thdng ba la {Pinus kesyia). Sdi ghe {Lilhocarpus corneus)... Nhin chung kieu rirng nay cdn giii dugc tinh nguyen sinh, song mdt sd cdy go quy hilm cd sd lugng cd the rat it, hoac chi cdn lai nhiing cay CO dudng kinh nho.
n. Ldp quan he rung thua (Wood land)
U.A.1.L Quan he rung thua thir&ngxanh cay la rgng a ddt thap vd nui thdp Trong khu virc thi kieu rirng ndy chilm uu thi duoc phan bd d hdu hel cac xa trong huyen.
Do la cac rirng thir sinh phuc hdi sau nuang ray bd hoa. Kieu rirng ndy cd cau true 2 tdng nhung phdn hda khdng rd ret. Tdng cay gd cd thanh phan Ioai gdn gidng nhu kieu rirng kin Ihudng
HQl NGHI KHOA HQC T O A N Q U Q C V £ SINH T H A I V A T A I N G U Y E N SINH VAT L A N THO" 5
xanh mua miia nhi?t ddi, vdi cdc cay cd dudng kinh trung binh 8-IOcm vd dp tan che 0,5-0,6.
Cdc lodi cdy thir sinh uu the Id: Biim bup {Mallotus paniculala), Man dia {Archidenc clypearia), Rdng rang {Ormosia balansae), Cheo {Engelhardtia roxburghiana), De {Caslanopsis indica), Sdi la trdn (Sapium rolundifolium), Thdnh nganh {Cratoxylum cochinchinnense), Hu day {Trema orientalis)... Dudi tdng cdy gd la cdy byi, cdy con tai sinh va tham tuai thua nhu: Mang tang {Litsea cubeba), Thdu tdu (Aporosa dioica), Hu day (Trema orientalis). Co giing (Panicum repens) vd mgt sd cay hg Ray (Araceae)...
II.A.1.2. Quan he rirng tre nu-a
Quan he nay hinh thdnh sau khi rimg nguyen sinh bj khai thdc kiet va nuong ray bj bo hoi Chiing mgc xen vdi cdy gd Id rgng tao thanh rimg hdn giao ho^ic mgc thdnh rimg thuan lo^i nhung do tdn che cdn thdp (0,4).
II.A.1.2.1. Phdn qudn hi rimg tre, mia mgc xen vdi cdy go la rdng
Kieu rimg Nura {Neohouzena dulloa), rirng Vdu {Phyllostachis sp.^ mgc hdn giao vdi c i c l cay gd la rdng nhu: Ddm {Bridelia balansae), Hu day {Trema orientalis), Thdi ba {Alangium chinense). Mang tang {Lilsea cubeba)... Loai hinh ndy phdn bd d hau het cac xa cua huyen Vj Xuyen nhu: Dao Diic, Bach Nggc, Tung Ba, Thuan Hod, Kim Linh, Nggc Linh, Linh Hd, Ngpc Minh, Trung Thanh, Thugng Scm, Xin Chdi...
II.A. 1.2.2. Phdn qudn he rimg tre, mia mgc thudn logi
Loai hinh ndy gap rdi rdc d cdc xa nhu: Lao Chdi, Xin Chai, Phd Linh, Thugng San, Minh Tan, Trung Thanh, Ngpc Linh, Nggc Minh, Qudng Ngan, Linh Hd, Kim Linh, Thudn Hod.
n.A.1.3. Quan hi ritng thira cdy Id rgng rung Id & dat ihap vd mii thap
Cac qudn xa thugc qudn he nay ryng la ve miia khd. Thai gian ryng la tir thang 12 ndm trudc den thdng 2 nam sau. Day la qudn xa rimg phuc hdi sau nuang ray vdi cdc loai uu the 14:
Thdnh nganh {Cratoxylum cochinchinense), Bd d l (Styrax tonkinensis), Sau sau {Liquydamba formosana). cd d cac xa Dao Dirc, Phuong Tiln, Trung Thdnh, thj trdn Viet Lam, Vj Xuyen...
UI. Ldp quan he cay bui (Scrub)
HLA. 1.1. Quan hg cdy bui thu-dng xanh tren ddt kho III.A. 1.1.1. Phdn qudn hg cdy bgi co cdy go mgc rdi rdc
Kieu thdm nay gap d hau het cac xa trong huyen Vj Xuyen, trSn ddt sau nuong rdy bd hoa.
Dd Id nhirng qudn xa vdi cdc loai uu the nhu: Bum bup {Mallotus paniculala), Dom dom {Alchornea tiliaefoUa), Thanh nganh {Cratoxylum cochinchinense), Thau tau {Aporosa sphaerosperma). Me rimg {Phyllanthus emblica)..., cac cay gd mpc rai rdc chu yeu Id cdc lo^i cdy tien phong ua sang, sinh trudng nhanh nhu: Hu day {Trema orientalis), Ba soi {Macaranga J
denticulata), Cheo {Engelhardtia roxburghiana)... ' ni.A.I.1.2. Phdn qudn hi cdy bgi khdng CO cdy go j Cd thdnh phan loai uu thi Id: Sim {Rhodomyrtus tomentosa), Mua {Melasloma candidum), \
Biim bup {Mallotus paniculala), Ba chac {Euodia lepla)... Cdc quan xa nay gap nhilu d cdc x5:
Dao Due, Phong Quang, Phuong Tien, Phuang Thien, Viet Ldm...
500
HQI NGHI KHOA HQC TQAN QUOC V£ SINH T H A I V A TAI N G U Y E N SINH VAT L A N THCf 5 IV. Ldp quan H ^° (Grassland vegetation)
/ K ^ i . Nhonfqmn hi co dgng lua cao co cof gd che phd tir 10-40%
IVJ.I.L Qudn hg co chiu hgn
Uu hi^) LA" {Saccharum sponlaneum) + Chit {Thysanolaena maxima)
Thdnh phan cay gd, cay bui Id cdc cay chju han: Mdng tang {Litsea cubeba), Sim (Shodomyrtus tomentosa), Mua {Melasloma candidum)...
Cdc qudn he nay cd nhilu d cdc M : Trung Thanh, Phong Quang, Qudng Ngan, thj tran Vj Xuyen.
IV.B.1. JVbdm quaa be co dang lua thap va trung binh (0,5-lm) co cay go cbe pbu t^lO-40%
IV.B.I.l. Quan hi co chiu hgn
Quan he nay dugc hinh thdnh chu yeu tren cdc nuong riy bj bd hda vdi uu hgp Cd tranh {Imperaia cylindrica) + Cd sdu rom {Selaria glauca) + Cd dang {Paspalum longifolium) + Cd giing {Panicum repens). Ngodi ra cdn cd mdt sd lodi cay gd mgc rdi rdc nhu: Thanh nganh {(^rcaoxylum conchinchinense), Ba soi {Macaranga denticulata)...
Quan he ridy thudng gap d Dao Due, Cao Bd, Phong Quang, Phii Linh, Kim Thgch.
IV.Cl. Nhom quan hi co khong dgng lua TV.C.1.1. Qudn hi Chudi rimg
U'u hpp Chuoi rimg {Musa uranoscopos) phdn bd d cdc xa Minh Tdn, Cao Bd, Thanh Due...
IY.C.1.2. Qudn h4 Co lao
U'u hpp Cd lao {Chromolaena odorata) gap phd bien d cdc nai dja hinh thdp d cdc dja phucmg trong huyen.
IV.CI.3. Qudn he Gugt
Uu hgp Gupt {Dicranopieris linearis) dugc hinh thanh tren ddt nuong rdy bj bd hda do ddt bj thoai hoa hay tren cdc rimg bj chay nhung khdng cd kha ndng phuc hdi. Tren quan he nay cd xuat hifn mdt sd lodi cay gd va cdy bui nhu: Thdu tdu {Aporosa sphaerosperma). Sim {Rhodomyrtus tomentosa), Mua {Melasloma candidum), Mang tang {Litsea cubeba)..
2. Cac nguyen nban Iam suy thoai tham thuc vat d huyen Vi Xuyen
Trong nhirng nam gdn ddy do nhu cdu kinh te vd ddi sdng, tai nguyen rimg da bi khai thdc can kift va suy thoai nghiem trgng. Cdc nguyen nhan chinh Idm suy thodi thdm thuc vat d huyen Vj Xuyen la:
Hogt ddng khai thdc go, cdi: 6 Hd Giang ndi chung vd huyen Vj Xuyen ndi rieng tinh iTflng pha rimg ddc dung, rimg phdng hd ddu ngudn dien ra ngdy cdng gay gdt trong vai nam trd 91 day. Do lgi nhugn khai thdc gd Nghien len tdi vai trieu ddng/ngudi/ngdy nen cac doi lugng ani t|c bat chap lugt pljap, dimg nhieu thii dogn de tan phd rirng. Hang tram, thdm chi hang nghin
^ go Nghien, Trai (nhdm IIA) cd thu cd dudng kinh tir 0,8-1,5m dd bi ddn ha, cdi Uidl trong sir bdt irc cua cdc ca quan chiic ndng. Do do khai thdc gd la nguyen nhdn chinh Idm cho chat lugng ciia rimg
°\ suy dioai nghiem Upng.
HQl NGHj KHOA HQC T O A N Q U Q C V E SINH THAl VA T A I N G U Y E N SINH VAT L A N THl> 5 Ngodi ra, do thu nhdp cua da sd cac hd dan trong huypn cdn thdp vd theo thdi quen sinh | boat nen cui dugc sir dung Idm chdt ddt Id chu ylu. Do dd nhiJng hg gia dinh ngheo khdng cd j ddt sdn xudt, khdng cd vdn dau tu da vao rimg khai thdc cui de ban nham tang them thu nh|p j
cho gia dinh. I Chuyen doi muc dich sir dung rirng: Trong dja bdn huyen cd nhieu md khodng san Ion i
nhu: Md vdng d xd Linh Ho, md sal d xa Timg Bd, Cao Bd, Viet Ldm... Da phan cac md khoang 1 sdn diu ndm d nhiing noi cd riing nen khi khai thdc phdi vira pha rimg, vira phai md dudng giao thdng de van chuyen da Idm cho dipn tich rimg gidm siit nghiem trgng. Ngodi ra viec xay dimg a cdc khu cdng nghiep (khu cdng nghiep Binh Vdng d xd Dgo Due, cum cdng nghiep d cac xi | Thuan Hod, Tung Bd...) hay md cac tuyen dudng lien thdn, lien xa deu dan den phd hogi rimg.
Khai thdc ldm sdn ngodi go: Ngodi khai thdc gd quy thi khai thdc lam san ngoai gd cung 1^
mdt hoat ddng tan pha lai nguyen rirng. Day cd Ihl xem la nguyen nhan tac dgng Iam suy ki^t tdi nguyen nhanh nhdl. Lam sdn ngoai gd bao gdm cdc loai dgng vgt hoang da, cdc loai thirc v^t cho nguyen lieu quy nhir: Song, may, tre, mia, vau... va cdc loai cay thudc. Tdt cd cac logi Iren diu duoc su dung trong ho gia dinh, ban vd xuat khdu nen tinh trgng khai thdc dien ra kha phS bien trong huyen.
Chdy rirng: Chay rirng cung Id mgt nguyen nhan quan trgng Idm suy gidm tdi nguyen rimg, gdy anh hudng tdi cdc hoat ddng sdng cua sinh vdt tren mpt dien tich rdng Idn va gay ra cdc h?ii qud xau (gay xdi mdn, lii lut, han hdn, mdt da dgng sinh h o c . ) den ddi sdng con ngudi. Nguyen nhdn chii ylu cua chdy rirng Id do hoat dgng khai thdc ciia con ngudi nhu: Ddt lira Idy mgt ong, ddt nuong lam ray, dot cdc gdc cdy to de khai Ihac gd... hogc do thdi tiet nang ndng keo ddi.
HI. KET LU^N
1. Theo khung phdn logi cua UNESCO (1973), thdm thirc vat tir nhien huyfn Vj Xuyen gdm 4 Idp quan he: Ldp qudn he rirng kin, Idp quan he rung thua, Idp quan he cdy bui va lop quan he cd. Tdt ca nhiing qudn he thugc cdc idp quan he rimg thua, cay bui vd cd diu Id trang thai thu sinh dugc hinh thdnh do ldc dgng ciia con ngudi.
2. Nguyen nhdn gay suy thoai rirng d huyen Vi Xuyen do khai thdc gd, ciii; chuyin doi myc dich sir dung rimg; khai thdc ldm san ngodi gd qua mdc; do chay rirng. Dja phuong cin cd nhung bien phdp hiiu hipu de bao vp tai nguySn rimg, xd ly nghiem minh vdi nhimg hdnh ddng khai thdc bia bai tdi nguyen rimg. Tang cudng tuyen truyen cho ngudi ddn ve y thuc bao ve rimg, dong then can cb chinh sdch hd trg cho ngirdi dan sdng gdn rimg ve vdn vd ky thugt san xudt de ndng cao thu nhgp on dinh den sdng.
TAI U E U THAM KHAO
i Nguyen Tien Ban (chu bien), 2003-2005. Danh luc cac lodi thyc vat Vifit Nam, lap 1, 2, 3. NXB.
Nong nghifp, Hd Noi.
i. Hodng Chung, 2008. Cac phucmg phdp nghien cuu qudn xd thuc vdt. NXB. Gido due, Hd N$i.
3. Nguyen Quang Hung vd cong su, 2009: Budc ddu n^ien ciiu tinh da dgng thyc val d Khu Bdo ton thien nhien Tay Cdn Linh, huyfn Vj Xuyen, Ha Giang. Bdo cdo Hpi nghj Khoa hpc Toin quoc W ^ Sinh thdi vd Tdi nguyen sinh vgt ldn thir ba,I0/2009. Hd Npi, tr 577-584.
4. Thdi Vdn Trirng, 1970. Thdm thyc vgt rirng Viet Nam, NXB. Khoa hpc va KJ thudt, Hd Npi.
5 UNESCO, 1973. Inlernational classification and mapping of vegetation, Pari.
MOI NGHI KHOA HQC T O A N Q U Q C V E SINH T H A I V A TAI N G U Y E N SINH VAT L A N THLF 5 THE CLASSIFICATION OF NATURAL VEGETATION AND THE CAUSES
OF FOREST DEGRADATION IN VI XUYEN, HA GIANG PROVINCE DO KHAC HUNG, LE NGOC CONG
SUMMARY
AcconJing to the classification framework of UNESCO (1973). the natural vegetation of Vi Xuyen Histrid Ha Giang province includes 4 class formations: Closed forest, wood land, scrub and herbaceous veaetaUon All the areas which belong lo the woodland, scrub and herbaceous fonnalions are the anlropogenic secondary vegetations.
The cause of forest degradation in Vi Xuyen district are logging, firewood collection, land use change of forest area, exploitation of non-timber forest products, forest fire. The proposed measures to protect forest resources are: Sbiclly deal with the illegal exploitation of forest resources, improvement of people awareness in forest protection, to support people living near the forests by providing capital and production tedmiques.
