Hoi Dia ly Viet Nam D^i hgc Thdi NguySn DAC T R I T N G CAC H E SINH THAI NHAN SINH H I N H T H A N H
SAU TAC DONG CUA CHIEN TRANH H 6 A H Q C DIA BAN HUYEN G I O LINH, T I N H QUANG T R I
Nguyen Ddng Hgi', Kuznetsov A. N, Kuznetsova S. P, Phgm Mai Phuang Abstract
Charactics of anthropogenic ecosystems, that fonned under impacts of chemical war in Gio Linh district, Qaang Tri province
During the war. natural ecosystems of Gio Lmh district were seriously impacted by military operations, especially using herbicides of the U.S. military. Consequently, over the decades, the vestiges have been occured in many ecosystems tn the area. Thousand hectares of vacant land, grasslands and shrubs created after the war are still existed unttll now but no answer.
The anthropogenic ecosystems that formed after the impact of herbicides usually have simple structures, has not even reached a stable formation: secondary forest ecosystem, vegetation with unstable stories, many vines, the grassland ecosytem, the grassland and shrub with simple structure, mainly species compostion of hard and big stem grass.
As vegetation succession, in current conditions, recover of the forest is entirely possible occurred in the transition zone between forest and grassland, but in very slow speed. The reason for this is because the destroyed ecosystems are existing critical factors that forest vegetation is not likely to arise and exist This is the reason why even though the war has finished in nearly 40 years, the vast area of Gio Linh district shll exists grassland and shrub ecosystems.
To be able to exploit, use and improve the large area of grassland, shrub formed after the war in Gio Lmh, It needs appropriate technical measures; the first measure is upgrade the environmental conditions of the area
1 DATVANDE
Trong thdi gian chien tranh, quan dgi My da su dyng chat diet cd (CDC) d^ buy di?t thdm thgc vdt rung d Mien Nam Viet Nam. Ddy la mgt trong nhung nguyen nhan lam thay doi nhieu h?
sinh thai (HST) rimg; bien nhung cdnh rimg nguyen sinh gidu cd ve tiu lugng go, ve da dgng lodi dgng thyc vgt, phong phii tang tan thanh nhimg HST rung nhan sinh cd trii lugng ngheo ki$t, thdm chi trd tfadnfa trang cd, trdng cd cay byi ma den nay van con pho bien 6 nhieu tinh phia Nam vd Tdy Nguyen nuoc ta [1, 4, 6]. Su bien mat hodc ttiay doi cua quan xa thuc vgt rirng dd keo theo hdng loat bien doi nay smh cua dieu kien tdi nguyen vd mdi trudng: Id su suy gidm nghiem trgng tdi nguyen sinh hgc, tdi nguyen vd moi trudng dat, tai nguyen vd moi tnrdng nude, tai nguyen va dieu ki$n khi hgu [4, 5, 7, 10].
Trong tien trinh^do. huyen Gio Luifa tinh Quang Tri noi len nhu mgt "diem nong" ve six tan phd cua chien tranh doi vdi tdi nguyen va mdi tiudng tii nhien. Nhieu dign tich rung ty nhien da bien mat vi CDC vd bom dan. Hau qua la qua nhieu tiidp nien nhung dau tich van cdn in dgm ti^en nhieu HST khu vuc. Nhiing dien tich chiu anh faudng ndng ne cua CDC trudc het phdi ke den la hang chyc ngfam ha dat trong, tidng cd cay byi Wnh thdnh sau chien tianh van cdn ton tgi den ngay nay [5, 6]. Da co nhieu cdng trinfa nghien cuu tiiuc tnmg phd fayy cua CDC doi vdi rimg va tai nguyen rung d cac vimg Mien Nam Viet Nam [1, 7, 8]. Tyy nhien, nhihig nghign cuu v^ cdc HST cac quan xa tiiuc vdt hmh tiianh sau chien tranh hod hgc d Qudng Tri cdn khd khiem t6n Dgc biet cfaua CO ngfaien cuu, quan trdc cy tiie ndo de danfa gid sy bi^n dfii cua cdc HST nhdn sinh famh tiidnh sau chien tianh; cung-chua M nghien cuu ndo ly giai cho sy tfin tai b^n vimg cua cdc q u k xa co cay byi ban 40 nam sm. chien tranfa hod fagc - mgt faien tugng phfi bi^n khdng chi d Gio Linh md con o nhieu khu vyc kfaac o Mien Nam va Tdy Nguyen.
. N ^ e - i ^™ , « ^ f ^ ™ v i sir b i k d& cie HST nhan sinh dae tnmg, dje biet la eiu true eie quan xa thuc vat cua HST Hm vuc huyen Gio Linh l i hit siic ein Mk. Dilu niy khong nhttng eg y nghia thye aen giup chg viec dinh huong sii dung hgp ly tii nguyen v i lanh thi, ma con gop phin ' Trung tdm Nhi$t dai Vi^t - Nga
Kpyiu Hdi nghf Khoa hgc Dfa lp todn qudc ldn tha 7
Hoi Dia Iy Vifit Nam Dai hgc Thdi Nguyen lam sang to co che tdc ddng va bien doi cua cac HST hinh thanh sau nhung tac dpng mgnh me cua chien tranh hoa hgc va nhiing tdc dpng tieu cue khde tii phia con nguoi.
2 D 6 I TirONG, PHUONG PHAP NGIDEN CUtJ
+ Doi tirang nghiin cOu: Doi tuong nghien cuu Id cdc quan xa thuc vat ty nhien da bi bien doi phyc hoi tharii HST rung nhan sinh, trdng cd, cay bui nhan sinh tren nhung khu vuc bi rai CDC trong chien tranh tai huy?n Gio Linh, tinfa Quang Tri.
+ Phirang phdp nghiin cuu: De gidi quyet tot cac nlii?m vu dgt ra, da six dyng nhieu phuang phap khac nfaau, trong dd cac phuong p h ^ chu dao la:
- Phuang phdp bdn dd, he thdng tin dia ly (GIS): Phuang phap nay giiip nhan biet lanfa tfao Gio Linfa mpt cacfa kfaai qudt vd nfaanh nhat. Co sd du lieu dudi dang bdn do kfadng nfairng cd y nghia ve mat phan bo kfadng gian cua cac thanfa phan mdi trudng ngfaien ctiu ma cdn cfai ra nfaung thudc tinh cua doi tugng theo timg khu vyc cu tiie. Phuang phap ndy ciing dugc dp dung de thanh lap ban do HST nhan sinh fauyen Gio Linh d ty le 1/100.000 phyc vu cho vi^c mo ta cdc don vi, cac quin xa thuc vat ^ trung.
- Phirang phdp khdo sdt thuc dia: Thuc diat Id to hgp cua nhiing phuong phdp khac nhau nfau: phuang phdp phdng van, pfauong phdp md td dia hinh vd cdc qua trinh dia mao, phuong phdp thu Hb^ so li$u... Vi?c dieu tra thyc dia dugc tien hanfa theo cac tuyen vd diem. Trong moi HST vd sinh c ^ , cdc phuong phdp dugc vgn dyng \a!p lai de Ihu thdp so lieu so sdnh (cd dieu cfainfa cho phu hgp vdi ddc tnmg cda timg dia diem nghien cuu).
- Phuang phdp nghiin cOu dia thuc vdt: Ngfaien cuu dia thyc vgt dugc tien hanfa theo cdc tuyen va tai cac d tieu chuan tgm thdi Viec xdc dinh cay vd day leo dugc tien hanh tren ca sd nghien ciiu tong hgp cac day hi$u ve hinh thdi Ngodi tfayc dia, viec dinh danh cay chii yeu tdi mtic chi. Viec xdc ^nh ten lodi dya theo tdi lieu ciia Pham Hodng Ho "Cdy cd Vi?t Nam" tgp 1, 2 va 3 [2], Ten ggi hp va chi ciia thyc vgt cd faoa theo he thong phan loai cda A. Takhtajan (1987). Khi xem xet ddc diem cau trie diing cua tham thuc vat duoc fainfa thanh tren nhitng quan xa khac nhau, tien hanfa mo td cfai tiet theo cac tang cay diing.
- Phirong phdp so sdnh, ddnh gid tdng hgp: De phan ticfa vd ddnh gid sy b i ^ doi ciia HST, qudn xa thyc vdt vd cdc tfadnfa pfaan mdi trudng, viec so sanh so li|u thu t h ^ dugc la rat quan trgng Ca sd tdi li^u dung so sanh la ket qud nghien cuu cua chiing toi tai rat nhieu dia diem 6 Mien Nam Viet Nam vd so U^u thu dugc tgi Kfau bdo ton Ddk Rdng, tinh Qudng Tri - nai khong chiu tac dpng ciia CDC de doi cfaung.
3. KET QUA NGHIEN CUU VA T H A O LUAN
a) Hoat dgng chien tranh bod hoc d Quang Tri va huyen Gio Linh
Vdi vi tri dia chien luge vd quan sy quan trpng, Qudng Tri dugc xem Id tuyen liia cua cupc chien tranh chong My. De thiet 1 ^ vanh dai trdng, quan dpi My da sii dyng nhieu bi?n phdp khac nhau, trong dd tac dgng noi bgt doi vdi tdi nguyen va mdi trudng la vi^c su dyng CDC cd chiia dioxin rdi xuong nhthig kfau vyc cd tfadm thuc vdt, ddc biet la thdm thyc vat ty nhien.
Theo ket qud thong k€ tii nhieu nguon tdi heu khde nhau, trong dd cd tdi li$u cua Bg Quoc phdng My, di?n ticfa rung bj tdc dpng trong gidi hgn huyen Gio Linh tgp trung nhieu nhat la tuyen liia VI tuy^n 17 dgc song Ben Hai, keo dai tir kfau vyc Con Tien - Doc Mieu len %\a!p biSn gidi Viet Lao tiiugo-^a-bm cac xa Linh Thugng, Hdt Thai, Lmh Hdi, Gio San, Gio Hod, Gio Cfaau [5, 9].
Miic dg vd phgm vi phun rai rdt khac nhau, trong do cd mgt so di?n tich chiu nfing dg phyn rai tren l.OOOgal/km^. Nhieu di$n tich cdn lai cd nong dg phun rai tix)ng khodng 200 - l.OOOgal/km^. Tyy vgy. Cling vdi tdc dgng faSn hgp ciia bom dgn vd bom chdy napal, nhimg di$n ticfa bi phun rdi da tra tiianh dat trong hogc trdng co. Sau ndy chi cd mpt phan di$n tich rat nfad phuc hoi thdnh rimg.
^yiu Hgi nghi Khoa hgc Dfa lp todn qudc ldn tha 7 ~ ~ ~ ^ Q
HM Dia \i Viet Nam Dai hoc Thii Nguy*"
b) Ban d l hien trang cac HST nhSn sinh huygn Gio Linh ty 1$ 1/100.000
D6 phuc vu cho viec xic dinh quy mo di|n tich, phan bo khong gian cQng nhu mo ta tung don vi HST rimg bi tic dgng boi chien tranh hoi hgc, chiing toi xay dimg ban do HST nhan si huyen Gio Linh ty le 1/100 000. Bin d6 duge thinh lap theo nguyen tic va chi tieu cu the:
* Nguyin ldc thdnh lap bdn dd- Van dung 3 nguyen tic chii dao la nguyen tic phat sinh hinh thai, nguyen tic dgng nhit tuong doi va nguyen tie toin ven lanh tho.
* Chi tliu phdn chia: Do doi tuong nghien ciiu tap tnmg vio 2 HST nhan sinh dae tnmg la rimg diii sinh nhan tac v i trang co cay bui nen cie chi tieu phan chia dugc lira chgn de lim ro cac don vi eua 2 HST niy Cac HST khu vuc nghien cira duoc phan chra theo 3 cap; phu he, lop va kieu HST, trong do lop dugc phan chia theo die tnmg quan xa thuc vat v i kieu HST dugc phan chia theo su phan hoi cua quan xa thirc vat theo dai eao.
Bang 1 Dgc tnmg phdn hod cdc HST nhdn sinh huyen Gio Lmh hinh thdnh sau tdc ddng
T T
/
1
2
//
3
4
5
Dffnvi HST
Ldp HST rimg nhan sin
Kieu HST rung nhan sinh d dp cao 100 - 300ni
Ki^u HST lung nhan sinh d dd cao > 300m
Ldp HST trang cd cdy bid
Kieu HST trdng cd cay bui d cao < lOOm
Kieu HST tring cd cdy byi d cao 100 - 300m
Ki^u HST tidng cd c ^ byi d cao > 3 0 0 m
COng
cua chiin tranh hod hgc
T4n su^t
6
3
3
21
16
3
2
27
Difn tich (ha)
2.697,91
1.589,86
1.108,05
18.323,65
7.716,11
9.129,26
1.478,28
2 1 . 0 2 1 ^ 6
P h a n b ^
Phan tdy va tay bdc xa Linh Thugng
P h ^ tay xa Linh T h i g i ^
Phia ddng, dgc thung lung s6ng Ben Hdi vd phan tdy ciia huy^n
T ^ tnmg d t i u i ^ tdm xd Linh Thugng
P h ^ nam xd Linh Thugng
Ky h i ^ tr^nbdn i 6
R 4 , R 5 . R 6
R l , R2, R3
T i r T C e d e n TC20
TC3, TC4, TC5
T C I , TC2, TC3
Kpyeu Hdi ngh] Khoa hgc Dfa Iptodn qudc ldn tha 7
Hoi Dia Iy ViSt Nam Bai hgc Thai Nguyen
BAN Dti Ht SINH THAI NHAN SINH HUY$N GIO LINH TINH QUANG TRI N.\M 2011
c) Djic diem c^u true cdc HST nhan sinh ddc trung
* Ldp HST rimg nhan sinh (cd 2 kieu)
+ Kieu HST rimg nhdn sinfa d do cao 100 - 300m: cd 3 don vi vdi ^ng dien tich 1.589,86ha, ph&i bo chii yeu d khu vuc phia tay, tdy bdc xa Linh Thugng.
'^.V yiu H0i nghi Khoa hgc Dia lp todn qudc ldn tha 7
^m
Hdi Dia ly Viet Nam Dai hgc Thdi NguyS"
Hien trang thyc vgt trong HST d cdc muc do kha khac nhau Da ghi nhgn nhimg cay go non va cdc choi nhdnh mgc len tii nhiing goc cut, co chieu cao tii 1,5 den 4m vdi cac chr chi Budi bung Acronychia, ho Cam (Rutaceae); chi Siia Alstonia. ho Tnic ddo (Apocynaceae). chi Doi Arehidendron, hg Tnnh nir (Mimosaceae), chi Trdc Dalbergia, hp Ddu (Fabaceae), chi Cam ngudi Ardisia, hg Com ngudi (Myrsinaceae), chi Mit Artocarpus, chi Ruoi Streblus, ho Dau tam (Moraceae); chi De gia Breyniopsis. hp Thau d4u (Euphorbiaceae); chi Mdc Caryota, hg Cau dira (Arecaceae); chi Que Cinnamomum, chi Boi ldi Litsea, chi Bdi ldi nude Neolitsea va chi Khao Phoebe, hp Long nao (Lauraceae); chi Thanh nganh Cratoxylum, chi Biia Garcinia. hp Mang cyt (Clusiaceae); chi Diic diep Daphyiphylum. hp Diic diep (Daphnyphylaceae); chi Thi Diospyros, hp Thi (Ebenaceae); chi Com Elaeocarpus, hg Com (Elaeocarpaceae); chi Cd ke Grewia, hp Day (Tiliaceae), chi Dan Ixora, chi Lau Psyehotria, chi Gang Randia. fag Ca phe (Rubiaceae); chi Mdu chd Knema. hg Mdu chd (Myristicaceae); cfai Bdng ldng Lagerstroemia, hg Tii vi (Lithraceae); chi Sam Memecylon, hg Mua (Melastomataceae), chi Nhgc Polyalthia, ho Na (Annonaceae), chi Trdm Sterculia, hp Trdm (Stereuliaceae); chi Den Vitex, ho Cd roi ngya (Verbenaceae).
Ciing ghi nhdn dugc nhiing loai day leo nhu chi Bgc thau Argyreia. hg Khoai lang (Convohoilaceae); chi Mdy Calamus, ho Cau diia (Arecaceae), cfai Gdm Gnetum, hg Day gdm (Gnetaceae); chi Ngay Rubus. hg Hoa hdng (Rosaeeae); chi Chac chiu Tetracera, ho Sd (Dilleniaceae); chi Bii de Uvaria. hg Na (Annonaceae), mgt so loai thugc ho Day khe (Connaraceae), hg Tiet de (Menispermaceae), va cac loai than thao - chi R6 quat Dianella. ho Huong bai (Phormiaceae); chi Huyet giac Dracaena, hp Huyet giac (Dracaenaceae); chi Dg cam Hedyoiis. hg Cd phe (Rubiaceae); Cung vdi do, d day cung phdt trien nhiing Ioai cay dae tnmg ciia khu vyc bi phd buy nhu chi La nen Macaranga, fap Thau dau (Euphorbiaceae); chi Hodng mpc Zanthoxylum. ho Cam (Rutaceae), chi Thdi h&Alangium. hg Ihdi ba (Alangiaeeae).
Til dau hieu thuc trang ndy cimg vdi ket qud faoi ciiu, phdng van cu dan dia phuong da cho phep chung tdi di den nhgn dinh, tgi khu vyc nay tiudc chien tranh dd timg tfin tai kieu rimg kin nhiet ddi thudng xanh ddc trung cua viing dat t h ^ Mien Trung Viet Nam.
Ngodi ra, tgi nhiing dia hmh tii^ va dpc theo nfaiing bd suoi, thudng gap cac don vi HST vdi di§n tich nhd (khoang 400 -500m^). Trong thanh phan, da ghi nhdn dugc cac lodi nhu Ka nia Irvingia malayna (Irvingiaceae), Sira Alstonia scholaris (Apocynaceae), chi Thanh nganh Crato^lum (Clusiaceae), chi Cd ke Grewia (Tiliaceae), chi Xdng mau Horsfieldia (Myristicaceae), chi Sfii Lithocarpus (Fagaceae), chi Cg Livistona (Arecaceae), chi Ngu gia bi Scheffiera (Araliaceae), chi Tram Syzygium (Myrtaceae).
^ Mac dii cdc cay go rimg cd ra hoa, ket qud, nfaung nhihig cay non cua chung khong the phat trien dugc vi hi nhihig ddm cay cd che phu, khong tiie tiioat ra ngoai cho ti^ng, vd nhung mdnh rimg nhu tiie khong cd dupc xu huang phdt trifin rpng 0 ddy khong tiiay xay ra qua trinh md trong do cdc cay go rimg phdt triln cd tiifi lin chifim dugc nhimg lanh tiio moi va Ioai bd cac trdng cd - cay byi (tiiam chi khi nhimg lanh tiio dd ndm ngay canh cdc khu rimg).
+ Ki^u HST rimg nhan sinh ddg cao >30Dm.cd 3 dan vi vdi tfing dien tich 1.108 OShaciinR phan bo khu vuc phia tay, tay bdc xa Linh Thugng. Cac dan vi HST nay ndm nfii ti^p ngay phia tren cua dai 100 - 300m. Tiong sfi 3 don vi tiii cd tdi 2 don vi co dien h?p, tii 3 - 29ha.
Kfit qud khdo sat cho tiiiy, tai cdc khu vyc tifip gidp vdi cac q u ^ xa cay cd cho dfin nav vSn con duy til dugc nhiing mdnh rimg ty nhien mdc dii chyng da bi tac ddng va bi pha huy mdt nhdn Cay go nmg mang tinh da trdi. Tuy vay. tgi mgt sfi dia difim, tmh trgi chi co 6 mot sfi hg' vd cTu tiuc nmg dugc phan faoa tiianh 3 tang tuang dfii i6 ret.
Kyyiu Hgi nghf Khoa hgc Dia lptodnqii3^]g^^i^^-^
Hoi 0ia I^ Viet Nam Dai hoc Thai Nguyfin Trong do: Alst-,^/j/on/a, Cin- Cinnamomum, Tiios-Diospyros, E\-Elaeocarpus, Eur-Eurycoma, Fic-Ficus, Gsa-Garcinia, Gir- Gironniera, Gon-Gonocanum, hag-Lagerstroemia, Laur- Lauraceae, \A^-Luhocarpus,
\A\s-Lilsea, Wy-Livistona, Mngf- Mangifera, Vod.n-Podocarpus nenfolius, Po\-Polyalthia, Pter- Pterospermum, Q-Quercus, Scf- Schefflera, Str-Streblus, Tar- TameUa, Nil-Vitex.s^.
(Rubiaceae).
Hinh 1 Kidt cdt dang qudn xd th^: vgt trong HST nhdn sinh d dg cao > 300m khu vuc go dot huyen Gio Linh
- Tang tren ciing (tang 1) cd chieu cao 17 - 20m, dudng kinh than cay 40 - 70cm, d goc nhieu loai cay phat trien nhiing re bgnh ve nhd; tdn day, nen chat, hinh 6 van hogc cau, ban kinh tan khoang 2 - 3m, To thdnh loai gom Sua Alstonia sholans, hg Tnic ddo (Apocynaceae), Ko nia Irvingia malayana, hg Ha nu (Irvingiaceae), Bang lang oi Lagerstroemia caliculata, hg Tii vi (Lythraceae), Dau tdm Moms album, hg Dau tdm (Moraceae), Huynh Tarrietia javanica, Ldng mang Pterospermum heterophyllum, hg Trdm (Stereuliaceae), Thau ITnh Alphonsea sp., hg Na (Annonaceae), cac lodi De Castanopsis spp., Sfii Lithocarpus spp., hg D6 (Fagaceae), Que Cinnamomum sp., hg Re (Lauraceae), Cdm Elaeocarpus sp., Nhim nude Sloanea s p , hp Com (Elaeocaipaceae), Bdi ldi Litsea sp., hp Re (Lauraceae), Chan chim Scheffiera sp., hg Ngu gia bi (Araliaceae). 0 khu vyc chdn sudn, noi cd nhieu suoi vd thdc nude, tinh tipi thugc vfi lodi Cfaan chim Scheffiera sp., trong khi tren dang dia fainh sudn va dinfa, tinh trgi thugc ve cac loai ciia hg D^
(Fagaceae).
Tang 2 cao 6 - 1 Im, cd cau triic tii cdc lodi Budi bung Acronychia pedunculata, hg Cam (Rutaceae), Lgc vimg Barringtonia sp., hp Lpc vung (Lecythidaceae), Thanh nggnh Cratoxylum sp., Biia Garcinia sp., hg Biia (Clusiaceae), Chdm chdm Nephelium sp., hp Bo hdn (S^indaceae), Nhpc Polyalthia sp., fag Na (Annonaceae), Tram Syzygium sp., hg Sim (Myrtaceae), D6n Vitex sp , hg Cd roi ngya (Verbenaceae). Diem ddc trung cua tang 2 la su gdp mat cua lodi Co kich thudc ldn Livistona saribus, fag Cau dira (Palmae), cay cao tdi 6 - 8m. Tgi mgt so dia diem, loai Cg Llvistoru3 sanbus mpc thdnh khom. Lodi nay ghi nfaan dugc ca d khu vyc chdn, suon vd dinh doi.
Tang 3 cau tao tii nhung cay cao 2 - 5m, bao gom cac loai: Dung dinh Caryota mitis, Mdc cgc Licuala sp,, hg Cau diia (Palmae), Bdch benh Eurycoma longifolia, hg Tfaanfa that (Simaroubaceae), Thy dao Gonocaryum subrostratum, hg Tfau dao (Icacinaceae), Chdi mdi Antidesma sp., De Breynia sp,, Diep hg chau Phyllanthus sp., hp Thau dau (Euphorbiaceae), Cam ngupi Ardisia sp., Dan nem Maesa sp , hp Com ngudi (Myrsmaceae), Cong Calophyllum sp., hp Biia (Clusiaceae), Don Ixora s p , Xii huong Lastanthus sp., Lau Psyehotria sp., hg Cd phe
^ b i a c c M ) ^ — -
Hien tugng cay non ciia nhung cay gd rimg khong the phdt trien ra ngodi dam c6, cay bui vdng lan can cung dugc l^ lgi giong nhu d kieu I K T dudi 3D0m, Dieu nay cho phep nhgn dinh ban day ve kha ndng phyc hoi rimg sau tdc dpng cua CDC faoac khong dien ra, hoac dien ra vd ciing chgm chi^,
* Ldp HST trang cd cdy bui (co 3 kieu)
Kpyiu Hgi nghi Khoa hgc Dfa lp todn qudc ldn tha 7
Hoi Dialy Viet Nam p»i hgc Tha^Nguye;;
Cd dien phan bfi rpng d tat ca cac khu vyc va dai cao tren lanh tho huyen Gio Linh, phan hoa thanh 3 kieu. ^ . A i*
+ Kieu HST trang cd cay bui d dp cao < 100m: cd tan suat xuat hien nhieu nhat vdn lo lan.
Tong di?n tich la 7.716,1 Iha. Cac don vi nay phan bo chu yfiu d khu vuc phia dong, dgc tiiung lung song Ben Hdi va rdi rac d phia tdy cua huyen.
+ Kieu HST trang cd cay byi d dp cao 100 - 300m: chi xuat hi?n 3 lan nhung vdi dign tich ldn, 9.129,26ha, phan bo chii yeu d khu vyc trung tam xa Linh Thugng.
+ Kieu HST trang cd cdy byi d do cao > 300m cd 2 lan xuat faien vdi dien tich 1.478,28ha va
phan bo chu yeu d phan nam xd Linh Thugng. ^ Da tdc dgng manh liet ciia CDC va bom napal, 3 kieu HST tiang cd cay byi khong cd nhieu
khde bi?t ve cau triic tiiyc vdt Diem kfaac biet tiie faien chi d miic dp phong phii va siic song tiiyc vat tiieo tinh chat cua dat va tifiu khi hgu. Theo dd, thyc vat trong cdc HST trang cd cdy byi la nhimg quan xa cd tiidnh phan dong uu trgi la Cd duoi voi nhieu gie Pennisetum polystachyon va Lau Eryanthus arumdinaceus Mgt so dien tich ghi nfaan dugc lodi troi la Co tranh Imperata cylindrica. Loai Cd dudi voi nhieu gie dgt tdi chieu cao 120 - 150cm vd Lau co kich tiiudc dat tdi 220cm chieu cao.
Ngodi nhung lodi cd ke tr6n, trong kfau vyc nay cdn ghi nhgn dugc nhiing loai thyc vat nhu Duong xi Pteridium aquilmum, chieu cao tdi I20cm, C6 lao Eupatorium odoratum, Eupatorium spp. (Compositae), Re quat Dianella nemorosa (Foimiaceae), Luoi thdo Lindemia spp.
(Scrophulariaceae),..
Dg che phii tai nhirng khu vyc nay dgt tdi gan 100%. Ting cd co mat dg day ddc nhat d dg cao 30 - 80cm. <3 mgt vdi noi, nhung khdm cay cd ndm canh nhau khoang 30 - 50cm. Vdo mua kfad thyc vat van tiep tyc phdt trien mgnh vd nhirng phan cay la trSn mat dat khong bi kho va chet. Tuy nhien tren mat dat van quan sat tfaay nfaung Id co chet, nhung chung khong du de tgo thdnh ldp la j
ryng, ' Trong nhiing trdng cd cay byi nay, da ghi nhdn dugc nhirng Ioai tien phong va mgt so cay go
rimg. Nhiing lodi tien phong thugc chi Ba soi Macaranga, Ba bet Mallotus (Euphorbiaceae), chi Mua Melastoma (Melastomataceae), chi Hu day Trema (Uhnaceae) va chi Hoang mgc Zanthoxylum (Rutaceae), Chieu cao cua cay tai 2,5m. Nhiing lodi tien phong nay thudng Id cdc cay thich nghi vdi vdi do chieu sang mgnh (ven dudng vd d nhiing nai ma ldp cd da bi con ngudi pha buy). Tai nhiing dia diem ndy, khdng quan sat tfaay trudng fagp kfai md cdc nhom cay tien phong huih tfaanfa, tan cdy sdt vdo nfaau, che aiUi sdng mgt trdi vd logi bd dugc ldp cay cd ben duoi, gifing nhu quan sat thay d nhung rung cay dang phyc hfii.
Nhihig cdy rimg cd ciiiey cao tdi 6m, thudng la nhimg lodi thudc tang thap nhat ctia rimg cay go nhu Tnic tiet Caralba sufruticosa (Rhizophoraceae), Choi mdi Antidesma sp. (Euphorbiaceae), Due diep Daphnyphyllum sp. (D^bnypfayllaceae), Don Ixora sp. (Rubiaceae).
d) Giai thich ve sir bifin ddi va diln thfi HST hinh thdnh sau tdc ddng cua CDC Viec su dyng CDC lam cho cay go rimg vd day leo bi ryng la. Tuy vay, say khi rimg bi phun rai lan dau thi phan ldn cay go rimg deu cd khd nang phdt trien Id mdi. Neu rimg bi phun rai nhifiu lan se diln den cdy go vd cac lodi thuc vgt khde hi chet, va sau dd bom n ^ a l dugc su dyng de huy diet hoan toan tham thyc vat rimg.
Tren nhiing khu vyc bj mat di thdm thye vat rimg, hgt ciia cdc lodi thyc vgt tien phong dugc gid dem tdi, ma chu yeu la cdc loai cd vdi dai dign cua chi Imperata. Pennisetum, Themeda (Gramineae) vd Eupatorium (Compositae), Sau mgt miia mua, cdc lodi cd nay phat trifin dgt chieu cao tdi 2m, fainfa thdnh cdc bui cd, ra hoa va cho hat rit nhifiu. Nhu vay, cfai sau mpt thdi gian ngdn cdc khu vyc trfing da bj nhiing lodi c6 than ciing xdm chiem. Vao thdi ky mua kho, nhiing trdng c6 nay thudng hi dfit do chii y hogc vo y ciia con ngudi,
Kyyiu Hgi nghf Khoa hgc Dfa lp todn qudc ldn tha 7
Hoi Bia ly Viet Nam Dai fagc Thdi Nguyen
~Ket qua nghien cuu cho thay, nhiing khu vuc rimg bi huy diet bdi CDC thi sau do khong lau, dd da hinh thanh nhung HST nhan sinh voi tinh chat ciia cac quan xa than thao. Sau chien tranh a cho dfin hien nay, van chua cd boat dpng cai tao dat nao (thgm chi cd noi van chua rd pha xong bom min) Dien hinh trong sfi do phai ke den dia ban xa Linh Thugng, la mot trong nhiing noi chiu hau qua ngng ne nhit. Tgi day, HST trang co khong duoc thay dfii theo hudng tiiay the bdng HST rung tham chi nhifiu khu vyc cdn chua dgt tdi HST trang co cay byi. Dien tich HST trang c6 tren nen dat bi bao mdn d Gio Linh dgt tdi 12 OOOha trong tong so khoang 18.300ha HST trang cd, trang cd cay byi
Dieu dang luu y la trong dieu kien tu nhien, nhiing loai cay go tgo rirng lai phuc hdi dugc tren dat dfic bang dien thfi "man rimg - cua so". Cay rimg khong cd co che phat tan hgt ra cy ly xa Hat va qua cua mpt so loai cay chi cd the phat tan di xa nhd gid. Ddi vdi nhieu loai chim - chu the gieo hat, thi chiing can phai cd cho ddu, nhung d trang cd thi khong cd dieu ki6n nay. Tuy vay, theo quan diem cua chiing tdi, dieu ca ban la cay go riing nhiet ddi khdng cd kha nang phat taen tren nhung khu vuc trfing la do dgc diem sinh hpc ciia chiing.
Khac vdi cac loai cay go rimg, cdc Ioai cdy thugc nhom tien phong lai phat trien rat tot trong difiu ki?n nhiet dp, miic dg chieu sang gan vdi difiu kien d khu vyc trfing trai. Ket qud nghien ciiu d Gio Linh vd nhifiu khu vuc khac d Viet Nam trong khoang 20 nam qua cho thay, nhung loai thyc vat nay thudc cac hp, Araliaceae (Don chau cfaau Aralia armata), Euphorbiaceae (Sdi tia Sapium discolor, Sdi trang S. sebiferum, 14 loai thugc chi Macaranga, trong do 6 Mien Nam cd lodi dgc trung Ba soi long sao M. trichocarpa va 30 Ioai thudc chi Mallotus); Lauraceae (Mang tang Litsea cubeba); Melastomataceae (14 loai thugc chi Melastoma, trong do d Mien Nam cd lodi Muoi an bich M osbeckoides); Ulmaceae (Hu day long Trema orientalis. Hu day T. velutina), Rubiaceae (Gao tdu Anthocephalus chinensis); Rutaceae (Ba chgc Euodia lepta, Cdc hdi Zanthoxylum rhetsa);
Shnaroubaceae (Kho sam nam Brucea javanica); Verbenaceae (khong duoi 26 loai thupc chi Callicarpa).
Ket qua nghien ciiu ciing cfao thay, trong dieu kien binh thudng, sau 1 miia mua, cac lodi Macaranga trichocarpa, Trema velutina,
Anthocephalus chinensis da co chifiu cao tdi 150cm. Trong khi do, chieu cao ldn nhat khi trudng thdnh cua 2 lodi Macaranga tnchocarpa, Trema velutina la 8m, cdn ioai Anthocephalus chinensis la 20m. Sau mot tfadi gian smh trudng ngan cay da ra hoa, ket trai (Juan sat thyc te cho tfaay, Trema velutina da ra hoa chi sau 3 thang sinh trudng. Vdng ddi cua cac cay tien phong, theo udc tinh cua chiing toi, Id tii 10 dfin 15 nam. Hang ndm, cac cay tien phong deu ra trdi va rat sai qua, tuy vay khdng thiy nhiing cay con cua chiing mgc ngay dudi tan cay me. Nhiing
^loM-gdy tien phong ke tren tfaudng cd mat d nfaiing "cua sfi" rimg, tren nhung noi rimg hi khai thdc chgn vd ca nhiing bai trong, Tgi (jio Lmh ciing nhu nhieu vimg bj rdi^CDC d Mien Nam Vi?t Nam, cac cay go tien phong mpc quanh, bao bgc lay
rang cay thdn cao, hinh thdnfa mgt ddi dem, cdn ggi Id ddi chuyen tiep rit dgc thii giiia rimg tu nhien (cd the nguyen sinh) vd cdc quan xa cd, thyc vat dgng savan (hinh 2), Chifiu rgng cua ddi (dmyen tiep dao ddng phfi bien trong khoang.3 dfin 7m. Cac cay tien phong vdi toe dp sinh trudng Kpyiu Hdi nghf Khoa hgc Dfa lp todn qudc ldn tha 7
Hinh 2. Cdy gd ttin phong trong ddi chuyin tiip rimg vd qudn xa cd
MOI tlia ip Viet Nam Dai hoc ThdnVg"yg" j nhanh, cd vai trd quan trgng la bao ve be mgt dat tranh hi biic xa mat trdi vd trdnh bi nude mua ao , mdn. Ddng thdi, day ciing la con dudng khdi phyc lai nhung tham so vi khi hau d sat mat dat rung!
(ldp khdng khi tii 0 den 20cm). ^ j Dudi tan nhimg cay go tien phong, theo thdi gian (3 - 4 nam), mam ciia nhung loai cay phat tan til phia rimg cd the se phat trifin tot. Trong ddi chuyen tifip, da phdt hien mam vd cay non cua cac loai Thanh nganh Cratoxylum formosanum (Clusiaceae), Ko nia Irvmgla malayana (Irvingiaceae), Sao den Hopea odoraia. Sen cat Shorea roxburghu (Ditperocaipace^) vd^Cam 1 Pannari annamense (Chrysobalanaceae). Qua trinh nay dien ra tii khi nfairng canh tiiap nhat cua tan cay tien phong dgt tdi do cao 1,5 - 2m each mat dit. Song^song vdi sy ldn len ciia cdc loai cay go rimg, tdn cfae do cdy tien phong tao ra trong ddi chuyen tiep bj chia cat, mgc du cay rimg mdi chi dat tdi dd cao ciia ldp cd. Ddi bong ram do eay go rimg^tgo ra cimg vdi cay non trong ddi chuyfin tiep dan day lui ranh gidi cua cac quan xa cd vd tgo difiu ki?n md rgng dien tich phia dudi tiiuc vgt rimg Sy bifin doi dan dan dieu kien vi khi hau dudi tan cay^tiieo hudng tiep cgn vdi ca;
tiiam so VI khi hiiu trong rimg, cimg nhu sy xuit hi?n gan khu vuc dat trong. Nhirng cay den tiioi tnrdng tiidnh, ra hoa kfit qua thuoc ldp tren cung cua rimg, se tiuic day qua trinh kfadi phyc rimg cay nhiet ddi ban dia tai khu vyc do. Tuy nhien, qua trinh "quay trcr lgi" ndy cua cac lodi cay tiiupc tang tren cimg cda tan rimg (cho du chi Id mgt so loai nao dd) dien ra trong tfidi gian rit dai, khodng tii 50 den 80 nam. Trong dieu kien tfiyc tai tgi Gio Linh ciing nhu nhieu vung khde d Viet Nam, do mfii quan he "con ngudi - rimg nhiet ddi", qud trinh dien tiie nhu vay da vd se rat khd dien ra, yi nhu tiiudng thiy, hoat dpng cua con ngudi khong ngimg gay ra nhiing tdc dgng tiSu cyc len cac khu vyc nay.
a Gio Linh, cac cay thugc ddi chuyfin tiep khong cd khd nang xam lan tiianh di6n tich rgng ldn kfai hoan todn khdng cd cay rimg ban dia. Nhung noi nhu vay chi xuat hi?n nfaiing dgi dien don
\t vd hiem khi gap nhiing cym 3 - 7 cay ddi chuyfin tifip. Ben trong nhung cym cay nhu vay, dudi tan ciia chiing khdng dien ra qud trinh phyc hfii cdy rimg. Cay dai chuyfin tifip khong chen lin dugc vdo ting cd ram nq), khdng pfadt trien duoc tren nen dat bi bao mdn, nia troi, d6 la nhung noi ma thdnh phan ly - hoa cua dit da bi thay dfii, thgm chi mgt so noi dd hinh thanh ldp vd feralit rdn chdc kfadng faoac it tham nude Nfau vgy, qud trinh cgnh tranh sy song cua nhung cay go co khd nang sinh sdi d kfau vyc phyc hfii ben trong rimg, nfaung lgi khdng cd khd ndng ton tgi dugc o nfaihig khu vyc hi mit rimg, khong faoan todn thod man khdi ni^m "tien phong" da timg dugc thira nhgn. Day Id nfaiing cay chi ton tai dugc trong difiu ki^n chuyfin tiep, hay con goi la chuyfin tifip sinh thai.
Khde vdi cay gd, cdc lodi cd hodn todn co khd ndng xdm lin nhiing khu vuc trong trdi. Tren nen dat viia lg ra sau khi rimg bi mat, cung nhu dat hi bdo mdn, rira troi Id dieu ki§n thich hgp cfao cac lodi cd vd duong xi phdt tnen. Hat cua nhieu loai cd de dang phdt tan nha gio, cdc bo pfaan dudi dat cua chiing pfaat trifin rat mgnh vd mim tdi tao ciia chiing van tfin tgi dugc sau nhung tran chdy rimg. Tren kfau vuc rimg da bi tan pha, hinh thanh cdc quan xa cd dgt tdi cyc ^ n h vfi khi hau. TrSn dia fainfa vyng dong bang, gd dfii d Gio Linfa, trong nfaiing quin xa nhu vay chiem uu the van Id cac lodi cd cong to va ciing. Qua trinh dien thfi ciia tiiam thyc vdt tifip tyc dien ra trong chu trinfa nfau vgy neu nfau kfadng co nhung dot bifin vfi dieu kien ty nhien hodc bien phap ky thuat tii phia con ngudi.
KETLUAN
Trai qua^tfidi^gian ddi, chiu nhung tac dgng cua CDC cung nhifiu tac dgng nhan sinh khac nhau da j ^ n b i e n dgi eg bdn tfayc vat ciia nhifiu HST ty nhien huygn Gio Linh, tgo nen nhung HST nhan sinh cd ciu tnic dan^gidn. Trong do, HST trang cd cay byi va HST rimg nhan sinh la nhimg HST dgc trung cua lanh thfi vdi sy bifin doi mgnh me cua nhieu yeu to ciu tiianh.
Cau true HST rimg nhan sinh d Gio Linh cfaua dat den dp on dinh va co nhifiu khde bi?t, pfay tiiupc vdo miic dg tic dgng vd vi tri cua chiing: Trong HST rimg tini sinh, tii^ tiiuc vdt co ting tan chua on dinfa, nfaieu day leo nfaung d mgt so khu vyc da cho tiiay sy phan hod vdi 3 tang chii dgo
Kpyeu Hot nghi Khoa hgc Dia lp todn qudc ldn thu 7
Hpi flia l>^ ViSt Nam Dai hoc Thdi Nguy£n ucrlidne cd, trang cd cdy bui c6 cau triic dan gian, voi thanh phan gdm chu yfiu la cac Ioai cd than to va Cling. - ^ .A „ ..
Theo xu hudng dien tfae, trong dieu kien hien tai, khd nang phuc hoi cua rimg la hoan toan cd the dien ra tgi nhung ddi chuyen tiep giira rimg va trang cd cay bui, song toe dp rat cham chap. Sd di cd dieu nay la do trong HST bi pha huy dang ton tai nhung yeu to tdi ban ma tham thyc vgt rimg khdng cd kha nang phat sinh va ton tgi, trong do cd che dp nhiet - am cua khdng kfai va dat, dd chieu sang va su bien dfii cdc yeu to theo mua.
De CO the khai thac, sit dung va cai tgo nhiing dien tich rpng ldn trang cd, trang cd cay bui hinh thanh sau chifin tranh d Gio Lmh, can cd nhiing bien phap ky thuat thich hop; trudc tien Id bien phap cdi tao difiu kien mdi trudng khu \ a vyc.
TAI LIEU THAM K H A O
1. Phiing Tuu Boi va rmk (2002), "Anh huong cua chien tranh hod hoc (1961 - 1971) doi vdi tdi nguyen rimg Nam Viet Nam", Bdo cdo cdc cdng trinh khoa hoc tgi Hdi nghi khoa hoc Viet - My v^t^foxiM, HaNpi.,tr 145 -155
2. Pfaam Hodng Hp (1999), Cdy cd ViitNam. tgp 1,2 va 3. Nxb TP Ho Chi Minh.
3. Nguyen Dang Hpi (2000), "Uhg dung phuang phap danfa gia tong hgp cho viec khai thac, su dung hgp ly va bao ve tdi nguyen rimg", Tgp chi Khoa hoc Ldm nghiip, (Sd 1+2), tr. 31-34,
4. Nguyen Dang Hgi, Trin Van Thinh, Vu Van Lien (2001), "Tac dgng tieu cyc cua chien tranh hod hgc len tai nguyen mdi tnrdng tu nfaien huyen Sa Thay tinh Kon Tum", Tuyen tap Hoi nghi khoa hoc Tdi nguyen vd Moi trudng Viit Nam, Nxb Khoa hoc - Ky thugt. Ha Ndi, tr. 173 - 183.
5. Nguyen Dang Hoi, Kuznetsov A.N (2012), Nghiin cuu hiin trgng vd biin ddi cdc he smh thdi tu nhien dudi tdc ddng ctia con ngudi vd chiin tranh hod hgc huyin Gw Linh - Cam Lg, linh Qudng Tri. Bao cao de tai khoa hpc cap Uy ban phoi hgp Vi?t - Nga, HaNoi.
6. Kuznetsov A.N., Kuznetsova S.P, Phan Luong, Nguyen Dang Hgi (2009), "Nghien ciiu tac dgng ciia chat diet cd va bom Napal len rimg nhiet ddi gid miia d Mien Nam Viet Nam", Bdo cdo khoa hoc tgi Hdi nghi khoa hoc todn qudc ldn tha 3 vi Sinh thai vd Tdi nguyin Sinh vgt ndm 200P,Ha Ndi, tr 1390-1396.
7. Vd Quy, Phan Nguyen Hfing va nnk (2004), "Hau qud lau dai cua chien tranh hod hgc doi vdi moi trudng, tai nguyen rimg vd da dang smh hpc d Viet Nam", Kp yiu Hdi nghi Khoa hoc vi Tdi nguyin va Mdi trudng 2003-2004, Trung tam Nghien ciiu Tai nguyen va Mdi trudng, Dai hgc Qufic gia Hd Ngi,
8. Thai Vdn Trimg (1993), "Phuc hoi nhiing h$ sinh thai rimg bi chat diet cd huy hoai d mifin Nam Vi6t Nam", Bdo cdo khoa hgc Hdi thdo Qudc ti ldn 2 vi chdt diit cd trong chiin tranh. Ha Npi, tr 120-128.
9. Van phdng Chuong trinh 33 (1999), Tap bdn dd phum rdi chdt diit cd ciia qudn ddi My trong chiin tranh a Viet Nam, Hd Ngi,
10. Martin Van den Berg et all (2002), 'Tac dpng cua cac hgp chit dang dioxm vd PCB Ien cudc song hoang da: Li$u cd cdn mot vin dfi toan cau khong?", Bdo cdo cdc cdng trinh khoa hgc lgi H6i nghi khoa hgc Viet - My vi dioxin, Ua'M6i.,tT 616 - 621.
Kpyiu Hdi nghi Khoa hgc Dia ly todn qudc ldn thu 7
