KHOA HQC C Q N G NGHfi
PHAIVI L O A I D A T RIJIVG SUY THOAI VA D|IVH HUOIXIG GIAI PHAP KY T H U A T LAIVI SII\IH
Ph?mri v a n Didn*, Ph?un X u i n H o i n \ Dd Anh Tiiin^
T6MTAT
Giai ph^p ky thu$t lam sinh n^o phu hop vdi dIt rung suy thodi b nude ta? Dl giii quylt vIn dl niy, cin thilt phai phSn loai dc^t rung suy tho^ thinh cdc nhdm ddng nhit vl khi nSng phyc hdi. Bii bio da phin tich s6 lieu tr^n 117 6 ti^u chudn djnh vj phin bd b cic viing sinh thii khic nhau. Ddi tupng nghidn ciiru li dSlt da mit rung ty nhifen la rdng thudng xanh, vdi cic muc dd khic nhau. Ca sd khoa hpc dl phin loai dIt rung la dua vdo mdi quan hi cua lupng tSng trudng vl sd ciy tii sinh cd triln vpng vdi nhOng nhin td chii ylu cin thanh dilu kien l|ip dja cua tung Id d^t. Mdt he thdng bang tra don giin vi dl ip dyng vl cich xic djnh dilm sd cua nhCmg nhan td c6 anh hudng tdi kha ning phyc hdi cua Id dIt da dupe thilt lip trfin co sd chuyin doi tir phuong trinh todn hpc. C6 ba d p bilu thj khi nftng phyc hdi ciia dIt da mit rimg li A (tdO, B (trung binh) va C 0<lm). Tuong ung vdi ba c^p kha nang phyc hdi niy li 3 nhdm giii phip ky thuit lim sinh tac dOng, gdm: khoanh nudi tii sinh ty nhi^n (cho nhdm A), khoanh nudi tii sinh cd tic ddng (cho nhdm B) va cai tao rimg (cho nhdm C). VI m$t khoa hpc, bii bao cd y nghia li bd sung tb&m mdt sd thdng tin vl mdi b6n he giua kha nang phyc hdi cua rimg vdi nhung nhin td dilu kiln lip dja cd inh hudng chii ylu. VI mat thyc tiln, bai bao gdp phin vao viec xdy dyng hudng din ky thuit vi quin ly, chi d^o, giim sit cic c6ng trinh lam sinh, nhim phyc hdi va phat triln rimg ty nhifin li rdng thudng xanh theo hudng 6n djnh, bin vung va cd hieu qua cao.
Til khda: Dat rimg suy thoai, giai phip ky thu$t lim sinh, khi ningphpc hdi, phin lofu dit rimg suy thoii, rimg tu nhidn li rdng thudng xanh.
LDATVAND^ bdi c i n h d i giao d I t c h o h d gia dinh ngudi din Hien nay nude ta cd x i p xi 3,1 trieu hec ta dat (Pbam X u i n H o i n , 2010).
khdng cd rimg ( J o n g cue Lam nghiep, 2010), trong D l g d p p h i n giai q u y l t vIn d l niy, vide phSn dd chu yeu la dat do m a t rimg t u n h i l n l i rpng loai v i djnh h u d n g giii p h i p ky t h u i t lam sinh cho tiiudng xanh. Day la mdt ddi tupng cd nhu c i u d p dIt rimg suy thoii (degraded forestiands) l i rIt cin tiiilt cin dupe phuc hdi b i n g c i c giii phip ky tiiuit tiiilt v i cd y nghia. Mijic tiiu ciia nghiln cihi niy la lam sinh phu hpp, n h i m rut ngin thdi gian tiiinh til x u l t b i n g p h i n lo?d tilm n i n g phyc hdi ciia Id djit rimg v i tilt kilm kinh phi. D l thiic d l y c i c ho^t tii m i t rimg; d l x u l t bang tra v i djnh hudng giai ddng phuc hdi rimg trIn dat rimg suy thoii, n h i phip ky thuit l i m sinh t i c ddng cho timg nhdm 16 nude da ban h i n h nhilu quy pham ky thuit, nhu dIt rimg d i p h i n lo^i.
QPN 06-84, QPN 14 - 92 v i QPN 21 - 98. Mpt sd t i c L BCil TUQItt VA PHUQItt niAP NGHfill CUU gia cung d l cap tdi phin loai dIt rimg thu sinh n h i m i . Y)6i tuxjvig nghidn ciiu
muc dich d l xult giai p h i p ky tiiuit phuc hdi rung. ^^^ j ^ , ^ nghiln cuu l i nhiing d i e didm cua dit nhu Vu Tiln Hinh v i Pham Vin Diin (2005). P h ^ ^.^ ^^y ^ ^ . ^degraded 6>restlands) thudc kidu Xuan H o i n (2010). T u y n h i l n , d i n nay v i n chua ning nhidn lii^ng thudng xanh bcAc vimg smhm phan loai dat rung suy tiioii tiieo tilm ning phyc hdi ^h^^ „hau. Dit rimg tiioii hda chinh li dIt di mit mdt cich cd he tiidng, vira cd tinh bao quit, l?d vira ^img, dupe hinh tiiinh do kit qui cua qui tiinh suy cu till. Nhirng quy pham ky tiiuit hidn cd chi dimg thoii rimg h; nhidn (TTIX). 2002; David Lamb vi Don lai d nguyin tic chmig, nIn tiong nhilu tiirdng hpp Q^^^^^ gOOS; Wil de Jong, Do Dinh Sam, Trieu Van chung da dupe hiiu vi ip dting rIt khic nhau giua n^^^ 2OO6)
cac dia phuong (Vu Tiln Hinh, 2005). Hiln tai vin chua xay dung dupe he thdng bien phip ky thuit hpp ly cho phuc hdi rimg trIn timg Id dit cii thi vi tiong
Theo QPN 6-84, dit rimg suy thoii dupe chia
thinh: i Kilu IA: die trung bdi lop cd, lau lich ho^
chudi rimg, cd thi cd mdt it ciy tii smb.
- Kilu Ig: die trung bdi lop cay bui, cd thi cd mdt sd cay tai sinh.
Kilu Ic: die tnmg bdi cay thin go tai sinh vdi so lupng cay cd chilu cao trIn 1 m dat tir 1000 cay/ha trd len.
2. Phuong phip nghidn ciiu
-Bdtrid tidu chuan, kd thira vi thu thip sdlidu Kha ning phuc hdi ciia mdt Id dit cd mdi liln hi chit che vdi dilu kien lip dia cua nd (David Lamb and Don Gilmour, 2003). Vi vay, vin dk: miu chdt cua viec bd tri d tiiu chuan la cin bao quit trIn cic Id dit cd dilu kien lap dia khic nhau, vdi cic miic dp phuc hdi hay suy tiioii khic nhau. Cin cii vio su biln ddng cua nhimg nhan td chii ylu ciu thinh dilu kiln lap dia, nhu chi sd mua Im, dilu kiln dia hinh - th6 nhudng vi mit dp cay tii sinh, ngudn gdc ciia Id dit, da kl thira tong sd 117 d tiiu chuIn djnh vj phin bd d nim viing sinh thii vdi cic miic dd suy thoii vi dilu kiln lip dia khic nhau cua dit rimg suy thoii, gdm:
+ 35 d tiiu chuan dinh vi (1000 mVd) cua Vu Tien Hinh frong giai doan 2002 2005 vi sd Ueu nghien ciiu tren nhirng d tiiu chuan niy ciia Pham Van Diin trong nim 2006 d ba tinh: Son La, Bic Kan, Ha Giang (tren co sd lua chpn tir 154 d tiiu chuan dinh vi mi sd cay tai sinh cd trien vpng chua dam bao thinh rimg).
+ 22 d tiiu chuan dinh vi (400 mVd) ciia Pham Van Diin trong giai doan 2001 - 2004 d tinh Hda Binh
(tren co sd lua chpn tir 32 d tiiu chuan dinh vi mi sd cay tai sinh cd triln vpng chua dam bao thinh rimg).
+ 60 d tiiu chuan dinh vi (1000 mVd) ciia trudng Dai hpc Lim nghidp (vdi sir tham gia ciia Vien Dilu tra Quy hoach Rimg) tiong giai doan 2006 - 2010 d tam tinh: Hda Binh, Hi Giang, Nghd An, Ha Tinh, Quang Ngai, Thira Thiln Hul, Kon Tum vi Die Ndng.
Cic chi tiiu dilu tra dupe kl thira vi do dim true tilp gdm: dp cao tuydt ddi. vj tri tiln sudn ddc.
' dp ddc. hudng phoi ciia cic d tiiu chuln. cic tinh '' chit vit ly. hda hpc dit, cac nhin td ciu titic vi dai lupng sinh trudng ciia tang ciy cao, mat dp vi cic d^
' lupng sinh trudng cua cay tai sinh, tiiinh phin loii va dp che phii ciia ciy bui tiiam tuoi. Cic chi tiiu niy
\ dupe dilu tia tiieo phuong phip lam hpc, mdi nim dilu tra mdt lan vio cudi miia sinh trudng.
Lupng mua binh quin nim va chi sd khd ban d timg dia phuong dupe xac dinh theo phan mem sinh khi hiu cua Vuong Vin Quynh (2007).
- Xir ly sdlidu
Ddi vdi dit rimg thii sinh, nhilm vu trudc mit la phuc hdi chiing thinh rimg, chua cin thilt phai phan biet chue ning sin xult vdi chiic ning phdng hd.
Theo tiiu chuln nginh, Id dit dupe cdng nhin thanh rimg khi mit dd ciy tii sinh cd triln vpng dat tdi thilu li 500 ciy/ha. Ciy tii sinh cd triln vpng la cay gh thudc loii muc dich, cd chilu cao tir 2 m trd lln, cd phim chit tir trung binh din tdt (Quylt dinh sd 46/2007-QD-BNN).
Vi viy, kha ning phuc hdi ciia mdt Id dat nao dd dupe thi biln thdng qua chi tiiu sd nim (n, nim) nd dat hoic vupt tiiu chuln dupe cdng nhin thanh rimg:
n(nim) = (500-N,.2j/ANt, (1) Trong dd, N>.2n, li mit dp ciy tii sinh cd triln
vpng (ciy/ha). ANtv li ting trudng cua mat dp ciy tii sinh cd triln vpng (ciy/ha/nim).
Vin dl dit ra li can du bio ANt^ dua trIn cic nhin td ciu thinh dilu kiln lip dia ciia Id dat cho trudc. Phuong phip giai quylt li thilt lap quan hi ctia ANtv vdi bdn nhdm nhin td cd inh hudng quan trpng gdm:
Khi hau. thu nghiem cic nhin td lupng mua binh quan nim (P, mm/nim, tinh bmh quin trong 5 nim), dp am khdng khi binh quin nim (W, %), chi sd mua am K = P/(S + A), trong dd: S li sd tiiang khd; A li sd thing ban d dia diem nghien ciiu. Theo cdng thuc chi sd khd ban ciia Thii Vin Trimg (1976, 2001), d Viet Nam, S + A > 0 trong mpi trudng hpp.
Dfa hinh. thu nghiem cic nhin td dp cao tuyet ddi (Htd. m), dp ddc mit dit (a, dp).
- Dat thii nghiem cic nhin td dp diy ting dat (d, cm), dd xdp ting dit mit 0 -10 cm (X, %), him lupng mim trong tang dit 0 - 20 cm (Mu, %).
Thim thpc vit hidn cd. thu nghiem cic nhin td:
mit dp ciy tii smh cd triln vpng (N>.2„,. ciy/ha).
chilu cao binh quin ciia nhiing ciy tii sinh cd triln vpng(H.m).
Sii dung phuong trinh tuong quan da biln de md ta mdi liln h i ciia ANjv (nhin td sinh trudng) vdi cic nhin td sinh tiiii theo dang tdng quit
ANtv = F(K, Htd, •. d, Mu, N, H) (2)
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 7/2011 85
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Qui trinh tinh toin dupe tiiuc hien bing phuong phap thir nghiem cic dang phuong tiinh khic nhau vdi to hpp cic biln sd khic nhau dupe dua vio tiieo phuong phip thim dd timg budc (Stepwise), sau dd chpn ra phuong trinh phii hpp nhit. Phuong tiinh phii hpp nhit li phuong trinh tiida min nhOng dilu kiln sau (Nguyin Hii Tult, 1982; Chiang, C. L, 2003;
David A. Freedman, 2005; Good P. I. Hardin J. W, 2009):
- Cd he sd tuong quan (r) hoic he sd tuong quan kip (R) cao nhit vi nd tdn tgi.
Cd he so biln ddng cua phuong trinh tuong quan (V%) vi hi sd chinh xic ciia phuong trinh tuong quan (P%) nhd nhit.
- Cic tham sd ciia phuong trinh tuong quan tdn t^i.
- Don giin nhit, dl ^ dyng nhit, cd it biln sd nhit Trong cdng trinh niy, chpn phuong trinh tirong quan cd it biln sd nhit vi thda min dilu kiln:
R (R2) > 0,900
V < 10% (3) P<5%
Dp tin ciy cua cic tiiu chuln kilm tra li 95%.
Theo cic quy pham ky thuit lim smh hiln hinh vi tinh hinh thuc tl, cd thi xic dinh thdi gian khoanh nudi tii smh tu nhiln cho mpi ddi tupng dit rimg suy thoii (phdng hd vi sin xult) li 7 nim, nIn tir(l)vi(2)tacd:
Nlu n =< 7, ip dung giai phip khoanh nudi khdng tic ddng, tiic li sd Ipi dung khi ning tii sinh tu nhiln dia Id d i t
Nlu 7 < n =< 11, ip dung giai phip khoanh nudi cd tic ddng, tiic li vira Ipi dung khi ning tii sinh txf nhiln ciia Id dit, vira tic ddng thim dl nit ngin thdi gian thinh rimg.
Nlu n > 11, ip dt^ng giii phip cii t?io rimg, tiic li thay thi tham thtrc bi hiln cd bing mdt thim rimg khic vdi si; can thidp ciia con ngudi.
Dl tiiuin tiln cho viec ip dung ciia ngudi din, cin don giin hda cich xic dinh giai phip lim sinh can ip dung cho timg Id dit trong khi khdng lim giam ding kl dd chinh xic ctia nd. Dl giii quylt vin dl nay, mdt y tudng dit ra li su dt^g phuong phip chIm dilm cac tiiu chi vi diing tdng dilm ciia cic tiiu chi dl phin loai dit rimg thii sinh. Phuong phip nay dupe thuc hiln nhu sau:
Xic djnh su ting lln ciia sd nim (n) khi timg
lin ting lln giiia hai d p bin tilp ciia nhung nhan td ly. Diy li co sd cho vile chIm dilm cic tiiu chi.
Phin lo^i tdng dilm ciia cic tiiu chi thinh ba d p dl tgo ra ba nhdm dit rimg suy thoii ddng nhit vl khi ning tt; phyc hdi thinh rimg. Diing phuong trinh tuong quan dl xic dinh ngudng ciia timg dp tdng dilm.
Kl thira kit qui nghiln ciiu ciia Pham Xuin Hoin (2010) dl dl xult djnh hudng ky tiiu$t lim sinh cho timg nhdm ddi tupng dit rimg suy thoii da dupe phin lo^i.
•.KfTQUA NGHiN Oiu
1. Phin lo^i dit rimg suy thoii
Hiln nay cd mdt sd hpc gii d l nghj ring, vile phin lo^ dit rimg d l lim co sd cho cic giii p h ^ tdc ddng cin dt^a tiln cic tiiu chi vl ci ky thuit vi kinh tl - xi hdi. Quan dilm trong nghiln oiu niy li, chi sir dyng nhung tiiu chi ky thuit dl phin lo^i, cdn nhtmg tiiu chi vl kinh t l xi hdi sd dupe sir dting cho vile xic dinh loii muc dich vi d l xult biln ph^
kinh doanh rimg.
Khi ning ti; phuc hdi ciia nhdm loii ciy chii ylu dupe bilu th} thdng qua nhilu chi tiiu, nhu lupng ting trudng thudng xuyIn hing nim vl trir lupng g§;
si; biln ddi vl sd lupng ciy tii sinh cd triln vpng; su thay ddi vl thinh phin vi sd lupng loii; dd phi vi dd Im cua dit rimg; v.v...Tuy nhidn, chi tiiu trxfc tilp vi quan trpng nhit d i dupe thira nhin li su thay ddi vl sd lupng cua dy tii sinh thudc nhdm loii chu ydu chuydn Idn ting ciy cao ho^c st; thay ddi vl sd lupng cda ciy tii sinh cd tridn vpng theo thdi gian frong giai do?ui phyc hdi (VQ Tiln Hinh vi Ph^un Vin Diin, 2005). Trong hai chi tiiu dd, chi tidu thir hai dxiqc cdng trinh Ivta chpn vi su dving d l d^ didn cho kha ning phyc hdi cua nhdm loii ciy chii ylu, vi nd phu hpp vdi die dilm cua dit rimg suy thoii. Chi tiiu nay cung dugc Bd Ndng nghidp vi Phit triln ndng tiidn diing lim tidu chi d l xic dfnh rimg khoanh nudi tiiinh rimg (tiieo Quylt djnh s6 46/QD-BNN-20a7).
NhOng nhin t6 cd inh hudng quan tipng t6i ANtv gAm: khi h^u, dia hinh, thd nhudng vi tiiam thi;c v^t Nlu chpn cing nhilu nhin td dl dua viao phuong trinh tuong quan thi he sd tuong quan cua phirong trinh cing cao nhung mdt sd tham sd cd thi khdng tdn tai. Bing phuong phip so sinh gifia ck phuong trinh vi ddi chilu vdi dilu kidn (3), di chon dupe phuong tiinh phu hpp nhit li: ANt, = 12,230BI
+0,00649.K.d/a + 0,08089. N>2™ - 0,000035. N^gm (4)
Trong dd, N^^ li niat dd ciy tai sinh da trudng thinh thudc loai muc dich.
(R = 0,891, F(ti„h) = 843,3 > F05 o,^),
Sig.tai < 0,05, V^^ = 13,2%, Vj^ = 8,7%;P = 0,804%) Phuong trinh phiic tap nhit da dupe tiiu nghiem
la phuong trinh vdi su tham gia ciia 9 biln sd cd R = 0,983.
0 phuong trinh (4) tit ca cic tham sd aj diu tdn tai, nghia li ANjv phu thudc rIt chit vio cic nhin td nlu trIn.
Nhu viy, trong tiiuc tl d i tdn t^ mdi Uln h i giua ting trudng vl sd ciy tii sirtii cd triln vpng vdi cic nhan td cua dilu kiln lip dia. Tir diy cd thi lip dupe bang tra sd nim (n, nim) tu phuc hdi thinh rimg ciia Id dat bit ky dua trIn bdn nhin td cua dilu kiln lip dia tai Id dit ly (bang 1).
Bang 1. Sd nim ti; phyc hdi thinh ritng ciia Id dit (trich din mdt sd tinh hudng ngiu nhidn)
a(dd) 15 25 25 35 15 15 25 35 15 15 25 25 35 15 25 25 35 25 15 25 35 35 25 15 35 35 35 40
d (cm) 50 75 100
75 100
75 100
75 100
50 75 50 50 100
75 100
50 25 75 100
75 100
75 25 50 50 25 25
...
K 500 600 500 600 700 600 700 500 600 700 700 500 700 600 700 400 700 500 500 500 700 500 400 700 500 400 500 400
...
N>-2m (cay/ha)
500 480 500 500 400 400 400 400 300 300 300 300 300 200 200 200 200 200 100 100 100 100 100 100 100 100 100 0
...
n (n&m) 0 0 0 0 1 2 2 2 3 4 4 5 5 6 7 8 9 10 11 12 13 14 14 15 16 17 18 36
Theo bing 1, thdi gian tu phuc hdi cua cic Id dat dl cham ngudng bit diu dupe cdng nhan thanh rimg li tir 0 - 36 nim., Dilu nay cd thi xay ra trong dilu kien nhiet ddi Im thudc vimg phin bd cua rimg la rdng thudng xanh vi khi dit rimg khdng tilp tuc bi phi hoai nira.
N>2n, li nhin td quan trpng nhit trong td hpp khi hiu - dia hinh - tiid nhudng - tiiam thuc vit Nlu N>2„
> 270 ciy/ha, tiii n < 7 vdi mpi td hpp cua K, a vi d.
Nlu N>2m < 270 ciy/ha, tiidi gian phuc hdi tiiinh rimg cua timg Id dit nhanh hay chim li phu thupc vio td hpp ciia K, a vi d. Dilu dd cho thIy ring, trong pbgm vi nhit djnh, cic nhin td d u thinh Id dit cd thi bii trir cho nhau hoic han chi tic dung ciia nhau, qua dd cd inh hudng din tdc dd phuc hdi rimg.
Theo cdng thtic (1) vi phuong trinh (4), ling vdi mdi trj sd cho trudc ciia N>2„ si xic djnh dupe tri sd ciia td hpp CK.d)/a dl tiida man dilu kiln cua tri sd n. Ta cd:
K.d ao*aiN..i„-arN^
N>..
2m 500a
=Z (6)
a. "a,
Tiiu chuln dl dit rimg suy thoii phuc hdi thinh rimg trong thdi gian khdng qui 7 nim li:
(Kd)/a > Z7 (tuong ting vdi n = 7 trong cdng thiic
(6)). (7) Tiiu chuln dl dit rimg suy thoii phuc hdi
tiiinh rimg trong thdi gian tir 7 11 nim li: Zu <
(K.d)/a < Z7 (Zu tuong ting vdi n = 11 trong cdng
tiiirc (6)). (8) Tiiu chuln d^ dit rimg suy thoii phuc hdi
thinh rimg trong thdi gian Idn hon 11 nim li:
(K.d)/a<Zu. (9) Trong thtrc tiln, to hpp ciia cac nhin td d u
tiiinh Id dit rIt da dang, nen vile ip dung bang tren cung gip nhilu khd khin. Dl thuan Ipi, can xiy dung tiilm mdt phuong phip khic, dd li phuong phip chIm dilm. Cin cu vio phuong phip chuyin ddi ttr phirong trinh tuong quan thinh dilm sd ciia cic biln sd, di xiy dtmg dupe cic bing sau: Bing tra dilm ciia tham tin;c vit (bang 2), bing phin logi tilm ning phyc hdi ciia tiiam tiiuc vit (bang 3), bing tra dilm cic tiiu chi ciia dilu kiln lip dja (bang 4), bang phin loai tilm ning lip dia (bang 5).
a. Phan loai tidm ning phuc hdi cua tham tiiue vit
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 7/2011 87
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Bing 2. Bing tia dilm ciia thim thytc vjt
Tifiu chi
Mat do cay tAi sinh c6 tri^n vpng (N^.jJ
Thang til sd
<100 100-<190 190-<270 270-500
K^hieu
Nl N2 N3 N4
Dilmsd 10 17,7 28,6 87,5
Theo quy dinh, ngoii tiiu chi mit dO ciy tii sinh ylu ciu dl ra ddi vdi tiiu chuln cdng nhin rimg CO triln vpng thudc loii muc dich phii d?it tir 500 khoanh nudi tiiinh rimg.
cay/ha trd lln, cdn c6 mdt dilu kiln nGa li chilu cao binh quin cua nhimg ciy tai sinh niy phii dat tir 4 m trd len. Kit qua phin tich sd lilu dilu tra d tiiu chuln dinh vi da cho thiy:
Ciy tii sinh (nlu cd) trdn dit di mit rimg li rpng thudng xanh dupe chia tiiinh hai nhdm. Nhdm tiiii nhit gdm nhirng loii tm sing, tii sinh ddng loat, mat dp biln ddng Idn giua cic khu d i t cd kich tiiudc kha ddng nhat (trir nhung ciy gd cdn sdt lai). Nhdm thir hai gom nhung loai ciy muc dich, chju bdng, mit dp biln ddng Idn giua cic Id dit, tii sinh khdng ddng loat, nIn cd kich thudc khic nhau khi Idn.
Neu mat dp cay tii sinh cd triln vpng dat xIp xi 400 500 ciy/ha, phin bd N-U^ ciia chiing cd d ^ g nhilu dinh, chilu cao pho biln tir 2 - 5 m. Mat dd ciy tai sinh cang Idn, chilu cao binh quin cua chiing cing tilm cin vdi tri sd 3,5 - 4,5 m. Kit qua phin tich sd lieu tren 3 d tiiu chuan dinh vi d Son La cd N>.2n, bing 480, 520 vi 560 ciy/ha da cho thay, chilu cao binh quin cua chiing biln ddng tir 3,87 4,35 m, dip ung dupe
Nlu mit dd ciy tii sinh cd tiiln vpng thIp (dudi 200 ciy/ha), thi chilu cao binh quin ciia chiing chi d^t tiln ngudng 2 m (vi chi tinh tir ciy c6 chilu cao 2 m tid lln). Tuy nhiln, vl logic, nhiing 16 niy se tilp tuc dupe tic ddng vdi thdi han nim tiong khoing tiidi h?ui khoanh nudi (ti-ong ph^m vi 6 7 nim). Vdi ting tiirdng chilu cao nhu di hilt (0,3 - 0,5 m/nim), nhirng Id dit niy cd till dip img dupe ddng tiidi hai tiiu chuln cdng nhin rimg hoin tiiinh khoanh nudi.
Bing 3. Phin lo^i tilm ning phyc hdi dia thimtiiycvjt
Tdng dilm
>28,6 17,7-28,6
10-17,7
<10
d p tilm nang tham thuc vat
1 2 3 4
Dinh gia RIt tdt
Tdt Trung binh
Kem b. Phin lo^ tidm ning lip dia
Bing 4. Bing tra dilm cic tidu chi ciia dilu kidn Ijp dja TieudW
1. Khi hau (K) K=P/(S + A)
2. Dja hinh (a)
3. D^t (d)
Than£tris6 300-<400 400 - < 500 500-<600 600-<700 700-<800
>.35 25-<35 15-<25 8-<15
<8
<50 50-<100 100-<150
>-150
IC^hieu Kl K2 K3 K4 K5 al a2 aS a4 a 5 dl d2 d3 d4
Dilm 10.0 10,7 11,5 12.1 12,8 10,0 10.8 11,8 12,8 13,7 10,0 11,5 12,2 12,6 Bing 5. Phin lo^i tidm
Tdng dilm
>37,8 35,1-37,8 33,7-35,1
<33,7
Cip tilm ndng lip dia
I II 111 IV
ning lip dia Dinh gii RIt tiiuin Ipi ThuSnlpi it thuan Ipi Khdng thuin Ipi
c. Xic dinh td hpp cda thim thyc vit vi diSu kidn lip d/'a
VI ca 1^ tiiuylt lin tiiuc tiln, cd till xay ra 16 td hpp cua tiiam tiiuc vit vdi dilu kiln \^p dja (bang 6).
Trong bang 6, cd ba d p tilm ning phuc hdi ciia 16 dit li A (tdt), B (tiimg binh) vi C (kdm)'.
Bing 6. Bing tra tilm ning phyc hdi ciia Id dit Cap tiem
nang phuc hoi cua tham
thuc vat 1 2 3 4
Cip tilm nSnj? iSp dia
I 11 III IV
Cap tiem nang phuc hoi cua Id d^t
A A A B
A A B C
A B B C
A B C C
Su sai khic vl kit qua xic dinh d p tilm ning phuc hdi cua Id dit tir bing 6 so vdi tir phuong trinh tuong quan (4) vi cic tiiu chuln (6), (7), (8) chi xiy ra khi mit dp ciy tii sinh cd triln vpng cua Id dit cd tri sd gin bing vdi tri sd thudc ranh gidi cic d p phin chia mit dd ciy tii sinh. Nlu trudng hpp niy xay ra thi cd thi giii quylt bing d c h ting tri sd N>2n, thim 5%, sau dd tra lai vio bing 3 vi 6. Nlu kit qui cua hai lln tra khic nhau, thi su dyng kit qui d miic tdt hon (ching ban, chpn A trong A vi B; chpn B trong B vi C. Tuy nhiln, theo thdng kl, nhung trudng hpp niy chi chilm xIp xi 5%, nIn cd thi bd qua.
2. D}nh hudng giii p h ^ ky thuit lim smh cho timg nhdm ddi tupng dit rimg suy thoii
Khoing thdi gian cin thilt d l hoin tiiinh tii sinh tu nhiln li co sd quan trpng nhit de quylt djnh giii phip khoanh nudi rimg ciing nhu xic dinh ky han ^ dyng giii phip niy. Ky ban khoanh nudi li khoang tiidi gian tir khi ip dyng biln phip khoanh nudi din khi Id dit dat tieu chuln hoin tiiinh khoanh nudi. Tuy theo tinh trang ban diu ciia dilu kiln khi hiu, dia hinh, tiid nhuong, tiiim thuc vit vi bien phip ky tiiuit tic ddng mi tiidi gian khoanh nudi phuc hdi rimg cd thi dii hoic ngin khic nhau.
Vdi mdt ddi tupng nio dd mi thdi gian niy qui dii, viec ip dyng giii p h ^ khoanh nudi tii sinh tu nhiln li khdng cd hidu qua vi nd can dupe tiiay till bing cac giii phip khoanh nudi cd tic ddng hoic giai phip cai tao rimg. Nlu chpn thdi gian khoanh nudi tii sinh tu nhiln li 7 nim, tiii cic giai phip ky tiiuit lim sinh dupe dl xult trong bang 7.
Bang 7. Bing tia giii phip ky tiiuit lim sinh tic ddng
Cap tilm n&ig phuc hdi cua 16 dat
B
Giai phap phyc hdi rimg Khoanh nudi tai sinh ty nhi6n
Ochdng tac ddng)
Khoanh nudi tai sinh cd tac ddng Cai tao rimg
a. Khoanh nudi tii sinh tu nhidn
+ Ddi tupng ip dyng: nhdm chua thinh rimg, gdm ci ddi tupng sin xult vi phdng hd diu ngudn cd d p tilm ning phyc hdi A
-I- Nguyin tic, ylu ciu ky thuit
Sii dyng giai phip khoanh nudi tu nhidn ("Khoanh ddng") lim co ban, Ipi dyng ning luc gieo gidng tu nhiln, niy chdi gdc vi dim chdi rl ciia ciy rimg trIn Id dit, dl din din hinh thinh rimg, chuyin dit khdng cd rimg thinh dit cd rimg, qua dd dat dupe myc dich phyc hdi rimg.
Lip hd so, ddng mdc bing phin dinh ranh gidi rd ring, giao cho chii rimg dl quin ly bio vl cd hieu qui.
Xic dinh, lip danh lye loii ciy myc dich, phi myc dich.
Ngin chin chin thi siic vit ban chi khai thic ciii, ban chi cit cd. Trong trudng hpp can thilt phai xiy dung chdi canh, bing can lua xanh hoic tring hay hing rio, bio ngin chin nan chin thi tu do. Td chiic tdt vile tuan tra canh gic.
Phai xic dinh thdi ban ip dyng giii phip khoanh nudi tai sinh tu nhiln. Khi rimg khoanh nudi di khep tin, dupe phep chuyin sang ip dyng giii phip nudi dudng hoic lim giiu. Din thdi ban xic dinh mi rimg van chtra phyc hdi, nlu cd dii dilu kiln kinh tl - ky tiiuit tiii chuyin sang ip dyng giii phip cii tao rimg.
b. Khoanh nudi tii sinh cd tic ddng
+ Ddi tupng ip dyng: nhdm chtra thinh rimg, gdm ci ddi tupng sin xult vi phdng hd diu ngudn cd d p tilm ning phyc hdi B.
+ Nguyin tic, ylu ciu ky tiiuit
Thuc hiln tiieo QPN 14 - 92 (xiic tiln tii sinh txx nhiln, Dilu 59 - 66) hoic tiieo QPN 21 - 98 (khoanh nudi xiic tiln tii sinh tu nhiln kit hpp tidng bd sung).
Xuc tidn tii sinh bing hat tiong timg tiang thii tiiim tiiuc vit cy till, cd till ip dyng mdt hoic ddng tiidi cic biln phip dudi diy:
Xii ly dit eye bd bing phuong phip tiiii cdng, cudc rinh hay d y phay cho hat gidng dupe viii trong d i t sdm niy mim, trinh su phi hoai cua cdn trimg, ddng vit Bien phip niy phii hpp vdi mdt sd loii
NONG NGHIEP VA PHAT TRIEN NONG
THON- KY 1 - THANG 7/2011
89KHOA HQC
C Q N GNGHfi
thdng, mpt sd loii ciy ua sing, h?it nhp vi nhilu nhu con tiln cic Id tidng cd diin tich tiln 1000 m?, tia cheo, vdi thudc vi mpt sd ciy hp Diu. chdi, lo?u bd ciy phi myc dich.
Xii ly ciy byi, thim tuoi khi di sin cd Idp ciy Ludng phit diy leo vi ciy byi inh hudng din tai sinh nhung hi chin Ip. Vile xir ly tiiyc hien 1-2 sinh tinidng ciia ciy tii sinh myc dich cd triln vpng lan trong 1-2 nim cho din khi ciy tii sinh vupt khdi tiln ti)in bd diin ti'ch.
su lie chi cua ciy byi thim ttroi. Biln phip niy dupe ip dyng chu ylu trIn cic tring cd ciy byi vi nuong riy bd hoi. Trong mdt sd tnrdng hpp, cd thi phit ludng ciy byi thim ttroi tnrdc miia hat ryng.
Ddi vdi nhimg loii sdm ra hoa kit qui, qui vi hat nhilu. dl tii sinh, dupe phip tidng ciy hoic khdm ciy rii ric hay trIn nhung vj tri thuin Ipi cho vile phit tin h?it gidng dl xiic tiln tii sinh ty nhiln.
Xuc tidn tii sinh ti/nhidn bing ciy chdidxiqtc ip dyng ddi vdi nhung rimg cd cic loii ciy cd khi ning tii sinh chdi gdc, chdi rl, chu ylu nhim sin xult gd nhd, hoic cic chiing lo?ii gd khic phii hpp vdi phim chit gd do tii sinh chdi. Ddi vdi loii ciy cd khi ning tii sinh chdi phai tin dyng tdi da phuong thirc niy di nit ngin chu ky kinh doanh, ha gii thinh tii t^o
Xdi dit, vun gdc ciy tii sinh cd triln vpng bin kinh 0,5 m.
Chit sit gdc ddi vdi ciy tii sinh b} dip, gay dl tgo ra ciy chdi khod m^nh.
Dinh tia, di chuyin vi tidng dim ciy tii sinh loii myc dich.
Trdng bd sung ciy bin dia vio nhung khu vvrc thilu hoic khdng cd ciy tii sinh. Mit dd tidng bd sung thudng biln ddng tir 100 - 400 ciy/ha.
- Cd till thilt lip vinh dai xanh cd chilu rdng tir 3 hing ciy trd lln, chilu dii theo toin bd hoic mdt phin chu vi ciia Id rimg.
c. Cii tao rimg
+ Ddi tupng ip dyng: nhdm chua thinh rimg, gdm ci ddi tupng sin xult vi phdng hd diu ngudn c6 rung.
Xuc tidn tii sinh tu nhidn bing bidn phip tdng *^^P ti^"™ " ^ ^ P^tiC hdi C.
hap gdm: ^ Nguyin tic, ylu d u ky thuit
Loai bd mdt sd ciy phi myc dich, cin trd smh Thyc hidn tiieo Quy ph^m thilt k l kinh doanh trudng cua ciy myc dich nhim dilu chinh td thinh rimg (QPN 6 84), quy ph^un ky thuit cii t?io rimg nhdm ciy gh, kich tiiich hat gidng niy mim vi tiiuc (2007/QE)-BNN).
dly sinh trudng ciy tai sinh. . Cd till cii t?io rimg bing mdt tiDng hai phuong Ludng phit diy leo vi ciy bvii inh htrdng din phip: chit tring trdng l^i ho^c ti-dng rimg trudc. ch$t smh trudng ciia d y tii sinh myc dich cd triln vpng h? sau.
trIn toin bp didn tich. + ch$t ti^Ing \xhx\z l?u: ch$t ti)an bd tiiam rimg - Dinh tia, di chuyin vi trdng d$m ciy tiii sinh cO, sau dd mdi tiln hinh ti-dng rimg.
loii myc dich. + Trdng rimg tiudc, chit h? sau: diu tiln tiln Xdi d i t vun gdc ciy tii sinh cd triln vpng bin hinh ti-dng rimg dudi tin rimg cu, sau khi cd tiiln kinh 0,5 m. vpng thinh rimg, mdi tiln hinh chit bd Idp tiiam
Chit sit gdc ddi vdi ciy tii sinh b} dip, giy dl tao ra ciy chdi khoe manh.
Trong trudng hpp cin thilt, cd till thilt l|ip vinh dai xanh cd chilu rdng tir 3 hing ciy gd trd Idn, chilu dii theo toin bd ho$c mdt phin chu vi ciia Id rimg.
Khoanh nudi xiic tidn tii sinh kdt hpp trdng bd sung. Cic biln phip ky thuit tic ddng trong giii
Cd thi cii t?io trdn toin didn tich, hoic cai tao theo dim, tiieo bing. Nlu cai t^o theo dai/bing, cin chia didn tich khu cai t^o thinh cic dai/bing, khai thic xong tiln hinh trdng rimg, sau khi chic ch^
thinh rimg sd khai thic tin dyng cic dai/bing cdn chita 1^ vi tilp tyc trdng rung.
Tidu chuln lya chpn loii ciy trdng cai tao cho rimg san xult d n xem xdt ddng thdi cic tidu chu&
phap nay co ^i^ su dyng ti,ng hpp cic bien phip vl gii til kinh t l vi tiij tiiidng lim sin, kha ning chim soc, tiuoi dudng hoic xuc tiln ^ sinh, nhu ^ ^ m canh vi nit ngin chu ky kinh doanh, kha ning
nghi vi tii sinh, khi ning bio vl vi cii thien mdi trudng sinh thii.
Tiiu chuan lua chpn loii ciy trdng cii tao cho rimg phdng hd dau ngudn:
+ Chiu ban: d noi cd ban hin d n chpn loii cd tinh chiu han cao de sinh trudng dn dinh, dl sdng thinh rimg.
+ Tieu tdn it ntrdc: tuy In chpn loii ciy cd ty 11 tiiu hao nude do sinh tnrdng, thoit hoi nude vi hoc hoi nude trIn mdt don vj thi tich cua ciy tirong ddi nhd, dl giim bdt tiiu hao nude cho khu vuc.
+ Cii tao d i t d noi dit xlu, ting dit ndng, d n tuyIn chpn loii ciy cd thi cii tao d i t nhu loii ciy cd khi ning cd dinh dam.
+ Uu tiln loii ciy dia phuong vi loii ciy cd philn li nhd, ciy li kim. Loii ciy dja phirong tuong ddi thich ling vdi dilu kiln khi hiu, dit dai ciia dia phuong, nIn sinh trudng dn dinh. Ciy cd philn li nhd, ciy li kim cd tic dyng giim thilu kich thudc gipt nude dpng khi roi xudng, nIn ban chi xdi mdn d i t
+ Gii trj kinh tl: loii ciy cd siic sin xult nhit dinh, cd thi mang lai Ipi ich vl mit kinh tl, cung d p cic lim sin ngoii gd, tao dilu kiln thuin Ipi cho canh tic, nudi ong,... dupe ngtrdi din vi cdng ddng dia phuong quan tim phit triln.
Tieu chuln ciy con dem trdng: tiiu chuln chung li ciy con cd sinh luc tdt (qua quan sit ngoai hinh), sinh trudng binh tiiudng; khdng cyt ngpn, nhilu thin hoic nhilm siu bdnh hai.
Khuyin khich cai tao rimg bing cic loii ciy ban dia cd gii tri kinh t l cao, mpc nhanh vdi ngudn gidng dupe cii thiln.
Ngoii d c quy pham vi hudng dan ky tiiuit hien hinh, khi cai tao rimg bing ciy ban dia can chii y thim hai vin dl, gdm: cin cir vio ylu d u vl dd tin che ciia ciy ban dia tiieo tudi di xic dinh tiidi dilm dua ciy vio trdng dudi tin ciy mpc nhanh vi xic dinh ky tiiuit xu ly tang ciy cao.
IV. KET LUAN
- Co sd dl phin loai dit rimg suy tiioii dupe dua tiln kha ning ti; phyc hdi ciia nd, tiidng qua mdi Uln he ciia su gia ting sd lupng d y tai sinh cd tiiln vpng hang nim (AN J vdi bdn nhdm nhin td d u tiiinh dilu kiln lip dia ciia Id dit cd anh hudng quan tipng toi nd, gdm: chi sd mua Im (K = P/(S + A)), dd ddc
mit dit (a, dp), dd diy ting dat (d, cm) vi mat dp ciy tii sinh cd triln vpng hiln cd (N>.2n„ ciy/ha).
- d p tilm ning phyc hdi cua Id dat li to hpp d p tilm ning phyc hdi ciia tham thuc vat vi d p tilm ning lip dia. Cip tilm ning phyc hdi cua Id dit dupe chia thinh ba d p : tdt (A), trung binh (B) vi kem
(C). Vile phin loai tilm ning phyc hdi cua Id dat dupe thuc hiln bing phuong phip chIm dilm trIn CO sd chuyin ddi tir phuong trinh tuong quan thinh dilm ciia cic d p biln sd.
Djnh hudng giii phip ky thuit lim sinh tic ddng cho dit di mit rimg gdm ba giii phip: khoanh nudi tii sinh tu nhiln (cho d p A), khoanh nudi tii smh cd tic ddng (cho d p B) vi cii tao rimg (cho cIpC).
Trong thyc tiln, vile dilu tra xic djnh bdn nhin td: K, a, d, N>2n, li tuong ddi don gian. Vile tra dilm ciia timg nhin td cung nhu vile xic dinh tdng dilm ciia td hpp bdn nhin td cung di ding, nIn phirong in phin loai dit di mit rimg tir kit qui nghiln ciiu niy cd tinh kha tiii, cd thi ip dyng vio thuc tiin. Ngoii ra, vile chIm dilm cic nhan td theo timg thang bic di tinh toin din su biln ddng ciia chiing cung nhu inh hudng ciia su biln ddng ly tdi chi tiiu bilu till khi ning phyc hdi ciia Id dat (ANJ, nen phuong in phin loai dit rimg suy thoii cung dim bio dp tin ciy.
TAILtUniAMKHAO
1. Vu Tiln Hinh, Pham Vin Diin, 2005. Bio do kdt qui nghidn cuu cic giii phip phuc hdi rung bing khoanh nudi a mdt sd tinh phia Bic Vidt Nam. Dl tii KHCN Bd Ndng nghilp vi PTNT.
2. Ph^im Xuin Hoin, 2010. Bio do kdt qui cdng trinh hudng dan ky thuit lim sinh ip dung cho rimg tu nhidn phuc hdi sau khoanh nudi Cdng tiinh KHCN Tdng eye Lim nghiep.
3. Vuong Vin Quynh, 2007. Bio do kdt qui nghidn cm inh hudng cda mdtsd kidu thim tiiue vat rimg ddn dc nhin td khi hiu, tiiuy }^in vi dat, tu dd xiy dung phin mdm smh khi hiu. Dl tii KHCN Bd Ndng nghidp vi PTNT.
4. Tdng eye Lim nghidp, 2010. Quydt dfnh sd 2140/QD-BNN-TCLN ngay 09 thing 8 nim 2010 vd vide cdng bd didn tich vi dd che phd cua rimg tinh ddn 31/12/2009
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 7/2011 91
KHOA HQC CbNG NGHfi
5. Tran Hiiu Viln, Pham Vin Diin, Nguyin 7. ITTO, 2002. Guidelines for restoration, Minh Thanh, 2010. Bio do kdt qui nghidn cuu management and rehabilitation of degraded and xay dimg phuong in didu chd rung ti/ nhidn li secondary tropical forests. ITTO policy rpng thudng xanh li rimg sin xudt d Vi^t Nam. development series. No 13. 86 pages.
^i tii KHCN Bp Ndng nghilp v i PTNT.
6. David Lamb and Don Gilmour, 2003.
Rehabilitation and Restoration of Degraded
8. Wil de Jong, Do Dinh Sam, Trieu Van Hung, 2006. Forest Rehabilitation in Vietnam histories, . . -. .. .^.^ ' 7 ' j o -J 1 j ° J rea/rtoes a/7(//i//Mre Center for international forestnr
Foresrts. lUCN, Gland, Switzerland and ' Cambridge. UK in collaboration with WWF- '^^^^""^ J'' ^^^^^R, situ Gede, Sindang Barang
Gland. Switzedand. 122 pages. Bogor Barat 16680, Indonesia.
CLASSIFICATION OF DEGRADED FORESTLANDS AND ORIENTATION OF SILVICULTURAL PRACTICES
Pham Van Dien, Pham Xuan Hoan, Do Anh Ttian Summary
Which silvicultural practices are suitable for degraded forestlands in Vietnam? In order to solve this problem, it is necessary to classify degraded forestlands into homogeneous groups based on the rehabilitation capacity of foresUands. This article analyzes the database of 117 permanent sample plots distributed in the different ecological regions of Vietnam. The objects of the study are degraded evergreen broadleaf forests at different levels of degradation. Scientific foundations for classification of degraded forestiands are based on the relationship between increments of number of potential saplings Avith the key important factors of forest sites. A simple and applicable table for determining the weighted values of forest site factors is set up fi"om a predicted mathematic equation. There are three levels of rehabilitation capacity of degraded forestlands: A (good), B (average), and C (bad). Correlatively, three silvicultural systems are made up for each group of degraded forestiands, including restoration through natural regeneration (for group K), assisted natural regeneration (for group B), and forest reclamation (for group C). Scientifically, the article provided important understanding on the relationship between the rehabilitation capacity of degraded forests and the key factors of forest sites. From practical perpective, this article contributes to establishment of technical and managemential guidelines, to conduction and supervision of sihdcultural works, aiming at better management of evergreen broadleaf natural forests in a simple and effective way by application of the simple table on the rehabiliation capacity of the degraded forestiands.
Keywords: Degraded forestiand, silvicultural practice, rehabilitation capacity, classiScation of degraded forestiands, evergreen broadleaf natural forest
Ngudi phin bidn: PGS.TS. Vd D^ii Hii