^ Lam hgc
QUAN HE K H 6 N G GIAN CUA CAY RlfNG SAU KHAI THAC CHON
THEO KHOANG CACH VA DlTOfNG KINH CAY
Nguyen Hong Hai
Trirang Dgi hgc Lam nghiep
TOM TAT
Mpt trong nhijng muc tieu chinh ciia nghien ciiu smh thai rimg la tim hi6u cac co ch£ va qua trinh da diSu ti^l phan bo, dp nhieu va quan he ciia cay rimg. Nghien ciru nay so sanh can true khong gian ciia cac trang thai rimg sau khai thac la tac dpng manh (HIL) va tac dpng trung binh (MIL) voi trang thai chua khai thac (UL) theo tang tan de tim ra nhiing co che va qua trinh smh thai co ban nhdt dang diln ra trong lam phSn. Tren moi trang thai rirng, ! 6 tieu chuan 1 ha dupc thiet lap va dieu tra ducmg kinh ngang nguc (dbh), chieu cao, ten loai va tpa do tuong doi ciia tat ca ca the cay co dbh > 2,5 cm. Phuong phap phan tich mo hinh digm khong gian mpt bien so va hai bien so duoc sir dung de phan dch phan bo va quan he ciia cay rirng theo khoang each va kich thuac cay a ba tang tan rirng. duai tan, giua tan va vupt tan. Ket qua phan tich da chi ra dupc su 6n dinh ciia cay rimg doi vai trang thai UL, trong khi quan he canh tranh giira cay - cay dugc tim thiy 6 trang thai HIL va MIL. Lien he voi ly thuyet sinh thai cho thay mot so co che smh thai chinh co kha nang dieu chinh phan bo va quan he cua cay rimg nhu; chet phu thupc mat do, phat tan han che va ly thuyet trung lap. Anh hucmg ciia viec khai thac chpn trong qua khii da tao ra cac xao tron cau tnic khong gian ciia rimg tu nhien. Tir can cu nay, cac bien phap lam sinh co the duac de xuat de giam thieu tinh canh tranh, thuc day kha nang sinh truong va quan ly rirng ben vung.
Tir khoa: Ham tirvng quan daic tinh, ham tu'ong quan theo cap, khai thac chpn, phan tich mo hinh khong gian, rimg nhiet doi la rong thirong sanh.
1. DAT VAN DE
Phan bo khong gian ciia cay rimg da duac thira nhan la nhimg bang chiing ciia cac qua trinh da dieu chinh cau triic ciia quan the (He va cpng sir, 1997; Condit va cong sir, 2000).
Dua vao vi tri cua cac ca the cay (mo hinh diem - point pattern), phan tich mo hinh khong gian se cho biet mot nhom cay co phan bo dang cum, dang deu hoac ngau nhien; hai nhom cay c6 quan he la tirong ho, canh tranh hoac dpc lap vai nhau a nhirng pham vi nhat dinh trong khong gian. Ngoai ra, neu ket hop them cac dac tinh khac cua cay (vi du kich thuac cay: dirong kinh, chieu cao), quan he ciia nhimg cay lan can se dupc lam sang to vi trong rung ur nhien vj tri cay thuang co quan he vai kich thuoc ciia chung (Weiner va cpng su, 2001; StoU&Bergius, 2005).
Phan bo khong gian ciia cay rimg, dac biet la a rirng tu nhien nhiet dai, duac dieu chinh bai nhieu ca che sinh thai khac nhau nhu: canh tranh/tuang ho, phat tan han che, chet phu thupc mat dp va ly thuyet trung lap. Trong do.
canh tranh la ca che chinh cau tao nen quan the tir nhien va the hien thong qua qua trinh tu tia thua self-thinning (Tilman, 1994). Phat tan han che la mot trong nhimg ca che tao ra phan bo dang cum - la phan bo pho bien cua da so cac loai cay rimg (He va cpng su, 1997). Ly thuyet trung lap cho rang de tuong thich voi moi tnrcmg song, cac loai cay se co chuc nang tuong tu nhau vi the canh tranh gma cac loai khac nhau rat kho dupc nhan dien (Hubbell, 2006). Cac CO che sinh thai dang dien ra trong quan the deu de lai dau vet thong qua mat dp cay rimg thay doi a cac cap kich thuac cay va pham vi khong gian khac nhau.
Chirng toi so sanh cau true khong gian ciia cac trang thai rimg sau khai thac la tac dpng manh (HIL) va tac dpng trung binh (MIL) vai trang thai chua khai thac (UL) theo tang tan de tim ra nhimg ca che va qua trinh sinh thai co ban nhat dang diln ra trong lam phan, Chung toi gia thiet r4ng: cay rimg a cac tang tan duai co phan bo dang cum va canh tranh vai cay a tang tren la cac dku hieu a cac trang thai rimg sau khai thac
TAP THI KHOA HQC VA CONG NGHE LAM NGHIEP S6 3 - 2019 27
Ldm hgc
chpn. Ngoai ra, trang thai chua khai thac se c6 sir on dinh hon trong cau true khong gian.
2. P H i r O N G P H A P NGHIEN C i r u 2.1. Khu v\xc nghien cii-u va thu thap s6 lieu
Khu virc nghien cuu la Rimg thuc nghiem Kon Ha Nimg, huyen Kbang, tinh Gia Lai.
Rimg la rpng thuang xanh am nhiet dai tai khu vuc rimg thuc nghiem Kon Ha Nimg co dien tich xap xi 1.400 ha; trong do co khoang 100 ha thupc vimg loi chua khai thac. Khai thac chpn dupc thuc hien vao nhimg nam trirac 1980 tren nhirng quan thu co tru lupng go Ian hon 130 m^/ha. Duong kinh cay toi thieu dupc khai thac la 45 cm. Khai thac chpn dupc thuc hien voi cuang dp cao (khai thac 30 - 50% tru lupng), cuang dp trung binh (khai thac 20 - 30%
trir lupng). Sau nam 1980, toan bo dien tich nay duac trai thuc nghiem Kon Ha Nimg bao ve nghiem ngat phuc vu muc dich nghien ciru.
Khu vyc nghien cuu c6 nhiet dp trung binli nam la 23,6°C. Lupng mua trung binh nam khoang 2.042 mm. Miia mua keo dai tir thang 5 den thang 12 va chiem 90% tong lupng mua hang nam, mua kho keo dai tir thang 1 den thang 4. Dat chii yeu la dat nau tim dien hinh, dat do vang, dat do vang co tang set loang 16 va dat do vang tren da set va da bien ch4t.
Dp cao dia hinh xap xi 700 m so vai mirc nuac bien.
Vao nam 2018, ba 6 tieu chuSn 1 ha dupc thiet lap tren ba trang thai rimg: sau kliai thac tac dpng manh (HIL; tpa do 14° 10.475' Bac, 108°38.977' Dong), sau kliai thac tac dpng trung binh (MIL; tpa dp 14° 10.89' BSc, 108°39.277' Dong) va chua khai thac (UL; tpa dp 14°11.492' B5c, 108°39.938' Dong). Moi 6 tieu chuan dupc chia thanh mot luai 100 5 thu cap (10 X 10 m). Tren moi 6 thu cap, duang kinh than cay ngang nguc (dbh) tai vi tri 1,3 m, chieu cao viit ngpn (H), vi tri ciia cay (x,y) trong 6 va ten loai cay dupc xac dinh va do d^m cho tat ca cac cay than go co dbh > 2,5 cm. Vl tri ciia cac cay rieng le dupc xac dinh thong qua viec sir dung thuoc do khoang each
bang laser (Leica Disto D5) va la ban Sau do.
tat ca cac ca the cay dupc chia vao mot trong ba tiing tan: duai tan (H < 8 m). giua tan (8_^
H < 18 m), vugt tan (H > 18 cm) tlico each tiep can CLia Getzin va cpng sir (2011).
2.2. Xu' Iy so lieu
Phuang phap phan tich mo hinh diem khong gian (spatial point pattern analysis) dupc sir dung de phan tich su sap xep trong khong gian ciia cac ca the cay (Diggle, 2003). Trong nghien ciiu nay, chimg toi da dya vao vi tri (x,y) va duang kinh (dbh) cua ca the cay lam so lieu dau vao. Ham tuang quan theo cap (pair-correlation function) va ham tuong quan dac tinh (mark-correlation function-MCF) dupc sir dung de mo ta tinh chat cua mo hinh diem khong gian (spatial point pattern) trong mpt dai ciia khoang each (Illian va eong sir, 2008). Qua trinh mo phong da su dung mo hinh khong (null model) de mo ta gia thuySt khong (null hypothesis) cua mo hinh diem va sau do duac doi ehieu vai mo hinh thuc nghiem (Diggle, 2003; Wiegand & Moloney, 2004). Dp lech giira mo hinh thyc nghiem va mo hinh ly thuyet khong dupe su dung dk mo ta mo hinli thyc nghiem va tim ra cac qua trinh da dieu chinh mo hinh thuc nghiem.
Hdm titrmg quan theo cap
Ham Urang quan theo cap g{r) mo ta mat dp chuan hoa tai mot khoang each nhdt dinh /• va duac giai thich la mat dp ky vpng ciia cac di^m tai khoang each r tir mpt diSm bdt ky. Vai mpt loai diem (vi du: cay rimg a cung mpt t k g tan), ta co ham urong quan theo cap mpt biln so - g,,(r), day ciing la dao ham cua ham Ripley'K(Riplcv 1976):
/^(r) = 271 | , g ( r O r ' r f r '
0
h a y 5 ( r ) = | ^ for r > o Su(r) = 1 cho biSt phan bd hoan toan nalu nhien, g „ ( r ) > 1 cho bict phan bfl kilu gii(r) < 1 cho biet phan b6 Isieu deu tai i.u ' ' cachr. 'W khoang
28 TAP C H i KHOA H O C VA C O N G N G H E LAM N G H I E P SO 3 - 2019
Ham tuang quan theo cap hai bi6n so g\2{r) duac phat triin tir ham tuong quan theo cap mpt bien s6- Ham gnif) dupc sir dung de phan tich quan he khong gian giiia hai nhom diem khae nhau (vi du: cay rimg a hai tang tan).
Ham gnir) phan anh mat dp ky vpng cua cac diem nhom thu 2 tai khoang each r tir mpt diem bat ky ciia nhom thir 1. Neu guO') = 1, quan he la dpc lap (khong tuang tac); neu gn{f) > 1, quan he la tuong ho, nghia la eo nhieu hon cac diem nhom 2 tai khoang each r tu mpt diem bat ky ciia nhom 1 so vai ky vpng khi quan he la dpc lap; neu g[2{r) < 1, quan he la canh tranh tai khoang each r.
Hdm tuong quan dac tinh
Ham tuong quan dac tinh (MCF) (Illian va cpng sy, 2008) mo ta sy phu thupc giira dac tinh ciia cac cay (vi du: dbh) a khoang each r.
Gia thiet hai eay / vay each nhau mpt khoang r va CO dac tinh m, va w/. Quan he dac tinh dupc lupng hoa boi mpt ham kiem tra t{mi,mj). Dua vao tat ca cac cap cay each nhau mpt khoang r, uac lugng cua r-MCF dugc tinh nhu sau:
r . > ^ 1 Y.U^%M^i.mj)]k{\\xi-Xj\\-r) Trong do Ct la ky vpng cua ham kiem tra va A:f]|;c,-x,||-r^ la mot ham trung tam. Neu khoang each ||.v,-x,|| gan vai r, ham trung tam nhan gia trj 1, ngugc lai nhan gia tri 0.
Truang hop co mpt bien so, kmimi{r), sii' dung ham kiem tra t2{m„mj) ^ m, dupc chuan hoa bai gia tri dac tinh trung binh \x. Truang hgp CO hai bien so, kn,]m2{r), sir dung ham kiem tra l3{m„mj) = mj, trong do chi co gia tri dac tinh eiia nhom 2 dupc xem xet. Truang hop cae dac tinh la dpc lap vai nhau MCF ^ 1, neu MCF <" 1, thi cac dac tinh co tuong quan nghjch vai nhau va neu MCF > 1, thi cac dac tinh CO tuong quan thuan (quan he tuang ho) tai khoang each /-. Chang han, tuang quan nghjch (quan he canh tranh) xay ra neu cae eay each nhau mpt khoang r va se co gia tri cac dac tinh nho hon gia tri tmng binh (Illian va cpng sy, 2008).
Ldm hgc Mo hinh khong
Gia thuyet ca sa cha cac phan tich trong bai bao nay la cac dieu kien moi truang tai 6 tieu chuan la dong nhat. Bai vi didu kien moi truang khong d6ng nhat se anh huong d£n phan bo khong gian cua cay va lua chpn cac mo hinh khong phii hgp vai su khong d6ng nhat. Chiing toi da kiem tra tinh dong nhat nay dya vao phan bo khong gian ciia tat ca cae cay truang thanh (dbh > 10 cm) boi vi cay truang thanh co kha nang song phii kin cac dien tich dupc nghien ciiu va da trai qua giai doan chpn Ipc ty nhien kho khan nhat. Chat lugng moi truang song khong dong nhat (neu co) se phan anh thong qua phan bo khong dong nhat cua cay thanh thuc (Getzin va cpng su, 2008). Cac 6 tieu chuan nghien ciiu dugc xac dinh la dong nhat ve dieu kien moi truong. Vi vay, chiing toi da ap dung mo hinh khong gian hoan toan ngau nhien (complete spatial randomness CSR) cho ham mpt bien so va dpc lap (Independence) cho ham hai bien so de mo ta mo hinh khong gian.
Trong tat ca cac phan tich mo hinh khong gian, da thyc hien 199 lan mo phong Monte Carlo va sir dung 5 gia tri lan nhat va 5 gia tri nlio nhat de xay dyng khoang tin cay xap xi 95%. Su khae biet eo y nghia so vai gia thuyet khong la mo hinh thyc nghiem nam ngoai khoang tm cay. Sau do, phep kiem tra Goodness-of- Fit test dupc ap dyng cho mirc sai so < 5% de giam sai so loai 1. Tat ca cac phan tich khong gian neu tren deu dupc thyc hien tren phan mem Programita (Wiegand &
Moloney, 2004).
3. KET QUA VA THAO LUAN 3.1. Dac diem cau triic lam phan
KSt qua tinh toan cha thay tinh da dang loai va tru' lupng go a ca ba trang thai rimg deu rat cao (bang 1). So cay co duong kinh tir 2,5 cm dupc do dSm bien dpng UJ 1341 - 1551 cay.
Ion nhat a trang thai UL. Dp nhieu ciia loai trang thai bien dpng tir 83 - 115 loai cay, Ion nh4t la trang thai MIL. Duong kinh Ion nhat
TAP CHI KHOA HOC VA CONG NGHE LAM NGHIEP SO 3-2019 29
Ldm hgc
biln dpng tir 85,35 - 117,83 cm va chiSu cao Ion nhat biSn dpng rir 33 - 55 m. Ca ba trang thai rimg deu co trir lupng go r4t cao tir 408,47 (HIL) - 619,42 (MIL) m^/ha. Quan he giira
duong kinh va ehieu cao cay rimg o ba trang thai rimg dugc mo phong theo dang hai Logarit va cho thay deu a mirc rat chat vm K - 0,84 - 0,86 va gia tri p < 0,05 (Hinh If Bang 1. Mot so chi tieu cSu triic cua 03 trang thai rung
Chi tieu So cay So loai
Chieu cao Idn nhat (m) Duang Idnh Ion nhiit (cm) T6ng tiet dien ngang (m'/ha) Tm lirgng (m /lia)
HIL 1427 96 55 85,35 33,024 408,47
MIL 1341 115 40 105,41 46,127 619,42
UL 1551
83 33 117,83 43,791 570,28
Dl,3(cm) D13(cml D.I.J (cm)
Hinh I. Quan he giua dircmg kinh ngang nguc va chieu cao cua cay rirng & trang thai rijng (Khai thdc tdc dong manh - HIL (hinh la), Khai thdc tdc dong trung binh - MIL (hinh lb) vd
Chua khai thdc - UL (hinh lc))
3.2. Phan tich mo hinh khong gian mot bien so Ket qua phan tich mo hinh khong gian ciia ca ba trang thai rimg cho thay ham tuong quan theo cap mpt bien so ciia 3 tang tan (duai, giira va vupt tan) deu tiem can gia tri 1 trong khoang each 30 m (Hinh 2). Dieu nay chirng to ca ba 6 tieu ehuan deu dong nhat ve dieu kien moi truang. Ket qua tuang tu ciing dugc the hien thong qua ham m'ong quan dac tinh mpt biln s6 cho thay mite dp dong deu ve duang kinh ngang nguc ciia cay rimg a ca ba trang thaii-img(Hinh3).
Quan he ve khoang each giu'a cac cay rirng cho thay xu thi chuyen tir phan b6 dang cum sang phan b6 dang ngau nhien theo tang tan tir duai tan din vugt tan a trang thai rimg da bi tac dpng (Hinh 2a-f). 0 trang thai UL, tat ca cay rimg ciia ba t§ng tan diu co phan bo dang
ngau nhien (Hinh 2g-k). Nhu vay, eay rimg co xu huong phan bo ngau nhien khi kich thuac cay tang len o ea ba trang thai rimg dupc nghien cim.
Gia tri cua ham tuong quan dac tinh nho hon 1 o khoang each duai 3 m cho thfiy cay rimg a tang duai tan (Hinh 3a, g) va tSng vupt tan (Hinh 3c, f, k) co xu thi ire ehl lan nhau vl duang kinh. Xu thi canh tranh nay dugc thi hien tuang d6i ro rang a ca ba trang thai rimg.
0 tang giua tan, cay rirng chu ylu c6 quan he dpc lap vai nhau vc dirong kinh thi hien bai gia tri eiia ham tuang quan dac tinli x4p -i 1 a ca ba trang thai rimg Mac du c6 quan he canh tranh ire chi l§n nhau a ting duoi tan nhung cay rimg a tang giua va vuot tan cung cho thSy xu thi dich chuyin hi quan he doc 13«
quan he canh tranh ve duong kinh
30 TAP CHI KHOA HOC VA CONG NGHE LAM NGHIEP SO 3 - 2U19
Ldm hoc
V\/V^A'^>A/VV^
K h o i n g each r(m) Khodng cach r(m) Khoang each r i m )
Hinh 2. Quan he khong gian theo khoang each cua cay rung 6" ba tang tan cua ba tr^ng thai rimg (Khai thdc tdc dong manh - HIL (hinh 2a-c), Khai thdc Idc dong trung binh - MIL (hinh 2d-f) vd Chua khai
thdc - UL (hinh 2g-k). Duong mdu den Id mo hinh thuc nghiem, du&ng mdu xdm Id khodng tin cdy 95%)
l;"/A'V-Vv--Vvvv.,.,^ -,^^.v,^^:vvV~^~-v^^ -
Cj^^^^r^r-A^ :V^^^^^VW-^^>-^ l/~Jv^^:
Khoang cach r|m) Khoang c i c h F(in) Khodng c i c h r(m)
Hinh 3. Quan he khong gian theo duOTig kinh ciia cay rirng o" ba tang tan cua ba trang thai rung (Khai thdc tdc dong mgnh - HIL (hinh 3a-c). Khai thdc Idc dong trung binh - MIL (Iiinh 3d-J) vd Chua khai
thdc - UL (hinh 3g-k). Duong mdu den Id mo hinh ihirc nghiem, dir&ng mdu xdm Id khodng tin cgv 95%.) TAP CHI KHOA H O C VA C O N G N G H E L A M N G H I E P S 6 3 - 2019 31
Ldm hoc
Mac du quan he khong gian theo klioang each khong thi hien ro nhung quan he theo ducmg kinh cho thdy co bdng chimg ro rang cua sy eanh tranh ve moi truang song ciia cay rimg a ca ba trang thai rimg dupc nghien cim.
Sy chuyen doi tii' phan bo dang cum sang dang ngau nhien hoac deu ciia cay rimg 6 tang duoi tan den tang vugt tan dugc cho la ket qua ciia qua trinh chet phu thupc mat dp - density dependent mortality (Peters, 2003). Nliiing cay a tang tren co kich thuac lan hon the hien kha nang canh tranh manh hon cay a tang duoi (Peters, 2003; Picard va cpng sy, 2009).
Pelissier (1998) cung cho rang xu huang phan
bo deu cua cay truang thanh la dau hseu ciia sy canh tranh manh me giira cae ca the cay ' >'i nhau. Phan bo dang cum ciia ca\' rimg ^ hai trang thai rung da bi tac dpng cho thay nguyen nhan co the la viee khai thac chpn trong qua khu da tao ra cae 16 trong va tao dieu kien cho cay non phat trien vai mat do cao. Ngoai ra, phan bo dang cum con co the la ket qua ciia qua trinh phat tan han che - dispersal limitation (Condit va cpng sy, 2000). Trong klii do, phan bo dang ngau nhien 6 trang thai UL lai eho thay su on djnh trong phan bo ciia cay rimg a trang thai it bj tac dpng o ca ba tang tan.
3.3. Phan tich mo hinh khong gian hai bien so
Hinh 4. Quan he khong gian theo khoang each cua cay rirng giua cac tano Mn fi-.^ K f ^u '• ^ /^i .f- ,• .*" r rrr, „ • , A \ ,^, . , . . ^^^^ ^ ^ ' " ' ^ 3 i g tan cua ba trang thai rung (Khai thac tac dong manh - HIL (hinh 4a-c), Khai thac tac dgng trung binh - MIL (hinh 4d-f) vd Chua khai thdc - UL (hinh 4g-k). Dtrmig mdu den Id mo hinh thirc nghiem. du&ng mdu xcirn td khodng tin cgy 95%)
m ( h i n h 4 a - b ) Tuong tu o irang thai UL, cay rmig a tang tan thap han co phan b6 mat do cao xung quanh cay ting tren 6 khoanP each duo, 10 m (hinh 4g, k). Nguac Iai, o , r „ , MIL, cay duoi tan co xu thi phan b6 voj mat dp thap xung quanh cac cay tSng ircn 6 j^]^ - ' each til' 0 - 8 m va phan b l doc jjip ^ ° ^ " ^ khoang each Ion hon 8 m (hinh 4c-0, ' ^^'^
Phan tich mo hinh khong gian giira cac tang tan ciia cay rimg a ba trang thai rirng cho thay phan bo cay rimg a trang thai HIL va UL dpc lap hon trang thai MIL (hinh 4). (3 trang thai HIL, cay rirng a tang giira va duoi tan co xu huong phan bo vai mat dp cao xung quanh cac cay vugt tan a khoang each gan duai 1 m va phan b6 dpc lap a cac klioang each lan han 1
32 TAP CHI KHOA HOC VA CONG NGHE LAM_NGHIEP SO 3 - 2 0 1 9
a.Vi/TItinftGiOatin-l b,VuWtin&DLj'*i tir-H c, GlO'a tan & Di/di tan-MiL
\ j ; \ | W v y ^ ^ ^
; ; ^ v w \ p , ^ v ^ :
• ^d, Vi/^rt tan & Gi[}a tin-IV Tttan&DLro'i tan MIL f, GlO'a tan a Di/dn ta
t::.f>v^-vw ;:^^^^-^vvv^ ;:.w.:,^,.s^
W%r-'tK>s;Ar
Khoang cich r|ni) Khoang each r(m) Khoing cich r[ni|
Hinh 5. Quan he khong gian theo duong kinh cua cay rimg giira cac t^ng tan cua ba tr^ng thai rirng (Khai thdc tdc dong mgnh - HIL (hinh 5a-c), Khai thdc tdc dong trung binh - MIL (hinh 5d-f) vd Chua khai thdc - UL (hinh 5g-k). Duong mdu den Id mo hinh thuc nghiem, du&ng mdu xdm Id khodng tin cgy 95% )
Ket qua phan tich quan he khong gian theo duang kinh ciia cay rimg cho thay rang quan he nay la dpc lap trong khong gian a ca ba trang thai rirng. Nhu vay, khong co sy eanh tranh hay tuong ho eua cay rimg dupc the hien thong qua duong kinh cay giira cac tang tan voi nhau mae dii quan he nay dugc the hien ro rang hon thong qua khoang each cay - cay a hinh 3.
Quan he tuong ho theo khoang each ciia cay rirng giua cae tang tan a trang thai HIL va UL cho thay anh huong cua 16 trong va ca che phat tan han che den phan bo ciia cay non a tang tan duai lan can cay a tang tan tren. O trang thai MIL, cay non a tang duai tan co xu huang phan b6 tach rai cay a hai tang tan tren. Dieu nay cho the dugc giai thich la do nhirng cay non ua sang co xu the phan b6 vai mat dp eao a cac 16 tr6ng dugc tao ra do khai thac chpn nhirng cay go lan. Quan he dpc lap cua cay rimg nhiet dai c6 the dugc giai thich bo'i Iy thuyet trung lap - Neutral theory (Hubbell, 2006), theo do tinh da dang loai cao ciia rimg nhiet dai lam cho kliong loai nao chilm uu t h i
ro ret va lam suy giam tinh eanh tranh giira cac loai trong quan xa.
4. KET LUAN
Trong nghien cuu nay, phan tich m6 hinh diem khong gian mpt bien so va hai bien so dupc sir dung de so sanh cau true kh6ng gian ciia ba trang thai rimg la khai thac tac dpng manh (HIL), tac dpng trung binh (MIL) va chua khai thac (UL). Ket qua phan tich da chi ra dugc su on dinh ciia cay rimg doi voi trang thai UL, trong khi quan he canh tranh giiia cay - cay dugc tim thay o trang thai HIL va MIL.
Lien he vai ly thuyet sinh thai, mgt so ca che sinh thai chinh e6 kha nang dieu chinh phan bo va quan he cua cay rimg nhu: qua trinh chet phu thupc mat dp, phat tan han che va ly thuyet trung lap. Anh huong cua viec khai thac chpn trong qua khir da tao ra cac xao tron ciia cau tnic khong gian cua rirng tu nhien. Tii' can cii nay, cac bien phap lam sinh eo the dupc de xuat de giam thieu tinh canh tranh, thiic day kha nang sinh truong va quan ly rimg ben viing.
TAP CHI KHOA HOC VA CONG NGHE LAM NGHIEP SO 3 - 2019 33
Ldm hgc L61 cam on
Nghien cuu nay dugc tai trp bai Quy Phat trien khoa hpe va eong nghe Qu6c gia (NAFOSTED) trong D I tai ma s5 106-NN.06- 2016.22
TAI LIEU THAM KHAO
1. Condit, R., P. S. Ashton, P. Baker, S.
Bunyavejchewin, S GunaUlleke, N. Gunatillcke, S. P.
Hubbell, R. B Foster, A. Itoh, J. V. LaFrankie. H S.
Lee, E Losos, N. Manokaran, R Sukumar and T.
Yamakiira (2000). Spatial patterns in the distribution of tropica] tree species. Science 288(5470): 1414-1418
2. Diggle, P. J. (2003). Statistical Analysis of Spatial Point Patterns. London, Arnold (Hodder Headline Group).
3. Gelzin, S., T. Wiegand, K. Wiegand and F He (2008). Heterogeneity influences spatial patterns and demographics in forest stands. Journal Of Ecology 96(4). 807-820.
4. Getzin, S , Worbes, M., Wiegand, T., & Wiegand, K.. (2011). Size dominance regulates tree spacing more than competition within height classes in tropical Cameroon.
Journal of Tropical Ecology, 27{\), 93-102.
5. He, F L., P. Legendre and J. V. LaFrankie (1997). Distribution patterns of tree species in a Malaysian tropical rain forest. Journal of Vegetation Science 8(1): 105-114.
6. Hubbell, S. P. (2006). Neutt'a] theory and ihe evolution of ecological equivalence Ecology 87(6) 1387-1398.
; in three
•3\ moist I-I6 7- Illian, J., D Stoyan, H. Stoyan and A Penttmen (2008) Statistical Analysis and Modelling o^ Spat'a Point Patterns. Sussex, Wiley.
8 Pelissier, R. (1998). Tree spattai paitcii contrasting plots of a southern Indian trnp e\'ergreen forest. Journal of Tropical Ecolog> ' ^
9 Peters, H. A (2003). Neighbour-regulated mortality: the influence of positive and nogatne density dependence on tree populations in specie^-nch tropical forests. Ecology Letters 6(8): 757-765.
lO.Picard, N., A. Bar-Hen, F. Mortier and J.
Chadoeuf (2009). Understanding the dynamics of an undisturbed tropical rain forest from the spatial pattern of trees Journal Of Ecology 97( 1): 97-! 08
11. Ripley, B D. (1976). The Second-Order Analysis of Stationary Point Processes Journal of Applied Probability 13(2): 255-266
12.Stoll, P. and E. Bergius (2005) Pattern and process: competition causes regular spacing of individuals within plant populations. Journal Of Ecology 93(2): 395-403
13. Tilman, D. (1994). Competitton and biodiversity m spattally sttucture habitats Ecology 75(1): 2-16.
14. Weiner, J., P. Stoll, H. Muller-Landau and A.
Jasentuliyana (2001). The effects of density, spatial pattern, and competitive symmetry on size variation in simulated plant populations. American Naturalist 158(4): 4 3 8 ^ 5 0 .
15 Wiegand, T. and K. A. Moloney (2004). Rings, circles, and null-models for point partem analysis in ecology. Oikos 104(2): 209-229.
SPATIAL ASSOCIATION OF FOREST TREES AFTER LOGGING BASED ON THEIR DISTANCES AND DIAMETERS
Nguyen Hong Hai
Vietnam National University of Forestry S U M M A R Y
One of the principal objectives m forest ecology is to understand mechanisms and processes regulating distribution, abundance, and association of forest trees. Our study compares the spatial structure of logged forest stands including high impact logging (HIL) and medium impact logging (MIL) to the unlogged forest (UL) based on canopy stones to identify the most important underlying mechanisms and processes. On each forest stand, one ha plot was designed and measured diameter at breast height (dbh) tree height species and relative coordmates of all trees with dbh > 2.5 cm. Methods of umvanate and bivariate spatial point pattern analysis were used to analyze distribution and association of forest trees based on their distances and diameters on three vertical strata: understorey, midstory and overstorey. The results showed stationary of trees in UL while competition between tree-tree was found in HIL and MIL. Relevant ecological theories showed that principal mechanisms may regulate tree disrtibution and association such a. dependent mortality dispersal limitation and neutral theory. Effects of selective logging m the past distuibed spatial structure of these natural forests. Based on these findings, silvicultural treatments may be applied to ri-d-r,. .-r,^ *•,,
rr'^^.'i-^'LUi.iLL competitive interaction
facilitate productive increment and sustainable forest management ' Kevwords: Mark correlation function, pair correlation function, SCILUIVP I>»I.,;.„^ .. . . . . . J. j - r - . ' - ' c '"liging, spatial Dattern
analysis, tropical broadleaved rain lorest. *^
Ngay nhan bai Ngay phan bien Ngay quySt djnh dang
: 05/4/2019 : 21/5/2019 : 29/5/2019
34 TAP CHI KHOA HOC VA CONG NGHE LAM NGHIEP s 6 3-2019
