KHOA HOC CONG NGHE
PHAIV B d V A QUAIV HE KHOIVG GIAIV CUA LOAI CAY XOAY [Diaiium cachlnchinemis Pierr) T A I KOIM HA IMIJlXlii,
HUYEI\I KBAIXIG, TilXIH GIA LAI
Nguydn Hdng Hai\ Phgm Tidn Bdng^
T6MTAT
Tim hi^u ca ch^ sinh thai chu yeu da di^u chinh cau tnic khong gian cua loai cay Xoay trong rimg tu nhiSn la rong thirong xanh 6 Kon Ha Nimg la muc tiSu cua nghien ciki nay. Phan tich phan bo va quan he khong gian se d^ xuat duoc cac co che sinh thai chinh dang hoat dong. 6 6 tieu chuan 1 ha (100 m x 100 m) duoc thiet lap tren 3 trang thai rimg chaa khai thac CUL), sau khai thac tac dpng manh (HIL) va trung binh (MIL). Toan bo cac cay than g5 co dirong kinh ngang ngiic > 2,5 cm duoc xac dinh vi tri va cac chi tiSu:
duong kinh ngang nguc va ten loai. Phuon,g phap phan tich mo hinh diem khong gian duo€ ap dung voi ham tuong quan theo cap mot va hai bi^n so. Ket qua phan tich cho thay: (1) Loai Xoay co phan bd chu yeu la dang nglu nhi6n va deu, phan bd kieu cum it xu^t hien. (2) Quan he khong gian ciia loai Xoay voi cac loai khac b hai trang thai rimg HIL va MIL la tuong duong nhau voi 7,5-15,596 tirong hd, 9,3-12,5% canh tranh va 78,2-80% doc lap. 6 trang thai chua khai thac, quan he canh tranh cua loai Xoay voi cac loai khac tang ien ro ret (29,7%) va quan he doc lap giam sau (37,8%). (3) Khai thac rimg da lam suy giam cac quan he tuong tac va lam gia tang quan h§ d6c lap giua loai Xoay vb\ cac ioai cay lan can, Nghien cuu nay da cho bi^t: Co che sinh thai trung lap, canh tranh-tirong hd va phat tan ban che da dieu chinh phan bd va quan he khong gian ciia loai Xoay vdi cac loai lan can nd. Dtra vao cac ket qua nghien cmi nay co till chon ra mat do phii hgp cho loai Xoay va cac loai cay s6ng chung vol nd trong vi6c phat trien loai Xoay a khu vuc nghien cuu.
Tu kh6a: Cay Xoay, ham tuong quan theo cap, phan bd khong gian, quan h& khong gian, rung la rong thudng xanh.
I.DATVANDE
Phan bo va quan he kh6ng gian cua cay rimg, cu the la b cac pham vi khong gian khac nhau, da duac COI la bang chung phan anh dong thai cua lam phan theo thoi gian. Da co rat nhieu co ch^ sinh thai dugc de xuat de giai thich cho md hinh phan bo va quan he khong gian cua cay rimg nhu: Canh tranh va tuong h6, ly thuyet trung Mp, m chet phu thuoc mat do, ly thuyet & sinh thai (Wright, 2002). Ly thuyet trung lap (Neutral theory) cho rang tat ca cac ca the cay khong ph^n biet khac loai deu binh dang trong cac qua trinh sinh san, sinh truong va ch^t (Hubbell, 2005). Dua vao vi tri cua cac cay rieng le, co the xac dinh dac diem phan b6 khong gian cua mpt loai la ki^u cum, nglu nhien hay deu, hoac co th^ xac dinh duoc tuong tac khong gian cua hai loai la canh tranh, doc lap hay tuong h6. Tihnan (2004) nhan manh rang mo hinh khong gian cua cay co the duoc giai thich boi anh huong ciia moi trudng sdng khong dong nhat va cac trang thai can bang cua cac loai phu thupc vao kha nang phat tan, canh tranh hay tuong h6 lin nhau.
' Khoa Lam hoc. Truong Dai hoc Lam nghiep
^ Trung tam Lam nghiep Nhiet ddi, Vien Khoa hgc Lam nghiep Viet Nam
Trong rimg mua nhiet doi, noi co da dang loai cao va mat dp m6i loai thap, thi tuong tac cimg loai va khac loai se di&n ra phiic tap hon cac kieu rimg khac.
Cac phuong phap phan tich m6 hinh di^m khong gian dupe de xuat de tim hieu str sap xep ctia cac diem trong khong gian (Ripley, 1976; Stoyan &
Stoyan, 1994; Diggle, 2003). Vi du dua vao vi tri cua cay (toa dp x, y) va sii dung ham tirong quan theo cap Ripley" K d^ mo ta tinh chat cua mo hinh diem (point pattern) trong mpt dai ciia khoang each (Stoyan & Stoyan, 1994; Ilhan etal., 2008). Trong cac phuong phap nay, mo hinh ly thuyet (null model) duoc sii dung de mo ta gia thuyet ly thuy&t (null hypothesis) ciia mo hinh di^m va sau qua trinh mo phong se dupe doi chifiu voi dir lieu quan sat (Diggle, 2003; Wiegand & Moloney, 2004). Do Iteh giira dii heu thuc nghiem va gia thuyet duoc sii dung de mo ta mo hinh cua dir lieu va du bao cac qua trinh hoac CO ch^ da dieu chinh mo hinh quan sat dupe.
Viec nghien ciiu va Hen he cac co che va qua trinh sinh thai ly thuyet co anh huong dSn phan bo va quan he khong gian cua cay rimg dang la mot van de con it dupe quan tam nghien ciiu b nuoc ta.
Nghien ciiu nay duoe thuc hien tren trang thai rimg la rpng thuong xanh dupe bao ve nghiem ngat sau
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khai thac chgn b khu rimg thuc nghifem Kon Ha Nimg, tinh Gia Lai. Muc tieu cita nghidn ciiu la tim hieu phan bd va quan he khong gian ciia loai cay Xoay voi cac loai cay im the khac tren ba trang thai ning sau khai thac chpn di tim hi^u cac co che va qua trinh sinh thai da dieu chinh cac moi quan he ciing loai va khac loai cita loai cay Xoay b day.
2. DOI TUDNG VA PHUDNG PHAP NGHBU CUU 2 . 1 . D o i t i r p n g n g h i d n c i h i
K h u v u c n g h i e n cihi la rimg t h u c n g h i e m Kon H a N i m g , h u y e n K b a n g , t i n h Gia Lai. R i m g la r o n g thuong xanh am nhiet doi tai khu vuc nghien ctiu co dien tich xap xi 1.400 ha. Truoc nam 1980, viec khai thac chpn dupe thuc hien b day tren nhung qudn the CO trij lupng g& ldn hon 130 m^/ha; ducmg kinh cay toi thi^u duoc khai thac la 45 cm; khai thac chpn cuong do cao (khai thac 30-50% trir lupng), cuong dp trung binh (khai thac 20- 30% trir luong). Sau nkm 1980, toan bp dien tich nay dupe Tram thuc nghiem Kon Ha Nimg bao ve nghiSm ngat phuc vu muc dich bao ton va nghien a i u khoa hpc.
Khu vuc nghien ctiu co nhiet dp trung binh 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% tdng lupng mua hang nam, miia kho keo dai tir thang 1 den thang 4. Dat chu ydu la dat nau tim dien hinh, dat do vang, dat dd vang co tang set loang 16 va d^t do vang tren da set va da bien chat. Dp cao so vdi mirc nude bien xap xi 700 m va dd doc < 5°.
Nam 2018, 6 6 tieu chuan (OTC) 1 ha (100 m x 100 m) dupe thiet lap tren ha trang thai rimg; 02 OTC tren trang thai tac dpng manh sau khai thac (HIL), 02 OTC tren trang thai tac dpng trung binh sau khai thac (MIL) va 02 OTC tren trang chua khai thac (UL). M6i 6 tieu chuan dupe chia thanh mdt ludi 100 d thii cap (10 xlO m). Tren mdi d thii cap, dudng kinh than cay ngang nguc (DBH) tai vi tri 1,3 m, chieu cao viit ngpn (H), vi hi ciia cay (x, y) vk ten loai cay dupe xac dinh va do dem cho tat ca cac cay than gd cd DBH > 2,5 cm. Vi tri cua cac cay rieng le dupe xac dinh thdng qua viec sii dung thudc do khoang each bang laser (Leica Disto D5) va la ban.
2.2. Phuong ph^p nghidn cuu
Cac chi sd da dang Fisher va Margalef diroc su dung de so sanh tinh da dang giira cac trang thai rimg. Cac chi sd nay dupe tinh thdng qua phan mem thdng ke Past (Paleontological statistics) ver. 3, vdi cdng thiic sau:
Fisher's alpha (a):S=a*ln(l+N/a)
Margalef s index = ( S - 1) / ki(N)
Trong dd: S la sd loai; N la tong sd ca the; a la chi sd Fisher's alpha.
Ham tuong quan theo cdp
Ham K(r) md ta su sap xep khdng gian cua ckc diem trong mpt dai ctia khoang each (Stoyan &
Stoyan, 1994). Dua vao khoang each giCta cac c^lp diem, ham K(r) md ta phan bo tan xuat cpng don ctia tat ca cac cap di^m theo khoang each.
K(r) = >» ^ ^ ^iiini.n / " ' Trong do: r la ban kinh vdng trdn cd tam la mpt diem trong md hinh; n la tong sd diem; A la dien tich d mau; w„ la trpng sd hieu chinh anh hudng canh bien; I^ la bien ddm cd gia tri =1 ndu khoang each Uj, giira hai diem i va j < r, ngupc lai I^ =0. Ham B hinction la mdt dang chuyen ddi ciia ham Ripley's K CBesag, 1977):^
L(r) = r J n
Trong didu kien cac diem hoan toan nghi nhi6n khdng gian L(r)= 0 tai tat ca cac khoang each r, L(r)>
0 eho biet cac diem cd phan bo dang cum, L(r)< 0 cho biet cac didm cd phan bd dang ddu. Miic y nghia ciia md hinh thuc nghiem dupe so sanh vdi md hinh ly thuyet trong didu kien hoan toan ngau nhiSn khdng gian.
Vdi mdt loai diem (vi du, ciing mdt loai cay hay mdt nhdm cay), ta cd ham tuong quan theo cap mpt hidn sd - Lii(r), Lii(r) - 0 cho bidt phan hd hoan toan ngau nhidn, Ln(r) > 0 cho biet phan bd kidu cum, Lj|(r) < 0 cho biet phan bd kieu deu tai khoang cich r. Ham tuong quan hai bien sd Li2(r) dupe sir dung de phan tich quan he khdng gian giira hai nhom diem khac nhau (vi du, hai loai cay khac nhau).
Li2(r) = 0 cho biet quan he la dpc lap (khdng tirang tae), Liafr) > 0 cho biet quan he la tuong hd va Li2(r)
< 0 cho biet quan he la canh tranh tai khoang each r.
Cac phan tich md hinh khdng gian bao gdm:
Phan bd khdng gian ctia loai cay Xoay: md hinh ly thuyet hoan toan ngiu nhien khdng gian
(Complete Spatial Randomness - CSR) dupe str dting de kiem tra phan bd khdng gian ciia loai cay. Gia thiet la khdng cd tuong tac giira cac cay trong mo hinh, cac ca thd cay phan bd hoan toan nghx nhien khdng gian. Su dung md hinh iy thuydt la CSR vdi ham Lii(r) dd tim hidu phan bd khdng gian ciia cac ca the cay ciing loai Xoay.
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Quan he khdng gian khac loai ciia loai cay Xoay:
md hinh ly thuyet dpc lap (hidependence): dtrpc sir dung de kidm tra quan hd khdng gian a i a cac cap loai cay chiem tm thd bang viee cd dinh vi tri ctia loai cay thtt nhit vk dich chuyen ngau nhidn toan bp vi tri ciia loai thii hai xung quanh loai thii nhat. Sii dung md hmh ly thuyet la ddc lap va thue hien phan tich vdi h ^ tirong quan theo cap hai hien sd Li2(r).
Trong tat ca cac phan tich, 199 lan md phdng Monte Carlo dtrpc thtre hien va sti dting nam gia tri ldn nhat va nam gia tri nhd nhat de xay dtmg khoang tin cay xap xi 95% bang phan mem Programita 2014 (http://programita.org/) vdi do phan giai khdng gian la 1 m. Sir khac bidt cd y nghia so vdi gia thuydt
\k md hinh thuc nghiem nam ngoai khoang tin c^y.
3. KFT QUA NGHBU COU 3.1. Dac didm c^u tnic riing
Trang thai rimg sau khai thac cudng dd cao (HIL), gdm cac loai chiem da sd sau:
OTC 1: 8,47 Dung liia -f- 8,4 Cd ke + 5,11 Ngat + 4,34 Nhpc la nhd + 4,27 Khao nhot + 4,06 Khao la nho + 4,06 Tram vd do + 3,5 Chdm chdm dd -i- 3,43 Gidi nhung + 3,36 Trudng sang + 3,29 Tram mdc + 2,94
Xoan dao + 2,38 Cdm tang + 2,17 Xoay + 2,1 Khao la dai.
OTC 2: 8,7 Chan chim + 5,95 Ngat + 4.5 Xoay + 4,42 Cd ke + 4,35 Nhpc la ldn + 3,99 Gidi xanh -h 3,92 Dung lua + 3,7 Trudng sang + 3,41 Khao la nhd + 3,26 Tram ti-ang + 2,68 Nho ndi + 2,61 Xoan dao + 2,54 De do + 2,47 Khao nhdt + 2,47 Tram vd do + 2,32 Nhan rtmg.
Trang thai rimg sau khai thac cudng dd trung binh (MIL), gdm eac loai chiem da sd sau:
OTC 3: 7,63 Dung lua + 5,55 Tram vd dd -H 4,99 Cdc da -I- 3,7 Khao la nhd + 3,14 Nhpc la nhd + 3,08 Tram ti-ang + 3,03 Dung tiling -i- 2,97 Xoay + 2,92 Ngat -H 2,92 Nhp ndi + 2,69 Chdm chdm dd + 2,69 Sdn mii + 2,52 Du mode + 2,52 Gdi te + 2,41 Rang rang mit + 2,02 Gidi nhung -i- 2,02 Trudng sang + 1,96 Chdi mdi •+
1,96 Cd ke + 1,96 Khao nhdt -t-1,96 Re bau + 1,85 Chia vdi + 1,68 Khao vang.
OTC 4: 8,7 Tram vo dd + 5,87 Sen mu + 5,16 Khao la nhd + 5,16 Ngat + 4,51 Chia vdi + 4,51 Khao vang + 4,26 Hoke quang + 4,0 Nhpc la nhd + 3,8 Cdc da + 3,42 Xoay + 3,22 Du mode + 3,22 Dung lua + 3,22 Trudng sang •+ 2,84 Tram trang + 2,77 Chdi mdi + 2,45 Gidi nhung + 2,06 Sen dat.
Trang thai rimg
HIL
MIL
UL O T C l OTC 2 OTC 3 OTC 4 OTC 5 OTC 6
Bang L D&c di^m 3 trang t h ^ rung nj Toa do
14-10,475' B;
108-38,977'D 14"09,791' B;
108"39,329' D 14-10,507' B;
108'40,222 B 14"11,492' B;
108*39,938'D 14* 10,839' B;
108*39,236' D 14'10,563'B;
108'40,249' D n/N 32/1429 62/1379 53/1783 53/1551 33/1341 60/2002
So loai 97 86 104 83 111 91
So loai chiem da so
15 17 23 17 13 24
'hj6nciiu Margalef
13,21 13,76 11,16 15,28 11.76 11,84
Fisher a 23,53 24,09 18,75 28,72 20,32 19,64
Tiet dien ngang (mVha)
33,5 36,58 42,77 43,97 48,25 53,25 Ghi chu: nia sdca the cay Xoay, NU tdngsdca the
Trang thai rung chua khai thac (UL), gom cac loai chiem da so sau:
OTC 5: 7,23 Khao nuoc + 6,04 Dung lua + 5,82 Ngat + 5,74 Co ke + 4,77 Tram vo do + 3,43 Nhoc la dai + 3,36 Chom chom do + 2,46 Chan chira + 2,39 Hoac quang + 2,39 Tram choi moi + 2,31 De do.
OTC 6: 7,34 TrSm vo do + 6,89 Sen mil + 6,79 Hoac quang + 5,59 Chia voi + 5,19 Ngat + 3,8 Tram
cay
trang + 3,6 Nhan rimg + 3,0 Xoay + 2,85 Coc da + 2,8 Du mooc + 2,7 Khao la nho + 2,4 Khao vang + 2,35 Khao la to + 2,35 Truong sang + 2,3 Nhoc la dai + 2,2 Nhp n6i + 2,15 Gioi nhung + 2,15 Khao nhot + 2,15 Tram qua to + 2,15 Xuong ca + 1,9 Dung lua + 1,85 Choi moi + 1,8 Re huong.
Tong so loai uu the duoc nghien cuu o Irang thai HIL la 32 loai, trang thai MIL la 40 loai va trang thai
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UL la 37 loai (Bang 1). Tdng tidt dien ngang cho thay su tuong ddng giiia cac d tieu chuan ciia 03 trang thai rimg HIL (33,&-36,58 mVha), MIL (42,77-43,97 mVha) va UL (48,25-53,25 mVha). Tinh da dang loai diroe danh gia thdng qua 2 chi sd Margalef va Fisher a cung cho thay su tirong ddng ciia cac d tidu chuan trong mdi trang thai.
3.2. Quan h^ etmg loii c^y
nhd. Tram vd do, Chdm chdm dd. Gidi nhung. Tram mdc, Xoan dao, Cdm tiing, Khao la dai. Tram ti^g, Nhp noi.
Nhu vay, d tiang thai rung HIL, 32 loai ed quan he khdng gian vdi loai Xoay, bao gdm 12.5% quan h§
tirang hd, 9,3% quan he canh ti-anh va 78,2% quan he ddc lap.
Hmh 1. Phan bd khdng gian ciia loM cay Xoay d 6 OTC dupe bi^u diSn bdi hkm Lii(r) vdi md hinh Ij^
thuydt Id CSR
Duong mau den la phan bd thuc nghiim va dudng mau xdm la khoang tin cay 95%.
Phan tich phan bd khdng gian ciia cay Xoay tren 4 OTC b ba trang thai rimg cho thay loai nay cd phan hd ngau nhien OHinh la, b, e) va phan bd deu d khoang each 32-35 m (Hinh Id). Phan bd cum cita loai nay dtrpc tim thay, trong khoang each cay-cay tii 5-30 m va tii 6-9 m, d trang thai rimg chtra bi khai thac (Hinh le, 0. Nhu vay, trong 06 OTC nghien ciiu, loai Xoay cd phan bd chti yeu la dang nglu nhidn va cum, phan bd ddu chi xuat hien b khoang each ldn hon 30 m.
3.3. Quan hd khdc loai cky
O trang thai rimg sau khai thac vdi cudng dp cao (HIL), 4 loai (12,5%) cd quan he tuong hd vdi loai Xoay d khoang each 10-15 m, 27-32 m va dudi 15 m.
hao gdm Nhpc la nhd, De dd, Nhan rimg va Tnrdng sang (Hinh 2b, c, d). Ngoai ra, 3 loai (9,3%) c6 quan he canh tranh vdi loai Xoay b eac khoang each 28-37 m, 28-35m va 4-14 m bao gdm Nhpc la ldn, Trudng sang va Chan chim (Hinh 2a, e, 0- Rieng loai Trudng sang ed quan he tuong hd d khoang each nhd (<10 m) nhtmg lai cd quan he canh tranh d khoang each ldn tii 28-35 m (Hinh 2e). Cac loai cay khac ddu cd quan he dpc lap vdi loai Xoay, bao gom 14 loai (78,2%): Dung lua, Cd ke, Ngat. Khao nhdt, Khao la
^P^
Hinh 2. Quan h$ khdng gian cila c4c loii cSy rimg chi^m uu th^ vdi l o ^ Xoay a tr^mg thii rtmg HIL duac bi^u di§n boi ham I^Cr) v6i m6 hinh I^ thuyA
lidOcUp
Dudng mau den la quan hd thuc nghiem va dudng mau xam la khoang tin cay 95%.
Hinh 3. Quan h^ kheng gian a i a cac loSi cay rimg chi6n uu th^ v4i loii Xoay tiang fliii rimg MIL dugc bi&i difel
bdi ham LizW v « ma hinh h? thuyft la dOc Up Dudng man den la quan he thuc nghiem va dudng man xim la khoang tm cay fi.91
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O ti-ang thai rung sau khai thae vdi ctrdng dp trung hmh (MIL), ba loai (7,5%) cd quan he tuong hd vdi loai Xoay b eac khoang each khae nhau 5-30 m, 1(^20 m va 0-3 m (Hinh 3e, d, g), hao gom Cd ke, Chdm chdm dd va Chdi mdi. Bdn loai (12,5%), bao gdm Chia vdi (< 20 m). Dung tiTing (25-30 m), Nhpc la nhd (0-8 m) va Sdn mu (10-30 m), ed quan he canh tranh vdi loai Xoay (Hinh 3a, b, e, f, h) d cae khoang each nhd hon 30 m. Cac loai cay khac ddu cd quan he doc lap vdi loai Xoay, bao gdm 32 loai (80%): Dung lua. Tram vd dd, Cdc da, Khao la nhd. Tram tring, Ngat, Nhp noi, Du mode, Gdi te. Rang rang mit, Gidi nhung, Trudng sang, Khao nhdt, Re bau, Khao vang, Hoac quang, Sen dait.
O trang thai rung MIL, loai Xoay cd quan he khdng gian vol 40 loai khac, bao gdm: 7,5% quan he ttrong hd, 12,5% quan he canh tranh va 80% quan he dpc lap.
i,Ch«mdiomdo-Ul b,Cake-Ul C Tiam chDi mw-UL
(37,8%): Khao nude, Ngat, Chan chim, De dd, Sdn mu, Chia vdi. Tram trang, Nhan ning, Cde da, Du mode, Khao la nhd, Gidi nhung, Khao nhdt. Tram qua to, Re hirong.
O trang thai rimg UL, loai Xoay cd quan he khdng gian vdi 37 loai khac bao gdm: 8,1% quan he tuong hd, 29,7% quan he canh ttanh va 37,8% quan he doe lap.
Hinh 4. Quan h^ khdng gian cua ckc l o ^ cSy rung chidm mi thd vdi l o ^ Xoay trang thdi rimg UL dupe bidu diSn bdi h ^ Li2(r) voi md hinh ly thuydt \k
dOc lap
Duong mau den la quan he thuc nghiem va dudng mau xam la khoang tin cay 95%.
6 ti-ang thai rimg chua bi khai thac, 12 loai cay (32,4%) cd quan he tirong tac vdi loai Xoay (Hinh 4, 5). Trong dd, ba loai (8,1%) cd quan he tuong hd bao gdm Cd ke (0-5 m), HoSc quang (7-10 m) va Trudng sang (2-18 m) (Hinh 4b, e va hinh 5i); 11 loai (29,7%) cd quan he canh tranh vdi loai Xoay bao gdm Chdm chdm dd (> 28 m). Tram choi mdi (>36 m). Dung lua (0-10 m), Nhoc la dai (6-8 m), Khao la to (6-25 m), Khao vang (30-38 m), Nho ndi (20-25 m), Xuong ea (3-10 m) va Tram vo dd (>5 m) (Hinh 4a, e-d, f va hmh 5g-h, j-n). Ngoai ra, cac loai cay khac deu ed quan he ddc lap vdi loai Xoay, bao gdm 14 loai
^^^\/^ '>=^-^<^ i^.^::^
, n, Tramvodo-UL
^ V i i ^ = ^
Hinh 5. Quan ht khdng gian cua ckc lo id cdy rung ehidm iru thd vdi loai Xoay trgng thdi rung UL dupe bidu didn bdi hdm LjaCr) vdi md hmh ly thuydt Id
ddc ldp
Dudng mau den la quan hi thuc nghiim va dirdng mau xam la khoang tin cay 95%.
4. KET LUAN
Loai Xoay ed phdn bd chii yeu la dang ngdu nhidn vd ddu, it phdn hd kieu cum. Quan he khdng gian ctia loai Xoay vol cac loai khac d hai trang thai ning HIL va MIL la tuong duong nhau: 7,5-15,5%
tirong hd, 9,3-12,5% canh ti-anh va 78,2-80% dpc lap. O trang thai chua bi khai thac, quan he canh tranh ctia lodi Xoay vdi edc loai khac tang len rd ret (29,7%) va quan he ddc lap giam sdu (37,8%). Khai thdc rimg da lam suy giam cac quan he tuong tac vd ldm gia tang quan he ddc lap giiia loai Xoay vdi cdc loai eay lan can. Kha nang tdi sinh hat cua loai Xoay bi han che, cd the do viec thu luom hat xoay lam thuc pham ctia ngudi dan dia phuong. Ca hai quan he canh ti-anh va tuong hd eimg duoe tim thay vdi ty le tuong duong nhau.
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SPATIAL DISTRIBUTION AND ASSOCIATION OF Diahum cocbmchmesis Pierr IN KON HA NUNG, KBANG DISTRICT, GIA LAI PROVINCE
Nguyen Hong HaiS Pham Tien Bang^
^Faculty of Silviculture, Vietnam National University of Forestry
^Center of Tropical Forestry, Vietnam Academy of Forest Sciences Summary
This study aims to understanding major ecological mechanisms regulating spatial structure of Dialium cochinchinesis tree species in tropical evergreen broadleave forest at Kon Ha Nung. Analyzing of spatial distribution and association may suggest main underlying ecological mechanisms. Six study 1-ha plots (100 m X 100 m) was created in three forest types unlogged forest (UL), high-impact logged (HIL) and medium impact logged (MIL) forests. All woody trees with diameter at breast height (DBH) > 2.5 cm were mapped and recorded dbh and species. Method of spatial point pattern analysis was applied by using univanate and bivariate pair correlation functions. Results showed that (1) D. cochinchinesis was mainly random and regular distributions, aggregated distribution rarely occured. (2) Spatial interspecific associations of D.
cochmchinesis were similar in HIL and MIL with 7.5-15.5% adraction, 9.3-12.5% repulsion and 78.2-80%
independence. In unlogged stands, negative uiterspecific interactions of D. cochinchinesis increased considerably (29.7%) and independent interactions strongly decreased (37.8%). (3) Loggmg leads to decline of significant interactions and increase of independent associations between D. cochinchinesis and its neighbour species. This study shows that ecological mechanisms of neutral, competition/attraction and dispersal limitation regulate spatial distribution and association of D. cochinchinesis and its neighbour species. These outcomes may be useful for regulating an appropnate density of D. cochinchinesis and its coexisting species m D. cochinchinesis development of study region.
Ifeywords: Dialium cochinchinesis, pair correlation function, spatial distribution, spatial association, tropical evergreen broadleave forest
Ngudi phan bi§n: TS. Nguyin Tlianh Tdn Ngdy nhdn bdi: 28/02/2020
Ngdy thdng qua phan bi^n: 30/3/2020 Ngdy duyet ddng: 6/4/2020
