Đánh giá thực trạng và đề xuất giải pháp phát triển cây xanh cảnh quan môi...
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S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.edu.vn/
I HC THI NGUYNTRNG I HC NNG LM
TRN VN NH
NH GI THC TRNG V XUT
GII PHP PHT TRIN CY XANH CNHQUAN MI TRNG KHU VC NI TH,
THNH PH THI NGUYN
LUN VN THC S KHOA HC MI TRNG
Thi Nguyn, nm 2014
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S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.edu.vn/
I HC THI NGUYNTRNG I HC NNG LM
TRN VN NH
NH GI THC TRNG V XUTGII PHP PHT TRIN CY XANH CNHQUAN MI TRNG KHU VC NI TH,
THNH PH THI NGUYN
Chuyn ngnh : Khoa hc mi trng
M s : 6044 03 01
LUN VN THC S KHOA HC MI TRNG
Ngi hng dn khoa hc :PGS.TS. Nguyn Khc Thi Sn
Thi Nguyn, nm 2014
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i
LI CAM OAN
Ti xin cam oan lun vn tt nghip ny l cng trnh nghin cu thc s
ca c nhn, c thc hin trn c s nghin cu l thuyt, kin thc v s
nghin cu kho st tnh hnh thc tin v di s hng dn khoa hc ca
PGS.TS. Nguyn Khc Thi Sn.
Cc s liu, m hnh v nhng kt qu trong lun vn l trung thc, cc
xut a ra xut pht t thc tin v kinh nghim, cha tng c cng b di
bt c hnh thc no trc khi trnh, bo v v cng nhn bi Hi ng nh gi
lun vn tt nghip Thc s..
Mt ln na, ti xin khng nh v s trung thc ca li cam kt trn.
Thi nguyn, ngy thng 11 nm 2014
Hc vin
Trn Vn Nh
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LI CM N
Cy xanh c vai tr quan trng trong i sng con ngi, h thng cyxanh t lu c coi nh l phi, n c tc dng ci thin v bo v mi
trng, mi sinh. Cy xanh bng mt li cng quan trng hn i vi nhng
thnh ph ln, c mt dn s ng v hot ng cng nghip pht trin
mnh. Cy xanh, mt nc c vai tr quan trng trong khng gian th, c
tc dng to b mt cho cnh quan th, ci thin mi trng th.
Hiu r vai tr cy xanh bng mt vi th ni chung v thnh ph ThiNguyn ni ring, cng vi mc cp thit ca qu trnh pht trin cy xanh bng
mt ph hp vi pht trin chung ca thnh ph Thi Nguyn, chng ti tin
hnh thc hin ti: nh gi thc trng v xut gii php pht trin cy
xanh cnh quan mi trng khu vc ni th, thnh ph Thi Nguyn.
Em xin gi li cm n n Ban gim hiu nh trng, phng qun l o
to Saui hc trng i hc Nng Lm Thi Nguyn, cng ton th cc
thy c gio truyn t cho em nhng kin thc trong thi gian hc tp v
rn luyn trong nh trng.
c bit em xin chn thnh cm n n thy gio PGS.TS Nguyn Khc
Thi Sn ging vin ca khoa Ti nguyn & Mi trng - Trng i hc
Nng Lm Thi Nguyn hng dn v ch bo em trong sut qu trnh
thc hin v n nay hon thnh ti kha lun.
Em xin chn thnh cm n.
Thi Nguyn, thng 11 nm 2014Sinh vin
Trn Vn Nh
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iii
MCLC
LI CAM OAN ............................................................................................... i
LI CM N.................................................................................................... ii
MC LC........................................................................................................ iii
DANH MC CC CH VIT TT................................................................ vi
DANH MC CC BNG............................................................................... vii
DANH MC CC HNH................................................................................ iix
M U............................................................................................................ 1
1. Tnh cp thit ca ti............................................................................ 1
2. Mc tiu nghin cu.................................................................................. 2
2.1. Mc tiu tng qut ................................................................................. 2
2.2. Mc tiu c th....................................................................................... 2
3. ngha ca ti...................................................................................... 2
3.1 ngha khoa hc .................................................................................... 23.2 ngha thc tin..................................................................................... 2
Chng 1:TNG QUAN TI LIU NGHIN CU...................................... 4
1.1 C s khoa hc ca ti....................................................................... 4
1.1.1. C s l lun ................................................................................... 4
1.1.2. C s thc tin................................................................................ 5
1.2. Khi qut v cy xanh cnh quan mi trng....................................... 51.2.1. Vai tr ca cy xanh........................................................................ 5
1.2.2. Phn loi h thng cy xanh th................................................. 7
1.2.3. c im mi trng sinh trng ca cy xanh th................... 8
1.2.4. Tiu chun cy xanh th............................................................. 9
1.2.5. Cc nguyn tc b tr cy trng.................................................... 14
1.3. Nhng nghin cu v cy xanh cnh quan mi trng trn th gii v
Vit Nam ..................................................................................................... 14
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1.3.1 Nhng nghin cu trn th gii..................................................... 14
1.3.2.Nhng nghin cu Vit Nam...................................................... 17
Chng 2:I TNG, NI DUNG V PHNG PHP NGHIN CU
......................................................................................................................... 19
2.1. i tng nghin cu v Phm vi nghin cu.................................... 19
2.1.1 i tng nghin cu.................................................................... 19
2.1.2 Phm vi nghin cu........................................................................ 19
2.2 Thi gian v a im nghin cu......................................................... 19
2.2.1 Thi gian nghin cu..................................................................... 19
2.2.2 a im nghin cu...................................................................... 20
2.3. Ni dung nghin cu............................................................................ 20
2.4. Phng php nghin cu...................................................................... 22
2.4.1. Phng php iu tra thu thp s liu th cp.............................. 22
2.4.2. Phng php iu tra thu thp s liu s cp............................... 22
2.4.3. Phng php tng hp, phn tch, x l s liu........................... 23Chng 3:KT QU NGHIN CU ................................................................ 25
3.1. Khi qut tnh hnh c bn vng nghin cu....................................... 25
3.1.1. V tr a l, ranh gii hnh chnh................................................. 25
3.1.2. a hnh, th nhng.................................................................... 25
3.1.3. Kh hu.......................................................................................... 26
3.1.4. Thy vn........................................................................................ 313.1.5 Tnh hnh dn sinh kinh t.............................................................. 32
3.2. Thc trng cy xanh cnh quan mi trng khu vc ni th thnh ph
Thi Nguyn, tnh Thi Nguyn................................................................. 33
3.2.1 Phn loi v xc nh cc loi hnh cy xanh bng mt ni thnh,
thnh ph Thi Nguyn........................................................................... 33
3.2.2 Thnh phn loi, dng sng ca cc loi hnh cy xanh bng mt
ni thnh, thnh ph Thi Nguyn.......................................................... 34
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3.2.3. Sinh trng cy xanh bng mt ni thnh, thnh ph Thi Nguyn
................................................................................................................. 43
3.2.4. Cht lng cc loi hnh cy xanh bng mt ni thnh thnhph
Thi Nguyn ............................................................................................ 49
3.3. nh gi cc ch tiu v mi trng ti cc khu vc cy xanh ni th
thnh ph Thi Nguyn............................................................................... 57
3.3.1. So snh nhit khng kh........................................................... 57
3.3.2. So snh m khng kh.............................................................. 58
3.3.3. So snh tc gi......................................................................... 60
3.4 Nghin cu la chn m hnh cy xanh c hiu qu cho th khu vc
ni th, thnh ph Thi Nguyn.................................................................. 61
3.5. xut gii php pht trin cy xanh cnh quan mi trng khu vc
ni th, thnh ph Thi Nguyn, tnh Thi Nguyn.................................... 63
KT LUN V NGH ..................................................................................... 65
TI LIU THAM KHO ...................................................................................... 67
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vi
DANH MC CC CH VIT TT
CS : Cng s
DHTN : i hc Thi Nguyn
HQG : i hc Quc gia
NN & PTNT :Nng nghip v pht trin nng thn
Nxb :Nh xut bnUBND : y ban nhn dn
TP.TN : Thnh ph Thi Nguyn
Q : Quyt nh
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DANH MCCC BNG
Bng 3.1:Nhit , m, tng s gi nng v lng ma trung bnh
thng tnh Thi Nguyn nm 2012................................................. 27
Bng 3.2: Thnh phn loi cy xanh bng mt ni thnh, thnh ph
Thi Nguyn .................................................................................. 35
Bng 3.3: S h, chi, loi cy xanh bng mt ni thnh thnh ph
Thi Nguyn .................................................................................. 40
Bng 3.4: Cc nhm dng sng ca cy xanh bng mt ni thnh,
thnh ph Thi Nguyn ................................................................. 42
Bng 3.5: Sinh trng cy trng trn cc ngph xy dng trc
nm 1980........................................................................................ 45
Bng 3.6: Sinh trng ca mt s loi cy trng sau nm 1990................... 46
Bng 3.7: Sinh trng cy xanh bng mt trong cng s, trng hc.......... 47
Bng 3.8: Sinh trng cy xanh chc nng khu vc ni thnh, thnhph Thi Nguyn ........................................................................... 48
Bng 3.9: Cht lng cy xanh ng ph TP.TN trc nm 1980 ............ 52
Bng 3.10: Cht lng cy xanh ng ph thnh ph Thi Nguyn
trng sau nm 1990 ....................................................................... 53
Bng 3.11: Cht lng cy xanh bng mt trng hc, cng s .................. 55
Bng 3.12: Cht lng cy xanh chc nng ................................................. 56Bng 3.13: So snh ch tiu nhit cc vng nghin cu c
quan trc vo thng 2/2014 ........................................................... 57
Bng 3.14: So snh ch tiu nhit cc vng nghin cu c
quan trc vo thng 6/2014............................................................ 57
Bng 3.15: So snh ch tiu m khng kh cc vng nghin cu
c quan trc vo thng 2/2014................................................... 58
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Bng 3.16: So snh ch tiu m khng kh cc vng nghin cu
c quan trc vo thng 6/2014................................................... 59
Bng 3.17: So snh tc gi cc vng nghin cuc quan trc
vo thng 2/2014 ............................................................................ 60
Bng 3.18: So snh tc gi cc vng nghin cuc quan trc
vo thng 6/2014 ............................................................................ 60
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DANH MCCC HNH
3.1. Biu nhit trung bnh thng Thi Nguyn nm 2012........ 28
3.2. Biu lng ma trung bnh thng Thi Nguyn nm 2012 .... 29
3.3. Biu m trung bnh thng Thi Nguyn nm 2012 ........... 30
3.4. Biu s gi nng trung bnh thng Thi Nguyn nm 2012... 30
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M U
1. Tnh cp thit ca ti
th t tha s khai lun c mi quan h thun ho gia cc yu t
cnh quan thin nhin v nhn to. Thi k u do qu trnh th nh, dn
c t, cy xanh cng c s dng trong th nhng cha c xem l
mt thnh phn quan trng ca cu trc th. Ngy nay do s pht trin
mnh m ca khoa hc k thut y mnh qu trnh th ho, lm cho
dn s th ngy mt tng, khin cho mi trng b nhim nng n.
Cy xanh c vai tr quan trng trong i sng con ngi, h thng cy
xanh t lu c coi nh l phi, n c tc dng ci thin v bo v mi
trng, mi sinh. Cy xanh bng mt li cng quan trng hn i vi nhng
thnh ph ln, c mt dn s ng v hot ng cng nghip pht trin
mnh. Cy xanh, mt nc c vai tr quan trngtrong khng gian th, c
tc dng to b mt cho cnh quan th, ci thin mi trng th. [29]Cng vi s pht trin kinh t - x hi, cng nghip ho - hin i ho,
qu trnh th ho thnh ph Thi Nguyn cngdin ra nhanh chng, b
mt th c ci thin, i mi tng ngy. Thnh ph Thi Nguyn l
trung tm chnh tr, kinh t, vn ho x hi ca tnh Thi Nguyn, ni tp
trung nhiu trng i hc, cao ng, trung hc chuyn nghip, nhiu nh
my ln nh ang hot ng sn xut kinh doanh vi cc ngnh ngh khcnhau, tc ng ca con ngi n mi trng ngy cng tng v quy m,
cng nh mc nhim mi trng thnh ph ngy mt tng. Do , cng
tc bo v mi trng lm xanh sch p thnh ph l mt yu cu rt cn
thit. Ngy 27/4/2009, y ban nhn dn tnh Thi Nguyn ra ban hnh
Quy nh v trch nhim qun l cy xanh th trn a bn tnh Thi
Nguyn [19]. y l mt nhim v ht sc quan trng i vi tt c cc cpcc ngnh, c bit i vi ngnh ti nguyn mi trng.
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Hiu r vai tr cy xanh bng mt vi th ni chung v thnh ph
Thi Nguyn ni ring, cng vi mc cp thit ca qu trnh pht trin cy
xanh bng mt ph hp vi pht trin chung ca thnh ph Thi Nguyn,
chng ti tin hnh thc hin ti: nh githc trng v xut gii
php pht trin cy xanh cnh quan mi trng khu vc ni th, thnh ph
Thi Nguyn.
2. Mc tiu nghin cu
2.1. Mc tiu tng qut
nh gi thc trng v xut gii php pht trin cy xanh cnh quanmi trng.
nh gi kh nng sinh trng, cht lng ca cc loi hnh cy xanh
bng mt t xc lp nhng c s khoa hc v thc tin xut h thng
cc gii php (khoa hc, cng ngh, c ch, chnh sch pht trin...) v bo v
cy xanh bng mt nithnh, thnh ph Thi Nguyn.
2.2. Mc tiu c th
- Xc nh c cc loi hnh cy xanh th, c im v thnh phn
loi, thnh phn dng sng ca cc loi hnh cy xanh bng mt ni thnh
thnh ph Thi Nguyn.
- Qua quan trc bit c ch s cc ch tiu mi trng ti cc khu vc
nghin cu
3. ngha ca ti
3.1 ngha khoa hc ti ni ln tm quan trng v li ch ca cy xanh mang li cho con
ngi. cc khu vc nghin cu ch ra rng cy xanh gip cho mi trng
trong lnh hn v gim bt nhng iu kin khc nghit t mi trng.
3.2 ngha thc tin
Qua nghin cu nh gi ti lm c s cho cc nh quy hoch th
tham kho v la chn m hnh cho ph hp vi iu kin cnh quan.
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Cn b tr hp l cc loi cy cho tng cng trnh ph hp.
Gip cho mi ngi bit c v vic tn ti v pht trin cc loi cy
xanh trong khu vc thnh ph Thi Nguyn.
ti thng k li hin trng ca cc cy xanh trong khu vc ni thnh
thnh ph Thi Nguyn, t gip thun tin trong vic qun l, bo v cy.
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Chng 1
TNG QUAN TI LIUNGHIN CU
1.1 C s khoa hc ca ti
1.1.1. C s l lun
Theo quy hoch th th cy xanh c trng dc theo va h ng
ph, c 9 n10m (2 l t) c 1 cy xanh[18]. Khi cy ln, khong 4 n 5
tui s cho bng mt, gip khu ph c mt m, m quan, gim ting n v
nhim. Ngy nay, cy xanh c m trng vn m n khi ln,
khong 4 n 5 nm tui mi em trng nn s pht trin ca chng rt nhanh
v cn trnh c cc tc nhn gy h hng khi cy cn nh. Cy xanh ng
ph s gip chng ta tit kim nng lng theo nhng cch chnh sau y:
-Ngn chn s hp th nng lng t nh nng mt tri v to bng rm mt
vo ma h.
- Hp th nng lng mt tri v lm mt khng kh.- Lm gim vic lun chuyn khi khng kh nng vo ma h v chn
gi lnh vo ma ng.
Nhng iu ny rt d hiu nu chng ta tng tng ang sng trong
mt ngi nh mt ph hng Ty, vi cc trng hp va h c trng cy
xanh v khng trng cy xanh. thnh ph Thi Nguyn v nhiu thnh ph
khc, mc d cc n v qun l th u t trng cy trn cc va hnhng ngi dn vn sn sng b ra s tin ln trng thay cy mi ln
hn, to bng mt va h ng, ngay trc ca nh, nhm to m quan v
tit kim nng lng.. R rng, mi ngi dn u thc c nu nh nh
trng cy xanh th b mt ca th khng nhng c ci thin m cc h
gia nh cn gim c vic s dng my iu ha, qut lm mt, s tit kim
c nng lng tiu th trong ma h.[17]
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Vn cy xanh v tit kim nng lng c kim chng qua nhiu
nghin cu trong v ngoi nc. Nghin cu ca t chc USDA Forest
Service, Center of Urban Forest Research l mt v d in hnh. Theo , t
chc ny a ra kt lun rng, khi u t 1$ cho cy xanh s mang li 1,31$.
1.1.2. C s thc tin
Cy xanh ng vai tr quan trng trong i sng x hi nh: iu ha
mi trng khng kh, hp th cc cht thi c hi, khi bi, dit vi khun,
gim ting n, gp phn bo v sc khe con ngi, bo v mi trng.
Ngoi ra, cy xanh vi c im t nhin, cng cc cng trnh kin trc khc
to nn nhng sc thi vn ha c trng, gp phn lm tng v p cnh
quan th, lm phong ph cuc sng vn ho tinh thn ca c dn
th.[16]
1.2. Khi qut v cy xanh cnh quan mi trng
1.2.1. Vai tr ca cy xanh
Khc vi cc h sinh thi t nhin khc, ngoi hai thnh phn c bn l husinh v v sinh, h sinh thi th cn c thnh phn th ba l thnh phn cng
ngh. N bao gm cc nh my, c quan, x nghip, cc c s sn xut... [14]
Thnh phn cng ngh c vai tr quyt nh v chi phi dng nng
lng qua h sinh thi. V cu trc khng gian, h sinh thi th gm c
phn trung tm (ni thnh) v vng ngoi thnh. Phn trung tm l ni tp
trung dn c ln nn rt d dn n nhng thay i v mi trng theo chiuhng xu c nh hng n sc kho ca con ngi. Mc tp trung dn
c cng ng th nguy c thay i v mi trng cng ln.Vng ngoi thnh
c coi nh l vng m chuyn tip t h sinh thi t nhin sang h sinh
thi nhn to. Do tp trung dn c ng v cng nghip pht trin dn n
nhim mi trng ngy cng tng. Ngun gy nhim chnh l: cc phng
tin giao thng, cc nh my, x nghip, cc c s sn xut v rc thi sinh
hot hng ngy. Cc cht gy nhim l: bi, khi, kh c, cc cht thi,
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ting n.... i tng d b nhim nht l khng kh v ngun nc. bo
v mi trng, ngoi cc bin php gim thiu ngun nhim th cy xanh c
vai tr v cng quan trng v h thng cy xanh c nhng chc nng sau[4]:
Trc ht, h thng cy xanh c tc dng ci thin kh hu v chng c
kh nng ngn chn v lc bc x mt tri, ngn chn qu trnh bc hi nc,
gi m t v m khng kh thng qua vic hn ch bc hi nc, kim
sot gi v lu thng gi.
Cy xanh c tc dng bo v mi trng: cy xanh c th gim thiu cc
cht c hi trong khng kh (CO2, SO2, CO) v di t (Ch (Pb), St
(Fe), Km (Zn)) gim nng bi, hn ch ting n, gim nhit, to i
lu khng kh, sinh ngun gi mt, tng lng oxyV d cy Ho hoa vng
rt ph hp trng trn ng ph, mi nm 1 cy Ho c th gi c 2.156
tn bi trn l v bi trn bi c di cy c th lu li 1/6 n 1/3 so vi
bnh thng [12].
Cy xanh c vai tr quan trng trong kin trc v trang tr cnh quan.Nhng tnh cht ca cy xanh nh: hnh dng (tn l, thn cy), mu sc (l,
hoa, thn cy, trng ma ca l...) l nhng yu t trang tr lm tng gi tr
thm m ca cng trnh kin trc cng nh cnh quan chung.[23]
Ngoi chc nng trang tr, tng thm v p thm m cy xanh cn c tc
dng kim sot giao thng v phng h an ton. Vic kim sot giao thng bao
gm c xe c gii v ngi i b. Cc bi thp, b du, ng vin cy xanh trongvn hoa cng vin va c tc dng trang tr va c tc dng nh hng cho
ngi i b. V d, hng cy bn ng c tc dng nh hng nh cc gc cy
c sn vi trng l nhng tn hiu ch dn cho ngi i ng.
S lng cnh nhnh cht ta v n h nhng cy gi ci khng cn tc
dng l ngun cung cp g ci cho dn dng.
Nh vy, ngoi chc nng l sinh vt sn xut nh trong cc h sinh thi
khc (h sinh thi rng, h sinh thi nng nghip...) cy xanh trong h sinh
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thi th cn c chc nng quan trng hn l bo v mi trng v trang
tr cnh quan.
1.2.2. Phn loi h thng cy xanh th
Hin nay trn th gii cng nh trong nc ang c nhng phng php
phn loi xc nh thnh phn h thng cy xanh th nh sau [22]:
- Theo ngun gc: gm c cy trng nhn to v cy t nhin.
- Theo dng sng thc vt:
+ Theo hnh thi l: cy l rng, cy l kim.
+ Theo trng ma: cy rng l, bn rng l, cy thng xanh.
+ Theo hnh dng tn l: cy tn rng, cy tn hp; cy tn dy, cy tn
tha; tn hnh chp, hnh trng, hnh d...
+ Theo kch thc: cy g, cy bi, cy tho v dy leo. Trong nhm cy
g li c th phn chia thnh cy g ln c H>20m, cy g trung bnh c
H=15-20m, cy g nh H=10-15m v cy g nh H=6-10m. Cy bi c chiu
cao H
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+ Cy xanh cng vin v vn hoa: bo v mi trng, iu ho kh hu,
trang tr cnh quan phc v cho nhu cu vui chi, gii tr v ngh ngi ca
nhn dn.
+ Cy xanh chuyn dng: bo v cc cng trnh kin trc vn ho, cc
khu di tch lch s.
+ Cy xanh khu chc nng: l h thng cy xanh trong cc khu cng
nghip, cc c s sn xut, nh my... c chc nng chnh l ngn cn kh
c, bi, iu ho kh hu...
+ Cy xanh trng hc v cng s: ch yu l che bng, iu ho kh
hu, phc v cng tc gio dc v hc tp...
+ Cy xanh vn h v bit th: l h thng cy n qu, cy trang tr.
Nh vy, c nhiu phng php xc nh thnh phn h thng cy xanh
th. Trong phng php xc nh theo qui hoch mi trng th l
thch hp hn c, ang c s dng rng ri. iu tra, nh gi hin trng
v xut cc gii php pht trin h thng cy xanh bng mt ni thnh,thnh ph Thi Nguyn ti cng s dng cch phn chia ny.
1.2.3. c im mi trng sinh trng ca cy xanh th
. C th:
- Cy xanh
. Mi trng sng b nhim do vt
liu xy dng, khi bi do cc phng tin giao thng thi ra. Sau khi trng,
lun lun b tc ng do vic xy dng ci to cc cng trnh c lin quan, do
cc hot ng ca con ngi hng ngy. Khng gian sinh trng b hn ch
do chiu cao ca cc cng trnh xy dng. Nhiu ni thng b ngp nc vo
ma ma do h thng thot nc km.
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- Cy xanh vn hoa cng vin: Mi trng sng b thay i, nhim do
vt liu xy dng, iu kin lp a b bin i do cng tc xy dng. Mi
trng khng kh t b nh hng, nhng y l ni c nhiu ngi qua li
nn s b tc ng ch yu do con ngi.
- Cy xanh cng s trng hc: cng nh cc loi hnh trn, iu kin lp a
cng b bin i, mi trngt b nhim hoc bin dng trong qu trnh thi
cng xy dng cng trnh. Nhng tc ng sau khi trng ch yu do khng gian
sinh trng b hn ch, nn t b tc ng do hot ng ca con ngi.
- Cy xanh khu chc nng: ngoi mi trng t b nhim v bin
dng, cy xanh y cn b nhim bi khi bi ca nh my, x nghip.
Khng gian sinh trng b thu hp. Nhng bc x v nhit khng kh tng
do s phn x ca cc cng trnh nh my c tc ng ng k n i sng
ca cy trng.
- Cy xanh chuyn dng: y l nhm cy t b tc ng nht so vi cc
loi hnh khc. Nhng nh hng ch yu do tc ng ca con ngi trongvic xy dng ci to, hoc do cc cng trnh xy dng lm thu hp khng
gian sng ca cy.
- Cy xanh vn h, bit th:Mc d c chm sc tt nhng cy xanh
vn h, bit th vn b nhiu tc ng lm nh hng n sinh trng ca
cy. Trong khu vc ni thnh hin nay nhng nh hng ny ngy cng gia
tng v cc iu kin sinh trng ca cy cng ngy cng b vi phm do qut b thu hp v tc th ho.
1.2.4. Tiu chun cy xanh th
Cy xanh s dng cng cng trong th gm 3 loi:
- Cy xanh cng vin: L khu cy xanh ln phc v cho mc tiu sinh
hot ngoi tri cho ngi dn th vui chi gii tr, trin khai cc hot ng
vn ha qun chng, tip xc vi thin nhin, nng cao i sng vt cht v
tinh thn...
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- Cy xanh vn hoa: L din tch cy xanh ch yu ngi i b n
do chi v ngh ngi trong mt thi gian ngn. Din tch vn hoa khng
ln, t vi ba ha tr xung. Ni dung ch yu gm hoa, l, c, cy v cc
cng trnh xy dng tng i n gin.
- Cy xanh ng ph: Thng bao gm bulva, di cy xanh ven
ng i b (va h), di cy xanh trang tr, di cy xanh ngn cch gia cc
ng, hng giao thng...
Cht lng cy l ni dung quan trng, m bo cho h thng cy trng
sng st v pht trin. Tuy nhin, cho n nay, nhng nghin cu v lnh vc
ny cn rt hn ch. Hu Th v cng s [27], L ng Tn (2003) [20]
nghin cu v xut tiu chun hnh thi sinh thi cho cc loi hnh cy
xanh th nh sau:
- Tiu chun cy xanh ng ph
+ V kch thc: cy trng thnh c kch thc l cy g ln, trung
bnh hay g nh.+ V yu cu sinh thi: cy a sng, c kh nng sng st v sinh trng
tt trong mi trng khng kh b nhim nng (khi, bi, ting n), t ai
b bin dng, iu kin lp a thp, thot nc km.
+ V trng ma: cy l rng thng xanh, c rng l th ch tng phn.
+ V hnh dng: c dng p,tn l cn i, ta cnh cao; hoa l c mu
sc xinh ti, p.+ Cc tiu chun khc: Hn ch cy c m c. Khng c cnh nhnh
gin d gy, t hay khng c gai. R n su c kh nng ng vng khi gi
bo, khng c r n ngang ph hng mt ng vcc cng trnh ngm. L
khng qu nh, nhng dy mp c nhiu lng t gi cc ht bi cng tt.
Hoa l c kh nng tit cc cht thm cng tt. t hoc khng su bnh.
- Tiu chun cy xanh vn hoa, cng vin
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+ V kch thc: cy trng thnh c kch thc l cy g ln, trung
bnh, g nh v cy bi.
+ V yu cu sinh thi: cy a sng, a bng, c kh sinh trng tt
trong mi trng, t ai b bin dng, iu kin lp a thp, thot nc km.
+ V trng ma: cy l rng thng xanh, rng l, bnrng l.
+ V hnh dng: c dng p, tn l cn i, ta cnh cao, hoa l c mu
sc xinh ti, p. Trong vn hoa cng vin, cy xanh c b tr theo
nhiu cch, v vy tiu chun cho cc i tng ny cng phi khc nhau:
Cy ng c lp: c hnh khi dng dp, mu sc hi ho c o,
kch thc va phi, khng c qu ln, tn l thch hp cho vic pht trin
t nhin hay ct xn to hnh.
Cy trng theo m hay rng nh: c th cy g, cy bi; cy l kim
hay cy l rng thng xanh, rng l,bn rng l.
Cy trng theo hng: c kch thc ln, to nn tn l vm xung
(nh Phng v), cy cao, thng.+ Cc tiu chun khc: Hn ch cy c m c. Khng c cnh nhnh
gin d gy, t hay khng c gai. R n su c kh nng ng vng khi gi
bo. L dy mp c nhiu lng t gi cc ht bi cng tt. Cy c kh
nng tit cc cht thm, cc cht phitoxit dit khun cng tt.
- Tiu chun cy xanh trng hc, cng s
+ V kch thc: cy trng thnh c kch thc l cy g ln, trungbnh, g nh v cy bi.
+ V yu cu sinh thi: cy a sng, a bng, c kh sinh trng tt
trong mi trng, t ai b bin dng, iu kin lp a cao hay thp, thot
nc tt hay km.
+ V trng ma: cy l rng thng xanh, nu rng l th ch tng phn.
+ V hnh dng: c dng p, tn l cn i, ta cnh cao; hoa l c musc xinh ti, p; c hnh khi dng dp, mu sc hi ho c o, kch
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thc va phi, khng c qu ln, tn l thch hp cho vic pht trin t
nhin hay ct xn to hnh;c kch thc ln, to nn tn l vm xung
(nh phng v), cy cao, thng.
+ Cc tiu chun khc: cy khng c m c, khng c cnh nhnh gin
d gy, khng c gai. R pht trin c kh nng ng vng khi gi bo, c
kh nng tit cc cht thm, cccht phitoxit dit khun cng tt.
- Tiu chun cy xanh chc nng
+ V kch thc: cy trng thnh c kch thc l cy g ln, trung
bnh, g nh v cy bi.
+ V yu cu sinh thi: cy a sng, a bng; mc nhanh hay mc chm,
c kh nng thch nghi, sinh trng v pht trin tt trong mi trng c hi,
b nhim nng bi kh c do nh my thi ra, t ai b bin dng, iu
kin lp a cao hay thp, thot nc tt hay km.
+ V trng ma: cy l rng thng xanh, nu rng l th ch tng phn.
+ V hnh dng: c dng p, tn l cn i, ta cnh cao; hoa l c musc xinh ti, p; cy l rng, l kim u thch hp.
+ Cc tiu chun khc: khng c m c, khng c cnh nhnh gin d
gy, khng c gai, r n su c kh nng ng vng khi gi bo; c l dy,
mp, tn l rm rp, nhiu lng t gi li ti a bi, kh thi; hoa qu
khng c mi hi, khng c nha m c; c kh nng tit cc cht thm, cc
cht phitoxit dit khun cng tt.Cy cch ly khu cng nghip, nh my, khu sn xut ngoi cc tiu
chun trn, nhanh chng pht huy tc dng: ngn chn khi, bi v cc ht
cht l lng trong khng kh, cy phi sinh trng nhanh, c l thng xanh,
mp, dy c nhiu lng t cng tt.
- Tiu chun cy xanh chuyn dng
+ V kch thc: cy trng thnh c kch thc l cy g ln, trung
bnh, g nh.
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+ V yu cu sinh thi: cy a sng, a bng; mc nhanh hay mc chm,
c kh nng thch nghi, sinh trng v pht trin tt trong mi trng t ai
v khng kh b nhim, lp a thp, thot nc km.
+ V trng ma: cy l rng thng xanh, nu rng l th ch tng phn.
+ V hnh dng: c dng p, tn l cn i, ta cnh cao; hoa l c mu
sc xinh ti, p; cy l rng, l kim u thch hp.
+ Cc tiu chun khc: khng c m c, khng c cnh nhnh gin d
gy, khng c gai, ng vng khi gi bo; c l dy, mp, tn l rm rp,
nhiu lng t gi li ti a bi, kh thi; hoa qu khng c mi hi, khng
c nha m c; c kh nng tit cc cht thm, cc cht phitoxit dit khun
cng tt.
Cy ven sng, ven h: Cc loi cy trng y rt a dng c th l cy
g ln, g trung bnh, g nh hay cc loi thn tho, thn tre...Cc loi cy
ny c b r pht trin mnh trng xi mn, pht trin nhanh, tn l dy rm
c th gi c cc cht bi. Ngoi ra, ni y cn l ni sinh sng ca ccloi sinh vt lm tng tnh a dng sinh hc.
- Tiu chun cy xanh vn h, bit th
+ V kch thc: cy trng thnh c kch thc l cy g ln, trung
bnh, g nh v cy bi.
+ V yu cu sinh thi: cy a sng, a bng, c kh sinh trng tt
iu kin lp a cao hay thp, thot nc tt hay km.+ V trng ma: cy l rng thng xanh, rng l, bn rng l.
+ V hnh dng: c dng p, tn l cn i, ta cnh cao; hoa l c mu
sc xinh ti, p.
+ Cc tiu chun khc: cy khng c m c, khng c cnh nhnh gin
d gy, t hay khng c gai, c kh nng tit cc cht thm, cc cht phitoxit
dit khun.
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1.2.5. Cc nguyn tc b tr cy trng
Ngoi chc nng iu ho kh hu, bo v mi trng th cy xanh cn
l mt yu t quan trng trong kin trc cnh quan. V vy, trong cc cng
trnh xy dng ngi ta thng s dng cy xanh trang tr cnh quan.
Nhng nguyn tc chnh trong b tr cy trng c mt s tc gi nghin
cu. C th vi cy xanh bng mt ng ph cn tun th theo cc nguyn
tc sau: [15]
- n gin: trn mt ng ph (on ph) nn trng mt loi cy.
- Thay i: Nn kt hp hnh dng mu sc v kt cu to nn s thayi, tng tnh a dng sinh hc,khc phc s n gin, t nht ca vic trng
thun loi. Trn mt ng ph, nht l i vi nhng ng ph di, c th
chia thnh nhiu on, mi on trng mt loi cy.
- Cn bng: Cn bng l s cn thit i vi mt cng trnh kin trc. N
c th hin cch b tr hng cy hai bn ng sao cho hnh dng ca
hng cy bn ny l hnh nh ca hng cy bn kia v ngc li hng cy bn
kia l hnh nh ca hng cy bn ny.
- Lin tc: Cy trng ng ph phi to thnh di lin tc, u, khng
t qung.
- Cn i: Tu theo ng ph rng hp, cc cng trnh kin trc hai bn
ng ph m chn loi cy trng sao cho thch hp vi khng gian.
-Nhn mnh: to nt c o, trnh s n gin, t nht. Tnh cht
ny c th hin vic b tr nhng loi cy tng phn vi cc loi cy
khc trn cng mt ng ph. N c th l mt khm cy, mt hng cy,
thm ch ch mt cy.[28]
1.3. Nhng nghin cu v cy xanh cnh quan mi trng trn th gii
v Vit Nam
1.3.1 Nhng nghin cu trn th gii
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T thi k s khai ca nn vn minh nhn loi, cy xanh lun lun gi
vai tr quan trng v mt trang tr cnh quan. Ngi Trung Hoa, La M, Ai
Cp, Hy Lp s dng cy xanh trang tr nh , lng miu, n th,
tng i...
Qua cc thi k pht trinca x hi loi ngi, th dn dn c
hnh thnh v khng ngng pht trin. Cng vi s pht trin ca th l h
thng cy xanh, v cy xanh l mt b phn quan trng ca cc cng trnh
kin trc, nht l i vi cc cng trnh kin trc th.
Trc y, vic trng cy xanh ch yu l trang tr v kin trc cnhquan. V vy, trng cy g, u v trng nh th no th hu nh ph thuc
vo mun ch quan ca cc nh kin trc, s yu thch thin nhin ca cc
nh qu tc, s ham m ca nhng ngi lm vn... V phng din bo v
mi trng c th ni l cha c ch , nu c th ch mang tnh cc b i
vi mt ngi nh, mt vng hay mt khu vc no .
n gia th k XX, do dn s tng nhanh, s pht trin ca cc ngnhcng nghip, s gia tng ca cc phng tin giao thng... lm cho mi
trng th b nhim ngy cng nghim trng. Cho nn, bo v mi
trng tr thnh nhim v ht sc cp bch.
Cy xanh, mt thnh phn quan trng trong cc cng trnh kin trc, c
vai tr ht sc quan trng trong vic iu ho kh hu, bo v mi trng v
gii quyt cc vn mi sinh. Cng vi vic gim thiu ngun nhim ths dng cy xanh ang l gii php hiu qu nht trong vic bo v mi
trng. V vy, cy xanh th tr thnh ch thu ht nhiu nh khoa
hc quan tm. Tuy nhin, phi n nhng nm u ca thp k 60 vn ny
mi c nghin cu mt cch h thng.
nghin cu cy xanh th, cc nh nghin cu a ra nhiu thut
ng m t nh: phc hp rng, lm nghip vnh ai xanh, k ngh xanh,
lm nghip tin ch, lm nghip th...
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Trong s cc thut ng th lm nghip th l thut ng c nhiu
ngi ch v s dng. Thut ng ny ln u tin c gii thiu ti trng
i hc Torondo (Canaa) vo nm 1965. Tuy nhin, phi sau 5 nm,
Jogensen (1970) mi a ra nh ngha v thut ng ny. Theo ng th lm
nghip th khng ch lin h n cy xanh th hay qun l cc cy c l
m cn qun l cy xanh trn ton b din tch chu nh hng v s dngbi
qun th c dn th. Sau , c cc nh nghin cu khc b sung thm
v thng nht: Lm nghip th l trng v to lp, bo v v qun l cy
xanh v cc thc vt kt hp di dng c th, nhm nh hay di hon cnh
rng trong cc thnh ph,ngoi ca thnh ph v nng thn ngoi thnh.
Theo nh ngha ny th phm vi v chc nng hot ng ca lm nghip
th kh rng lin quan n nhiu lnh vc: lm nghip, nng nghip, bo v
mi trng, kin trc, dch v v thng mi.
Nh vy, vai tr ca cy xanh c s thay i c bn vchc nng
trong h sinh thi th: trc y, cy xanh ch yu l trang tr v kin trccnh quan th nay l iu ho kh hu v bo v mi trng. Cy xanh th
tr thnh mt chuyn ngnh khoa hc thc s-chuyn ngnh lm nghip
th. Vi quan im ny i hi phi xy dng mt lot cc gii php khoa
hc cng ngh t vic qui hoch n vic chn loi cy trng, xy dng h
thng tiu chun cy trng, cc k thut trng trt, chm sc v qun l...
Xu hng pht trin cy xanh cc nc trn th gii rt a dng. Ccquc gia pht trin rt sm khng gian xanh cho cc th, trc ht l cy
xanh ng ph, cy xanh cng vin, cy xanh khu chung c, trong c quan,
trng hc, bnh vin Cc quc gia uquan tm n ch s m2/ngi. Ch
tiu ny cng ln th khng gian xanh ca th cng hon ho.
Boo Chih Min, Kartini Omar-Hor & Ou-Yang Chow Lin (2006) [33]
m t h thng cc vn thc vt Singapore, trong c nu ln vai tr ca
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cc cnh quan, c im ca cc loi cy trong vic thit k cnh quan v k
thut lm vn.
Garrett Eckbo (2002) [34] c bit lu n vic thit k cnh quan ph
hp vi cuc sng ca ngi dn, nht l ngi dn trong cc th. Tc gi
m t cc k thut v a ra phng php xy dng cc vn (cnh quan)
khng ch trn qui m l vn hoa hay cng vin phc v chung cho cng
ng, m cn a ra cc m hnh cho cc h gia nh to nn khng gian
xanh cho cn h hay khu vn ca gia nh.
1.3.2.Nhng nghin cu Vit Nam
Vit Nam, vic trng cy xanh th c tin hnh t hng trm
nm. Nhng vic nghin cu v vn ny th mi c thc hin khong
vi chc nm gn y. iu ng ch l cc nghin cu mi ch tp trung
hai Thnh ph ln l H Ni v Thnh ph H Ch Minh. Quan im v vn
cy xanh th, cc nh nghin cu trong nc u khng nh: h thng
cy xanh th c vai tr ht sc to ln trong vic iu ho kh hu, bo vmi trng v kin trc cnh quan. H thng cy xanh th ca nc ta
cha p ng c yu cu v mi trng cnh quan. T l din tch cy
xanh qu t, c cu cy trng cha hp l. Chng ta vn cn thiu mt gii
php ng b cho vic phttrin h thng cy xanh th[2].
Phn ln cy xanh trn h ph, trong cc cng vin, cc vn ca cc
dinh th H Ni mi trng cui th k 19 u th k 20. Theo i Nam nhtthng ch: H Ni l kinh xa c 36 ph phng, nm (1875) c 21 ph:
H Khu, Vit ng, Hng Mm, Hng M, Bo Thin, Nam Hoa, Hng B,
Hng bc, Hng Thic, Hng Lam, ng Xun, Thanh H...sang u th k
20 ph x m rng ra pha ng v pha nam nh hin nay. Nh vy thm cy
xanh H Ni ch c trng sau khi ph x hnh thnh khong mt trm
nm[5].
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H Gm trc y kh rng, nh dn ra st mp h. Thng 11 nm
1885 gii to cc h dn sng chung quanh h v khi cng t cp h v
cho san lp nhng vng trng thp. n u nm 1893, con ng nha chy
quanh H Gm c khnh thnh. Thm cy xanh quanh H Gm cng
c trng t y vi nhiu loi cy c a t nhiu min ca t nc. V
vy thm cy xanh y hon ton l cy ni a, khc vi thm cy khu vc
Bch Tho. C th ni y l thm cy xanh qu nht ca th H Ni v t
chu tc ng nht bi qu trnh th ha [9].
Cc cng vin v vn hoa khc ca thnh ph nh: Ch Linh, DinHng, Tao n, Pt-xt, Th L...c trng cng thi gian vi cc hng cy
trn h ph theo quy hoch th thi . Nhng cy ci trn cc ng ph
thuc khu vc H Ty, Ba nh c trng sm hn khu vc pha nam H
Gm. Nhng ni chung thm cy xanh H Ni c tui trn 100 nm to
nn mu xanh t thm v p t nhin cho thnh ph.[11]
Nhiu ng ph trng thun mt loi cy c trng nh X c trn
ng Hong Diu v ng B Triu, Phng v trn ng L Thng
Kit, cy Bng lng trn ng Hng Bng, Th Nhum, cy Sao en trn
ng L c, cy Su trn ng Trn Hng o, Phan nh Phng v
in Bin Ph, cy Sa trn ng Nguyn Du... li nhng du n kh
qun khng ch i vi nhng ngi tng sng y m cn c ghi
nhn ca nhiu ngi trn nhng trang th, cu ht v H Ni.[30]
Cy xanh khng th thiu vng trong cn bng sinh thi v mi trng.Cy xanh th li cng c vai tr to ln hn. N hp th mt lng ln
kh cacbonnic do con ngi v cc nh my thi ra, b xung ngun xy ng
k cho con ngi s dng, lm du i ci oi nng ma h, chn nhng
ngun gi bc lnh lo ma ng, gim bt ting n ca hng vn xe c ng
c qua li hng ngy. Sau ngy lm vic cng thng i do hay ngi di vm
cy, tm hn s tr nn th thi. Cy a, cy , cy Mung, cy Xoi, cyi trng trong cc nh cha mang li ngha tm linh.[13]
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Chng 2
I TNG, NI DUNGV PHNG PHP NGHIN CU
2.1. i tng nghin cuv Phm vi nghin cu
2.1.1 i tng nghin cu
- H thng cy xanh cnh quan mi trng khu vc ni th, thnh ph
Thi Nguyn.
- Ch tiu mi trng: Nhit , m, tc gi.
2.1.2 Phm vi nghin cu
ti ca chng tic nghin cu ti khu vc ni thnh, thnh ph
Thi Nguyn, tnh Thi Nguyn.
- Gii hn v mt khng gian: Ni thnh, thnh ph Thi Nguyn, gm:
cc trc ng chnh nh ng Hong Vn Th, ng i Cn, ng
Hng Vng, ng Nguyn Du, ng Nha Trang, ng Cch mng
Thng Tm, ng Minh Cu, ng Dng T Minh, ng Phan nhPhng, ng Lng Ngc Quyn, ng Vit Bc, ng Bc Nam, ng
Bn Tng, ng Ph Lin, ng Thng Nht, ng Quang Trung. Cc
c quan hnh chnh, trng hc, cng s, mt s cm dn c, nh my x
nghip, vn hoa, cng vin trung tm thnh ph Thi Nguyn.
- Gii hn v mt thi gian: T thng nm 2013 n nm 2014.
- Gii hn v mt ni dung: nh gi hin trng cy xanh bng mt
thuc 4/6 loi hnh cy xanh th ni thnh, thnh ph Thi Nguyn.
2.2 Thi gian v a im nghin cu
2.2.1 Thi gian nghin cu
T thng 11 nm 2013 n thng 9 nm 2014.
Thi im quan trc cc ch tiu mi trng 2 thi im: Thng 2 v
thng 6 nm 2014
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2.2.2 a im nghin cu
Ti cc tuyn ng, cng trnh cng cng, khu dn c, cc c quan, nh
my, trng hc...
C th khi o cc ch tiu mi trng ti mt s khu vc im nh: Khu
vc qung trng thnh ph Thi Nguyn, khu vc ng trn Gang Thp,
Cng trng i hc S Phm Thi Nguyn, T 5 phng Ph X TP Thi
Nguyn, khu vc ng trn Tn Long, Bi rc Mi, khu vc cng cn
cng ty Gang thp Thi Nguyn.
2.3. Ni dung nghin cuNi dung 1. S lc v iu kin t nhin, kinh t -x hi thnh ph
Thi Nguyn, tnh Thi Nguyn
- iu kin t nhin
- iu kin kinh t - x hi
Ni dung 2. nh gi thc trng cy xanh cnh quan mi trng khu
vc ni th thnh ph Thi Nguyn, tnh Thi Nguyn
- Hin trng v chng loi cy xanh cnh quan mi trng khu vc ni
th thnh ph Thi Nguyn, tnh Thi Nguyn
+ C nhng loi no
+ c im thc vt hc c bn ca tng loi
- Hin trng v s lng cy xanh cnh quan mi trng khu vc ni th
thnh ph Thi Nguyn, tnh Thi Nguyn
+ Vi cy thn g: Tng loi c bao nhiu cy
+ Vi cy thn tho: Tng loi c bao nhiu m2
- Hin trng v cht lng cy xanh cnh quan mi trng khu vc ni
th thnh ph Thi Nguyn, tnh Thi Nguyn
+ Vi cy thn g: Bnh qun s cy trn din tch, bnh qun s cy trn
nghn ngi dn.
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+ Vi cy thn tho: Bnh qun s m2cy trn din tch, bnh qun s m2
cy trn nghn ngi dn.
- Thc trng v din bin cy xanh cnh quan mi trng khu vc ni th
thnh ph Thi Nguyn, tnh Thi Nguyn
+ Vi cy thn g: Din bin s lng cy trong 3 nm gn y, t 2011
n 2013
+ Vi cy thn tho: Din bin s lng m2cy trong 3 nm gn y, t
2011 n 2013
Ni dung 3. nh gi nh hng ca cy xanh cnh quan mi trng
n mt s ch tiu v mi trng khu vc ni th thnh ph Thi Nguyn,
tnh Thi Nguyn
- nh hng ca cy xanh cnh quan mi trng n nhit khng kh
khu vc ni th, thnh ph Thi Nguyn, tnh Thi Nguyn
(So snh nhit khng kh gia ni c cy xanh vni khng c cy xanh)
- nh hng ca cy xanh cnh quan mi trng n m khu vc ni
th, thnh ph Thi Nguyn, tnh Thi Nguyn
(So snh mgia ni c cy xanh v ni khng c cy xanh)
- nh hng ca cy xanh cnh quan mi trng n nh sng khu vc
ni th, thnh ph Thi Nguyn, tnh ThiNguyn
(So snh nh sng gia ni c cy xanh v ni khng c cy xanh)
- nh hng ca cy xanh cnh quan mi trng n tc gi khu vc
ni th, thnh ph Thi Nguyn, tnh Thi Nguyn
(So snh tc gi gia ni c cy xanh v ni khng c cy xanh)
Ni dung 4. Nghin cu la chn m hnh cy xanh th c hiu
qu khu vc ni th, thnh ph Thi Nguyn
- La chn m hnh cy xanh c hiu qu a ra xut pht trin h
thng cy xanh th.
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- nh hng pht trin h thng cy xanh khu vc ni th, thnh ph
Thi Nguyn theo hng c hiu qu v mt mi trng, cnh quan
Ni dung 5. xut gii php pht trin cy xanh cnh quan mi
trng khu vc ni th, thnh ph Thi Nguyn, tnh Thi Nguyn
2.4. Phng php nghin cu
2.4.1. Phng phpiu tra thu thp s liu th cp
T kt qu ca cc ti nghin cu nh: Nguyn Cng Tng v
cng s (2002) xc nh h thng cy xanh th thnh ph H Ni c 7
loi hnh: cy trng tp trung, cy xanh ng ph, cy xanh vn hoa cng
vin, cy xanh cng s trng hc, cy xanh chuyn dng, cy xanh khu chc
nng v cy xanh vn nh bit th. Hu Th, L ng Tn (2001) p
dng phng php phn chia ny nghin cu hin trng v xut gii
php pht trin cy xanh th H Ni. L ng Tn (2003) nghin cu
mi trng sinh trng ca cy xanh th .
S liu thu thp t cc c quan chc nng nh: Cng ty Mi trng th Thi Nguyn, Cc thng k
2.4.2. Phng php iu tra thu thp s lius cp
o cc ch tiu mi trng c lin quan n s nh hng ca cy xanh nh:
* Phng php o nhit
Dng my o nhit o, v tr cch mt t 2 mt, o trong bng
rm. Theo di nhit ca khng kh mc n nh v ghi li.o ti cc ni c cy xanh thn g, thn tho vkhng c cy xanh. o
mi loi ti 04 v tr khc nhau.
o 2 ln ti mi v tr o, ti 2 thi im l vo thng 2 v thng 6 nm 2014.
* Phng php o m
o m khng kh, dng m kim sng, m kbay hi, m ktc.
m kdng cc trm kh tng thu vn c cm bin (xenx) l tc ngihay mng mng hu c (ng vt) c kh nng thay i chiu di theo hm
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lng hi nc trong khng kh (khi m tng, chm tc nhim m v di
ra, ko mt n by lm di chuyn kim trn bng chia ).
o 2 ln ti mi v tr o, ti 2 thi im l vo thng 2 v thng 6 nm 2014.
* Phng php o tc gi
Tc gi tnh bng mt/ giy hocbng km/ gi. Tcgi thng
thay i nnminhm othng ko di 100 giy ritnh tctrung bnh
cho khong thi gian . o tc gi ngi ta thng dng my o
cnh quthay cnh go.o bngmy ogi cnh qut.
o 2 ln ti mi v tr o, ti 2 thi im l vo thng 2 v thng 6 nm
2014.
2.4.3.Phng php tng hp, phn tch, xl s liu
- Tn khoa hc ca loi cy c xc nh theo cc ti liu ca Nguyn
Tin Bn (2003-2005) [3], Phm Hong H (1992) [10].
- S dng phn mm Excel trn my tnh tnh cc ch s ng knh
trung bnh (D), chiu cao trung bnh (H) v ng knh tn (DT).- Phn chia dng sng cy xanh theo cy rng Vit Nam (2000) [1].
- Vic nh gi cht lng cy xanh th theo cp cht lng (tt,
trung bnh, xu, rt xu) c tin hnh trn c s thng k s lng cy theo
tng cp cht lng, ri tnh % trong tng s theo cng thc sau:
N = m
i
N
N
1
Trong :
N% l phn trm cy ca mt cp cht lng
N l s cy thc t ca cp cht lng.
2.4.4.Phng php iu tra thu thp qua ngi dn
iu tra thu thp s liu nh gi hin trng c hin theo cc tuyn(ph, ng ph), theo cm dn c (xm, lng, khu ph), theo h thng vn
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hoa, cng vin; theo h thng cng s (c quan, trng hc, khu cng nghip,
nh my...).
Thu thp cc s liu v sinh trng (chiu cao, ng knh) c thc
hin cc phng php trong iu tra lm hc hin nay.
Trong qu trnh iu tra, xc nh tn khoa hc v tn Vit Nam thng
gi. Nhng cy cha xc nh c tn, thu mu tiu bn gim nh ti
phng th nghim. Cc s liu thu thp c ghi ring cho tng loi.
S dng phng php iu tra c s tham gia ca ngi dn PRA thu thp s liu v hin trng, ngun gc cy xanh; v nguyn vng, quan
im pht trin h thng cy xanh qua cc i tng l ngi dn, cn b
qun l, cc chuyn gia, nh khoa hc ang cng tc ti cc c quan, ban
ngnh a phng.
Ngoi cc s liu thu thp c, chng ti tham kho cc s liu
nghin cu c c cng b, hoc cc s liu do cc nh nghin cu iu tra thu thp c phn tch nh gi hin trng cy xanh,nht l cho
cc ni dung lin quan n sinh trng, pht trin, ni sng v kh nng thch
nghi v sng st ca cc loi.
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Chng 3
KT QU NGHIN CU
3.1. Khi qut tnh hnh c bnvng nghin cu
3.1.1. V tr a l, ranh gii hnh chnh
Thnh ph Thi Nguyn l tnh l tnh Thi Nguyn, c ta 21029
n 21037 v bc v t 105043 n 105055 kinh ng, cch Th
H Ni 80km v pha bc. Pha bc, ng bc gip huyn Ph Lng, ng
H; pha ty gip huyn i T; pha nam, ty nam gip th x Sng Cng;
pha ng, ng nam gip huyn Ph Bnh. Thnh ph Thi Nguyn nm trn
quc l s 3 H Ni i Cao Bng[21].
3.1.2. a hnh, th nhng
Thnh ph Thi Nguyn c a hnh ch yu l i bt p c cao
tng i khong 50 60m nhng hin nay do qu trnh xy dng thnh ph,
mt s lng ln i ny b san i ginh t cho xy dng. a hnh thnh
ph Thi Nguyn kh bng phng. Tuy nhin, vng t ny vn mang tnh
cht ca din mo trung du vi kiu bc thm ph sa v bc thang nhn to,
thm ph sa mi v bc thm pha tch (t dc t) vi nhng i g thoi, bt
p xen k nhau chim 50,2% din tch t nhin. Bnh qun din tch t nng
nghip ca thnh ph l 425,55m2/ngi, tp trung ch yu cc x pha ty,
ty nam: Phc Xun, Phc Tru, Tn Cng, Thnh c, Lng Sn. Phn
ln din tch c dc di 80, ph hp vi cy la, cy trng hng nm [21].
Tng din tch t nhin ca thnh ph l 177,15km2, trong t nng
nghip 88,88km2, t lm nghip c rng 30,10km2, t chuyn dng
35,82km2, t 13,12km2, t cha s dng v sng sui 9,15km2. Bnh qun
din tch t nhin trn mt u ngi l 847,78m2. n v c din tch nh
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nht l phng Trng Vng (1,02km2). n v c din tch ln nht l x
Phc Xun 18,53km2.
V th nhng, t ph sa chua c 36,23km2, chim 20,65%. t xm
feralit trn st v bin cht c 31,79km2, chim 27,95%, thch hp vi vic
gieo trng cy hng nm. t dc t 80 n 250c din tch 34,03km2, chim
19,22% din tch t t nhin, ph hp vi cc loi cy nng nghip di ngy,
cy n qu, ph hp vi vic pht trin h sinh thi nng lm nghip vng
i. t c dc trn 250l 21,72km2, chim 2,27% tng din tch t nhin,
ph hp vi vic pht trin rng lm nghip v rng cnh quan du lch [21].
3.1.3. Kh hu
Cc s liu v nhit , m, tng s gi nng v lng ma trung
bnh thng tnh Thi Nguyn nm 2012
Thi Nguyn c kh hu c th ca mt tnh min ni, trung du Bc b.
Mt nm chia lm hai ma r rt l ma ma v ma kh.
Ma ma l nhng thng c nhit cao, lng ma ln, nhit caovo thng 5 n thng 9 v lng ma cng tp trung vo cc thng ny.
(Thng 8 c nhit trung bnh cao nht 28,80C v lng ma cao nht vo
thng 7 l 465,2mm).
Ma ma l nhng thng c nhit thp, tri rt, c lng ma t v
thng c gi ma ng Bc trn v. Trong cc thng 11, 12, 1 , 2 m
khng kh kh, nng hanh c km theo sng mui lm nh hng ln nsn xut nng nghip v sinh hot ca ngi dn.
Thi Nguyn c kh hu c th ca mt tnh min ni, trung du Bc b.
Mt nm chia lm hai ma r rt l ma ma v ma kh.
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Bng 3.1. Nhit , m, tng s gi nngv lng ma trung bnh
thng tnh Thi Nguyn nm 2012
Thng
Ch tiu
Nhit khng kh
trung bnhthng (0C)
Tng s ginng -thng
mkhng khtrung bnhthng
(%)
Tnglng mathng
(mm)
1 14,2 4,8 84,0 48,8
2 15,6 18,2 84,0 18,6
3 20,0 28,6 77,0 33,3
4 25,7 111,0 82,0 45,8
5 28,5 159,3 80,0 281,8
6 29,4 116,2 83,0 148,6
7 28,7 167,2 83,0 465,2
8 28,8 207,0 83,0 402,4
9 27,2 138,6 78,0 85,7
10 26,0 127,0 79,0 50,6
11 22,5 75,2 81,0 29,4
12 18,0 33,9 80,0 28,3
Tng 1458 1638,5
Trung bnh 23,7 98,9 81,2 136,5
(Ngun: Nin gim thng k nm 2012- Cc thng k) [7]
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3.1.3.1. Ch nhit
1
10
100
1 2 3 4 5 6 7 8 9 10 11 12
Nhit
3.1. Biu nhit trung bnh thng Thi Nguyn nm 2012
Qua bng 3.1 biu din kh hu tnh Thi Nguyn nm 2012 ta thy:
Nhit trung bnh nm l 23,70C v c s phn ho r rt theo hai ma l
ma h (ma ma) v ma ng (ma kh) nn s chnh lch nhit gia hai
ma l tng i ln. Ma ng lnh thi tit kh hanh, nhit ngy xung
thp ti 5-100C, ma h thi tit nng m, nhit ngy cao nht l 35-380C.
3.1.3.2. Ch ma, m
Thnh ph Thi Nguyn nm trong vng c lng ma ln, lng ma
trung bnh hng nm 1638,5mm, phn b theo ma, v c s chnh lch ln
gia hai ma. Ma ma trng vi ma nng, thng tp trung vo thng 5
n thng8, lng ma chim ti 80% lng ma c nm. S ngy ma trn
100mm trong mt nm kh ln. Ngy ma ln nht trong vng hn na th
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k qua l ngy 25/6/1959, ti 353mm, lm cho thng ny c lng ma k
lc 1.103mm [21]. Lng ma cao nht trong nm vo thng 7 vi lng
ma l 465,2mm
1
10
100
1000
1 2 3 4 5 6 7 8 9 10 11 12
Lng ma
3.2. Biu lng ma trung bnh thng Thi Nguyn nm 2012
Ma kh trng vi ma lnh, thi tit lnh v hanh kh. Trong u
ma kh thi tit hanh kh c khi c thng khng c ma, gy nn tnh tr ng
hn hn, v thng c lng ma thp nht l thng 2. Cui ma kh khng
kh lnh v m do c ma phn.
Do lng ma ln ln m khng kh tng i cao v kh n nh,
vi m trung bnh nm l 80%, thng c m cao nht l thng 6, 7, 8
vi 83%, thp nht l thng 3 vi 77% do chu nh hng ca gi ma ng
Bc kh v lnh.
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1
10
100
1 2 3 4 5 6 7 8 9 10 11 12
m
3.3. Biu m trung bnh thng Thi Nguyn nm 2012
3.1.3.3. Ch gi, v s gi nng
1
10
100
1000
1 2 3 4 5 6 7 8 9 10 11 12
S gi nng
3.4. Biu s gi nng trung bnh thng Thi Nguyn nm 2012
Ch gi Thi Nguyn thay i theo ma kh r rt: Ma ng gi ma
ng Bc l ch yu, cn ma h hng gi ch yu li l gi ng Nam.
Tng s gi nng ca Thi Nguyn l 1458 gi, thng cs gi nng cao
nht l thng 8 (207 gi) , cn thng c s gi nng thp nht l thng 1 (4,8 gi).
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3.1.4. Thy vn
Trn a bn thnh ph c hai con sng chy qua: Sng Cu v Sng
Cng. Sng Cu, pha ng bc thnh ph, chy theo hng ty bc ng
nam to nn ranh gii hnh chnh t nhin vi huyn ng H. on chy
qua thnh ph Thi Nguyn thuc vng trung lu di 25km, on ny dng
sng m rng t 70 n 100m. Lu lng nc bnh qun ma ma 620m3/s
(trong nhng ngy l, lu lng nc lnti 3.500m3/s). Ma kh lu lng
nc nh, ch t bnh qun 3,32m3/s. Sng Cng chy dc pha ty thnh
ph Thi Nguyn to thnh ranh gii t nhin vi huyn Ph Yn v th x
Sng Cng. Sng Cng bt ngun t vng ni Ba L thuc huyn nh Ha,
chy qua huyn i T vo thnh ph. on chy qua thnh ph di 15km.
Vo ma ma, lu lng nc ca sng Cng trong l t 1.880m3/s. Ma
kh lu lng nc rt nh, ch 0,32m3/s.
Sng Cu v sng Cng l ngun cung cp nc sinh hot, nc cho snxut cng nghip v nc ti cho ng rung. Hng nm, hai con sng ny
to nn mt lng ph sa tng ph cho t ai thnh ph. Mc d vy, n
cng thng gy ra l lt. S liu quanst t nm 1959 n nm 2000 Trm
thy vn Gia By: 63 trn l ln xy ra, trong c 4 trn l ln in hnh
xy ra vo cc nm 1959,1968,1983,1986. Trn l ngy 2/8/1959 l trn l
lch s vi mc nc nh l l 28,14m (trn mc bo ng s ba 2,14m).
Thnh ph Thi Nguyn c 93 h, ao va v nh tp trung 25 x,
phng, l ni d tr nc cho sn xut nng, cng nghip, to cnh quan,
cn bng sinh thi.
Ngun nc ngm khu vc ng Bm, Tc Duyn c tr lng ln.
Nc ngm y c hm lng cn nh, hm lng st t 5 n 10mg/lt,
PH 5,5 n 6.
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3.1.5 Tnh hnh dn sinh kinh t
Thnh ph Thi Nguyn c s dn 279.710 ngi (2009), trong khu
vc thnh th 200.420ngi, khu vc nng thn 79.290 ngi, mt dn s
1.474 ngi/km2. Dn tc Kinh c s lng ng nht, do nhiu b phn hp
thnh. Cc dn tc Ty, Nng, Dao, Sn Chay, Sn Du...sng xen k vi cc
dn tc khc trong thnh ph. Tuy mi dn tc hi t v thnh ph Thi
Nguyn t nhng vng khc nhau, vo nhng thi im khc nhau, mi dn
tc li c nhng phong tc tp qun ring nhng do c im c tr thnh
nhng n v nh, xen k gia cc dn tc, nn qu trnh ha hp gia cc
dn tc din ra kh sm v d dng, nh mt l t nhin, trong sut qu trnh
u tranh dng nc v gi nc ca nhn dn thnh ph Thi Nguyn [21].
Thnh ph Thi Nguyn c v tr thun li v ht sc quan trng trong
chin lc pht trin kinh t - x hi ca tnh Thi Nguyn. Do v tr tip gip
gia vng rng ni pha bc v ng bng Bc B, li c ng giao thng thy
b dc ngang nn t xa xa Thi Nguyn l ni bun bn sm ut.Thnh ph Thi Nguyn l mt th loi 2, ng vai tr l mt th
trung tm ca vng trung du v min ni Bc B, l trung tm kinh t -chnh
tr-vn ha-y t-gio dc-khoa hc-qun s ca vng ng Bc. Thnh ph
c h thng gio dc ng th ba so vi c nc ch sau H Ni v TP.H
Ch Minh, ng th hai min Bc sau H Ni. Vi 6 trng i hc v rt
nhiu trng cao ng trung hc chuyn nghip, Thi Nguyn tr thnhmt trong nhng trung tm o to ln ca t nc, do cng l ni quy t
c mt s lng ln thnh phn tr thc, k thut vin cc ngnh ngh
khc nhau, cng l mt th mnh pht trin kinh t ca tnh v thnh ph.
Song mt khc cng gy ra p lc ln v sinh hot, v t ca thnh ph.
Cng t vn ng dn s, nn ny sinh ra nhng kh khn m hin nay
vn ang l ni bc xc ca thnh ph nh mt dn c ngy cng cao, dn
n tnh trng lm gim din tch t trng cy, din tch ao h...thm vo
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ngun cht thi, kh thi trong sinh hot, trong sn xut kinh doanh to ra
mt khi lng cc cht gy nhim ln, nh hng nghim trng n mi
trng, t, nc, khng kh ca thnh ph.
Sau gn 15 nm i mi nn kinh t, thnh ph c nhng bin chuyn
ng k, tc tng trng nhanh, nht l nhng nm gn y, mc thu nhp
bnh qun u ngi mt thng l 1.454.000 ng [7]. Cng vi s pht trin
chung ca thnh ph, cc ngnh, cc cp thng xuyn quan tm tu b, sa
cha, m rng xy dng mi nhiu h thng giao thng, trng hc, bnh
vin, iu v cc cng trnh k thut c s h tng...c bit mng li
thng tin, lin lc ngy cng c nhn rng to iu kin tt cho vic tuyn
truyn, gio dc, vn ng, tip thu cc thnh tu khoa hc k thut.
Nh vy thng qua cc c im v iu kin t nhin, chnh tr, kinh t
x hi chng ta c th a ra nhng thun li, kh khn, nhng tim nng i
vi vic tm ra nhng loi cy ph hp, thch ng tt, ci to c mi
trng, p ng cc yu cu v thm m v to bn sc ring cho thnh phThi Nguyn
3.2. Thc trng cy xanh cnh quan mi trng khu vc ni th thnh
ph Thi Nguyn, tnh Thi Nguyn
3.2.1 Phn loi v xc nh cc loi hnh cy xanh bng mt ni thnh,
thnh ph Thi Nguyn
Cho n nay, quan im ca cc nh nghin cu u thng nht chorng, phn chia h thng cy xanh thnh cc loi hnh chc nng ca cnh
quan l hp l, v n khng ch gip cho vic xc nh gianh gii, m cn
gip cho vic nh hng pht trin v qun l mt cch hiu qu. nh
gi hin trng cy xanh khu vc ni thnh thnh ph Thi Nguyn, ti p
dng phng php phn chia ny. Kt qu cho thy h thng cy xanh ni
thnh, thnh ph Thi Nguyn c nhng loi hnh sau y:
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Cy xanh ng ph:Cy xanh ng ph l h thng cy trng dc theo
l ng v gii phn cch ng ni thnh hay ngoi thnh.
Cy xanh vn hoa, cng vin: Chc nng chnh ca vn hoa cng vin
l ni vui chi gii tr ca mitng lp nhn dn; y cng l ni thng din
ra cc hot ng vn ho th thao. Ngoi ra cn c tc dng bo v t, bo
v ngun nc, gim thiu cht nhim l lng, ci thin kh hu v bo v
cnh quan mi trng th.
Cy xanh trng hc, cng s:L cy xanh trng vi mc ch trang tr,
che bng v ci thin mi trng. Tt c cc trng hc u c cy xanh.
Cy xanh chc nng:y l cy trng trong cc khu vc nh my, khu
cng nghip... gm ch yu l cy bng mt, cy cnh vi chc nng chnh l
iu ho kh hu, ngn gi kh, bi, che bng, gim ting n v trang tr.
(Cng ty c phn Gang thp Thi Nguyn, nh my cn thp Gia Sng, nh
my Z127, Z159...)
Cy xanh chuyn dng: L h thng cy xanh cc khu di tch lch s,
ngha trang, n cha, lng miu, ven sng, h... c chc nng duy tr v bo v
cc cng trnh kin trc, che bng, trang tr cnh quan phc v khch tham quan,
du lch. (Cha Ph Lin, n Xng Rng, i tng nim lit s ca tnh...)
Cy xanh vn nh, bit th:L tp on cy trng trong cc vn nh v
bit th c chc nng che bng, phc v cc mc ch ca ngi dn: ly qu, ly
hoa, l... n hay trang tr ni ngoi tht, i khi cn c dng lm thuc...
3.2.2 Thnh phn loi, dng sng ca cc loi hnh cy xanh bng mt ni
thnh, thnh ph Thi Nguyn
3.2.2.1 Thnh phn loi
Bc u ghi nhn 109 loi thuc 81 chi 41 h thuc hai ngnh:
Ngnh Thng (Pinophyta) v ngnh Ngc lan (Magnoliophyta) nh sau
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Bng 3.2:Thnh phn loi cy xanh bng mt ni thnh, thnh ph
Thi Nguyn
STT Tn khoa hc Tn Vit NamDngsng
Phnb
PINOPHYTA (GYMNOSPERMAE)NGNH THNG(NGNH HT TRN)
1 Araucariaceae H Bch tn1 raucaria exelsaR. Br. Bch tn GOL 1,2,3
2 uniperus chinensis L. Tng GON 2,3,4
2 Pinaceae H Thng3 Pinus massonianaLam. Thng ui nga GOL 1,44 P. merkusiiJunghuhn et Vriese Thng nha GOL 1,2,33 Podocarpaceae H Kim giao5 ageia fleuryi (Hickel)de Laub. Kim giao GOL 1,4
4 Taxodiaceae H Bt mc6 Taxodium distichum(L.) L. C. Rich Bt mc GOL 1,2,3
MAGNOLIOPHYTA NGNH HT KN
MAGNOLIOPSIDA LP HAI L MM5 Altingiaceae H T hp7 Liquidambar formosanaHance Sau sau GOL 2,3
6 Anacardiaceae H Xoi, Mum8 llospondias lakonensis(Pierre) Stapf. Du da xoan GOT 1,2,3,4
9 Dracontomelum duperreanum Pierre Su GOL 1,3,410 angifera indicaL. Xoi GOL 1,3
11 . foetidaLour. Mum GOL 1,3,4
7 Annonaceae H Na12 nnona squamosaL. a GOT 1,3
13Cananga odorata (Lamk.) Hook.f. etThoms
gc lan ty GOT 1,2,3,4
8 Apocynaceae H Trc o14 lstonia scholaris(L.) R. Br. Sa GOL 1,2,3,415 Plumeria rubra L. i hoa GON 1,2,316 Thevetia peruviana (Pers.) K. Schum. Thng thin GON 2,3,4
9 Bignoniaceae H Chm t17 Fernandoa brillehi P. Beauv inh GOL 1,3,4
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STT Tn khoa hc Tn Vit NamDngsng
Phnb
18 Oroxylum indicum (L.) Kurz. c nc GON 2,3,410 Bombaceae H Go19 ombax malabaricum DC. Go GOL 1,2,3,420 Ceiba pentandraL. GOL 1,3,4
11 Boraginaceae H Vi voi21 rgusia argentea(L.f.) Heine Phong ba GOT 3,4
12 Caesalpiniaceae H Vang22 auhinia purpurea L Mng b GON 1,2,3
23 . bassacensis Pierre exx Gagnep Mng b hoa vng GON 1,324 Cassia javaniaca L. Mung hoa o GOT 1,2,325 C. siamea(Lamk.) Irwin & Baneby Mung en GOT 1,2,326 Delonix regia(W. J. Hook.) Raf. Phng v GOL 1,2,3,427 rythrophloeumfordiiOliv. in Hook. Lim xanh GOL 3,4
28 Peltophorum dasyrrhachis (Miq.) KurzHong linh GOL 1,2,3,4
29 Peltophorum pterocarpum DC. Lim xt GOL 3,4
30
Senna surattensis (Burm. f.) Irwin &
Barneby Mung hoa vng GOT 1,2,331 Tamarindus indicaL.* Me GOT 1,3
13 Casuarinaceae H Phi lao
32Casuarina equisetifolia J.R. et J.
G.Forst.Phi lao GOT 1,3,4
14 Combretaceae H Bng33 Terminalia catappa L. Bng GOT 1,2,3,4
34 T. myriocarpa Heurck & Muell. Arg Ch xanh GOT 1,3
15 Dipterocarpaceae H Du35 Dipterocarpus retususBlume Ch nu GOL 1,3
36 opea ordorataRoxb. Sao en GOL 1,2,316 Ebenaceae H Th37 Diospyros decandraLour. Th GOL 417 Ericaceae H quyn38 hododendron crenupatum Hutch. quyn GON 1,2,318 Euphorbiaceae H Thu du
39 ischofia javanicaBlume hi GOL 1,2,3,4
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STT Tn khoa hc Tn Vit NamDngsng
Phnb
40 Sapium discolor Champ & Benth Si GON 419 Fabaceae H u41 Dallergia tonkinensisPrain* Sa GOT 1,2,442 rythrina variegata L. Vng GOT 1,2,3,4
43 illetia ichthyochtora Drake Thn mt GOL 4
44 Sophora tonkinensisGagnep* Ho (bc b) GON 2,320 Lauraceae H Re45 Cinnamomum camphoraPresl Long no (d hng) GOT 1,2,3,4
21 Lecythidaceae H Lc vng46 arringtonia acutanguta(L.) Gaertn. Lc vng GOT 1,2,322 Lythraceae H Bng lng47 Lagestromia speciosa L. Bng lng GOT 1,2,3,448 Lagestromia indica L. T vi GON 1,2,323 Magnoliaceae H Mc Lan49 anglietia conifera Dandy M GOL 1,3,450 anglietia fordiana Dandy Vng tm GOL 3,4
51 ichelia balansae (A. DC) Dandy Gii lng GOL 3,452 ichelia alba DC.* gc lan trng GOT 1,2,353 ichelia champaca L.* gc lan vng GOL 1,2,324 Meliaceae H Xoan54 glaia odorataLour. gu GON 1,2,3,4
55 glaia spectabilis (Miq.) Jain et Benn. Gi np GOL 1,2,356 Chukrasia tabularisA. Juss. Lt hoa GOL 1,3,4
57 Khaya senegalensis (Desr) A. Juss X c GOL 1,2,3,458 elia azedarachLinn. Xoan ta GOL 1,2,3,4
59 Swietenia marcophylla King in Hook. Di nga GOL 1,425 Mimosaceae H Trinh n60 casia confusa Merr* Keo l trm GOT 3,4
61 casia mangiumWilld. Keo tai tng GON 4
62 lbizia lebbleckoides (DC.) Benth.*Sng rn (Bn xetrng)
GOL 1,3
63 lbizia procera(Rocb.) Benht.* Mung xanh GOT 1,2,464 Pithecellobium dulce (Roxb.) Benth. Me keo (Gng ty) GON 3,4
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STT Tn khoa hc Tn Vit NamDngsng
Phnb
65 Samanea saman(Jacq.) Merr.* Me ty GOL 3,426 Moraceae H Du tm66 rtocarpus heterophyllus Lamk. Mt GOT 3,4
67 Ficus auriculata Lour. Sung GON 3,4
68 Ficus bejamica L. Si GOL 1,2,3,4
69 Ficus carica L. V GON 3,470 Ficus damit Gagn. a mt GOL 2,471 Ficus drupacea Thunb. a lng GOT 2,4
72 Ficus elastica Roxb. ex Horn. a bp GOL 473 Ficus stricta (Miq.) Miq. Si l nhn GOT 1,2,474 Ficus vasculosa Wall. ex Miq.* a qu xanh GOL 3,475 Ficus racemosa L. Sung GOL 1,2
76 Ficus religiosa L. GOL 1,2,477 Streblus asper (Retz.) Lour. Dui GON 427 Myrtaceae H Sim
78
Cleistocalyx operculatus (Roxb.) Merr.
et Ferry Vi GON 479 ucalyptus camadulensisDehn. Bch n c GOL 1,3,480 ucalyptus exerta F. Muell. Bch n liu GOL 1,3,481 ucalyptus robusta Smith. Bch n GOL 1,3,482 Psidium guajava L. i GON 2,3,483 Syzygium cuminii(L.) Skeels Trm vi GOL 484 Syzygium jambos(L.) Alston Gioi GON 4
28 Oxalidaceae H Chua me t
85 verrhoa carambolaL. Kh GON 429 Rhamnaceae H To86 Ziziphus mauritianaLamk. To GON 4
30 Rosaceae H Hoa hng87 Prunus armeniaca L. M GON 431 Rubiaceae H C ph88 dina cordifolia (Roxb.) Hook. Go GOT 3,4
32 Rutaceae H Cam89 Clausena indica (Dalz.) Oliv. Mc mt GOL 4
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STT Tn khoa hc Tn Vit NamDngsng
Phnb
90 Clausena lansium(Lour.) Skeels Hng b GON 491 Citrus grandis (L.) Osbeck Bi GON 433 Salicaceae H Liu92 Salix babilonicaL. Liu r GOT 1,2,334 Sapindaceae H B hn93 Dimocarpus longan Lour. hn GOT 1,3,4
94 Litchi chinensis Sonn. Vi GOT 495 Sapindus saponariaL. B hn GOT 1,2,3
35 Sapotaceae H Hng xim96 Chrysophyllum cainito L. V sa GON 497 anilkara zapota(L.) P. Royen Hng xim GON 3,436 Sterculiaceae H Trm98 Sterculia foetida L. Trm GOT 4
99 Sterculia pierrei Gagnep inh trng GOL 1,2,3,437 Theaceae H Ch
100
Camelia amplexicaulis (Pierre) Craib.
ex Harrtwwich Hi ng GON 1,2,338 Tiliaceae101 untingia calabura L. GOT 1,2,3,4
39 Ulmaceae H Du102 Celtis sinensis Pers.* Su GOL 440 Verbenaceae H C roi nga103 Gmelina arborea Roxb. Li th GOL 4104 Tectona grandisL. Tch GOL 4
LILIOPSIDA LP MT L MM41 Arecaceae H Cau105 reca catechuL. Cau CAU 1,2,3,4
106 Cocus nuciferaL. Da GOT 1,2,3,4107 Livistona chinensis(Jacq.) R.Br. K Bc b GOT 1,2108 Livistona saribus (Lour.) Merr. C CAU 1,2,3109 oystonea regia(H.B.K.) Cook. Cau bng CAU 1,2,3,4
(Ngun: Cng ty qun l th Thi Nguyn) [6]
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Cc dng sng:
CAU: cy dng cau da GOT: g trung bnh
GOL: g ln GON: g nh
1: Cy trng ng ph 3: Cy trng trng hc cng s
2: Cy trng vn hoa cng vin 4: Cy trng khu chc nng
Bng3.3: S h, chi, loi cy xanh bng mt ni thnhthnh ph Thi
Nguyn [6]
STT Ngnh H Chi Loi
1 Ngnh Thng (Pinophyta) 4 5 6
2 Ngnh Ngc lan(Magnoliophyta) 37 76 103
Lp Ngc lan (Magnoliopsida) 36 72 98
Lp Hnh (Liliopsida) 1 4 5
Tng s 41 81 109
(Ngun: Cng ty qun l th Thi Nguyn)
T kt qu thu c chng ti c mt s nhn xt sau:
Cy xanh bng mt khu vc ni thnh ch yu c di nhp t cc
vng sinh thi khc nhau v trng.
: X c -Khaya senegalensis,Phng v - Delonix regia, Su - Dracontomelum duperreanum , Nhi -
Bischofia javanica, Sa -Alstonia scholaris, Si -Ficus bejamica....
Mt s loi cy c trng lu i tr thnh nhng cy c th trn
cc ng ph, v khu di tch... C th ni y l mt ti sn qu gi gn lin
vi cc ng ph, cc di tch lch s.
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Cc loi hnh cy xanh khc nhau, c s lng loi cy khc nhau. C
th nh sau:
- Cy xanh ng ph:
66 loi chim 60,55% tng s loi. Cy trng ng ph
ch yu l cy g, trong c nhiu loi c trng t lu i v tr thnh im
nhn quan trng cho mt s tuyn ph nh: Phng v (Delonix regia) trn ng
i Cn, ng Nguyn Du;Bng (Terminalia catappa), Su (Dracontomelum
duperreanum) trn ng Phan nh Phng, Thng Nht..; Nhi (Bischofia
javanica), inh trng (Sterculia pierrei) trn ng Lng Ngc Quyn; X c(Khaya senegalensis) trn ng Vit Bc, ng Nha Trang, Cch mng Thng
Tm; Bng lng (Lagestromia speciosa) , ng
Trng Vng; Trng c (Muntingia calabura) trn ng Bn Tng.
- Cy xanh bng mt vn hoa, cng vin:
53 loi (chim 48,62% tng s loi ), c
vin bo tng. Thuc nhm ny c cc loi sau: Si (Ficus bejamica),
(Ficus religiosa), Long no (d hng) (Cinnamomum camphora), Bng lng
(Lagestromia speciosa), Da (Cocus nucifera); Ngc lan ty (Cananga
odorata), Liu r (Salix babilonica), i hoa (Plumeria rubra), Sa
(Alstonia scholaris), Mng b trng (Bauhinia acuminata), Phng v
(Delonix regia), Mung hoa vng (Senna surattensis)...
- , trng hc:
77 loi,
chim 70,64 . Cc loi ph bin l: Bng -
Terminalia catappa, Bng lng -Lagestromia speciosa, Bch tn -Araucaria
exelsa, Su - Dracontomelum duperreanum, Long no (d hng) -
Cinnamomum camphora, Nhi Bischofia javanica, X c - Khaya
senegalensis, inh trng -Sterculia pierrei, Sa -Alstonia scholaris, Si -Ficusbejamica, Phng v -Delonix regia, Mng b Bauhinia purpurea., T vi -
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Lagestromia indica, Ngc lan ty - Cananga odorata, Lim xt -Peltopholum
pterocarpum, Du da xoan -Allospondia lakonensis...
- Cy trng chc nng:
(chim 62,39%) tng s loi. y l cy trng trong cc khu
vc nh my, khu cng nghip... gm ch yu l cy bng mt, cy cnh vi
chc nng chnh l iu ho kh hu, ngn gi kh, bi, che bng, gim ting
n v trang tr. Cy trng chnh gm: X c -Khaya senegalensis. Juss, inh
trng - Sterculia pierrei Gagnep), Long no - Cinnamomum camphora, Su -
Dracontomelum duperreanum, Nhi Bischofia javanica, Mng bBauhinia
purpurea, Bng- Terminalia catappa, Bnglng -Lagestromia speciosa...
3.2.2.2Dng sng
4
dng sng. S lng v t l (%) ca mi dng sng c trnh by trong
bng 3.4:
Bng 3.4: Cc nhm dng sng ca cy xanh bngmt ni thnh, thnhph Thi Nguyn[6]
STTDng sng
S loi %
1 Cy dng cau da CAU 3 2,75
2 Cy g ln GOL 48 44,03
3 Cy g trung bnh GOT 30 27,52
4 Cy g nh GON 28 25,69
Tng s 107 100
(Ngun: Cng ty Qun l th Thi Nguyn)
4 dng sng:
- Nhm cy g bao gm cy g ln, g trung bnh v g nh, trong cy g ln c s lng nhiu nht 48 loi chim 44,03% tng s loi, sau
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l cy g trung bnh v cy g nh ln lt l 30 loi chim 27,52% v 28 loi
chim 25,69% tng s loi. Cc loi thng c trng phi hp vi nhau
ngoi mc ch che bng cn trang tr cnh quan. V vy, tu theo mc
ch ca tng cng trnh m ngi ta c th trng phi hp mt, hai hay nhiu
loi vi nhau. Do qu trnh th ho, cc khu chung c, khu th mi c
m ra, cc tuyn ng c ci to hay m rng... lm cho s lng cy
thn g b bin i mnh m. Nhng loi c s lng c th nhiu l: Phng
v - Delonix regia , Bng- Terminalia catappa, X c - Khaya senegalensis,
inh trng - Sterculia pierrei, Bng lng - Lagestromia speciosa, Nhi
Bischofia javanica, Sa -Alstonia scholaris, Vng -Erythrina variegata, Bch
tn -Araucaria exelsa, Su -Dracontomelum duperreanum, Si -Ficus bejamica
L, Mng bBauhinia purpurea L....
-Nhm cau da c 3 loi, chim 2,75% tng s loi. Nhm cy ny ch
yu l trang tr trong tt c cc loi hnh cy xanh, trong c s dng
nhiu nht l vn hoa cng vin, cc khu chc nng, cng s trng hc.Nhng loi c s lng c th nhiu l: Cau - Areca catechu L.; C -
Roystonea regia; Cau bng -Livistona saribus.
3.2.3. Sinh trng cy xanh bng mt ni thnh, thnh ph Thi Nguyn
Khc vi cc h thng cy trng khc (cy rng trng, cy nng nghip,
cy cng nghip), sinh trng ca cy xanh th ph thuc vo nhiu yu t,
trong mi trng v khng gian sinh trng l quan trng nht. Cy xanh th thng sinh trng trong mi trng b bin i so vi iu kin t
nhin ca chng: khng gian sinh trng lun b nh hng bi h thng cc
cng trnh xy dng nh nh, ng giao thng, ng dy in, h thng
thot nc, n ng, iu kin lp a b bin dng, t b nhim bi cc
vt liu xy dng, cht thi c; kh hu b nhim do kh thi Tuy nhin,
cho n nay cha c cng trnh no nghin cu mt cch y v nhng
nh hng ny n kh nng sinh trng pht trin ca cy trng.
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a s cy trng u l cy c di nhp t cc vng sinh thi khc nhau
nn sc sinh trng b bin i do iu kin sng thay i so vi iu kin
sng ni nguyn sn. Nhng tc ng ch yu ca con ngi thng qua cc
hot ng tu b hay xy dng u c nh hng trc tip n kh nng sinh
trng ca cy trng. Mc nh hng ph thuc vo cng v mc
tc ng V vy, cng mt loi cy nhng do iu kin trng, iu kin lp
a, mc tc ng ca con ngi, khng gian sinh trng nhiu hay t m c
kh nng sinh trng khc nhau. Do khi nh gi kh nng sinh trng ca
cy trng th cn xem xt trong mi tng quan ca nhng tc ng nh
hng ny.
Cho n nay cha c cng trnh no nghin cu mt cch y v kh
nng sinh trng ca cy xanh th ni chung v cy xanh Thi Nguyn ni
ring. Nhng nghin cu thc hin thng ch a ra nhng nhn xt v
chiu hng v kh nng pht trin ca cy theo cc mc tt, xu hay
trung bnh.
Chng ti cho rng, tiu ch nh gi sinh trng ca cy xanh phi
c da theo cc tiu chun nh gi sinh trng ca cy lm nghip hay
nng nghip tu theo chng loi cy trng. V d i vi cy g trng ly
bng mt v iu ho kh hu mi trng th sinh trng chiu cao, ng
knh v tn l l nhng ch tiu quan trng, i vi cy thn tho trang tr
cnh quan l kh nng sng st v mc che ph, i vi cy bi trng lmcnh hay cc tiu cnh trong cng vin, nh vn l kh nng sng st, tc
ra chi ny lc v kh nng to hnh l quan trng hn c.
Mt tiu ch khc quan trngcn uc cp n l tui th ca cc
loi cy. Cy sinh trng nhanh, i sng ngn s t c gi tr hn cy sinh
trng chm v i sng di. Tuy nhin, to thnh mng xanh, ngoi sinh
trng nhanh th tui th ca loi cy l tiu ch quan trng nh gi cht
lng cy xanh
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3.2.3.1 Cy xanh ng ph
Bng 3.5: Sinh trng cy trng trn cc ng ph xy dng trc nm
1980 [6]
TTTn loi cy
(Ph/ ng ph)N
Sinh trng
D (cm) H1,3 (m) DT (m)
1 X c (Cch mng Thng Tm)60
65,5 0,314 15,50,087 6,20,045
2 Phng v (Nha Trang)40
47,5 0,241 7,50,061 7,10,059
3 Bng (Thng nht)45
37,50,121 6,10,045 6,80,057
4 Sa (Nguyn Du)30
41,50,132 8,70,069 5,00,034
5 Su (Phan nh Phng)35
40,90,129 11,50,022 4,70,031
6 Bng lng (Hng Vng)40
35,30,098 6,70,056 3,90,025
Trung bnh 44,70,151 9,330,057 5,610,042
(Ngun: Cng ty qun l th Thi Nguyn)
Trong N: s cy
D: ng knh thn cy
H: Chiu cao cy
DT: ng knh tn
i vi cy trng trc nm 1980 s liu bng 3.5 cho thy: cy t
ng knh t t 35,3cm (Bng Lng trn ng Hng Vng ) n
65,5cm (X c trn ng Cch mng thng Tm), trung bnh 44,7cm; chiu
cao t 6,1m (Bng trn ng Thng Nht) n 15,5m (X c trn ng
Cch mng Thng Tm) trung bnh 9,33m; ng knh tn t 3,9m (Bng
Lng trn ng Hng Vng) n 7,1m (Phng v trn ng Nha Trang)
trung bnh 5,61m.
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Bng 3.6: Sinh trng ca mt s loi cy trng sau nm 1990[6]
TT Tn loi cy(Ph/ ng ph)
Tui
(Thigiantrng)
N
Sinh trng
D (cm) H1,3 (m) DT (m)
1 Phng v (i Cn) 20 40 41,8 0,135 6,50,043 6,70,046
2 Bng (Bc Nam) 20 45 34,80,091 5,60,040 5,90,041
3 Sa (Nguyn Du) 15 50 32,50,083 6,90,048 4,20,030
4 Nhi (Ph Lin) 10 30 25,7 0,069 5,20,038 3,80,028
5 Trng c (Bn Tng) 10 60 20,50,053 3,50,027 2,60,019
6 Du da xoan (Dng T Minh) 20 35 36,00,102 3,60,027 4,70,035
7 inh trng (Lng Ngc Quyn) 15 85 37,50,124 4,20,030 5,50,039
8 Su (Minh Cu) 5 55 11,50,028 3,40,026 3,10,024
9 Bng lng (Hong Vn Th) 15 65 10,50,021 3,50,027 4,00,029
10 X c (Bc Nam) 10 50 32,20,081 4,10,030 3,40,026
Trung bnh 28,30,079 4,650,034 4,390,032
(Ngun: Cng ty qun l th Thi Nguyn)
Trong N: s cy
D: ng knh thn cy
H: Chiu cao cy; DT: ng knh tn
i vi cy trng sau nm 1990, s liu bng 3.6 cho thy: Cy t
ng knh t t 10,5cm (Bng Lng) n 41,8cm (Phng v), trung bnh
28,3cm; chiu cao t 3,4m (Su) n 6,9m (Sa) trung bnh 4,65m; ng
knh tn t 2,6m (Trng c) n 6,7m (Phng v) trung bnh 4,39m.
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3.2.3.2 Cy xanh bng mt vn hoa, cng vin
Thnh ph Thi Nguyn ch c vn hoa Sng Cu v c Cng ty
qun l th Thi Nguyn qun l v iu hnh, cy xanh c trng datrn c s thit k cnh quan c tuyn chn cy trng thch hp. Song do din
tch t t, hn hp nn s lng cy trng khng ln v ch trng vi mc
ch to cnh quan.
Do khng gian sinh trng khng hoc t b tc ng nn cy trng u
c hnh dng p, khng b chn p bi cc cng trnh xy dng
3.2.3.3. Cyxanh bng mt trng hc, cng s
Cy xanh cng s trng hc lun gn lin vi lch s xy dng v pht
trin ca c quan v trng hc. Nhng c quan, trng hc c b dy lch
s, t b ci to sa cha th h thng cy xanh n nh v c nhiu cy c
knh vi kch thc cao ln. Cn nhng ni b ci to sa cha th t nhiu
cy xanh thay i.
Bng 3.7: Sinh trng cy xanh bng mt trong cng s, trng hc[31]
Loi cy N Tui Sinh trngD (cm) H1,3 (m) DT (m)
Phng v 40 25 37,50,121 6,70,056 4,60,035X C 30 30 63,20,309 14,50,084 5,80,038Bng 60 20 34,30,094 8,10,067 4,90,036
Bng lng 80 15 31,20,076 6,50,054 3,70,028Sa 65 20 29,80,073 7,50,061 3,60,028Du da xoan 50 15 38,70,125 4,60,035 4,30,031
Mung vng 30 10 25,50,068 4,10,030 3,70,028Nhi 75 10 29,50,072 3,90,029 3,20,025inh trng 70 20 35,60,098 7,20,059 7,50,061Vng 45 15 27,40,071 4,30,031 4,00,029
Trung bnh 35,270,111 6,740,051 4,530,034(Ngun: Tng Tuyt Mai2010)
Trong N: s cy
D: ng knh thn cy
H: Chiu cao cy; DT: ng knh tn
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S liu bng 3.7 cho thy: Cy t ng knh t t 25,5cm (Mung
vng) n 63,2cm (X c), trung bnh 35,27cm; chiu cao t 3,9m (Nhi) n
14,5m (X c) trung bnh 6,74m; ng knh tn t 3,2m (Nhi) n 7,5m
(inh trng) trung bnh 4,53m.
3.2.3.4 Cy xanh chc nng
y l cy trng trong cc khu vc nh my, khu cng nghip... gm
ch yu l cy bng mt, cy cnh vi chc nng chnh l iu ho kh hu,
ngn gi kh, bi, che bng, gim ting n v trang tr. Cc khu cng nghip
trong khu vc trung tm thnh ph khng nhiu, ch yu l cc nh my x
nghip c xy dng trong thp k 60-70. H thng cy xanh thng c
b tr trn cc ng i ni trong nh my, x nghip.
Bng 3.8: Sinh trng cy xanh chc nng khu vc ni thnh, thnh ph
Thi Nguyn [31]
Tn loi cy N
Sinh trng
D (cm) H1,3 (m) DT (m)
Phng v 35 51,80,286 6,50,043 5,20,038
X c 35 70,20,431 15,30,085 8,60,068
Bng lng 30 40,50,127 5,60,037 4,50,034
Su 30 50,40,281 6,80,048 4,90,036
Sa 30 45,70,236 6,50,043 4,70,035Bng 35 40,20,125 7,60,060 6,10,045
Trung bnh 49,800,248 8,050,053 5,670,042
(Ngun: Tng Tuyt Mai 2010)
Trong N: s cy
D: ng knh thn cy
H: Chiu cao cy; DT: ng knh tn
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Cy t ng knh t t 40,2 cm (Bng) n 70,2cm (X c), trung
bnh 49,80cm; chiu cao t 5,6m (Bng lng) n 15,3m (X c) trung bnh
8,05m; ng knh tn t 4,5m (Bng Lng,) n 8,6m (X c) trung bnh
5,67m. Do t b tc ng nn cht lng cy trng trong loi hnh ny kh tt.
3.2.4 Cht lng cc loi hnh cy xanh bng mt ni thnh thnh ph
Thi Nguyn
Do c tnh cht c trng ring nn vic nh gi cht lng ca mi
loi hnh cy xanh khc nhau l khc nhau. Tuy nhin, do cc loi hnh c
mt chc nng chnh ging nhau l trang tr cnh quan v iu ho kh
hu. Vi chc nng ny th ngoi kh nng sng st, sinh trng pht trin th
hnh thi ngoi mo ca cy trng c th hin trng thi cy, hnh thi tn
l, thn cy l mt ch tiu quan trng. V vy, chng ti chn tiu chun
hnh thi thn cy v tn l ny lm tiu ch nh gi v cht lng cy
xanh cho tt c cc loi hnh.
i vi cc nhm cy bi, cy tho ch yu l cy trang tr, cht lng cachng ph thuc vo s chm sc ca con ngi, hn na do l cy trang tr v
thng xuyn thay i, nn chng ti khng nh gi cht lng ca cy ny.
i vi cy g l nhm cy ch o v u l cy lu nm, c nh trong cc
loi hnh cy xanh, nn vic nh gi cht lng lm c s cho vic tuyn
chn cy trng cho tng loi hnh cy xanh l ht sc cn thit.
3.2.4.1. Cy xanh ng phCht lng cy xanh trn cc tuyn ph cng l iu gy nhiu bn
khon khi hin nay cha c quy nh c th v tiu chun cy khi a ra trng
ti cc cng vin, ng ph. Ngoi ra s ph thuc vo cc cng trnh, cc
d n xy dng, quy hoch v c kinh ph to nn s khng ng b, thng
nht trong cng tc qun l, bo v, thm ch cn lm ng ph tr nn xu
x, nguy him hn.
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Nhng cy xanh sng lu nm trong khu vc thnh ph Thi Nguyn
cho n nay vn cha c ti liu no cng b chnh xc v tui ca cy,
nhng qua ti liu nghin cu v kho st thc t, cc loi cy x c, bng
lng, phng v, d hng, si, a....c trng khu vc trung tm thnh ph
v trong cc cng s t thi Php thuc vo cui th k 19 u th k 20 . Cho
n nay vn cn gi li c vi ni nh: khun vin Bo tng, ng i
Cn, ng Nha Trang...cn li hu ht cc tuyn ph khc, h thng cy
xanh pht trin theo kiu t pht.
Qua kho st chng ti thy cy xanh trn cc tuyn ng ph ca
thnh ph Thi Nguyn c s khc bit rt r rt:
- Tuyn ng c mt dn c cao, chc nng chnh ca ng ph l
giao thng, thng mi. Ngi dn tn dng ti a din tch bn hng v
thu hp ti a din tch , v vy khng c g l kh hiu khi mt cy xanh
y rt thp 0,5m2/ ngi. Va h ph c rt t cy, do dn t trng mt cch
t pht, ln xn v ch yu l cy du da xoan, cy bng... nh tuyn ngHong Vn Th, Dng T Minh, on u ng Cch mng Thng Tm.
- Trn tuyn ng tp trung hu ht cc khi c quan nh nc nh
ng i Cn v Nha Trang, ng ph rng 23m (i Cn), 10,5m (Nha
Trang), c nhiu hng cy c th rt to hai bn va h, c chiu rng t 6-9m,
to nn khng gian i b rt thoi mi. Cy xanh bao gm: cy xanh ng
ph, cy xanh thm phn ln ng, cy xanh trong vn hoa nh, nhng hinnay a s cc cy xanh trn ng ph ny gi ci, r n ngang ph hng
mt ng v cc cng trnh ngm, mt s cy b ta tr lm mt dng v ca
cy, s cy c trng li khng ng chng loi, khng cng ln.
- Nt c trng d nhn thy l cy hoa sa chim u th trn mt s
tuyn ph (ng Lng Ngc Quyn, Phan nh Phng...), hoa c mi
hng nng vo cui ma h nh hng n sc kho ngi dn. Ngoi
ra, cy bng c ngi dn t trng rt nhiu, c tng tn p nhng loi cy
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ny c khuyn co khng nn trng trong th v loi cy ny c b r
chm d khi c gi bo, ng thi hoa, qu, lrng ra ng ph rt mt
v sinh khng m bo an ton v sinh cho ngi v cc cng trnh cng
cng, hn na loi cy ny thng c rt nhiu su bnh c bit l su rm
trng nhiu trn tuyn ng Thng Nht, Ph Lin ...Tnh trng ngi dn
t trng, cht v di chuyn cy xanh ng ph cng xy ra thng xuyn
nhng do cha c quy nh x l v lc lng bo v cy xanh ng ph
nn khng th x l cc trng hp vi phm. V vy trn nhiu tuyn ph c
nhng loi cy tim tng nhng nguy him, c nguy c gy, hoc che
khut tm nhn ca ngi tham gia giao thng.
Tui cy ph thuc vo lch s hnh thnh ng ph. ng ph cng
lu i, tui cy cng nhiu. Theo thi gian, nhng cy cht hay b gy
c trng li nn cng mt ng phtui cy trng khc nhau, c cy hng
trm nm tui, nhng c cy mi c trng c 2 -3 nm gn y. Tuy
nhin, do s lng cy trng li khng nhiu nn nhng cy cng tui vnchim t l cao, t 80-90% trn cng mt tuyn ph.
Trn mt ng ph t thnh loi cy n gin, thng ch 1 loi. Nu
c hai hay nhiu loi khc nhau th cc loi u c trng lun vi chiu di
trn di 500m/loi. Do cy trng li khng cng loi vi cy cht nn lm
thay i t thnh loi cy. Tuy nhin, mc khng nhiu v loi cy ch
o (cy trng chnh) vn chim u th tuyt i (trn 90%).Trn cc ph chnh u c h rng (5-6m), nu cc cng trnh xy dng
nm su bn trong th khng gian sinh trng ca cy xanh gn nh cha b
vi phm (ng Nha Trang, i Cn, Nguyn Du, Hng Vng... ). Nhng
ni c h ph hp (di 3m) v c nh xy st ra h ph u nh hng n
khng gian sinh trng ca cy. Nhng ng mi c xy dng thng c
h rng (3-6m). Nu hai bn ng l c quan hay cng s vi cc c ng trnh
xy dng su vo trong th khng gian sinh trng ca cy trng cha b nh
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hng. Nhng ni c nh st h ph (k c c quan v nh dn) th cy c
chiu cao trn 4m b nh hng: tn cy pht trin st vo ban cng,
tng nh v khng cn khng gian pht trin tip (ng Bn Tng,
ng Phan nh Phng, ng Vit Bc...).
Trn cc tuyn ph iu tra, hu ht nhng cy cao trn 3m b nh
hng bi h thng ct in v ng dy din. Mc nh hng tu thuc
vo tnh cht ca h thng. Nhng cy di ng dy cao th cy trng
thng xuyn b cht cnh h thp chiu cao cy m bo an ton hnh
lang in. Vic xy dng, ci to, c bit m rng ng t r cy, xy
b va h lm thu hp din tch mt t, nh hng n kh nng tn ti v
sng st ca cy. Do quy hoch ng giao thng v xy dng hnh lang
ng ph lm cho mt s hng cy xanh bng mt b y ra st mp
ng nh hng.
Bng 3.9: Cht lng cy xanh ng ph TP.TN trc nm 1980[6]
Tn loi NTt Trung bnh Xu Rt xu
S cy % S cy % S cy % S cy %
X c (Cch mng
Thng Tm)75 56 74,67 14 18,67 3 4,00 2 2,66
Phng v (i Cn) 36 17 47,22 12 33,34 4 11,11 3 8,33
Bng (Thng nht) 87 59 67,82 18 20,69 6 6,89 4 4,60
Sa (Nguyn Du) 35 23 65,71 7 20,00 3 8,57 2 5,71
Su (Phan nh Phng) 32 19 59,37 8 25,00 2 6,25 3 9,38
Trung bnh 62,96 23,54 7,36 6,14
(Ngun: Cng ty qun l th Thi Nguyn)
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i vi cy trng trc nm 1980 s liu bng 3.8 cho thy:
- T l cy c cht lngtt chim t 47,22% (Phng v) n 74,67%
(X c), trung bnh l 62,96%.
- T l cy c cht lng trung bnh t 18,67% (X c) n 33,34