Qudn ly Tdi nguyen rieng & Moi tru&ng
DAC DI£M DONG CHAY BE MAT VA LU^ONG DAT XOI MON TR£N 6
" NGHIEN CUtJ DANG BAN TAI NUI LUOT - XUAN MAI - HA NQl
Biii Xuan Dung', Phiing Van Khoa^
'•^Truorng Dgi hgc Ldm nghiep
T O M T A T
DS xac djnh dong chay b^ mat va Iugng ddt xoi m6n & cac diSu kien che phu khdc nhau, chiing toi da tiSn hanh lap 2 6 nghien ciiu dang ban (2 m^/6) la dit rimg trdng va dat cay byi tai vung mii phia TSy ciia Hi NgL D6ng chay bh m^t va lucmg dat xoi mon dirg-c quan trie lien tyc cho 18 tr^n mua khac nhau keo dai tii ngiy 15 thing 6 toi 23 thang 9 nSm 2016. BSng vi?c sii dung phan m£m R dS phan tich cac so lieu thu dupc, nghien ciiu dua ra mgt so ket qua chinh nhir sau: 1- Khu vuc nghien ciiu c6 lupng mua hang n5m t i 1300 - 2300 mm, du^c chia thanh 2 mua rd ret: mua mua thudng bat diu tir thang 4 din t h ^ g 10, miia kho bat dau tut thing 11 dk thang 3 nam sau; 2- Dong chay b^ mat ciia dat cky byi che phu (hfi s6 dong chay la 5,9%) Ion hem gin 5 lan so vdi dit rimg (he s6 dong chay 1,2%). Nguong lupng mua lam xuat hj?n dong chay be mat 6 dat rung >10 mm/triin va > 8 mm/tran vdi dilu ki|n cay byi che phu; 3- Lupng dit xoi mon cua cay byi che phu (0,6 g/m'/trSn mua) Ion hon 2,5 lan so vdi dit co rtmg che phu (0,25 g/mVtrSn mua); 4- Dong chay bh m$t vi lugng dit xoi m6n trong dilu kien che phii cay bui Ion hon rimg chii yeu la do kha nang giii l?i nuoc tren tdn va lugng nudc thim cua dit rimg idn hon so vdi cay byi. DiSu nay cho thiy viec duy tri Idp che phii rimg la rat quan trong nhim bao v? va diSu tiet nudc cho khu v\rc dit d6c va vung dSu ngudn.
Tir kh6a: Che phu thirc vat, che dq mira, dong chay be mat, vung nui, s6i mdn.
I. D^T V A N D E
Xoi mon la hien tirgng bao mon ldp dat be mat dxrcji tac d6ng cua nirdc ho|c gio (Mohammad and Adam, 2010). Theo cic nghien cuu cua FAO - UNEP (2005) hang nam cd tir 5 - 7 trieu ha dit mit kha nang san xuat do xoi mon dat (Montgomery, 2007) dong thai cung chi ra rang lucrng dat mat di hang nam do xdi mon tren trai dat len tdi 75 ti tin.
Xoi mon thuong xay ra mJinh d Chau A, Chau Phi va Nam My vdi lugng dk xdi mon hang nam tii 30 - 40 tSn/ha/nam (Lal, 1990). 6 Vi?t Nam, lugng dit mdt di do xdi mon la rat khac biet giua cac vimg va giua cac loai hinh sir dung dat. Xdi mdn ciia luu vuc dugc che phu bdi cay ndng nghi?p va rung d VTnh Phiic dao dgng tu 16,3 tdi 172,2 g/mVnam (Mai va cgng sir, 2013), trong khi d Hda Binh, xdi mdn la tie 14 - 150 g/m^/nam (Ha va cgng sir, 2012).
Podwojewski va cgng su (2008) lai tim dugc xoi mdn cd the len tdi 1305 g/m^/nam d Hda Binh, trong khi xdi mdn tut dat trdng san d Son La cd the dat 1700 g/m^/nam (Tuin va cgng su, 2014). Xdi mdn ciing dong thdi lam mit ldp mim va chat dinh duong ciia dat nhu Nita,
Photpho, Kali, gay anh hudng ldn tdi doi s6ng Clia con ngudi nhu lam giam thu nh§p, an ninh lugng thuc va ddi ngheo (Lal, 1998; Teramage va cdng svr, 2013; Anh va cgng s\r, 2014).
Theo FAO (1983 - 2000) thi lugng chat dinh duang mit di hang nam do xdi mdn gay ra tai Chau Phi cd th6 tdi 22 kg Nito/ha; 2,2 kg Photpho/ha va 15 kg Kali/ha. Lugng tien mat di do viec mit chat dinh dudng ciia dat cd the udc tinh tuong duang vdi 4 ti USD.
Thdng thudng xdi mdn xay ra khi cudng do mua ldn hon tdc d0 thim nudc ciia dat lim xuat hien ddng chay mat va cudn theo ldp dat be mat (Miyata va cgng sir, 2009). Khi dong chay bd mat gia tang thudng keo theo su gia tang cua lugng dit xdi mdn nhu xdi mdn khe, xdi mdn ranh va xdi mdn mang (Miyata va cgng sir, 2009). Vi vay sy phat sinh ddng chay m | t dugc xem la nhan to quan trgng quyet djnh miic do xdi mdn. De bao v? dat chdng xdi mon can cd nhCrng bien phap nhSm giam thieu nguy ca xuat hien ddng chay m^t. Thuc vat che phii be mat dit la mgt nhan t6 quan trgng anh hudng tdi su phat smh ddng chay m^t va xoi mdn khi vira tac dgng vao pha ban pha cua h?t 64 TAP c m KHOA HQC VA C 6 N G NGHE LAM NGHIEP SO 4-2017
Qudn ly Tdi nguySn rieng & Moi tru&ng mua (Montgomery, 2007) va pha cudn troi cua
ddng chay (Gomi va cdng su, 2008).
Nhieu nghien cuu da dugc thirc hien nhlm kiSm tra anh hudng cua thyc vat che phii hh mat dSn ddng chay mat vk xdi mdn (Anh va cdng sy, 2014). Vi dii, Miyata va cgng su (2009) da chi ra rang lugng dit xdi mdn ty le nghich vdi phin tram che phii mat dit khi ki^m tra bang cic trgn mua nhan tao. Gomi va cdng sy (2008) phit hi?n dugc lugng dit xdi mdn it han khi tang ty le che phu cua cay byi. Trong dieu ki|n h^ sinh thai rung, cay bui tham tuai lam giam xdi mdn va ddng chay mat tdt hem tang cSy cao (Zhou va cdng sy, 2008), bdi vi kich thudc cua hat mua trd nen ldn hon dudi tin ting cay cao (Nanko va cgng su, 2008).
Mac dil da cd nhieu hieu biet ve mdi quan he giua che phii be mat va xdi mdn, nhi^u vin de khic ve quan h^ nay van cdn chua dugc sang td nhu anh hudng cua che phii tdi tac dgng ban phi ciia hat mua (Sidle, 2004), lam suy giam ddng chiy mat (Dilng va cgng sy, 2011) giira cua tham thyc vlt rimg va cay bui. Nham khac phyc nhung han ch6 tren, chiing tdi da thyc hiSn nghien cuu: "Bdc diem dong chdy mgt vd lu(mg ddt xoi mon tren 6 nghiin eieu dgng bdn tgi Niii Luot - Xudn Mai - Hd Npf\ Ket qua
tim kiSm dugc sS la ca sd khoa hgc quan trgng phuc vy cho viec xay dung giai phap nHam dieu tiet nudc va bio ve tii nguyen dat ciia vimg diu ngudn.
n . NQl DUNG, PHUtfNG PHAP NGHIEN CUtJ 2.1. NQI dung nghien ciru
De dgt dugc nhung myc tieu de ra, chiing tdi ti^n hinh thuc hien 03 ndi dung nghien cim:
(1) DSc di6m che do mua ciia khu vuc nghien cuu; (2) Danh gii die diem phit sinh ddng chay mat dat d cac dieu kien che phu thyc vat khic nhau; (3) Xie dinh lugng dit xdi mdn tai cic dieu ki?n che phii thyc v | t khac nhau.
2.2. Phirong phap nghien CIJU 2.2.1. Bgc diem khu v^ nghien cuu
Niii Ludt cd dia hinh tuang ddi ddng nhit mang tinh gd nui thip, it bi chia cat, gdm 2 qua ddi ndi tiep nhau ch?y dai 2 km theo hudng tir Ddng sang Tay, mdt dinh cd dg cao tuyet doi l i 133 m (hinh 2.1). Dinh cdn lai cd dg cao tuy?t ddi la 76 m, dg ddc trung binh la 150, noi ddc nhit la 270, hudng phoi chu y6u la cac hudng Ddng Bac, Tay Bac v i Ddng Nam. Dit d khu vyc Niii Ludt la dat Feralit nau vang phit triln trSn da me Poocfiarit thudc nhdm d i micma trung tinh, tang diy hoac trung binh tuy thudc vao ttmg vi tri dia hinh.
lOOkm . - " ^ . - • ; . * - ^ ' '
Hmh 2.1. Vj trf khu vyc nghien cun
TAP CHi KHOA HQC VA C 6 N G NGHE LAM NGHlEP S 6 4-2017
Qudn ly Tdi nguyen rimg & Mdi truemg Niii Ludt gdm nhilu loai hinh che phii khic nhau nhu gdm rung hdn giao, dat trang cd cay byi va dit trdng. Vi the nhim dinh gia kha nang bao ve dit chdng xdi mdn ciia cic loai hinh che phu khic nhau, chiing tdi da lap 6 dang bing (dien tich 2 m^ = 1 m x2 m) tren mdi loai hinh: Plot 1- Dit rimg che phu va Plot 2: Dit cd cay bui che phii (hinh 2.2). Riing Bang 1. DSc diem dieu Id^n
trdng Clia d nghien ciru la rung hdn giao gifia re huang va thdng vdi dg tan che la 90%, trong khi do che phii la 30%. 6 dang ban 2 cd d^ che phli 90%. Dg ddc ciia 2 d dgng ban khdng c6 su khic bi|t ldn khi chiing lin lugt li 20,5 va 19,5°. Dg xdp cua dit b cac loai hinh che phii la tuong ddi cao tir 47 - 55%, trong khi tSng dit mdng tir 48 - 52 cm (bing 1).
tir nhi£n ciia cdc 6 dang ban 6 dang Loai hmh -, ^' -.,' " L' L' Loai cay
ban che phu *^
Tan che
(%)
Che phu
(%)
D9 doc Do xop
(%) (%)
B^diiy~
ting dit (CM) Dat rimg
trdng
Re huong
-Thdng 20,5
Dat cay Duong xi, b\ii Co lao 2.2.2. Xdc dinh dong chay mgt vd lupmg dat xdi mon
*B6 tri thi nghiem
- 6 dang ban cd dien tj'ch 2 m^, cgnh dai (2 m) vudng gdc vdi dudng dong muc trong khi b8 rdng (1 m) song song vdi dudng ddng muc.
- Thanh d dang bin dugc lap dgt bing tim nhya cd chieu cao tr£n mat dit la 0,25 m va chieu chdn xudng dat 5 cm nhim cd dinh d v i
ngan ddng chay mat - xdi mdn txi cho khac chiy vio,
- Phan ming hung ddng chay mat vi xoi mdn dugc dgt phia dudi cd kit noi vdi mot bmh dyng de chiia ddng chiy mat va xdi mon.
- Ben canh d dang ban, chiing tdi lip dat mgt dng do mua bang nhua ciia M.^ de do lugng mua tgi khu vuc nghien ciiu.
fflnh 2.2. Sff Ah vi tri va d i k IdSn cac 6 quan trie dong chiy, xdi mdn vJ mir 66 TAP c m KHOA HQC VA CONG NGHE LAM NGHIfP S 6 4-2017
Qudn ly Tdi nguyen rieng & MdJ truomg
*Quan trdc dong chdy vd xoi mon Sau moi tran mua, chung tdi tiln hinh thu toan bp lugng nudc trong thung chiia v i lugng dit xdi mdn tr^n ming (hinh 2.2, 2.3). Sau dd chiing tdi tien hanh lgc nudc d l xac dinh Iugng ddng chay mat sau mdi tran mua. Lugng dit cd dugc dem di siy kho kiet de xie dinh lugng dat xdi mdn. Ddng chay mat va lugng dit xdi mdn dugc quan sit cho 18 tran mua cd lugng mua khic nhau ttong khoing thdi gian tir thing 6 den thing 9 nam 2016. Ngoii viec quan trkc ddng chay mat v i xdi mdn, chiing tdi ddng thdi xie djnh Iugng mua (tram do mua tai mii Ludt, Tnidng Dai hgc Lam nghiep) va lugng nudc Igt qua tan tai khu vuc nghien ciiu bing dng do mua bang nhua cua My (hinh 2.3d).
2.2.3. Xdc dinh dac diem che dp mua
Lugng mua dugc thu thap tgi Tram khi tugng thuy van rimg ciia Trucmg Dai hgc Lam nghiep. Sd li?u thu thap gom Iugng mua hing gid tir nam 1997 din nam 2015. Ngoai ra, sd Ii|u mua cdn dugc dilu tra bd sung tgi cac thdi dilm khic nhau bing thiet bj do mua tu ddng (tipping bucket rain gauge) cho cac tran mua vdi thdi gian do l i 5 phiit mdt lan cho cic tran mua khic nhau. Sd lieu thu thgp se dugc phan tich danh gia nham tim ra dac diem che dd mua cua khu vyc nghien ciiu. Sd lieu mua dong thdi dugc su dung nhim danh gii phin ling cua ddng chay theo cac tran mua khac nhau tgi khu vuc nghien cuu. Sd lieu mua dugc do theo phuang phip tu ddng l i 18 tran mua khac nhau tir thing 6 - 9 (2016).
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Hinh 2.3. Thiet ke 6 quan trac dong chay ffl. KET QUA NGHIEN ClJtJ, THAO L U ^
3.1. Dac diem che dg mua tai khu vyc nghiSn cihi
Sd lieu quan trie mua 21 nam Uen tuc tir nam 1995 tdi nim 2015 tgi Tram quan trac khi tugng Clia Trudng Dai hgc Lam nghiep dugc
tdng hgp tai hinh 3.1. Dya vao sd lieu thu dugc cho thiy, khu vuc nghien cuu cd lugng mua binh quan hing nam l i 1700 mm/nam. Nam cd lugng mua ldn nhat l i 1996 vdi lugng mua len tdi 2300 mm/nam, trong khi nam cd lugng mua nhd nhat la nam 1995 vdi chi 1300 mm/nam.
TAP CHI KHOA HQC VA CONG NGHE LAM NGHIEP SO 4-2017 67
Qudn ly Tii nguyen rimg & Moi trudng Khu virc nghien ciiu thugc tieu vimg khi hju 3 cua mien BJc Viet Nam, hang nam co 2 miia ro ret: mia mua thutog bit diu tir thang 4 dSn thang 10, miia kho bit d4u tir thang 11 dSn thang 3 nam sau. Thang co lu(?ng mua Ion nhat la thang 7, trung binh 304 mm/thang (dao dgng
2500 n
tit 115 toi 578 mm/n5m). Thang c6 lugng mm nho nhat la thang 1 v i i lu?mg mua trdng binh la 14 mm/thang (biSn dO dao d^ng tir 0 - 45 mm/thang). Cac thang miia mua tir thang 4 tiii thang 10 chiSm 89% tdng lugng mua hang nam ciia khu vuc (hinh 3.1).
I 15C
i
1995
300 1 2 5 0 1 2 0 0 1 •'^
% 100 -• 50
1997 1999
. 1
2001 2003 2005 2007 2009 2011
I
1 1 1 1
ill
•
1 1
II
2013 2015
1.
Hinh 3.1. Dgc diem Iirgng mira hing nam va h^ng thing cua Ichu virc nghien cuu 3.2. Dac dilm ddng chay mgt dat is cac dieu
Id^n che phu thurc vat khac nhau Ddng chay bl mgt tir hai d nghien ciiu phan ling nhanh vdi lugng mua. Khi lugng mua ldn thi ddng chiy mat dat gia cao (hinh 3.2).
Lugng mua trong thdi gian quan trac dao dgng tir 4 - 55 mm, trung binh 19,8 mm/tran, trong khi ddng chiy mat (± do l?ch chuin: SD ) cua dit rimg dao d^ng tii 0 - 1,6 ± 0.5, trung binh 0,4 mm/tran mua. Ddng chay mat (±SD) cua ciy bui dao dgng tu 0 - 5,3 ± L9, tnmg binh 1,7 mm/tr|n mua. He sd ddng chiy be mgt (±SD) Clia dit rung dao dgng tir 0 - 3,4 ± 1%, trung binh 1,2%, trong khi h§ sd ddng chay mat cua dat cay byi dao dgng tir 0 - 15,1 ± 5,2%, trung binh 5,9%. Dilu nay cho thiy sd
Iugng va he sd ddng chiy mat ciia cay bui cao hon so vdi dit trdng dudi tan rimg. Su khac biet niy cd y nghia thdng ke vdi gia trj p
<0,01.
Tdng lugng mua quan trac dugc sau 18 tran mua la 356 mm (hmh 3.3). Cung trong thdi gian dd tdng lugng ddng chay b l mat quan sat dugc trong dieu ki?n dat cay bui la 30,2 nun, ldn han 4,6 lin so vdi dilu ki$n dit rimg (6,6 mm). Kha nang phit sinh ddng chiy be mat dudi dat rtmg thip hon nhilu so vdi dieu ki§n cay byi che phu cd thl dugc giii thich thdng qua kha nang tham nudc cua dit dudi tan rung thudng cao hon so vdi dieu ki?n cay byi che hu (Dung, 2016) va lugng nudc giO lgi tren tin cao cua dit cd rimg che phu (Yin, 2014).
TAP CHI KHOA HQC VA C 6 N G N G H E LAM NGHIEP SO 4-2017
Qudn l^ Tdi nguyen rieng & Mdi trud'ng
1 2 3 4 5 6 7 8 9 10 11 12 13 U IS 16 17 18 Trai mtfa
3.2. D3c diem mira, d6ng chay mSt v^ h| &6 ddng chay mit d cac dieu Idf n che phu thiJrc vgt khic nhau
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50
40 I
e30 • ! a
20 I
10
1 2 3 4 5 7 8 9 10 11 12 13 14 15 16 17 18 Tiln mua
Blnh 3J. D$c diem dong cb&y mat va lirgng mira tich Ifly sau 18 tr|n mira d 2 Sihn ki^n che phii thuc vat khac nhau
TAP cat KHOA HQC VA CONG NGH| LAM NGHIEP SO 4-2017 69
Qudn ly Tdi nguyen rieng & Mdi tru&ng Trong c i 2 trudng hgp che phii (Plot 1: Dat trdng dudi tin rung va plot 2: Dit ciy bui che phu), ddng chay b l mat diu cd quan h? rit chat v i cd y nghta thdng ke vdi Iugng mua (hinh 3.4). Khi lugng mua tang ISn thi ddng chay be mat ciing tang. Tuy nhien Iugng gia tang ciia ddng chay mat trong dieu kien rimg che phii cham ban so vdi dilu kien cay bui che phu.
Nguang Iugng mua lam xuit hi?n ddng chay be mat \ai dit rimg la >10 mm/tran mua, vi Idn hem 8 mm/tran mua ciia dieu kien cay bui che phii. Dieu nay cd the giii thich nhd vao khi nang giu: nudc tren tin rimg thudng ldn
hon so vdi ciy bui thim tuoi. Cy the flieo nghien cim ciia Komatsu et al. (2008) cho bi6t lugng nudc toi da ma cay bui cd thl gift IJIK^J tren tan l i 15% lugng mua, trong khi tham thyc vit rimg cd the giii lgi 35 - 40%. Ngo^ ra, kit qua nghien ciiu ciia Yin (2014) ddng thai cho biet Iugng nudc giu lgi trSn tan cua rimg tai Niii Luot dao ddng tir 25 - 75%, trung binh 50% ciia trin mua. Ngoai ra, do do xdp cua dSt rimg cao han (55%) so vdi 47% d dat cay bui (bing 1) nen lim cho kha nang thim ciia dat rimg ldn hem dat cay bui. Vi thl Iugng nuoc hinh thinh ddng chiy be mat it hon.
a Plot 1: Bk nJrg 0 Piot2;:0<'tcaybui
•
0
y60
o / o
IT = 0.115a-05894 / R*= 0.8539. p < 0 . 0 1 / ^
° / °
0 ® /
/ y = 00284x-0 1944 R" = 0 S87; p<0.01
• __.——-"""'^
-1 \ • i . 1 .
I"
I, 2
0 10 20 30 40 50 60 Luqng mua (mmlrSn-i)
Hinh 3.4. Quan h | giira l u ^ g mua va doog chay be mkt ir hai dieu kif Q che phu Icfaac nhau tai khu vurc nghiSn cuu
3.3. Lugng dat xdi mon cua cac dieu kifn che phu thyc vSt khac nhau
Lugng dat xdi mdn trong c i hai dilu kien che phii deu cao hon khi Iugng mua Idn hon (hinh 3.5). Lugng dit xdi mdn (± Do l?ch chuin: SD) ciia dit rtmg dao ddng tir 0 -1,52 ± 0,5 g/2m^ trung binh 0,5 g/tran mua, trong khi dd lugng dat xdi mdn ciia ciy bui che phu cao han, dao ddng tir 0 - 4.7 ± 1,5g/2m^ tmng binh 1,2 g/tran mira. Su khac biet ve lugng dat xdi mdn Clia hai dilu kien che phii thuc vat cd y
nghia thdng ke khi gia tri p <0,01.
Sd tran mua quan trie trong thai gian nghien cuu la 18 vdi tdng lugng mua la 356 mm. Trong thdi gian dd tong lugng dat xoi mdn quan sat dugc d dit ciy byi l i 20,9 g, ldn han 2,5 lin so vdi dit rimg (8,3 g) (hinh 3.6).
Tdng lugng dit xdi mdn trong dilu ki$n ciy byi che phu ldn hern dit rimg cd thl la do ddng chay be mat ciia cay byi ldn han so vdi dat rimg.
70 TAP CHI KHOA HQC VA CONG NGHE LAM NGHIEP SO 4-2017
Qudn ly TdJ nguyen rung & Mdi tru&ng
•1 10- 1 20 .
| 3 0 . 0,40 • 3 so.
6 0 •
'1 'II 11 ' 1 rri'*ii'
-O- Plot 1 B^t rirng - • - P l o t 2 Dit cay byi
„ . « T » ^
7 a 9 10 11 12 13 14 15 18 17 18 Trgn mua
Hinh 3.5. Dac diem mua va lu-ong dit xdi mdn cua hai dilu kiSn che phu thin: v | t 25
* P l o t 1 BatrCma
• Rot 2, OatcaytJij
10 11 12 13 14 15 16 17 18 Tr^n mua
Hinh 3.6. D$c dilm mira vi l u ^ g dat xoi mon tich luy a cac dieu ki£n che phii thirc vat Idiic nhau
Lugng dat xdi mdn trong c i 2 dieu kien che nghia thong ke khi gii tri p < 0,01. Tuy nhien, phli diu cd quan h | chit vdi lugng mua (hinh ngudng lugng mua gay xdi mdn trong dilu 3.7a) va ddng chay b l mat (hinh 3.7b) theo kien ciy bui che phu (> 10 nun/tran) nhd hon ham hdi quy tuyen tmh. Khi lugng mua hoac so vdi dieu kien rung che phii (>I5 mm/tran) ddng chiy b l mit ting thl lugng dit xdi mdn (hinh 3.7).
dong thdi gia tang. Quan he niy tdn tgi cd y
TAP CHI KHOA HOC VA CONG NGHE LAM NGHIEP S 6 4-2017
Qudn ly Tdi nguyen rung & Moi tru&ng 5 1
20 30 4Q LiJongmuaimmtrSn^]
iW
V=Q-765a(-0,1371 R'=0539S.fK0-01
0 1 2 3 -J 5 6 DangchSy b4 mat (mm trSr')
Hmh 3.7. Quan h^ giua lirgrng dit xoi mon vdi (a) lirong mira vk (b) dong chay be mat 0* cac dieu Id^n che phii Ithdc nhau
IV. KET LUAN
Dya vao viec quan trac ddng chiy be mat va lugng dat xdi mdn d hai dieu kien che phii thuc vat khic nhau (dit rimg trdng va dit cay bui) cho 18 trgn mua, nghien ciiu da thu dugc nhung ket qui chinh nhu sau:
- Khu vuc nghien ciiu hing nam cd 2 mua rd ret: miia mua thudng bit diu tir thing 4 din thing 10, miia khd bit diu tir thing 11 den thing 3 nam sau. Lugng mua hang nam dao ddng tir 1300 tdi 2300 mm/nam, binh quan hang nam la 1700 mm/nam. Thing cd Iugng mua ldn nhat diudng la thing 7, trong khi thing I thudng cd lugng mua nhd nhit.
- Ddng chiy be mat cua dat cay bui che phu (he so ddng chiy la 5,9%) ldn hon gin 5 lin so vdi dat rimg (he so ddng chiy 1,2%). Ddng
chay be mat trong c i hai trudng hgp deu co quan he chat vdi lugng mua theo ham tuyen tinh. Nguong Iugng mua Iim xuat hien dong chiy b l mat vdi dit rimg >10 mm/tran va ldi hem 8 mm/trgn vdi dieu ki?n cay bui che phii.
- Lugng dit xdi mdn ciia ciy byi che phi (0,6 g/m^/tran mua) ldn hem 2,5 lin so vdi da cd rimg che phii (0,25 g/m^/trgn mua). T6ni lugng dat xdi mdn trong thdi gian nghien cin cua cay bui che phii l i 20,9 g, ldn han 2,5 lai dit rimg che phu (8,3 g). Lugng dit xdi moi trong ca hai dieu kien che phii deu phy thuO vao lugng mua va ddng chiy be mgt. Kt Iugng mua va ddng chay b l mat ting thi lugn dat xdi mdn gia tang.
- Ddng chay mat v i lugng dat xdi mo
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trong dieu kien che phii ciy bui ldn ban rim TAP CHI KHOA HQC VA CONG NGH$ LAM NGHIEP S 6 4-2017
Qudn ly Tdi nguyen rieng & Mdi tru&ng cfaii yeu ia do kha nang giu lgi nudc tren tan va
lugng nudc tham cua dit rimg ldn han so vdi cay byi. Dilu nay cho thiy vi?c bio v? ldp che phil rimg la rit quan trgng nhim bio ve va dilu tilt nudc cho khu vyc dit ddc va vung diu ngudn.
TAI H | ; U THAM KHAO
1. Bui Xuan Dung, 2016. Dgc dilm thim mioc cua dit duoi mgt so loai hinh sii dimg dit tai niii LuSt, XuSn Mai, Hk Ngi. Tap chi Khoa hoc vd Cong nghe Ldm nghiep, 4:41-5S.
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4. Anh, P.T.Q., T. Gomi, L.H. MacDonald et al, 2014. Linkages among land use, macronutrient levels, and soil erosion in northern Vietnam: A plot-scale study.
Geoderma
btq3://dx.doLorg/10.10I6^.geoderma.2014.05.011, II pp.
5. Dung BX., 2016. Soil infiltration charactensncs of different landuse types at Luotmountaiti, Xuan Mai, Ha Noi. Forestry Science and Technology Journal, 4: 47-58 (Vietnamese with abstract m English).
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Relationship between annual rainfall and interception ratio for forests across Japan. Forest Ecology and Management - volume 256, issue 5, 1189 -1197.
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10.1029/2008WR007270
10. Mohammad, A.G., Adam, M.A., 2010. The i n t a c t of vegetative cover type on runoff and soil erosion under different land uses. Catena 81, 97-103.
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Estimation of soil splash detachment rates on the forest oor of an umnanaged Japanese cypress plantation based on eld measure - ments of throughfall drop sizes and velocities. Catena 72, 348-361.
13. Podwojewski, P., Orange, D., Jouquet, P. et al, 2008. Land-use impacts on surface runoff and soil detachment wiihrn agricultural sloping lands in northern Vietnam. Catena 74,109-118.
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O V E R L A N D F L O W AND S O I L E R O S I O N F R O M H I L L S L O P E P L O T S A T L U O T M O U N T A I N - XUAN M A I - H A N O I
Bui Xuan Dung\ Phung Van Khoa^
'^Vietnam National University of Forestry S U M M A R Y
To detennine overland flow and soil erosion from hillslope plot, we have installed two plots with 2m^ (2 m x 1 m) area under plantation forest (plot 1) and shrub land (plot 2) in the west mountains of Hanoi. Overland flow and soil erosion are observed continuously for 18 different storni events lasting from June 15 to September 23, 2016. By using the R software to analyze the collected data, main findings of this smdy are including: (I) Aimual rainfall of study site ranged fi'om 1300 to 2300 mm, is divided into two seasons: the rainy season fi-om April to October and the dry season is from November to March; (2) Overland flow coefficient is 5.9% in slmids cover, nearly five times larger than one ofthe forest cover (1.2% overland flow coefficient). Threshold of rainfall that makes overland flow is more than 10 mm/storm event m forest cover and more than 8 mm/stonn event for shrub cover conditions; (3). The amount of soil erosion in shrub cover (0.6 g/m^/stonn event) is 2.5 times greater than that of forested cover (0.25g/mVstorm event); (4) The overland flow and soil erosion in shrubs cover is larger than one of forest cover, is mainly due to the water-holding capacity in canopy (intercepted by canopy) and infiltration of forest cover is larger than one of shrubs cover. This shows that l i e conservation of forest cover is important to protect and regulate water resource in headwater.
Keywords: Overland flow, runoff, soil erosion, vegetadon cover types.
Ngay nhin bai Ngay phan bien Ng^y quyet dinh dang
06/02/2017 13/02/2017 24/02/2017
TAP CHI KHOA HQC VA CONG NGHE LAM NGHIEP S 6 4-2017
