Thuc Hanh Sinh Thai Rung(1)

Thc hnh sinh thi rng

THC HNH

SINH THI RNG

P

hn thc hnh sinh thi rng gm 11 bi, tng ng vi 15 tit chun, tp trung vo mt s chng ca mn hc. Mi bi bao gm t 1 - 2 kiu. Sau mi bi c cc ch dn gii v mt s cu hi m sinh vin cn phi tr li. Nhng bi tp ny c ngha nh nhng bi tp mu nhm gip sinh vin lm quen vi cch thc thu thp v phng php x l s liu v sinh thi rng. hon thnh tt cc bi tp ny, trc ht sinh vin cn c tht k l thuyt, chun b y v ghi chp, bt mc, bt ch v giy v...

Trc khi thc hnh, sinh vin s c gio vin hng dn thc hnh gii thiu mc ch, mc tiu v cch thc gii tng bi tp. Sau mi sinh vin phi t mnh lm cc bi tp v np li kt qu cho gio vin vo mt thi gian thch hp. Hon thnh y tt c cc bi thc hnh trong cun sch ny l iu kin tt gip cho sinh vin nm vng mn hc v d thi c kt qu tt.

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1


M T CU TRC RNG BNG BIU PHU DIN(1)1.1 MT S K HIU QUY C

Phn I

Trong o cy v lm phn, n gin cho vic ghi chp v trnh by kt qu ngi ta dng mt s k hiu quy c sau y (hnh 1.1): 1. Chiu cao thn cy c k hiu bng ch H, n v o l mt. Chiu cao vt ngn c k hiu bng ch HVN, m. Chiu cao thn cy di cnh ln nht cn sng c k hiu bng ch HDC, m. 2. ng knh thn cy c k hiu bng ch D, n v o l cm. Trong o cy, ng knh thn cy c o nhng v tr khc nhau: 0 m, 1,3 m cch mt t, 1/2Hvn v 3/4Hvn...- tng ng c k hiu l Do, D 1.3, D1/2, D3/4... ng knh thn cy ng hay cy cy cn sng (standing trees, alive trees) thng c o v tr 1,3 m cch mt t v c gi l ng knh ngang ngc (D1.3, m).

Dtmax

LT HVN HDC

D1.3

3. ng knh y tn cy v cy v cc k hiu v ch tiu o l DTmax, m. Hnh 1.1. Nhng b phn ca tr ln nht c k hiu m 4. Chiu di tn cy tnh t y tn cy n vt ngn, c k hiu bng ch LT, m. 5. Tit din ngang thn cy v lm phn c k hiu tng ng bng ch g v G, n v o l m2/ha.(1)

Profile - diagramme

2


6. Th tch thn cy v tr lng g ton lm phn c k hiu tng ng bng ch V v M, n v o l m3/ha. 7. Ngoi ra, ngi ta dng ch q ch h s hnh dng thn cy, ch f hnh s; a hoc A - tng ng l tui cy v lm phn, n v l nm hay cp tui; Zt v t - biu th tng ng lng tng trng thng xuyn v lng tng trng bnh qun ca mt nhn t iu tra no (v d Zd, Zh, Zg v Zv). 8. Mt lm phn c k hiu bng ch N, n v l cy/ha. Khng gian dinh dng ca mt c th cy rng c k hiu bng ch F, n v l m2/cy. Khong cch gia cy ny n cy kia c k hiu bng ch L, n v l m... 1.2. BIU PHU DIN RNG V NGHA CA N 1. Khi nim v ngha ca biu phu din rng Biu phu din rng l bn v m t s phn b v sp xp (hay cu trc) ca cc thnh phn qun x thc vt theo chiu thng ng v chiu nm ngang. S phn b v sp xp ca qun x thc vt theo chiu nm ngang c gi l cu trc ngang ca rng (hay s phn b ca rng theo chiu nm ngang). Ngc li, s phn b v sp xp ca qun x thc vt theo chiu thng ng c gi l cu trc tng th hay cu trc ng ca rng. Nh chng ta bit, cu trc rng khng ch phn nh quan h gia cc loi cy vi nhau m cn gia cy rng vi cc nhn t sinh thi. V th, bn cnh vic m t s phn b ca cy rng theo chiu ng v ngang, nh lm hc cn m t trn biu phu din mt s nhn t sinh thi c nh hng cn bn n s hnh thnh rng. V d: a hnh, t, kh hu - thy vn... Phng php m t qun x thc vt bng biu phu din c Richards v Davis s dng ln u vo nm 1933 - 1934 nghin cu thm thc vt vng nhit i Moraballi ca Guyana thuc Anh. V ngha, biu phu din gip nh lm hc pht hin v phn tch: - cc thm thc vt; - c tnh sinh thi ca loi cy; - s phn b ca cc loi cy theo chiu ng v ngang; - s hnh thnh tng th v s dao ng ca cc loi cy theo ma; - s kt nhm (mi lin h) gia cc loi cy; - kt cu mt v mng hnh phn b ca cy rng trn mt t; - quan h ca thm thc vt vi mi trng; - d bo khuynh hng bin i ca cu trc rng; - tuyn chn cy trong khai thc chnh v cht nui dng rng; - d kin cc bin php x l rng... 2. Phng php v biu phu din rng v biu phu din rng, trc ht chng ta cn xc nh chnh xc v tr v kch thc ca di v trn thc a. V tr ca di v trn thc a phi m bo hai yu cu c bn sau y:

3


(a) Di v phi nm trn trong mt kiu thm thc vt nht nh. Khi cn m t s chuyn tip gia hai kiu thm thc vt th di v c th cha hai kiu thm thc vt khc nhau. (b) Di v phi mang tnh cht in hnh hay i din cho cu trc ca thm thc vt v iu kin hon cnh (a hnh, t, kh hu, tc ng ca ngi v ng vt...) hnh thnh thm thc vt. Kch thc ca di v phi c chn la mt cch thch hp sao cho m t c y nhng c trng c bn ca thm thc vt v mi trng, cng nh m bo cho bn v cn i v p... Ty theo kiu thm thc vt v trng thi ca n, ngi ta chn di v c chiu di khc nhau. m t rng t nhin hn loi, di v phi c chiu di t 50 60 m, chiu rng t 5 10 m. i vi rng trng, do cy rng phn b ng u v mt dy, di v c chn theo kch thc 30 x 10 m. i vi thm cy bi v thm c, di v c chn l 5 x 15m... v c biu phu din rng, chng ta cn thu thp nhng thng tin sau y: v tr cy trong di v, tn cy, ng knh thn cy (D 0, D1.3, Dtmax), chiu cao thn cy (HVN, Hdc, Lt...). Sau bng phng php v hnh hc khng gian, nhng cy trong di v c chuyn t thc a vo bn v trn giy. V tr (to ) ca nhng cy trn mt di v c xc nh bng h to vung gc ( Cc) hoc h to mt cc, trong gc to c quy nh v tr giao nhau gia hai cnh ca di v (thng thng l im giao nhau gc tri phi di ca di v). Nhng ghi ch khc c trnh by trn hnh 1.2. Lu : (1) Mun c bn v p v r rng, sinh vin cn chun b giy v k thut hoc giy k vung (giy k milimt), bt ch (mu, en), bn v, thc k, ty... Trc rng phi c v theo ng quy tc v hnh hc khng gian. Khi v trc , ta c th dng mu sc khc nhau biu th cc thnh phn nh l, thn, cnh... (2) Trn mt ct ng v ngang, chng ta c th dng cc nt t on hay nt chm chm biu th tn l ca nhng cy nm v tr phi sau cy khc (k t v tr chng ta ang ng) hoc nhng cy nm di tn ca nhng cy cao hn. (3) Khi m t quan h ca cc loi cy g vi thm cy bi v thm c trn cng mt bn v th t l v cy bi v thm c phi ln hn cy g. (4) phn trn hoc di ca biu (hnh 1.4), cn dnh mt khong thch hp ghi ch v a hnh, v biu kh hu a phng v tn (gm c tn a phng v tn khoa hc) ca cc loi cy. c bn v p, d c, tn ca loi cy c vit tt theo mt quy c nht nh, thng thng l mt hay hai ch ci u ca tn cy (tn a phng hoc tn khoa hc).

4


H, m 20

10

0m

Mt ct ng

Gc to 30 m 0m 15mDr S

4.0 m Mt ct ngang

10 m

Hnh 1.2. Phng php v biu phu din ng v ngang ca qun x thc vt rng K hiu tn cy: Dr (Du ri), S (Sao en)...

1.3. PHN CP SINH TRNG CY RNG V TA THA T NHIN CA QUN TH

Bi tp 1 1. Theo s liu bng 1.1, hy v trc rng theo phng php ca Davis v Richards (1934). T l v quy nh nh sau: trc tung (Y) b tr chiu cao cy theo t l 1:200 (1 cm = 2,0 m); trc honh (X) v ng knh thn cy v ng knh tn l - t l v quy nh l 1:100 (1 cm = 1,0 m). 2. Theo s liu ca bng 1.2, hy in cc s liu tnh ton vo nhng ct trng v v th biu din s bin i s cy (N, cy/ha) v khng gian dinh dng bnh qun ca mt cy (F, m2/cy) theo tui lm phn (A, nm). Tnh

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khong cch trung bnh gia nhng cy li nui dng (L, m) ty thuc cp t.

T giy vPhc a l a hnh

Ghi ch tn cy

Biu kh hu Gaussen - Walter

BIU PHU DIN NG CA QUN TH THC VT (T l : 1/200)

H,m

0m

V tr v tng cy bi phng i (T l 1/50)

V tr v tng c quyt phng i (T l 1/20)

0 m 10 m

10

20

30

40

50

60

BIU HNH CHIU NM NGANG CA TN CY (Cng t l vi biu mt ct ng ca qun th - 1/200)

Hnh 1.4. Quy c cch b tr v tr v biu qun th thc vt Biu phu din a hnh v t (Phng theo Thi Vn Trng, 1978) (t l 1/50 - 1/100)

Hng dn gii bi tp 1 1. Khi v th v s bin i mt v khng gian dinh dng theo tui lm phn, hy t s cy (N/ha) v khng gian dinh dng trung bnh ca mt cy (F, m2/cy) trn trc tung bn tri tng ng theo t l 1 cm = 1000 cy/ha v 1 cm = 0.5m2. Tui ca qun th c b tr trn trc honh vi t l 1 cm = 5-10 nm (hnh 1.3).

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Bng 1.1. c trng hnh dng cy g v cy biTT (1) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Loi cy (2) sp sp sp thng Thng

X (m) (3) 8,0 31,0 21,0 2,5 25,0 16,0 12,5 28,0 23,0 19,0 24,0 25,0 27,5 26,0 14,5 10,0 26,0 4,0

H (m) (4) 30,0 26,0 25,5 23,0 22,5 22,5 20,0 19,0 17,0 17,0 16,0 1,5 2,5 1,0 25,5 10,0 26,0 20,5

ng knh thn cy ti : 1,3m 0,5H 0,75H (5) (6) (7) 50 30 21 34 26 16 28 20 13 26 19 12 26 19 12 26 19.5 12 20 16 12 20 16 12 12.5 9 6 11.5 9 6 32 18,0 10 40 28 16 30 22 13 28 20 13 24 16 12

c trng tn l, m: Lt (8) 12,0 9,0 9,5 7,0 6,5 7,5 5,0 4,5 3,0 3,0 14,0 1,0 1,0 0,5 11,5 3,0 11 5,5 Hdc (9) 18 17 16 16 16 15 15 14.5 14 14 2 0,5 0,5 0,5 14 7 15 15 Dt (10) 6,0 4,5 4,0 3,5 3,5 3,5 3,0 3,0 2,0 1,5 1,8 1,2 1,5 0,8 6,5 4,0 4,0 3,5 Hdm (11) 22,0 18,0 18,0 18,0 18,0 17,0 16,0 15,5 14,0 12,0 12,0 16 19 18 16Dtmax

(12) 6,5 6,0 4,5 3,5 3,5 4,0 2,0 3,5 2,5 2,0 2,5 7,4 4,5 5,0 4,5

* Ghi ch : X - khong cch t gc to n cy th I ; Sp - cy bi. Lt - Chiu di tn l ; Hdc - chiu cao di cnh ln nht cn sng; Hdm - chiu cao ng vi v tr ng knh tn ln nht (Dtmax).

Bng 1.2. S bin i s cy v khng gian dinh dng ca mt cy theo tuiLoi cy Thng Tui (nm) 10 20 30 40 50 60 70 80 90 100 Cp t I, P = 1.0 N, cy/ha F hin cht (m2) cn 8600 1,2 4960 3640 ... 2950 ... 2100 1620 1220 910 750 655 605 L (m) Cp t II, P = 1.0 N, cy/ha F hin cht (m2) cn 10000 1,0 7600 2400 1,3 5010 ... ... 3100 2100 1550 1300 1100 910 800 L (m)

2. Din tch dinh dng trung bnh ca mt cy tnh theo cng thc: F, m2/cy = (1.1) 3. Khong cch trung bnh gia nhng cy li nui dng tnh theo cng thc: Ltb, m/cy = = 1,074 (1.2) 4. Da vo hnh v v l thuyt, sinh vin t phn chia cp sinh trng cy rng theo phng php ca Kraft (1884). T cho bit nhng cy mc

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trong rng c hnh thi khc vi cy mc ngoi t trng nhng c im no ? 5. Trong mt vi trng hp, ngoi v mt ct ng v ngang ca qun x cy g, ngi ta cn m t c s phn b cy bi, thm c, dng a hnh v t, s phn b r cy...Trong trng hp ny, lp cy bi v thm c c v vi t l phng i l 1/20 - 1/50.Phng php phn cp mc sinh tring cy rng ca G. Kraft Kraft phn chia ton b cy g trong mt qun th thnh 5 cp sinh trng c bn , hoc cp u th v cp b chn p . Cy rng c chia thnh 5 cp sinh trng theo th t gim dn sc sng l I , II, III, IV v V. Ch tiu c Kraft s dng phncp sinh trng bao gm: v tr tn cy trong tn rng, ln v hnh dng tn l, kh nng ra hoa qu, tnh trng sinh lc, cy cn sng hay cht... Mi ch tiu c mt h thng tiu chun nhn bit v nh gi. Di y l tiu chun cc cp cy. Cy cp I. l nhng cy cao nht, to ln nht, tn l pht trin tt nht. Chiu cao ca chng bng 1,2 - 1,3Hbq vi Hbq l chiu cao bnh qun lm phn. y l nhm cy sinh sn mnh nht, cho cht lng ht tt nht. Cy cp II. Nhm ny gm nhng c th sinh trng v pht trin tt, nhng c cc tiu chun thp hn cy cp I. So vi chiu cao bnh qun ca qun th (Hbq), chiu cao cy cp II t 1,1 - 1,15 Hbq. Cy cp II c kh nng sinh sn tt, cht lng di truyn tt, ta cnh t nhin tt, v thng chim s lng c th kh ln hn cy cp I. Cy cp III. y l nhng c th c kch thc v tnh trng sng mc trung bnh, chiu cao t 0,95 - 1,0Hbq, lng hoa qu t 35-40% so vi cy cp I. Cy cp III c s lng c th ln nht trong lm phn. Cy cp IV. l nhng cy b chn p nhng vn tham gia vo tng thp ca tn rng. Cy cp IV gm hai cp nh : + IVa - cy c tn hp nhng u ; + IVb - cy c tn dng c lch v mt pha. Ni chung, cy cp IV khng ra hoa qu. Nu loi b cy cp IVb ra khi tn rng th khng li l trng trong tn rng ; ngc li, loi cy cp IVa s to ra l trng trong tn rng. Cy cp V. y l nhng cy sinh trng rt km, cy ang cht hoc cht. Cy cp V cng gm hai phn cp nh: + Cp Va: cy ang cht nhng mt vi b phn cn sng; + Cp Vb: cy cht, cy kh nhng cha b gy. Ni chung, nhm cy cp V c gi l nhm cy b o thi v s b o thi t nhin. Nu loi b cy cp V th khng li l trng trong tn rng.

N, (ngn cy/ha)

7 6

F,m2/cy

Hnh 1.3. S T bi tp 1, sinh vin cn tr li nhng cu hi v din bin dinh mt theo sau y: i dng (N cy/ha) tch 2 1. Thi k no trong i sng ca rng xy ra tui rng (F, m2/cy) s o thi t nhin mnh nht, v sao? 0 2. Nhng nguyn nhn gy ra s phn ha v ti tha cy rng. Hy cho bit bin php k thut lm sinh lm gim cc hin tng ? 0 10 20 30 40 50 60 70 80 90 100 tui, (nm)

4

8


3. Phn cp sinh trng cy rng c ngha g ? 4. v c biu phu din m t kt cu rng theo chiu ng v ngang, chng ta cn thu thp nhng thng tin no; ngha ca biu phu din rng ? * * *

Phn II RNG, NH SNG V NHIT Bi tp 2 1. Hy phn bit loi cy a sng v loi cy chu bng; cho bit phng php xc nh chng ? 2. T s liu cho bng 2.1, hy v th phn b bc x mt tri theo ba thnh phn: phn x, lt qua tn rng v phn b tn rng hp thu.Bng 2.1. Phn b bc x tng s trong tn rng, tnh theo %

di sng nh sng (m) 0,40 0,50 0,55 0,60 0,68 0,75 0,80 0,90 1,00

Cc thnh phn bc x : phn x, % lt qua, % hp thu, % 2,0 3,5 5,0 3,6 3,0 44,0 45,0 46,0 47,0 3,0 3,5 4,0 5,0 6,0 10,0 18,0 15,0 16,0 95,0 93,0 91,0 91,4 91,0 46,0 43,0 39,0 37,0

TN

BHQ

HN

100i qua, % Hp thu i qua Phn x

0

Phn x, %

0 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 m

9

100%

Hnh 2.1. Phn b bc x mt tri khi i qua tn rng


Theo th hy ch ra ranh gii bc x quang hp c (PAR)1 v bc x hng ngoi. T l ve theo trc honh 1 cm = 0,05 m, theo trc tung 1 cm = 10%. Khi v th cn b tr trc tung bn phi theo th t tng dn t 0 100%, cn trc tung bn tri ngc li t 100 - 0%. Phn di ca th biu th phn nh sng phn x, pha trn - phn nh sng lt qua, cn gia l phn nh sng c rng hp thu (hnh 2.1). 3. Bng 2.2 ghi li cng nh sng di tn rng Du song nng tm cao 2,0 m cch mt t. T s ca cc tr s trong bng 2.2 l phn trm cng nh sng so vi ni trng, cn mu s l cng nh sng tnh bng lux (ngn lux). T bng 2.2, hy cho nhn xt v i sng cy ti sinh Du song nng di tn rng ?Bng 2.2. Phn b cng nh sng di tn rng tng ng vi cy con Du song nng c tui khc nhau

Tui cy con (nm) v cng nh sng :

Loi cy

Mc chu bng

Du song nng Bi tp 3

yu trung bnh cao

1-2 35-40/13 22-26/8 10-12/4

3-4 45-50/17 32-36/12 16-20/7

5-6 55-60/22 40-50/16 30-32/11

T s liu ca bng 2.3, hy xc nh nhng ch tiu sau y: 1. Chi ph nhit lng cho thot hi nc ca 1 ha rng v ng c sau ma sinh trng ? 2. Chi ph nhit lng cho bc hi nc vt l do tn rng v ng c gi li sau ma sinh trng ? 3. Chi ph nhit lng hnh thnh lng tng trng thc vt khi kh tuyt i ca 1 ha rng v ng c sau ma sinh trng. T tnh: - Hiu sut chuyn i nng lng K K= (2.1) - Hiu sut s dng nng lng K+ K+ = (2.2) Trong cng thc 2.1 v 2.2 ta c: t - nng sut ta nhit trung bnh ca 1 kg thc vt khi kh tuyt i ( y gi nh t = 5000 kcal/kg); m - lng tng trng thc vt khi kh tuyt i ca 1 ha rng v ng c sau ma sinh1

Photosynthesis Active Radiation = PAR

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trng, n v l m3/ha hoc kg/ha; i l t sut ht nng lng ca rng v ng c (i = 0,5); B - cn bng bc x mt tri trong ma sinh trng, hoc c nm.Bng 2.3. c im ca rng v ng c. Lng ma (mm), chi ph nc (mm) cho thot hi nc ca thc vt v bc hi nc vt l t tn cy v t...

TT1

i tng2

Tui (nm)3

m (t/ha)4

B (kcal/cm2) ma nm5 6

OC (mm)7

Trong ma sinh trng O,mm q,mm8 9

P (mm)10

1 2 3

Rngng c

Rngng c

Rngng c

60 80 100 -

6,6 2,5 6,2 3,0 12,0 3,6

27,8 27,8 35 35 55 55

36 36 45 45 69 69

650 650 480 480 1500 1500

100 68 172 -

30 165 56 170 183 280

290 200 260 260 450 400

Ghi ch: + OC - lng ma ri, mm/nm hoc ma sinh trng; + O - lng nc c tn rng gi li sau bc hi vt l, mm; + p - lng nc chi ph cho thot hi nc ca thc vt, mm; + q - nc bc hi vt l t t, thm mc v thot hi nc ca cy bi v thm c, mm; + Mt s k hiu khc xem bi tp 4.

4. Hiu sut s dng nng lng ca rng non thng c tr s rt thp. Theo anh (ch), cn phi lm g tit kim ngun nng lng mt tri chiu n 1 ha rng v ng c. 5. Nhit trao i hon lu gia rng, ng c v khng gian xung quanh ? 6. Hy so snh cn bng bc x ca 1 ha rng v ng c. Nhng lm phn c tui v cu trc khc nhau c nh hng n cn bng bc x ca 1 ha rng nh th no ? 7. Cho bit ngha sinh thi ca rng trong s m bo cn bng bc x mt t ? Hng dn gii bi tp 3 1. Lng ma o bng mm, do khi tnh ton cn phi i ra n v trng lng l kilgam hoc tn. 2. Tnh lng nhit m 1 ha rng v ng c nhn c trong mt ma sinh trng v mt nm. 3. Chi ph nhit lng cho thot hi nc (tim nhit bc hi) ca 1 ha rng v ng c sau ma sinh trng bng lng nc thot hi ca thc vt nhn vi lng nhit cn thit lm thot hi ht 1 kg nc trong iu kin nhit nht nh ( y gi nh nhit bnh qun l 150C). Bng cch tng t nh trn, c th tnh c chi ph nhit lng cho bc hi nc vt l (hin nhit) do tn rng v ng c gi li sau ma sinh trng. 4. Lng nhit to ra tng thc vt khi ca rng v ng c trong ma sinh trng bng kh nng to nhit ca 1 kg thc vt khi kh tuyt i (t11


= 5000 kcal/kg) nhn vi tng lng thc vt khi (m) c rng v ng c to ra trong ma sinh trng. 5. Thay cc s liu vo cng thc 2.1 v 2.2 tnh hiu sut chuyn i nng lng K v hiu sut s dng nng lng K+. 6. Da vo phng trnh cn bng nhit rng s bit c nhit trao i hon lu (hin nhit) gia rng, ng c v khng gian xung quanh.

* * *

Phn III QUAN H GIA RNG VI NCBi tp 4 Theo s liu ca bng 3.1(a, b), hy tnh cn bng nc trong mi lin h vi tui rng v ng c ? Cho bit:

m (ct 2) l khi lng g m. TVK (ct 3) l thc vt khi trng thi kh tuyt i. OC (ct 4) - lng ma lt qua tn rng n mt t. TT (ct 12) l bc hi tng s (p + q, mm). Ct 13 l chi ph nc hnh thnh g thn cy. Ct 14 l chi ph nc hnh thnh tng lng thc vt khi v thot hi nc ca thc vt.

12


Lng nc cn thit hnh thnh 1 tn thc vt khi kh tuyt i l 0,55 3 tn/m , tng t Lng nc lm m 1 tn thc vt khi kh l 1,15 tn. Tng cng lng nc cn thit hnh thnh v lm m 1 tn thc vt khi kh tuyt i (k c cy g v thm c) l 1,7 tn nc/1 tn thc vt khi. T trng g m (t/m3) c v ca mt s loi cy g nh sau: Thng l 0,403 (thn), 0,410 (cnh v nhnh), 0,380 (r cy); Si l 0,561 (thn), 0,540 (cnh v nhnh), 0,530 (r cy). T trng g kh tuyt i: Thng 0,530 t/m3; Si 0,680 t/m3. B v Bn - tng ng l cn bng bc x trong ma sinh trng v c nm; Oc - lng ma ri c nm.

Bng 3.1a. Cn bng nc rng Thng v ng cTui, nm 1 20 30 40 50 60 70 80 90 100 .c mg m (m3/ha)

(OC = 560mm/nm; B = 29kcal/cm2/ma; Bn = 37 kcal/cm2/nm)Oc TVK (t/ha) 3 4,4 6,0 6,5 6,9 6,8 6,6 6,2 5,7 5,5 3,0 mm 4 460 442 440 445 450 452 454 456 460 560 t/h a 5 7.5 (*) ... t m m 6 75 ... O mm 7 100 .... q mm 8 80 65 65 68 70 72 74 76 78 160 r mm 9 40 20 19 20 20 20 20 20 20 100 s mm 10 119,2 103,0 87,8 83,7 97,7 110,8 126,8 142,9 151,0 109,5 p mm 11145,8 ...

TT mm 12225,8 ...

2 5,1 7,3 7,9 8,5 8,4 8,1 7,7 7,0 6,6 -

t+p (mm) g TV K 13 14180,8 ... 220,8 ...

By(mm)

15 420 ...

(*) Cc tr s ct 5, 6, 7 v 11 - 15 l tr s tnh ton mu

Bng 3.1b. Cn bng nc rng Si v ng c(OC = 530mm/nm; B = 33kcal/cm2/ma; Bn = 42 kcal/cm2/ma) mTui, nm G m (m3/ha) TVK (t/ha)

Ocmmt/ha

tmm

Omm

qmm

rmm

smm

pmm

TTmm

t+p (mm)g TV K

Bymm

120 30 40 50 60 70 80 90 100 120 140 160 .c

27,0 7,6 8,1 8,2 8,3 8,3 8,0 7,8 7,4 6,8 6,0 5,3 -

38,9 9,5 10,1 10,2 10,3 10,2 10,0 9,6 9,2 8,4 7,5 6,8 3,6

4472 466 464 464 464 465 466 467 468 469 470 472 530

5

6

7

876 72 71 71 70 70 71 72 73 78 82 88 170

918 15 14 14 13 13 14 14 15 16 18 20 106

1092,5 85,4 80,3 82,3 84,2 86,3 86,3 87,4 96,4 102,6 118,7 134,6 46,4

11

12

13

14

15

Hng dn gii bi tp 4 Nhng ni dung cn tnh ton:13


1. Lng ma c tn rng gi li (ct 7) v phn trm so vi tng lng ma ri bng lng ma tr i phn lt qua tn rng, ngha l O = Oc Oc. 2. Lng nc chi dng cho s hnh thnh thc vt khi hng nm (ct 5 v 6): t = t1 + t2 , trong t1 = ct 3 * 0,55tn nc, t2 = ct 3*1,15 tn nc, hay t = ct 3*1,7 tn nc. Sau i n v tn nc/ha ra mm nc/ha. 3. Chi ph nc cho thot hi nc ca thc vt c xc nh theo phng trnh cn bng nc: OC = O + p + q + r + s + t u, mm ; (3.1) trong : OC - lng ma ri, mm/nm hoc ma sinh trng; O - lng nc c tn rng gi li sau bc hi vt l, mm; p - lng nc chi ph cho thot hi nc ca thc vt, mm; q - lng nc bc hi vt l t t, thm mc v thot hi nc ca cy bi v thm c, mm; r - dng chy trn b mt t, mm; s - dng chy ngm trong t, mm; t - chi ph nc hnh thnh thc vt khi (t1, mm) v lm m g (t2, mm), vi t = t1 + t2; u - chi ph nc b sung vo dng nc ngm v lm m t (u = o, mm). T cng thc 3.1, ta c: p = OC - O - r - q - s - t - u, mm. 4. Tnh lng bc hi nc tng s (ct 12), ngha l bc hi vt l v thot hi nc ca thc vt: TT (ct 12) = ct 8 + ct 11 = p + q, mm. 5. Tnh chi ph nc cho s hnh thnh lng tng trng hng nm ca phn g thn cy (ct 13) v hnh thnh tng thc vt khi (ct 14) trng thi kh tuyt i, n v l tn nc/tn thc vt khi. 6. Ct 13 = (ct 2*d*1,7)+ p, vi d = 0,403 tn; 7. Ct 14 = (ct 3*1,7) + p. 8. Xc nh m tng s ca t By (ct 15): By = OC - O - r, mm (3.2) hoc By = p + q + s + u. (3.3) 9. Tnh chi ph nhit (theo phn trm) cn thit cho s thot hi nc ca thc vt so vi cn bng nhit trong ma sinh trng v tng lng nc bc hi c nm so vi cn bng nhit c nm (cho bit lng nhit cn thit lm bc hi ht 1 kg nc nhit 150C l 589 kcal). Cch tnh ton nh sau: Trc ht, cn phi tnh lng nhit m 1 ha rng nhn c trong mt ma sinh trng v c nm. Tip theo, chia lng nhit cn thit lm thot hi nc ca thc vt (hoc bc hi tng s) cho lng nhit m 1 ha rng nhn c trong mt ma sinh trng (hoc c nm). Nhng kt qu tnh ton c in vo cc ct trng ca bng 3.1. T v nhng th v chi ph nc hnh thnh tng thc vt khi hng nm v thc vt khi hng nm ca ring phn thn cy. C hai ng cong ny c v trn cng mt th; trong trc honh t tui rng vi t l 1 cm =10 nm, cn trc tung t lng nc vi t l1 cm = 100 tn nc. T nhng kt qu tnh ton, hy a ra mt s nhn xt v:14


(a) Cn bng nc ca rng v ng c, vai tr ca rng i vi s n nh cn bng nc ? (b) Nhu cu nc ca rng thay i theo tui nh th no ? (c) S thiu ht nc trong t gy nh hng r nht cho cy rng vo giai on tui no, ti sao ?.

Phn IV RNG V KHNG KHBi tp 5 1. Theo s liu ca bng 3.1, hy xc nh s hp thu CO2 v gii phng O2 ca 1 ha rng Thng, rng Si v ng c tui khc nhau. Nhng kt qu tnh ton ghi vo mu biu 4.3. 2. Cho bit ngha ca rng trong vic m bo cn bng cc cht kh ca kh quyn: hm lng CO2, O2, s thi phytonxt, s in ha O2 ? Hng dn gii bi tp 5 1. tr li bi tp 5, trc ht sinh vin cn xem li l thuyt v nhng s liu ghi bng 3.1 v 4.1.Bng 4.1. ng lng hp thu CO2 v gii phng O2 vo khng kh khi hnh thnh 1 tn thc vt khi kh tuyt i ca mt s loi cy

15


Loi cy Thng Si ng c

Hp thu CO2 (tn) 1,854 1,792 1,722

Gii phng O2 (tn) 1,442 1,371 1,302

2. Mun xc nh c lng CO2 v O2 trong qu trnh quang hp v h hp ca thc vt, cn bit ng lng hp thu CO2 v gii phng O2 tng ng vi cc qu trnh ny. Nh bit, s hp thu CO2 v gii phng O2 trong hot ng sng ca rng l t l thun vi lng tng trng thc vt khi hng nm. Nh phn tch thnh phn ha hc ca g thn cy, cnh cy, l, hoa v qu, v qua phng trnh nhit ha hc c th bit c ng lng hp thu CO2 v gii phng O2 trong qu trnh quang hp ca thc vt (xem bng 4.1 v 4.2). Do , tng lng hp thu CO2 v gii phng O2 ca 1 ha rng sau ma sinh trng v c nm tng ng bng tng lng thc vt khi kh tuyt i nhn vi ng lng hp thu CO2 v gii phng O2 trong khi hnh thnh 1 tn thc vt khi. V d. T bng 3.1 v 4.1 ta c: Lng CO2 rng hp thu: s liu ct 3 ca bng 4.3 = ct 2 x 1,854. Lng O2 c rng thi vo khng kh: ct 5 = ct 2*1,442. 3 Khi P = 760 mmHg, t = 150C th t trng ring (d, kg/m3) ca CO2 v O2 tng ng l 1,870 v 1,335; th tch v (m3/kg) ca 1 kg CO2 v O2 tng ng l 0,535 v 0,749. Do , ct 4 = ct 3/1,87 = ct 3*0,535; ct 6 = ct 5*0,749 = ct 5/1,335.Bng 4.2. Hm lng trung bnh ca cc nguyn t ha hc (%) theo trng lng kh tuyt i trong g, cnh nhnh, l... Thnh phn ha hc theo cc b phn ca cy 1. G thn cy khng v -C -H -O -N - Tro - T trng g kh tuyt i, t/m3 2. Cnh, r c v -C -H -O -N - Tro 3. L, hoa, qu -C -H -O -N - Tro 16 Loi Thng 49,60 6,40 43,60 0,15 0,30 0,53 51,50 6,20 41,00 0,36 0,94 53,10 6,2 36,30 1,32 3,10


3. Theo s liu ca bng 4.3, hy lp nhng th sau y: Lng tng trng thc vt khi kh tuyt i theo tui lm phn. Kh nng hp thu CO2 theo tui lm phn. Kh nng gii phng O2 theo tui lm phn. Cc ng cong trn y b tr trn cng mt th, trong : + tui rng t theo trc honh, 1 cm = 10 nm; + trc tung bn tri t lng tng trng thc vt khi kh tuyt i (m), CO2, O2 vi n v l t/ha/nm (1 cm = 1 tn); + trc tung bn phi t lng O2 c rng gii phng ra khng kh vi n v l m3/ha/nm (t l 1 cm =1 m3 = 1 tn). 4. Khi bit lng CO2 v O2 m 1 ha rng hp thu vo v thi ra khng kh, nh lm hc c th c tnh c kh nng hp thu CO 2 v gii phng O2 trong mt nm ca gn 4 t ha rng trn ton th gii v vai tr ca rng trn tri t ?

Bng 4.3a. S hp thu CO2 v gii phng O2 ca rng Thng tui khc nhau Tui rng(nm) (1) (tn/ha) (2)

m 4,4 6,0 ...

Hp thu CO2 T/ha m3/ha(3) (4)

Thi O2 T/ha m3/ha(5) (6)

20 30 40

8,16(*) 11,13 ...

4364 5952 ...

6,34 8,65 ...

4749 6479 ....

(*) Cc s t ct 3 - 6 l cc s c tnh lm v d mu

Bng 4.3b. S hp thu CO2 v gii phng O2 ca rng Si tui khc nhau Tui rng(nm) (1) (tn/ha) (2)

m

Hp thu CO2 (tn/ha) m3/ha(3) (4)

Thi O2 (tn/ha) m3/ha(5) (6)

20 30 40... Bi tp 6 1. Trnh by nh hng qua li ca rng v gi ? 2. Hy v li s m t nh hng ca ai rng n vn tc v hng vn ng ca gi khi gp ai rng ?

17


3. Theo s phn b tc gi trc v sau ai rng v theo cng thc ca E.N. Valendik (1964), hy tnh: + Tc gi sau ai rng 50 m, 100 m v 400 m; trong gi thit: V 0 (tc gi trc ai rng) = 8, 10, 12, 14, 16 m/s. + Tc gi (V, m/s) trn cc tm chiu cao h = 2, 4, 6, 8, 30 m ca tn rng, bit rng:V = [2,22(h/2) - 0,83(h/2)2 + 0,1(h/2)3] - 0,0029(h/2)4 - (0,076V0 + 0,063).

+ T kt qu tnh ton, hy v cc th m t phn b tc gi trong rng ty thuc vo chiu cao (H, m) ca tn rng so vi mt t. Khi v th ny, cn b tr tc gi trc honh vi t l 1 cm = 2 m/s, cn trc tung t chiu cao tn rng vi t l 1 cm = 2 m (hnh 4.1).

H, m

Hnh 4.1. Ch dn cch b tr th biu din phn b tc gi (V, m) theo chiu cao H (m) ca tn rng.

Tc y, V, m T kt qu tnh ton trn gi sinh vin hy tr li nhng cu hi sau y: (a) Ti sao tc gi trong ai rng li gim ? (b) Gi thit ai rng rng 100 m, chiu cao 25 m th nh lm hc phi b tr khong cch gia hai ai rng bng bao nhiu chng pht huy tt tc dng phng h cho ng rung ? Bit rng tc gi thnh hnh l 15 m/s.

* * *

18


Phn V RNG V TBi tp 7 Bng 5.1(a,b) cho bit qu trnh sinh trng ca cc lm phn theo tui. T hy xc nh : 1. Lng thc vt khi (thn c v, cnh nhnh, r c v, l, hoa qu) c rng tch ly, phn ri rng v o thi tng ng vi tui khc nhau ? 2. Nhu cu m v cc cht khong khc (tro) ca 1 ha rng trong tng thi k v c qa trnh sng ca rng ? 3. Lng m v cht khong b mang ra khi rng trong k khai thc chnh v cht nui dng rng. Gi thit cng khai thc l 96% tng lng thc vt khi cui chu k sng ca rng ? Gii thch v hng dn gii bi tp 7 1. tnh c nhu cu cht dinh dng ca rng, chng ta cn phi bit thnh phn ha hc trong cc b phn ca cy rng v tng quan cc nguyn t trong hp cht ca chng. Nhng s liu ny c ghi li bng 4.2 v 5.2. 2. Bng 5.3 cho bit hm lng cc cht dinh dng tnh bng n v kilgam. Do vy, khi tnh ton theo n v th tch (m3) th phi thc hin s chuyn i thch hp. 3. Mun chuyn t n v trng lng kh tuyt i sang n v th tch trng thi cy ng (trng thi g m t nhin), ta cn s dng t trng g m bng 5.4. Trong bng 5.4, ct 5 l tng quan trng lng l kh tuyt i v trng lng l m.19


4. Cc s liu v lng tng trng v lng o thi thc vt khi, nhu cu m v cc cht khong (cht tro), s tr li (quay vng) cht dinh dng v t c tnh ton v in vo biu 5.5. Trong biu 5.5, tr s tui rng ct 1 l tr s gia t: v d tui 10, 20...100 nm tng ng thuc nhm tui 6-15,1625, 96-105 nm. 5. Sau khi tnh ton xong biu 5.5, cc s liu c in vo mu biu 5.6. 6. Gi thit nhng qun th ny b khai thc trng v lng g c v mang ra khi rng l 96% so vi tr lng rng trc khi khai thc. Phn b li rng gm r 3%, phn cnh, ngn v l l 1% so vi tng thc vt khi ca rng. Bit t l gia trng lng cnh nhnh v r l 0,46/0,54.

Bng 5.1a. Tng trng hng nm (trung bnh 10 nm) ca rng Thng v thc vt khi kh tuyt i, lng ri rng v o thi, tn/haTui (nm) (1) N (cy/ha) (2) Thn cy c v M (3) m (4) Cnh v r c v M (5) m (6) l, hoa, qu M+m (7) Tng cng M (8) m (9)

10 20 30 40 50 60 70 80 90 100

8200 4020 2620 1990 1590 1180 1050 878 684 602

0,90 2,00 2,70 3,07 3,54 3,50 3,50 3,25 3,00 2,60

0,18 0,40 0,55 0,61 1,10 1,18 1,28 1,24 1,22 1,08

0,40 1,91 1,05 1,10 0,91 0,82 0,78 0,69 0,58 0,52

0,10 0,23 0,27 0,31 0,32 0,32 0,30 0,27 0,24 0,22

1,30 1,76 2,26 2,61 2,85 2,80 2,78 2,62 2,55 2,50

2,60 4,67 6,01 6,78 7,30 7,13 7,06 6,56 6,13 5,62

1,58 2,39 3,08 3,53 4,27 4,30 4,36 4,13 4,01 3,80

Bng 5.1b. Tng trng hng nm (trung bnh 10 nm) ca rng Si v thc vt khi kh tuyt i, lng ri rng v o thi, tn/haTui (nm) (1) N (cy/ha) (2) Thn c v M (3) m (4) Cnh v r c v M (5) m (6)L, hoa,qu

Tng cng M (8) m (9)

M+m (7)

10 20 30 40 50 60 70 80 90 100 110 120

8800 4800 2540 1690 1130 802 602 467 374 308 263 247

2,60 5,13 5,82 6,23 6,06 5,17 4,68 4,40 4,10 3,98 3,69 3,28

0,82 1,60 1,70 1,72 1,71 1,70 1,73 1,78 1,72 1,70 1,68 1,64

1,69 3,32 2,62 2,42 2,15 1,79 1,49 1,36 1,20 1,09 0,98 0,85

0,53 1,09 0,83 0,74 0,71 0,67 0,65 0,60 0,52 0,48 0,45 0,43

2,06 3,88 4,26 4,66 4,92 4,51 4,06 3,90 3,81 3,71 3,52 3,23

6,35 12,33 12,70 13,31 13,13 11,47 10,23 9,66 9,11 8,78 8,19 7,36

3,41 6,57 6,79 7,12 7,34 6,88 6,44 6,28 6,05 5,90 5,65 6,30

20


Bng 5.2. Tng quan trng lng gia cc nguyn t ha hc v hp cht ca chng Hp cht CaO K2 O K2CO3 Na2O P2 O5 MgO SiO2 Trng lng nguyn t 40 + 16 2*39 + 16 2*39 + 12 + 3*16 2*23 + 16 2*31 + 5*16 24 + 16 28 + 2*16 Trng lng phn t 56 94 138 62 142 40 60 T l nguyn t v hp cht 0,714 0,830 0,565 0,710 0,436 0,600 0,467

Bng 5.3 Hm lng tro v cc cht dinh dng trong cc b phn ca cy, kg/tn cht kh tuyt i Ch tiu (1) 1. G thn c v - Tro -P - Ca -K - Mg -N 2. Cnh, r c v - Tro -P - Ca -K - Mg -N Loi cy Thng Si (2) (3) 5.80 0,087 2,80 0,39 0,30 1,88 9,40 0,40 4,40 1,30 0,95 3,6 13,2 0,137 5,44 1.10 0.62 3,29 23,40 9,64 1,95 1,10 6,7 Ch tiu (1) 3. L hoa qu - Tro -P - Ca -K - Mg -N Loi cy Thng Si (2) (3) 31,0 1,50 4,70 4,80 1,40 13,2 60,0 9,6 9,2 4,5 26,7

Bng 5.4. T trng g m c v theo cc b phn ca cy, T/m3

Loi cy Thng Si

G thn cy 0,403 0,560

Cnh c v 0,410 0,540

R c v 0,380 0,530

L(T kh/T m) 0,410 0,430

7. Lp th v tng lng tng trng thc vt khi v tng trng thn cy trng thi kh tuyt i. T l v th nh sau : + Trc honh b tr tui rng, tng ng 1cm = 10 nm ; + Trc tung t thc vt khi vi t l 1cm = 50 - 100 t/ha; + Phi di trc tung (tr s m) bn phi biu th lng thc vt khi b o thi (vi t l 1cm = 50 - 100 t/ha) trong tng giai on sng ca rng, cn trc tung bn tri l s cy b o thi (vi t l l 1 cm = 1000 cy/ha).Bng 5.5. ng thi nhu cu v s quay vng cht khong ca rng Thng 21


Tui 1 6-15 16-25 26-35 36-45 46-55 ...

M (tn) 2 9,0 20,0 27,0 30,7 35,4

m (tn) 3 1,8 4,0 5,5 6,1 11,0

M-m (tn) 4 7,2 16,0 21,5 24,6 24,0

G thn cy c v Tng theo tui Nhu cu sau (tn) 10 nm (kg) M m M-m m tro 5 6 7 8 9 9,0 1,8 7,2 16,92 52,2 29,0 5,8 23,2 56,0 11,3 44,7 86,7 17,4 69,3 122,1 28,4 93,7

Cnh, r

Quay vng sau 10 nm (kg) m tro 10 11 3,38 10,44

Lng hin cn sau 10 nm, (kg) m tro 12 13 13,54 41,76

(tnh cy 14

nh thn)

(Tip bng 5.5)M+m (tn) 15 L Nhu cu sau 10 nm, (kg) m tro 16 17 M (tn) 18 m (tn) 19 M-m (tn) 20 Tng tng trng v nhu cu khong, kg/ha Tng theo tui Nhu cu Quay vng (tn) (kg) (kg) M m M-m m tro m tro 21 22 23 24 25 26 27 Hin cn (tn) m tro 28 29

Ghi ch : + M - lng tng trng ( thn, l , thc vt khi...); + m - Lng o thi cc b phn ca cy + M - m l lng hin cn trn cy ng.

Bng 5.6. S lng cc cht dinh dng khong c cy hp thu v tr v t hng nm, kg/ha Loi cy :Tui (nm)(1)

Nng sut (tn/ha)(2)

Thnh phn dinh dng khong N(3)

P(4)

Ca(5)

K(6)

Tng s(7)

10 20....

....

....

....

....

....

....

Nh vy, trn th ny gm c 7 ng cong sau y: 1. Phn b s cy theo tui lm phn (c k hiu N - A nm); 2. Tng lng tng trng thc vt khi theo tui rng; 3. Tng lng thc vt khi hin cn (phn sinh khi cy ng hay cy cn ang sng - standing trees) theo tui rng; 4. Tng lng thc vt khi b o thi theo tui rng; 5. Tng lng tng trng thc vt khi ca phn thn cy theo tui rng; 6. Tng lng tng trng thc vt khi ca phn thn cy hin cn (sinh khi cy ng hay cy cn sng) theo cc cp tui ca rng; 7. Tng lng thc vt khi ca phn thn cy b o thi theo tui rng; Khi v th cn lu , trc tung b tr tr lng g thn cy theo n v m3/ha, hoc i thnh t/ha. C hai loi n v ny ly t l ging nhau. Cc tr s v lng o thi g cng c b tr tng ng nh trn. 8. V cc th v nhu cu khong ca rng thay i theo tui (n v l kg/ha), gm ba th sau y: Nhu cu m v tro to ra tng lng thc vt khi; Tr lng m v tro cn li trn cy ng;

22


Tr lng m v tro trn thn cy ng n tui khai thc chnh v tng ng l m v tro c a ra khi rng trong qu trnh khai thc ( y gi thit lng khai thc bng 96% tr lng g thn cy). Cc th c v theo t l nh sau: (a) Trc honh b tr tui rng, tng ng 1 cm = 10 nm; (b) Trc tung b tr lng m v tro cn li trn cy ng v s c mang ra khi rng cng vi vic khai thc g; (c) Trc tung biu th nhu cu m v tro hnh thnh tng lng thc vt khi - t l v t chn.

Phn VI SINH TRNG V PHT TRIN CA RNGBi tp 8 1. Bng 6.1 ghi li mt s nhn t iu tra ca lm phn Thng 140 tui, trong : MC (m3/ha) l tng tr lng g thn cy; Mhc (m3/ha) l tr lng g cy ng hay cy hin cn sng; m (m3/ha) l tr lng g b o thi trong ton b i sng ca rng Thng 140 tui. Theo bng 6.1, hy xc nh v v hai ng cong sau y: (a) Lng tng trng v tr lng bnh qun chung nh k 10 nm ZMbqc(TX) ca qun th, bit rng ZMbqc(TX) = (6.1) trong : MC = MCA - MCA - n ; A = n = 10 nm.Bng 6.1. Mt s nhn t iu tra lm phn Thng 140 tuiTui (nm) 1 10 20 30 40 50 60 70 80 90 100 100 120 130 140 N ( cy/ha) 2 8200 4020 2620 1990 1590 1200 1000 880 690 600 590 580 565 555 H (m) 3 6 8 10 13 15 18 20 22 23 24 26 28 29 30 D1.3 (cm) 4 6 8 11 14 16 19 21 24 26 28 29 31 32 33 Mc (m3/ha) 5 20 75 155 235 325 415 520 590 655 695 730 765 800 835 Mhc (m3/ha) 6 16 65 125 180 265 345 425 465 495 500 520 550 580 600 m (m3/ha) 7 4 10 30 55 60 70 95 125 160 195 210 215 220 235

T l v quy nh: 2 m3/nm ca ZMbqc(TX) tng ng vi tr lng qun th M = 100 m3/ha, sau ni cc im thnh ng cong lin nt.23


(b) Lng tng trng bnh qun v tr lng g thn cy tui A nm c tnh theo cng thc : + i vi tng tr lng qun th : MCbq = , m3/ha (6.2) + i vi tng tr lng cy ng hin cn: Mhcbq = , m3/ha (6.3) Sau v cc ng cong ZMbqc(TX), Mcbq v Mhcbq. Hai ng cong ZMbqc(TX) v Mcbq ct nhau ti im K ng vi tui no, tui ny c ngha g v mt lm sinh - kinh t ? Nhng s liu tnh ton trn y c in vo mu biu 6.2.Bng 6.2. Kt qu tnh ton cc nhn t iu tra ca lm phn Thng 140 tuiTui (nm) 1 10 20 30 40 50 60 70 80 90 100 100 120 130 140N ( cy/ha)

2 8200 4020 2620 1990 1590 1200 1000 880 690 600 590 580 565 555

H (m) 3 6 8 10 13 15 18 20 22 23 24 26 28 29 30

D1.3 (cm) 4 6 8 11 14 16 19 21 24 26 28 29 31 32 33

Mc (m3/ha) 5 20 75 155 235 325 415 520 590 655 695 730 765 800 835

Mhc (m3/ha) 6 16 65 125 180 265 345 425 465 495 500 520 550 580 600

m (m3/ha) 7 4 10 30 55 60 70 95 125 160 195 210 215 220 235

ZMcbq ( TX)8

MCbq9

Mhcbq

10

Phn b s cy hin cn theo tui (k hiu Nhc - A, xem ct 1 v 2);

2. Hy v biu m t nhng phn b sau y:

Phn b s cy b o thi ( y biu th s cy b o thi theo gi tr m) theo tui (k hiu n - A, xem ct 1 v 2); Phn b N - D v N - H theo tui lm phn, xem tng ng ct 1, 3, 4; Phn b MC - A, Mhc - A, xem tng ng ct 1, 5 v 6; Phn b tr lng lm phn b o thi (k hiu m - A, vi m ly gi tr m, m = MC - Mhc, xem ct 1 v 7). 3. Hy tr li mt s cu hi sau y: 1. Cc giai on trong i sng ca rng v ngha ca chng ? 2. C s xc nh tui thnh thc s lng ? 3. Cho bit quy lut sinh trng D, H v M ca cy rng, ngha ca vic tm hiu cc quy lut ny ? 4. Lng tng trng tr lng ca lm phn tng nhanh hoc gim thp vo giai on no, v sao; vic tm hiu quy lut ny c ngha g ? 5. Cho bit quy lut gim s cy theo tui lm phn, nhng nhn t nh hng, ngha ca vic tm hiu quy lut ny ? 6. Nhng nhn t nh hng n nng sut rng ?

24


Phn VII CU TRC RNGBi tp 9 1. Theo s liu ca bng 7.1, hy tnh cc c trng thng k v lp bng m t phn b s tn cy (N - H) trong khng gian ca rng t nhin v rng trng thun loi ng tui ?Bng 7.1. Phn b N - H ca rng t nhin v rng thun loi ng tui

X(1)

Rng t nhin H, m S tn (f)(2) (3)

X(4)

Rng trng B H, m S tn (f)(5) (6)

0 1 2 3 4

11,5 18,5 25,5 32,5 39,5 Tng s

34 49 23 9 4 119

0 1 2 3 4

16 18 20 22 24 Tng s

3 8 17 29 11 69

Ghi ch : Ct 2 v 5 l trung tm cp chiu cao ; Ct 1 v 4 (X) l th t lp chiu cao ca rng.

Bng 7.2. Din tch tn cy (St,m2) trong cc lp khng gian (Din tch th nghim l 0.25 ha)H, m(1)

Dt, m(2)

S tn (f, cy)(3)

St, m2(4)

11,5 18,5 25,5 32,5 39,5 Tng cng

6,4 7,9 9,4 12,4 15,4

25 39 40 10 5 119

2. Tnh tng din tch v phn trm cc tn cy trong cc lp khng gian ca rng t nhin v rng nhn to theo s liu ca bng 7.2. Cc k hiu ca bng 7.2 nh sau: + Dt (m) - ng knh bnh qun ca tn cy v tr rng nht; + St (m2) - tng din tch hnh chiu nm ngang ca cc tn cy. 3. Bng 7.3a ghi li phn b N - D ca qun x cy g v nhm loi cy u th trong mt khonh rng t nhin. Bng 7.3b ghi li phn b N - D ca qun th Tch ng tui. T hy v th m t phn b N - D ca cc lm phn trn ?Bng 7.3a. Phn b N - D ca rng t nhin

25

Thc hnh sinh thi rng S cy theo cp knh : Phn theo loi cy: Tu Lim(4) (5)

TT(1)

D1.3 (cm)(2)

Tng th(3)

D(6)

1 2 3 4 5 6 7 8 Cng

14 22 30 38 46 54 62 70

362 142 74 47 30 20 11 6 692

125 36 22 14 9 8 4 3 221

122 45 17 10 11 7 5 3 220

115 61 35 23 10 5 2 251

Bng 7.3b. Phn b N - D ca rng Tch 25 tuiTT (1) 1 2 3 4 5 6 7 8 Cng D1.3, cm (2) 12 16 20 24 28 32 36 40 N, cy (3) 10 15 24 42 64 32 22 7 216

Hng dn gii bi tp 9 1. Nhng c trng phn b N - D v N - H cn phi tnh l : (a) Chiu cao bnh qun (Hbq, m) v ng knh bnh qun (D 1.3bq, cm) ca lm phn trn tiu chun ? (b) Sai tiu chun (S), h s bin ng (V%), bin phn b (Xmax - Xmin) ca chiu cao v ng knh ? (c) Tr s trung v (Me): + Nu N l s l th gi tr Me l tr s trung bnh ca s ng hng th (N + 1)/2; + Nu N l s chn th Me l tr s trung bnh ca s ng hng th (N/2) v (N + 1 )/2; + Khi s liu c phn nhm th Me c tnh bng cch lp bng phn phi dn v th dn; v - Nu N l th Me c tnh nh sau: Me = Li + k (7.1) - Nu N l chn th Me c tnh nh sau: Me = , (7.2) vi : Xn/2 = Li + k X (n/2)+1 = Li + k Trong cng thc 7.1 v 7.2 ta c:26


+ Li l ranh gii di ca nhm cha Me; + k - khong cch nhm ; N - tng s ln quan st; + ndn - tn s dn di Li ; ni - tn s ca nhm cha trung v Me. (d) lch (Sk). Tr s ny cho bit mt i xng ca phn b, ngha l biu th cc gi tr dn v phi trn hoc pha di ca gi tr trung bnh. Sk c th c tnh theo cc cng thc sau y : - Dng h s xin ca Pearson (2) Sk = (7.3) - Hoc Sk = (7. 4) Nu Sk ly gi tr m th phn phi lch tri, ngha l c nhiu gi tr dn v phi di tr Xbq. Ngc li, Sk mang du dng th phn phi lch phi, ngha l c nhiu gi tr dn v phi trn tr Xbq. (e) nhn (Ex). Tr s ny c lin quan vi phn b chun, trong Ex = - 3 (7. 6) i vi phn b chun Ex c tr s bng 3. Do , nu Ex ly gi tr m th nh ng cong phn b l t. Ngc li, nu Ex ly gi tr dng th nh ng cong phn b l nhn. 2. Khi tnh din tch hnh chiu tn cy trn mt phng ngang, hy coi n c dng hnh trn, ngha l St (m2) = *Dt2 = 0.785* Dt2. Theo kt qu tnh ton v th, hy lm r nhng vn sau y: (1) c im phn b tn cy trong khng gian (ca rng t nhin v rng trng thun loi). S cy tp trung nhiu nhng cp H no, iu ni ln vn g ? (2) Quy lut phn b N - D ca rng t nhin v rng trng thun loi ng tui. Nguyn nhn hnh thnh cc dng phn b ny ? (3) Nhng u im v nhc im ca rng t nhin v nhn to v mt lm sinh (sinh thi) v kinh t ? * * *

Phn VIII. DIN TH RNGBi tp 10 1. Phn bit s dao ng v din th ca qun x thc vt. Cho v d ? 2. V sao din th th sinh tin trin nhanh hn din th nguyn sinh ? 3. ngha nghin cu s dao ng v din th rng ?

27


Phn IX TI SINH RNGBi tp 11 1. Bng 9.1 l ti liu ghi chp v tnh hnh ti sinh di tn rng trn cc tiu chun (hay o m, dng bn). Tng s dng bn c o m l 39. Kch thc 1 o m l 10 m2. Cc o m c b tr theo phng php h thng trn nhng tuyn cch u, tuyn ny cch tuyn kia l 50 m, ny cch kia l 20 m. Cy ti sinh ca cc loi cy g c phn bit theo 3 cp H (m); trong cp I c H 0,50 - k hiu H1, cp II c H = 0,51 1,50 - k hiu l H 2 v cp III c H = 1,51 6,0 - k hiu H3. Cy ti sinh ca cc loi cy g cng c phn bit theo 3 cp cht lng l tt, nghi ng (cy cha r tt hay xu) v xu. T hy tnh cc c trng sau y: (a) S cy bnh qun trn dng bn (k hiu l N bq/db), cc ch tiu bin ng nh sai tiu chun, h s bin ng, sai s ca s bnh qun...? Nhng ch tiu ny c tnh cho: + tng s cy ti sinh c kch thc v cht lng khc nhau ; + tng s cy tin tng, nghi ng v xu; + cy tin tng, nghi ng v xu tng ng vi tng cp chiu cao v cp cht lng khc nhau; (b) Tnh thng gp s cy tin tng v a ra nhn xt kt qu ? (c) Gi thit yu cu v chnh xc trong thng k cy ti sinh l 5%, hy cho bit kt qu o m trn y c m bo yu cu ra hay khng ?28


(d) Nu ch thng k 10, 20, 25 dng bn th kt qu o m tng ng c chnh xc bng bao nhiu ? Hng dn tnh ton Bc 1. S cy bnh qun trn dng bn (Nbq/db) c tnh theo cng thc Nbq = (9.1) trong Ni (i = 1, 2...n) - s cy trong th i; n l tng s o m. Bc 2. Tnh s cy trn 1 ha:

Bng 9.1. S liu o m ti sinh rng (Din tch 10m2/db)TT db 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 H1 2 0 1 4 0 1 0 2 4 0 0 1 3 4 2 1 0 0 2 0 1 3 0 0 0 2 5 0 Cy tin cy H2 3 2 3 0 1 5 0 2 3 1 0 4 0 0 0 2 1 1 2 2 4 1 0 3 4 0 1 3 H3 4 0 2 4 0 2 4 0 0 1 2 4 0 0 1 4 2 1 0 0 2 0 1 3 0 0 0 2 Tng 5 2 6 8 1 8 4 4 7 2 2 9 3 4 3 7 3 2 4 2 7 4 1 6 4 2 6 5 H1 6 0 1 4 0 1 0 1 4 0 1 0 2 4 0 0 1 3 4 2 1 0 0 2 0 1 3 0 Cy nghi ng H2 7 2 3 0 1 5 2 3 0 1 5 0 2 3 1 0 4 0 0 0 2 1 1 2 2 4 1 0 H3 8 0 2 4 0 2 0 2 4 0 2 4 0 0 1 2 4 0 0 1 4 2 1 0 0 2 0 1 Tng 9 2 6 8 1 8 2 6 8 1 8 4 4 7 2 2 9 3 4 3 7 3 2 4 2 7 4 1 H1 10 2 1 0 0 2 0 1 3 0 0 0 2 5 0 1 3 4 2 1 4 2 1 0 0 2 0 1 Cy xu H2 11 0 2 1 1 2 2 4 1 0 3 4 0 1 3 2 1 0 1 1 0 0 2 1 1 2 2 4 H3 12 1 4 2 1 0 0 2 0 1 3 0 0 0 2 5 0 1 4 2 0 1 4 2 1 0 0 2 13 3 7 3 2 4 2 7 4 1 6 4 2 6 5 8 4 5 7 4 4 3 7 3 2 4 2 7 Tng s Tng Sng 14 7 19 19 4 20 8 17 19 4 16 17 9 17 10 17 16 10 15 9 18 10 10 13 8 13 12 13 Cht 15 1 2 0 0 1 2 1 0 0 2 0 1 0 2 0 0 0 1 2 0 0 0 1 1 2 3 0

29

Thc hnh sinh thi rng28 29 30 31 32 33 34 35 36 37 38 39 Tng 1 3 4 2 1 0 1 0 2 2 3 0 55 2 1 0 1 1 0 2 1 2 1 0 2 58 5 0 1 4 2 1 0 0 2 0 1 3 54 8 4 5 7 4 1 3 1 6 3 4 5 167 0 0 2 0 1 0 2 4 0 0 1 3 48 3 4 0 3 5 0 2 3 1 0 4 0 70 3 0 0 0 2 4 0 0 1 2 4 0 54 6 4 2 3 8 4 4 7 2 2 9 3 172 3 0 4 2 1 0 0 2 0 1 3 0 53 1 0 0 0 2 1 1 2 2 4 1 0 55 0 1 0 1 4 2 1 0 0 2 0 1 50 4 1 4 3 7 3 2 4 2 7 4 1 158 18 9 11 13 19 8 9 12 10 12 17 9 497 1 2 0 1 0 0 2 2 1 1 0 1 33

N/ha = Nbq , vi s l din tch 1 dng bn, n v l m2/. Bc 3. Tnh cc c trng bin ng : + sai tiu chun

(9.2)

S= (9.3) + bin ng s cy gia cc dng bn V% = (9.4) + sai s chun ca s bnh qun m= (9.5) Bc 4. chnh xc ca kt qu o m ti sinh c tnh theo cng thc P% = = (9.6) Bc 5. T cng thc 9.6 c th tm c s dng bn cn o m m bo chnh xc P% cho trc l n= (9.7) Bc 6. thng gp cy ti sinh c tnh theo cng thc F= (9.8) trong n1 l s o m bt gp cy ti sinh, n - tng s o m. 2. Bng 9.2 ghi li s liu v lng tng trng chiu cao hng nm (ZH, cm) ca cy ti sinh Du song nng di tn rng c tn che khc nhau. T hy xc nh tn che thch hp cho sinh trng ca cy ti sinh Du song nng theo cc giai on tui khc nhau ? Hng dn tnh ton Trc ht, chng ta cn nhn thy rng, theo Quy lut gii hn sinh thi th tn che thch hp cho cc giai on sng ca cy ti sinh c hiu l bin (hay gii hn) tn che m bo cho chng sinh trng v pht trin bnh thng. tm c gii hn ny, chng ta c th thc hin cc bc tnh ton sau y:

30


Bng 9.2. Lng tng trng chiu cao hng nm (ZH, cm) ca cy ti sinh Du song nng di tn rng c tn che khc nhau tn che v l trng (LT, m2) (1) LT1 LT2 0,5-0,6 0,7-0,8 0,9-1,0 ZH(cm) tng ng theo tui : 2 (2) 25,6 26,8 24,7 24,5 12,5 4,2 3,6 3,8 3,5 4,1 4 (3) 54,5 6,5 56,7 6,1 53,8 6,7 40,5 5,3 36,5 4,7 6 (4) 132,4 14,1 136,5 17,3 130,0 16,8 94,5 18,5 76,5 16,2

Ghi ch : - LT1, LT2 - tng ng l l trng kch thc < 200 v 200 400 m2; - Tr s trong bng 9.2 l s bnh qun v sai tiu chun ca ZH ; - Tng s mu nghin cu l 150 cy, trong s cy o m mi tui ng vi mt cp tn che l 30 cy.

Bc mt. Ap dng tiu chun T ca Student kim tra s sai khc gia cc Xi vi Xbqc, y X = ZH: Ti = (9.9) trong : - Xbqc = ; - S2c = ; - n=; - m l s mu em so snh. Bc hai. So snh cc Ti vi T05(n-2) hoc T01(n-2). Nu cc Xibq no c sai d r rt vi Xbqc (ngha l Ti > t05(n-2) hoc T01(n-2)), ta gp chng thnh nhm ring, nhm cn li l nhng Xibq khng c sai d r rt vi Xbqc (ngha l Ti < T05 hoc T01). Sau t nhng mu c Xibq sai d r rt vi Xbqc c gp li thnh nhm, v t ta li tip tc p dng cng thc 9.9 tnh Xc, Sc cho nhm . Sau hy lp li cc bc kim tra s thun nht gia ac nhm bng tiu chun T... Bc ba. Sau khi xc nh c cc nhm thun nht, cn ch ra tn che ca chng. tn che thch hp cho mt giai on cy ti sinh no chnh l khong tn che m ti cy ti sinh c mc tng trng bnh qun t t (ZHbq - t05* Sc) tr ln. 3. Bng 9.3 ghi li phn b ca mt loi cy ti sinh trn 200 dng bn, mi dng bn l 1m2. T hy xc nh kiu phn b ca n ?Bng 9.3. Phn b cy trn mt t

S cy/ dng bnTn s thc nghim

Tn s l thuyt 2tt

0 79 .... ....

1 70

2 31

3 16

4 4

31


Hng dn tnh ton Bc 1. T ti liu cu bng 9.3, hy tnh cc tham s mbq/db, S2... Bc 2. Ap dng phn b Poisson, tnh xc sut bt gp s lng cy ti sinh trn mi dng bn. Phn b Poisson c dng: P(x) = , (9.10) trong e = 2,71828 ; m - s cy bnh qun/db; k - s cy/. T cng thc 9.10 ta c: P(x=0) = e- m ; P(x = 1) = e- mm; P(x=2) = e- mm2/2; P(x=3) = e- mm3/6; P(x=4)= e- mm4/24; P(x=5)= e- mm5/120.... Bc ba. Kim tra phn b thc nghim c ph hp vi phn b l thuyt hay khng. Mun vy ta phi tnh: tn s l lun cho cc gp 0, 1, 2...n cy ; sau kim tra s ph hp ca dng phn b Poisson theo tiu chun 2 vi s bc t do bng s cp sau khi gp (iu kin l tn s ca mi cp phi ln hn 5) tr i 2. Bc bn. Tra bng 205 hoc 201 vi s bc t do l n - 2, y n l s t sau khi gp c tn s mi t ln hn hoc bng 5. Nu 2TN < 2LT th phn b ca loi cy ny tun theo lut phn b Poisson. Ni khc i, phn b ca n theo din tch l phn b ngu nhin. Ngc li, nu 2TN > 2LT th phn b ca loi cy ny khng tun theo lut phn b Poisson hay khng phi phn b ngu nhin. Ch : Phn b Poisson c mt tnh cht quan trng l ga tr bnh qun (mbq) bng tr s phng sai (S2). Do , xc nh s b phn b cy trn mt t ta c th tnh : W= (9.11) Nu W < 1,0 th phn b cy ti sinh trn mt t l ng u; Nu W = 1,0 th phn b cy ti sinh trn mt t l ngu nhin; Nu W > 1,0 th phn b cy ti sinh trn mt t c dng cm. Cn nhn thy rng tr s W t n cha ni ln iu g. Theo Blackman (1942), kim tra iu kin S2/mbq c thc s khc 1 hay khng c th dng tiu chun sau : S= , (9.12) vi N l s mu. Khi N rt ln (trn 200 ) th cng thc (9.12) c th chuyn thnh : S = Theo Blackman, nu W = nm trong khong 1 2S th n khng khc 1 thc s, ngha l phn b thc nghim ph hp vi phn b Poisson.

* * *

32


CU HI N TP1. Cho bit khi nim v sinh thi hc v nhim v ca n; sinh thi rng v nhim v ca n ? 2. Cho bit khi nim v rng v cc thnh phn ca rng ? 3. Th no l nhn t sinh thi, nhn t sinh tn, nhn t sinh thi ch o, nhn t sinh thi c lp, nhn t sinh thi ph thuc ? 4. Pht biu nhng quy lut tc ng ca cc nhn t sinh thi n i sng sinh vt rng? 5. xem xt phn ng ca cy g trc tc ng ca nh sng, nhit , nc, phn bn (hu c, v c), trc ht nh lm hc cn phi thay i dn cc mc tc ng ca cc nhn t sinh thi k trn. Sau , cn c vo phn ng ca cy g, ngi ta xc nh mc tc ng thch hp ca nhn t sinh thi. Cch b tr th nghim nh trn da trn nguyn l no? 6. Trnh by nh hng ca nh sng i vi rng ? Cc phng php xc nh quan h ca cc loi cy vi nh sng ? 7. xc nh phn ng ca cy g vi nh sng trong iu kin (vn m, di tn rng), nh lm hc cn phi o c nhng ch tiu no; v sao ? 8. Cho bit nhng bin php lm sinh m cc nh lm hc s dng p ng nhu cu nh sng ca cc loi cy g (trong gieo m, di tn rng)?

33


9. Cho bit quan h ca rng v nc ? Vit phng trnh cn bng nc rng v phn tch cc nhn t nh hng n cn bng nc rng ? 10. Trong iu kin (vn m, rng trng, rng t nhin), nh lm hc c th gii quyt nhu cu nc cho cy rng bng cch no ? 11. Trnh by phng trnh cn bng nhit rng ? Ti sao rng c kh nng lm gim s nng cao nhit ca khng kh gn mt t ? 12. Cho bit nh hng qua li ca gi v rng ? 13. V sao thc vt phn b khc nhau theo cao ? 14. Trnh by quan h ca rng v ng vt ? 15. Cho bit chu trnh chuyn ha nng lng trong h sinh thi rng ? Vai tr ca thc vt trong chu trnh chuyn ha nng lng ca h sinh thi rng ? 16. Trnh by chu trnh chuyn ha vt cht trong h sinh thi rng? Nhng con ng hon tr li vt cht cho h sinh thi rng? 17. Khi nghin cu cu trc ca thm thc vt rng, nh lm hc cn phi xem xt nhng nhn t no ? V sao ? 18. Cho bit nhng c trng c bn ca qun th thc vt rng, qun x thc vt rng? 19. Cho bit th no l dao ng ca qun x thc vt, nguyn nhn dn n s dao ng ca qun x thc vt ? 20. Phn bit s dao ng v din th ca qun x thc vt, cho mt hai v d ? 21. Trnh by din th ca qun x thc vt rng, cc loi din th, nguyn nhn din th v ngha nghin cu din th rng ? 22. Ti sinh rng l g ? Cc hnh thc ti sinh rng ? Nhn t nh hng n ti sinh rng? Ti sao khi nghin cu ti sinh rng nh lm hc cn phi phn chia qu trnh ti sinh ca cy rng thnh nhiu giai on ? 23. Ti sinh chi l g? cc loi ti sinh chi, c im ca rng chi? Khi ti sinh rng bng con ng chi, nh lm hc phi lu n nhng vn g, ti sao ? 24. Th no l rng th sinh ngho, nguyn nhn hnh thnh; nhng c im ca rng th sinh ngho v phng hng x l rng th sinh ngho ? 25. Trnh by nhng u im v nhc im ca rng thun loi ng tui, rng hn giao khc tui. Cho bit nhng h thng bin php nng cao nng sut rng ? 26. Ti sao ni nh sng, nhit , gi, ma, t v a hnh c ngha quyt nh vic chn la cc phng thc lm sinh (khai thc - ti sinh rng (t nhin v nhn to), nui dng rng ? 27. Khi trng rng cy g ln (Sao en, Du ri, Vn vn, Ch chai, G , Ging hng) trn t (trng, b xi mn mnh, ngho dinh dng), trong nhng nm u nh lm hc thng trng hn giao chng vi cc loi cy (Keo l trm, Keo lai, u chm, Lim st, Mung en). Hy cho bit cch b tr cy trng nh trn nhm gii quyt nhng vn g? 28. Khi khai thc rng trn t dc (sn i v ni), nh lm hc ra cc nguyn tc sau y: (1) Khng c khai thc trng rng trn cc sn dc c tng t mng, thnh phn c gii nh (nhiu ct); (2) Khng c khai thc trng rng theo hng t chn ni ln nh ni m phi theo hng ngc li; (3) Khng c khai thc trng rng trn nh niNhng nguyn tc a ra trn y da trn nhng cn c no? 29. Ti sao trong trng rng, trc khi a cy t vn m ra t trng, nh lm hc phi thc hin mt s bin php nh o bu, ti nc gim dn v ngng ti nc t nht 1 - 2 tun, khng bn thm phn cho cy, hn dn tn che cho n khi m trng hon ton (nu cy cn che bng trong khi gieo m)? 30. Nh lm hc cn phi lm g khi gp nhng tnh hung sau y: 34


(a) i tng t trng rng l t trng, nhng cy g non rt cn bng che trong mt s nm u.(b) Cn phi trng rng t cy g ln c i sng rt di (thi gian c khai thc bng c i ngi), nhng iu kin kinh t - x hi c nhiu kh khn (kinh ph trng rng thp, i sng cn b v cng nhn lm nghip gp nhiu kh khn). (c) Cn phi chuyn ho mt lm phn cu thnh t nhiu cy a sng sang lm phn u th cy chu bng vi i sng di. (d) Th trng ang c nhu cu g cao v a dng, nhng nh lm hc ch c php khai thc trng rng trn din tch hp. (e) Cn phi duy tr nhng loi cy c gi tr kinh t cao, nhng i sng ca chng ang b e do do mi trng sng thay i hoc do nhng loi cy khc ang ln t khng gian ca chng. (f) Cn phi trng rng t nhng loi cy g bn a, nhng cho n lc y nh lm hc vn cha bit nhng thng tin g (sinh hc - sinh thi, k thut gieo m v gy trng, k thut nui dng rng, cng dng g, kh nng tiu th sn phm) v chng. (g) Cn phi trng rng t nhng loi cy g mc nhanh v trung bnh, nhng cho n lc y nh lm hc vn cha bit nhng thng tin g chng. (h) Nhng loi cy bn a p ng khng y nhu cu v kinh t - x hi v nguyn liu. (i) i tng t v rng nm trong quy hoch pht trin rng g ln, nhng lp a v loi cy to rng li khng c kh nng phc hi rng g ln. (j) Nh lm hc cha c nhng thng tin g v iu kin t nhin, kinh t - x hi v ti nguyn rng ca a phng n cng tc.

TI LIU THAM KHO CHNH************ ************

1. X.V. Belov, 1983. 2. X.V. Belov, 1983. 3. A.I. Buzkin,1985. 4. Stephen D. Wratten Gary L.A. Fry, 1986. 5. Thi Vn Trng, 1978. 6. Nguyn Vn Trng, 1984. 7. Nguyn Hi Tut, 1982. 8. Nguyn Vn Thm, 1996 9. V.I. Vasilevich, 1969.

- Bi tp lm hc, Nxb. Cng nghip rng, Moxcova (ting Nga). - Lm hc, Nxb. Cng nghip rng, Moxcova (ting Nga). - Phn tch cu trc qun x cy g, Nxb. Khoa hc, Moxcova (ting Nga). - Thc nghim sinh thi hc. Mai nh Yn dch, Nxb. Khoa hc v k thut, H Ni. - Thm thc vt rng Vit Nam trn quan in h sinh thi, Nxb. Khoa hc v k thut, H Ni. - Quy lut cu trc rng g hn loi, Nxb. Khoa hc v k thut, H Ni. - Thng k ton hc trong lm nghip, Nxb. Nng nghip, H Ni. - Sinh thi rng. T sch i Hc Nng Lm. - Nhng phng php thng k trong a thc vt, Nxb. Khoa hc, Leningrad.

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