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TNT equivalent
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Diagram of explosive yield vs mushroom cloud height, illustrating the difference between 22 kiloton Fat Man and 15 megaton Castle Bravo explosions[citation needed]
TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The "ton of TNT" is a unit of energy defined by that convention to be 4.184 gigajoules,[1] which is the approximate energy released in the detonation of a metric ton (1,000 kilograms or one megagram) of TNT. In other words, for each gram of TNT exploded, 4,184 joules of energy are released.
This convention intends to compare the destructiveness of an event with that of conventional explosive materials, of which TNT is a typical example, although other conventional explosives such as dynamite contain more energy.
Contents
[hide]
1 Kiloton and megaton
2 Historical derivation of the value
3 Conversion to other units
4 Examples
5 Relative effectiveness factor
5.1 RE factor examples
5.2 Nuclear examples
6 See also
7 References
Kiloton and megaton[edit]
The "kiloton (of TNT)" is a unit of energy equal to 4.184 terajoules.
The "megaton (of TNT)" is a unit of energy equal to 4.184 petajoules.
The kiloton and megaton of TNT have traditionally been used to describe the energy output, and hence the destructive power, of a nuclear weapon. The TNT equivalent appears in various nuclear weapon control treaties, and has been used to characterize the energy released in such other highly destructive events as an asteroid impact.[2]
Historical derivation of the value[edit]
A gram of TNT releases 2673–6702 J (joules) upon explosion.[3] The energy liberated by one gram of TNT was arbitrarily defined as a matter of convention to be 4184 J,[4] which is exactly one kilocalorie.
An explosive's energy is normally expressed as the thermodynamic work produced by its detonation, which for TNT has been accurately measured as 4686 J/g from a large sample of air blast experiments, and theoretically calculated to be 4853 J/g.[5]
The measured, pure heat output of a gram of TNT is only 2724 J,[6][clarification needed] but this is not the important value for explosive blast effect calculations.
Alternative TNT equivalency can be calculated as a function of when in the detonation the value is measured and which property is being compared.[7][8][9][10]
A kiloton of TNT can be visualized as a cube of TNT 8.46 metres (27.8 ft) on a side.
Grams TNT
Symbol
Tons TNT
Symbol
Energy [Joules]
Energy [Wh]
Corresponding mass loss
gram of TNT g microton of TNT μt 4.184×103 J or 4.184 kilojoules 1.163 Wh 46.55 pg
kilogram of TNT kg milliton of TNT mt 4.184×106 J or 4.184 megajoules 1.163 kWh 46.55 ng
megagram of TNT Mg ton of TNT t 4.184×109 J or 4.184 gigajoules 1.163 MWh 46.55 μg
gigagram of TNT Gg kiloton of TNT kt 4.184×1012 J or 4.184 terajoules 1.163 GWh 46.55 mg
teragram of TNT Tg megaton of TNT Mt 4.184×1015 J or 4.184 petajoules 1.163 TWh 46.55 g
petagram of TNT Pg gigaton of TNT Gt 4.184×1018 J or 4.184 exajoules 1.163 PWh 46.55 kg
Conversion to other units[edit]
1 ton TNT equivalent is approximately:
1.0×109 calories
4.184×109 joules
3.96831×106 British thermal units
3.08802×109 foot pounds
1.162×103 kilowatt hours
Examples[edit]
Further information: Orders of magnitude (energy)
Megatons of TNT
Energy [Wh]
Description
6988100000000000000♠1×10−12 (i.e. 1 gram of TNT) 1.162 Wh ≈ 1 food Calorie (large calorie), which is the approximate amount of energy needed to raise the temperature of one kilogram of water by one degree Celsius at a pressure of one atmosphere.
6991100000000000000♠1×10−9 (i.e. 1 kilogram of TNT) 1.162 kWh Under controlled conditions one kilogram of TNT can destroy (or even obliterate) a small vehicle.
6992100000000000000♠1×10−8 11.62 kWh The approximate radiant heat energy released during 3-phase, 600 V, 100 kA arcing fault in a 0.5 m × 0.5 m × 0.5 m (20 in × 20 in × 20 in) compartment within a 1-second period.[11][further explanation needed]
6992120000000000000♠1.2×10−8 13.94 kWh Amount of TNT used (12 kg) in Coptic church explosion in Cairo, Egypt on December 11, 2016 that left 25 dead[12]
6994100000000000000♠1×10−6 (i.e. 1 ton of TNT) – 6995440000000000000♠44×10−6 1.16–51.14 MWh Conventional bombs yield from less than one ton to FOAB's forty four tons. The yield of a Tomahawk cruise missile is equivalent to 500 kg of TNT, or approximately 0.5 tons.[13]
6994189999999999999♠1.9×10−6 2.90 MWh The television show MythBusters used 2.5 tons of ANFO to make "homemade" diamonds.
6996500000000000000♠5×10−4 581 MWh A real 0.5-kilotonne-of-TNT (2.1 TJ) charge at Operation Sailor Hat. If the charge were a full sphere, it would be 1 kilotonne of TNT (4.2 TJ).
500 tons of TNT (5 by 10 m (17 by 34 ft)) awaiting detonation at Operation Sailor Hat.
6997100000000000000♠1×10−3 (1 kiloton of TNT) – 6997200000000000000♠2×10−3 1.16–2.32 GWh Estimated yield of the Oppau explosion that killed more than 500 at a German fertilizer factory in 1921.
6997230000000000000♠2.3×10−3 2.67 GWh Amount of solar energy falling on 4,000 m2 (1 acre) of land in a year is 9.5 TJ (2,650 MWh) (an average over the Earth's surface).
6997300000000000000♠3×10−3 3.49 GWh The Halifax Explosion in 1917 was the accidental detonation of 3,000 tons of TNT.
6997400000000000000♠4×10−3 9.3 GWh Minor Scale, a 1985 United States conventional explosion, using 4,744 tons of ANFO explosive to provide a scaled equivalent airblast of an eight kiloton (33.44 TJ) nuclear device,[14] is believed to be the largest planned detonation of conventional explosives in history.
6998150000000000000♠1.5×10−2 – 6998200000000000000♠2×10−2 17.4–23.2 GWh The Little Boy atomic bomb dropped on Hiroshima on August 6, 1945, exploded with an energy of about 15 kilotons of TNT (63 TJ), and the Fat Man atomic bomb dropped on Nagasaki on August 9, 1945, exploded with an energy of about 20 kilotons of TNT (84 TJ). The modern nuclear weapons in the United States arsenal range in yield from 0.3 kt (1.3 TJ) to 1.2 Mt (5.0 PJ) equivalent, for the B83 strategic bomb.
1 1.16 TWh The energy contained in one megaton of TNT (4.2 PJ) is enough to power the average American household for 103,000 years.[15] The 30 Mt (130 PJ) estimated upper limit blast power of the Tunguska event could power the same average home for more than 3,100,000 years. The energy of that blast could power the entire United States for 3.27 days.[16]
3 3.5 TWh The total energy of all explosives used in World War Two, including the Hiroshima and Nagasaki atom bombs, is estimated to have been three megatons of TNT.
8.6 10 TWh The energy released by a typical tropical cyclone in one minute, primarily from water condensation. Winds constitute a quarter of a percent of that energy.[17]
21.5 25 TWh The complete conversion of 1 kg of matter into pure energy would yield the theoretical maximum (E = mc2) of 89.8 petajoules, which is equivalent to 21.5 megatons of TNT. No such method of total conversion as combining 500 grams of matter with 500 grams of antimatter has yet been achieved. In the event of proton–antiproton annihilation, approximately 50% of the released energy will escape in the form of neutrinos, which are almost undetectable.[18] Electron–positron annihilation events emit their energy entirely as gamma rays.
24 28 TWh Approximate total yield of the 1980 eruption of Mount St. Helens.
25, 50, 100 29 TWh, 58 TWh, 116 TWh During the Cold War, the United States developed hydrogen bombs with maximum theoretical yields of 25 megatons of TNT (100 PJ). The Soviet Union developed a prototype weapon, nicknamed the Tsar Bomba, which was tested at 50 Mt (210 PJ), but had a maximum theoretical yield of 100 Mt (420 PJ).[19] The effective destructive potential of such a weapon varies greatly, depending on such conditions as the altitude at which it is detonated, the characteristics of the target, the terrain, and the physical landscape upon which it is detonated.
26.3 30.6 TWh Megathrust earthquakes 2004 Indian Ocean earthquake released record ME surface rupture energy, or potential for damage at 26.3 megatons of TNT (110 PJ).
200 232 TWh The total energy released by the eruption of Mt. Krakatoa in Indonesia in 1883.
540 628 TWh The total energy produced worldwide by all nuclear testing and combat combined, from the 1940s till now[when?] is about 540 megatons.
1,460 1.69 PWh The total global nuclear arsenal is about 15,000 nuclear warheads[20][21][22] with a destructive capacity of around 1460 megatons[23][24][25][26] or 1.460 gigatons (1,460 million tons) of TNT.
62,500 73 PWh The total solar energy received by Earth per minute is 440 exajoules.
875,000 1,000 PWh Approximate yield of the last eruption of the Yellowstone supervolcano.
6,000,000 = 7006600000000000000♠6×106 6,973 PWh The estimated energy at impact when the largest fragment of Comet Shoemaker–Levy 9 struck Jupiter is equivalent to six million megatons (six trillion tons) of TNT.
7006932000000000000♠9.32×106 10,831 PWh The energy released in the 2011 Tōhoku earthquake and tsunami was over 200,000 times the surface energy and was calculated by the USGS at 3.9×1022 joules,[27] slightly less than the 2004 Indian Ocean quake. This is equivalent to 9,320 gigatons of TNT, or approximately 600 million times the energy of the Hiroshima bomb.
7006956000000000000♠9.56×106 11,110 PWh Megathrust earthquakes record huge MW values, or total energy released. The 2004 Indian Ocean earthquake released 9,560 gigatons TNT equivalent.
7008100000000000000♠1×108 116,222 PWh The approximate energy released when the Chicxulub impact caused the mass extinction sixty six million years ago was estimated to be equal to 100 teratons (i.e. 100 exagrams or approximately 220.462 quadrillion pounds) of TNT. That is roughly eight billion times stronger than each of the bombs that hit Hiroshima and Nagasaki and the most energetic event on the history of Earth for hundreds of millions of years, far more powerful than any volcanic eruption, earthquake or firestorm. Such an explosion annihilated everything within a thousand miles of the impact in a split second. Such energy is equivalent to that needed to power the whole Earth for several centuries.
7015597200000000000♠5.972×1015 6.94 × 1027 Wh The explosive energy of a quantity of TNT the mass of Earth.
7015789000000000000♠7.89×1015 9.17 × 1027 Wh Total solar output in all directions per day.
7021198000000000000♠1.98×1021 2.3 × 1033 Wh The explosive energy of a quantity of TNT the mass of the Sun.
7028239999999999999♠2.4×1028 – 7028479999999999999♠4.8×1028 2.8–5.6 × 1040 Wh A type 1a supernova explosion gives off 1–2×1044 joules of energy, which is about 2.4 to 4.8 hundred billion yottatons (24 to 48 octillion (2.4–4.8×1028) megatons) of TNT, equivalent to the explosive force of a quantity of TNT over a trillion (1012) times the mass of the planet Earth.
7030240000000000000♠2.4×1030 – 7030480000000000000♠4.8×1030 2.8–5.6 × 1042 Wh The largest type of supernova observed, gamma-ray bursts (GRBs) release more than 1046 joules of energy.[28]
7032130000000000000♠1.3×1032 1.5 × 1044 Wh A merger of two black holes, first observation of gravitational waves, released 5.3×1047 joules
Relative effectiveness factor[edit]
The relative effectiveness factor (RE factor), relates an explosive's demolition power to that of TNT, in units of the TNT equivalent/kg (TNTe/kg). The RE factor is the relative mass of TNT to which an explosive is equivalent: The greater the RE, the more powerful the explosive.
This enables engineers to determine the proper masses of different explosives when applying blasting formulas developed specifically for TNT. For example, if a timber-cutting formula calls for a charge of 1 kg of TNT, then based on octanitrocubane's RE factor of 2.38, it would take only 1.0/2.38 (or 0.42) kg of it to do the same job. Using PETN, engineers would need 1.0/1.66 (or 0.60) kg to obtain the same effects as 1 kg of TNT. With ANFO or ammonium nitrate, they would require 1.0/0.74 (or 1.35) kg or 1.0/0.42 (or 2.38) kg, respectively.
RE factor examples[edit]
Some RE factor examples
Explosive, Grade
Density
(g/ml)
Detonation
Vel. (m/s)
R.E.
Ammonium nitrate (AN + <0.5% H2O) 1.72 2700[29] 0.42
Mercury(II) fulminate 4.42 4250 0.51[30]
Tanerit Simply® (93% granulated AN + 6% red P + 1% C) 0.90 2750 0.55
Hexamine dinitrate (HDN) 1.30 5070 0.60
Dinitrobenzene (DNB) 1.50 6025 0.60
HMTD (hexamine peroxide) 0.88 4520 0.74
ANFO (94% AN + 6% fuel oil) 0.92 5270 0.74
TATP (acetone peroxide) 1.18 5300 0.80
Tovex® Extra (AN water gel) commercial product 1.33 5690 0.80
Hydromite® 600 (AN water emulsion) commercial product 1.24 5550 0.80
ANNMAL (66% AN + 25% NM + 5% Al + 3% C + 1% TETA) 1.16 5360 0.87
Amatol (50% TNT + 50% AN) 1.50 6290 0.91
Nitroguanidine 1.32 6750 0.95
Trinitrotoluene (TNT) 1.60 6900 1.00
Hexanitrostilbene (HNS) 1.70 7080 1.05
Nitrourea 1.45 6860 1.05
Tritonal (80% TNT + 20% aluminium)* 1.70 6650 1.05
Amatol (80% TNT + 20% AN) 1.55 6570 1.10
Nitrocellulose (13.5% N, NC; AKA guncotton) 1.40 6400 1.10
Nitromethane (NM) 1.13 6360 1.10
PBXW-126 (22% NTO, 20% RDX, 20% AP, 26% Al, 12% PU’s system)* 1.80 6450 1.10
Diethylene glycol dinitrate (DEGDN) 1.38 6610 1.17
PBXIH-135 EB (42% HMX, 33% Al, 25% PCP-TMETN’s system)* 1.81 7060 1.17
PBXN-109 (64% RDX, 20% Al, 16% HTPB’s system)* 1.68 7450 1.17
Triaminotrinitrobenzene (TATB) 1.80 7550 1.17
Picric acid (TNP) 1.71 7350 1.20
Trinitrobenzene (TNB) 1.60 7300 1.20
Tetrytol (70% tetryl + 30% TNT) 1.60 7370 1.20
Dynamite, Nobel's (75% NG + 23% diatomite) 1.48 7200 1.25
Tetryl 1.71 7770 1.25
Torpex (aka HBX, 41% RDX + 40% TNT + 18% Al + 1% wax)* 1.80 7440 1.30
Composition B (63% RDX + 36% TNT + 1% wax) 1.72 7840 1.33
Composition C-3 (78% RDX) 1.60 7630 1.33
Composition C-4 (91% RDX) 1.59 8040 1.34
Pentolite (56% PETN + 44% TNT) 1.66 7520 1.33
Semtex 1A (76% PETN + 6% RDX) 1.55 7670 1.35
Hexal (76% RDX + 20% Al + 4% wax)* 1.79 7640 1.35
RISAL P (50% IPN + 28% RDX + 15% Al + 4% Mg + 1% Zr + 2% NC)* 1.39 5980 1.40
Hydrazine mononitrate 1.59 8500 1.42
Mixture: 24% nitrobenzene + 76% TNM 1.48 8060 1.50
Mixture: 30% nitrobenzene + 70% nitrogen tetroxide 1.39 8290 1.50
Nitroglycerin (NG) 1.59 8100 1.54
Octol (80% HMX + 19% TNT + 1% DNT) 1.83 8690 1.54
Nitrotriazolon (NTO) 1.87 8120 1.60
DADNE (1,1-diamino-2,2-dinitroethene, FOX-7) 1.77 8330 1.60
Gelignite (92% NG + 7% nitrocellulose) 1.60 7970 1.60
Plastics Gel® (in toothpaste tube: 45% PETN + 45% NG + 5% DEGDN + 4% NC) 1.51 7940 1.60
Composition A-5 (98% RDX + 2% stearic acid) 1.65 8470 1.60
Erythritol tetranitrate (ETN) 1.72 8100 1.60
Hexogen (RDX) 1.78 8700 1.60
PBXW-11 (96% HMX, 1% HyTemp, 3% DOA) 1.81 8720 1.60
Penthrite (PETN) 1.71 8400 1.66
Ethylene glycol dinitrate (EGDN) 1.49 8300 1.66
TNAZ (trinitroazetidine) 1.85 8640 1.70
Octogen (HMX grade B) 1.86 9100 1.70
Tetranitroglycoluril (TNGU Sorguyl Sorguryl) 1.95 9150 1.76
HHTDD (hexanitrohexaazatricyclododecanedione DTNGU Naza/Namsorguyl/uryl HnHaza/amTcDglcDuryl) 2.16 9700 1.96
HNIW (CL-20) 1.97 9380 1.80
Hexanitrobenzene (HNB) 1.97 9400 1.85
MEDINA (Methylene dinitroamine) 1.65 8700 1.93
DDF (4,4’-Dinitro-3,3’-diazenofuroxan) 1.98 10000 1.95
Heptanitrocubane (HNC) 1.92 9200 N/A
Octanitrocubane (ONC) 1.95 10600 2.38
*: TBX (thermobaric explosives) or EBX (enhanced blast explosives), in a small, confined space, may have over twice the power of destruction. The total power of aluminized mixtures strictly depends on the condition of explosions.
Nuclear examples[edit]
Nuclear weapons and the most powerful non-nuclear weapon examples
Weapon
Total yield
(kilotons of TNT)
Weight
(kg)
R.E. ~
Davy Crockett (nuclear device) 0.022 23 1,000
Fat Man (dropped on Nagasaki) A-bomb 20 4600 4,500
Classic (one-stage) fission A-bomb 22 420 50,000
Hypothetical suitcase nuke 2.5 31 80,000
Typical (two-stage) nuclear bomb 500–1000 650–1120 900,000
W56 thermonuclear warhead 1,200 272–308 4,960,000
W88 modern thermonuclear warhead (MIRV) 470 355 1,300,000
B53 nuclear bomb (two-stage) 9,000 4050 2,200,000
B41 nuclear bomb (three-stage) 25,000 4850 5,100,000
Tsar nuclear bomb (three-stage) 50,000–56,000 26,500 2,100,000
GBU-57 bomb (Massive Ordnance Penetrator, MOP) 0.0035 13,600 0.26
Grand Slam (Earthquake bomb, M110) 0.0065 9,900 0.66
Bomb used in Oklahoma City (ANFO based on racing fuel) 0.0018 2,300 0.78
BLU-82 (Daisy Cutter) 0.0075 6,800 1.10
MOAB (non-nuclear bomb, GBU-43) 0.011 9,800 1.13
FOAB (advanced thermobaric bomb, ATBIP) 0.044 9,100 4.83
See also[edit]
Brisance
Net explosive quantity
Nuclear weapon yield
Orders of magnitude (energy)
Relative effectiveness factor
Table of explosive detonation velocities
Ton
Tonne
Tonne of oil equivalent, a unit of energy almost exactly 10 tonnes of TNT
References[edit]
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Jump up ^ "Joules to Megatons Conversion Calculator". unitconversion.org.
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Jump up ^ "Appendix B8 – Factors for Units Listed Alphabetically". In NIST SI Guide 2008
Jump up ^ Cooper, Paul W. (1996). Explosives Engineering. New York: Wiley-VCH. p. 406. ISBN 0-471-18636-8.
Jump up ^ Muller, Richard A. (2001–2002). "Chapter 1. Energy, Power, and Explosions". Physics for Future Presidents, a textbook. ISBN 978-1-4266-2459-9. Archived from the original on 2007-05-28.
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Jump up ^ Cunningham, Bruce J. (2001). C-4/tnt equivalency (Technical report). Lawrence Livermore National Laboratory. EMPE-01-81.
Jump up ^ "Arc blast Tri-Nitro-Toluene TNT Trotyl equivalent – ARCAD INC". arcblasts.com.
Jump up ^ Atassi, Basma; Sirgany, Sarah; Narayan, Chandrika (December 13, 2016). "Local media: Blast at Cairo cathedral kills at least 25". CNN. Retrieved 5 April 2017.
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Jump up ^ "Frequently Asked Questions – Electricity". United States Department of Energy. 2009-10-06. Retrieved 2009-10-21. (Calculated from 2007 value of 936 kWh monthly usage)
Jump up ^ "Country Comparison :: Electricity – consumption". The World Factbook. CIA. Archived from the original on 2012-01-28. Retrieved 2009-10-22. (Calculated from 2007 value of 3,892,000,000,000 kWh annual usage)
Jump up ^ "NOAA FAQ: How much energy does a hurricane release?". National Oceanic & Atmospheric Administration. August 2001. Retrieved 2009-06-30. cites 6e14 watts continuous.
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Jump up ^ See Currently deployed U.S. nuclear weapon yields Archived September 7, 2016, at the Wayback Machine., Complete List of All U.S. Nuclear Weapons Archived December 16, 2008, at the Wayback Machine., Tsar Bomba Archived June 17, 2016, at the Wayback Machine., all from Carey Sublette's Nuclear Weapon Archive.
Jump up ^ "Status of World Nuclear Forces". fas.org.
Jump up ^ "Nuclear Weapons: Who Has What at a Glance". armscontrol.org.
Jump up ^ "Global nuclear weapons: downsizing but modernizing". Stockholm International Peace Research Institute. 13 June 2016.
Jump up ^ Kristensen, Hans M.; Norris, Robert S. (May 3, 2016). "Russian nuclear forces, 2016". Bulletin of the Atomic Scientists. 72 (3): 125–134. doi:10.1080/00963402.2016.1170359 – via Taylor and Francis+NEJM.
Jump up ^ Kristensen, Hans M; Norris, Robert S (2015). "US nuclear forces, 2015". Bulletin of the Atomic Scientists. 71 (2): 107. doi:10.1177/0096340215571913.
Jump up ^ http://www.nrdc.org/nuclear/nudb/datab14.asp[dead link]
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Jump up ^ Maselli, A.; Melandri, A.; Nava, L.; Mundell, C. G.; Kawai, N.; Campana, S.; Covino, S.; Cummings, J. R.; Cusumano, G.; Evans, P. A.; Ghirlanda, G.; Ghisellini, G.; Guidorzi, C.; Kobayashi, S.; Kuin, P.; LaParola, V.; Mangano, V.; Oates, S.; Sakamoto, T.; Serino, M.; Virgili, F.; Zhang, B.- B.; Barthelmy, S.; Beardmore, A.; Bernardini, M. G.; Bersier, D.; Burrows, D.; Calderone, G.; Capalbi, M.; Chiang, J. (2013). "GRB 130427A: A Nearby Ordinary Monster". Science. 343 (6166): 48–51. doi:10.1126/science.1242279. PMID 24263134.
Jump up ^ US Army FM 3-34.214: Explosives and Demolition, 2007, page 1–2.
Jump up ^ Whitehall Paraindistries
Thompson, A.; Taylor, B.N. (July 2008). Guide for the Use of the International System of Units (SI). NIST Special Publication. 811. National Institute of Standards and Technology. Version 3.2.
Nuclear Weapons FAQ Part 1.3
Rhodes, Richard (2012). The Making of the Atomic Bomb (25th Anniversary ed.). Simon & Schuster. ISBN 978-1-4516-7761-4.
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HQ Department of the Army (2004) [1967], Field Manual 5-25: Explosives and Demolitions, Washington, D.C.: Pentagon Publishing, pp. 83–84, ISBN 0-9759009-5-1
Explosives - Compositions, Alexandria, VA: GlobalSecurity.org, retrieved September 1, 2010
Urbański, Tadeusz (1985) [1984], Chemistry and Technology of Explosives, Volumes I–IV (second ed.), Oxford: Pergamon
Mathieu, Jörg; Stucki, Hans (2004), "Military High Explosives", CHIMIA International Journal for Chemistry, Schweizerische Chemische Gesellschaft, 58 (6): 383–389, doi:10.2533/000942904777677669, ISSN 0009-4293
3. Thermobaric Explosives, Advanced Energetic Materials, 2004., The National Academies Press, nap.edu, 2004
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Boreal forest of Canada
From Wikipedia, the free encyclopedia
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Boreal Forests occur in the more southern parts of the Taiga ecoregion that spreads across the northern parts of the world.
Distribution of taiga and boreal forests in Canada and the United States (dark blue area in Canada and Alaska).
Canada's Boreal forest comprises about one third of the circumpolar boreal forest that rings the Northern Hemisphere, mostly north of the 50th parallel.[1] Other countries with boreal forest, also called taiga, include Russia, which contains the majority, the United States in its northernmost state of Alaska, and the Scandinavian or Northern European countries (e.g. Sweden, Finland, Norway and small regions of Scotland). The boreal region in Canada covers almost 60% of the country’s land area.[2] The Canadian boreal region spans the landscape from the most easterly part of the province of Newfoundland and Labrador to the border between the far northern Yukon and Alaska. The area is dominated by coniferous forests, particularly spruce, interspersed with vast wetlands, mostly bogs and fens. The boreal region of Canada includes eight ecozones. While the biodiversity of regions varies, each ecozone has a characteristic native flora and fauna.[3]
The boreal forest zone consists of closed-crown conifer forests with a conspicuous deciduous element (Ritchie 1987).[4] The proportions of the dominant conifers (white and black spruces, jack pine (Pinus banksiana Lamb.), tamarack, and balsam fir) vary greatly in response to interactions among climate,[5] topography, soil, fire, pests, and perhaps other factors.
The Canadian boreal region represents a tract of land over 1,000 kilometres wide separating the tundra in the north and temperate rain forest and deciduous woodlands that predominate in the most southerly and westerly parts of Canada. Canada's boreal forest is also considered to be the largest intact forest on earth, with around 3 million square kilometres still undisturbed by roads, cities and industrial development.[6] Its high level of intactness has made the forest a particular focus of environmentalists and conservation scientists who view the untouched regions of the forest as an opportunity for large-scale conservation that would otherwise be impractical in other parts of the world.
The boreal region contains about 13% of Canada’s population. With its sheer vastness and forest cover, the boreal makes an important contribution to the rural and aboriginal economies of Canada, primarily through resource industries, recreation, hunting, fishing and eco-tourism. Hundreds of cities and towns within its territory derive at least 20% of their economic activity from the forest, mainly from industries like forest products, mining, oil and gas and tourism.[7] The boreal forest also plays an iconic role in Canada’s history, economic and social development and the arts.[8]
Contents
1 Overview
1.1 General forest ecology
1.2 Ecosystems
1.3 Forest species
1.4 Inland water and wetlands
1.5 Deforestation
1.6 Wildlife
2 Boreal life cycles
2.1 Natural regeneration
2.2 Fire effects
3 Economic activities
3.1 Region-wide planning
3.2 Land ownership
3.3 Industrial activity
3.4 Aboriginal participation
3.5 Sustainable development
3.6 Certification for sustainable forest management
4 Protection
5 Boreal in culture and popular imagination
6 See also
7 References
8 Citations
9 External links
Overview[edit]
General forest ecology[edit]
The Canadian boreal forest in its current form began to emerge with the end of the last Ice Age. With the retreat of the Wisconsin Ice Sheet 10,000 years ago, spruce and northern pine migrated northward and were followed thousands of years later by fir and birch.[9] About 5000 years ago, the Canadian boreal began to resemble what it is today in terms of species composition and biodiversity. This type of coniferous forest vegetation is spread across the Northern Hemisphere. These forests contain three structural types: forest tundra in the north, open lichen woodland further south, and closed forest in more southern areas.[10] White spruce, black spruce and tamarack are most prevalent in the four northern eco-zones of the Taiga and Hudson Plains, while spruce, balsam fir, jack pine, white birch and trembling aspen are most common in the lower boreal regions. Large populations of trembling aspen and willow are found in the southernmost parts of the Boreal Plains.[11]
One dominant characteristic of the boreal is that much of it consists of large, even-aged stands, a uniformity that owes to a cycle of natural disturbances like forest fires, or outbreaks of pine beetle or spruce budworm that kill large tracts of forest with cyclical regularity.[10][12] For example, the many stands of white spruce, black spruce, and balsam fir are vulnerable to the cyclical outbreaks of a species of the spruce budworm, the Choristoneura fumiferana.[13][14] Since the melting of the great ice sheet, the boreal forest has been through many cycles of natural death through fire, insect outbreaks and disease, followed by regeneration. Prior to European colonization of Canada and the application of modern firefighting equipment and techniques, the natural burn/regeneration cycle was less than 75 to 100 years, and it still is in many areas.[15]
Terms like old growth and ancient forest have a different connotation in the boreal context than they do when used to describe mature coastal rain forests with longer-lived species and different natural disturbance cycles. However, the effects of forest fires and insect outbreaks differ from the effects of logging, so they should not be treated as equivalent in their ecological consequences. Logging, for example, requires road networks with their negative impacts,[16] and it removes nutrients from the site, which may deplete nutrients for the next cycle of forest growth.[10] Fire, on the other hand, recycles nutrients on location (except for some nitrogen), it removes accumulated organic matter and it stimulates reproduction of fire-dependent species.[17][18]
Ecosystems[edit]
Typical upland taiga in Quebec
Canada's boreal region can be divided into eight ecozones. These eight can be divided into two main groups. The northern regions of the boreal forest consists of four eco-zones – Taiga Cordillera, Taiga Plains, Taiga Shield and Hudson Plains – that are the most thinly treed areas where the growing season and average tree size progressively shrinks until the edge of the Arctic tundra is reached.[19] The southern tier of the boreal meanwhile consists of three other ecozones that form the largely uninterrupted or continuous forest in stretching as far south as Lake Superior in Ontario (as the Central Canadian Shield forests ecoregion) and the Manitoba-North Dakota border. These three southern zones are the Boreal Shield, at 1,630,000 square kilometres the largest of the eight zones, the Boreal Plains and Boreal Cordillera.[20] A typical ecoregion of this southern tier would be the Eastern Canadian Shield taiga that covers northern Quebec and most of Labrador. Finally the eighth zone is the balsam fir Abies balsamea forest that covers the higher elevations of the Laurentian Mountains and the northern Appalachian Mountains in eastern Quebec (especially the Gaspé Peninsula), on the island of Newfoundland, in the highlands of New Brunswick, and the Cape Breton Highlands on Cape Breton Island, Nova Scotia.[21][22] Within the boreal region, there are about 1,890,000 square kilometres that are between 80% to 100% forested and another 650,000 square kilometres with 60% to 80% forest cover.[21]
Forest species[edit]
The Calypso orchid grows in the shade of boreal forest.
Most trees native to the Canadian boreal are conifers, with needle leaves and cones. These include: black spruce, white spruce, balsam fir, larch (tamarack), lodgepole pine, and jack pine. A few are broad-leaved species: trembling and large-toothed aspen, cottonwood and white birch, and balsam poplar.[23] There are large areas of black spruce, a species which is tolerant of shallow soil, permafrost and waterlogged substrates, although as a consequence they have relatively low biological productivity.[24] Owing to the short growing season, generally infertile soils, generally shallow soils, and frequent waterlogging, most of these forest types are slow-growing species, which generally tend to predominate in stressed habitats.[25] Similarly, many of the understory shrubs are in the Ericaceae, a family known to tolerate acid, infertile and flooded habitats: examples include Labrador tea, sheep-laurel and blueberry. Since nutrient levels are so low, overall, the productivity of forest trees is highly dependent on the rate at which mineral elements such as nitrogen and phosphorus are recycled by litterfall and decomposition.[10] After logging, the loss of nutrients may convert forested areas into shrub barrens dominated by shrubs such as sheep-laurel.[26] Many of the plant species are fire-dependent, since fire removes neighbouring plants, and recycles nutrients locked in organic matter.
Although there are rather few species of trees in the boreal forest, there is a considerable diversity of other kinds of plants. An accurate summary is difficult, since most compendia on plants are organized by political, rather than ecological boundaries; one exception addresses the flora of the Hudson Bay Lowland,[27] but much of this area is not forested. One portion of the boreal forest can be used to illustrate plant diversity; consider the Flora of the Yukon.[28] In this western part of the boreal forest, there are, for example 127 species of grass (Poaceae), 118 species of Asteraceae, 115 species of sedge (Cyperaceae), 93 species of crucifer (Brassicaceae), 52 species of Rosaceae, 37 species of Saxifragaceae and 36 members of the snapdragon family (Scrophulariaceae). Overall, the flora has 1112 species—there are even 15 species of orchids.
A Sphagnum bog with spruce trees on a forested ridge in the background
Inland water and wetlands[edit]
Canada’s boreal landscape contains more lakes and rivers than any comparably sized landmass on earth. It has been estimated that the boreal region contains over 1.5 million lakes with a minimum surface area of 40,000 square metres as well as some of Canada’s largest lakes. Soft water lakes predominate in central and eastern Canada and hard water lakes predominate in Western Canada. Most large boreal lakes have cold water species of fish like trout and whitefish, while in warmer waters, species may include northern pike, walleye and smallmouth bass.[29]
The boreal forest also has vast areas of wetland, particularly bogs and fens.[30] Two wetland areas, the Hudson Bay Lowland and the Mackenzie River basin, are among the ten largest wetlands in the world.[31] The boreal forest wetlands provide wildlife habitat (particularly for migratory birds), they maintain water flow in rivers, and they store significant amounts of carbon that otherwise would be released to the atmosphere.[32]
Deforestation[edit]
Sheep laurel grows in clearings and shallow soils. It can form extensive shrub barrens after logging.
In contemporary times, the boreal forest has suffered little deforestation, defined as the permanent conversion of forest area to non-forest due to activities associated with agriculture, urban or recreational development, oil and gas development, and flooding for hydroelectric projects. In Alberta, the province with the largest oil and gas industry, more trees are cut for agriculture or oil and gas exploration than for timber.[33] In eastern Canada, over 9,000 square kilometres of peatlands and forest have been flooded over the past four decades for hydroelectric projects. Canada as a whole has 91% of the forest cover that existed at the dawn of European settlement. More deforestation has occurred outside the boreal region, in more southerly areas of the country.[33] The forest sector annually harvests approximately ½ of 1% of the region. However, this is not considered deforestation by some, given that provincial laws are meant to ensure that areas harvested by the forest sector are replanted or regenerated naturally.[33] However, the resulting road network from logging has effects that persist long beyond the period of harvest; indeed, one can make the case that road construction is one of the most harmful and persistent effects of logging.[16]
The Canada warbler nests on the ground in boreal forests.
Wildlife[edit]
There may be as many as five billion landbirds, including resident and migratory species. The Canadian boreal region contains the largest area of wetlands of any ecosystem of the world, serving as breeding ground for over 12 million waterbirds and millions of land birds, the latter including species as diverse as vultures, hawks, grouse, owls, hummingbirds, kingfishers, woodpeckers and passerines (or perching birds, often referred to as songbirds).[34] It is estimated that the avian population of the boreal represents 60% of the landbirds in all of Canada and almost 30% of all landbirds in the United States and Canada combined.[35]
Many of the wildlife species, are, like the forests, dependent upon natural disturbance from fire and insect outbreaks. For example, at least three species of warbler (Cape May warbler, bay-breasted warbler and Tennessee warbler), have distributions and abundance related to spruce budworm outbreaks.[36] The black-backed woodpecker shows a preference for burnt over forests, where it forages for insects burrowing in the dead trees that remain standing.[37] Fireweed, as the name suggests, is a plant that similar thrives in recently burned areas. Blueberries and huckleberries are also stimulated by fires, probably benefiting from the removal of shade, and the nutrients released in ashes. The resulting berries are an important food source for boreal forest animals.
Few species of boreal wildlife are classified under government conservation regimes as being at risk of extinction. However, the decline of some major species of wildlife is a concern. Boreal woodland caribou, whose lichen-rich, mature forest habitat spans the boreal forest from the Northwest Territories to Labrador, is designated as a threatened by the Committee on the Status of Endangered Wildlife in Canada.[38][39] The Newfoundland population of marten is threatened by habitat loss, accidental trapping and prey availability.[40]
Boreal life cycles[edit]
Natural regeneration[edit]
The particular mixture of tree species depends upon factors including soil moisture, soil depth, and organic content. Upland forests can be closely mixed with forested peatlands. The resulting conifer forests are produced by and dependent upon recurring disturbance from storms, fires, floods and insect outbreaks. Owing to the accumulated peat in the soil, and the predominance of coniferous trees, lightning-caused fire has always been a natural part of this forest. It is one of many ecosystems that depend upon such recurring natural disturbance.[41] For example, fire dependent species like lodgepole and jack pine have resin sealed cones. In a fire, the resin melts and the cones to open, allowing seeds to scatter so that a new pine forest begins (see also fire ecology). It has been estimated that prior to European settlement, this renewal process occurred on average every 75 to 100 years, creating even-aged stands of forest. Fire continues to cause natural forest disturbance,[42] but fire suppression and clear-cutting has interrupted these natural cycles, leading to significant changes in species composition.[43]
Boreal vegetation never attains stability because of interactions among fire, vegetation, soil–water relationships, frost action, and permafrost (Churchill and Hanson 1958, Spurr and Barnes 1980).[44][45] Wildfires produce a vegetation mosaic supporting an ever-changing diversity of plant and animal populations (Viereck 1973).[46] In the absence of fire, the accumulation of sphagnum peat on level upland sites would eventually oust coniferous vegetation and produce muskeg.
Fire effects[edit]
Fireweed is a native wildflower that grows after forest fires.
Despite today’s sophisticated and expensive fire-spotting and fire-fighting techniques, forest fires in Canada still burn, on average, about 28,000 square kilometres of boreal and other forest area annually. That average annual burn area is equivalent to more than three times the current annual industrial timber harvest. It can be many more times that in intense fire years.[47] However, although logging also removes trees, fire is not the same as logging, since fire has been a part of coniferous forests for millennia.[25] Fire not only stimulates regeneration of many plant species, it recycles phosphorus and removes accumulated organic matter. Fire is increasingly used as a management tool to maintain forest health in some parts of North America (see fire ecology). Different parts of the boreal have different burn cycles. The drier western region, which receives lower average rainfall, had higher natural fire frequencies. Hence, more area is burned annually on average in the west than in central and eastern Canada.[48] When natural burn cycles are interrupted by fire suppression, natural renewal is obstructed and species composition is changed. In addition, fire suppression causes fuel loads to increase so that fires, when they do occur, become more intense. One can argue that fire suppression actually creates a positive feed back loop, where ever more expensive fire suppression generates the conditions for ever larger fires. The negative effects of fire suppression are still under study, and not fully measured, but they need to be considered when making decisions about the future health of boreal forests.
Economic activities[edit]
Region-wide planning[edit]
Because parts of the boreal forest region are found in nearly every province and territory in Canada, there has not been much in the way of coordinated planning to develop the region. Prime Minister Diefenbaker talked of his "northern vision"[49] but little was done to see it come to pass. A proposal was authored by Richard Rohmer in 1967 called Mid-Canada Development Corridor: A Concept and was discussed by officials and politicians but was never implemented. In 2014, John van Nostrand attempted to revive the concept.[50]
In the absence of a nationwide plan, private industry and the provinces have pursued development in particular products or certain regions. These include the Athabasca Oil Sands in Alberta, the Ring of Fire (Ontario), and Quebec's Plan nord.
Land ownership[edit]
Main article: land ownership in Canada
Forest land in Canada is largely Crown land. Over 90% of the boreal forest is provincial Crown land; another 5% is federally controlled and includes national parks, First Nations reserves and national defence installations.[51]
Industrial activity[edit]
A skidder is used to clear forest and move logs.
About 1,400 communities within the Boreal region rely on resource industries for at least part of the livelihood and stability. Many of these communities were carved out of the forest to support a sawmill, pulp and paper mill, mine or railway maintenance facility. Boreal forestry activities support almost 400,000 direct and indirect jobs across Canada. Forestry, pulp and paper, mining, and oil and gas exploration and development are the largest industries along with tourism, trapping, recreation, light manufacturing and the services to support industry and communities. The forest products sector is one of Canada’s largest export industries, representing approximately 3% of GDP, with about half of the annual wood harvest coming from the boreal forest.[52]
Roughly one quarter of the boreal forest is managed for industrial forestry. The remaining three-quarters is either in parks, conservation areas, model forests or is considered non-timber-productive, generally defined as unsuitable for managed forestry or inaccessible. As recently as 2003, it was estimated that the annual harvest in the boreal was about 7,500 square kilometres per year, equivalent to about 0.2% of the total Canadian boreal forest.[53] The sharp downturn in the market for lumber because of the collapse of the housing market in the United States that began in 2006, coupled with import tariff and tax barriers, have knocked the bottom out of Canada's forest industry. In Ontario, Canada's most populous province, where most forestry activity is in the boreal, government statistics suggest that the harvest declined 18% from 2005 to 2006.[54] Given the high number of mill closings from 2005 onward, mostly in Ontario and Quebec, it is a trend that most likely persisted through 2007 and 2008.[55] Most of Canada's conventional onshore oil and gas production, including the rapidly expanding oil sands production in Alberta, is located in the boreal region as is Canada’s largest uranium producing zone in northern Saskatchewan and Quebec’s largest hydroelectric generating facilities in the La Grande watershed.
Aboriginal participation[edit]
About eighty percent of Canada's Aboriginal population resides[when?] in forested areas – including one million in over five hundred First Nations and Métis settlements in boreal zones. Of that amount, over 17,000 work in the forest products industry, mostly in silviculture and woodlands operations in the boreal and other forest regions.[56]
Sustainable development[edit]
Since the early 1990s, a strong impetus has been created to focus on conserving Canada's boreal legacy and sustainably managing economic activity within the entire region. The Canadian boreal is largely intact and available for multiple uses like timber harvest, recreation and hunting. Forestry companies have come to adopt the management practices known as eco-system based management, which takes into consideration criteria and indicators for sustainability – social, economic and environmental. A number of key principles have come to underpin Canadian forestry practices as mandated by forestry legislation, including the obligation for forestry companies operating on public lands to fully regenerate all areas harvested for timber and to consult the public on the preparation of forest management/harvest plans submitted to the relevant provincial authorities.
Certification for sustainable forest management[edit]
As a result of growing public concern with sustainable development and conserving the integrity of the boreal forests, conservation initiatives are progressing on various fronts. The area in national and provincial parks and protected conservation areas is approximately 10% of the total boreal area.[57] Most large forest products companies have certified their boreal forestry operations to one of three third-party, independently audited standards for sustainable forest management:
The Forest Stewardship Council's FSC Boreal Standard;
The Canadian standard CAN/CSA Z809;
The Sustainable Forestry Initiative.[58]
Sustainable Forest Management refers to managing a forest ecosystem in a manner that maintains and enhances its long-term health.
Protection[edit]
In July 2008 the Ontario government announced plans to protect 225,000 kilometres of the Northern Boreal lands.[59] In February 2010 the Canadian government established protection for 5,300 square miles (14,000 km2) of boreal forest by creating a new reserve of 4,100 square miles (11,000 km2) in the Mealy Mountains area of eastern Canada and a waterway provincial park of 1,200 square miles (3,100 km2) that follows alongside the Eagle River from headwaters to sea.[60] A report issued in 2011 by the Pew Environment Group described the Canadian boreal forest as the largest natural storage of freshwater in the world.[61][62]
Boreal in culture and popular imagination[edit]
The boreal forest is deeply ingrained in the Canadian identity and the images foreigners have of Canada. The history of the early European fur traders, their adventures, discoveries, aboriginal alliances and misfortunes is an essential part of the popular colonial history of Canada. The canoe, the beaver pelt, the coureur des bois, the voyageurs, the Hudson's Bay Company and the North-West Mounted Police, the construction of Canada’s transcontinental railways – all are symbols of Canadian history familiar to school children that are inextricably linked to the boreal forest.
The forest – and boreal species such as the caribou and loon – are or have been featured on Canadian currency. Another iconic and enduring image of the boreal was created by 20th-century landscape painters, most notably from the Group of Seven, who saw the uniqueness of Canada in its boreal vastness. The Group of Seven artists largely portrayed the boreal as natural, pure and unspoiled by human presence or activity and hence only partly a reflection of reality.[63]
See also[edit]
Geography of Canada portal
Environment of Canada
References[edit]
Jump up ^ State of Canada's Forests: 2004–2005, The Boreal Forest, Canadian Forest Service, ISBN 0-662-40014-3, p. 43
Jump up ^ Canadian Boreal Initiative online, http://www.borealcanada.ca/boreal-did-you-know-e.php; State of Canada’s Forests: 2004-2005, p. 43.
Jump up ^ State of Canada’s Forests: 2004-2005, p. 45, Map "Canada's Boreal Forest" inside back cover
Jump up ^ Ritchie, J.C. 1987. Postglacial Vegetation of Canada. Cambridge Univ. Press, Cambridge, U.K. 178 p.
Jump up ^ "Global Warming Cited as Wildfires; Increase in Fragile Boreal Forest Scientists say the near-destruction of Fort McMurray last week by a wildfire is the latest indication that the vital boreal forest is at risk from climate change". NYT. May 10, 2016. Retrieved 11 May 2016.
Jump up ^ Analysis produced by Global Forest Watch Canada, 2012.
Jump up ^ State of Canada’s Forests: 2004-2005, p. 55.
Jump up ^ State of Canada’s Forests: 2004-2005, p. 48.
Jump up ^ State of Canada’s Forests, 2004–2005, pp. 46–47.
^ Jump up to: a b c d Archibold, O. W. 1995. Ecology of World Vegetation. London: Chapman and Hall.
Jump up ^ "Canada's Boreal Forest", Forest Products Association of Canada, map, inside front cover.
Jump up ^ Ludwig, D., D. D. Jones, and C. S. Holling. 1978. Qualitative analysis of insect outbreak systems: the spruce budworm and forest. Journal of Animal Ecology 47: 315–332.
Jump up ^ Swaine, J.M.; Craighead, F.C.; Bailey, J.W. 1924. Studies on the spruce budworm Cacoecia fumiferana Clem. Can. Dep. Agric., Ottawa ON, Tech. Bull. 37 (N.S.).
Jump up ^ Balch, R.E.; Webb, F.E.; Morris, R.F. 1954. Results of spraying against spruce budworm in New Brunswick. Can. Dep. Agric., For. Biol. Div., Ottawa ON, Bi-mo. Progr. Rep. 10(1).
Jump up ^ "The Nature of Forest Fires," State of Canada's Forests, 2003–2004, ISBN 0-662-37602-1, p. 47.
^ Jump up to: a b Forman, R. T. T., D. Sperling, J. Bissonette, A. P. Clevenger, C. D. Cutshall, V. H. Dale, L. Fahrig, R. France, C. R. Goldman, K. Heanue, J. A. Jones, F. J. Swanson, T. Turrentine, and T. C. Winter. 2002. Road Ecology: Science and Solutions. Washington: Island Press.
Jump up ^ Rowe, J. S. and G. W. Scotter. 1973. Fire in the boreal forest. Quaternary Research 3: 444–464.
Jump up ^ Heinselman, M. L. 1981. Fire and succession in the conifer forests of northern North America. pp. 374–405. In D. C. West, H.H. Shugart, and D. B. Botkin (eds.) Forest Succession: Concepts and Applications. New York: Springer-Verlag.True facterino
Jump up ^ State of Canada's Forests: 2004–2005, p. 40.
Jump up ^ State of Canada's Forests: 2004–2005, Map "Canada's Boreal Forest", inside back cover.
^ Jump up to: a b State of Canada’s Forests: 2004-2005, Map "Canada's Boreal Region", inside back cover
Jump up ^ "Eastern Canadian forests". Terrestrial Ecoregions. World Wildlife Fund.
Jump up ^ Archibold, O. W. 1995. Ecology of World Vegetation. London: Chapman and Hall. Chapter 8.
Jump up ^ C. Michael Hogan. 2008. Black Spruce: Picea mariana, GlobalTwitcher.com, ed. Nicklas Stromberg, November 2008 Archived October 5, 2011, at the Wayback Machine..
^ Jump up to: a b Keddy, P.A. 2007. Plants and Vegetation: Origins, Processes, Consequences. Cambridge University Press, Cambridge, UK. 666 p.
Jump up ^ Weetman, G. F. 1983. Forestry practices and stress on Canadian forest land. pp. 260–301. In W. Simpson-Lewis, R. McKechnie, and V. Neimanis (eds.) Stress on Land in Canada. Ottawa: Lands Directorate, Environment Canada.
Jump up ^ Riley, J.L. 2003. Flora of the Hudson Bay Lowland and its Postglacial Origins.NRC Research Press, Ottawa, Canada. 236 p.
Jump up ^ Cody, W.J. 1996. Flora of the Yukon Territory.NRC Research Press, Ottawa, Canada. 643 p.
Jump up ^ "Boreal fresh waters", State of Canada's Forests 2004-2005, pp. 70-71
Jump up ^ National Wetlands Working Group. 1988. Wetlands of Canada.Jesse Graham Likes to party Canada Committee on Ecological Land Classification, Environment Canada. 452 p.
Jump up ^ Fraser, L.H. and P.A. Keddy (eds.). 2005. The World's Largest Wetlands: Ecology and Conservation. Cambridge University Press, Cambridge, UK.
Jump up ^ Vitt, D.H., L.A. Halsey and B.J. Nicholson. 2005. The Mackenzie River basin. Pp. 166–202 in L.H. Fraser and P.A. Keddy (eds.). The World’s Largest Wetlands: Ecology and Conservation. Cambridge University Press, Cambridge, UK.
^ Jump up to: a b c State of Canada's Forests 2004–2005, p 40
Jump up ^ "Birds in Canada's Boreal Forest: New paradigms for paradise found", State of Canada’s Forests 2005–2006, p 72
Jump up ^ Peter Blancher, "Importance of Canada’s Boreal Forest to Landbirds", Canadian Boreal Initiative and Boreal Songbird Initiative, May 2003, p. ii, "Archived copy". Archived from the original on 2008-05-21. Retrieved 2008-05-27.
Jump up ^ Cadman, M.D., P.F.J. Eagles, and F.M. Helleiner. Atlas of the Breeding Birds of Ontario. University of Waterloo Press, Waterloo. p. 376
Jump up ^ Cadman, M.D., P.F.J. Eagles, and F.M. Helleiner. Atlas of the Breeding Birds of Ontario. University of Waterloo Press, Waterloo. p. 244
Jump up ^ Natural Resources Canada 2000, p. 14.
Jump up ^ Culling & Culling 2006, p. 1.
Jump up ^ “Forest Associated Species at Risk”, State of Canada’s Forests 2004-2005, pp 77-79; http://www.newfoundlandmarten.com/page.php?pid=21
Jump up ^ Keddy, P.A. 2007. Plants and Vegetation: Origins, Processes, Consequences. Cambridge University Press, Cambridge, UK. 666 p.
Jump up ^ "Fire in the Forest", State of Canada's Forests, 2003-2004, p. 47
Jump up ^ Carleton, T. J. and P. MacLellan. 1994. Woody vegetation responses to fire versus clear-cutting logging: a comparative survey in the central Canadian boreal forest. Ecoscience 1: 141–152.
Jump up ^ Churchill, E.D.; Hanson, H.C. 1958. The concept of climax in arctic and alpine vegetation. Bot. Rev. 24:127–191.
Jump up ^ Spurr, S.H.; Barnes, B.V. 1980. Forest ecology, 3rd ed. Wiley, New York NY. 687 p.
Jump up ^ Viereck, L.A. 1973. Wildfire in the taiga of Alaska. Quaternary Res. 3:465–495.
Jump up ^ “Disturbances and Renewal in the Forest”, State of Canada’s Forests, 2003–2004, p. 74
Jump up ^ State of Canada’s Forests 2003–2004, p 69
Jump up ^ "The Northern Vision". www.canadahistory.com.
Jump up ^ http://thewalrus.ca/if-we-build-it-they-will-stay/
Jump up ^ State of Canada's Forests 2004-2005, p. 49
Jump up ^ State of Canada's Forests 2004–2005, p. 57
Jump up ^ State of Canada's Forests 2004–2005, p. 48
Jump up ^ Natural Resources Canada, statistical data, http://canadaforests.nrcan.gc.ca/statsprofile
Jump up ^ "Mill Closures and Mill Investments in the Canadian Forest Sector", State of Canada’s Forests, 2005–2006, pp 46–55.
Jump up ^ "Aboriginal Partnerships in the Forest", State, The State of Canada's Forests, 2007, National Resources Canada, ISBN 978-0-662-46538-6, p. 21; Canadian Boreal Initiative, Borealcanada.ca/boreal-did-you-know-e.php; "Aboriginal Issues in Canada's Boreal Forest", Summary, National Round Table on the Environment and the Economy.
Jump up ^ "Sustainable Forest Management in Canada", State of Canada's Forests, 2007, p. 6
Jump up ^ "Canadian Sustainable Forestry Certification Coalition - Coalition can…". 23 July 2012. Archived from the original on 23 July 2012.
Jump up ^ "Protecting a Northern Boreal region one-and-a-half times the size of the Maritimes". Office of the Premier. 2008-07-14. Archived from the original on 2009-01-31. Retrieved 2008-07-31.
Jump up ^ Braun, David (February 7, 2010). "Boreal landscapes added to Canada's parks Boreal landscapes added to Canada's parks". NatGeo News Watch: News Editor David Braun's Eye on the World. National Geographic Society. Retrieved 17 February 2010.
Jump up ^ Pew Environment Group. A Forest of Blue: Canada's Boreal Forest. March 16, 2011
Jump up ^ Munro, Margaret (March 16, 2011). "Canada urged to protect water in boreal forests". The Vancouver Sun. Retrieved 16 March 2011.
Jump up ^ “The boreal muse of the Group of Seven; Creating a national identity from a palette of boreal colours”, Canadian Geographic, Jan/Feb 2004, "Archived copy". Archived from the original on 2008-02-21. Retrieved 2008-05-27.
Citations[edit]
Culling, Diane E.; Culling, Brad A. (May 2006), Ecology and seasonal habitat selection of boreal caribou in the Snake-Sahtaneh watershed, British Columbia: 2000 to 2004 (PDF), Fort St. John, British Columbia, archived from the original (PDF) on 21 December 2013, retrieved 19 December 2013
"State of Canada's Forests 1999-2000: Forests in the New Millennium" (PDF), Natural Resources Canada, Ottawa, Ontario, 2000, ISBN 0-662-29069-0, retrieved 19 December 2013
External links[edit]
Media related to Boreal forest of Canada at Wikimedia Commons
Map of Canadian Ecozones.
The Alberta Centre for Boreal Studies
Boreal Songbird Initiative
Map of world's largest wetlands.
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Megaspore mother cell
From Wikipedia, the free encyclopedia
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Development of the megagametophyte and fertilization in Arabidopsis thaliana.
MMC - megaspore mother cell; FM - functional megaspore; AP - antipodal cells; CC - central cell; EC - egg cell; SC - synergid cell; PT - pollen tube; SP - sperm; VN - vegetative nucleus; EM - embryo; EN - endosperm; SUS - suspensor
A megaspore mother cell, or megasporocyte, is a diploid cell in plants in which meiosis will occur, resulting in the production of four haploid megaspores. At least one of the spores develop into haploid female gametophytes (megagametophytes).[1] The megaspore mother cell arises within the megasporangium tissue.
In flowering plants the megasporangium is also called the nucellus, and the female gametophyte is sometimes called the embryo sac.
Contents
[hide]
1 Developmental processes
2 Meiosis
3 See also
4 References
Developmental processes[edit]
Two distinct processes are involved in producing the megagametophyte from the megaspore mother cell:
Megasporogenesis, formation of the megaspores in the megasporangium (nucellus) by meiosis
Megagametogenesis; development of the megaspore(s) into the megagametophyte(s) which contains the gametes.[2]
In gymnosperms and most flowering plants, only one of the four megaspores is functional at maturity, and the other three soon degenerate. The megaspore that remains divides mitotically and develops into the gametophyte, which eventually produces one egg cell.[2] In the most common type of megagametophyte development in flowering plants (the Polygonum type), three mitotic divisions are involved in producing the gametophyte, which has seven cells, one of which (the central cell) has two nuclei that later merge to make a diploid nucleus.
In flowering plants, double fertilization occurs, which involves two sperm fertilizing the two gametes inside the megagametophyte (the egg cell and the central cell) to produce the embryo and the endosperm.
Meiosis[edit]
In Arabidopsis, actin-related proteins regulate female meiosis by modulating meiotic gene expression in the megaspore mother cell.[3] One of the key genes whose expression is regulated is Dmc1, a gene that plays a central role in the strand-exchange reactions of meiotic recombinational repair.
See also[edit]
Microspore, spores that develop into male gametophytes
References[edit]
Jump up ^ Solomon, Eldra P., 2005, Biology, Thomson, Brooks/Cole, United States
^ Jump up to: a b Raven, Peter H., 2005, Biology of Plants, W.H. Freeman and Company Publishers, United States
Jump up ^ Qin Y, Zhao L, Skaggs MI, Andreuzza S, Tsukamoto T, Panoli A, Wallace KN, Smith S, Siddiqi I, Yang Z, Yadegari R, Palanivelu R (2014). "ACTIN-RELATED PROTEIN6 Regulates Female Meiosis by Modulating Meiotic Gene Expression in Arabidopsis". Plant Cell. 26 (4): 1612–1628. doi:10.1105/tpc.113.120576. PMC 4036575  . PMID 24737671.
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