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Fire in boreal forests : climatic influences on the number and sizes of fires in recent Canadian forests and the size-area relationship in a Swedish site over the last 800 years

Johansson, Andrea LU (2011) In Lunds universitets Naturgeografiska institution - Seminarieuppsatser NGEM01 20111
Dept of Physical Geography and Ecosystem Science
Abstract (Swedish)
För att se om brand regimerna i Sverige före större antropogena påverkningar skett år jämförbara med nutida Kanadensiska brand regimer jämförde jag två datasets av brand storlek och antal bränder. Man kan se likheter när Kanada och Sveriges brand regimer jämfördes, men eftersom sökarean varierade mycket (Kanada: hela landet, Sverige: 608km2) och den temporala upplösningen (Kanada: 41 år, Sverige: 800 år), inget signifikant resultat fanns. Den ‘effektiva brand storleken‘ (definition s. 27) räknades ut för fyra skogstyper i Kanada (barrskog, lövskog, blandskog och övergående skog), en signifikant skillnad i den effektiva brand storleken kunde ses för barrskogen och lövskogen mot de andra skogstyperna.
Vädret används ofta för att förutse... (More)
För att se om brand regimerna i Sverige före större antropogena påverkningar skett år jämförbara med nutida Kanadensiska brand regimer jämförde jag två datasets av brand storlek och antal bränder. Man kan se likheter när Kanada och Sveriges brand regimer jämfördes, men eftersom sökarean varierade mycket (Kanada: hela landet, Sverige: 608km2) och den temporala upplösningen (Kanada: 41 år, Sverige: 800 år), inget signifikant resultat fanns. Den ‘effektiva brand storleken‘ (definition s. 27) räknades ut för fyra skogstyper i Kanada (barrskog, lövskog, blandskog och övergående skog), en signifikant skillnad i den effektiva brand storleken kunde ses för barrskogen och lövskogen mot de andra skogstyperna.
Vädret används ofta för att förutse brandfara, brand indexer som till exempel Nesterov brand index. I analyserna som genomfördes här, korrelerades det dagliga vädret med antalet bränder och med brand storlekarna i Kanada. Inget samband hittades mellan vädret och brand storlekarna. Ett brev mönster kunde ses, där vädret begränsar maximum storleken men inte har någon effekt på minimum storleken. Detta beror troligtvis på att det finns många orsaker till att utbredningen av en brand skulle bli begränsad, så kallade brand barriärer.
En GLM regression modell kördes för att se om ett mer signifikant resultat var möjligt om man inte använder sig av en linjär korrelation mellan brandstorlekarna och vädret, men ingen bra korrelation hittades.
För att testa om brand mönster beror på storskaliga klimat variationer, gjordes en korrelation mellan NAO, PNA, TNH, PT, AO, ENSO och den effektiva brand storleken, standard medel brand storleken, antal bränder och total bränd area per år. Ett samband fanns mellan standard medel brand storleken och NAO och TNH. Om man tittar på hela Kanada som en helhet så kan man inte finna någon korrelation mellan NAO, PNA, TNH, PT, AO, ENSO och den effektiva brand storleken, antal bränder och total bränd area per år.
Jämför med andra områden (t.ex. Afrika), så är länken mellan bränder och storskaliga väderfenomen svag eftersom eld startnings mönstret är mycket slumpmässigt, vilket inte kan ses när det tillgängliga klimat data använts. (Less)
Abstract
To assess if the fire regimes in Sweden before the strong human intervention are comparable to the recent Canadian fire regime I compared two datasets of fire numbers. A likeness could be found when comparing the Swedish and Canadian fire regimes, but due to the differences in study area (Canada: the whole state; Sweden 608km2) and time span (Canada: 41 years, Sweden: 800 years), no significant result could be determined. The effective fire size (definition p. 27) were calculated for the four forest types in Canada (coniferous, broadleaf, mixed and transitional), a significant difference in the effective fire size is present when assessing the broadleafed and the coniferous forests with the other forest types.
The weather is often used to... (More)
To assess if the fire regimes in Sweden before the strong human intervention are comparable to the recent Canadian fire regime I compared two datasets of fire numbers. A likeness could be found when comparing the Swedish and Canadian fire regimes, but due to the differences in study area (Canada: the whole state; Sweden 608km2) and time span (Canada: 41 years, Sweden: 800 years), no significant result could be determined. The effective fire size (definition p. 27) were calculated for the four forest types in Canada (coniferous, broadleaf, mixed and transitional), a significant difference in the effective fire size is present when assessing the broadleafed and the coniferous forests with the other forest types.
The weather is often used to predict the fire danger, using fire indices such as the Nesterov fire index. In this analysis the correlations between the daily weather and the number of fires and the fire size were assessed over Canada. No relationship between the fire size and the weather was detected. An envelope pattern was assessed, in which the weather limits the maximum size of the fires but has no effect on the minimum size. This is most probably due to a number of additional factors limiting the spread of the fires (e.g. fire barriers).
A GLM regression model was carried out to assess if a more significant result was detected when not using a linear correlation for the correlation between the burnt area and the fire indices, but no good correlation could be found.
To test whether large scale climate pattern influence the fire pattern, a correlation was carried out between the teleconnections NAO, PNA, TNH, PT, AO, ENSO and the effective fire size, standard mean fire size, number of fires and total burnt area per year. A significant correlation was found between the standard mean fire size and the teleconnections NAO and TNH. When assessing the whole of Canada there is no correlation between the teleconnections in the northern Hemisphere and the effective fires size, number of fires and total burnt area.
Compared to other areas (e.g. Africa), the link between fires and large scale weather conditions is rather weak due to the randomness in the ignition pattern, which cannot be assessed using the available climate data. (Less)
Please use this url to cite or link to this publication:
author
Johansson, Andrea LU
supervisor
organization
alternative title
Bränder i boreala skogar : hur klimatet påverkar antalet och storlekarna på skogsbränderna i dagens Kanada och förhållandet mellan storlekarna, arean på en plats i Sverige över de sista 800 åren
course
NGEM01 20111
year
type
H2 - Master's Degree (Two Years)
subject
keywords
geography, physical geography, forest fire, weather, climate, teleconnection, geografi, naturgeografi, väder, klimat, skogsbrand, Kanada, Canada
publication/series
Lunds universitets Naturgeografiska institution - Seminarieuppsatser
report number
228
language
English
id
2439034
date added to LUP
2012-04-13 13:05:28
date last changed
2012-04-13 13:10:53
@misc{2439034,
  abstract     = {To assess if the fire regimes in Sweden before the strong human intervention are comparable to the recent Canadian fire regime I compared two datasets of fire numbers. A likeness could be found when comparing the Swedish and Canadian fire regimes, but due to the differences in study area (Canada: the whole state; Sweden 608km2) and time span (Canada: 41 years, Sweden: 800 years), no significant result could be determined. The effective fire size (definition p. 27) were calculated for the four forest types in Canada (coniferous, broadleaf, mixed and transitional), a significant difference in the effective fire size is present when assessing the broadleafed and the coniferous forests with the other forest types.
The weather is often used to predict the fire danger, using fire indices such as the Nesterov fire index. In this analysis the correlations between the daily weather and the number of fires and the fire size were assessed over Canada. No relationship between the fire size and the weather was detected. An envelope pattern was assessed, in which the weather limits the maximum size of the fires but has no effect on the minimum size. This is most probably due to a number of additional factors limiting the spread of the fires (e.g. fire barriers).
A GLM regression model was carried out to assess if a more significant result was detected when not using a linear correlation for the correlation between the burnt area and the fire indices, but no good correlation could be found.
To test whether large scale climate pattern influence the fire pattern, a correlation was carried out between the teleconnections NAO, PNA, TNH, PT, AO, ENSO and the effective fire size, standard mean fire size, number of fires and total burnt area per year. A significant correlation was found between the standard mean fire size and the teleconnections NAO and TNH. When assessing the whole of Canada there is no correlation between the teleconnections in the northern Hemisphere and the effective fires size, number of fires and total burnt area.
Compared to other areas (e.g. Africa), the link between fires and large scale weather conditions is rather weak due to the randomness in the ignition pattern, which cannot be assessed using the available climate data.},
  author       = {Johansson, Andrea},
  keyword      = {geography,physical geography,forest fire,weather,climate,teleconnection,geografi,naturgeografi,väder,klimat,skogsbrand,Kanada,Canada},
  language     = {eng},
  note         = {Student Paper},
  series       = {Lunds universitets Naturgeografiska institution - Seminarieuppsatser},
  title        = {Fire in boreal forests : climatic influences on the number and sizes of fires in recent Canadian forests and the size-area relationship in a Swedish site over the last 800 years},
  year         = {2011},
}