Effect of prior disturbances on the extent and severity of wildfire in Colorado subalpine forests
Disturbances are important in creating spatial heterogeneity of vegetation patterns that in turn may affect the spread and severity of subsequent disturbances. Between 1997 and 2002 extensive areas of subalpine forests in northwestern Colorado were affected by a blowdown of trees, bark beetle outbreaks, and salvage logging. Some of these stands were also affected by severe fires in the late 19th century. During a severe drought in 2002, fires affected extensive areas of these subalpine forests. We evaluated and modeled the extent and severity of the 2002 fires in relation to these disturbances that occurred over the five years prior to the fires and in relation to late 19th century stand-replacing fires. Occurrence of disturbances prior to 2002 was reconstructed using a combination of tree-ring methods, aerial photograph interpretation, field surveys, and geographic information systems (GIS). The extent and severity of the 2002 fires were based on the normalized difference burn ratio (NDBR) derived from satellite imagery. GIS and classification trees were used to analyze the effects of prefire conditions on the 2002 fires. Previous disturbance history had a significant influence on the severity of the 2002 fires. Stands that were severely blown down (>66% trees down) in 1997 burned more severely than other stands, and young (∼120 year old) postfire stands burned less severely than older stands. In contrast, prefire disturbances were poor predictors of fire extent, except that young (∼120 years old) postfire stands were less extensively burned than older stands. Salvage logging and bark beetle outbreaks that followed the 1997 blowdown (within the blowdown as well as in adjacent forest that was not blown down) did not appear to affect fire extent or severity. Conclusions regarding the influence of the beetle outbreaks on fire extent and severity are limited, however, by spatial and temporal limitations associated with aerial detection surveys of beetle activity. Thus, fire extent in these forests is largely independent of prefire disturbance history and vegetation conditions. In contrast, fire severity, even during extreme fire weather and in conjunction with a multiyear drought, is influenced by prefire stand conditions, including the history of previous disturbances. © 2007 by the Ecological Society of America.
Abies lasiocarpa, blowdown, classification trees, disturbance interactions, fire, Picea engelmannii, Spruce beetle, Subalpine forests
Kulakowski, Dominik and Veblen, Thomas T., "Effect of prior disturbances on the extent and severity of wildfire in Colorado subalpine forests" (2007). Geography. 314.
Madhara ya uharibifu wa mapema juu ya kiwango na ukali wa moto wa misitu ya Colorado ya subalpine Uharibifu ni muhimu katika kuunda heterogeneity ya nafasi ya mifumo ya mimea ambayo inaweza kuathiri kuenea na ukali wa uharibifu wa baadaye. Kati ya mwaka wa 1997 na 2002, maeneo makubwa ya misitu ya chini ya milima ya Alps kaskazini magharibi mwa Colorado yaliathiriwa na kupigwa kwa miti, kuenea kwa wadudu wa bark beetle, na ukataji wa miti. Baadhi ya viwanja hivyo vilikumbwa na moto mkubwa mwishoni mwa karne ya 19. Wakati wa ukame mkubwa wa mwaka 2002, moto ulisababisha uharibifu mkubwa katika maeneo hayo ya misitu ya chini ya milima ya Alps. "Tuliamua na kuunda mfano wa kiwango na ukali wa moto wa 2002 kuhusiana na usumbufu huu uliofanyika zaidi ya miaka mitano kabla ya moto na kuhusiana na moto wa mwisho wa karne ya 19 ""kuchukua nafasi ya kusimama.""" Utafiti wa hali ya hewa ulifanyika kabla ya mwaka 2002 na kuunganisha njia za kuchunguza miti, kuchunguza picha za angani, kuchunguza maeneo, na kutumia mfumo wa habari za kijiografia. Uwezo wa moto huo uligunduliwa kwa kutumia kiwango cha tofauti ya kuchoma (NDR) kilichopatikana katika picha za satelaiti. GIS na miti ya uainishaji ilitumiwa kuchambua athari za hali ya moto kwenye moto wa 2002. Historia ya machafuko ya zamani ilikuwa na ushawishi mkubwa juu ya ukali wa moto wa 2002. Miti iliyopigwa na upepo (kwa asilimia 66 ya miti iliyopigwa) mwaka 1997 ilichomwa moto kwa kiasi kikubwa kuliko miti mingine, na miti mipya (ya miaka 120) ilichomwa moto kwa kiasi kidogo kuliko miti ya zamani. Kwa upande mwingine, msukosuko wa moto wa mapema ulikuwa utabiri duni wa kiwango cha moto, isipokuwa kwamba vijana (miaka 120) baada ya moto wa moto walikuwa chini ya kuungua kwa kiasi kikubwa kuliko watu wazima. Kuanguka kwa misitu na kuzuka kwa magugu ya mbao baada ya mlipuko wa 1997 (ndani ya mlipuko huo na pia katika msitu ulio karibu ambao haukuangushwa) haukuonekana kuathiri kiwango cha moto au ukali. Hata hivyo, matokeo kuhusu athari za milipuko ya vimelea kwenye kiwango cha moto na ukali ni mdogo, na mipaka ya nafasi na muda kuhusishwa na uchunguzi wa angani wa shughuli za vimelea. Hivyo, upeo wa moto katika misitu hii ni kwa kiasi kikubwa huru ya historia ya usumbufu prefire na hali ya mimea. Kwa kulinganisha, ukali wa moto, hata wakati wa hali ya hewa kali ya moto na pamoja na ukame wa miaka mingi, unaathiriwa na hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali ya hali. 2007 - Shirika la Mazingira la Marekani "Abies laoscarpa, blowdown, classification trees, disturbance interactions, fire, P. engelmannii, spruce beetle, subalpine forests, Kulakowski, Dominik, and Veblen, Thomas T., ""Effect of previous disturbances on the extent and severity of wildfires in Colorado subalpine forests"" (2007)." Jiografia. 314 - Uwezo wa kuongoza