Southern Research Station

Title: Human influence on the abundance and connectivity of high-risk fuels in mixed forests of northern Wisconsin, USA

Author: Sturtevant, Brian R.; Zoller, Patrick A.; Gustafson, Eric J.; Cleland, David T.

Date: 2004

Source: Landscape Ecology 19: 235-253

Description: Though fire is considered a "natural" disturbance, humans heavily influence modern wildfire regimes. Humans influence fires both directly, by igniting and suppressing fires, and indirectly, by either altering vegetation, climate, or both. We used the LANDIS disturbance and succession model to compare the relative importance of a direct human influence (suppression of low intensity surface fires) with an indirect human influence (timber harvest) on the long-term abundance and connectivity of high-risk fuel in a 2791 km² landscape characterized by a mixture of northern hardwood and boreal tree species in northern Wisconsin. High risk fuels were defined as a combination of sites recently disturbed by wind and sites containing conifer species/cohorts that might serve as "ladder fuel" to carry a surface fire into the canopy. Two levels of surface fire suppression (highlcurrent and low) and three harvest alternatives (no harvest, hardwood emphasis, and pine emphasis) were compared in a 2x3 factorial design using 5 replicated sin~ulations per treatment combination over a 250-year period. Multivariate analysis of variance indicated that the landscape pattern of high-risk fuel (proportion of landscape, mean patch size, nearest neighbor distance, and juxtaposition with non fuel sites) was significantly influenced by both surface fire suppression and by forest harvest (p > 0.0001). However, the two human influences also interacted with each other (p < 0.001), because fire suppression was less likely to influence fuel connectivity when harvest disturbance was simultaneously applied. Temporal patterns observed for each of seven conifer species indicated that disturbances by either fire or harvest encouraged the establishment of moderately shade-tolerant conifer species by disturbing the dominant shade tolerant competitor, sugar maple. Our results conflict with commonly reported relationships between fire suppression and fire risk observed within the interior west of the United States. and illustrate the importance of understanding key interactions between natural disturbance, human disturbance, and successional responses to these disturbance types that will eventuall dictate future fire risk.

Keywords: Fire risk, fire suppression, fuel distribution, LANDIS, landscape pattern, simulation model, succession, timber harvest

View and Print this Publication (2.0 MB)

Pristine Version:  An uncaptured or "pristine" version of this publication is available. It has not been subjected to OCR (Optical Character Recognition) and therefore does not have any errors in the text. However it is a larger file size and some people may experience long download times. The "pristine" version of this publication is available here:

View and Print the PRISTINE copy of this Publication (2.6 MB)

Publication Notes: 

• We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
• This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

 Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

Citation

Sturtevant, Brian R.; Zoller, Patrick A.; Gustafson, Eric J.; Cleland, David T.  2004.  Human influence on the abundance and connectivity of high-risk fuels in mixed forests of northern Wisconsin, USA.   Landscape Ecology 19: 235-253