scholarly journals PRESCRIBED FIRE IN OAK SAVANNA: FIRE FREQUENCY EFFECTS ON STAND STRUCTURE AND DYNAMICS

2001 ◽  
Vol 11 (3) ◽  
pp. 914-927 ◽  
Author(s):  
David W. Peterson ◽  
Peter B. Reich
2002 ◽  
Vol 11 (1) ◽  
pp. 1 ◽  
Author(s):  
Jolie Pollet ◽  
Philip N. Omi

Fire exclusion policies have affected stand structure and wildfire hazard in north American ponderosa pine forests. Wildfires are becoming more severe in stands where trees are densely stocked with shade-tolerant understory trees. Although forest managers have been employing fuel treatment techniques to reduce wildfire hazard for decades, little scientific evidence documents the success of treatments in reducing fire severity. Our research quantitatively examined fire effects in treated and untreated stands in western United States national forests. Four ponderosa pine sites in Montana, Washington, California and Arizona were selected for study. Fuel treatments studied include: prescribed fire only, whole-tree thinning, and thinning followed by prescribed fire. On-the-ground fire effects were measured in adjacent treated and untreated forests. We developed post facto fire severity and stand structure measurement techniques to complete field data collection. We found that crown fire severity was mitigated in stands that had some type of fuel treatment compared to stands without any treatment. At all four of the sites, the fire severity and crown scorch were significantly lower at the treated sites. Results from this research indicate that fuel treatments, which remove small diameter trees, may be beneficial for reducing crown fire hazard in ponderosa pine sites.


2014 ◽  
Vol 44 (4) ◽  
pp. 350-364 ◽  
Author(s):  
Melissa Thomas-Van Gundy ◽  
James Rentch ◽  
Mary Beth Adams ◽  
Walter Carson

Current forests developed under conditions different from original forests, with higher deer densities, reduced fire frequency, denser canopies, and smaller canopy gaps. These alterations have led to understories dominated by species simultaneously browse tolerant, shade tolerant, and fire sensitive leading to difficulties in the regeneration of oak species (Quercus spp.) in some areas. We evaluated how three key processes — understory fire, canopy gaps, and browsing — influenced tree species in east central West Virginia. We were particularly interested in the response of oak species because they are the dominant overstory species and of maple species (Acer spp.), black birch (Betula lenta L.), and yellow-poplar (Liriodendron tulipifera L.) as these are likely to replace the current forest. Single-process effects were significant and significant interactions among processes were numerous. In general, fire caused significant reductions of seedlings and saplings of red maple (Acer rubrum L.) and striped maple (Acer pensylvanicum L.) and increased the seedlings of black birch and yellow-poplar. Canopy gaps increased the abundance of black birch and yellow-poplar seedlings and saplings. Gaps and fire together caused an increase in the relative abundance of yellow-poplar. Excluding browsers and creating canopy gaps together nearly doubled oak sapling importance values versus either treatment alone; however, oak importance values remained low. Given the significant interactions of browse control with the other two processes, browse control should be considered when planning oak regeneration treatments such as canopy gaps or prescribed fire.


2020 ◽  
Vol 17 (18) ◽  
pp. 4509-4522
Author(s):  
Matthew L. Trumper ◽  
Daniel Griffin ◽  
Sarah E. Hobbie ◽  
Ian M. Howard ◽  
David M. Nelson ◽  
...  

Abstract. Fire frequency exerts a fundamental control on productivity and nutrient cycling in savanna ecosystems. Individual fires often increase short-term nitrogen (N) availability to plants, but repeated burning causes ecosystem N losses and can ultimately decrease soil organic matter and N availability. However, these effects remain poorly understood due to limited long-term biogeochemical data. Here, we evaluate how fire frequency and changing vegetation composition influenced wood stable N isotopes (δ15N) across space and time at one of the longest running prescribed burn experiments in the world (established in 1964). We developed multiple δ15N records across a burn frequency gradient from precisely dated Quercus macrocarpa tree rings in an oak savanna at Cedar Creek Ecosystem Science Reserve, Minnesota, USA. Sixteen trees were sampled across four treatment stands that varied with respect to the temporal onset of burning and burn frequency but were consistent in overstory species representation, soil characteristics, and topography. Burn frequency ranged from an unburned control stand to a high-fire-frequency stand that had burned in 4 of every 5 years during the past 55 years. Because N stocks and net N mineralization rates are currently lowest in frequently burned stands, we hypothesized that wood δ15N trajectories would decline through time in all burned stands, but at a rate proportional to the fire frequency. We found that wood δ15N records within each stand were remarkably coherent in their mean state and trend through time. A gradual decline in wood δ15N occurred in the mid-20th century in the no-, low-, and medium-fire stands, whereas there was no trend in the high-fire stand. The decline in the three stands did not systematically coincide with the onset of prescribed burning. Thus, we found limited evidence for variation in wood δ15N that could be attributed directly to long-term fire frequency in this prescribed burn experiment in temperate oak savanna. Our wood δ15N results may instead reflect decadal-scale changes in vegetation composition and abundance due to early- to mid-20th-century fire suppression.


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