Natural regeneration responses to thinning and burning treatments in ponderosa pine forests and implications for restoration

AbstractUnderstanding naturally occurring pine regeneration dynamics in response to thinning and burning treatments is necessary not only to measure the longevity of the restoration or fuels treatment, but also to assess how well regeneration meets forest sustainability guidelines and whether natural regeneration is sufficient for maintaining a sustainable forest structure and composition. A synthesis review was carried out on the effects of mechanical thinning and prescribed burn treatments on natural pine regeneration response in frequent-fire ponderosa pine forests across the western United States. The focus was on site-specific variability in pine regeneration dynamics, temporal trends in regeneration presence and abundance, and response to treatment as described in the current literature using 29 studies that met our evidence-based review protocols. Data showed that the effects of thinning and burning treatments on regeneration depended on time since treatment. Mechanical thinning, prescribed burning, and thinning plus burn treatments all increased seedling density, but there was high variability among sites and studies. There were mixed results in the short-term (< 10 years) with both increasing and decreasing regeneration, and a general increase in regeneration 11 − 20 years post-treatment. Some long-term studies (> 20 years) concluded that stands can return to pre-treatment densities in terms of total trees per hectare and forest floor duff levels when there are no maintenance treatments applied. Several studies showed the average ponderosa pine seedling presence, survival and growth found in today’s forests to be at a high density; this combined with missed fire cycles could contribute to future fire risk and reduce the efficacy of maintaining fuel reduction goals.

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Thinning and Burning Effects on Long-Term Litter Accumulation and Function in Young Ponderosa Pine Forests

Forest Science ◽

10.1093/forsci/fxaa018 ◽

2020 ◽

Vol 66 (6) ◽

pp. 761-769

Author(s):

Matt Busse ◽

Ross Gerrard

Keyword(s):

Ponderosa Pine ◽

Forest Floor ◽

Prescribed Burning ◽

Mineral Soil ◽

Pine Forests ◽

Organic Layer ◽

Litter Accumulation ◽

Ponderosa Pine Forests ◽

Essential Components

Abstract We measured forest-floor accumulation in ponderosa pine forests of central Oregon and asked whether selected ecological functions of the organic layer were altered by thinning and repeated burning. Experimental treatments included three thinning methods applied in 1989 (stem only, whole tree, no thin—control) in factorial combination with prescribed burning (spring 1991 and repeated in 2002; no burn—control). Forest-floor depth and mass were measured every 4–6 years from 1991 to 2015. Without fire, there was little temporal change in depth or mass for thinned (270 trees ha−1) and control (560–615 trees ha−1) treatments, indicating balanced litterfall and decay rates across these stand densities. Each burn consumed 50–70 percent of the forest floor, yet unlike thinning, postfire accumulation rates were fairly rapid, with forest-floor depth matching preburn levels within 15–20 years. Few differences in forest-floor function (litter decay, carbon storage, physical barrier restricting plant emergence, erosion protection) resulted from thinning or burning after 25 years. An exception was the loss of approximately 300 kg N ha−1 because of repeated burning, or approximately 13 percent of the total site N. This study documents long-term forest-floor development and suggests that common silvicultural practices pose few risks to organic layer functions in these forests. Study Implications: Mechanical thinning and prescribed fire are among the most widespread management practices used to restore forests in the western US to healthy, firewise conditions. We evaluated their effects on the long-term development of litter and duff layers, which serve dual roles as essential components of soil health and as fuel for potential wildfire. Our study showed that thinning and burning provided effective fuel reduction and resulted in no adverse effects to soil quality in dry ponderosa pine forests of central Oregon. Repeated burning reduced the site carbon and nitrogen pools approximately 9–13 percent, which is small compared to C located in tree biomass and N in mineral soil. Litter accumulation after burning was rapid, and we recommend burning on at least a 15–20-year cycle to limit its build-up.

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Influences of thinning, prescribed burning, and wildfire on soil processes and properties in southwestern ponderosa pine forests: A retrospective study

Forest Ecology and Management ◽

10.1016/j.foreco.2006.06.031 ◽

2006 ◽

Vol 234 (1-3) ◽

pp. 123-135 ◽

Cited By ~ 82

Author(s):

Kevin C. Grady ◽

Stephen C. Hart

Keyword(s):

Retrospective Study ◽

Ponderosa Pine ◽

Prescribed Burning ◽

Pine Forests ◽

Soil Processes ◽

Ponderosa Pine Forests

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The Effects of Fire on Understory Vegetation in Ponderosa Pine Forests

The UW National Parks Service Research Station Annual Reports ◽

10.13001/uwnpsrc.1980.2229 ◽

1980 ◽

Vol 4 ◽

pp. 96-97

Author(s):

Jane Bock ◽

Carl Bock

Keyword(s):

Pinus Ponderosa ◽

Ponderosa Pine ◽

Prescribed Burning ◽

Fire Regime ◽

Management Plan ◽

Black Hills ◽

Pine Forests ◽

Natural Phenomenon ◽

Natural Fire ◽

Ponderosa Pine Forests

This was the second year of our study designed to evaluate the nature of vegetation occurring under Pinus ponderosa canopy in Wind Cave National Park and to define the relationship between this vegetation and fire. Fire is known to be a natural phenomenon in ponderosa pine forests (Wright 1978), and to play a major role in determining the position of the pine-grassland ecotone in the Black Hills (Gartner and Thompson 1973). Wind Cave personnel are developing a fire management plan allowing for prescribed burning, in hopes of bringing the park ecosystems back under a "natural" fire regime. Results of our study will help park management predict the effects of such prescribed burning on the ponderosa pine community.

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Natural regeneration in ponderosa pine forests of western Montana /

10.5962/bhl.title.68783 ◽

1970 ◽

Cited By ~ 3

Author(s):

Raymond C. Shearer ◽

Wyman C. Schmidt ◽

Keyword(s):

Ponderosa Pine ◽

Natural Regeneration ◽

Western Montana ◽

Pine Forests ◽

Ponderosa Pine Forests

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Response of antelope bitterbrush to repeated prescribed burning in Central Oregon ponderosa pine forests

Forest Ecology and Management ◽

10.1016/j.foreco.2008.10.026 ◽

2009 ◽

Vol 257 (3) ◽

pp. 904-910 ◽

Cited By ~ 8

Author(s):

Matt D. Busse ◽

Gregg M. Riegel

Keyword(s):

Ponderosa Pine ◽

Prescribed Burning ◽

Pine Forests ◽

Ponderosa Pine Forests

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Developing resilient ponderosa pine forests with mechanical thinning and prescribed fire in central Oregon's pumice region

Canadian Journal of Forest Research ◽

10.1139/x09-044 ◽

2009 ◽

Vol 39 (6) ◽

pp. 1171-1185 ◽

Cited By ~ 10

Author(s):

Matt D. Busse ◽

P.H. Cochran ◽

William E. Hopkins ◽

William H. Johnson ◽

Gregg M. Riegel ◽

...

Keyword(s):

Plant Diversity ◽

Prescribed Fire ◽

Ponderosa Pine ◽

Prescribed Burning ◽

Stand Structure ◽

Forest Vegetation ◽

Pine Forests ◽

Production Plant ◽

Ponderosa Pine Forests ◽

Combined Use

Thinning and prescribed burning are common management practices for reducing fuel buildup in ponderosa pine forests. However, it is not well understood if their combined use is required to lower wildfire risk and to help restore natural ecological function. We compared 16 treatment combinations of thinning, prescribed fire, and slash retention for two decades across a site quality gradient of second-growth pine stands, measuring changes in forest vegetation growth, structure, and composition. Thinning alone doubled the diameter growth increment of ponderosa pine, moderately stimulated shrub production, and resulted in lower tree mortality compared with unthinned plots. In contrast, repeated fire alone did not substantially alter stand structure or increase tree vigor, herbaceous production, or plant diversity. The combined use of thinning and repeated burning reduced shrub cover, yet produced no changes in herbaceous production, plant diversity, stand structure, or tree vigor compared with thin-only treatments. Additional findings identified (1) inconsequential effects of thinning residues on site productivity, (2) the need for multiple entries of prescribed fire if the abatement of shrubs is required, (3) the ineffectiveness of repeated burning to stimulate plant growth, and (4) that the thinning treatment served as an effective surrogate to fire for managing central Oregon forest vegetation.

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