Post-1935 changes in forest vegetation of Grand Canyon National Park, Arizona, USA: Part 1 – ponderosa pine forest

Over a century of fire exclusion in frequent-fire ponderosa pine and dry mixed conifer forests has resulted in increased tree densities, heavy surface fuel accumulations and an increase in late successional, fire-intolerant trees. Grand Canyon National Park uses prescribed fires and wildfires to reduce fire hazard and restore ecosystem processes. Research is needed to determine post-fire vegetation response thus enabling future forest succession predictions. Our study focussed on the effects of burn entry and burn severity on species composition and regeneration in two forest types: ponderosa pine with white fir encroachment and dry mixed conifer. We found no difference in tree composition and structure in a single, low-severity burn compared with unburned areas in the white fir encroachment forest type. We found no white fir seedlings or saplings in a second-entry, low-severity burn in the white fir encroachment forest type. Second-entry burns were effective in reducing white fir densities in the white fir encroachment forest type. There was significant aspen regeneration following high-severity fire in the dry mixed conifer forest type. This research suggests that repeated entries and an increase in burn severity may be necessary for prescribed fire or wildfire to be effective in meeting management objectives.

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Fire history in ponderosa pine landscapes of Grand Canyon National Park: is it reliable enough for management and restoration?

International Journal of Wildland Fire ◽

10.1071/wf06047 ◽

2006 ◽

Vol 15 (3) ◽

pp. 433 ◽

Cited By ~ 16

Author(s):

William L. Baker

Keyword(s):

Ponderosa Pine ◽

National Park ◽

Fire History ◽

Fire Regime ◽

Grand Canyon ◽

Fire Risk ◽

Fire Regimes ◽

Grand Canyon National Park ◽

High Severity ◽

The Impact

Reconstructing fire regimes of the past can provide a valuable frame of reference for understanding the impact of human land uses on contemporary fire and forest structure, but methods for reconstructing past fire regimes are under re-evaluation. In the present article, a common method of characterizing surface fire regimes, using composite fire intervals from fire scars, is shown to significantly underestimate the length of the fire rotation and population mean fire interval in Grand Canyon landscapes where these parameters are known. Also, the evidence and interpretation that past high-severity fire was uncommon in ponderosa pine landscapes in Grand Canyon National Park are challenged. Together, these two concerns mean that an alternative characterization of the fire regime, which has very different implications, cannot be excluded. Management aimed at lowering fire risk, as a means of restoration, does not presently have a sound scientific basis, if it uses the composite fire interval as a measure of the fire regime or is based on fire history research that lacks adequate analysis of past high-severity fire.

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Post-1935 changes in forest vegetation of Grand Canyon National Park, Arizona, USA: Part 2—Mixed conifer, spruce-fir, and quaking aspen forests

Forest Ecology and Management ◽

10.1016/j.foreco.2010.09.015 ◽

2011 ◽

Vol 261 (3) ◽

pp. 326-341 ◽

Cited By ~ 17

Author(s):

John L. Vankat

Keyword(s):

National Park ◽

Grand Canyon ◽

Forest Vegetation ◽

Quaking Aspen ◽

Mixed Conifer ◽

Grand Canyon National Park

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Variability of historical forest structure and fire across ponderosa pine landscapes of the Coconino Plateau and south rim of Grand Canyon National Park, Arizona, USA

Landscape Ecology ◽

10.1007/s10980-012-9835-z ◽

2012 ◽

Vol 28 (2) ◽

pp. 297-310 ◽

Cited By ~ 16

Author(s):

Mark A. Williams ◽

William L. Baker

Keyword(s):

Forest Structure ◽

Ponderosa Pine ◽

National Park ◽

Grand Canyon ◽

Grand Canyon National Park ◽

Historical Forest

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Reversal of human-induced vegetation changes in Sequoia National Park, California

Canadian Journal of Forest Research ◽

10.1139/x99-007 ◽

1999 ◽

Vol 29 (4) ◽

pp. 399-412 ◽

Cited By ~ 7

Author(s):

D Graham Roy ◽

John L Vankat

Keyword(s):

Ponderosa Pine ◽

National Park ◽

Prescribed Burning ◽

Pine Forest ◽

Tree Density ◽

Permanent Plots ◽

Vegetation Changes ◽

Sequoia National Park ◽

Giant Sequoia ◽

Ponderosa Pine Forest

We resampled 76 permanent plots that had been established in the woodlands and forests of Sequoia National Park in 1969. Our objectives were to describe vegetation changes in the tree and shrub layers and determine the effects of prescribed burning that began in the 1960s. We compared changes in species importance and tree size class distributions between sample dates and between burned and unburned plots. Species composition had remained similar in all nine vegetation types sampled except in the ponderosa pine forest where Pinus ponderosa Dougl. ex P. & C. Laws. decreased in importance from 28 to 15% and Abies concolor (Gord. & Glend.) Lindl. increased from 18 to 31%. Structural changes were more common, as tree density decreased in the blue oak woodland (19%), and live oak woodlands (15%), as well as in ponderosa pine forest (41%), white fir forest (5%), giant sequoia groves (39%), and red fir forest (24%). Decreases in density were greater in burned plots but occurred in unburned plots as well, indicating that prescribed fire and self-thinning contributed to decreases in density. Tree density was unchanged in the lodgepole and subalpine forests, but increased in the Jeffrey pine forest (58%). The decreases in tree density represent a reversal of earlier trends.

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