Long-Term Effects of Burn Season and Frequency on Ponderosa Pine Forest Fuels and Seedlings

Westlind, Douglas J.; Kerns, Becky K.

doi:10.4996/fireecology.130304261

Cited by 14 publications

(13 citation statements)

References 59 publications

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“…Some plant groups were considered more relevant or desirable for certain management goals (e.g., wildlife habitat, forage production), including native perennial bunchgrasses, sedges, and shrubs. Results for exotic grasses, notably cheatgrass, are published elsewhere (Kerns and Day ), as are results for tree seedlings (Westlind and Kerns ). We note that there are no warm‐season or native annual grasses in the study area, no exotic shrubs, and too few tree species to analyze for richness (Table ).…”

Section: Methodsmentioning

confidence: 89%

“…Very frequent burning may also be too low severity to promote seed germination and short‐lived species establishment. Indeed, the reburns in this study were often difficult to conduct and carry due to fine fuel limitations (Westlind and Kerns ). On the other hand, bare soil cover increased and O horizon depth was reduced with fall reburning, as was overstory tree cover, suggesting that burns were of sufficient severity to expose new mineral soil and increase light availability.…”

Section: Discussionmentioning

confidence: 99%

“…). Ironically, 5‐yr burning has not reduced woody fuels due to notable overstory mortality that actually increased fuels, although ground fuels (litter and diff) have been reduced (Westlind and Kerns ). While we suggest that simply conducting prescribed fires more frequently may not increase perennial native plant abundance and diversity, we acknowledge our burns were still conducted under low‐temperature and high‐humidity conditions that still may not allow fire to do as much work (North et al.…”

Section: Discussionmentioning

confidence: 99%

“…). Westlind and Kerns () suggest that an intermediate fire frequency closer to 10 yr in these types of ponderosa pine forests may offer better outcomes related to fuel reduction goals, and this may hold for some plant goals as well. Some suggest wildfires managed for ecological or other resource goals may provide a viable option as well as recognized tradeoffs (Barros et al.…”

Section: Discussionmentioning

confidence: 99%

“…Prescribed burns were maintained by handcarried drip torches using a multiple-strip headfire pattern maintaining a 60 cm flame length if possible. Westlind and Kerns (2017) noted that there was a difference in air temperature during the burns between spring and fall, with the mean spring temperatures estimated to be 6.22°C higher than fall temperatures. There were no differences between spring and fall burns for mean relative humidity, wind speed, or flame length.…”

Section: Experimental Designmentioning

confidence: 99%

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Prescribed fire regimes subtly alter ponderosa pine forest plant community structure

Kerns

Day

2018

Ecosphere

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Prescribed fire is an active management tool used to address wildfire hazard and ecological concerns associated with fire exclusion and suppression over the past century. Despite widespread application in the United States, there is considerable inconsistency and lack of information regarding the extent to which specific outcomes are achieved and under what prescribed fire regimes, particularly in regard to ecological goals related to plant community structure. We quantify differences and patterns in plant functional group abundance, species richness and diversity, and other key forest components through time from a unique long‐term (15‐yr) experiment within the Malheur National Forest of Oregon. Treatments included five fire regimes: fall and spring 5‐yr burning, fall and spring single burn, and no burning. Original burns were conducted in the fall of 1997 and spring of 1998, and plant data were collected every five years starting in 2002. Many perennial plant group responses were neutral, subtle, and ephemeral. Total cover increased marginally in response to the first burn, but this response disappeared within a decade. Three 5‐yr reburns did not increase or decrease total plant cover, richness, or diversity. Some plant groups with fire resistant and resilient traits, such as annual forbs, exotic forbs, open bunchgrasses, and rhizomatous and resprouting perennials, showed some short‐term positive responses to initial burning and 1–2 reburns, but not 3. The moderately more severe fall burns generally impacted plant responses more than spring burning, but many patterns were legacies from the original higher severity burns. Burn frequency was more important for less severe spring burning. Overall, we document that most native perennial plant functional groups were able to resist or recover from burning and reburning, but did not necessarily strongly respond. This may be due to the importance of other overriding forcing factors and ecosystem inertia not easily overcome by very low‐severity prescribed burns. Results from our study are important for practitioners using prescribed fire to achieve biodiversity, conservation, and habitat goals that hinge on a vigorous native perennial plant response, as such outcomes are not certain even with frequent burn regimes.

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Section: Methodsmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Experimental Designmentioning

confidence: 99%

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Prescribed fire regimes subtly alter ponderosa pine forest plant community structure

Kerns

Day

2018

Ecosphere

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Long‐term frequent fire and cattle grazing alter dry forest understory vegetation

Kerns,

Day

2024

Ecological Applications

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Understanding fire and large herbivore interactions in interior western forests is critical, owing to the extensive and widespread co‐occurrence of these two disturbance types and multiple present and future implications for forest resilience, conservation and restoration. However, manipulative studies focused on interactions and outcomes associated with these two disturbances are rare in forested rangelands. We investigated understory vegetation response to 5‐year spring and fall prescribed fire and domestic cattle grazing exclusion in ponderosa pine stands and reported long‐term responses, almost two decades after the first entry fires. In fall burn areas open to cattle grazing, total understory cover prior to utilization was about 12% lower compared with fall burn areas where cattle were experimentally excluded. This response was not strongly driven by a particular palatable or unpalatable plant functional group. Fire and grazing are likely interacting in a numerically mediated process, as we found little evidence to support a functionally moderated pathway. Post‐fire green‐up may equalize forage to a certain extent and concentrate herbivores in the smaller burned areas within pastures, constraining a positive understory response to burning. Fall fire and grazing also increased annual forbs and resprouting shrubs. The effects of spring burning were relatively minor, and we found no interaction with grazing. The nonnative annual grass Bromus tectorum (cheatgrass) remains a problematic invader linked to fall burning but not grazing in stands that had higher propagule pressure when the experiment was initiated. At these sites, exotic grass was a major component of the vegetation by 2015, and invasion was also increasing in spring burn and unburned areas. Information from our study suggests that frequent fall fires and cattle grazing combined may reduce understory resilience in similar dry ponderosa pine forests. Consideration of longer fire return intervals, resting areas after fire, virtual fencing, or burning entire pastures may help to mitigate the effects noted in this study.

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Post-fire Regeneration in Yellow Pine and Mixed Conifer Forests of California: Challenges, Tools and Applications for Fire-Adapted Forests

Williams

Long

Meyer

et al. 2021

Pines and Their Mixed Forest Ecosystems in the Mediterranean Basin

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Long-Term Effects of Burn Season and Frequency on Ponderosa Pine Forest Fuels and Seedlings

Cited by 14 publications

References 59 publications

Prescribed fire regimes subtly alter ponderosa pine forest plant community structure

Prescribed fire regimes subtly alter ponderosa pine forest plant community structure

Long‐term frequent fire and cattle grazing alter dry forest understory vegetation

Post-fire Regeneration in Yellow Pine and Mixed Conifer Forests of California: Challenges, Tools and Applications for Fire-Adapted Forests

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