Fire history and the structure and dynamics of a mixed conifer forest landscape in the northern Sierra Nevada, Lake Tahoe Basin, California, USA

Beaty, Robert M.; Taylor, Alan H.

doi:10.1016/j.foreco.2007.09.044

Cited by 124 publications

(74 citation statements)

References 62 publications

(107 reference statements)

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“…Because our understanding of fire history in aspen-conifer forests is still developing we have a limited historical context for knowing how current fire cycles compare to the past (Baker 2009). However, studies of fire history in the subalpine and boreal forests of western North America, suggest that both climate conditions (Beaty and Taylor 2008) and fire suppression by humans (Gallant et al 2003, Van Wagner et al 2006) can lengthen fire rotations in the forest of western North America (Strand et al 2009). If this is the case, our data suggest that the aspen-fir facilitation results in antagonistic interactions for aspen that intensify as succession cycles lengthen causing strong compositional shifts toward conifer dominance mediated by fir regeneration success, aspen regeneration failure (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Increasingly, anthropogenic influences are changing the timing and behavior of fire in the forest ecosystems of western North America (Brown and Smith 2000), which is likely to have important feedbacks on facilitative and competitive interactions. Emerging evidence suggests that both climate conditions (Beaty and Taylor 2008) and fire suppression by humans (Gallant et al 2003) can lengthen fire rotations in subalpine forests. Early successional species may be particularly vulnerable to altered disturbance cycles and their response is likely to have cascading effects on forest community development (Reyes et al 2010).…”

Section: Introductionmentioning

confidence: 99%

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Facilitation drives mortality patterns along succession gradients of aspen‐conifer forests

Calder

Clair

2012

Ecosphere

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Citation: Calder, W. J., and S. B. St. Clair. 2012. Facilitation drives mortality patterns along succession gradients of aspenconifer forests. Ecosphere 3(6):57. http://dx.doi.org/10.1890/ES12-00119.1Abstract. While it is well established that facilitation and competition are important structuring forces in plant communities, a clear understanding of the interactions between them and how they change through the life stages of plants and affect long-term plant community development is lacking. We have observed that conifer seedlings are rarely found growing in meadows but readily establish under adjacent aspen stands, particularly at the base of aspen trees, creating the potential for antagonistic interactions in later life stages. To examine these relationships and their potential consequences on forest community development, we characterized patterns of establishment, regeneration, and overstory mortality of aspen (Populus tremuloides) and subalpine fir (Abies lasiocarpa) along a stand composition gradient (aspen dominant ! mixed ! conifer dominant) that develops in seral aspen forests. We found strong stand effects on the establishment of both aspen and subalpine fir regeneration. Aspen regenerated into meadows from the forest boundary, reached peak densities underneath aspen stands, and decreased significantly in mixed and conifer dominated stands. In contrast, subalpine fir seedlings failed to regenerate in meadows, but established readily underneath aspen, mixed and conifer stands. Within stands, establishing subalpine fir seedlings were strongly aggregated around mature aspen trees, which increased the proximity of the two species 2-10 fold depending on subalpine fir age class and stand type. Both stand type and increased proximity of overstory aspen and fir trees drove mortality patterns of the two species in opposite directions. Overstory aspen mortality increased sharply along the stand composition gradient: aspen (7%), mixed (17%), conifer (49%), while subalpine fir wasn't significantly influenced by stand type. Proximity of overstory aspen and subalpine fir, was associated with increased (23) aspen mortality under all stand conditions but increased subalpine fir survival resulting in high aspen:fir mortality ratios that likely accelerate successional shifts toward conifer dominance. Our data suggest that environmental conditions that promote facilitator mortality may compromise the ability of facilitation-dependent forests to regenerate following disturbance. Maintenance of natural disturbance regimes appears to be critical in striking an ecological balance between facilitation and competition that promotes sustainability in succession-driven plant communities.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Facilitation drives mortality patterns along succession gradients of aspen‐conifer forests

Calder

Clair

2012

Ecosphere

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“…Following a disturbance event (e.g., a stand-replacing fire), aspen colonize the area, either by seed or through sprouting from existing roots (Mueggler, 1985). Numerous studies have established that changes in fire regimes from the early twentieth century onward have clearly altered forest succession (Beaty, et al, 2008;Kaye, et al, 2003;Kurzel, et al, 2007), and favor coniferdominated landscapes, especially among current aspen/mixed conifer stands (Smith and Smith, 2005;Minnich, et al, 2000).…”

Section: Conifer Encroachmentmentioning

confidence: 99%

Aspen mortality in the Colorado and southern Wyoming Rocky Mountains: Extent, severity, and causal factors

Dudley

Burns

Jacobi

2015

Forest Ecology and Management

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We established 573 random roadside survey plots in stands that contained at least 50% aspen cover type. From these random plots, we found average standing aspen tree mortality ranged from 3.3 to 23.7 % on the four national forests and 11% on the east side of the continental divide and 4 % on the west side. Low elevation stands had significantly less mortality (7%) vs. high elevation (8%). The roadside plot data suggests that Colorado's aspen on these four national forests overall were healthy; mortality rates iii among aspen were fairly low (~3 -8%) among all stems, and average percent live crown among adults was high (~85 -90%), in spite of nearly ubiquitous presence of disease (~97 -99%) and high incidence of insect damage (~50 -75%).We also established 98 aspen stand assessment plots with half of the plots in damaged stands, as defined by U.S.D.A. Forest Service aerial detection surveys (ADS), and half in healthy aspen stands. Damaged stands were defined as those stands with (1) thinning crowns among at least 25% of adult aspen, (2) stands with moderate (<50% of stems) levels of overstory mortality, or (3) stands with high (>50% of stems) levels of overstory mortality. Healthy aspen stands were defined as having (1) a maximum mortality rate of 5 -7% among all aspen, and/or (2) more than 75% of adult aspen with full crowns.Adult aspen in damaged stands tended to be less vigorous, based a health score index from 1 to 5, with higher scores indicating less healthy conditions (where 1=0-25% damage; 2 = 25-50% damage; 3 = >50% damage; 4 = recent dead; 5 = >5 years dead).Health scores averaged 1.7 in healthy stands, compared to 2.3 in damaged stands.Saplings in damaged stands tended to be healthier with a score of 1.7, compared to 2.2 in healthy stands. Further, there was no difference in the proportion live or total numbers of saplings per hectare between healthy and damaged stands. The prevalence of damaging organisms, such as Cytospora canker (20% in damaged, 13% in healthy), wood-boring insects (27% in damaged, 10% in healthy), and aspen bark beetles (16% in damaged, 7% in healthy) was considerably greater among damaged stands. Site conditions also influenced the prevalence of some of these damage agents: bark beetles were most common among stands at low elevations (18%, compared to 11% and 6% at moderate iv and high elevations, respectively); Cytospora canker was most common among stands on south-or west-facing aspects (20% and 19%, respectively); both aspen bark beetles and Cytospora canker were also most common among stands in the southernmost section of the survey area, the Pike-San Isabel national forest (41% and 36%). There was no difference in the severity of canker or decay fungal infection between healthy and damaged stands. Cytospora canker infestations were more severe on the Medicine Bow NF compared to the other three national forests, and Marssonina foliar blight infection appeared to be most severe on slope summits, concave sites, and sites with either no to low percent slope or moderately steep sl...

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“…Under these conditions forests were largely resistant to extensive, high-intensity fire (Brown et al 2008), and were generally resilient to other disturbances and stressors (e.g., insects, disease, and drought) (Fulé 2008). However, there is evidence from some forest types that historical fires did occur at higher intensities as well, resulting in discrete patches of high tree mortality throughout the landscape (Beaty and Taylor 2001, Hessburg et al 2007, Beaty and Taylor 2008; such patterns continue today where wildfires have been managed for resource benefit .…”

Section: Introductionmentioning

confidence: 99%

Impacts of fire exclusion and recent managed fire on forest structure in old growth Sierra Nevada mixed-conifer forests

2011

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Abstract. We re-sampled areas included in an unbiased 1911 timber inventory conducted by the U.S.Forest Service over a 4000 ha study area. Over half of the re-sampled area burned in relatively recent management-and lightning-ignited fires. This allowed for comparisons of both areas that have experienced recent fire and areas with no recent fire, to the same areas historically based on early forest inventories. Our results indicate substantially altered present forest conditions, relative to the 1911 data, and can largely be attributed to the disruption of the key ecosystem process for these forests, fire. For areas that burned recently there was a noticeable difference in forest structure based on fire severity. Current tree density and canopy cover in areas burned recently with moderate severity did not differ from 1911 estimates, while areas that burned recently with low severity or were unburned had higher tree density and canopy cover relative to the 1911 estimates. This emphasizes an important distinction with regard to using fire to restore forests, resting primarily on whether fires kill trees in the lower and intermediate canopy strata. Our results also demonstrate nearly a doubling of live tree carbon stocks in the present forest compared to the historical forest. The findings presented here can be used by managers and ecologists interested in restoring Sierra Nevada mixed conifer systems.

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Fire history and the structure and dynamics of a mixed conifer forest landscape in the northern Sierra Nevada, Lake Tahoe Basin, California, USA

Cited by 124 publications

References 62 publications

Facilitation drives mortality patterns along succession gradients of aspen‐conifer forests

Facilitation drives mortality patterns along succession gradients of aspen‐conifer forests

Aspen mortality in the Colorado and southern Wyoming Rocky Mountains: Extent, severity, and causal factors

Impacts of fire exclusion and recent managed fire on forest structure in old growth Sierra Nevada mixed-conifer forests

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