Opportunities for winter prescribed burning in mixed conifer plantations of the Sierra Nevada

Abstract Background Young, planted forests are particularly vulnerable to wildfire. High severity effects in planted forests translate to the loss of previous reforestation investments and the loss of future ecosystem service gains. We conducted prescribed burns in three ~35-year-old mixed conifer plantations that had previously been masticated and thinned during February in order to demonstrate the effectiveness of winter burning, which is not common in the Sierra Nevada, California. Results On average, 59% of fine fuels were consumed and the fires reduced shrub cover by 94%. The average percent of crown volume that was damaged was 25%, with no mortality observed in overstory trees 1 year following the fires. A plot level analysis of the factors of fire effects did not find strong predictors of fuel consumption. Shrub cover was reduced dramatically, regardless of the specific structure that existed in plots. We found a positive relationship between crown damage and the two variables of Pinus ponderosa relative basal area and shrub cover. But these were not particularly strong predictors. An analysis of the weather conditions that have occurred at this site over the past 20 years indicated that there have consistently been opportunities to conduct winter burns. On average, 12 days per winter were feasible for burning using our criteria. Windows of time are short, typically 1 or 2 days, and may occur at any time during the winter season. Conclusions This study demonstrates that winter burning can be an important piece of broader strategies to reduce wildfire severity in the Sierra Nevada. Preparing forest structures so that they can be more feasible to burn and also preparing burn programs so that they can be nimble enough to burn opportunistically during short windows are key strategies. Both small landowners and large agencies may be able to explore winter burning opportunities to reduce wildfire severity.

Download Full-text

Opportunities for winter prescribed burning in mixed conifer plantations of the Sierra Nevada

10.21203/rs.3.rs-423745/v1 ◽

2021 ◽

Author(s):

Robert York ◽

Jacob Levine ◽

Kane Russell ◽

Joseph Restaino

Keyword(s):

Sierra Nevada ◽

Pinus Ponderosa ◽

Prescribed Burning ◽

Winter Season ◽

Basal Area ◽

Weather Conditions ◽

Shrub Cover ◽

Mixed Conifer ◽

Planted Forests ◽

Conifer Plantations

Abstract Background Young, planted forests are particularly vulnerable to wildfire. High severity effects in planted forests translate to the loss of previous reforestation investments and the loss of future ecosystem service gains. We conducted prescribed burns in three ~ 35 year-old mixed conifer plantations during February in order to demonstrate the effectiveness of winter burning, which is not common in the Sierra Nevada, California. Results On average, 59% of fine fuels were consumed and the fires reduced shrub cover by 94%. The average percent of crown volume that was damaged was 25%, with no mortality observed in overstory trees one year following the fires. A plot-level analysis of the factors of fire effects did not find strong predictors of fuel consumption. Shrub cover was reduced dramatically, regardless of the specific structure that existed in plots. We found a positive relationship between crown damage and the two variables of Pinus ponderosa relative basal area and shrub cover. But these were not particularly strong predictors. An analysis of the weather conditions that have occurred at this site over the past 20 years indicated that there has consistently been opportunities to conduct winter burns. Windows of time are short, typically one or two days, and may occur at any time during the winter season. Conclusions This study demonstrates that winter burning can be an important piece of broader strategies to reduce wildfire severity in the Sierra Nevada. Preparing forest structures so that they can be feasible to burn and also preparing burn programs so that they can be nimble enough to burn opportunistically during short windows during the winter are key strategies.

Download Full-text

Heterogeneity in fire severity within early season and late season prescribed burns in a mixed-conifer forest

International Journal of Wildland Fire ◽

10.1071/wf04068 ◽

2006 ◽

Vol 15 (1) ◽

pp. 37 ◽

Cited By ~ 75

Author(s):

Eric E. Knapp ◽

Jon E. Keeley

Keyword(s):

Sierra Nevada ◽

Prescribed Burning ◽

Fire Severity ◽

Basal Area ◽

Conifer Forest ◽

Fuel Loading ◽

Early Season ◽

Late Season ◽

Fuel Loads ◽

In Fire

Structural heterogeneity in forests of the Sierra Nevada was historically produced through variation in fire regimes and local environmental factors. The amount of heterogeneity that prescription burning can achieve might now be more limited owing to high fuel loads and increased fuel continuity. Topography, woody fuel loading, and vegetative composition were quantified in plots within replicated early and late season burn units. Two indices of fire severity were evaluated in the same plots after the burns. Scorch height ranged from 2.8 to 25.4 m in early season plots and 3.1 to 38.5 m in late season plots, whereas percentage of ground surface burned ranged from 24 to 96% in early season plots and from 47 to 100% in late season plots. Scorch height was greatest in areas with steeper slopes, higher basal area of live trees, high percentage of basal area composed of pine, and more small woody fuel. Percentage of area burned was greatest in areas with less bare ground and rock cover (more fuel continuity), steeper slopes, and units burned in the fall (lower fuel moisture). Thus topographic and biotic factors still contribute to the abundant heterogeneity in fire severity with prescribed burning, even under the current high fuel loading conditions. Burning areas with high fuel loads in early season when fuels are moister may lead to patterns of heterogeneity in fire effects that more closely approximate the expected patchiness of historical fires.

Download Full-text

Implementation constraints limit benefits of restoration treatments in mixed-conifer forests

International Journal of Wildland Fire ◽

10.1071/wf18141 ◽

2019 ◽

Vol 28 (7) ◽

pp. 495 ◽

Cited By ~ 6

Author(s):

Jamie M. Lydersen ◽

Brandon M. Collins ◽

Carolyn T. Hunsaker

Keyword(s):

Sierra Nevada ◽

Forest Structure ◽

Forest Restoration ◽

Tree Mortality ◽

Canopy Cover ◽

Basal Area ◽

Severe Drought ◽

Conifer Forest ◽

Mixed Conifer ◽

Trade Offs

Forest restoration treatments seek to increase resilience to wildfire and a changing climate while avoiding negative impacts to the ecosystem. The extent and intensity of treatments are often constrained by operational considerations and concerns over uncertainty in the trade-offs of addressing different management goals. The recent (2012–15) extreme drought in California, USA, resulted in widespread tree mortality, particularly in the southern Sierra Nevada, and provided an opportunity to assess the effects of restoration treatments on forest resilience to drought. We assessed changes in mixed-conifer forest structure following thinning and understorey burning at the Kings River Experimental Watersheds in the southern Sierra Nevada, and how treatments, topography and forest structure related to tree mortality in the recent drought. Treatments had negligible effect on basal area, tree density and canopy cover. Following the recent drought, average basal area mortality within the watersheds ranged from 5 to 26% across riparian areas and 12 to 44% across upland areas, with a range of 0 to 95% across all plots. Tree mortality was not significantly influenced by restoration treatments or topography. Our results suggest that the constraints common to many restoration treatments may limit their ability to mitigate the impacts of severe drought.

Download Full-text

Local testing and calibration of species-specific competition indices in Sierran mixed conifer forests: Application transfer to evolving objectives

Canadian Journal of Forest Research ◽

10.1139/cjfr-2020-0193 ◽

2020 ◽

Author(s):

Mike Premer ◽

Sophan Chhin ◽

Jianwei Zhang

Keyword(s):

Sierra Nevada ◽

Pinus Ponderosa ◽

Growth Patterns ◽

Forest Growth ◽

Conifer Forests ◽

Mixed Conifer ◽

Competitive Response ◽

Mixed Conifer Forests ◽

Species Specific ◽

Competition Indices

Forest growth processes are driven by site productivity and species functional traits, ultimately constrained by cumulative resource demand, and resulting in competitive dynamics across successional forest communities. Historic efforts to quantify competition utilize density metrics or neighborhood crowding indices for yield modeling and reforestation surveys. These methods have expanded to dendroclimatology and restoration applications that commonly assume similar competitive response across species of various functional types. We assessed competitive indices of two focal species (Pinus lambertiana Douglas and Pinus ponderosa Lawson & C. Lawson) in Sierra Nevada mixed conifer forests to estimate stem radial growth under current stand structure. We ranked correlations of basal area increment of the last 10 years (BAI10) separately across 20 competition indices (CIs). Best ranked CIs were used to test the relative influence of competition, tree size, and site variables on BAI10 with linear mixed models. While crown overlap was a common variable in CIs among both species, BAI10 of P. lambertiana was less impacted by intraspecific competition, and P. ponderosa appeared sensitive to all competing stems. Results suggest that local calibration of CIs with crown parameters may aid in interpreting Pinus species growth patterns, and the relative impact of competition on growth is species-specific.

Download Full-text

Twenty-Five-Year Growth and Mortality of Planted Ponderosa Pine Repeatedly Thinned to Different Stand Densities in Northern California

Western Journal of Applied Forestry ◽

10.1093/wjaf/12.4.122 ◽

1997 ◽

Vol 12 (4) ◽

pp. 122-130 ◽

Cited By ~ 8

Author(s):

William W. Oliver

Keyword(s):

Sierra Nevada ◽

Pinus Ponderosa ◽

Ponderosa Pine ◽

Bark Beetles ◽

Basal Area ◽

Stand Density ◽

Northern California ◽

Winter Storms ◽

Randomized Design ◽

Lower Site

Abstract A 20 yr old ponderosa pine (Pinus ponderosa var. ponderosa) plantation on a productive site on the west slope of the Sierra Nevada in northern California was thinned four times over a 25 yr period. Stand densities tested were Stand Density Indexes (SDI) of 73, 128, 183, 238, and 293 (equivalent to 40,70,100,130, and 160 ft2/ac of basal area), replicated three times in a randomized design. Growth was analyzed for each of five 5 yr periods. Periodic annual increments (PAI) of diameter, net basal area, and net total volume differed significantly among periods and, in the earlier periods, among stocking levels. Mortality from winter storms and bark beetles was largely confined to the higher stand densities and in periods 3 and 4 caused PAIs of net basal area and net total volume to decline below that of lower densities. The sensitivity of mortality to stand density suggests a thinning target of SDI 183 (about 100 ft²/ac of basal area) for similar stands—no higher than that recommended for eastside stands of much lower site productivity. This sensitivity coupled with rapid growth suggests that multiple thinnings will be necessary in similar stands to maintain healthy, vigorous trees. West. J. Appl. For. 12(4):122-130.

Download Full-text

Long-term demographic trends in a fire-suppressed mixed-conifer forest

Canadian Journal of Forest Research ◽

10.1139/cjfr-2015-0406 ◽

2016 ◽

Vol 46 (5) ◽

pp. 745-752 ◽

Cited By ~ 9

Author(s):

Carrie R. Levine ◽

Flora Krivak-Tetley ◽

Natalie S. van Doorn ◽

Jolie-Anne S. Ansley ◽

John J. Battles

Keyword(s):

Sierra Nevada ◽

Fire Regime ◽

Fire Suppression ◽

Basal Area ◽

Stand Density ◽

Community Level ◽

Homogeneous State ◽

Conifer Forest ◽

Mixed Conifer ◽

Mixed Conifer Forest

In the western United States, forests are experiencing novel environmental conditions related to a changing climate and a suppression of the historical fire regime. Mixed-conifer forests, considered resilient to disturbance due to their heterogeneity in structure and composition, appear to be shifting to a more homogeneous state, but the timescale of these shifts is not well understood. Our objective was to assess the effects of climate and fire suppression on stand dynamics and demographic rates of an old-growth mixed-conifer forest in the Sierra Nevada. We used a Bayesian hierarchical analysis to quantify species and community rates of recruitment, growth, and mortality. Despite a warming climate, we found that stand density, basal area, and carbon have increased over 56 years. Fir recruitment and growth significantly exceeded the community-level median rates, whereas pine recruitment and growth was significantly lower than the community-level median rates. Shifts in species composition from a well-mixed stand to a more dense fir-dominated stand appear to be driven by low growth and recruitment rates of pines relative to firs. In forests such as these with consistent and relatively low mortality rates, we recommend that restoration and management activities be focused on promoting pine recruitment and growth.

Download Full-text

Influence of Ash Substrate Proximity on Growth and Survival of Planted Mixed-Conifer Seedlings

Western Journal of Applied Forestry ◽

10.1093/wjaf/24.3.117 ◽

2009 ◽

Vol 24 (3) ◽

pp. 117-123 ◽

Cited By ~ 4

Author(s):

Robert A. York ◽

Zachary Thomas ◽

Joseph Restaino

Keyword(s):

Sierra Nevada ◽

Pinus Ponderosa ◽

Ponderosa Pine ◽

Douglas Fir ◽

Mixed Conifer ◽

Basal Diameter ◽

Growth And Survival ◽

Sugar Pine ◽

Giant Sequoia ◽

Height Gain

Abstract To address uncertainty in the performance of seedlings planted in and around postburn substrates, we systematically planted seedlings in the center of, on the edge of, and outside ash substrate footprints following burning of logging residue piles and monitored growth and survival for a decade. Five species (Douglas-fir [Pseudotsuga menziesii], giant sequoia [Sequoiadendron giganteum], incense-cedar [Calocedrus decurrens], sugar pine [Pinus lambertiana], and ponderosa pine [Pinus ponderosa]) were planted in a regenerating mixed-conifer stand in the Sierra Nevada range of California. There was a positive effect of ash substrate proximity on growth that was immediate and persisted for 10 years for every species except incense-cedar. Seedlings planted in the centers of ash substrates consistently outgrew (in both height and basal diameter) seedlings that were planted either on the edges of or outside ash substrates. Douglas-fir had the greatest height gain (+47%), followed by giant sequoia (+28%), sugar pine (+23%), and ponderosa pine (+17%). Basal diameter differences were similar. No effect of ash proximity on survival was detected. Planting seedlings in the centers of ash substrates led to exceptionally larger trees by the time the stand had developed enough to apply a precommercial thin, a relevant milestone for managed stands.

Download Full-text

Damage and mortality patterns in young mixed conifer plantations following prescribed fires in the Sierra Nevada, California

Forest Ecology and Management ◽

10.1016/j.foreco.2016.05.049 ◽

2016 ◽

Vol 376 ◽

pp. 193-204 ◽

Cited By ~ 6

Author(s):

Robin S. Bellows ◽

Ariel C. Thomson ◽

Kate J. Helmstedt ◽

Robert A. York ◽

Matthew D. Potts

Keyword(s):

Sierra Nevada ◽

Prescribed Fires ◽

Mixed Conifer ◽

Conifer Plantations

Download Full-text

A Comparison of Chain Saws, Brushcutters, and Machetes in Thinning a Young Conifer Plantation in the Sierra Nevada

Western Journal of Applied Forestry ◽

10.1093/wjaf/4.2.60 ◽

1989 ◽

Vol 4 (2) ◽

pp. 60-62

Author(s):

Mark S. Jamnick

Keyword(s):

Sierra Nevada ◽

Tree Size ◽

The Other ◽

Mixed Conifer ◽

Production Rates ◽

Conifer Plantation ◽

Significant Difference ◽

Conifer Plantations

Abstract Chain saws, power brushcutters, and machetes were used in thinning an 8-year-old, 14.5 ac mixed conifer plantation in the Sierra Nevada. A comparison of production rates indicated no significant difference between chainsaws and machetes, with brushcutter production rates significantly lower than the other two tools. Differences in production rates were not attributable to tree size or number of trees per acre. Inefficiency of brushcutters was attributable to greater maintenance and downtime as compared to the other two tools. Further comparisons of these tools could be useful in determining the least expensive method of conducting precommercial thinnings in young mixed conifer plantations. West. J. Appl. For. 4(2):60-62, April 1989.

Download Full-text