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

2019 ◽  
Vol 28 (7) ◽  
pp. 495 ◽  
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.

Tree mortality from fire and bark beetles following early and late season prescribed fires in a Sierra Nevada mixed-conifer forest

2006 ◽  
Vol 232 (1-3) ◽  
pp. 36-45 ◽  
Author(s):  
Dylan W. Schwilk ◽  
Eric E. Knapp ◽  
Scott M. Ferrenberg ◽  
Jon E. Keeley ◽  
Anthony C. Caprio
Keyword(s):  
Sierra Nevada ◽  
Bark Beetles ◽  
Tree Mortality ◽  
Prescribed Fires ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Late Season ◽  
Mixed Conifer Forest

scholarly journals Historical and current landscape-scale ponderosa pine and mixed conifer forest structure in the Southern Sierra Nevada

Ecosphere ◽  
2015 ◽  
Vol 6 (5) ◽  
pp. art79 ◽  
Author(s):  
Scott L. Stephens ◽  
Jamie M. Lydersen ◽  
Brandon M. Collins ◽  
Danny L. Fry ◽  
Marc D. Meyer
Keyword(s):  
Sierra Nevada ◽  
Forest Structure ◽  
Ponderosa Pine ◽  
Landscape Scale ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Mixed Conifer Forest

Tree mortality patterns following prescribed fires in a mixed conifer forest

2006 ◽  
Vol 36 (12) ◽  
pp. 3222-3238 ◽  
Author(s):  
Leda Kobziar ◽  
Jason Moghaddas ◽  
Scott L Stephens
Keyword(s):  
Sierra Nevada ◽  
Ponderosa Pine ◽  
Tree Mortality ◽  
Fire Behavior ◽  
Mortality Rates ◽  
Fire Intensity ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Mixed Conifer Forest ◽  
White Fir

During the late fall of 2002 we administered three burns in mixed conifer forest sites in the north-central Sierra Nevada. Eight months later we measured fire-induced injury and mortality in 1300 trees. Using logistic regression, an array of crown scorch, stem damage, fuels, and fire-behavior variables were examined for their influence on tree mortality. In Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), white fir (Abies concolor (Gord. & Glend.) Lindl.), and incense cedar (Calocedrus decurrens (Torr.) Florin), smaller trees with greater total crown damage had higher mortality rates. Smaller stem diameters and denser canopies predicted mortality best in ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws). Duff consumption and bark char severity increased model discrimination for white fir and incense cedar and California black oak (Quercus kelloggii Newberry), respectively. In tanoak (Lithocarpus densiflorus (Hook. & Arn.) Rehd.), greater total crown damage in shorter trees resulted in higher mortality rates. Along with tree diameter and consumption of large (>7.6 cm diameter at breast height, DBH) rotten downed woody debris, fire intensity was a significant predictor of overall tree mortality for all species. Mortality patterns for white fir in relation to crown damage were similar among sites, while those for incense cedar were not, which suggests that species in replicated sites responded differently to similar burns. Our results demonstrate actual fire-behavior data incorporated into mortality models, and can be used to design prescribed burns for targeted reduction of tree density in mixed conifer forests.

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

2016 ◽  
Vol 46 (5) ◽  
pp. 745-752 ◽  
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.

Long-term effects of prescribed fire on mixed conifer forest structure in the Sierra Nevada, California

2011 ◽  
Vol 261 (6) ◽  
pp. 989-994 ◽  
Author(s):  
Phillip J. van Mantgem ◽  
Nathan L. Stephenson ◽  
Eric Knapp ◽  
John Battles ◽  
Jon E. Keeley
Keyword(s):  
Sierra Nevada ◽  
Prescribed Fire ◽  
Forest Structure ◽  
Conifer Forest ◽  
Long Term Effects ◽  
Mixed Conifer ◽  
Mixed Conifer Forest

Initial tree mortality and insect and pathogen response to fire and thinning restoration treatments in an old-growth mixed-conifer forest of the Sierra Nevada, California

2008 ◽  
Vol 38 (12) ◽  
pp. 3011-3020 ◽  
Author(s):  
Patricia E. Maloney ◽  
Thomas F. Smith ◽  
Camille E. Jensen ◽  
Jim Innes ◽  
David M. Rizzo ◽  
...  
Keyword(s):  
Sierra Nevada ◽  
Forest Restoration ◽  
Tree Mortality ◽  
Large Diameter ◽  
Heterobasidion Annosum ◽  
White Pine Blister Rust ◽  
Mixed Conifer ◽  
White Pine ◽  
Dwarf Mistletoe ◽  
Blister Rust

Fire and thinning restoration treatments in fire-suppressed forests often damage or stress leave trees, altering pathogen and insect affects. We compared types of insect- and pathogen-mediated mortality on mixed-conifer trees 3 years after treatment. The number of bark beetle attacked trees was greater in burn treatments compared with no-burn treatments, and in some cases, larger pine trees were preferentially attacked. Restoration treatments are not expected to change the trajectory of spread and intensification of dwarf mistletoe. Thinning treatments may have provided a sanitation effect in which large leave trees have lower levels of dwarf mistletoe. Although thinning treatments are known to exacerbate root disease, <12% of cut stumps were infected with root pathogens ( Armillaria gallica and Heterobasidion annosum ). Treatments increased Ribes (alternate host for white pine blister rust) frequency and abundance, which may have very localized impacts on white pine blister rust dynamics. In some instances, fire, insects, and pathogens appear to conflict with forest restoration goals by reducing the percentage of pine and producing proportionally higher rates of tree mortality in large-diameter size classes. To better understand the long-term effects of restoration treatments on pathogens and insects, continued monitoring over the course of varying climatic conditions will be needed.

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