Anthropogenic and natural disturbance and patterns of mortality in a mixed conifer forest in California

1994 ◽  
Vol 24 (6) ◽  
pp. 1149-1159 ◽  
Author(s):  
Melissa Savage
Keyword(s):  
Forest Ecosystems ◽  
Stand Structure ◽  
Fire Suppression ◽  
Stand Density ◽  
Natural Disturbance ◽  
Anthropogenic Influences ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Mixed Conifer Forest

Anthropogenic and natural disturbances have been implicated in recent mortality episodes in montane forests. While the role of natural disturbance in patterning forest ecosystems has been widely explored in recent decades, the agency of human influence is less well understood. In this paper, stand structure analysis is used to characterize patterns of mortality in a montane mixed conifer forest in southern California subject to multiple influences, both anthropogenic and natural, including fire suppression, air pollution, drought, competition, and insect infestation. While it is difficult to separate the contribution of any one of these factors to tree death, because there have been cumulative and synchronous disturbances, successional trends can be identified. Anthropogenic influences appear to abet the effects of natural disturbance in enhancing the shift from early successional pines to species that tolerate stresses such as drought, fire suppression, or competition that result from increased stand density, or a combination of such stresses.

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.

scholarly journals Effects of post-fire management on dead woody fuel dynamics and stand structure in a severely burned mixed-conifer forest, in northeastern Washington State, USA

2020 ◽  
Vol 470-471 ◽  
pp. 118190 ◽  
Author(s):  
Morris C. Johnson ◽  
Maureen C. Kennedy ◽  
Sarah C. Harrison ◽  
Derek Churchill ◽  
James Pass ◽  
...  
Keyword(s):  
Fire Management ◽  
Stand Structure ◽  
Washington State ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Mixed Conifer Forest ◽  
Fuel Dynamics

Impact of fire suppression on a mixed-conifer forest

1979 ◽  
Vol 2 ◽  
pp. 21-33 ◽  
Author(s):  
David J. Parsons ◽  
Steven H. DeBenedetti
Keyword(s):  
Fire Suppression ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Mixed Conifer Forest

Seasonal variation in surface fuel moisture between unthinned and thinned mixed conifer forest, northern California, USA

2012 ◽  
Vol 21 (4) ◽  
pp. 428 ◽  
Author(s):  
Becky L. Estes ◽  
Eric E. Knapp ◽  
Carl N. Skinner ◽  
Fabian C. C. Uzoh
Keyword(s):  
Canopy Cover ◽  
Stand Density ◽  
Fire Risk ◽  
Fuel Moisture ◽  
Northern California ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Mixed Conifer Forest ◽  
Crown Fires ◽  
Stand Thinning

Reducing stand density is often used as a tool for mitigating the risk of high-intensity crown fires. However, concern has been expressed that opening stands might lead to greater drying of surface fuels, contributing to increased fire risk. The objective of this study was to determine whether woody fuel moisture differed between unthinned and thinned mixed-conifer stands. Sections of logs representing the 1000- and 10 000-h fuel sizes were placed at 72 stations within treatment units in the fall (autumn) of 2007. Following snow-melt in 2008, 10-h fuel sticks were added and all fuels were weighed every 1–2 weeks from May until October. Moisture of the 1000- and 10 000-h fuels peaked at the end of May, and then decreased steadily through the season. Moisture of the 10- and 1000-h fuels did not differ between unthinned and thinned stands at any measurement time. The 10 000-h fuel moisture was significantly less in thinned than unthinned stands only in early to mid-May. Overall, even when fuel moisture varied between treatments, differences were small. The long nearly precipitation-free summers in northern California appear to have a much larger effect on fuel moisture than the amount of canopy cover. Fuel moisture differences resulting from stand thinning would therefore not be expected to substantially influence fire behaviour and effects during times of highest fire danger in this environment.

Post-fire epicormic branching in Sierra Nevada Abies concolor (white fir)

2006 ◽  
Vol 15 (1) ◽  
pp. 31 ◽  
Author(s):  
Chad T. Hanson ◽  
Malcolm P. North
Keyword(s):  
Sierra Nevada ◽  
Fire Suppression ◽  
Large Diameter ◽  
Abies Concolor ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Diameter Class ◽  
Mixed Conifer Forest ◽  
White Fir ◽  
Epicormic Branching

In California’s mixed-conifer forest, which historically had a regime of frequent fires, two conifers, Sequoiadendron giganteum and Pseudotsuga menziesii, were previously known to produce epicormic sprouts from branches. We found epicormic branching in a third mixed-conifer species, Abies concolor, 3 and 4 years after a wildfire in the central Sierra Nevada Mountains of California. Sprouting occurred only from the boles. We investigated (1) whether the degree of crown loss and the extent of epicormic branching were independent; and (2) whether epicormic branching differed by tree size. The vertical extent of epicormic foliage increased with increasing severity of crown loss. There was a significantly greater proportion of large diameter-class (>50 cm diameter at breast height [dbh]) trees with epicormic branching than small/medium diameter-class (25–50 cm dbh) trees. These results suggest large diameter Abies concolor may survive high levels of crown loss, aided by crown replacement through epicormic branching, but that reiterative green foliage may not appear for up to 3 years after fire damage. If this response is widespread, it would suggest some ‘dying’ trees logged under current salvage guidelines could survive, and that higher-intensity fire may substantially reduce the density of small post-fire suppression white fir, while retaining many larger overstory trees.

Stand-level spatial dependence in an old-growth Jeffrey pine – mixed conifer forest, Sierra San Pedro Mártir, Mexico

2010 ◽  
Vol 40 (9) ◽  
pp. 1803-1814 ◽  
Author(s):  
Danny L. Fry ◽  
Scott L. Stephens
Keyword(s):  
Spatial Pattern ◽  
Forest Structure ◽  
Forest Ecosystems ◽  
Conifer Forest ◽  
Spatial Correlations ◽  
Mixed Conifer ◽  
Old Growth ◽  
Jeffrey Pine ◽  
Old Growth Forest ◽  
Mixed Conifer Forest

Descriptions of spatial patterns are important components of forest ecosystems, providing insights into functions and processes, yet basic spatial relationships between forest structures and fuels remain largely unexplored. We used standardized omnidirectional semivariance modeling to examine the spatial pattern of fuels and forest structure measured in a systematic nested plot grid covering 144 ha. Forest structure variables were spatially dependent at scales ranging from 62 to 572 m. Cross-variograms of fuels and forest structure showed both positive and negative correlations, ranging from 0.04 to 0.67. Notably, fine fuels were correlated positively and negatively with forest structure variables of white fir ( Abies concolor (Gord. & Glend.) Lindl. ex Hildebr.) and Jeffrey pine ( Pinus jeffreyi Balf.), respectively. Old-growth Jeffrey pine – mixed conifer forest within the study area exhibited both identifiable spatial correlations and high stand-level spatial heterogeneity, as demonstrated by the influence of outliers on the underlying spatial pattern. The spatial dependency of fuels with species-specific variables suggests that less common species may have a large influence in the characterization of forest attributes and that fuel classifications may be improved by accounting for the spatial distributions of overstory species. Spatial correlations have many applications to forest management, including the classification and mapping of forest structure, establishing guidelines for fuel treatments, and restoration of old-growth forest ecosystems.

Spatial variability in microclimate in a mixed-conifer forest before and after thinning and burning treatments

2010 ◽  
Vol 259 (5) ◽  
pp. 904-915 ◽  
Author(s):  
Siyan Ma ◽  
Amy Concilio ◽  
Brian Oakley ◽  
Malcolm North ◽  
Jiquan Chen
Keyword(s):  
Spatial Variability ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Mixed Conifer Forest ◽  
Before And After
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