Recent bark beetle outbreaks influence wildfire severity in mixed‐conifer forests of the Sierra Nevada, California, USA

2021 ◽  
Author(s):  
Rebecca B. Wayman ◽  
Hugh D. Safford
Keyword(s):  
Sierra Nevada ◽  
Bark Beetle ◽  
Conifer Forests ◽  
Mixed Conifer ◽  
Mixed Conifer Forests

Characterizing the light environment in Sierra Nevada mixed-conifer forests using a spatially explicit light model

2004 ◽  
Vol 34 (6) ◽  
pp. 1332-1342 ◽  
Author(s):  
Rolf Gersonde ◽  
John J Battles ◽  
Kevin L O'Hara
Keyword(s):  
Leaf Area ◽  
Sierra Nevada ◽  
Forest Type ◽  
Individual Species ◽  
Spatially Explicit ◽  
Conifer Forests ◽  
Prediction Equations ◽  
Mixed Conifer ◽  
Sapwood Area ◽  
Mixed Conifer Forests

The spatially explicit light model tRAYci was calibrated to conditions in multi-aged Sierra Nevada mixed-conifer forests. To reflect conditions that are important to growth and regeneration of this forest type, we sampled a variety of managed mature stands with multiple canopy layers and cohorts. Calibration of the light model included determining leaf area density for individual species with the use of leaf area – sapwood area prediction equations. Prediction equations differed between species and could be improved using site index. The light model predicted point measurements from hemispherical photographs well over a range of 27%–63% light. Simplifying the crown representation in the tRAYci model to average values for species and canopy strata resulted in little reduction in model performance and makes the model more useful to applications with lower sampling intensity. Vertical light profiles in managed mixed-conifer stands could be divided into homogeneous, sigmiodal, and continuous gradients, depending on stand structure and foliage distribution. Concentration of leaf area in the upper canopy concentrates light resources on dominant trees in continuous canopies. Irregular canopies of multiaged stands, however, provide more light resources to mid-size trees and could support growth of shade-intolerant species. Knowledge of the vertical distribution of light intensity in connection with stand structural information can guide regulation of irregular stand structures to meet forest management objectives.

Empirically validated drought vulnerability mapping in the mixed conifer forests of the Sierra Nevada

2021 ◽  
Author(s):  
Adrian J. Das ◽  
Michèle R. Slaton ◽  
Jeffrey Mallory ◽  
Gregory P. Asner ◽  
Roberta E. Martin ◽  
...  
Keyword(s):  
Sierra Nevada ◽  
Vulnerability Mapping ◽  
Conifer Forests ◽  
Mixed Conifer ◽  
Drought Vulnerability ◽  
Mixed Conifer Forests

scholarly journals Historical and modern landscape forest structure in fir (Abies)-dominated mixed conifer forests in the northern Sierra Nevada, USA

Fire Ecology ◽  
2018 ◽  
Vol 14 (2) ◽  
Author(s):  
Scott L Stephens ◽  
Jens T Stevens ◽  
Brandon M Collins ◽  
Robert A York ◽  
Jamie M Lydersen
Keyword(s):  
Sierra Nevada ◽  
Forest Structure ◽  
Conifer Forests ◽  
Mixed Conifer ◽  
Mixed Conifer Forests ◽  
Modern Landscape

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

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.

Variation in leaf area index in complex mixed-conifer forests in California’s Sierra Nevada: implications for stocking control

2020 ◽  
Vol 93 (5) ◽  
pp. 641-651
Author(s):  
Kevin L O’Hara ◽  
John J Battles
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Sierra Nevada ◽  
Timber Harvest ◽  
Forest Community ◽  
Conifer Forests ◽  
Mixed Conifer ◽  
Area Index ◽  
Mixed Conifer Forests ◽  
Study Sites

Abstract The mixed-conifer forests in California’s Sierra Nevada include species from several genera (Pinus, Abies, Pseudotsuga, Calocedrus and Sequoiadendron). These forests have complex disturbance regimes dominated by low to moderate severity fire that often resulted in patchy spatial patterns and multiaged stands. Leaf area index (LAI) describes the total leaf surface area per unit area in a forest community and is related to wood and biomass production and ecosystem values such as water usage, water yields and carbon sequestration. LAI can also serve as a representation of growing space occupancy and the basis for stocking control, including in multiaged stands. Nine study sites were sampled with 22–37 0.05 ha plots per study site to estimate LAI and other metrics. LAI was highest in study sites with greater proportions of shade tolerant Abies and Calocedrus species and on higher productivity sites. Recent drought-related mortality has reduced stocking and LAI. The combination of fire suppression and timber harvest over the past century has resulted in stands with higher densities, and greater proportions of shade tolerant species. Managing these structures to restore their presettlement character will involve reducing overall stocking, increasing proportions of intolerant species and increasing fine-scale heterogeneity. LAI allocation—allocating leaf area to age classes, species or canopy strata—can be used to design new structures that resemble presettlement structures and are resilient to disturbances.

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