Fire-scar formation in Jeffrey pine – mixed conifer forests in the Sierra San Pedro Mártir, Mexico

2010 ◽  
Vol 40 (8) ◽  
pp. 1497-1505 ◽  
Author(s):  
Scott L. Stephens ◽  
Danny L. Fry ◽  
Brandon M. Collins ◽  
Carl N. Skinner ◽  
Ernesto Franco-Vizcaíno ◽  
...  
Keyword(s):  
Sierra Nevada ◽  
Fire Frequency ◽  
Scar Formation ◽  
Mixed Conifer ◽  
Fire Scars ◽  
Fire Scar ◽  
Jeffrey Pine ◽  
San Pedro ◽  
Mixed Conifer Forests ◽  
Sierra San Pedro Martir

Little is known about the probability of fire-scar formation. In this study, we examined all mixed conifer trees for fire-scar formation in a 16 ha watershed that burned as part of a 2003 wildfire in Sierra San Pedro Mártir National Park (SSPM), Mexico. In addition, we examine the probability of fire-scar formation in relation to the previous fire interval in forests in the SSPM and Sierra Nevada. Within the 16 ha SSPM watershed, 1647 trees were assessed (100% census) for new fire scars. The SSPM wildfire burned around the base of 78% of the trees, but only 8% developed a new fire scar. Although the years from tree germination to first fire scar could potentially represent a fire-free period, there is clear evidence from this study that the inclusion of this interval when computing fire statistics is not justified. When the time since previous fire was <10 years, 10–30 years, and >57 years, the probability of rescarring was approximately 0.05, 0.5, and 0.75, respectively. In areas where fires were frequent (<10 years), fire frequencies derived from fire scars will likely underestimate true fire frequency, at least in forests that are similar to those studied here.

Comparing modern and past fire regimes to assess changes in prehistoric lightning and anthropogenic ignitions in a Jeffrey pine – mixed conifer forest in the Sierra San Pedro Mártir, Mexico

2007 ◽  
Vol 37 (2) ◽  
pp. 318-330 ◽  
Author(s):  
Rand R. Evett ◽  
Ernesto Franco-Vizcaino ◽  
Scott L. Stephens
Keyword(s):  
Fire Regime ◽  
Climatic Factors ◽  
Fire Regimes ◽  
Fire Frequency ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
The Past ◽  
Jeffrey Pine ◽  
San Pedro ◽  
Sierra San Pedro Martir

Fire histories of Jeffrey pine ( Pinus jeffreyi Grev. & Balf.) – mixed conifer forests in the Sierra San Pedro Mártir, Baja California, Mexico, recently described through analysis of 300 years of tree-ring fire-scars, indicate there have been four distinct fire-regime periods based on fire frequency and size. We used modern lightning and fire data to assess whether the current lightning regime could have supported the prehistoric fire regime. Although there are several sources of uncertainty, the present lightning regime, concentrated in the summer with little spring activity, may be insufficient to support the high number and spring seasonality of fires recorded during some periods in the past. Changes in the ignition regime recorded during the past 300 years could have been due to anthropogenic and (or) climatic factors; available evidence suggests periods of frequent fire were dominated by anthropogenic ignitions.

Phytolith evidence for the absence of a prehistoric grass understory in a Jeffrey pine – mixed conifer forest in the Sierra San Pedro Mártir, Mexico

2007 ◽  
Vol 37 (2) ◽  
pp. 306-317 ◽  
Author(s):  
Rand R. Evett ◽  
Ernesto Franco-Vizcaino ◽  
Scott L. Stephens
Keyword(s):  
Fire Regime ◽  
Grass Cover ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
High Concentration ◽  
Fire Scar ◽  
Jeffrey Pine ◽  
San Pedro ◽  
Mixed Conifer Forest ◽  
Sierra San Pedro Martir

Phytolith analysis was applied to several sites in a Jeffrey pine ( Pinus jeffreyi Grev. & Balf.) – mixed conifer forest in the Sierra San Pedro Mártir, Baja California, Mexico, to explore the hypothesis that the introduction of livestock in the late 18th century led to overgrazing of a prehistoric grass understory, resulting in changes to the prehistoric fire regime observed in the tree-ring fire-scar record. Stable soils in regions with extensive prehistoric grass cover retain a high concentration of total phytoliths and high percentage of grass phytoliths, regardless of historic vegetation changes. Phytoliths extracted from soil samples collected from several sites in the Sierra San Pedro Mártir revealed total phytolith concentrations in forest soils were generally <0.5% by mass, with most <0.1%, whereas grass phytoliths were generally <10% of the total, values consistent with the interpretation of a forest with sparse grass cover in the understory. Phytolith evidence suggests that there was minimal grass available for grazing in prehistoric Sierra San Pedro Mártir forests; overgrazing a grass understory was probably not a major driver of changes in the prehistoric fire regime.

scholarly journals Dendrochronology-based fire history of Jeffrey pine - mixed conifer forests in the Sierra San Pedro Martir, Mexico

2003 ◽  
Vol 33 (6) ◽  
pp. 1090-1101 ◽  
Author(s):  
Scott L Stephens ◽  
Carl N Skinner ◽  
Samantha J Gill
Keyword(s):  
Sierra Nevada ◽  
Fire History ◽  
Western Slope ◽  
Conifer Forests ◽  
Mixed Conifer ◽  
Large Spatial Scale ◽  
San Pedro ◽  
Mixed Conifer Forests ◽  
Northwestern Mexico ◽  
Sierra San Pedro Martir

Conifer forests in northwestern Mexico have not experienced systematic fire suppression or logging, making them unique in western North America. Fire regimes of Pinus jeffreyi Grev. & Balf. mixed conifer forests in the Sierra San Pedro Martir, Baja California, Mexico, were determined by identifying 105 fire dates from 1034 fire scars in 105 specimens. Fires were recorded between 1521 and 1980 and median fire return intervals were less than 15 years at all compositing scales. Significant differences in mean fire return intervals were detected from 1700 to 1800, 1800 to 1900, and 1900 to 1997, most often at intermediate spatial compositing scales, and the proportion of trees scarred in the fires of the 1700s was significantly different from the fires of either the 1800s, the 1900s, or the combined post-1800 period. Superposed epoch analysis determined that moderate and large spatial scale fires occurred on significantly dry years during the length of the record, but before 1800, these fires were preceded by significantly higher precipitation 1 year before the fire. The dominance of earlywood fires in the Sierra San Pedro Martir is similar to the seasonality found in the southwest United States and is different from the western slope of the Sierra Nevada and Klamath Mountains of California.

Coarse woody debris and canopy cover in an old-growth Jeffrey pine-mixed conifer forest from the Sierra San Pedro Martir, Mexico

2007 ◽  
Vol 240 (1-3) ◽  
pp. 87-95 ◽  
Author(s):  
Scott L. Stephens ◽  
Danny L. Fry ◽  
Ernesto Franco-Vizcaíno ◽  
Brandon M. Collins ◽  
Jason M. Moghaddas
Keyword(s):  
Coarse Woody Debris ◽  
Woody Debris ◽  
Canopy Cover ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Old Growth ◽  
Jeffrey Pine ◽  
San Pedro ◽  
Mixed Conifer Forest ◽  
Sierra San Pedro Martir

Pathogens and insects in a pristine forest ecosystem: the Sierra San Pedro Martir, Baja, Mexico

2002 ◽  
Vol 32 (3) ◽  
pp. 448-457 ◽  
Author(s):  
Patricia E Maloney ◽  
David M Rizzo
Keyword(s):  
Forest Ecosystem ◽  
Bark Beetles ◽  
Stand Structure ◽  
Linear Regression Analysis ◽  
Mixed Conifer ◽  
San Pedro ◽  
White Fir ◽  
Sugar Pine ◽  
Sierra San Pedro Martir ◽  
Pristine Forest

We determined the incidence of pathogens and insects across mixed-conifer stands in the Sierra San Pedro Martir (SSPM) of northern Baja, Mexico, to assess the role of pests in a pristine forest ecosystem. We also determined the spatial distribution of the two most common pests, mistletoe, Phoradendron pauciflorum Torrey, and the fir engraver, Scolytus ventralis LeConte, of white fir (Abies concolor (Gord. & Glend.) Lindl.) across a 25-ha grid to assess spread and what host and pest variables were related. In these open parklike stands the mean tree density was 160 trees/ha, of which 58% were trees >20 cm diameter at breast height (DBH). In these low-density, mixed-aged stands we found that mixed-conifer species were well represented with no one species being completely dominant. Percent cumulative mortality for the SSPM was 12.7%, ranging from 2 to 24%, with the greatest amount of mortality occurring in the larger size classes, trees [Formula: see text]50 cm DBH. Multiple linear regression analysis showed that 78% of the mortality we observed was explained by pathogens and bark beetles (r2 = 0.78, P = 0.0001, F = 84). Mean pest incidence for Jeffrey pine (Pinus jeffreyi Grev. & Balf. in A. Murray), white fir, and sugar pine (Pinus lambertiana Dougl.) was 21, 88, and 2%, respectively. We found a number of relationships among host and pest variables, as well as a pathogen– insect interaction, and across the SSPM we found that nonhost species may be interfering in certain host–pest interactions. Spatial patterns from the 25-ha grid survey revealed that both P. pauciflorum and S. ventralis incidence were widespread. Phoradendron pauciflorum showed no spatial structure across the 25 ha but S. ventralis showed some degree of spatial structuring across the survey area. We also found that mistletoe severity was negatively correlated with regeneration of white fir. In pristine forests, pathogens and insects influence mortality and regeneration success, affecting stand structure and composition.

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
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