Fuel loads, snag abundance, and snag recruitment in an unmanaged Jeffrey pine–mixed conifer forest in Northwestern Mexico

2004 ◽  
Vol 199 (1) ◽  
pp. 103-113 ◽  
Author(s):  
Scott L. Stephens
Keyword(s):  
Conifer Forest ◽  
Mixed Conifer ◽  
Fuel Loads ◽  
Jeffrey Pine ◽  
Mixed Conifer Forest ◽  
Northwestern Mexico

Relating fuel loads to overstorey structure and composition in a fire-excluded Sierra Nevada mixed conifer forest

2015 ◽  
Vol 24 (4) ◽  
pp. 484 ◽  
Author(s):  
Jamie M. Lydersen ◽  
Brandon M. Collins ◽  
Eric E. Knapp ◽  
Gary B. Roller ◽  
Scott Stephens
Keyword(s):  
Sierra Nevada ◽  
Predictive Models ◽  
Vegetation Type ◽  
Fuel Load ◽  
Small Scale ◽  
Conifer Forest ◽  
Fire Behaviour ◽  
Mixed Conifer ◽  
Fuel Loads ◽  
Mixed Conifer Forest

Although knowledge of surface fuel loads is critical for evaluating potential fire behaviour and effects, their inherent variability makes these difficult to quantify. Several studies relate fuel loads to vegetation type, topography and spectral imaging, but little work has been done examining relationships between forest overstorey variables and surface fuel characteristics on a small scale (<0.05 ha). Within-stand differences in structure and composition would be expected to influence fuel bed characteristics, and thus affect fire behaviour and effects. We used intensive tree and fuel measurements in a fire-excluded Sierra Nevada mixed conifer forest to assess relationships and build predictive models for loads of duff, litter and four size classes of downed woody fuels to overstorey structure and composition. Overstorey variables explained a significant but somewhat small percentage of variation in fuel load, with marginal R2 values for predictive models ranging from 0.16 to 0.29. Canopy cover was a relatively important predictor for all fuel components, although relationships varied with tree species. White fir abundance had a positive relationship with total fine woody fuel load. Greater pine abundance was associated with lower load of fine woody fuels and greater load of litter. Duff load was positively associated with total basal area and negatively associated with oak abundance. Knowledge of relationships contributing to within-stand variation in fuel loads can increase our understanding of fuel accumulation and improve our ability to anticipate fine-scale variability in fire behaviour and effects in heterogeneous mixed species stands.

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

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.

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.

Mechanical fuel treatment effects on fuel loads and indices of crown fire potential in a south central New Mexico dry mixed conifer forest

2007 ◽  
Vol 251 (3) ◽  
pp. 195-204 ◽  
Author(s):  
Glenn J. Mason ◽  
Terrell T. Baker ◽  
Douglas S. Cram ◽  
Jon C. Boren ◽  
Alexander G. Fernald ◽  
...  
Keyword(s):  
New Mexico ◽  
Treatment Effects ◽  
Crown Fire ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Fuel Treatment ◽  
Fuel Loads ◽  
South Central ◽  
Mixed Conifer Forest

Habitat preferences of an arboreal forage lichen in a Sierra Nevada old-growth mixed-conifer forest

2010 ◽  
Vol 40 (6) ◽  
pp. 1034-1041 ◽  
Author(s):  
Thomas R. Rambo
Keyword(s):  
Sierra Nevada ◽  
Forest Canopy ◽  
Habitat Preferences ◽  
Vertical Gradient ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Abies Magnifica ◽  
Jeffrey Pine ◽  
Mixed Conifer Forest ◽  
Sugar Pine

The arboreal forage lichen Bryoria fremontii (Tuck.) Brodo & D.Hawksw. appears sensitive to conditions of prolonged hydration in wet forests of British Columbia. I estimated the abundance of this lichen in mixed-conifer forest canopy in the contrasting Mediterranean climate of the southern Sierra Nevada in relationship to the vertical gradient of vapor pressure deficit. Abundance was estimated by biomass in 5 m strata from the ground to the tops of 50 trees. Transplants of Bryoria thalli were installed in 18 fir trees for 1 year to assess their growth relative to distance from perennial streams. VPD generally increased with height, being significantly greater at 45 m than 5 m. Bryoria biomass averaged across tree heights was estimated as 15.9, 0.60, 0.15, 0.25, and 0.19 g·m–1 in red fir (Abies magnifica A.Murray), white fir (Abies concolor (Gordon & Glend.) Hildebr. var. lowiana (Gordon) Lemmon), incense cedar (Calocedrus decurrens (Torr.) Florin), Jeffrey pine (Pinus jeffreyi Balf.), and sugar pine (Pinus lambertiana Douglas), respectively. Transplant growth was significantly greater in trees <25 m from water (11.4%) than in trees >25 m from water (9.7%). Bryoria had strong positive associations with red fir, proximity to streams, and decreasing VPD. The sensitivity of Bryoria to prolonged hydration does not appear to be important in this climate characterized by extended summer dryness.

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