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.

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.

Litter dynamics in two Sierran mixed conifer forests. II. Nutrient release in decomposing leaf litter

1988 ◽  
Vol 18 (9) ◽  
pp. 1136-1144 ◽  
Author(s):  
Thomas J. Stohlgren
Keyword(s):  
Leaf Litter ◽  
Sierra Nevada ◽  
Nutrient Release ◽  
Conifer Forests ◽  
Mixed Conifer ◽  
Acid Detergent Fiber ◽  
White Fir ◽  
Mixed Conifer Forests ◽  
Sugar Pine ◽  
Giant Sequoia

The factors influencing leaf litter decomposition and nutrient release patterns were investigated for 3.6 years in two mixed conifer forests in the southern Sierra Nevada of California. The giant sequoia–fir forest was dominated by giant sequoia (Sequoiadendrongiganteum (Lindl.) Buchh.), white fir (Abiesconcolor Lindl. & Gord.), and sugar pine (Pinuslambertiana Dougl.). The fir–pine forest was dominated by white fir, sugar pine, and incense cedar (Calocedrusdecurrens (Torr.) Florin). Initial concentrations of nutrients and percent lignin, cellulose, and acid detergent fiber vary considerably in freshly abscised leaf litter of the studied species. Giant sequoia had the highest concentration of lignin (20.3%) and the lowest concentration of nitrogen (0.52%), while incense cedar had the lowest concentration of lignin (9.6%) and second lowest concentration of nitrogen (0.63%). Long-term (3.6 years) foliage decomposition rates were best correlated with initial lignin/N (r2 = 0.94, p < 0.05), lignin concentration (r2 = 0.92, p < 0.05), and acid detergent fiber concentration (r2 = 0.80, p < 0.05). Patterns of nutrient release were highly variable. Giant sequoia immobilized N and P, incense cedar immobilized N and to a lesser extent P, while sugar pine immobilized Ca. Strong linear or negative exponential relationships existed between initial concentrations of N, P, K, and Ca and percent original mass remaining of those nutrients after 3.6 years. This suggests efficient retention of these nutrients in the litter layer of these ecosystems. Nitrogen concentrations steadily increase in decomposing leaf litter, effectively reducing the C/N ratios from an initial range of 68–96 to 27–45 after 3.6 years.

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.

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.

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.

Wald und Klimawandel in der inneralpinen Trockenregion Visp

2012 ◽  
Vol 163 (12) ◽  
pp. 481-492
Author(s):  
Andreas Rigling ◽  
Ché Elkin ◽  
Matthias Dobbertin ◽  
Britta Eilmann ◽  
Arnaud Giuggiola ◽  
...  
Keyword(s):  
Climate Change ◽  
Ecosystem Services ◽  
Forest Management ◽  
Forest Ecosystem ◽  
Bark Beetles ◽  
Forest Ecosystems ◽  
Field Experiments ◽  
Forest Monitoring ◽  
Management Interventions ◽  
Forest Ecosystem Services

Forest and climate change in the inner-Alpine dry region of Visp Over the past decades, observed increases in temperature have been particularly pronounced in mountain regions. If this trend should continue in the 21st Century, frequency and intensity of droughts will increase, and will pose major challenges for forest management. Under current conditions drought-related tree mortality is already an important factor of forest ecosystems in dry inner-Alpine valleys. Here we assess the sensitivity of forest ecosystems to climate change and evaluate alternative forest management strategies in the Visp region. We integrate data from forest monitoring plots, field experiments and dynamic forests models to evaluate how the forest ecosystem services timber production, protection against natural hazards, carbon storage and biodiver-sity will be impacted. Our results suggest that at dry low elevation sites the drought tolerance of native tree species will be exceeded so that in the longer term a transition to more drought-adapted species should be considered. At medium elevations, drought and insect disturbances as by bark beetles are projected to be important for forest development, while at high elevations forests are projected to expand and grow better. All of the ecosystem services that we considered are projected to be impacted by changing forest conditions, with the specific impacts often being elevation-dependent. In the medium term, forest management that aims to increase the resilience of forests to drought can help maintain forest ecosystem services temporarily. However, our results suggest that relatively rigid management interventions are required to achieve significant effects. By using a combination of environmental monitoring, field experiments and modeling, we are able to gain insight into how forest ecosystem, and the services they provide, will respond to future changes.

Spatial variation in CO2 efflux from the soil in a mature beech forest ecosystem.

2021 ◽  
Author(s):  
Yihan Cai ◽  
Takahiro Nishimura ◽  
Hideyuki Ida ◽  
Mitsuru Hirota
Keyword(s):  
Spatial Variation ◽  
Temporal Variation ◽  
Forest Ecosystem ◽  
Linear Regression Analysis ◽  
Basal Area ◽  
Beech Forest ◽  
Controlling Factors ◽  
Spatial And Temporal Variation ◽  
Canopy Openness ◽  
Co2 Efflux

&lt;p&gt;&amp;#160;Soil respiration (Rs) is the second largest carbon flux between the atmosphere and terrestrial ecosystem. Because of the large proportion, even small change in Rs would considerably impact the global carbon cycle. Therefore, it is important to accurately estimate Rs by taking its spatial and temporal variation into consideration. While the temporal variation of Rs and its controlling factors have been well-described, large unexplainable part still has been remained in the spatial variation of Rs especially in the forest ecosystems with complex structures. The objective of this study is to fill the knowledge gap about spatial variation of Rs and its controlling factors in a typical mature beech forest in Japan. Hypotheses of this study were, 1) Rs would show large spatial variation in the mature beech forest, 2) the spatial variation of Rs was mainly influenced by soil water content (SWC) and soil temperature (ST), 3) the two key factors were determined by the forest structures. This study was conducted in a 1- ha permanent study plot in the mature beech forest with significant gap-mosaic structures. To examine these hypotheses, Rs, SWC, ST and parameters related to forest structure, i.e. sum of basal area, diameter at breast height, number of trees, number of species within a radius of 5 m from the Rs measurement points, and canopy openness were measured at 121 points in different season between 2012 to 2013. In this study, all the measurements of Rs were conducted by using alkali-absorption technique.&lt;/p&gt;&lt;p&gt;&amp;#160;Coefficient of variation of Rs was between 25 - 28 % which was similar to that of SWC in all the measurements. The spatial variation of Rs was relatively higher in July, August and September than that in June and October. There was no significant relationship in the spatial variation between Rs and ST in all the measurements, meanwhile, Rs was well explained by SWC in measurements conducted in August, September and October. Multiple linear regression analysis indicated that canopy openness and sum of basal area showed significant positive and negative correlation with SWC, respectively. And canopy openness explained SWC much more than sum of basal area did. This result suggested that SWC, the key factor determined the spatial variation of Rs, cannot be only explained by stems distribution and their characteristics, but also canopy architecture in the forest ecosystem.&lt;/p&gt;

scholarly journals A coastal population of Large-blotched Ensatina Ensatina klauberi (Caudata: Plethodontidae) in Baja California, México

Check List ◽  
2015 ◽  
Vol 11 (3) ◽  
pp. 1649 ◽  
Author(s):  
Jorge Heriberto Valdez-Villavicencio ◽  
Anny Peralta-Garcia ◽  
Bradford Damion Hollingsworth
Keyword(s):  
Baja California ◽  
Volcanic Field ◽  
Species Range ◽  
Oak Woodlands ◽  
Coastal Population ◽  
San Pedro ◽  
Sierra San Pedro Martir

We found a new population of Ensatina klauberi in San Quintín volcanic field, Baja California. It represents the first coastal population of this species. This record extends the species range ca. 71 km southwest of the southernmost record of E. klauberi in the Sierra San Pedro Mártir and represents the first population discovered outside of coniferous and pine-oak woodlands.

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