Using light to predict fuels-reduction and group-selection effects on succession in Sierran mixed-conifer forest

2011 ◽  
Vol 41 (10) ◽  
pp. 2051-2063 ◽  
Author(s):  
Seth W. Bigelow ◽  
Malcolm P. North ◽  
Carl F. Salk
Keyword(s):  
Sierra Nevada ◽  
Pinus Ponderosa ◽  
Ponderosa Pine ◽  
Group Selection ◽  
Wildlife Habitat ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Fuels Reduction ◽  
Mixed Conifer Forest ◽  
Large Trees

Many semi-arid coniferous forests in western North America have reached historically unprecedented densities over the past 150 years and are dominated by shade-tolerant trees. Silvicultural treatments generally open the canopy but may not restore shade-intolerant species. We determined crossover-point irradiance (CPI) (light at which the height growth rank of pairs of species changes) for seedlings in Sierra Nevada mixed-conifer forest and used these to interpret light environments produced by fuels-reduction thinning and group selection with reserved large trees. Nine of 21 species pairs had well-defined CPIs. The CPI of the most common shade-tolerant and intolerant species (white fir ( Abies concolor (Gordon & Glendl.) Lindl. ex Hildebr.) and ponderosa pine ( Pinus ponderosa Douglas ex P. Lawson & C. Lawson)) was 22.5 mol·m–2·day–1 or 41% of full sun. Median understory irradiance increased from 9.2 mol·m–2·day–1 (17% full sun) in pretreatment forest to 13 mol·m–2·day–1 (24% full sun) in lightly and 15.5 mol·m–2·day–1 (28% full sun) in moderately thinned stands and 37 mol·m–2·day–1 (67% full sun) in group-selection openings. We estimate that 5%–20% of ground area in lightly to moderately thinned stands would have enough light to favor shade-intolerant over shade-tolerant growth compared with 89% of ground area in group-selection openings. The CPI provides a tool to assess regeneration implications of treatment modification such as increasing heterogeneity of thinning to enhance regeneration or reserving large trees in group-selection openings to maintain wildlife habitat.

scholarly journals Historical and current landscape-scale ponderosa pine and mixed conifer forest structure in the Southern Sierra Nevada

Ecosphere ◽  
2015 ◽  
Vol 6 (5) ◽  
pp. art79 ◽  
Author(s):  
Scott L. Stephens ◽  
Jamie M. Lydersen ◽  
Brandon M. Collins ◽  
Danny L. Fry ◽  
Marc D. Meyer
Keyword(s):  
Sierra Nevada ◽  
Forest Structure ◽  
Ponderosa Pine ◽  
Landscape Scale ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Mixed Conifer Forest

Tree mortality patterns following prescribed fires in a mixed conifer forest

2006 ◽  
Vol 36 (12) ◽  
pp. 3222-3238 ◽  
Author(s):  
Leda Kobziar ◽  
Jason Moghaddas ◽  
Scott L Stephens
Keyword(s):  
Sierra Nevada ◽  
Ponderosa Pine ◽  
Tree Mortality ◽  
Fire Behavior ◽  
Mortality Rates ◽  
Fire Intensity ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Mixed Conifer Forest ◽  
White Fir

During the late fall of 2002 we administered three burns in mixed conifer forest sites in the north-central Sierra Nevada. Eight months later we measured fire-induced injury and mortality in 1300 trees. Using logistic regression, an array of crown scorch, stem damage, fuels, and fire-behavior variables were examined for their influence on tree mortality. In Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), white fir (Abies concolor (Gord. & Glend.) Lindl.), and incense cedar (Calocedrus decurrens (Torr.) Florin), smaller trees with greater total crown damage had higher mortality rates. Smaller stem diameters and denser canopies predicted mortality best in ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws). Duff consumption and bark char severity increased model discrimination for white fir and incense cedar and California black oak (Quercus kelloggii Newberry), respectively. In tanoak (Lithocarpus densiflorus (Hook. & Arn.) Rehd.), greater total crown damage in shorter trees resulted in higher mortality rates. Along with tree diameter and consumption of large (>7.6 cm diameter at breast height, DBH) rotten downed woody debris, fire intensity was a significant predictor of overall tree mortality for all species. Mortality patterns for white fir in relation to crown damage were similar among sites, while those for incense cedar were not, which suggests that species in replicated sites responded differently to similar burns. Our results demonstrate actual fire-behavior data incorporated into mortality models, and can be used to design prescribed burns for targeted reduction of tree density in mixed conifer forests.

scholarly journals Armillaria Root Disease-Caused Tree Mortality following Silvicultural Treatments (Shelterwood or Group Selection) in an Oregon Mixed-Conifer Forest: Insights from a 10-Year Case Study

2010 ◽  
Vol 25 (3) ◽  
pp. 136-143 ◽  
Author(s):  
Gregory M. Filip ◽  
Helen M. Maffei ◽  
Kristen L. Chadwick ◽  
Timothy A. Max
Keyword(s):  
Ponderosa Pine ◽  
Group Selection ◽  
Tree Mortality ◽  
Douglas Fir ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Silvicultural Treatments ◽  
Mixed Conifer Forest ◽  
Armillaria Root Disease

Abstract In 2005, the 10-year effects of two silvicultural treatments (group-selection and shelterwood) on tree-growth loss and mortality caused by Armillaria ostoyae were compared with no treatment in a mixed-conifer forest in south-central Oregon. Ten years after treatment, Armillaria-caused mortality varied by species and was greatest in Shasta red fir (38% of trees per acre) and white fir (31%) and much less in Douglas-fir (3%) and ponderosa pine (0%). Ten years after harvesting, leave-tree mortality caused by Armillaria root disease was not significantly different in treated than in the unharvested units, nor was there significant diameter-growth response to the harvesting even in large ponderosa pine and Douglas-fir. The silvicultural treatments did have some benefits: (1) leave-tree mortality appeared, at least, not to be exacerbated by harvesting; (2) more disease-resistant pine, cedar, and larch seedlings and saplings survived in the shelterwood-harvest stands and group-selection openings than in comparable areas that were not harvested; and (3) living wood fiber was recovered from the treated stands, as well as dying and dead fuels that could exacerbate wildfire losses. Insights into host-pathogen interactions and recommendations for silvicultural options are presented. This is a case study from a single site and should be interpreted as such.

Development of the mixed conifer forest in northern New Mexico and its relationship to Holocene environmental change

2008 ◽  
Vol 69 (2) ◽  
pp. 263-275 ◽  
Author(s):  
R. Scott Anderson ◽  
Renata B. Jass ◽  
Jaime L. Toney ◽  
Craig D. Allen ◽  
Luz M. Cisneros-Dozal ◽  
...  
Keyword(s):  
New Mexico ◽  
Pinus Ponderosa ◽  
Late Glacial ◽  
Conifer Forest ◽  
Lake Levels ◽  
Mixed Conifer ◽  
The Holocene ◽  
Groundwater Levels ◽  
Mixed Conifer Forest ◽  
Jemez Mountains

Chihuahueños Bog (2925 m) in the Jemez Mountains of northern New Mexico contains one of the few records of late-glacial and postglacial development of the mixed conifer forest in southwestern North America. The Chihuahueños Bog record extends to over 15,000 cal yr BP. AnArtemisiasteppe, then an openPiceawoodland grew around a small pond until ca. 11,700 cal yr BP whenPinus ponderosabecame established. C/N ratios,δ13C andδ15N values indicate both terrestrial and aquatic organic matter was incorporated into the sediment. Higher percentages of aquatic algae and elevated C/N ratios indicate higher lake levels at the opening of the Holocene, but a wetland developed subsequently as climate warmed. From ca. 8500 to 6400 cal yr BP the pond desiccated in what must have been the driest period of the Holocene there. C/N ratios declined to their lowest Holocene levels, indicating intense decomposition in the sediment. Wetter conditions returned after 6400 cal yr BP, with conversion of the site to a sedge bog as groundwater levels rose. Higher charcoal influx rates after 6400 cal yr BP probably result from greater biomass production rates. Only minor shifts in the overstory species occurred during the Holocene, suggesting that mixed conifer forest dominated throughout the record.

Sign in / Sign up

Export Citation Format

Share Document