The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Roger F. Walker - One of the best experts on this subject based on the ideXlab platform.
-
Mechanized Thinning, Prescribed Fire, and Needle Age Influences on the Mineral Nutrition of Jeffrey Pine: Elemental Concentrations in Foliage and Soil
Forest Research: Open Access, 2016Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings using cut-to-length and whole-tree harvesting approaches followed by prescription underburning were assessed for their influences over multiple growing seasons on the mineral nutrition of Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.) on a Sierran site. Specifically examined were foliar and soil elemental concentrations encompassing macronutrients and micronutrients plus Al. Foliar N was higher in thinned stand subunits initially before transitioning to a relatively elevated concentration in the burned portion of either the cut-to-length or wholetree subunits, while higher foliar S in the burned cut-to-length treatment combination was evident in the last two of the six sampling periods. Foliar Mn was usually higher in the burned whole-tree combination while B and Al were often higher in burned stand portions but with less specificity regarding thinning treatment. At mid growing season, N, P, K, S, Fe, and Cu were higher in young needles while Ca, Mn, and Al were so in older ones. Near mid study, mineral soil Ca was higher in the unthinned subunit while Mg, Fe, Mn, Zn, and Cu were higher in unburned stand portions.
-
Elemental Ratios in Foliage and Soil of a Jeffrey Pine Stand Subjected to Thinning and Burning Restoration Practices
Forest Research: Open Access, 2016Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings accomplished through cut-to-length and whole-tree harvesting followed by a prescribed underburn were assessed for their influences on mineral nutrition in eastern Sierran Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.). As derived from foliar elemental concentrations determined at six samplings distributed over three growing seasons, molar Ca/Al, Mg/Al, K/Al, Ca/Mn, Mg/Mn, and K/Mn were generally higher in the unthinned treatment and lower in burned stand portions. Conducted under drought conditions, the driest phase of the study resulted in lower Ca/Al, Mg/Al, and K/Al and higher Ca/Mn and Ca/Zn when averaged across treatments. Foliar K/Mn, K/Zn, and K/Cu were generally lower in the early portion of the growing season compared to the late portion. At mid growing season, Mg/Al, K/Al, Mg/Mn, K/Mn, K/Fe, K/Zn, and K/Cu were higher in young needles while Ca/Al, Ca/Fe, Mg/Fe, Ca/Zn, Ca/Cu, and Mg/Cu were so in older ones. At mid study, soil Ca/Fe was higher in the unthinned treatment generally and especially in its unburned portion while K/Cu was higher overall in burned stand portions, most especially in the unthinned treatment. These findings provide insight into the interrelationships of base cations and metallic elements in forest nutrition as influenced by restoration practices.
-
Bark Beetle Demography in Sierra Nevada Mixed Conifer: Variability and Influencing Factors
Forest Research: Open Access, 2015Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Multiple forest health variables were examined in an eastern Sierra Nevada mixed conifer stand, principal among them bark beetle demography. As indicated by pitch tube counts, California white fir (Abies concolor var. lowiana [Gord.] Lemm.), the predominant species, was colonized prodigiously compared to Jeffrey Pine (Pinus Jeffreyi Grev. and Balf.) and sugar Pine (Pinus lambertiana Dougl.). Across host species, pitch tube abundance was positively related to white fir prevalence and negatively related to tree species diversity. Bark beetles preferentially attacked trees of small to medium DBH in white fir and sugar Pine. Attack intensity in small Jeffrey Pine was positively correlated with stand basal area and biomass and that in sugar Pine of medium size was positively correlated with basal area also. Minor mistletoe infestations were detected in white fir along with incense-cedar (Libocedrus decurrens Torr.) and California red fir (Abies magnifica A. Murr.), with bark beetle colonization in the smallest and largest white fir positively related to the percentage of this fir thus infested. Mortality in white fir and Jeffrey Pine irrespective of size was positively correlated with the pitch tube count in the largest white fir regarding the former and with total tree count regarding the latter.
-
Evaluation of Mechanized Thinning and Prescribed Fire Effects on Long-Term Fuels Accumulations in Uneven-Aged Jeffrey Pine
Journal of Sustainable Forestry, 2014Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings implemented through cut-to-length and whole-tree harvesting followed by underburning were evaluated for their effects on long-term downed and dead fuels accumulations in pure, uneven-aged Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.) accompanied by isolated California white fir (Abies concolor var. lowiana [Gord.] Lemm.). Based on an initial inventory consisting of dry weight and fuel bed depth measurements conducted posttreatment, accumulations in the cut-to-length treatment were elevated according to most measures. Burned stand portions exhibited smaller quantities of fuels initially in individual timelag categories and in total as well as reduced fuel bed depths compared to their unburned counterparts except for the 1,000-hr fuels in the whole-tree treatment where postburn mortality of small stems nullified this effect. A linkage between initial mortality resulting from prescribed fire and final 1,000-hr fuels, as measured 8 yr later, was established but was probably attributable to comb...
-
Influences of Thinning and Underburning Restoration Practices on Red Turpentine Beetle Demography in Jeffrey Pine
Journal of Sustainable Forestry, 2014Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings implemented with cut-to-length and whole-tree harvesting systems followed by prescribed underburning were evaluated for their effects on red turpentine beetle (Dendroctonus valens LeConte) colonization in pure, uneven-aged Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.). Based on pitch tube abundance expressed as bole surface area-based counts, this beetle was significantly more prevalent where thinnings were implemented regardless of harvesting approach than in the unthinned treatment, but the population increases were confined to the burned stand portions. Substantial evidence indicated that fire-induced crown and bole damage culminating in compromised defense mechanisms elevated turpentine beetle colonization, and some evidence suggested a proclivity of this beetle to attack stems exhibiting general characteristics of low vigor, specifically smaller trees with weak crowns. Tree mortality was likely induced by the turpentine beetle infestation but was probably not its sole cause. The respon...
Watkins W. Miller - One of the best experts on this subject based on the ideXlab platform.
-
Mechanized Thinning, Prescribed Fire, and Needle Age Influences on the Mineral Nutrition of Jeffrey Pine: Elemental Concentrations in Foliage and Soil
Forest Research: Open Access, 2016Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings using cut-to-length and whole-tree harvesting approaches followed by prescription underburning were assessed for their influences over multiple growing seasons on the mineral nutrition of Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.) on a Sierran site. Specifically examined were foliar and soil elemental concentrations encompassing macronutrients and micronutrients plus Al. Foliar N was higher in thinned stand subunits initially before transitioning to a relatively elevated concentration in the burned portion of either the cut-to-length or wholetree subunits, while higher foliar S in the burned cut-to-length treatment combination was evident in the last two of the six sampling periods. Foliar Mn was usually higher in the burned whole-tree combination while B and Al were often higher in burned stand portions but with less specificity regarding thinning treatment. At mid growing season, N, P, K, S, Fe, and Cu were higher in young needles while Ca, Mn, and Al were so in older ones. Near mid study, mineral soil Ca was higher in the unthinned subunit while Mg, Fe, Mn, Zn, and Cu were higher in unburned stand portions.
-
Elemental Ratios in Foliage and Soil of a Jeffrey Pine Stand Subjected to Thinning and Burning Restoration Practices
Forest Research: Open Access, 2016Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings accomplished through cut-to-length and whole-tree harvesting followed by a prescribed underburn were assessed for their influences on mineral nutrition in eastern Sierran Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.). As derived from foliar elemental concentrations determined at six samplings distributed over three growing seasons, molar Ca/Al, Mg/Al, K/Al, Ca/Mn, Mg/Mn, and K/Mn were generally higher in the unthinned treatment and lower in burned stand portions. Conducted under drought conditions, the driest phase of the study resulted in lower Ca/Al, Mg/Al, and K/Al and higher Ca/Mn and Ca/Zn when averaged across treatments. Foliar K/Mn, K/Zn, and K/Cu were generally lower in the early portion of the growing season compared to the late portion. At mid growing season, Mg/Al, K/Al, Mg/Mn, K/Mn, K/Fe, K/Zn, and K/Cu were higher in young needles while Ca/Al, Ca/Fe, Mg/Fe, Ca/Zn, Ca/Cu, and Mg/Cu were so in older ones. At mid study, soil Ca/Fe was higher in the unthinned treatment generally and especially in its unburned portion while K/Cu was higher overall in burned stand portions, most especially in the unthinned treatment. These findings provide insight into the interrelationships of base cations and metallic elements in forest nutrition as influenced by restoration practices.
-
Bark Beetle Demography in Sierra Nevada Mixed Conifer: Variability and Influencing Factors
Forest Research: Open Access, 2015Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Multiple forest health variables were examined in an eastern Sierra Nevada mixed conifer stand, principal among them bark beetle demography. As indicated by pitch tube counts, California white fir (Abies concolor var. lowiana [Gord.] Lemm.), the predominant species, was colonized prodigiously compared to Jeffrey Pine (Pinus Jeffreyi Grev. and Balf.) and sugar Pine (Pinus lambertiana Dougl.). Across host species, pitch tube abundance was positively related to white fir prevalence and negatively related to tree species diversity. Bark beetles preferentially attacked trees of small to medium DBH in white fir and sugar Pine. Attack intensity in small Jeffrey Pine was positively correlated with stand basal area and biomass and that in sugar Pine of medium size was positively correlated with basal area also. Minor mistletoe infestations were detected in white fir along with incense-cedar (Libocedrus decurrens Torr.) and California red fir (Abies magnifica A. Murr.), with bark beetle colonization in the smallest and largest white fir positively related to the percentage of this fir thus infested. Mortality in white fir and Jeffrey Pine irrespective of size was positively correlated with the pitch tube count in the largest white fir regarding the former and with total tree count regarding the latter.
-
Evaluation of Mechanized Thinning and Prescribed Fire Effects on Long-Term Fuels Accumulations in Uneven-Aged Jeffrey Pine
Journal of Sustainable Forestry, 2014Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings implemented through cut-to-length and whole-tree harvesting followed by underburning were evaluated for their effects on long-term downed and dead fuels accumulations in pure, uneven-aged Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.) accompanied by isolated California white fir (Abies concolor var. lowiana [Gord.] Lemm.). Based on an initial inventory consisting of dry weight and fuel bed depth measurements conducted posttreatment, accumulations in the cut-to-length treatment were elevated according to most measures. Burned stand portions exhibited smaller quantities of fuels initially in individual timelag categories and in total as well as reduced fuel bed depths compared to their unburned counterparts except for the 1,000-hr fuels in the whole-tree treatment where postburn mortality of small stems nullified this effect. A linkage between initial mortality resulting from prescribed fire and final 1,000-hr fuels, as measured 8 yr later, was established but was probably attributable to comb...
-
Influences of Thinning and Underburning Restoration Practices on Red Turpentine Beetle Demography in Jeffrey Pine
Journal of Sustainable Forestry, 2014Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings implemented with cut-to-length and whole-tree harvesting systems followed by prescribed underburning were evaluated for their effects on red turpentine beetle (Dendroctonus valens LeConte) colonization in pure, uneven-aged Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.). Based on pitch tube abundance expressed as bole surface area-based counts, this beetle was significantly more prevalent where thinnings were implemented regardless of harvesting approach than in the unthinned treatment, but the population increases were confined to the burned stand portions. Substantial evidence indicated that fire-induced crown and bole damage culminating in compromised defense mechanisms elevated turpentine beetle colonization, and some evidence suggested a proclivity of this beetle to attack stems exhibiting general characteristics of low vigor, specifically smaller trees with weak crowns. Tree mortality was likely induced by the turpentine beetle infestation but was probably not its sole cause. The respon...
Dale W. Johnson - One of the best experts on this subject based on the ideXlab platform.
-
Elemental Ratios in Foliage and Soil of a Jeffrey Pine Stand Subjected to Thinning and Burning Restoration Practices
Forest Research: Open Access, 2016Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings accomplished through cut-to-length and whole-tree harvesting followed by a prescribed underburn were assessed for their influences on mineral nutrition in eastern Sierran Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.). As derived from foliar elemental concentrations determined at six samplings distributed over three growing seasons, molar Ca/Al, Mg/Al, K/Al, Ca/Mn, Mg/Mn, and K/Mn were generally higher in the unthinned treatment and lower in burned stand portions. Conducted under drought conditions, the driest phase of the study resulted in lower Ca/Al, Mg/Al, and K/Al and higher Ca/Mn and Ca/Zn when averaged across treatments. Foliar K/Mn, K/Zn, and K/Cu were generally lower in the early portion of the growing season compared to the late portion. At mid growing season, Mg/Al, K/Al, Mg/Mn, K/Mn, K/Fe, K/Zn, and K/Cu were higher in young needles while Ca/Al, Ca/Fe, Mg/Fe, Ca/Zn, Ca/Cu, and Mg/Cu were so in older ones. At mid study, soil Ca/Fe was higher in the unthinned treatment generally and especially in its unburned portion while K/Cu was higher overall in burned stand portions, most especially in the unthinned treatment. These findings provide insight into the interrelationships of base cations and metallic elements in forest nutrition as influenced by restoration practices.
-
Mechanized Thinning, Prescribed Fire, and Needle Age Influences on the Mineral Nutrition of Jeffrey Pine: Elemental Concentrations in Foliage and Soil
Forest Research: Open Access, 2016Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings using cut-to-length and whole-tree harvesting approaches followed by prescription underburning were assessed for their influences over multiple growing seasons on the mineral nutrition of Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.) on a Sierran site. Specifically examined were foliar and soil elemental concentrations encompassing macronutrients and micronutrients plus Al. Foliar N was higher in thinned stand subunits initially before transitioning to a relatively elevated concentration in the burned portion of either the cut-to-length or wholetree subunits, while higher foliar S in the burned cut-to-length treatment combination was evident in the last two of the six sampling periods. Foliar Mn was usually higher in the burned whole-tree combination while B and Al were often higher in burned stand portions but with less specificity regarding thinning treatment. At mid growing season, N, P, K, S, Fe, and Cu were higher in young needles while Ca, Mn, and Al were so in older ones. Near mid study, mineral soil Ca was higher in the unthinned subunit while Mg, Fe, Mn, Zn, and Cu were higher in unburned stand portions.
-
Bark Beetle Demography in Sierra Nevada Mixed Conifer: Variability and Influencing Factors
Forest Research: Open Access, 2015Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Multiple forest health variables were examined in an eastern Sierra Nevada mixed conifer stand, principal among them bark beetle demography. As indicated by pitch tube counts, California white fir (Abies concolor var. lowiana [Gord.] Lemm.), the predominant species, was colonized prodigiously compared to Jeffrey Pine (Pinus Jeffreyi Grev. and Balf.) and sugar Pine (Pinus lambertiana Dougl.). Across host species, pitch tube abundance was positively related to white fir prevalence and negatively related to tree species diversity. Bark beetles preferentially attacked trees of small to medium DBH in white fir and sugar Pine. Attack intensity in small Jeffrey Pine was positively correlated with stand basal area and biomass and that in sugar Pine of medium size was positively correlated with basal area also. Minor mistletoe infestations were detected in white fir along with incense-cedar (Libocedrus decurrens Torr.) and California red fir (Abies magnifica A. Murr.), with bark beetle colonization in the smallest and largest white fir positively related to the percentage of this fir thus infested. Mortality in white fir and Jeffrey Pine irrespective of size was positively correlated with the pitch tube count in the largest white fir regarding the former and with total tree count regarding the latter.
-
Evaluation of Mechanized Thinning and Prescribed Fire Effects on Long-Term Fuels Accumulations in Uneven-Aged Jeffrey Pine
Journal of Sustainable Forestry, 2014Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings implemented through cut-to-length and whole-tree harvesting followed by underburning were evaluated for their effects on long-term downed and dead fuels accumulations in pure, uneven-aged Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.) accompanied by isolated California white fir (Abies concolor var. lowiana [Gord.] Lemm.). Based on an initial inventory consisting of dry weight and fuel bed depth measurements conducted posttreatment, accumulations in the cut-to-length treatment were elevated according to most measures. Burned stand portions exhibited smaller quantities of fuels initially in individual timelag categories and in total as well as reduced fuel bed depths compared to their unburned counterparts except for the 1,000-hr fuels in the whole-tree treatment where postburn mortality of small stems nullified this effect. A linkage between initial mortality resulting from prescribed fire and final 1,000-hr fuels, as measured 8 yr later, was established but was probably attributable to comb...
-
Bark Beetle Demography in a Jeffrey Pine Stand as Influenced by Mechanized Thinning and Prescribed Fire
Journal of Sustainable Forestry, 2014Co-Authors: Roger F. Walker, Dale W. Johnson, Watkins W. Miller, Robert M. FeckoAbstract:Forest thinnings implemented with cut-to-length and whole-tree harvesting systems followed by underburning were evaluated for their effects on bark beetle prevalence in pure, uneven-aged Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.) interspersed with isolated California white fir (Abies concolor var. lowiana [Gord.] Lemm.). Based on pitch tube counts in a stand with a moderate bark beetle population in its Pine component, the Jeffrey Pine beetle (Dendroctonus Jeffreyi Hopkins) generally preferred larger trees before treatment implementation, but after exhibiting mixed pretreatment tendencies concerning stand density demonstrated a posttreatment proclivity toward higher density. Cut-to-length thinning followed by underburning increased the Pine beetle population while whole-tree thinning unaccompanied by burning reduced it. Tree mortality was induced by the bark beetle infestation but was not its sole cause. Pitch tube abundance on white fir far exceeded that on Jeffrey Pine, and the greatest influence on th...
Scott L. Stephens - One of the best experts on this subject based on the ideXlab platform.
-
Forest gap characteristics in old-growth Jeffrey Pine-mixed conifer forests in California and northwestern Mexico, where summaries were calculated in two ways: all gaps within the four ha study area (with edge gaps), and excluding gaps where more tha
2014Co-Authors: Danny L. Fry, Scott L. Stephens, Brandon M. Collins, Malcolm P. North, Ernesto Franco-vizcaíno, Samantha J. GillAbstract:Forest gap characteristics in old-growth Jeffrey Pine-mixed conifer forests in California and northwestern Mexico, where summaries were calculated in two ways: all gaps within the four ha study area (with edge gaps), and excluding gaps where more than 10% of the gap area overlapped the 5 m perimeter buffer (without edge gaps).
-
Proportion of trees within separate size classes in four old-growth Jeffrey Pine-mixed conifer forest sites.
2014Co-Authors: Danny L. Fry, Scott L. Stephens, Brandon M. Collins, Malcolm P. North, Ernesto Franco-vizcaíno, Samantha J. GillAbstract:Proportion of trees within separate size classes in four old-growth Jeffrey Pine-mixed conifer forest sites.
-
International Journal of Wildland Fire Editor in Chief
2013Co-Authors: Gwynfor Richards, Scott L. StephensAbstract:Fire history differences in adjacent Jeffrey Pine and upper montane forests in the eastern Sierra Nevad
-
stand level spatial dependence in an old growth Jeffrey Pine mixed conifer forest sierra san pedro martir mexico
Canadian Journal of Forest Research, 2010Co-Authors: Danny L. Fry, Scott L. StephensAbstract: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 influen...
-
Stand-level spatial dependence in an old-growth Jeffrey Pine – mixed conifer forest, Sierra San Pedro Mártir, Mexico
Canadian Journal of Forest Research, 2010Co-Authors: Danny L. Fry, Scott L. StephensAbstract: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 influen...
Robert M. Fecko - One of the best experts on this subject based on the ideXlab platform.
-
Mechanized Thinning, Prescribed Fire, and Needle Age Influences on the Mineral Nutrition of Jeffrey Pine: Elemental Concentrations in Foliage and Soil
Forest Research: Open Access, 2016Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings using cut-to-length and whole-tree harvesting approaches followed by prescription underburning were assessed for their influences over multiple growing seasons on the mineral nutrition of Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.) on a Sierran site. Specifically examined were foliar and soil elemental concentrations encompassing macronutrients and micronutrients plus Al. Foliar N was higher in thinned stand subunits initially before transitioning to a relatively elevated concentration in the burned portion of either the cut-to-length or wholetree subunits, while higher foliar S in the burned cut-to-length treatment combination was evident in the last two of the six sampling periods. Foliar Mn was usually higher in the burned whole-tree combination while B and Al were often higher in burned stand portions but with less specificity regarding thinning treatment. At mid growing season, N, P, K, S, Fe, and Cu were higher in young needles while Ca, Mn, and Al were so in older ones. Near mid study, mineral soil Ca was higher in the unthinned subunit while Mg, Fe, Mn, Zn, and Cu were higher in unburned stand portions.
-
Elemental Ratios in Foliage and Soil of a Jeffrey Pine Stand Subjected to Thinning and Burning Restoration Practices
Forest Research: Open Access, 2016Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings accomplished through cut-to-length and whole-tree harvesting followed by a prescribed underburn were assessed for their influences on mineral nutrition in eastern Sierran Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.). As derived from foliar elemental concentrations determined at six samplings distributed over three growing seasons, molar Ca/Al, Mg/Al, K/Al, Ca/Mn, Mg/Mn, and K/Mn were generally higher in the unthinned treatment and lower in burned stand portions. Conducted under drought conditions, the driest phase of the study resulted in lower Ca/Al, Mg/Al, and K/Al and higher Ca/Mn and Ca/Zn when averaged across treatments. Foliar K/Mn, K/Zn, and K/Cu were generally lower in the early portion of the growing season compared to the late portion. At mid growing season, Mg/Al, K/Al, Mg/Mn, K/Mn, K/Fe, K/Zn, and K/Cu were higher in young needles while Ca/Al, Ca/Fe, Mg/Fe, Ca/Zn, Ca/Cu, and Mg/Cu were so in older ones. At mid study, soil Ca/Fe was higher in the unthinned treatment generally and especially in its unburned portion while K/Cu was higher overall in burned stand portions, most especially in the unthinned treatment. These findings provide insight into the interrelationships of base cations and metallic elements in forest nutrition as influenced by restoration practices.
-
Bark Beetle Demography in Sierra Nevada Mixed Conifer: Variability and Influencing Factors
Forest Research: Open Access, 2015Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Multiple forest health variables were examined in an eastern Sierra Nevada mixed conifer stand, principal among them bark beetle demography. As indicated by pitch tube counts, California white fir (Abies concolor var. lowiana [Gord.] Lemm.), the predominant species, was colonized prodigiously compared to Jeffrey Pine (Pinus Jeffreyi Grev. and Balf.) and sugar Pine (Pinus lambertiana Dougl.). Across host species, pitch tube abundance was positively related to white fir prevalence and negatively related to tree species diversity. Bark beetles preferentially attacked trees of small to medium DBH in white fir and sugar Pine. Attack intensity in small Jeffrey Pine was positively correlated with stand basal area and biomass and that in sugar Pine of medium size was positively correlated with basal area also. Minor mistletoe infestations were detected in white fir along with incense-cedar (Libocedrus decurrens Torr.) and California red fir (Abies magnifica A. Murr.), with bark beetle colonization in the smallest and largest white fir positively related to the percentage of this fir thus infested. Mortality in white fir and Jeffrey Pine irrespective of size was positively correlated with the pitch tube count in the largest white fir regarding the former and with total tree count regarding the latter.
-
Evaluation of Mechanized Thinning and Prescribed Fire Effects on Long-Term Fuels Accumulations in Uneven-Aged Jeffrey Pine
Journal of Sustainable Forestry, 2014Co-Authors: Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. MillerAbstract:Forest thinnings implemented through cut-to-length and whole-tree harvesting followed by underburning were evaluated for their effects on long-term downed and dead fuels accumulations in pure, uneven-aged Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.) accompanied by isolated California white fir (Abies concolor var. lowiana [Gord.] Lemm.). Based on an initial inventory consisting of dry weight and fuel bed depth measurements conducted posttreatment, accumulations in the cut-to-length treatment were elevated according to most measures. Burned stand portions exhibited smaller quantities of fuels initially in individual timelag categories and in total as well as reduced fuel bed depths compared to their unburned counterparts except for the 1,000-hr fuels in the whole-tree treatment where postburn mortality of small stems nullified this effect. A linkage between initial mortality resulting from prescribed fire and final 1,000-hr fuels, as measured 8 yr later, was established but was probably attributable to comb...
-
Bark Beetle Demography in a Jeffrey Pine Stand as Influenced by Mechanized Thinning and Prescribed Fire
Journal of Sustainable Forestry, 2014Co-Authors: Roger F. Walker, Dale W. Johnson, Watkins W. Miller, Robert M. FeckoAbstract:Forest thinnings implemented with cut-to-length and whole-tree harvesting systems followed by underburning were evaluated for their effects on bark beetle prevalence in pure, uneven-aged Jeffrey Pine (Pinus Jeffreyi Grev. & Balf.) interspersed with isolated California white fir (Abies concolor var. lowiana [Gord.] Lemm.). Based on pitch tube counts in a stand with a moderate bark beetle population in its Pine component, the Jeffrey Pine beetle (Dendroctonus Jeffreyi Hopkins) generally preferred larger trees before treatment implementation, but after exhibiting mixed pretreatment tendencies concerning stand density demonstrated a posttreatment proclivity toward higher density. Cut-to-length thinning followed by underburning increased the Pine beetle population while whole-tree thinning unaccompanied by burning reduced it. Tree mortality was induced by the bark beetle infestation but was not its sole cause. Pitch tube abundance on white fir far exceeded that on Jeffrey Pine, and the greatest influence on th...