Julie Whitbeck | National Park Service (original) (raw)
Papers by Julie Whitbeck
Bulletin of the Ecological Society of America; (United States), Jun 1, 1994
Employing the annual herb Hemizonia luzulaefolia, native to nutrient limited grassland ecosystem ... more Employing the annual herb Hemizonia luzulaefolia, native to nutrient limited grassland ecosystem in California, and a community of indigenous vesicular-arbuscular mycorrhizal (VAM) fungi, this study examined mycorrhizal response to interacting plant- and fungus-acquired resources. Plant carbon supply was manipulated through atmospheric carbon dioxide (CO[sub 2]) concentration, and substrate phosphorus (P) supply was varied in the nutrient solution. H. luzulaefolia responded strongly to VAM association, showing increased root and shoot biomass, greater leaf area, higher shoot P content and lower specific root length relative to non-mycorrhizal plants. Elevated (700 ppm) CO[sub 2] plants had lower mass, lower root:shoot ratios and slightly greater specific root length than ambient pCO[sub 2]-grown plants. VAM colonization of roots was stimulated by elevated CO[sub 2] early in the experiment. Low P plants showed greater leaf mass per area and lower shoot P concentration than plus-P plants. P effects on measures of VAM changed over time. While ambient pCO[sub 2]-grown plants responsed to added P with increased biomass, plants grown at elevated CO[sub 2] showed equivalent or lower biomass in plus-P treatments than in those with no added P. At the same time, ambient pCO[sub 2]-grown plants developed greater VAM colonization of roots in low P treatments,more » while at 700 ppm CO[sub 2]. VAM colonization was higher in plus-P treatments. It appears that atmospheric pCO[sub 2] affects the patterns of belowground allocation in H. luzulaefolia: ambient pCO[sub 2] plants direct carbon resources to VAM when P is low and to roots when P is available, while elevated CO[sub 2] plants maintain VAM colonization regardless of P environment and allocate to roots when P is low.« less
Bulletin of the Ecological Society of America; (United States), Jun 1, 1993
I measured four aspects of mycorrhizal ecology (vesicular-arbuscular mycorrhizal [VAM] root lengt... more I measured four aspects of mycorrhizal ecology (vesicular-arbuscular mycorrhizal [VAM] root length, percent root colonized, intraradical concentration of the mycorrhizal fungal membrane sterol ergosterol, and substrate spore density) in three experimental systems, each with treatments at ambient ( 350ppm) and twice ambient (700ppm) atmospheric CO[sub 2]. The systems differ in degree of manipulation, ranging from a single species grown in sand in controlled environment chambers, to intact grassland ecosystem plots enclosed in ventilated open-top chambers, and including single to six species serpentine substrate profile. While elevated CO[sub 2] increased all measures of mycorrhizal activity in the most controlled system, it appeared to have no effect on these properties in the intact serpentine grassland ecosystem. Ongoing examination of the intermediate microcosm systems may elucidate whether plant species or substrate properties (such as microbial communities) are responsible for these observed differences in mycorrhizal response.
Water, 2021
The acquisition of reliable and accurate data to assess environmental changes over large spatial ... more The acquisition of reliable and accurate data to assess environmental changes over large spatial scales is one of the main limitations to determine the impact of eutrophication, and the effectiveness of management strategies in coastal systems. Here, we used a continuous in situ Chl-a fluorometry sensor and L8/OLI satellite data to develop an algorithm and map Chl-a spatial distribution to assess the impact of freshwater diversions and associated high nutrient loading rates in the Barataria Basin (BB) complex, a coastal system in the northern Gulf of Mexico. We collected water quality samples at 24 sampling stations and high-frequency continuous fluorometry in situ [Chl-a] data along a ~87 km transect from 2019–2020. Field [Chl-a] values were highly correlated (r = 0.86; p < 0.0001) with continuous in situ [Chl-a] fluorometry values. These continuous in situ [Chl-a] values were significantly related to a surface reflectance ratio ([B1 + B4]/B3) estimated using L8/OLI data (expone...
Wetlands, 2009
This report documents changes in forest structure and growth potential of dominant trees in salt-... more This report documents changes in forest structure and growth potential of dominant trees in salt-impacted tidal and non-tidal baldcypress wetlands of the southeastern United States. We inventoried basal area and tree height, and monitored incremental growth (in basal area) of codominant baldcypress (Taxodium distichum) trees monthly, for over four years, to examine the interrelationships among growth, site fertility, and soil physico-chemical characteristics. We found that salinity, soil total nitrogen (TN), flood duration, and flood frequency affected forest structure and growth the greatest. While mean annual site salinity ranged from 0.1 to 3.4 ppt, sites with salinity concentrations of 1.3 ppt or greater supported a basal area of less than 40 m 2 /ha. Where salinity was , 0.7 ppt, basal area was as high as 87 m 2 /ha. Stand height was also negatively affected by higher salinity. However, salinity related only to soil TN concentrations or to the relative balance between soil TN and total phosphorus (TP), which reached a maximum concentration between 1.2 and 2.0 ppt salinity. As estuarine influence shifts inland with sea-level rise, forest growth may become more strongly linked to salinity, not only due to salt effects but also as a consequence of site nitrogen imbalance.
Water, 2021
The acquisition of reliable and accurate data to assess environmental changes over large spatial ... more The acquisition of reliable and accurate data to assess environmental changes over large spatial scales is one of the main limitations to determine the impact of eutrophication, and the effectiveness of management strategies in coastal systems. Here, we used a continuous in situ Chl-a fluorometry sensor and L8/OLI satellite data to develop an algorithm and map Chl-a spatial distribution to assess the impact of freshwater diversions and associated high nutrient loading rates in the Barataria Basin (BB) complex, a coastal system in the northern Gulf of Mexico. We collected water quality samples at 24 sampling stations and high-frequency continuous fluorometry in situ [Chl-a] data along a ~87 km transect from 2019–2020. Field [Chl-a] values were highly correlated (r = 0.86; p < 0.0001) with continuous in situ [Chl-a] fluorometry values. These continuous in situ [Chl-a] values were significantly related to a surface reflectance ratio ([B1 + B4]/B3) estimated using L8/OLI data (expone...
1 Introduction 2 Root life history and dynamics 3 The flux of carbon from roots to rhizosphere so... more 1 Introduction 2 Root life history and dynamics 3 The flux of carbon from roots to rhizosphere soil 4 Microbial communities and their activity in the rhizosphere 5 Rhizosphere microfauna 6 Plant residues and their influence on soil physical properties 7 Mycorrhizas - symbiotic mediators of rhizosphere and ecosystem processes 8 Elevated CO2 and links between carbon and nutrient cycling 9 Rhizospheres: keys to formation and function of highly weathered soils 10 Plant root systems in a changing world 11 The rhizosphere in agricultural ecosystems 12 Soil rhizosphere food webs, their stability, and implications for soil processes in ecosystems
PLOS ONE
Wetlands along upper estuaries are characterized by dynamic transitions between forested and herb... more Wetlands along upper estuaries are characterized by dynamic transitions between forested and herbaceous communities (marsh) as salinity, hydroperiod, and nutrients change. The importance of belowground net primary productivity (BNPP) associated with fine and coarse root growth also changes but remains the dominant component of overall productivity in these important blue carbon wetlands. Appropriate BNPP assessment techniques to use in various tidal wetlands are not well-defined, and could make a difference in BNPP estimation. We hypothesized that different BNPP techniques applied among tidal wetlands differ in estimation of BNPP and possibly also correlate differently with porewater nutrient concentrations. We compare 6-month and 12-month root ingrowth, serial soil coring techniques utilizing two different calculations, and a mass balance approach (TBCA, Total Belowground Carbon Allocation) among four tidal wetland types along each of two river systems transitioning from freshwater...
Global Biogeochemical Cycles
Canadian Journal of Botany
Myrica gale L. plants were inoculated with Frankia strain HFP M+g15 and grown for 28 days with ro... more Myrica gale L. plants were inoculated with Frankia strain HFP M+g15 and grown for 28 days with root systems exposed to 2, 5, 10, 21, and 40 kPa O2. Plant growth was similar under all treatments, except for a small decrease in final size of plants at 2 kPa O2. At the end of the experiment nitrogenase activity of representative plants was analyzed over a variety of Po2 levels using an open-flow cuvette. Optimum nitrogenase activity was found at Po2 levels close to the growth Po2 in all cases and plants showed no short-term adaptation to oxygen. Specific activity of maximum nitrogenase was similar for all treatments, being within a factor of two. Nitrogenase activity showed rapid transient responses to step shifts in Po2 during assay and irreversible decline in activity at Po2 levels above optimum. Morphological responses to changing Po2 include a dramatic increase in nodule-root growth, inversely proportional to ambient Po2, and a variety of internal structural changes reducing nodule...
Sssaj, 2007
... I. Cardon, Zoe G. II. ... Function 133 6.4 The Future of the Rhizosphere in Ecological Agricu... more ... I. Cardon, Zoe G. II. ... Function 133 6.4 The Future of the Rhizosphere in Ecological Agriculture 145 Conclusions 148 References 148 7 The Contribution of RootRhizosphere Interactions to Biogeochemical Cycles in a Changing World Kurt S. Pregitzer, Donald R. Zak, Wendy M ...
Bulletin of the Ecological Society of America, 2006
... This year we look forward to the Friday morn‑ ing symposium, Returning soils to restoration ... more ... This year we look forward to the Friday morn‑ ing symposium, Returning soils to restoration ecol‑ ogy: rethinking the trade of structure for function, organized by Mac Callaham and Christine Hawkes. ... Submitted by: Julie Whitbeck STATISTICAL ECOLOGY SECTION ...
Canadian Journal of Botany
ABSTRACT
Background/Question/Methods Over the next century rising sea level will move the land/sea interfa... more Background/Question/Methods Over the next century rising sea level will move the land/sea interface inland, exposing coastal ecosystems to increasing tidal influence including increased flooding frequency and salinity. We want to understand how these environmental changes will modify coastal forest structure, productivity and carbon cycling. Many southeastern US coastal plain rivers have already experienced shifts in extent of tidal influence due to human hydrologic modifications. Employing this gradient of tidal influence as a proxy for rising sea level, we investigate these impacts in cypress swamps located along the intensively modified lower Savannah River. Utilizing monthly censuses of fine root populations growing adjacent to minirhizotron tubes, we employ a demographic approach to quantify patterns of root distribution, morphology and production. We combine these with measures of aboveground production and monthly surface flux assays of soil respiration to compose a carbon cy...
Seasonally Dry Tropical Forests, 1995
Wetlands, 2012
... 1 Location of study sites along the lower Savannah River floodplain in relation to marsh, pri... more ... 1 Location of study sites along the lower Savannah River floodplain in relation to marsh, primary river braids, and dredged access channels to marsh from an era when ... constructed using a 2-cm Pt tip welded to Cu wire and sealed with an epoxy for waterproofing (Faulkner et al. ...
The Quarterly Review of Biology, 1998
Restoration Ecology, 2004
Bulletin of the Ecological Society of America; (United States), Jun 1, 1994
Employing the annual herb Hemizonia luzulaefolia, native to nutrient limited grassland ecosystem ... more Employing the annual herb Hemizonia luzulaefolia, native to nutrient limited grassland ecosystem in California, and a community of indigenous vesicular-arbuscular mycorrhizal (VAM) fungi, this study examined mycorrhizal response to interacting plant- and fungus-acquired resources. Plant carbon supply was manipulated through atmospheric carbon dioxide (CO[sub 2]) concentration, and substrate phosphorus (P) supply was varied in the nutrient solution. H. luzulaefolia responded strongly to VAM association, showing increased root and shoot biomass, greater leaf area, higher shoot P content and lower specific root length relative to non-mycorrhizal plants. Elevated (700 ppm) CO[sub 2] plants had lower mass, lower root:shoot ratios and slightly greater specific root length than ambient pCO[sub 2]-grown plants. VAM colonization of roots was stimulated by elevated CO[sub 2] early in the experiment. Low P plants showed greater leaf mass per area and lower shoot P concentration than plus-P plants. P effects on measures of VAM changed over time. While ambient pCO[sub 2]-grown plants responsed to added P with increased biomass, plants grown at elevated CO[sub 2] showed equivalent or lower biomass in plus-P treatments than in those with no added P. At the same time, ambient pCO[sub 2]-grown plants developed greater VAM colonization of roots in low P treatments,more » while at 700 ppm CO[sub 2]. VAM colonization was higher in plus-P treatments. It appears that atmospheric pCO[sub 2] affects the patterns of belowground allocation in H. luzulaefolia: ambient pCO[sub 2] plants direct carbon resources to VAM when P is low and to roots when P is available, while elevated CO[sub 2] plants maintain VAM colonization regardless of P environment and allocate to roots when P is low.« less
Bulletin of the Ecological Society of America; (United States), Jun 1, 1993
I measured four aspects of mycorrhizal ecology (vesicular-arbuscular mycorrhizal [VAM] root lengt... more I measured four aspects of mycorrhizal ecology (vesicular-arbuscular mycorrhizal [VAM] root length, percent root colonized, intraradical concentration of the mycorrhizal fungal membrane sterol ergosterol, and substrate spore density) in three experimental systems, each with treatments at ambient ( 350ppm) and twice ambient (700ppm) atmospheric CO[sub 2]. The systems differ in degree of manipulation, ranging from a single species grown in sand in controlled environment chambers, to intact grassland ecosystem plots enclosed in ventilated open-top chambers, and including single to six species serpentine substrate profile. While elevated CO[sub 2] increased all measures of mycorrhizal activity in the most controlled system, it appeared to have no effect on these properties in the intact serpentine grassland ecosystem. Ongoing examination of the intermediate microcosm systems may elucidate whether plant species or substrate properties (such as microbial communities) are responsible for these observed differences in mycorrhizal response.
Water, 2021
The acquisition of reliable and accurate data to assess environmental changes over large spatial ... more The acquisition of reliable and accurate data to assess environmental changes over large spatial scales is one of the main limitations to determine the impact of eutrophication, and the effectiveness of management strategies in coastal systems. Here, we used a continuous in situ Chl-a fluorometry sensor and L8/OLI satellite data to develop an algorithm and map Chl-a spatial distribution to assess the impact of freshwater diversions and associated high nutrient loading rates in the Barataria Basin (BB) complex, a coastal system in the northern Gulf of Mexico. We collected water quality samples at 24 sampling stations and high-frequency continuous fluorometry in situ [Chl-a] data along a ~87 km transect from 2019–2020. Field [Chl-a] values were highly correlated (r = 0.86; p < 0.0001) with continuous in situ [Chl-a] fluorometry values. These continuous in situ [Chl-a] values were significantly related to a surface reflectance ratio ([B1 + B4]/B3) estimated using L8/OLI data (expone...
Wetlands, 2009
This report documents changes in forest structure and growth potential of dominant trees in salt-... more This report documents changes in forest structure and growth potential of dominant trees in salt-impacted tidal and non-tidal baldcypress wetlands of the southeastern United States. We inventoried basal area and tree height, and monitored incremental growth (in basal area) of codominant baldcypress (Taxodium distichum) trees monthly, for over four years, to examine the interrelationships among growth, site fertility, and soil physico-chemical characteristics. We found that salinity, soil total nitrogen (TN), flood duration, and flood frequency affected forest structure and growth the greatest. While mean annual site salinity ranged from 0.1 to 3.4 ppt, sites with salinity concentrations of 1.3 ppt or greater supported a basal area of less than 40 m 2 /ha. Where salinity was , 0.7 ppt, basal area was as high as 87 m 2 /ha. Stand height was also negatively affected by higher salinity. However, salinity related only to soil TN concentrations or to the relative balance between soil TN and total phosphorus (TP), which reached a maximum concentration between 1.2 and 2.0 ppt salinity. As estuarine influence shifts inland with sea-level rise, forest growth may become more strongly linked to salinity, not only due to salt effects but also as a consequence of site nitrogen imbalance.
Water, 2021
The acquisition of reliable and accurate data to assess environmental changes over large spatial ... more The acquisition of reliable and accurate data to assess environmental changes over large spatial scales is one of the main limitations to determine the impact of eutrophication, and the effectiveness of management strategies in coastal systems. Here, we used a continuous in situ Chl-a fluorometry sensor and L8/OLI satellite data to develop an algorithm and map Chl-a spatial distribution to assess the impact of freshwater diversions and associated high nutrient loading rates in the Barataria Basin (BB) complex, a coastal system in the northern Gulf of Mexico. We collected water quality samples at 24 sampling stations and high-frequency continuous fluorometry in situ [Chl-a] data along a ~87 km transect from 2019–2020. Field [Chl-a] values were highly correlated (r = 0.86; p < 0.0001) with continuous in situ [Chl-a] fluorometry values. These continuous in situ [Chl-a] values were significantly related to a surface reflectance ratio ([B1 + B4]/B3) estimated using L8/OLI data (expone...
1 Introduction 2 Root life history and dynamics 3 The flux of carbon from roots to rhizosphere so... more 1 Introduction 2 Root life history and dynamics 3 The flux of carbon from roots to rhizosphere soil 4 Microbial communities and their activity in the rhizosphere 5 Rhizosphere microfauna 6 Plant residues and their influence on soil physical properties 7 Mycorrhizas - symbiotic mediators of rhizosphere and ecosystem processes 8 Elevated CO2 and links between carbon and nutrient cycling 9 Rhizospheres: keys to formation and function of highly weathered soils 10 Plant root systems in a changing world 11 The rhizosphere in agricultural ecosystems 12 Soil rhizosphere food webs, their stability, and implications for soil processes in ecosystems
PLOS ONE
Wetlands along upper estuaries are characterized by dynamic transitions between forested and herb... more Wetlands along upper estuaries are characterized by dynamic transitions between forested and herbaceous communities (marsh) as salinity, hydroperiod, and nutrients change. The importance of belowground net primary productivity (BNPP) associated with fine and coarse root growth also changes but remains the dominant component of overall productivity in these important blue carbon wetlands. Appropriate BNPP assessment techniques to use in various tidal wetlands are not well-defined, and could make a difference in BNPP estimation. We hypothesized that different BNPP techniques applied among tidal wetlands differ in estimation of BNPP and possibly also correlate differently with porewater nutrient concentrations. We compare 6-month and 12-month root ingrowth, serial soil coring techniques utilizing two different calculations, and a mass balance approach (TBCA, Total Belowground Carbon Allocation) among four tidal wetland types along each of two river systems transitioning from freshwater...
Global Biogeochemical Cycles
Canadian Journal of Botany
Myrica gale L. plants were inoculated with Frankia strain HFP M+g15 and grown for 28 days with ro... more Myrica gale L. plants were inoculated with Frankia strain HFP M+g15 and grown for 28 days with root systems exposed to 2, 5, 10, 21, and 40 kPa O2. Plant growth was similar under all treatments, except for a small decrease in final size of plants at 2 kPa O2. At the end of the experiment nitrogenase activity of representative plants was analyzed over a variety of Po2 levels using an open-flow cuvette. Optimum nitrogenase activity was found at Po2 levels close to the growth Po2 in all cases and plants showed no short-term adaptation to oxygen. Specific activity of maximum nitrogenase was similar for all treatments, being within a factor of two. Nitrogenase activity showed rapid transient responses to step shifts in Po2 during assay and irreversible decline in activity at Po2 levels above optimum. Morphological responses to changing Po2 include a dramatic increase in nodule-root growth, inversely proportional to ambient Po2, and a variety of internal structural changes reducing nodule...
Sssaj, 2007
... I. Cardon, Zoe G. II. ... Function 133 6.4 The Future of the Rhizosphere in Ecological Agricu... more ... I. Cardon, Zoe G. II. ... Function 133 6.4 The Future of the Rhizosphere in Ecological Agriculture 145 Conclusions 148 References 148 7 The Contribution of RootRhizosphere Interactions to Biogeochemical Cycles in a Changing World Kurt S. Pregitzer, Donald R. Zak, Wendy M ...
Bulletin of the Ecological Society of America, 2006
... This year we look forward to the Friday morn‑ ing symposium, Returning soils to restoration ... more ... This year we look forward to the Friday morn‑ ing symposium, Returning soils to restoration ecol‑ ogy: rethinking the trade of structure for function, organized by Mac Callaham and Christine Hawkes. ... Submitted by: Julie Whitbeck STATISTICAL ECOLOGY SECTION ...
Canadian Journal of Botany
ABSTRACT
Background/Question/Methods Over the next century rising sea level will move the land/sea interfa... more Background/Question/Methods Over the next century rising sea level will move the land/sea interface inland, exposing coastal ecosystems to increasing tidal influence including increased flooding frequency and salinity. We want to understand how these environmental changes will modify coastal forest structure, productivity and carbon cycling. Many southeastern US coastal plain rivers have already experienced shifts in extent of tidal influence due to human hydrologic modifications. Employing this gradient of tidal influence as a proxy for rising sea level, we investigate these impacts in cypress swamps located along the intensively modified lower Savannah River. Utilizing monthly censuses of fine root populations growing adjacent to minirhizotron tubes, we employ a demographic approach to quantify patterns of root distribution, morphology and production. We combine these with measures of aboveground production and monthly surface flux assays of soil respiration to compose a carbon cy...
Seasonally Dry Tropical Forests, 1995
Wetlands, 2012
... 1 Location of study sites along the lower Savannah River floodplain in relation to marsh, pri... more ... 1 Location of study sites along the lower Savannah River floodplain in relation to marsh, primary river braids, and dredged access channels to marsh from an era when ... constructed using a 2-cm Pt tip welded to Cu wire and sealed with an epoxy for waterproofing (Faulkner et al. ...
The Quarterly Review of Biology, 1998
Restoration Ecology, 2004