Kimberli Scott - Academia.edu (original) (raw)

Papers by Kimberli Scott

Research paper thumbnail of Impact of Oils Sands Mining on Nitrogen-Limited Peatland Ecosystems in Alberta Canada

Peatlands of boreal Canada represent large reservoirs of sequestered carbon (C) and nitrogen (N).... more Peatlands of boreal Canada represent large reservoirs of sequestered carbon (C) and nitrogen (N). Cycling of C and N in peatlands is intrinsically linked, especially in bogs - peatlands isolated from ground- and surface-water inputs, receiving nutrients exclusively from the atmosphere, which in the absence of N pollution, ensures an N-limited, nutrient-poor ecosystem. A growing concern associated with the development

Research paper thumbnail of Bog Plant Tissue Chemistry as Indicators of Regionally Elevated Atmospheric N and S Deposition in the Alberta Oil Sands Region

ABSTRACT Nitrogen oxide and sulfur oxide emission from ongoing development of oil sands in northe... more ABSTRACT Nitrogen oxide and sulfur oxide emission from ongoing development of oil sands in northern Alberta results in regionally elevated atmospheric deposition of N and S in an area where background deposition of both N and S is exceptionally low (less than 1 kg/ha/yr). Because bogs, which represent major landforms in the Alberta oil sands region, are believed to be N-limited and potentially sensitive to S inputs, we have been investigating the effects of elevated N deposition on C, N, and S cycling in bogs, as well as the potential of bogs to serve as monitors of N and S deposition. Toward this latter end, we have measured seasonal variation (5 sampling dates between June and October 2009) concentrations of N and S, as well as δ15N value, in leaf tissues (Picea mariana (ectomycorrhizal); Ledum groenlandicum, Oxycoccos microcarpon, Vaccinium vitis-idaea (ericoid mycorrhizal); Rubus chamaemorus, and Smilacina trifolia (nonmycorrhizal), Sphagnum (S. fuscum, S. capillifolium, S. magellanicum, S. angustifolium) moss capitula (top 1-cm of plant) and lichens (Cladina mitis and Evernia mesomorpha) at 5 bogs at distances ranging from 14 to 300 km from the heart of the oil sands mining area. Averaged across all sites and sampling dates, N concentrations in ectomycorrhizal, ericoid mycorrhizal, nonmycorrhizal, Sphagnum, and lichens was 8.6 + 0.2, 11.9 + 0.2, 26.3 + 0.6, 10.2 + 0.1, 7.2 + 0.2 mg/g, respectively; δ15N values were -10.3 + 0.1, -6.0 + 0.1, 1.7 + 0.2, -5.3 + 0.1, -4.7 + 0.1 mg/g, respectively, and S concentrations were 1.07 + 0.2, 1.31 + 0.2, 1.94 + 0.6, 1.46 + 0.2, 1.11 + 0.3 mg/g, respectively. Plant functional groups and individual species behaved differently with respect to both seasonal variation and site differences, often with significant interactions when analyzed using two-way analyses of variance. Some species exhibited seasonal variation in some aspects of plant tissue chemistry, while others did not; when a species did exhibit seasonal variation, the variation was rather consistent between sites. More importantly, however, canonical discriminant analysis (with potential variables of C, N, or S concentrations, C:N, C:S, or N:S ratios, and δ15N values) indicated that the five sites can be differentiated based on plant tissue chemistry, most clearly separating the site closest and the site farthest from the oil sands mining area. The first canonical axis explained between 66 and 91 percent of the overall variation, but the variables that were significantly correlated with the first canonical axis differed between species. We conclude that plant tissue chemistry exhibited a significant variation between plant functional groups, between species, between sites, and seasonally. Some of this variation appears to be related to distance from the heart of oil sands mining activity in northern Alberta, possibly reflecting regionally elevated atmospheric deposition of N and S. Bog plants, through analysis of tissue chemistry, have the potential to serve as biomonitors of the anticipated spread of elevated atmospheric N and S deposition as oil sands development continues to grow in northern Alberta.

Research paper thumbnail of Relationships between NEP and water table position in a western Canadian poor fen during a wet and a dry year

Water table position (WT) is an important factor in peatland ecosystem structure and function. Th... more Water table position (WT) is an important factor in peatland ecosystem structure and function. The relationship between WT and net ecosystem production (NEP) is recognized, but poorly described, especially on a microscale level where factors such as vegetation and microhabitat may influence this relationship. Over two growing seasons, fluxes of CO2 and CH4, coupled with measurements of WT, were examined

Research paper thumbnail of Disturbance and the peatland carbon sink in the Oil Sands Administrative Area

Attaining Sustainable Development, 2012

Research paper thumbnail of Living on the Edge: The Effects of Drought on Canada's Western Boreal Peatlands

Bryophyte Ecology and Climate Change, 2009

Research paper thumbnail of N2-fixation by methanotrophs sustains carbon and nitrogen accumulation in pristine peatlands

Biogeochemistry, 2014

Symbiotic relationships between N 2 -fixing prokaryotes and their autotrophic hosts are essential... more Symbiotic relationships between N 2 -fixing prokaryotes and their autotrophic hosts are essential in nitrogen (N)-limited ecosystems, yet the importance of this association in pristine boreal peatlands, which store 25 % of the world's soil (C), has been overlooked. External inputs of N to bogs are predominantly atmospheric, and given that regions of boreal Canada anchor some of the lowest rates found globally (*1 kg N ha -1 year -1 ), biomass production is thought to be limited primarily by N. Despite historically low N deposition, we show that boreal bogs have accumulated approximately 12-25 times more N than can be explained by atmospheric inputs.

Research paper thumbnail of Postfire carbon balance in boreal bogs of Alberta, Canada

Global Change Biology, 2009

Boreal peatland ecosystems occupy about 3.5 million km 2 of the earth's land surface and store be... more Boreal peatland ecosystems occupy about 3.5 million km 2 of the earth's land surface and store between 250 and 455 Pg of carbon (C) as peat. While northern hemisphere boreal peatlands have functioned as net sinks for atmospheric C since the most recent deglaciation, natural and anthropogenic disturbances, and most importantly wildfire, may compromise peatland C sinks. To examine the effects of fire on local and regional C sink strength, we focused on a 12 000 km 2 region near Wabasca, AB, Canada, where ombrotrophic Sphagnum-dominated bogs cover 2280 km 2 that burn with a fire return interval of 123 AE 26 years. We characterized annual C accumulation along a chronosequence of 10 bog sites, spanning 1-102 years-since-fire (in 2002). Immediately after fire, bogs represent a net C source of 8.9 AE 8.4 mol m À2 yr À1 . At about 13 years after fire, bogs switch from net C sources to net C sinks, mainly because of recovery of the moss and shrub layers. Subsequently, black spruce biomass accumulation contributes to the net C sink, with fine root biomass accumulation peaking at 34 years after fire and aboveground biomass and coarse root accumulation peaking at 74 years after fire. The overall C sink strength peaks at 18.4 mol C m À2 yr À1 at 75 years after fire. As the tree biomass accumulation rate declines, the net C sink decreases to about 10 mol C m À2 yr À1 at 100 years-sincefire. We estimate that across the Wabasca study region, bogs currently represent a C sink of 14.7 AE 5.1 Gmol yr À1 . A decrease in the fire return interval to 61 years with no change in air temperature would convert the region's bogs to a net C source. An increase in nonwinter air temperature of 2 1C would decrease the regional C sink to 6.8 AE 2.3 Gmol yr À1 . Under scenarios of predicted climate change, the current C sink status of Alberta bogs is likely to diminish to the point where these peatlands become net sources of atmospheric CO 2 -C.

Research paper thumbnail of The disappearance of relict permafrost in boreal north America: Effects on peatland carbon storage and fluxes

Global Change Biology, 2007

Research paper thumbnail of Decomposition and Peat Accumulation in Rich Fens of Boreal Alberta, Canada

Ecosystems, 2009

Fens are important components of Canada's western boreal forests, occupying about 63% of the tota... more Fens are important components of Canada's western boreal forests, occupying about 63% of the total peatland area and storing about 65% of the peatland carbon. Rich fens, dominated by true moss-dominated ground layers, make up more than half of the fens in the region. We studied organic matter accumulation in three rich fens that represent the diversity in structural types. We used in situ decomposition socks, a new method that examines actual decomposition throughout the upper peat profile over an extended period of time. We coupled our carbon loss data with macrofossil analyses and dated peat profiles using 210 Pb. Across the three rich fens and in the top 39 cm of the peat column, dry mass increases on average 3.1 times. From our dry mass loss measurements, we calculate that annual mass loss from the top 39 cm varies from 0.52 to 1.08 kg m 2 . Vertical accumulation during the past 50 years has varied from 16 to 32 cm and during these 50 years, organic matter accumulation has averaged 174 g m -2 y -1 compared to 527 g m 2 y -1 dry mass loss, with additional mass losses of 306 g m 2 y -1 from peat between 50 and 150 years of age. Organic matter accumulation from our rich fens compares well with literature values from boreal bogs, whereas peat bulk densities increase about three times within the uppermost 40 cm, much more than in bogs. Hence, rich fens accumulate peat not because the plant material is especially hard to decompose, is acidic, or has the catotelm especially close to the surface, but because dense, rapidly produced inputs outweigh the relatively rapid decomposition process of the upper peat column.

Research paper thumbnail of Cosmogenic 10Be as a potential dating tool in peat

Biogeochemistry, 2010

Because ombrotrophic peat bogs receive inputs of water, nutrients, pollutants, and xerobiotic mat... more Because ombrotrophic peat bogs receive inputs of water, nutrients, pollutants, and xerobiotic materials solely from the atmosphere, and accumulate organic matter vertically, dated peat cores can provide a historical record of deposition. We propose a novel method for accurately determining dates of peat, based on cosmogenic 10 Be. In a laboratory study, we document limited post-depositional mobility of atmospherically-deposited Be, a requisite for 10 Be dating. We provide an example of how the 210 Pb-dated upper portion of a peat core can be used to back-calculate a site-specific 10 Be deposition rate, which can then be used to estimate dates for peat throughout a core, and also discuss limitations to the application of cosmogenic 10 Be to the dating of peat deposits.

Research paper thumbnail of Three-dimensional, bioactive, biodegradable, polymer-bioactive glass composite scaffolds with improved mechanical properties support collagen synthesis and mineralization of human osteoblast-like cellsin vitro

Journal of Biomedical Materials Research, 2003

In the past decade, tissue engineering-based bone grafting has emerged as a viable alternative to... more In the past decade, tissue engineering-based bone grafting has emerged as a viable alternative to biological and synthetic grafts. The biomaterial component is a critical determinant of the ultimate success of the tissueengineered graft. Because no single existing material possesses all the necessary properties required in an ideal bone graft, our approach has been to develop a three dimensional (3-D), porous composite of polylactide-co-glycolide (PLAGA) and 45S5 bioactive glass (BG) that is biodegradable, bioactive, and suitable as a scaffold for bone tissue engineering (PLAGA-BG composite). The objectives of this study were to examine the mechanical properties of a PLAGA-BG matrix, to evaluate the response of human osteoblast-like cells to the PLAGA-BG composite, and to evaluate the ability of the composite to form a surface calcium phosphate layer in vitro. Structural and mechanical properties of PLAGA-BG were measured, and the formation of a surface calcium phosphate layer was evaluated by surface analysis methods. The growth and differentiation of human osteoblast-like cells on PLAGA-BG were also examined. A hypothesis was that the combination of PLAGA with BG would result in a biocompatible and bioactive compos-ite, capable of supporting osteoblast adhesion, growth and differentiation, with mechanical properties superior to PLAGA alone. The addition of bioactive glass granules to the PLAGA matrix resulted in a structure with higher compressive modulus than PLAGA alone. Moreover, the PLAGA-BA composite was found to be a bioactive material, as it formed surface calcium phosphate deposits in a simulated body fluid (SBF), and in the presence of cells and serum proteins. The composite supported osteoblast-like morphology, stained positively for alkaline phosphatase, and supported higher levels of Type I collagen synthesis than tissue culture polystyrene controls. We have successfully developed a degradable, porous, polymer bioactive glass composite possessing improved mechanical properties and osteointegrative potential compared to degradable polymers of poly(lactic acid-glycolic acid) alone. Future work will focus on the optimization of the composite scaffold for bone tissue-engineering applications and the evaluation of the 3-D composite in an in vivo model.

Research paper thumbnail of Impact of Oils Sands Mining on Nitrogen-Limited Peatland Ecosystems in Alberta Canada

Peatlands of boreal Canada represent large reservoirs of sequestered carbon (C) and nitrogen (N).... more Peatlands of boreal Canada represent large reservoirs of sequestered carbon (C) and nitrogen (N). Cycling of C and N in peatlands is intrinsically linked, especially in bogs - peatlands isolated from ground- and surface-water inputs, receiving nutrients exclusively from the atmosphere, which in the absence of N pollution, ensures an N-limited, nutrient-poor ecosystem. A growing concern associated with the development

Research paper thumbnail of Bog Plant Tissue Chemistry as Indicators of Regionally Elevated Atmospheric N and S Deposition in the Alberta Oil Sands Region

ABSTRACT Nitrogen oxide and sulfur oxide emission from ongoing development of oil sands in northe... more ABSTRACT Nitrogen oxide and sulfur oxide emission from ongoing development of oil sands in northern Alberta results in regionally elevated atmospheric deposition of N and S in an area where background deposition of both N and S is exceptionally low (less than 1 kg/ha/yr). Because bogs, which represent major landforms in the Alberta oil sands region, are believed to be N-limited and potentially sensitive to S inputs, we have been investigating the effects of elevated N deposition on C, N, and S cycling in bogs, as well as the potential of bogs to serve as monitors of N and S deposition. Toward this latter end, we have measured seasonal variation (5 sampling dates between June and October 2009) concentrations of N and S, as well as δ15N value, in leaf tissues (Picea mariana (ectomycorrhizal); Ledum groenlandicum, Oxycoccos microcarpon, Vaccinium vitis-idaea (ericoid mycorrhizal); Rubus chamaemorus, and Smilacina trifolia (nonmycorrhizal), Sphagnum (S. fuscum, S. capillifolium, S. magellanicum, S. angustifolium) moss capitula (top 1-cm of plant) and lichens (Cladina mitis and Evernia mesomorpha) at 5 bogs at distances ranging from 14 to 300 km from the heart of the oil sands mining area. Averaged across all sites and sampling dates, N concentrations in ectomycorrhizal, ericoid mycorrhizal, nonmycorrhizal, Sphagnum, and lichens was 8.6 + 0.2, 11.9 + 0.2, 26.3 + 0.6, 10.2 + 0.1, 7.2 + 0.2 mg/g, respectively; δ15N values were -10.3 + 0.1, -6.0 + 0.1, 1.7 + 0.2, -5.3 + 0.1, -4.7 + 0.1 mg/g, respectively, and S concentrations were 1.07 + 0.2, 1.31 + 0.2, 1.94 + 0.6, 1.46 + 0.2, 1.11 + 0.3 mg/g, respectively. Plant functional groups and individual species behaved differently with respect to both seasonal variation and site differences, often with significant interactions when analyzed using two-way analyses of variance. Some species exhibited seasonal variation in some aspects of plant tissue chemistry, while others did not; when a species did exhibit seasonal variation, the variation was rather consistent between sites. More importantly, however, canonical discriminant analysis (with potential variables of C, N, or S concentrations, C:N, C:S, or N:S ratios, and δ15N values) indicated that the five sites can be differentiated based on plant tissue chemistry, most clearly separating the site closest and the site farthest from the oil sands mining area. The first canonical axis explained between 66 and 91 percent of the overall variation, but the variables that were significantly correlated with the first canonical axis differed between species. We conclude that plant tissue chemistry exhibited a significant variation between plant functional groups, between species, between sites, and seasonally. Some of this variation appears to be related to distance from the heart of oil sands mining activity in northern Alberta, possibly reflecting regionally elevated atmospheric deposition of N and S. Bog plants, through analysis of tissue chemistry, have the potential to serve as biomonitors of the anticipated spread of elevated atmospheric N and S deposition as oil sands development continues to grow in northern Alberta.

Research paper thumbnail of Relationships between NEP and water table position in a western Canadian poor fen during a wet and a dry year

Water table position (WT) is an important factor in peatland ecosystem structure and function. Th... more Water table position (WT) is an important factor in peatland ecosystem structure and function. The relationship between WT and net ecosystem production (NEP) is recognized, but poorly described, especially on a microscale level where factors such as vegetation and microhabitat may influence this relationship. Over two growing seasons, fluxes of CO2 and CH4, coupled with measurements of WT, were examined

Research paper thumbnail of Disturbance and the peatland carbon sink in the Oil Sands Administrative Area

Attaining Sustainable Development, 2012

Research paper thumbnail of Living on the Edge: The Effects of Drought on Canada's Western Boreal Peatlands

Bryophyte Ecology and Climate Change, 2009

Research paper thumbnail of N2-fixation by methanotrophs sustains carbon and nitrogen accumulation in pristine peatlands

Biogeochemistry, 2014

Symbiotic relationships between N 2 -fixing prokaryotes and their autotrophic hosts are essential... more Symbiotic relationships between N 2 -fixing prokaryotes and their autotrophic hosts are essential in nitrogen (N)-limited ecosystems, yet the importance of this association in pristine boreal peatlands, which store 25 % of the world's soil (C), has been overlooked. External inputs of N to bogs are predominantly atmospheric, and given that regions of boreal Canada anchor some of the lowest rates found globally (*1 kg N ha -1 year -1 ), biomass production is thought to be limited primarily by N. Despite historically low N deposition, we show that boreal bogs have accumulated approximately 12-25 times more N than can be explained by atmospheric inputs.

Research paper thumbnail of Postfire carbon balance in boreal bogs of Alberta, Canada

Global Change Biology, 2009

Boreal peatland ecosystems occupy about 3.5 million km 2 of the earth's land surface and store be... more Boreal peatland ecosystems occupy about 3.5 million km 2 of the earth's land surface and store between 250 and 455 Pg of carbon (C) as peat. While northern hemisphere boreal peatlands have functioned as net sinks for atmospheric C since the most recent deglaciation, natural and anthropogenic disturbances, and most importantly wildfire, may compromise peatland C sinks. To examine the effects of fire on local and regional C sink strength, we focused on a 12 000 km 2 region near Wabasca, AB, Canada, where ombrotrophic Sphagnum-dominated bogs cover 2280 km 2 that burn with a fire return interval of 123 AE 26 years. We characterized annual C accumulation along a chronosequence of 10 bog sites, spanning 1-102 years-since-fire (in 2002). Immediately after fire, bogs represent a net C source of 8.9 AE 8.4 mol m À2 yr À1 . At about 13 years after fire, bogs switch from net C sources to net C sinks, mainly because of recovery of the moss and shrub layers. Subsequently, black spruce biomass accumulation contributes to the net C sink, with fine root biomass accumulation peaking at 34 years after fire and aboveground biomass and coarse root accumulation peaking at 74 years after fire. The overall C sink strength peaks at 18.4 mol C m À2 yr À1 at 75 years after fire. As the tree biomass accumulation rate declines, the net C sink decreases to about 10 mol C m À2 yr À1 at 100 years-sincefire. We estimate that across the Wabasca study region, bogs currently represent a C sink of 14.7 AE 5.1 Gmol yr À1 . A decrease in the fire return interval to 61 years with no change in air temperature would convert the region's bogs to a net C source. An increase in nonwinter air temperature of 2 1C would decrease the regional C sink to 6.8 AE 2.3 Gmol yr À1 . Under scenarios of predicted climate change, the current C sink status of Alberta bogs is likely to diminish to the point where these peatlands become net sources of atmospheric CO 2 -C.

Research paper thumbnail of The disappearance of relict permafrost in boreal north America: Effects on peatland carbon storage and fluxes

Global Change Biology, 2007

Research paper thumbnail of Decomposition and Peat Accumulation in Rich Fens of Boreal Alberta, Canada

Ecosystems, 2009

Fens are important components of Canada's western boreal forests, occupying about 63% of the tota... more Fens are important components of Canada's western boreal forests, occupying about 63% of the total peatland area and storing about 65% of the peatland carbon. Rich fens, dominated by true moss-dominated ground layers, make up more than half of the fens in the region. We studied organic matter accumulation in three rich fens that represent the diversity in structural types. We used in situ decomposition socks, a new method that examines actual decomposition throughout the upper peat profile over an extended period of time. We coupled our carbon loss data with macrofossil analyses and dated peat profiles using 210 Pb. Across the three rich fens and in the top 39 cm of the peat column, dry mass increases on average 3.1 times. From our dry mass loss measurements, we calculate that annual mass loss from the top 39 cm varies from 0.52 to 1.08 kg m 2 . Vertical accumulation during the past 50 years has varied from 16 to 32 cm and during these 50 years, organic matter accumulation has averaged 174 g m -2 y -1 compared to 527 g m 2 y -1 dry mass loss, with additional mass losses of 306 g m 2 y -1 from peat between 50 and 150 years of age. Organic matter accumulation from our rich fens compares well with literature values from boreal bogs, whereas peat bulk densities increase about three times within the uppermost 40 cm, much more than in bogs. Hence, rich fens accumulate peat not because the plant material is especially hard to decompose, is acidic, or has the catotelm especially close to the surface, but because dense, rapidly produced inputs outweigh the relatively rapid decomposition process of the upper peat column.

Research paper thumbnail of Cosmogenic 10Be as a potential dating tool in peat

Biogeochemistry, 2010

Because ombrotrophic peat bogs receive inputs of water, nutrients, pollutants, and xerobiotic mat... more Because ombrotrophic peat bogs receive inputs of water, nutrients, pollutants, and xerobiotic materials solely from the atmosphere, and accumulate organic matter vertically, dated peat cores can provide a historical record of deposition. We propose a novel method for accurately determining dates of peat, based on cosmogenic 10 Be. In a laboratory study, we document limited post-depositional mobility of atmospherically-deposited Be, a requisite for 10 Be dating. We provide an example of how the 210 Pb-dated upper portion of a peat core can be used to back-calculate a site-specific 10 Be deposition rate, which can then be used to estimate dates for peat throughout a core, and also discuss limitations to the application of cosmogenic 10 Be to the dating of peat deposits.

Research paper thumbnail of Three-dimensional, bioactive, biodegradable, polymer-bioactive glass composite scaffolds with improved mechanical properties support collagen synthesis and mineralization of human osteoblast-like cellsin vitro

Journal of Biomedical Materials Research, 2003

In the past decade, tissue engineering-based bone grafting has emerged as a viable alternative to... more In the past decade, tissue engineering-based bone grafting has emerged as a viable alternative to biological and synthetic grafts. The biomaterial component is a critical determinant of the ultimate success of the tissueengineered graft. Because no single existing material possesses all the necessary properties required in an ideal bone graft, our approach has been to develop a three dimensional (3-D), porous composite of polylactide-co-glycolide (PLAGA) and 45S5 bioactive glass (BG) that is biodegradable, bioactive, and suitable as a scaffold for bone tissue engineering (PLAGA-BG composite). The objectives of this study were to examine the mechanical properties of a PLAGA-BG matrix, to evaluate the response of human osteoblast-like cells to the PLAGA-BG composite, and to evaluate the ability of the composite to form a surface calcium phosphate layer in vitro. Structural and mechanical properties of PLAGA-BG were measured, and the formation of a surface calcium phosphate layer was evaluated by surface analysis methods. The growth and differentiation of human osteoblast-like cells on PLAGA-BG were also examined. A hypothesis was that the combination of PLAGA with BG would result in a biocompatible and bioactive compos-ite, capable of supporting osteoblast adhesion, growth and differentiation, with mechanical properties superior to PLAGA alone. The addition of bioactive glass granules to the PLAGA matrix resulted in a structure with higher compressive modulus than PLAGA alone. Moreover, the PLAGA-BA composite was found to be a bioactive material, as it formed surface calcium phosphate deposits in a simulated body fluid (SBF), and in the presence of cells and serum proteins. The composite supported osteoblast-like morphology, stained positively for alkaline phosphatase, and supported higher levels of Type I collagen synthesis than tissue culture polystyrene controls. We have successfully developed a degradable, porous, polymer bioactive glass composite possessing improved mechanical properties and osteointegrative potential compared to degradable polymers of poly(lactic acid-glycolic acid) alone. Future work will focus on the optimization of the composite scaffold for bone tissue-engineering applications and the evaluation of the 3-D composite in an in vivo model.