Plants employ a range of strategies to increase phosphorus (P) availability in soil. Current soil... more Plants employ a range of strategies to increase phosphorus (P) availability in soil. Current soil P extraction methods (e.g. Olsen P), however, often fail to capture the potential importance of rhizosphere processes in supplying P to the plant. This has led to criticism of these standard approaches, especially in nonagricultural soils of low P status and when comparing soil types across diverse landscapes. Similarly, more complex soil P extraction protocols (e.g. Hedley sequential fractionation) lack functional significance from a plant ecology perspective. In response to this, we present a novel procedure using a suite of established extraction protocols to explore the concept of a protocol that characterizes P pools available via plant and microbial P acquisition mechanisms. The biologically based P (BBP) extraction was conducted by using four extractions in parallel: (1) 10 mM CaCl2 (soluble P); (2) 10 mM citric acid (chelate extractable P); (3) phytase and phosphatase solution (enzyme extractable organic P); (4) 1 M HCl (mineral occluded P). To test the protocol, we conducted the analyses on a total of 204 soil samples collected as part of a UK national ecosystem survey (Countryside Survey) in 1998 and repeated again in 2007. In the survey, Olsen P showed a net decline in national soil P levels during this 10 year period. In agreement with these results, soluble P, citrate extractable P and mineral occluded P were all found to decrease over the 10 year study period. In contrast, enzyme extractable organic P increased over the same period likely due to the accumulation of organic P in the mineral soil. The method illustrates a noted shift in P pools over the 10 year period, but no net loss of P from the system. This new method is simple and inexpensive and therefore has the potential to greatly improve our ability to characterise and understand changes in soil P status across complex landscapes.
Wildland road removal is a common practice across the U.S. and in some parts of Canada. The main ... more Wildland road removal is a common practice across the U.S. and in some parts of Canada. The main types of road removal include ripping, stream crossing restoration, and full recontour. Road removal creates a short-term disturbance that may temporarily increase sediment loss. However, research and long-term monitoring have shown that road removal both reduces erosion rates and the risk of
Biological feedback mechanisms regulate fundamental ecosystem processes and potentially regulate ... more Biological feedback mechanisms regulate fundamental ecosystem processes and potentially regulate ecosystem productivity. To date, no studies have documented the down-regulation of terrestrial nitrogen (N) fixation via an ecosystem-level feedback mechanism. Herein, we demonstrate such a feedback in boreal forests. Rapid cycling of N in early secondary succession forests yielded greater throughfall N deposition, which in turn decreased N fixation by cyanobacterial associates in feather moss carpets that reside on the forest floor. The forest canopy exerts a tight control on biotic N input at a period of high productivity.
Cyanobacteria colonizing the feather moss Pleurozium schreberi were isolated from moss samples co... more Cyanobacteria colonizing the feather moss Pleurozium schreberi were isolated from moss samples collected in northern Sweden and subjected to physiological and molecular characterization. Morphological studies of isolated and moss-associated cyanobacteria were carried out by light microscopy. Molecular tools were used for cyanobacteria identification, and a reconstitution experiment of the association between non-associative mosses and cyanobacteria was conducted. The influence of temperature on N2 fixation in the different cyanobacterial isolates and the influence of light and temperature on N2-fixation rates in the moss were studied using the acetylene reduction assay. Two different cyanobacteria were effectively isolated from P. schreberi: Nostoc sp. and Calothrix sp. A third genus, Stigonema sp. was identified by microscopy, but could not be isolated. The Nostoc sp. was found to fix N2 at lower temperatures than Calothrix sp. Nostoc sp. and Stigonema sp. were the predominant cyanobacteria colonizing the moss. The attempt to reconstitute the association between the moss and cyanobacteria was successful. The two isolated genera of cyanobacteria in feather moss samples collected in northern Sweden differ in their temperature optima, which may have important ecological implications.
Between January 1987 and December 1989, 20 female patients with one mechanical valve prosthesis (... more Between January 1987 and December 1989, 20 female patients with one mechanical valve prosthesis (MVP) for at least 1 year postoperatively were studied while on coumarin therapy for the full length of pregnancy. In each case, caesarean section was scheduled for the 38th week. Patients were selected according to the following criteria: (1) prothrombin ratios remaining within the therapeutic range for more than 85% of their total estimations in the previous 12 months with mean daily doses of warfarin less than 5 mg; (2) stable cardiac status; (3) no previous obstetric diseases and (4) full acceptance of the risks involved in the protocol. The patients were in NYHA functional class I or II. Their ages ranged from 23 to 31 years (mean 26 +/- 3). Ten patients had a mitral prosthesis and 10 an aortic prosthesis. Among the 20 mechanical valve prostheses, 10 were Sorin, 6 Starr-Edwards, 2 Bjørk-Shiley, and 2 Lillehei-Kaster. Eighteen patients were in sinus rythm, 1 in chronic atrial fibrillation, and 1 had a permanent endocardial pacemaker. Nineteen were delivered by caesarean section: warfarin was withdrawn 48 h before surgery and resumed 24 h thereafter. One patient had premature spontaneous delivery at 36 weeks. The mean prothrombin ratio measured weekly in the 20 patients was 2.06 +/- 0.45 INR, using a mean daily warfarin dose of 4.1 mg +/- 1.63. The mean value of the prothrombin ratio during caesarean section for the 19 patients was 1.23 +/- 0.38 INR. In the 20 live births, the mean birth weight was 2.9 kg +/- 0.40.(ABSTRACT TRUNCATED AT 250 WORDS)
Plants employ a range of strategies to increase phosphorus (P) availability in soil. Current soil... more Plants employ a range of strategies to increase phosphorus (P) availability in soil. Current soil P extraction methods (e.g. Olsen P), however, often fail to capture the potential importance of rhizosphere processes in supplying P to the plant. This has led to criticism of these standard approaches, especially in nonagricultural soils of low P status and when comparing soil types across diverse landscapes. Similarly, more complex soil P extraction protocols (e.g. Hedley sequential fractionation) lack functional significance from a plant ecology perspective. In response to this, we present a novel procedure using a suite of established extraction protocols to explore the concept of a protocol that characterizes P pools available via plant and microbial P acquisition mechanisms. The biologically based P (BBP) extraction was conducted by using four extractions in parallel: (1) 10 mM CaCl2 (soluble P); (2) 10 mM citric acid (chelate extractable P); (3) phytase and phosphatase solution (enzyme extractable organic P); (4) 1 M HCl (mineral occluded P). To test the protocol, we conducted the analyses on a total of 204 soil samples collected as part of a UK national ecosystem survey (Countryside Survey) in 1998 and repeated again in 2007. In the survey, Olsen P showed a net decline in national soil P levels during this 10 year period. In agreement with these results, soluble P, citrate extractable P and mineral occluded P were all found to decrease over the 10 year study period. In contrast, enzyme extractable organic P increased over the same period likely due to the accumulation of organic P in the mineral soil. The method illustrates a noted shift in P pools over the 10 year period, but no net loss of P from the system. This new method is simple and inexpensive and therefore has the potential to greatly improve our ability to characterise and understand changes in soil P status across complex landscapes.
Wildland road removal is a common practice across the U.S. and in some parts of Canada. The main ... more Wildland road removal is a common practice across the U.S. and in some parts of Canada. The main types of road removal include ripping, stream crossing restoration, and full recontour. Road removal creates a short-term disturbance that may temporarily increase sediment loss. However, research and long-term monitoring have shown that road removal both reduces erosion rates and the risk of
Biological feedback mechanisms regulate fundamental ecosystem processes and potentially regulate ... more Biological feedback mechanisms regulate fundamental ecosystem processes and potentially regulate ecosystem productivity. To date, no studies have documented the down-regulation of terrestrial nitrogen (N) fixation via an ecosystem-level feedback mechanism. Herein, we demonstrate such a feedback in boreal forests. Rapid cycling of N in early secondary succession forests yielded greater throughfall N deposition, which in turn decreased N fixation by cyanobacterial associates in feather moss carpets that reside on the forest floor. The forest canopy exerts a tight control on biotic N input at a period of high productivity.
Cyanobacteria colonizing the feather moss Pleurozium schreberi were isolated from moss samples co... more Cyanobacteria colonizing the feather moss Pleurozium schreberi were isolated from moss samples collected in northern Sweden and subjected to physiological and molecular characterization. Morphological studies of isolated and moss-associated cyanobacteria were carried out by light microscopy. Molecular tools were used for cyanobacteria identification, and a reconstitution experiment of the association between non-associative mosses and cyanobacteria was conducted. The influence of temperature on N2 fixation in the different cyanobacterial isolates and the influence of light and temperature on N2-fixation rates in the moss were studied using the acetylene reduction assay. Two different cyanobacteria were effectively isolated from P. schreberi: Nostoc sp. and Calothrix sp. A third genus, Stigonema sp. was identified by microscopy, but could not be isolated. The Nostoc sp. was found to fix N2 at lower temperatures than Calothrix sp. Nostoc sp. and Stigonema sp. were the predominant cyanobacteria colonizing the moss. The attempt to reconstitute the association between the moss and cyanobacteria was successful. The two isolated genera of cyanobacteria in feather moss samples collected in northern Sweden differ in their temperature optima, which may have important ecological implications.
Between January 1987 and December 1989, 20 female patients with one mechanical valve prosthesis (... more Between January 1987 and December 1989, 20 female patients with one mechanical valve prosthesis (MVP) for at least 1 year postoperatively were studied while on coumarin therapy for the full length of pregnancy. In each case, caesarean section was scheduled for the 38th week. Patients were selected according to the following criteria: (1) prothrombin ratios remaining within the therapeutic range for more than 85% of their total estimations in the previous 12 months with mean daily doses of warfarin less than 5 mg; (2) stable cardiac status; (3) no previous obstetric diseases and (4) full acceptance of the risks involved in the protocol. The patients were in NYHA functional class I or II. Their ages ranged from 23 to 31 years (mean 26 +/- 3). Ten patients had a mitral prosthesis and 10 an aortic prosthesis. Among the 20 mechanical valve prostheses, 10 were Sorin, 6 Starr-Edwards, 2 Bjørk-Shiley, and 2 Lillehei-Kaster. Eighteen patients were in sinus rythm, 1 in chronic atrial fibrillation, and 1 had a permanent endocardial pacemaker. Nineteen were delivered by caesarean section: warfarin was withdrawn 48 h before surgery and resumed 24 h thereafter. One patient had premature spontaneous delivery at 36 weeks. The mean prothrombin ratio measured weekly in the 20 patients was 2.06 +/- 0.45 INR, using a mean daily warfarin dose of 4.1 mg +/- 1.63. The mean value of the prothrombin ratio during caesarean section for the 19 patients was 1.23 +/- 0.38 INR. In the 20 live births, the mean birth weight was 2.9 kg +/- 0.40.(ABSTRACT TRUNCATED AT 250 WORDS)
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methods (e.g. Olsen P), however, often fail to capture the potential importance of rhizosphere processes
in supplying P to the plant. This has led to criticism of these standard approaches, especially in nonagricultural
soils of low P status and when comparing soil types across diverse landscapes. Similarly,
more complex soil P extraction protocols (e.g. Hedley sequential fractionation) lack functional significance
from a plant ecology perspective. In response to this, we present a novel procedure using a suite of
established extraction protocols to explore the concept of a protocol that characterizes P pools available
via plant and microbial P acquisition mechanisms. The biologically based P (BBP) extraction was conducted
by using four extractions in parallel: (1) 10 mM CaCl2 (soluble P); (2) 10 mM citric acid (chelate
extractable P); (3) phytase and phosphatase solution (enzyme extractable organic P); (4) 1 M HCl
(mineral occluded P). To test the protocol, we conducted the analyses on a total of 204 soil samples
collected as part of a UK national ecosystem survey (Countryside Survey) in 1998 and repeated again in
2007. In the survey, Olsen P showed a net decline in national soil P levels during this 10 year period. In
agreement with these results, soluble P, citrate extractable P and mineral occluded P were all found to
decrease over the 10 year study period. In contrast, enzyme extractable organic P increased over the
same period likely due to the accumulation of organic P in the mineral soil. The method illustrates a
noted shift in P pools over the 10 year period, but no net loss of P from the system. This new method is
simple and inexpensive and therefore has the potential to greatly improve our ability to characterise and
understand changes in soil P status across complex landscapes.
methods (e.g. Olsen P), however, often fail to capture the potential importance of rhizosphere processes
in supplying P to the plant. This has led to criticism of these standard approaches, especially in nonagricultural
soils of low P status and when comparing soil types across diverse landscapes. Similarly,
more complex soil P extraction protocols (e.g. Hedley sequential fractionation) lack functional significance
from a plant ecology perspective. In response to this, we present a novel procedure using a suite of
established extraction protocols to explore the concept of a protocol that characterizes P pools available
via plant and microbial P acquisition mechanisms. The biologically based P (BBP) extraction was conducted
by using four extractions in parallel: (1) 10 mM CaCl2 (soluble P); (2) 10 mM citric acid (chelate
extractable P); (3) phytase and phosphatase solution (enzyme extractable organic P); (4) 1 M HCl
(mineral occluded P). To test the protocol, we conducted the analyses on a total of 204 soil samples
collected as part of a UK national ecosystem survey (Countryside Survey) in 1998 and repeated again in
2007. In the survey, Olsen P showed a net decline in national soil P levels during this 10 year period. In
agreement with these results, soluble P, citrate extractable P and mineral occluded P were all found to
decrease over the 10 year study period. In contrast, enzyme extractable organic P increased over the
same period likely due to the accumulation of organic P in the mineral soil. The method illustrates a
noted shift in P pools over the 10 year period, but no net loss of P from the system. This new method is
simple and inexpensive and therefore has the potential to greatly improve our ability to characterise and
understand changes in soil P status across complex landscapes.