The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
E M A Perrier - One of the best experts on this subject based on the ideXlab platform.
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the pore solid fractal model of Soil Density scaling
European Journal of Soil Science, 2003Co-Authors: N R A Bird, E M A PerrierAbstract:Summary We have developed the fractal approach to modelling variations in Soil bulk Density and porosity with scale of measurement or sample size. A new expression is derived for each quantity based on the pore–solid fractal (PSF) model of Soil structure. This new general expression covers a range of fractal media and accommodates existing fractal models as special cases. Model outputs cover a range of scaling behaviour expressed in terms of monotonic functions, from increasing Density and decreasing porosity, through constant porosity and Density to decreasing Density and increasing porosity with increasing scale of measurement. We demonstrate the link between this new model for the scaling of porosity and bulk Density and the water retention model for the PSF. The model for scaling bulk Density is fitted to data on aggregate bulk Density and shown to yield good fits describing bulk Density decreasing with increasing aggregate size. Porosity scaling is also inferred from the fitting of water retention data. Inferred porosities from different fittings are shown to follow decreasing, scale-invariant and increasing values with decreasing size of structural unit, and these theoretical results emphasize the need for further experimental investigation on the basic issue of Density scaling in Soil science.
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The pore–solid fractal model of Soil Density scaling
European Journal of Soil Science, 2003Co-Authors: N R A Bird, E M A PerrierAbstract:Summary We have developed the fractal approach to modelling variations in Soil bulk Density and porosity with scale of measurement or sample size. A new expression is derived for each quantity based on the pore–solid fractal (PSF) model of Soil structure. This new general expression covers a range of fractal media and accommodates existing fractal models as special cases. Model outputs cover a range of scaling behaviour expressed in terms of monotonic functions, from increasing Density and decreasing porosity, through constant porosity and Density to decreasing Density and increasing porosity with increasing scale of measurement. We demonstrate the link between this new model for the scaling of porosity and bulk Density and the water retention model for the PSF. The model for scaling bulk Density is fitted to data on aggregate bulk Density and shown to yield good fits describing bulk Density decreasing with increasing aggregate size. Porosity scaling is also inferred from the fitting of water retention data. Inferred porosities from different fittings are shown to follow decreasing, scale-invariant and increasing values with decreasing size of structural unit, and these theoretical results emphasize the need for further experimental investigation on the basic issue of Density scaling in Soil science.
N R A Bird - One of the best experts on this subject based on the ideXlab platform.
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the pore solid fractal model of Soil Density scaling
European Journal of Soil Science, 2003Co-Authors: N R A Bird, E M A PerrierAbstract:Summary We have developed the fractal approach to modelling variations in Soil bulk Density and porosity with scale of measurement or sample size. A new expression is derived for each quantity based on the pore–solid fractal (PSF) model of Soil structure. This new general expression covers a range of fractal media and accommodates existing fractal models as special cases. Model outputs cover a range of scaling behaviour expressed in terms of monotonic functions, from increasing Density and decreasing porosity, through constant porosity and Density to decreasing Density and increasing porosity with increasing scale of measurement. We demonstrate the link between this new model for the scaling of porosity and bulk Density and the water retention model for the PSF. The model for scaling bulk Density is fitted to data on aggregate bulk Density and shown to yield good fits describing bulk Density decreasing with increasing aggregate size. Porosity scaling is also inferred from the fitting of water retention data. Inferred porosities from different fittings are shown to follow decreasing, scale-invariant and increasing values with decreasing size of structural unit, and these theoretical results emphasize the need for further experimental investigation on the basic issue of Density scaling in Soil science.
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The pore–solid fractal model of Soil Density scaling
European Journal of Soil Science, 2003Co-Authors: N R A Bird, E M A PerrierAbstract:Summary We have developed the fractal approach to modelling variations in Soil bulk Density and porosity with scale of measurement or sample size. A new expression is derived for each quantity based on the pore–solid fractal (PSF) model of Soil structure. This new general expression covers a range of fractal media and accommodates existing fractal models as special cases. Model outputs cover a range of scaling behaviour expressed in terms of monotonic functions, from increasing Density and decreasing porosity, through constant porosity and Density to decreasing Density and increasing porosity with increasing scale of measurement. We demonstrate the link between this new model for the scaling of porosity and bulk Density and the water retention model for the PSF. The model for scaling bulk Density is fitted to data on aggregate bulk Density and shown to yield good fits describing bulk Density decreasing with increasing aggregate size. Porosity scaling is also inferred from the fitting of water retention data. Inferred porosities from different fittings are shown to follow decreasing, scale-invariant and increasing values with decreasing size of structural unit, and these theoretical results emphasize the need for further experimental investigation on the basic issue of Density scaling in Soil science.
Bruno Baur - One of the best experts on this subject based on the ideXlab platform.
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short term and long term effects of human trampling on above ground vegetation Soil Density Soil organic matter and Soil microbial processes in suburban beech forests
Applied Soil Ecology, 2009Co-Authors: Marion Kissling, Tessa K Hegetschweiler, Hanspeter Rusterholz, Bruno BaurAbstract:Understanding the effects of disturbance by human trampling on ecosystem processes is essential for the management of recreational areas. Discussions on recreational impacts are based either on data from trampling experiments or on field survey data from sites subjected to long-term recreational use, but rarely on a combination of both. We examined whether results from a short-term trampling experiment reflect the impact of long-term trampling around frequently used fire places. We compared short- and long-term effects of human trampling on above-ground forest vegetation and Soil physical, chemical and microbial characteristics. We found both similarities and differences in short- and long-term trampling effects. Both short- and long-term trampling reduced plant cover, plant height and species Density, though long-term effects were more pronounced than short-term effects. In both approaches, leaf litter biomass decreased, whereas Soil Density increased with trampling intensity. Other Soil characteristics including Soil moisture, total Soil organic matter content and total organic nitrogen content were not or only marginally affected by short- and long-term trampling. Furthermore, Soil microbial biomass and the activity of dehydrogenase did not change in both approaches. In contrast, the activity of β-glucosidase was only reduced by short-term trampling, whereas activity of phosphomonoesterase was reduced only by long-term trampling. Soil compaction was one factor reducing microbial activities at low and medium trampling intensities in our experiment and in the highly compacted area around the fire rings. We conclude that it could be problematic to use the results of short-term trampling experiments to predict general long-term trampling effects. Our results imply also that the restoration of degraded sites might be hampered by the low nutrient turnover resulting from the reduced litter layer and changes in enzyme activities, mitigating a successful re-establishment and growth of plants.
Marion Kissling - One of the best experts on this subject based on the ideXlab platform.
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short term and long term effects of human trampling on above ground vegetation Soil Density Soil organic matter and Soil microbial processes in suburban beech forests
Applied Soil Ecology, 2009Co-Authors: Marion Kissling, Tessa K Hegetschweiler, Hanspeter Rusterholz, Bruno BaurAbstract:Understanding the effects of disturbance by human trampling on ecosystem processes is essential for the management of recreational areas. Discussions on recreational impacts are based either on data from trampling experiments or on field survey data from sites subjected to long-term recreational use, but rarely on a combination of both. We examined whether results from a short-term trampling experiment reflect the impact of long-term trampling around frequently used fire places. We compared short- and long-term effects of human trampling on above-ground forest vegetation and Soil physical, chemical and microbial characteristics. We found both similarities and differences in short- and long-term trampling effects. Both short- and long-term trampling reduced plant cover, plant height and species Density, though long-term effects were more pronounced than short-term effects. In both approaches, leaf litter biomass decreased, whereas Soil Density increased with trampling intensity. Other Soil characteristics including Soil moisture, total Soil organic matter content and total organic nitrogen content were not or only marginally affected by short- and long-term trampling. Furthermore, Soil microbial biomass and the activity of dehydrogenase did not change in both approaches. In contrast, the activity of β-glucosidase was only reduced by short-term trampling, whereas activity of phosphomonoesterase was reduced only by long-term trampling. Soil compaction was one factor reducing microbial activities at low and medium trampling intensities in our experiment and in the highly compacted area around the fire rings. We conclude that it could be problematic to use the results of short-term trampling experiments to predict general long-term trampling effects. Our results imply also that the restoration of degraded sites might be hampered by the low nutrient turnover resulting from the reduced litter layer and changes in enzyme activities, mitigating a successful re-establishment and growth of plants.
Dirk Jaeger - One of the best experts on this subject based on the ideXlab platform.
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Soil compaction caused by cut to length forest operations and possible short term natural rehabilitation of Soil Density
Soil Science Society of America Journal, 2011Co-Authors: Eric R Labelle, Dirk JaegerAbstract:Our research explored the impact of forest machinery on Soil when traffi cking off -road through forest stands. In particular, we assessed Soil compaction caused by harvesting operations. Th is study had two objectives: (i) Quantify the increase of Soil bulk Density (absolute and relative Density) by forest machinery; and (ii) Analyze the persistence of Soil compaction over a 5-yr period. Our research was innovative in three respects; 1. We assessed in-place Soil Density at exactly the same locations pre- and posttreatment with a nuclear moisture and Density gauge. In this context, we consider treatment as forest machinery (harvester and forwarder) traffi cking on forest Soil. 2. Aft er the treatment, we monitored Soil Density at identical locations through yearly assessments for 5 yr to identify possible natural rehabilitation patterns. 3. We related the measured fi eld bulk densities to site specifi c maximum bulk densities derived by standard Proctor tests (concept of relative bulk Density) to get a better understanding of the severity of off -road traffi c impact on Soil Density changes. Our key fi ndings on two research sites were: 1. On average, dry Soil bulk Density increased by 19% in machine tracks. 2. Machine impact was not just limited to vehicle tracks; we noticed an increase of Soil bulk Density >10% in 14 of 65 (21.5%) locations extending up to 1 m away from tracks. 3. Due to machine impact, fi eld bulk Density increases exceeded the 80% maximum bulk Density threshold at 32% of all track locations, mostly in Soil depths of 20 to 30 cm. 4. Monitoring Soil Density for 5 yr aft er the treatment indicated no natural rehabilitation (decrease) of Soil Density down to pretreatment levels. Abbreviations: ASL, above sea level; CTL, cut-to-length; DBH, diameter at breast height; FBD, fi eld bulk Density; MBD, maximum bulk Density; ML, sandy silt; NGP, nominal ground pressure; NMDG, nuclear moisture-Density gauge; OWC, optimum water content; RBD, relative bulk Density; SL, silty sand with gravel; USCS, Unifi ed Soil Classifi cation System.
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Soil Compaction Caused by Cut‐to‐Length Forest Operations and Possible Short‐Term Natural Rehabilitation of Soil Density
Soil Science Society of America Journal, 2011Co-Authors: Eric R Labelle, Dirk JaegerAbstract:Our research explored the impact of forest machinery on Soil when traffi cking off -road through forest stands. In particular, we assessed Soil compaction caused by harvesting operations. Th is study had two objectives: (i) Quantify the increase of Soil bulk Density (absolute and relative Density) by forest machinery; and (ii) Analyze the persistence of Soil compaction over a 5-yr period. Our research was innovative in three respects; 1. We assessed in-place Soil Density at exactly the same locations pre- and posttreatment with a nuclear moisture and Density gauge. In this context, we consider treatment as forest machinery (harvester and forwarder) traffi cking on forest Soil. 2. Aft er the treatment, we monitored Soil Density at identical locations through yearly assessments for 5 yr to identify possible natural rehabilitation patterns. 3. We related the measured fi eld bulk densities to site specifi c maximum bulk densities derived by standard Proctor tests (concept of relative bulk Density) to get a better understanding of the severity of off -road traffi c impact on Soil Density changes. Our key fi ndings on two research sites were: 1. On average, dry Soil bulk Density increased by 19% in machine tracks. 2. Machine impact was not just limited to vehicle tracks; we noticed an increase of Soil bulk Density >10% in 14 of 65 (21.5%) locations extending up to 1 m away from tracks. 3. Due to machine impact, fi eld bulk Density increases exceeded the 80% maximum bulk Density threshold at 32% of all track locations, mostly in Soil depths of 20 to 30 cm. 4. Monitoring Soil Density for 5 yr aft er the treatment indicated no natural rehabilitation (decrease) of Soil Density down to pretreatment levels. Abbreviations: ASL, above sea level; CTL, cut-to-length; DBH, diameter at breast height; FBD, fi eld bulk Density; MBD, maximum bulk Density; ML, sandy silt; NGP, nominal ground pressure; NMDG, nuclear moisture-Density gauge; OWC, optimum water content; RBD, relative bulk Density; SL, silty sand with gravel; USCS, Unifi ed Soil Classifi cation System.
