Background/Question/Methods Redistribution of runoff is a fundamental ecohydrological processes i... more Background/Question/Methods Redistribution of runoff is a fundamental ecohydrological processes in semiarid woodlands. Runoff is often generated from intercanopy patches that separate the canopy patches of woody plants, particularly from locations with bare soil, and subsequently captured by vegetation patches, where the concentration of resources can be ecologically significant. Although redistribution by erosion also occurs, less well documented is the extent to which biogeochemical patterns such as total C and total N are affected, particularly in rapidly eroding hillslopes where redistribution might be greatest. We measured total soil C and total soil N at two hillslope positions (upslope and downslope) for interill areas including two patch types (canopies of woody plants and intercanopies separating them) and for rill areas in a rapidly eroding semiarid piñon-juniper woodland in northern New Mexico, USA. Results/Conclusions Downslope interill locations of either patch type had...
Zou CB (2013) The critical amplifying role of increasing atmospheric moisture demand on tree mort... more Zou CB (2013) The critical amplifying role of increasing atmospheric moisture demand on tree mortality and associated regional die-off. Front. Plant Sci. 4:266.
Processes within the critical zone-spanning groundwater to the top of the vegetation canopy-have ... more Processes within the critical zone-spanning groundwater to the top of the vegetation canopy-have important societal relevance and operate over broad spatial and temporal scales that often are not included in existing frameworks for ecosystem services evaluation. Here we expand the scope of ecosystem services by specifying how critical zone processes extend context both spatially and temporally, determine constraints that limit provision of services, and offer a potentially powerful currency for evaluation. Context: A critical zone perspective extends the context of ecosystem services by expressly addressing how the physical structure of the terrestrial Earth surface (e.g., parent material, topography, and orography) provides a broader spatial and temporal template determining the coevolution of physical and biological systems that result in societal benefits. Constraints: The rates at which many ecosystem services are provided are fundamentally constrained by rate-limited critical zone processes, a phenomenon that we describe as a conceptual "supply chain" that accounts for rate-limiting soil formation, hydrologic partitioning, and streamflow generation. Currency: One of the major challenges in assessing ecosystem services is the evaluation of their importance by linking ecological processes to societal benefits through market and nonmarket valuation. We propose that critical zone processes be integrated into an evaluation currency, useful for valuation, by quantifying the energy flux available to do thermodynamic work on the critical zone. In short, characterization of critical zone processes expands the scope of ecosystem services by providing context, constraints, and currency that enable more effective management needed to respond to impacts of changing climate and disturbances.
Soil surface conditions can have profound effects on plant seedling emergence and subsequent seed... more Soil surface conditions can have profound effects on plant seedling emergence and subsequent seedling survival. To test the hypothesis that different soil-surface treatments with logging residue affect range grass seedling emergence and survival, 6 alternative forest-residual treatments were established in the summer of 1998 following thinning of mature trees from approximately 500 to 133 trees ? ha 21 . The treatments included 1) whole logging debris, hand-piled; 2) whole logging-debris piles that were burned; 3) whole logging-debris piles that were chipped; 4) whole logging-debris piles that were chipped and burned; 5) scattered debris followed by a broadcast burn; and 6) zero debris, not burned. The influences of the debris treatments on grass seedling emergence and survival were tested by seeding with native and exotic perennial grass species. Three plots per treatment were seeded with a mix of 4 native grass species, and another 3 plots per treatment were seeded with a mix of 4 exotic grass species. Two plots per treatment were left unseeded. Subsequent grass emergence, growth, and establishment were measured as seedling emergence, cover, density, height, and biomass for 3 growing seasons. Grass cover, density height, and biomass increased on the burn treatments during the study. Less-significant results were obtained for the nonburned woodydebris treatments. In addition, important abiotic factors, such as soil moisture and soil surface temperature, were not adversely affected by the woody debris disposal practices tested in this study. Results indicate that scattered woody debris that is broadcast burned is the best mechanism for disposing of woody debris, increasing grass emergence and survival, and preventing ponderosa pine recruitment and exotic invasion.
Carbon and nitrogen are crucial to semiarid woodlands, determining decomposition, production and ... more Carbon and nitrogen are crucial to semiarid woodlands, determining decomposition, production and redistribution of water and nutrients. Carbon and nitrogen are often greater beneath canopies than intercanopies. Upslope vs. downslope position and ephemeral channels might also cause variation in C and N. Yet, few studies have simultaneously evaluated spatial variation associated with canopyeintercanopy patches and topography. We estimated C and N upslope and downslope in an eroding piñonejuniper woodland for canopies beneath piñons (Pinus edulis) and junipers, (Juniperus monosperma), intercanopies, and ephemeral channels. Soil C and N in the surface and profile beneath canopies exceeded that of intercanopies and channels. Relative to intercanopies, channels had more profile C upslope but less downslope (profile N was not significant). Relative to upslope, profile C downslope for intercanopies was greater and for channels was less (profile N was not significant). Relative to profile, surface soil C and N exhibited less heterogeneity. Although some topographic heterogeneity was detected, results did not collectively support our redistribution hypotheses, and we are unable to distinguish if this heterogeneity is due to in situ or redistribution effects. Nonetheless, results highlight finer topographical spatial variation in addition to predominant canopy and intercanopy variation that is applicable for semiarid woodland management.
Soil evaporation, a critical ecohydrological process in drylands, can exhibit substantial spatio-... more Soil evaporation, a critical ecohydrological process in drylands, can exhibit substantial spatio-temporal variation. Spatially, ecohydrological controls of soil evaporation may generally depend on a hierarchical structure spanning from the presence or absence of litter, through canopy patches of woody plants and intercanopy patches separating them, up to the overall vegetation mosaic characterized by density of woody plant cover in the landscape, although assessment of these factors in concert is generally lacking. Temporally, ecohydrological controls can be further complicated by not only seasonal climate, but also phenology, particularly in seasonally deciduous drylands. We experimentally assessed the interactive controls on soil evaporation along a gradient of mesquite cover (Prosopis velutina) within the North American monsoon region, with respect to such hierarchical structure and seasonality/phenology. Our results indicate that presence of litter exerts a dominant control on soil evaporation, independent of seasonality; in absence of litter, both patch and mosaic attributes influence soil evaporation variably with season/phenology. Correlations from related measures of incoming energy suggest energy limits evaporation in many cases, although other factors such as wind may potentially influence hierarchical and seasonal/phenological combinations. Our results highlight the need to account for both hierarchical vegetation structure and seasonal/phenological variability to improve ecohydrological predictions of soil evaporation.
Plant water use in drylands can be complex due to variation in hydrologic, abiotic and biotic fac... more Plant water use in drylands can be complex due to variation in hydrologic, abiotic and biotic factors, particularly near ephemeral or intermittent streams. Plant use of groundwater may be important but is usually uncertain. Disturbances like fire contribute to complex spatiotemporal heterogeneity. Improved understanding of how such hydrologic, abiotic, and biotic factors affect plant water use is needed not only to address management issues related to land use but also due to climate change, particularly for drylands projected to become warmer and drier such as much of the southwestern USA Here we focus on the interactive roles of hydrologic, abiotic, and biotic factors in determining plant water use of Gambel oak in ephemeral and/or intermittent riparian areas of ponderosa pine forest in central New Mexico, USA along a fire disturbance gradient with varying oak densities. More specifically, the purpose of this research is to determine: (1) depth to and frequency of groundwater associated with intermittent and ephemeral streams, (2) isotopic indications of whether or not groundwater is used by plants, and (3) plant water use (conductance, transpiration, and water use efficiency) interactions with groundwater. Depth to groundwater, which could be as shallow as 1 m or less, increased with plant density but plant water use efficiency decreased. Photosynthesis:transpiration ratios maximizing water use efficiency for a given successional stage appeared to be also affected by windspeed and leaf size, highlighting interactive effects of hydrologic, abiotic and biotic affects-a finding that may be ecohydrologically relevant for other dryland riparian systems. Published in 2010. This article is a US Government work and is in the public domain in the USA
Darin J. Lawl, Clayton B. Marlow'?, Jeftrey C. Mosley, Steve Custe13, Paul Hooka, and Bob Le... more Darin J. Lawl, Clayton B. Marlow'?, Jeftrey C. Mosley, Steve Custe13, Paul Hooka, and Bob Leinard5, Department of An mal and Range Sc ences ... Two sites were on sandy to cobbly alluvium on glacial outwash along the Blackfoot Rjver in a narrow mountain valley near Ovando ...
Monitoring of aeolian transport is needed for assessment and management of human health risks as ... more Monitoring of aeolian transport is needed for assessment and management of human health risks as well as for soil resources. Human health risks are assessed based on duration of exposure as well as concentration. Many aeolian studies focus on periods of high wind speed when concentrations are greatest but few studies focus on ''background'' conditions when concentrations are likely lower but which represent the most prevalent conditions. Such ''background'' conditions might be especially important at sites with recent disturbance such as fire. Exposure assessments also require improved understanding relating longer-term (days to weeks) measurements of saltation of larger particles to shorter-term (minutes to hours) measurements of smaller inhalable dust particles. To address these issues, we employed three commonly used instruments for measuring dust emissions for unburned and recently-burned sites: Big Springs Number Eight (BSNE) samplers for larger saltating soil particles (>50 lm) with weekly to monthly sampling resolution, DustTraks for suspended particles (diameters <10 lm) with 1-s sampling resolution, and Total Suspended Particulate (TSP) filter samplers for measuring with hourly to daily sampling resolution. Significant differences in concentrations between burned and unburned sites were detectable in either short (1-s maximum) interval DustTrak PM10 measurements, or in longer term (weekly) BSNE horizontal sediment flux measurements, but not in intermediate-term (daily 5-h means) for either DustTrak PM10 or TSP measurements. The results highlight ongoing dust emissions during less windy periods and provide insight into the complex interplay among particle-size dependent measures and typical time scales measured.
1] The diverse and fundamental effects that aeolian processes have on the biosphere and geosphere... more 1] The diverse and fundamental effects that aeolian processes have on the biosphere and geosphere are commonly generated by horizontal sediment transport at the land surface. However, predicting horizontal sediment transport depends on vegetation architecture, which is difficult to quantify in a rapid but accurate manner. We demonstrate an approach to measure vegetation canopy architecture at high resolution using lidar along a gradient of dryland sites ranging from 2% to 73% woody plant canopy cover. Lidar-derived canopy height, distance (gaps) between vegetation elements (e.g., trunks, limbs, leaves), and the distribution of gaps scaled by vegetation height were correlated with canopy cover and highlight potentially improved horizontal dust flux estimation than with cover alone. Employing lidar to estimate detailed vegetation canopy architecture offers promise for improved predictions of horizontal sediment transport across heterogeneous plant assemblages. Citation: Sankey, J. B., D. J. Law, D. D. Breshears, S. M. Munson, and R. H. Webb (2013), Employing lidar to detail vegetation canopy architecture for prediction of aeolian transport,
Background/Question/Methods Redistribution of runoff is a fundamental ecohydrological processes i... more Background/Question/Methods Redistribution of runoff is a fundamental ecohydrological processes in semiarid woodlands. Runoff is often generated from intercanopy patches that separate the canopy patches of woody plants, particularly from locations with bare soil, and subsequently captured by vegetation patches, where the concentration of resources can be ecologically significant. Although redistribution by erosion also occurs, less well documented is the extent to which biogeochemical patterns such as total C and total N are affected, particularly in rapidly eroding hillslopes where redistribution might be greatest. We measured total soil C and total soil N at two hillslope positions (upslope and downslope) for interill areas including two patch types (canopies of woody plants and intercanopies separating them) and for rill areas in a rapidly eroding semiarid piñon-juniper woodland in northern New Mexico, USA. Results/Conclusions Downslope interill locations of either patch type had...
Zou CB (2013) The critical amplifying role of increasing atmospheric moisture demand on tree mort... more Zou CB (2013) The critical amplifying role of increasing atmospheric moisture demand on tree mortality and associated regional die-off. Front. Plant Sci. 4:266.
Processes within the critical zone-spanning groundwater to the top of the vegetation canopy-have ... more Processes within the critical zone-spanning groundwater to the top of the vegetation canopy-have important societal relevance and operate over broad spatial and temporal scales that often are not included in existing frameworks for ecosystem services evaluation. Here we expand the scope of ecosystem services by specifying how critical zone processes extend context both spatially and temporally, determine constraints that limit provision of services, and offer a potentially powerful currency for evaluation. Context: A critical zone perspective extends the context of ecosystem services by expressly addressing how the physical structure of the terrestrial Earth surface (e.g., parent material, topography, and orography) provides a broader spatial and temporal template determining the coevolution of physical and biological systems that result in societal benefits. Constraints: The rates at which many ecosystem services are provided are fundamentally constrained by rate-limited critical zone processes, a phenomenon that we describe as a conceptual "supply chain" that accounts for rate-limiting soil formation, hydrologic partitioning, and streamflow generation. Currency: One of the major challenges in assessing ecosystem services is the evaluation of their importance by linking ecological processes to societal benefits through market and nonmarket valuation. We propose that critical zone processes be integrated into an evaluation currency, useful for valuation, by quantifying the energy flux available to do thermodynamic work on the critical zone. In short, characterization of critical zone processes expands the scope of ecosystem services by providing context, constraints, and currency that enable more effective management needed to respond to impacts of changing climate and disturbances.
Soil surface conditions can have profound effects on plant seedling emergence and subsequent seed... more Soil surface conditions can have profound effects on plant seedling emergence and subsequent seedling survival. To test the hypothesis that different soil-surface treatments with logging residue affect range grass seedling emergence and survival, 6 alternative forest-residual treatments were established in the summer of 1998 following thinning of mature trees from approximately 500 to 133 trees ? ha 21 . The treatments included 1) whole logging debris, hand-piled; 2) whole logging-debris piles that were burned; 3) whole logging-debris piles that were chipped; 4) whole logging-debris piles that were chipped and burned; 5) scattered debris followed by a broadcast burn; and 6) zero debris, not burned. The influences of the debris treatments on grass seedling emergence and survival were tested by seeding with native and exotic perennial grass species. Three plots per treatment were seeded with a mix of 4 native grass species, and another 3 plots per treatment were seeded with a mix of 4 exotic grass species. Two plots per treatment were left unseeded. Subsequent grass emergence, growth, and establishment were measured as seedling emergence, cover, density, height, and biomass for 3 growing seasons. Grass cover, density height, and biomass increased on the burn treatments during the study. Less-significant results were obtained for the nonburned woodydebris treatments. In addition, important abiotic factors, such as soil moisture and soil surface temperature, were not adversely affected by the woody debris disposal practices tested in this study. Results indicate that scattered woody debris that is broadcast burned is the best mechanism for disposing of woody debris, increasing grass emergence and survival, and preventing ponderosa pine recruitment and exotic invasion.
Carbon and nitrogen are crucial to semiarid woodlands, determining decomposition, production and ... more Carbon and nitrogen are crucial to semiarid woodlands, determining decomposition, production and redistribution of water and nutrients. Carbon and nitrogen are often greater beneath canopies than intercanopies. Upslope vs. downslope position and ephemeral channels might also cause variation in C and N. Yet, few studies have simultaneously evaluated spatial variation associated with canopyeintercanopy patches and topography. We estimated C and N upslope and downslope in an eroding piñonejuniper woodland for canopies beneath piñons (Pinus edulis) and junipers, (Juniperus monosperma), intercanopies, and ephemeral channels. Soil C and N in the surface and profile beneath canopies exceeded that of intercanopies and channels. Relative to intercanopies, channels had more profile C upslope but less downslope (profile N was not significant). Relative to upslope, profile C downslope for intercanopies was greater and for channels was less (profile N was not significant). Relative to profile, surface soil C and N exhibited less heterogeneity. Although some topographic heterogeneity was detected, results did not collectively support our redistribution hypotheses, and we are unable to distinguish if this heterogeneity is due to in situ or redistribution effects. Nonetheless, results highlight finer topographical spatial variation in addition to predominant canopy and intercanopy variation that is applicable for semiarid woodland management.
Soil evaporation, a critical ecohydrological process in drylands, can exhibit substantial spatio-... more Soil evaporation, a critical ecohydrological process in drylands, can exhibit substantial spatio-temporal variation. Spatially, ecohydrological controls of soil evaporation may generally depend on a hierarchical structure spanning from the presence or absence of litter, through canopy patches of woody plants and intercanopy patches separating them, up to the overall vegetation mosaic characterized by density of woody plant cover in the landscape, although assessment of these factors in concert is generally lacking. Temporally, ecohydrological controls can be further complicated by not only seasonal climate, but also phenology, particularly in seasonally deciduous drylands. We experimentally assessed the interactive controls on soil evaporation along a gradient of mesquite cover (Prosopis velutina) within the North American monsoon region, with respect to such hierarchical structure and seasonality/phenology. Our results indicate that presence of litter exerts a dominant control on soil evaporation, independent of seasonality; in absence of litter, both patch and mosaic attributes influence soil evaporation variably with season/phenology. Correlations from related measures of incoming energy suggest energy limits evaporation in many cases, although other factors such as wind may potentially influence hierarchical and seasonal/phenological combinations. Our results highlight the need to account for both hierarchical vegetation structure and seasonal/phenological variability to improve ecohydrological predictions of soil evaporation.
Plant water use in drylands can be complex due to variation in hydrologic, abiotic and biotic fac... more Plant water use in drylands can be complex due to variation in hydrologic, abiotic and biotic factors, particularly near ephemeral or intermittent streams. Plant use of groundwater may be important but is usually uncertain. Disturbances like fire contribute to complex spatiotemporal heterogeneity. Improved understanding of how such hydrologic, abiotic, and biotic factors affect plant water use is needed not only to address management issues related to land use but also due to climate change, particularly for drylands projected to become warmer and drier such as much of the southwestern USA Here we focus on the interactive roles of hydrologic, abiotic, and biotic factors in determining plant water use of Gambel oak in ephemeral and/or intermittent riparian areas of ponderosa pine forest in central New Mexico, USA along a fire disturbance gradient with varying oak densities. More specifically, the purpose of this research is to determine: (1) depth to and frequency of groundwater associated with intermittent and ephemeral streams, (2) isotopic indications of whether or not groundwater is used by plants, and (3) plant water use (conductance, transpiration, and water use efficiency) interactions with groundwater. Depth to groundwater, which could be as shallow as 1 m or less, increased with plant density but plant water use efficiency decreased. Photosynthesis:transpiration ratios maximizing water use efficiency for a given successional stage appeared to be also affected by windspeed and leaf size, highlighting interactive effects of hydrologic, abiotic and biotic affects-a finding that may be ecohydrologically relevant for other dryland riparian systems. Published in 2010. This article is a US Government work and is in the public domain in the USA
Darin J. Lawl, Clayton B. Marlow'?, Jeftrey C. Mosley, Steve Custe13, Paul Hooka, and Bob Le... more Darin J. Lawl, Clayton B. Marlow'?, Jeftrey C. Mosley, Steve Custe13, Paul Hooka, and Bob Leinard5, Department of An mal and Range Sc ences ... Two sites were on sandy to cobbly alluvium on glacial outwash along the Blackfoot Rjver in a narrow mountain valley near Ovando ...
Monitoring of aeolian transport is needed for assessment and management of human health risks as ... more Monitoring of aeolian transport is needed for assessment and management of human health risks as well as for soil resources. Human health risks are assessed based on duration of exposure as well as concentration. Many aeolian studies focus on periods of high wind speed when concentrations are greatest but few studies focus on ''background'' conditions when concentrations are likely lower but which represent the most prevalent conditions. Such ''background'' conditions might be especially important at sites with recent disturbance such as fire. Exposure assessments also require improved understanding relating longer-term (days to weeks) measurements of saltation of larger particles to shorter-term (minutes to hours) measurements of smaller inhalable dust particles. To address these issues, we employed three commonly used instruments for measuring dust emissions for unburned and recently-burned sites: Big Springs Number Eight (BSNE) samplers for larger saltating soil particles (>50 lm) with weekly to monthly sampling resolution, DustTraks for suspended particles (diameters <10 lm) with 1-s sampling resolution, and Total Suspended Particulate (TSP) filter samplers for measuring with hourly to daily sampling resolution. Significant differences in concentrations between burned and unburned sites were detectable in either short (1-s maximum) interval DustTrak PM10 measurements, or in longer term (weekly) BSNE horizontal sediment flux measurements, but not in intermediate-term (daily 5-h means) for either DustTrak PM10 or TSP measurements. The results highlight ongoing dust emissions during less windy periods and provide insight into the complex interplay among particle-size dependent measures and typical time scales measured.
1] The diverse and fundamental effects that aeolian processes have on the biosphere and geosphere... more 1] The diverse and fundamental effects that aeolian processes have on the biosphere and geosphere are commonly generated by horizontal sediment transport at the land surface. However, predicting horizontal sediment transport depends on vegetation architecture, which is difficult to quantify in a rapid but accurate manner. We demonstrate an approach to measure vegetation canopy architecture at high resolution using lidar along a gradient of dryland sites ranging from 2% to 73% woody plant canopy cover. Lidar-derived canopy height, distance (gaps) between vegetation elements (e.g., trunks, limbs, leaves), and the distribution of gaps scaled by vegetation height were correlated with canopy cover and highlight potentially improved horizontal dust flux estimation than with cover alone. Employing lidar to estimate detailed vegetation canopy architecture offers promise for improved predictions of horizontal sediment transport across heterogeneous plant assemblages. Citation: Sankey, J. B., D. J. Law, D. D. Breshears, S. M. Munson, and R. H. Webb (2013), Employing lidar to detail vegetation canopy architecture for prediction of aeolian transport,
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