Three C4 graminoids, Kyllinga nervosa, Themeda triandra, and Hyparrhenia filipendula, were grown ... more Three C4 graminoids, Kyllinga nervosa, Themeda triandra, and Hyparrhenia filipendula, were grown in unbalanced factorial treatment designs of clipping height, clipping frequency, watering frequency, and ni-trogen availability for periods equivalent to one growing season, after ...
... Three uncommon plant species (aspen, willow, and Wyoming big sagebrush Artemisia tridentata .... more ... Three uncommon plant species (aspen, willow, and Wyoming big sagebrush Artemisia tridentata ... assessment ungulates management native natural regulations. Francis J Singer, David M Swift ... Richard S Inouye, Nancy Huntly, G Wayne Minshall, JE Anderson in Biogeochemistry ...
Aims To identify approaches to improve our understanding of, and predictive capability for, mixed... more Aims To identify approaches to improve our understanding of, and predictive capability for, mixed tree-grass systems. Elucidation of the interactions, dynamics and determinants, and identification of robust generalizations that can be broadly applied to tree-grass systems would benefit ecological theory, modelling and land management.
Background/Question/Methods Cheatgrass (Bromus tectorum) is one of the most prolific invaders of ... more Background/Question/Methods Cheatgrass (Bromus tectorum) is one of the most prolific invaders of western rangelands, increasing fire frequency, decreasing wildlife and livestock habitat value and limiting the use of prescribed fire as a management tool. Once cheatgrass becomes established, it modifies the environment to create an ecologically stable state that is resilient to both successional processes and management intervention. The objective of the study reported here is to evaluate landscape scale constraints on conversion of perennial grass/shrublands to cheatgrass dominated stable states. Study sites were located in southeastern Wyoming and stratified by aspect and slope position along a fire chronosequence. Circular nested plots (CNP’s) were randomly located within these strata to measure effects on plant community. Results/Conclusions Field observations and preliminary analysis indicate that cheatgrass is more likely to persist on south facing aspects at low to mid elevatio...
Background/Question/Methods Bromus tectorum (cheatgrass) is one of the most widespread invasive s... more Background/Question/Methods Bromus tectorum (cheatgrass) is one of the most widespread invasive species in the western United States. In sagebrush steppe rangeland it alters fire frequency, soil moisture, and nutrient dynamics, decreasing the value of rangeland for wildlife and livestock and increasing costs associated with fire remediation and habitat restoration. Land managers have observed cheatgrass expansion into areas that were previously uninvaded in the Southern Rocky Mountain region. Currently cheatgrass invasion has been shown to exhibit positive feedbacks on plant community change, however, it is possible that management intervention soon after disturbance may restore negative feedbacks and promote recovery to a pre-disturbance community. We ask whether herbicide application can be used to avoid the process changes that cheatgrass can cause and promote desirable plant communities resistant to reinvasion. We collected baseline data on plant functional group cover in 8 burn...
Many ecological processes affect the amount of rainfall that infiltrates the soil profile and bec... more Many ecological processes affect the amount of rainfall that infiltrates the soil profile and becomes available for plant production. These processes include those that affect macroporosity and the soil surface condition, which influence the movement of water across the landscape and time available for infiltration. Simulation modelling provides a valuable means of exploring the effect of these processes on the retention or loss of resources from a system. This paper describes the eco-hydrological processes implemented in the SAVANNA.AU model in order to represent soil hydrology using a simple ecological approach and utilizing variables that are easily measured by managers and field ecologists.
Landscape scale modelling incorporates complex spatial and temporal processes (e.g. soil hydrolog... more Landscape scale modelling incorporates complex spatial and temporal processes (e.g. soil hydrology, runoff and sediment loss) operating at finer spatial resolutions than the model. It is important that these processes are accurately incorporated into larger scale models either intrinsically or extrinsically. Such hydrological factors ultimately determine plant production important for land use practices such as cattle grazing which occupies vast areas of northern Australia.
The ideal free distribution is a biological model that explains the abundance of predators relati... more The ideal free distribution is a biological model that explains the abundance of predators relative to their prey. This analysis reapplies this theory to examine the distribution of domestic livestock relative to the availability of water and forage along a 150km. transect in the Karakum Desert of Turkmenistan. In this arid environment, the location, quality and quantity of stock water
Grazing distribution patterns of large herbivores are affected by abiotic factors such as slope a... more Grazing distribution patterns of large herbivores are affected by abiotic factors such as slope and distance to water and by biotic factors such as forage quantity and quality. Abiotic factors are the primary determinants of large-scale distribution patterns and act as constraints within which mechanisms involving biotic factors operate. Usually there is a proportional relationship between the time large herbivores spend in a plant community and the available quantity and quality of forage. This grazing pattern may result from decisions made by animals at different spatial and temporal scales. Foraging velocity decreases and intake rate increases in areas of abundant palatable forage. These non-cognitive mechanisms that occur at smaller spatial scales (bites, feeding stations, small patches) could result in observed grazing patterns. However, large herbivores also appear to select areas (patches and feeding sites) to graze. Optimal foraging models and other models assume animals use "rules of thumb" to decide where to forage. A cognitive mechanism assumes animals use spatial memory in their foraging decisions. With such abilities, large herbivores could return to nutrient-rich sites more frequently than to nutrient-poor sites. Empirical studies indicate that large herbivores have accurate spatial memories and have the ability to use spatial memory to improve foraging efficiency. Body size and perceptual abilities can constrain the choices animals can make during foraging. A conceptual model was developed to demonstrate how cognitive foraging mechanisms could work within constraints imposed by abiotic factors. Preliminary predictions of the model correspond to observed grazing patterns. Recognizing that large herbivores may use previous experiences to decide where to forage may be useful in developing new techniques to modify grazing patterns. Grazing distribution patterns appear to result from decisions and processes made at a variety of spatial and temporal scales.
Wildlife management to reduce the impact of wildlife on their habitat can be done in several ways... more Wildlife management to reduce the impact of wildlife on their habitat can be done in several ways, among which removing animals (by either culling or translocation) is most often used. There are, however, alternative ways to control wildlife densities, such as opening or closing water points. The effects of these alternatives are poorly studied. In this paper, we focus on manipulating large herbivores through the closure of water points (WPs). Removal of artificial WPs has been suggested in order to change the distribution of African elephants, which occur in high densities in national parks in Southern Africa and are thought to have a destructive effect on the vegetation. Here, we modeled the long-term effects of different scenarios of WP closure on the spatial distribution of elephants, and consequential effects on the vegetation and other herbivores in Kruger National Park, South Africa. Using a dynamic ecosystem model, SAVANNA, scenarios were evaluated that varied in availability of artificial WPs; levels of natural water; and elephant densities. Our modeling results showed that elephants can indirectly negatively affect the distributions of meso-mixed feeders, meso-browsers, and some meso-grazers under wet conditions. The closure of artificial WPs hardly had any effect during these natural wet conditions. Under dry conditions, the spatial distribution of both elephant bulls and cows changed when the availability of artificial water was severely reduced in the model. These changes in spatial distribution triggered changes in the spatial availability of woody biomass over the simulation period of 80 years, and this led to changes in the rest of the herbivore community, resulting in increased densities of all herbivores, except for giraffe and steenbok, in areas close to rivers. The spatial distributions of elephant bulls and cows showed to be less affected by the closure of WPs than most of the other herbivore species. Our study contributes to ecologically informed decisions in wildlife management. The results from this modeling exercise imply that long-term effects of this intervention strategy should always be investigated at an ecosystem scale.
... number, and length of stem segments sampled from the tallest stems within the tallest plant s... more ... number, and length of stem segments sampled from the tallest stems within the tallest plant strata for 3 willow species (Salix monticola Bebb, Salix geyeriana ... Reviews by Brian Cade, Evan Wolf,Linda Zeigenfuss, and 3 anonymous referees greatly improved the manuscript. ...
The seasonal assimilation and within-plant partitioning of 14CO2-carbon and 35SO2-sulfur in field... more The seasonal assimilation and within-plant partitioning of 14CO2-carbon and 35SO2-sulfur in field plots of mixed-grass prairie was investigated, as was the dry deposition of 35SO2 onto surfaces of dead leaves, litter, and soil, and possible effects of continuous low-level SO2 fumigation on these processes. The proportion of total net-assimilated carbon found below-ground was 45% in May, 51% in July, and
Three C4 graminoids, Kyllinga nervosa, Themeda triandra, and Hyparrhenia filipendula, were grown ... more Three C4 graminoids, Kyllinga nervosa, Themeda triandra, and Hyparrhenia filipendula, were grown in unbalanced factorial treatment designs of clipping height, clipping frequency, watering frequency, and ni-trogen availability for periods equivalent to one growing season, after ...
... Three uncommon plant species (aspen, willow, and Wyoming big sagebrush Artemisia tridentata .... more ... Three uncommon plant species (aspen, willow, and Wyoming big sagebrush Artemisia tridentata ... assessment ungulates management native natural regulations. Francis J Singer, David M Swift ... Richard S Inouye, Nancy Huntly, G Wayne Minshall, JE Anderson in Biogeochemistry ...
Aims To identify approaches to improve our understanding of, and predictive capability for, mixed... more Aims To identify approaches to improve our understanding of, and predictive capability for, mixed tree-grass systems. Elucidation of the interactions, dynamics and determinants, and identification of robust generalizations that can be broadly applied to tree-grass systems would benefit ecological theory, modelling and land management.
Background/Question/Methods Cheatgrass (Bromus tectorum) is one of the most prolific invaders of ... more Background/Question/Methods Cheatgrass (Bromus tectorum) is one of the most prolific invaders of western rangelands, increasing fire frequency, decreasing wildlife and livestock habitat value and limiting the use of prescribed fire as a management tool. Once cheatgrass becomes established, it modifies the environment to create an ecologically stable state that is resilient to both successional processes and management intervention. The objective of the study reported here is to evaluate landscape scale constraints on conversion of perennial grass/shrublands to cheatgrass dominated stable states. Study sites were located in southeastern Wyoming and stratified by aspect and slope position along a fire chronosequence. Circular nested plots (CNP’s) were randomly located within these strata to measure effects on plant community. Results/Conclusions Field observations and preliminary analysis indicate that cheatgrass is more likely to persist on south facing aspects at low to mid elevatio...
Background/Question/Methods Bromus tectorum (cheatgrass) is one of the most widespread invasive s... more Background/Question/Methods Bromus tectorum (cheatgrass) is one of the most widespread invasive species in the western United States. In sagebrush steppe rangeland it alters fire frequency, soil moisture, and nutrient dynamics, decreasing the value of rangeland for wildlife and livestock and increasing costs associated with fire remediation and habitat restoration. Land managers have observed cheatgrass expansion into areas that were previously uninvaded in the Southern Rocky Mountain region. Currently cheatgrass invasion has been shown to exhibit positive feedbacks on plant community change, however, it is possible that management intervention soon after disturbance may restore negative feedbacks and promote recovery to a pre-disturbance community. We ask whether herbicide application can be used to avoid the process changes that cheatgrass can cause and promote desirable plant communities resistant to reinvasion. We collected baseline data on plant functional group cover in 8 burn...
Many ecological processes affect the amount of rainfall that infiltrates the soil profile and bec... more Many ecological processes affect the amount of rainfall that infiltrates the soil profile and becomes available for plant production. These processes include those that affect macroporosity and the soil surface condition, which influence the movement of water across the landscape and time available for infiltration. Simulation modelling provides a valuable means of exploring the effect of these processes on the retention or loss of resources from a system. This paper describes the eco-hydrological processes implemented in the SAVANNA.AU model in order to represent soil hydrology using a simple ecological approach and utilizing variables that are easily measured by managers and field ecologists.
Landscape scale modelling incorporates complex spatial and temporal processes (e.g. soil hydrolog... more Landscape scale modelling incorporates complex spatial and temporal processes (e.g. soil hydrology, runoff and sediment loss) operating at finer spatial resolutions than the model. It is important that these processes are accurately incorporated into larger scale models either intrinsically or extrinsically. Such hydrological factors ultimately determine plant production important for land use practices such as cattle grazing which occupies vast areas of northern Australia.
The ideal free distribution is a biological model that explains the abundance of predators relati... more The ideal free distribution is a biological model that explains the abundance of predators relative to their prey. This analysis reapplies this theory to examine the distribution of domestic livestock relative to the availability of water and forage along a 150km. transect in the Karakum Desert of Turkmenistan. In this arid environment, the location, quality and quantity of stock water
Grazing distribution patterns of large herbivores are affected by abiotic factors such as slope a... more Grazing distribution patterns of large herbivores are affected by abiotic factors such as slope and distance to water and by biotic factors such as forage quantity and quality. Abiotic factors are the primary determinants of large-scale distribution patterns and act as constraints within which mechanisms involving biotic factors operate. Usually there is a proportional relationship between the time large herbivores spend in a plant community and the available quantity and quality of forage. This grazing pattern may result from decisions made by animals at different spatial and temporal scales. Foraging velocity decreases and intake rate increases in areas of abundant palatable forage. These non-cognitive mechanisms that occur at smaller spatial scales (bites, feeding stations, small patches) could result in observed grazing patterns. However, large herbivores also appear to select areas (patches and feeding sites) to graze. Optimal foraging models and other models assume animals use "rules of thumb" to decide where to forage. A cognitive mechanism assumes animals use spatial memory in their foraging decisions. With such abilities, large herbivores could return to nutrient-rich sites more frequently than to nutrient-poor sites. Empirical studies indicate that large herbivores have accurate spatial memories and have the ability to use spatial memory to improve foraging efficiency. Body size and perceptual abilities can constrain the choices animals can make during foraging. A conceptual model was developed to demonstrate how cognitive foraging mechanisms could work within constraints imposed by abiotic factors. Preliminary predictions of the model correspond to observed grazing patterns. Recognizing that large herbivores may use previous experiences to decide where to forage may be useful in developing new techniques to modify grazing patterns. Grazing distribution patterns appear to result from decisions and processes made at a variety of spatial and temporal scales.
Wildlife management to reduce the impact of wildlife on their habitat can be done in several ways... more Wildlife management to reduce the impact of wildlife on their habitat can be done in several ways, among which removing animals (by either culling or translocation) is most often used. There are, however, alternative ways to control wildlife densities, such as opening or closing water points. The effects of these alternatives are poorly studied. In this paper, we focus on manipulating large herbivores through the closure of water points (WPs). Removal of artificial WPs has been suggested in order to change the distribution of African elephants, which occur in high densities in national parks in Southern Africa and are thought to have a destructive effect on the vegetation. Here, we modeled the long-term effects of different scenarios of WP closure on the spatial distribution of elephants, and consequential effects on the vegetation and other herbivores in Kruger National Park, South Africa. Using a dynamic ecosystem model, SAVANNA, scenarios were evaluated that varied in availability of artificial WPs; levels of natural water; and elephant densities. Our modeling results showed that elephants can indirectly negatively affect the distributions of meso-mixed feeders, meso-browsers, and some meso-grazers under wet conditions. The closure of artificial WPs hardly had any effect during these natural wet conditions. Under dry conditions, the spatial distribution of both elephant bulls and cows changed when the availability of artificial water was severely reduced in the model. These changes in spatial distribution triggered changes in the spatial availability of woody biomass over the simulation period of 80 years, and this led to changes in the rest of the herbivore community, resulting in increased densities of all herbivores, except for giraffe and steenbok, in areas close to rivers. The spatial distributions of elephant bulls and cows showed to be less affected by the closure of WPs than most of the other herbivore species. Our study contributes to ecologically informed decisions in wildlife management. The results from this modeling exercise imply that long-term effects of this intervention strategy should always be investigated at an ecosystem scale.
... number, and length of stem segments sampled from the tallest stems within the tallest plant s... more ... number, and length of stem segments sampled from the tallest stems within the tallest plant strata for 3 willow species (Salix monticola Bebb, Salix geyeriana ... Reviews by Brian Cade, Evan Wolf,Linda Zeigenfuss, and 3 anonymous referees greatly improved the manuscript. ...
The seasonal assimilation and within-plant partitioning of 14CO2-carbon and 35SO2-sulfur in field... more The seasonal assimilation and within-plant partitioning of 14CO2-carbon and 35SO2-sulfur in field plots of mixed-grass prairie was investigated, as was the dry deposition of 35SO2 onto surfaces of dead leaves, litter, and soil, and possible effects of continuous low-level SO2 fumigation on these processes. The proportion of total net-assimilated carbon found below-ground was 45% in May, 51% in July, and
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Papers by Michael Coughenour