Abstract Few old-field succession studies have been conducted in arid ecosystems and there is som... more Abstract Few old-field succession studies have been conducted in arid ecosystems and there is some question if classical secondary succession occurs in arid environments. In order to determine if old-field succession does occur under arid conditions, we sampled 40 previously-cultivated sites abandoned over a period of 29–80 years in the Owens Valley, California. We compared vegetation development at these 40 old fields to vegetation composition on 17 adjacent uncultivated reference sites. We were interested in determining if 1) seral communities could be identified, 2) these communities expressed predictable and progressive patterns, and 3) if so, whether the seral patterns indicated divergent or convergent successional pathways. The 57 sites separated into 6 separate seral communities. Two seres were identified, one progressing toward a big sagebrush late-seral community and the other with fourwing saltbush as the characteristic species. Based on multivariate statistical analysis, the two seres were likely to continue on divergent pathways for 100–140 years, after which the saltbush sere may converge toward the late-seral sagebrush community. Both localized and broad-scale factors were important in defining successional patterns in this arid environment. Our results support the concept that classical old-field succession does occur in arid regions.
: EDYS (Ecological DYnamics Simulation Model) is a general ecosystem simulation model that is mec... more : EDYS (Ecological DYnamics Simulation Model) is a general ecosystem simulation model that is mechanistically based and spatially explicit. The model simulates natural and anthropogenic-induced changes in plant, soil, animal, and watershed components across landscapes, at spatial scales ranging from 1 m2 or less to landscape levels (103 km and larger). It is a dynamic model that simulates changes on a daily basis over periods ranging from months to centuries. EDYS has also been linked with groundwater (MODFLOW) and surface runoff (GSSHA, CASC2D, HSPF) models to provide integrated watershed management simulation systems.
... Current Status 24 3 Applications 27 Strategy for Land Management 27 Fort Hood, Texas 30 Fort ... more ... Current Status 24 3 Applications 27 Strategy for Land Management 27 Fort Hood, Texas 30 Fort Bliss, Texas 32 US Air Force Academy, Colorado 34 Hydrological Applications 37 4 Future Development and Applications 40 Internet Access 40 EDYS Database Development 41 ...
ABSTRACT We analyzed temporal and spatial patterns of water use by a functionally-diverse group o... more ABSTRACT We analyzed temporal and spatial patterns of water use by a functionally-diverse group of Great Basin plant species and determined their water use rates at the whole-plant and individual-leaf scales under variable summer watering. Species studied were the desert grasses Distichlis spicata and Sporobolus airoides, the desert shrubs Artemisia tridentata, Ericameria nauseosa, and Atriplex confertifolia; the wetland/riparian plants Juncus arcticus, Leymus triticoides, and Salix exigua; and the annual exotic Salsola tragus. Plant species were individually grown in 5.8 m2 plots in a common garden in eastern California. Three irrigation treatments in the form of monthly pulses were applied during the summer: low (1.3 cm), medium (2.6 cm), and high (3.9 cm), in addition to a non-irrigated control. Whole-plant water uptake characteristics were determined by soil water depletion at different soil depths, while leaf transpiration was determined by gas exchange. Whole-plant water extraction and leaf transpiration varied similarly among species. Desert shrubs had low water extraction (35 to 395 g m-2 day-1) and were not affected by irrigation. The desert grasses and riparian/wetland species had higher water extraction, increasing with irrigation levels. L. triticoides and J. arcticus had the highest water extraction overall (> 2,000 g m-2 day-1). Desert shrubs relied 10 times more on deeper water sources than herbaceous species. The average T/ET was 31%, but varied by species. Summer available water in environments such as the Great Basin favors desert grasses and riparian/wetland species, but not desert shrubs. The observed species differences provide alternatives for water and vegetation management.
INTRODUCTION: EDYS (Ecological DYnamics Simulation Model) is a general ecosystem simulation model... more INTRODUCTION: EDYS (Ecological DYnamics Simulation Model) is a general ecosystem simulation model that is mechanistically based and spatially explicit (Childress and McLendon 1999; Childress et al. 1999, 2002). The model simulates natural and anthropogenic-induced changes in plant, soil, animal, and watershed components across landscapes, at spatial scales ranging from 1 m2 or less to landscape levels (103 km and larger). It is a dynamic model that
INTRODUCTION: EDYS (Ecological DYnamics Simulation Model) is a general ecosystem simulation model... more INTRODUCTION: EDYS (Ecological DYnamics Simulation Model) is a general ecosystem simulation model that is mechanistically based and spatially explicit (Childress and McLendon 1999; Childress et al. 1999, 2002). The model simulates natural and anthropogenic-induced changes in plant, soil, animal, and watershed components across landscapes, at spatial scales ranging from 1 m2 or less to landscape levels (103 km and larger). It is a dynamic model that
Conservation management practices such as no-tillage and cover cropping can reduce soil erosion, ... more Conservation management practices such as no-tillage and cover cropping can reduce soil erosion, enhance soil biological activity, increase water capture and storage, and sequester C. Cover crops, however, utilize stored soil water during the winter months, and the water depletion is thought to have negative impacts on the subsequent cotton (Gossypium hirsutum L.) crop in semi-arid ecoregions where water resources are limited. The objective of this research was to quantify the long-term impacts of conservation tillage and cover crop use on volumetric water content of soil in an irrigated cotton production system. Soil water was measured in a long-term (established 1998) conservation system in Lamesa, TX and water dynamics during the 2015–2017 growing seasons are presented here. Volumetric water content was reduced by cover crops prior to their termination but was replenished by spring precipitation and deficit irrigation prior to planting cotton. A stepwise regression analysis was u...
: Precipitation patterns, including the effects of long-term droughts or above average precipitat... more : Precipitation patterns, including the effects of long-term droughts or above average precipitation and the interactions with nitrogen availability, often have enough influence on plant growth that the effects of our use or management of land are not apparent. This is especially true because of the need to judge changes in land condition over periods of months to years. One of the primary information requirements identified by Army land managers and trainers is the need to be able to project the impacts of training and management strategies on the amount of plant cover protecting the soil. Managers also need to know how long it takes a plant community to recover to the desired plant cover level after use. The purpose of this research project was to test the ability of the Ecological Dynamics Simulation (EDYS) model to accurately project plant dynamics given a wide range of precipitation patterns and nitrogen availability over a period of years to decades. The results of this resear...
A soil microcosm experiment was used to analyze effects of depleted uranium on soil community fun... more A soil microcosm experiment was used to analyze effects of depleted uranium on soil community function. Uranium treatment levels were 0, 50, 500, 5,000, 10,000, and 25,000 ppm. Decomposition was followed through measurement of mass loss of several different plant litter types, as well as through analysis of soil respiration. Litter types tested were lignin, cellulose, and both high-nitrogen and low-nitrogen grass. Functional diversity of soil bacteria was assessed using the BIOLOG system of sole carbon source utilization. There was a significant reduction in litter decomposition at the 25,000 ppm level versus the control for all litter types except the high-nitrogen grass. Changes in functional diversity of the soil bacterial communities were more pronounced. Changes were observed both in terms of the number of carbon sources utilized, as well as in the intensity of utilization.
: The purpose of the Land Condition Trend Analysis (LCTA) program at the Marine Air Ground Task F... more : The purpose of the Land Condition Trend Analysis (LCTA) program at the Marine Air Ground Task Force Training Command (MAGTFTC), Twentynine Palms, California, is to support natural resource management decision making. The LCTA monitoring program collects the data necessary to (1) determine effects of military activity on both the current ecological condition of MAGTFTC and the trend in this condition, (2) help characterize the relationship between military impacts and the type, location, timing, intensity, and duration of training, and (3) characterize plant communities on MAGTFTC. This report assesses the strengths and weaknesses of the current LCTA program and offers recommendations for improvements. The current LCTA Protocol meets its primary purpose by addressing the effect of training on the bajada areas of MAGTFTC and providing information for management of this type of site. Albeit a secondary purpose, the Protocol inadequately samples the variability in the overall vegetati...
: The U.S. Army Engineer District, Fort Worth (CESWF) is involved in demon- strating the utility ... more : The U.S. Army Engineer District, Fort Worth (CESWF) is involved in demon- strating the utility of an ecological model in the performance and interpretation of a comprehensive General Investigations (GI) study of the Cibolo Creek watershed upstream of Interstate 10 near San Antonio, Texas. Partners to the District in this project are the Natural Resources Conservation Service (NRCS), U.S. Geological Survey (USGS), and U.S. Fish and Wildlife Service (USFW). Project sponsors are the Guadalupe-Blanco River Authority (GBRA), San Antonio River Authority (SARA), and San Antonio Water System (SAWS). CESWF requested assistance from the U.S. Army Engineer Research and Development Center (ERDC) in conducting this study. The first phase of the study was to establish existing conditions of the hydrologic, engineering, economic, and environmental aspects of the study area, and to demonstrate watershed modeling tools. The second phase will evaluate a recharge/dry detention structure to identify ...
Uptake of depleted uranium (DU, U) derived from weathered munitions was assessed in a greenhouse ... more Uptake of depleted uranium (DU, U) derived from weathered munitions was assessed in a greenhouse experiment utilizing three common grass species, Schizachyrium scoparium (little bluestem), Buchloe dactyloides (buffalograss), and Aristida purpurea (purple threeawn). Both aboveground and belowground uptake was dependent on the soil DU concentration, and on the experimental moisture regime utilized during the experimental duration. Uptake was enhanced under
Abstract Few old-field succession studies have been conducted in arid ecosystems and there is som... more Abstract Few old-field succession studies have been conducted in arid ecosystems and there is some question if classical secondary succession occurs in arid environments. In order to determine if old-field succession does occur under arid conditions, we sampled 40 previously-cultivated sites abandoned over a period of 29–80 years in the Owens Valley, California. We compared vegetation development at these 40 old fields to vegetation composition on 17 adjacent uncultivated reference sites. We were interested in determining if 1) seral communities could be identified, 2) these communities expressed predictable and progressive patterns, and 3) if so, whether the seral patterns indicated divergent or convergent successional pathways. The 57 sites separated into 6 separate seral communities. Two seres were identified, one progressing toward a big sagebrush late-seral community and the other with fourwing saltbush as the characteristic species. Based on multivariate statistical analysis, the two seres were likely to continue on divergent pathways for 100–140 years, after which the saltbush sere may converge toward the late-seral sagebrush community. Both localized and broad-scale factors were important in defining successional patterns in this arid environment. Our results support the concept that classical old-field succession does occur in arid regions.
: EDYS (Ecological DYnamics Simulation Model) is a general ecosystem simulation model that is mec... more : EDYS (Ecological DYnamics Simulation Model) is a general ecosystem simulation model that is mechanistically based and spatially explicit. The model simulates natural and anthropogenic-induced changes in plant, soil, animal, and watershed components across landscapes, at spatial scales ranging from 1 m2 or less to landscape levels (103 km and larger). It is a dynamic model that simulates changes on a daily basis over periods ranging from months to centuries. EDYS has also been linked with groundwater (MODFLOW) and surface runoff (GSSHA, CASC2D, HSPF) models to provide integrated watershed management simulation systems.
... Current Status 24 3 Applications 27 Strategy for Land Management 27 Fort Hood, Texas 30 Fort ... more ... Current Status 24 3 Applications 27 Strategy for Land Management 27 Fort Hood, Texas 30 Fort Bliss, Texas 32 US Air Force Academy, Colorado 34 Hydrological Applications 37 4 Future Development and Applications 40 Internet Access 40 EDYS Database Development 41 ...
ABSTRACT We analyzed temporal and spatial patterns of water use by a functionally-diverse group o... more ABSTRACT We analyzed temporal and spatial patterns of water use by a functionally-diverse group of Great Basin plant species and determined their water use rates at the whole-plant and individual-leaf scales under variable summer watering. Species studied were the desert grasses Distichlis spicata and Sporobolus airoides, the desert shrubs Artemisia tridentata, Ericameria nauseosa, and Atriplex confertifolia; the wetland/riparian plants Juncus arcticus, Leymus triticoides, and Salix exigua; and the annual exotic Salsola tragus. Plant species were individually grown in 5.8 m2 plots in a common garden in eastern California. Three irrigation treatments in the form of monthly pulses were applied during the summer: low (1.3 cm), medium (2.6 cm), and high (3.9 cm), in addition to a non-irrigated control. Whole-plant water uptake characteristics were determined by soil water depletion at different soil depths, while leaf transpiration was determined by gas exchange. Whole-plant water extraction and leaf transpiration varied similarly among species. Desert shrubs had low water extraction (35 to 395 g m-2 day-1) and were not affected by irrigation. The desert grasses and riparian/wetland species had higher water extraction, increasing with irrigation levels. L. triticoides and J. arcticus had the highest water extraction overall (> 2,000 g m-2 day-1). Desert shrubs relied 10 times more on deeper water sources than herbaceous species. The average T/ET was 31%, but varied by species. Summer available water in environments such as the Great Basin favors desert grasses and riparian/wetland species, but not desert shrubs. The observed species differences provide alternatives for water and vegetation management.
INTRODUCTION: EDYS (Ecological DYnamics Simulation Model) is a general ecosystem simulation model... more INTRODUCTION: EDYS (Ecological DYnamics Simulation Model) is a general ecosystem simulation model that is mechanistically based and spatially explicit (Childress and McLendon 1999; Childress et al. 1999, 2002). The model simulates natural and anthropogenic-induced changes in plant, soil, animal, and watershed components across landscapes, at spatial scales ranging from 1 m2 or less to landscape levels (103 km and larger). It is a dynamic model that
INTRODUCTION: EDYS (Ecological DYnamics Simulation Model) is a general ecosystem simulation model... more INTRODUCTION: EDYS (Ecological DYnamics Simulation Model) is a general ecosystem simulation model that is mechanistically based and spatially explicit (Childress and McLendon 1999; Childress et al. 1999, 2002). The model simulates natural and anthropogenic-induced changes in plant, soil, animal, and watershed components across landscapes, at spatial scales ranging from 1 m2 or less to landscape levels (103 km and larger). It is a dynamic model that
Conservation management practices such as no-tillage and cover cropping can reduce soil erosion, ... more Conservation management practices such as no-tillage and cover cropping can reduce soil erosion, enhance soil biological activity, increase water capture and storage, and sequester C. Cover crops, however, utilize stored soil water during the winter months, and the water depletion is thought to have negative impacts on the subsequent cotton (Gossypium hirsutum L.) crop in semi-arid ecoregions where water resources are limited. The objective of this research was to quantify the long-term impacts of conservation tillage and cover crop use on volumetric water content of soil in an irrigated cotton production system. Soil water was measured in a long-term (established 1998) conservation system in Lamesa, TX and water dynamics during the 2015–2017 growing seasons are presented here. Volumetric water content was reduced by cover crops prior to their termination but was replenished by spring precipitation and deficit irrigation prior to planting cotton. A stepwise regression analysis was u...
: Precipitation patterns, including the effects of long-term droughts or above average precipitat... more : Precipitation patterns, including the effects of long-term droughts or above average precipitation and the interactions with nitrogen availability, often have enough influence on plant growth that the effects of our use or management of land are not apparent. This is especially true because of the need to judge changes in land condition over periods of months to years. One of the primary information requirements identified by Army land managers and trainers is the need to be able to project the impacts of training and management strategies on the amount of plant cover protecting the soil. Managers also need to know how long it takes a plant community to recover to the desired plant cover level after use. The purpose of this research project was to test the ability of the Ecological Dynamics Simulation (EDYS) model to accurately project plant dynamics given a wide range of precipitation patterns and nitrogen availability over a period of years to decades. The results of this resear...
A soil microcosm experiment was used to analyze effects of depleted uranium on soil community fun... more A soil microcosm experiment was used to analyze effects of depleted uranium on soil community function. Uranium treatment levels were 0, 50, 500, 5,000, 10,000, and 25,000 ppm. Decomposition was followed through measurement of mass loss of several different plant litter types, as well as through analysis of soil respiration. Litter types tested were lignin, cellulose, and both high-nitrogen and low-nitrogen grass. Functional diversity of soil bacteria was assessed using the BIOLOG system of sole carbon source utilization. There was a significant reduction in litter decomposition at the 25,000 ppm level versus the control for all litter types except the high-nitrogen grass. Changes in functional diversity of the soil bacterial communities were more pronounced. Changes were observed both in terms of the number of carbon sources utilized, as well as in the intensity of utilization.
: The purpose of the Land Condition Trend Analysis (LCTA) program at the Marine Air Ground Task F... more : The purpose of the Land Condition Trend Analysis (LCTA) program at the Marine Air Ground Task Force Training Command (MAGTFTC), Twentynine Palms, California, is to support natural resource management decision making. The LCTA monitoring program collects the data necessary to (1) determine effects of military activity on both the current ecological condition of MAGTFTC and the trend in this condition, (2) help characterize the relationship between military impacts and the type, location, timing, intensity, and duration of training, and (3) characterize plant communities on MAGTFTC. This report assesses the strengths and weaknesses of the current LCTA program and offers recommendations for improvements. The current LCTA Protocol meets its primary purpose by addressing the effect of training on the bajada areas of MAGTFTC and providing information for management of this type of site. Albeit a secondary purpose, the Protocol inadequately samples the variability in the overall vegetati...
: The U.S. Army Engineer District, Fort Worth (CESWF) is involved in demon- strating the utility ... more : The U.S. Army Engineer District, Fort Worth (CESWF) is involved in demon- strating the utility of an ecological model in the performance and interpretation of a comprehensive General Investigations (GI) study of the Cibolo Creek watershed upstream of Interstate 10 near San Antonio, Texas. Partners to the District in this project are the Natural Resources Conservation Service (NRCS), U.S. Geological Survey (USGS), and U.S. Fish and Wildlife Service (USFW). Project sponsors are the Guadalupe-Blanco River Authority (GBRA), San Antonio River Authority (SARA), and San Antonio Water System (SAWS). CESWF requested assistance from the U.S. Army Engineer Research and Development Center (ERDC) in conducting this study. The first phase of the study was to establish existing conditions of the hydrologic, engineering, economic, and environmental aspects of the study area, and to demonstrate watershed modeling tools. The second phase will evaluate a recharge/dry detention structure to identify ...
Uptake of depleted uranium (DU, U) derived from weathered munitions was assessed in a greenhouse ... more Uptake of depleted uranium (DU, U) derived from weathered munitions was assessed in a greenhouse experiment utilizing three common grass species, Schizachyrium scoparium (little bluestem), Buchloe dactyloides (buffalograss), and Aristida purpurea (purple threeawn). Both aboveground and belowground uptake was dependent on the soil DU concentration, and on the experimental moisture regime utilized during the experimental duration. Uptake was enhanced under
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