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Russell L Scott - One of the best experts on this subject based on the ideXlab platform.
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long term decrease in satellite vegetation indices in response to environmental variables in an iconic desert Riparian Ecosystem the upper san pedro arizona united states
Ecohydrology, 2015Co-Authors: Uyen Nguyen, Edward P Glenn, Pamela L Nagler, Russell L ScottAbstract:The Upper San Pedro River is one of the few remaining undammed rivers that maintain a vibrant Riparian Ecosystem in the southwest United States. However, its Riparian forest is threatened by diminishing groundwater and surface water inputs, due to either changes in watershed characteristics such as changes in Riparian and upland vegetation, or human activities such as regional groundwater pumping. We used satellite vegetation indices to quantify the green leaf density of the groundwater-dependent Riparian forest from 1984 to 2012. The river was divided into a southern, upstream (mainly perennial flow) reach and a northern, downstream (mainly intermittent and ephemeral flow) reach. Pre-monsoon (June) Landsat normalized difference vegetation index (NDVI) values showed a 20% drop for the northern reach (P 0·05). NDVI and enhanced vegetation index values were positively correlated (P < 0·05) with river flows, which decreased over the study period in the northern reach, and negatively correlated (P < 0·05) with air temperatures in both reaches, which have increased by 1·4 °C from 1932 to 2012. NDVI in the uplands around the river did not increase from 1984 to 2012, suggesting that increased evapotranspiration in the uplands was not a factor in reducing river flows. Climate change, regional groundwater pumping, changes in the intensity of monsoon rain events and lack of overbank flooding are feasible explanations for deterioration of the Riparian forest in the northern reach. Copyright © 2014 John Wiley & Sons, Ltd.
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the water use of two dominant vegetation communities in a semiarid Riparian Ecosystem
Agricultural and Forest Meteorology, 2000Co-Authors: Russell L Scott, James W Shuttleworth, David C Goodrich, Thomas MaddockAbstract:Consumptive water use from Riparian evapotranspiration is a large component of many semiarid basins’ groundwater budgets — comparable in magnitude to mountain front recharge and surface water discharge. In most long-term groundwater studies the amount of water used by phreatophytes is estimated by empirical formulae and extrapolation of measurements taken elsewhere. These approaches are problematic due to the uncertainties regarding the vegetation’s water source (e.g., groundwater or recent precipitation) and its magnitude. Using micrometeorological techniques in this study, surface energy and water fluxes were measured for an annual cycle over two dominant types of vegetation in the Riparian floodplain of the San Pedro River in southeastern Arizona. The vegetation communities were a perennial, floodplain sacaton grassland (Sporobolus wrightii) and a tree/shrub grouping composed largely of mesquite (Prosopis velutina). These measurements are compared with estimates from previous studies. Additionally, measurements of soil water content and water table levels are used to infer the dominant sources of the evaporated water. The results indicate that the grassland relied primarily on recent precipitation, while the mesquite obtained water from deeper in the soil profile. Neither appears to be strongly phreatophytic, which suggests that the dominant, natural groundwater withdrawals in the Upper San Pedro Basin are mainly confined to the narrow cottonwood/willow gallery that lines the river. © 2000 Elsevier Science B.V. All rights reserved.
Matthew N Baillie - One of the best experts on this subject based on the ideXlab platform.
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quantifying water sources to a semiarid Riparian Ecosystem san pedro river arizona
Journal of Geophysical Research, 2007Co-Authors: Matthew N Baillie, James F Hogan, Brenda Ekwurzel, Arun K Wahi, Christopher J EastoeAbstract:[1] The Upper San Pedro River Basin (Southeastern Arizona, United States) contains one of the few desert Riparian areas in the Southwest, a system that is dependent on both shallow groundwater to support phreatic vegetation and baseflow for aquatic plants and animals. Proper management decisions for sustaining this biodiversity hotspot require understanding the hydrology of the Riparian system and its interaction with the basin aquifer. To meet this need and to assess whether the techniques used would be efficient for evaluating other semiarid Riparian Ecosystems, we addressed the following questions. What are the contributions of different water sources (e.g., local recharge during monsoon flood events versus inflow of basin groundwater) to Riparian groundwater and river baseflow? How does the spatial variability in water sources relate to gaining and losing reaches along of the river? We first characterize the possible water sources to the Riparian system using a suite of geochemical tracers. Results indicate that, of the possible sources, basin groundwater recharged along the Huachuca Mountains to the west and local recharge of monsoon floodwaters are the dominant Riparian water sources. Then, using their geochemical composition, we quantify these sources using a two end-member mixing model. We find that Riparian groundwater composition varies between gaining and losing reaches. Locally recharged monsoon floodwater comprises 60 to 85% of Riparian groundwater in losing reaches whereas that of gaining reaches contains only 10% to 40%. Baseflow, sampled year round, also contains a significant component of monsoon floodwater ranging from 80% on the upstream end and decreasing to 55% after passing though several gaining reaches. These results highlight the significance of local recharge during monsoon flood events as a water source for desert Riparian systems, a fact that should be addressed when constructing and calibrating hydrologic models used to evaluate these future water management decisions.
Juliet C Stromberg - One of the best experts on this subject based on the ideXlab platform.
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propagule banks potential contribution to restoration of an impounded and dewatered Riparian Ecosystem
Wetlands, 2008Co-Authors: Jere A Boudell, Juliet C StrombergAbstract:The Agua Fria River in Arizona’s Sonoran Desert was impounded and diverted more than 70 years ago. Immediately below New Waddell dam there are semi-permanent pools, but water has been released into the channel only during rare wet years. To determine whether a propagule bank exists below the dam, and whether it could contribute to the revegetation of the Agua Fria Riparian Ecosystem should flow be restored to the dewatered reach, we collected 45 soil cores from four plant associations. We examined species in the samples in a growth chamber using the seedling emergence method. A total of 74 species (mostly herbaceous) and an abundance of individuals were present in propagule banks. The propagule banks were similar to those of a free-flowing reference river despite considerable differences in extant vegetation. Riparian species were present in propagule banks of all four associations and were the dominant type in three (Tamarix forests, Tamarix-Salix forests, and Baccharis-Bebbia shrublands). Propagule distribution varied with soil depth in three of the associations (Tamarix forests and the two xerophytic shrublands) with Riparian species more prevalent in deep sediment and upland species more prevalent in surface soil and litter. Collectively these patterns suggest that a Riparian legacy is present in Agua Fria propagule banks. However, Riparian propagule density was low in the Hymenoclea-Bebbia shrublands, reflecting xerification of the Riparian corridor. Given the physical barrier of the dam, continued diversion of stream flow, and rare flood releases, local inputs from xerophytes will dominate propagule bank dynamics in the future. Although propagule banks could contribute to redevelopment of the herbaceous component of the vegetation should stream flows be restored to this river reach, the Riparian legacy likely will decline over time as Riparian propagules reach the end of their lifespan while propagules of xerophytes continue to be replenished.
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differences in seed mass between hydric and xeric plants influence seed bank dynamics in a dryland Riparian Ecosystem
Functional Ecology, 2008Co-Authors: Juliet C Stromberg, Jere A Boudell, Andrea F HazeltonAbstract:Summary 1. Dryland Riparian zones have steep spatial gradients of soil moisture and flood disturbance, and the component hydrogeomorphic surfaces support hydric to xeric plant species. These systems undergo extremes of flood and drought, a dynamic that may select for persistent soil seed banks. We asked if reliance on this strategy differed among plants in three moisture groups (hydric, mesic and xeric), and if patterns were related to diaspore traits. 2. We assessed the composition of soil and litter seed banks (emergence method) and extant vegetation along a Riparian hydrogradient, and measured seed persistence (using an indirect method) and diaspore mass and shape variance of the component species. 3. HydroRiparian species had smaller diaspores than xeroRiparian species, corresponding to differences in selective pressures on seedlings in their respective habitats, but the two groups formed persistent seed banks at approximately equal percentages. Persistent seeds were smaller than transient seeds, but within the persistent seed group there was separation between the smaller-diaspored hydrophytes and larger-diaspored xerophytes. 4. Distribution patterns of extant vegetation, in concert with diaspore trait differences among moisture-affinity groups, gave rise to divergent spatial patterns of diaspores within the soil: hydroRiparian diaspores were abundant not only along wet channel bars but also in deep soils under floodplain forests and shrublands, presumably owing to dispersal by flood waters. XeroRiparian diaspores were largely restricted to the litter and upper soil layers of their drier, higher, floodplain habitats. With increasing depth in the soil of floodplain forests and shrublands, viable diaspores became smaller and rounder, and plant composition shifted from xeroRiparian to hydroRiparian species. 5. The wide distribution of hydroRiparian diaspores in floodplain soils influences disturbance dynamics, increasing the probability that ephemeral wetland communities will develop wherever suitable conditions are stochastically created by floods. Persistent seed banks also allow many xeric annuals to be maintained in dryland Riparian zones throughout extended drought, similar to processes that occur in desert uplands.
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flood pulsing and metacommunity dynamics in a desert Riparian Ecosystem
Journal of Vegetation Science, 2008Co-Authors: Jere A Boudell, Juliet C StrombergAbstract:Abstract Questions: 1. Does flood pulsing drive metacommunity dynamics and provide insurance against catastrophic flooding in desert southwestern Riparian Ecosystems? 2. Do upland and wetland species in the floodplain differ in their dynamics? Location: Southwestern USA. Methods: We sampled vegetation and propagule banks in four communities along a floodplain hydrogradient. Plant species were classified as wetland or upland and community wetland indicator scores were calculated. ANOVA tested for differences between data categories amongst communities (extant vegetation and propagule banks) and soil depths. Sorensen's similarity coefficient was calculated to determine compositional similarity between vegetation and propagule banks. Results: Community propagule banks had high similarity indicating broad dispersal by flood waters. Wetland propagules were present in soils from channel bars to floodplain edges, despite declines in wetland vegetation with distance from channel. Wetland communities in propagule ...
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status of the Riparian Ecosystem in the upper san pedro river arizona application of an assessment model
Environmental Monitoring and Assessment, 2006Co-Authors: Juliet C Stromberg, Sharon J Lite, Tyler Rychener, Lainie R Levick, Mark D Dixon, Joseph M WattsAbstract:A portion of Arizona’s San Pedro River is managed as a National Riparian Conservation Area but is potentially affected by ground-water withdrawals beyond the conservation area borders. We applied an assessment model to the Conservation Area as a basis for monitoring long-term changes in Riparian Ecosystem condition resulting from changes in river water availability, and collected multi-year data on a subset of the most sensitive bioindicators. The assessment model is based on nine vegetation bioindicators that are sensitive to changes in surface water or ground water. Site index scores allow for placement into one of three condition classes, each reflecting particular ranges for site hydrology and vegetation structure. We collected the bioindicator data at 26 sites distributed among 14 reaches that had similar stream flow hydrology (spatial flow intermittency) and geomorphology (channel sinuosity, flood-plain width). Overall, 39% of the Riparian corridor fell within condition class 3 (the wettest condition), 55% in condition class 2, and 6% in the driest condition class. Condition class 3 reaches have high cover of herbaceous wetland plants (e.g., Juncus and Schoenoplectus spp.) along the perennial stream channel and dense, multi-aged Populus-Salix woodlands in the flood plain, sustained by shallow ground water in the stream alluvium. In condition class 2, intermittent stream flows result in low cover of streamside wetland herbs, but Populus-Salix remain abundant in the flood plain. Perennial wetland plants are absent from condition class 1, reflecting highly intermittent stream flows; the flood plain is vegetated by Tamarixa small tree that tolerates the deep and fluctuating ground water levels that typify this reach type. Abundance of herbaceous wetland plants and growth rate of Salix gooddingii varied between years with different stream flow rates, indicating utility of these measures for tracking short-term responses to hydrologic change. Repeat measurement of all bioindicators will indicate long-term trends in hydro-vegetational condition.
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arbuscular mycorrhizal fungi associated with populus salix stands in a semiarid Riparian Ecosystem
New Phytologist, 2006Co-Authors: Juliet C Stromberg, Vanessa B Beauchamp, Jean C StutzAbstract:Summary • This study examined the activity, species richness, and species composition of the arbuscular mycorrhizal fungal (AMF) community of Populus–Salix stands on the Verde River (Arizona, USA), quantified patterns of AMF richness and colonization along complex floodplain gradients, and identified environmental variables responsible for structuring the AMF community. • Samples from 61 Populus–Salix stands were analyzed for AMF and herbaceous composition, AMF colonization, gravimetric soil moisture, soil texture, per cent organic matter, pH, and concentrations of nitrate, bicarbonate phosphorus and exchangeable potassium. • AMF species richness declined with stand age and distance from and elevation above the channel and was positively related to perennial species cover and richness and gravimetric soil moisture. Distance from and elevation above the active channel, forest age, annual species cover, perennial species richness, and exchangeable potassium concentration all played a role in structuring the AMF community in this Riparian area. • Most AMF species were found across a wide range of soil conditions, but a subset of species tended to occur more often in hydric areas. This group of Riparian affiliate AMF species includes several not previously encountered in the surrounding Sonoran desert.
Christopher J Eastoe - One of the best experts on this subject based on the ideXlab platform.
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quantifying water sources to a semiarid Riparian Ecosystem san pedro river arizona
Journal of Geophysical Research, 2007Co-Authors: Matthew N Baillie, James F Hogan, Brenda Ekwurzel, Arun K Wahi, Christopher J EastoeAbstract:[1] The Upper San Pedro River Basin (Southeastern Arizona, United States) contains one of the few desert Riparian areas in the Southwest, a system that is dependent on both shallow groundwater to support phreatic vegetation and baseflow for aquatic plants and animals. Proper management decisions for sustaining this biodiversity hotspot require understanding the hydrology of the Riparian system and its interaction with the basin aquifer. To meet this need and to assess whether the techniques used would be efficient for evaluating other semiarid Riparian Ecosystems, we addressed the following questions. What are the contributions of different water sources (e.g., local recharge during monsoon flood events versus inflow of basin groundwater) to Riparian groundwater and river baseflow? How does the spatial variability in water sources relate to gaining and losing reaches along of the river? We first characterize the possible water sources to the Riparian system using a suite of geochemical tracers. Results indicate that, of the possible sources, basin groundwater recharged along the Huachuca Mountains to the west and local recharge of monsoon floodwaters are the dominant Riparian water sources. Then, using their geochemical composition, we quantify these sources using a two end-member mixing model. We find that Riparian groundwater composition varies between gaining and losing reaches. Locally recharged monsoon floodwater comprises 60 to 85% of Riparian groundwater in losing reaches whereas that of gaining reaches contains only 10% to 40%. Baseflow, sampled year round, also contains a significant component of monsoon floodwater ranging from 80% on the upstream end and decreasing to 55% after passing though several gaining reaches. These results highlight the significance of local recharge during monsoon flood events as a water source for desert Riparian systems, a fact that should be addressed when constructing and calibrating hydrologic models used to evaluate these future water management decisions.
Thomas Maddock - One of the best experts on this subject based on the ideXlab platform.
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the water use of two dominant vegetation communities in a semiarid Riparian Ecosystem
Agricultural and Forest Meteorology, 2000Co-Authors: Russell L Scott, James W Shuttleworth, David C Goodrich, Thomas MaddockAbstract:Consumptive water use from Riparian evapotranspiration is a large component of many semiarid basins’ groundwater budgets — comparable in magnitude to mountain front recharge and surface water discharge. In most long-term groundwater studies the amount of water used by phreatophytes is estimated by empirical formulae and extrapolation of measurements taken elsewhere. These approaches are problematic due to the uncertainties regarding the vegetation’s water source (e.g., groundwater or recent precipitation) and its magnitude. Using micrometeorological techniques in this study, surface energy and water fluxes were measured for an annual cycle over two dominant types of vegetation in the Riparian floodplain of the San Pedro River in southeastern Arizona. The vegetation communities were a perennial, floodplain sacaton grassland (Sporobolus wrightii) and a tree/shrub grouping composed largely of mesquite (Prosopis velutina). These measurements are compared with estimates from previous studies. Additionally, measurements of soil water content and water table levels are used to infer the dominant sources of the evaporated water. The results indicate that the grassland relied primarily on recent precipitation, while the mesquite obtained water from deeper in the soil profile. Neither appears to be strongly phreatophytic, which suggests that the dominant, natural groundwater withdrawals in the Upper San Pedro Basin are mainly confined to the narrow cottonwood/willow gallery that lines the river. © 2000 Elsevier Science B.V. All rights reserved.
