Geology topics

D.C. Andersen

Publications and source records attributed to D.C. Andersen.

16 recordsLinked to original sources

USGS2013

Floral ecology and insect visitation in riparian Tamarix sp. (saltcedar)

Climate change projections for semiarid and arid North America include reductions in stream discharge that could adversely affect riparian plant species dependent on stream-derived ground water. In order to better understand this potential impact, we used a space-for-time substitution to test the hypotheses that increasing depth-to-groundwater (DGW) is inversely related to Tamarix sp. (saltcedar) flower abundance (F) and nectar production per flower (N). We also assessed whether DGW affected the richness or abundance of insects visiting flowers. We examined Tamarix floral attributes and insect visitation patterns during 2010 and 2011 at three locations along a deep DWG gradient (3.2–4.1 m) on a floodplain terrace adjacent to Las Vegas Wash, an effluent-dominated Mojave Desert stream. Flower abundance and insect visitation patterns differed between years, but no effect from DGW on either F or N was detected. An eruption of a novel non-native herbivore, the splendid tamarisk weevil (Coniatus splendidulus), likely reduced flower production in 2011.

Journal of Arid Environments↗

USGS2011

Managed flood effects on beaver pond habitat in a desert riverine ecosystem, bill williams river, Arizona USA

The ecological effects of beaver in warm-desert streams are poorly documented, but potentially significant. For example, stream water and sediment budgets may be affected by increased evaporative losses and sediment retention in beaver ponds. We measured physical attributes of beaver pond and adjacent lotic habitats on a regulated Sonoran Desert stream, the Bill Williams River, after ???11 flood-free months in Spring 2007 and Spring 2008. Neither a predicted warming of surface water as it passed through a pond nor a reduction in dissolved oxygen in ponds was consistently observed, but bed sediment sorted to finest in ponds as expected. We observed a river segment-scale downstream rise in daily minimum stream temperature that may have been influenced by the series of ??100 beaver ponds present. Channel cross-sections surveyed before and after an experimental flood (peak flow 65 m3/s) showed net aggradation on nine of 13 cross-sections through ponds and three of seven through lotic reaches. Our results indicate that beaver affect riverine processes in warm deserts much as they do in other biomes. However, effects may be magnified in deserts through the potential for beaver to alter the stream thermal regime and water budget. ?? Society of Wetland Scientists 2011.

Wetlands↗

USGS2010

Novel plant communities limit the effects of a managed flood to restore riparian forests along a large regulated river

Dam releases used to create downstream flows that mimic historic floods in timing, peak magnitude and recession rate are touted as key tools for restoring riparian vegetation on large regulated rivers. We analysed a flood on the 5th‐order Green River below Flaming Gorge Dam, Colorado, in a broad alluvial valley where Fremont cottonwood riparian forests have senesced and little recruitment has occurred since dam completion in 1962. The stable post dam flow regime triggered the development of novel riparian communities with dense herbaceous plant cover. We monitored cottonwood recruitment on landforms inundated by a managed flood equal in magnitude and timing to the average pre‐dam flood. To understand the potential for using managed floods as a riparian restoration tool, we implemented a controlled and replicated experiment to test the effects of artificially modified ground layer vegetation on cottonwood seedling establishment. Treatments to remove herbaceous vegetation and create bare ground included herbicide application (H), ploughing (P), and herbicide plus ploughing (H + P). Treatment improved seedling establishment. Initial seedling densities on treated areas were as much as 1200% higher than on neighbouring control (C) areas, but varied over three orders of magnitude among the five locations where manipulations were replicated. Only two replicates showed the expected seedling density rank of (H + P) > P > H> C. Few seedlings established in control plots and none survived 1 year. Seedling density was strongly affected by seed rain density. Herbivory affected growth and survivorship of recruits, and few survived nine growing seasons. Our results suggest that the novel plant communities are ecologically and geomorphically resistant to change. Managed flooding alone, using flows equal to the pre‐dam mean annual peak flood, is an ineffective riparian restoration tool where such ecosystem states are present and floods cannot create new habitat for seedling establishment. This problem significantly limits long‐term river and riparian management options.

Colorado↗

USGS2009

Ecosystem effects of environmental flows: Modelling and experimental floods in a dryland river

Successful environmental flow prescriptions require an accurate understanding of the linkages among flow events, geomorphic processes and biotic responses. We describe models and results from experimental flow releases associated with an environmental flow program on the Bill Williams River (BWR), Arizona, in arid to semiarid western U.S.A. Two general approaches for improving knowledge and predictions of ecological responses to environmental flows are: (1) coupling physical system models to ecological responses and (2) clarifying empirical relationships between flow and ecological responses through implementation and monitoring of experimental flow releases. We modelled the BWR physical system using: (1) a reservoir operations model to simulate reservoir releases and reservoir water levels and estimate flow through the river system under a range of scenarios, (2) one- and two-dimensional river hydraulics models to estimate stage-discharge relationships at the whole-river and local scales, respectively, and (3) a groundwater model to estimate surface- and groundwater interactions in a large, alluvial valley on the BWR where surface flow is frequently absent. An example of a coupled, hydrology-ecology model is the Ecosystems Function Model, which we used to link a one-dimensional hydraulic model with riparian tree seedling establishment requirements to produce spatially explicit predictions of seedling recruitment locations in a Geographic Information System. We also quantified the effects of small experimental floods on the differential mortality of native and exotic riparian trees, on beaver dam integrity and distribution, and on the dynamics of differentially flow-adapted benthic macroinvertebrate groups. Results of model applications and experimental flow releases are contributing to adaptive flow management on the BWR and to the development of regional environmental flow standards. General themes that emerged from our work include the importance of response thresholds, which are commonly driven by geomorphic thresholds or mediated by geomorphic processes, and the importance of spatial and temporal variation in the effects of flows on ecosystems, which can result from factors such as longitudinal complexity and ecohydrological feedbacks. ?? Published 2009.

Freshwater Biology↗

USGS2007

The influence of river regulation and land use on floodplain forest regeneration in the semi-arid upper Colorado River Basin, USA

Flow regulation effects on floodplain forests in the semi-arid western United States are moderately well understood, whereas effects associated with changes in floodplain land use are poorly documented. We mapped land cover patterns from recent aerial photos and applied a classification scheme to mainstem alluvial floodplains in 10 subjectively selected 4th order hydrologic units (subbasins) in the Upper Colorado River Basin (UCRB) in order to document land use patterns (floodplain development) and assess their effects on Fremont cottonwood forest (CF) regeneration. Three of the mainstem rivers were unregulated, five were moderately regulated and two were highly regulated. We classified polygons as Undeveloped (with two categories, including CF) and Developed (with five categories). We ground-truthed 501 randomly selected polygons (4-28% of the floodplain area in each subbasin) to verify classification accuracy and to search for cottonwood regeneration, defined as stands established since regulation began or 1950, whichever is most recent. From 40% to 95% of the floodplain area remained undeveloped, but only 19-70% of the floodplain area was classified as forest. Regeneration occupied a mean of 5% (range 1-17%) of the floodplain. The likelihood of the presence of regeneration in a polygon was reduced 65% by development and independently in a complex manner by flow regulation. Our analyses indicate that floodplain forests may be in jeopardy on both regulated and unregulated rivers and that information on historical forest extent is needed to better understand their current status in the UCRB. Conservation efforts need to be coordinated at a regional level and address the potentially adverse affects of both flow regulation and floodplain development.

River Research and Applications↗

USGS2007

Variable role of aquatic macroinvertebrates in initial breakdown of seasonal leaf litter inputs to a cold-desert river

We used coarse-mesh and fine-mesh leafpacks to examine the importance of aquatic macroinvertebrates in the breakdown of floodplain tree leaf litter that seasonally entered a sand-bedded reach of the sixth-order Yampa River in semiarid Colorado. Leafpacks were positioned off the easily mobilized channel bed, mimicking litter trapped in debris piles. Organic matter (OM) loss was fastest for leaves collected from the floodplain and placed in the river in spring (k = 0.029/day) and slowest for leaves collected and placed in the river in winter (0.006/day). Macroinvertebrates were most abundant in winter and spring leaves, but seemed important to processing only in spring, when exclusion by fine mesh reduced OM loss by 25% and nitrogen loss by 65% in spring leaves. Macroinvertebrates seemed to have little role in processing of autumn, winter, or summer leaves over the 50-day to 104-day monitoring periods. Desiccation during bouts of low discharge and sediment deposition on leaves limited invertebrate processing in summer and autumn, whereas processing of winter leaves, which supported relatively large numbers of shredders, might have been restricted by ice formation and low water temperatures. These results were consistent with the concept that microbial processing dominates in higher-order rivers, but suggested that macroinvertebrate processing can be locally important in higher-order desert rivers in seasons or years with favorable discharge and water quality conditions.

Southwestern Naturalist↗

USGS2006

Flood pattern and weather determine Populus leaf litter breakdown and nitrogen dynamics on a cold desert floodplain

Patterns and processes involved in litter breakdown on desert river floodplains are not well understood. We used leafpacks containing Fremont cottonwood ( Populus deltoides subsp. wislizenii ) leaf litter to investigate the roles of weather and microclimate, flooding (immersion), and macroinvertebrates on litter organic matter (OM) and nitrogen (N) loss on a floodplain in a cool-temperate semi-arid environment (Yampa River, northwestern Colorado, USA). Total mass of N in fresh autumn litter fell by ∼20% over winter and spring, but in most cases there was no further N loss prior to termination of the study after 653 days exposure, including up to 20 days immersion during the spring flood pulse. Final OM mass was 10–40% of initial values. The pattern of OM and N losses suggested most N would be released outside the flood season, when retention within the floodplain would be likely. The exclusion of macroinvertebrates modestly reduced the rate of OM loss (by about 10%) but had no effect on N dynamics over nine months. Immersion in floodwater accelerated OM loss, but modest variation in litter quality did not affect the breakdown rate. These results are consistent with the concept that decomposition on desert floodplains progresses much as does litter processing in desert uplands, but with periodic bouts of processing typical of aquatic environments when litter is inundated by floodwaters. The strong dependence of litter breakdown rate on weather and floods means that climate change or river flow management can easily disrupt floodplain nutrient dynamics.

Journal of Arid Environments↗

USGS2003

The effects of bird use on nutrient removal in a constructed wastewater-treatment wetland

A 9.9-ha constructed wetland designed to reduce nitrogen in municipal wastewater following conventional secondary treatment began operating in southern California's San Jacinto Valley in September 1994. The wetland incorporated zones of bulrush ( Schoenoplectus acutus and S. californicus ) for effluent treatment, plus areas of 1.8-m deep open water and other features to benefit wintering waterfowl. A one-year long program to monitor bird use and evaluate their contribution to loadings of nitrogen and phosphorus was initiated seven months later and a second, four-month long period of monitoring was initiated after a 20-month hiatus. Daily bird use peaked at nearly 12,000 individuals during the second period. Estimates of maximum daily nitrogen and phosphorus input by birds were 139 g N ha −1 day −1 and 56 g P ha −1 day −1 . Following a reconfiguration of the wetland that increased the area of open water, a third year-long period of monitoring was initiated in September 2000. Estimated maximum daily loading attributable to birds during this period reached 312 g N ha −1 day −1 and 124 g P ha −1 day −1 . These levels represent only 2.6% and 7.0%, respectively, of the mean daily loads of N and P in inflow water from the wastewater-treatment plant. Wintering waterfowl contributed the most to nutrient loading, but the numerically dominant species was the colonial Red-winged Blackbird ( Agelaius phoeniceus ). The wetland's nutrient-removal efficiency was negatively correlated to bird loading. However, the greatest bird loading occurred during November to March, when winter conditions would reduce microbial nutrient-removal processes and plant uptake in the wetland. Multiple regression analysis indicated that variation in nutrient removal efficiency over a one-year period was best explained by wetland water temperature (R 2 = 0.21) and that little additional insight was gained by adding bird loading and inflow nutrient load data (R 2 = 0.22). This case study supports the concept that a constructed wetland can be designed both to reduce nutrients in municipal wastewater and to provide habitat for wetland birds.

Wetlands↗

USGS2003

Ord's kangaroo rats living in floodplain habitats: Factors contributing to habitat attraction

High densities of an aridland granivore, Ord's kangaroo rat (Dipodomys ordii), have been documented in floodplain habitats along the Yampa River in northwestern Colorado. Despite a high probability of inundation and attendant high mortality during the spring flood period, the habitat is consistently recolonized. To understand factors that potentially make riparian habitats attractive to D. ordii, we compared density and spatial pattern of seeds, density of a competitor (western harvester ant, Pogonomyrmex occidentalis), and digging energetics within floodplain habitats and between floodplain and adjacent upland habitats. Seed density within the floodplain was greatest in the topographically high (rarely flooded) floodplain and lowest immediately after a spring flood in the topographically low (frequently flooded) floodplain. Seed densities in adjacent upland habitat that never floods were higher than the lowest floodplain habitat. In the low floodplain prior to flooding, seeds had a clumped spatial pattern, which D. ordii is adept at exploiting; after spring flooding, a more random pattern resulted. Populations of the western harvester ant were low in the floodplain relative to the upland. Digging by D. ordii was energetically less expensive in floodplain areas than in upland areas. Despite the potential for mortality due to annual spring flooding, the combination of less competition from harvester ants and lower energetic costs of digging might promote the use of floodplain habitat by D. ordii.

Southwestern Naturalist↗

USGS2002

Spatial correlations of Diceroprocta apache and its host plants: Evidence for a negative impact from Tamarix invasion

1. The hypothesis that the habitat-scale spatial distribution of the Apache cicada Diceroprocta apache Davis is unaffected by the presence of the invasive exotic saltcedar Tamarix ramosissima was tested using data from 205 1-m 2 quadrats placed within the flood-plain of the Bill Williams River, Arizona, U.S.A. Spatial dependencies within and between cicada density and habitat variables were estimated using Moran's I and its bivariate analogue to discern patterns and associations at spatial scales from 1 to 30 m. 2. Apache cicadas were spatially aggregated in high-density clusters averaging 3 m in diameter. A positive association between cicada density, estimated by exuvial density, and the per cent canopy cover of a native tree, Goodding's willow Salix gooddingii , was detected in a non-spatial correlation analysis. No non-spatial association between cicada density and saltcedar canopy cover was detected. 3. Tests for spatial cross-correlation using the bivariate I YZ indicated the presence of a broad-scale negative association between cicada density and saltcedar canopy cover. This result suggests that large continuous stands of saltcedar are associated with reduced cicada density. In contrast, positive associations detected at spatial scales larger than individual quadrats suggested a spill-over of high cicada density from areas featuring Goodding's willow canopy into surrounding saltcedar monoculture. 4. Taken together and considered in light of the Apache cicada's polyphagous habits, the observed spatial patterns suggest that broad-scale factors such as canopy heterogeneity affect cicada habitat use more than host plant selection. This has implications for management of lower Colorado River riparian woodlands to promote cicada presence and density through maintenance or creation of stands of native trees as well as manipulation of the characteristically dense and homogeneous saltcedar canopies.

Ecological Entomology↗

USGS2002

Effects of cottonwood leaf beetle Chrysomela scripta (Coleoptera: Chrysomelidae) on survival and growth of Fremont cottonwood ( Populus fremontii ) in northwest Colorado

Greenhouse and field studies were used to assess the effects of a cottonwood leaf beetle ( Chrysomela scripta ) outbreak on growth and survivorship of Fremont cottonwood ( Populus fremontii ) along a segment of the Yampa River in northwestern Colorado. Exposure of greenhouse-reared seedlings to either 1 or 3 larvae reduced survivorship and the shoot and root masses of surviving seedlings. In the field sapling survivorship in unmanipulated, naturally established patches of saplings was inversely related to the intensity of beetle damage noted the previous year in both 1998–1999 and 1999–2000. Floodplain saplings treated with the insecticide esfenvalerate during two growing seasons added more height and radial growth than untreated saplings. Field observations in riparian stands along the Yampa River indicated that beetles preferentially oviposited and fed on cottonwood seedlings over saplings and mature trees during late summer. Taken together, the greenhouse and field studies suggest herbivory by C. scripta is a major determinant of Fremont cottonwood distribution and abundance at the Yampa River site. Repeated surveys detected few or no beetles in stands along the neighboring but regulated Green River. We hypothesize that flow regulation, by reducing P. fremontii seedling abundance, precludes C. scripta from reaching outbreak status along the Green River.

Colorado↗

USGS2002

Observations of the larval stages of Diceroprocta apache Davis (Homoptera: Tibicinidae)

Diceroprocta apache Davis is a locally abundant cicada in the riparian woodlands of the southwestern United States. While its ecological importance has often been hypothesized, very little is known of its specific life history. This paper presents preliminary information on life history of D. apache from larvae collected in the field at seasonal intervals as well as a smaller number of reared specimens. Morphological development of the fore-femoral comb closely parallels growth through distinct size classes. The data indicate the presence of five larval instars in D. apache . Development times from greenhouse-reared specimens suggest a 3-4 year life span and overlapping broods were present in the field. Sex ratios among pre-emergent larvae suggest the asynchronous emergence of sexes.

Journal of the Kansas Entomological Society↗

USGS2000

Movement patterns of riparian small mammals during predictable floodplain inundation

We monitored movements of small mammals resident on floodplains susceptible to spring floods to assess whether and how these animals respond to habitat inundation. The 2 floodplains were associated with 6th order river segments in a semiarid landscape; each was predictably inundated each year as snowmelt progressed in headwater areas of the Rocky Mountains. Data from live trapping, radiotelemetry, and microtopographic surveys indicated that Peromyscus maniculatus, Microtus montanus, and Dipodomys ordii showed different responses to inundation, but all reflected a common tendency to remain in the original home range until “forced” to leave. The reluctance of Dipodomys ordii to abandon the home burrow often resulted in death in situ, whereas individual P. maniculatus and M. montanus moved to nearby higher ground but not necessarily toward upland. This behavior could lead to occupancy of an island that disappeared as floodwaters rose. Peromyscus maniculatus climbed into sapling cottonwood, but the quality of such arboreal refuges was unclear. We found only weak support for the hypothesis that displacement was temporary; most floodplain residents, including P. maniculatus, disappeared over the flood period. No secondary effect from flooding on adjacent upland small-mammal assemblages was detected. Our data suggest populations of facultatively riparian, nonarboreal small mammals such as M. montanus and D. ordii generally experience habitat inundation as a catastrophy. Terrestrial species capable of using an arboreal refuge, such as P. maniculatus, face a more variable risk, determined in part by timing and duration of the flood event. River regulation can affect both sets of risks.

Journal of Mammalogy↗

USGS2000

Investigation of denitrification rates in an ammonia-dominated constructed wastewater treatment wetland

Denitrification measurements were made under simulated field conditions using sediment cores and water collected from the Hemet/San Jacinto Multipurpose Demonstration Wetland (Riverside County, California, USA). The 9.9 ha constructed wetland is used to both polish ammonia-dominated secondary municipal effluent and provide migratory bird habitat. The wetland was originally constructed as a marsh-pond-marsh system in 1994. Over the period from January through March 1998, measured denitrification rates averaged 20.9 ± 20.9 μmol N m −2 h −1 within the emergent marsh portions of the wetland and 646 ± 353 μmol N m −2 h −1 in open water areas. The mean areal denitrification removal rate for this period was 0.70 kg N ha −1 d −1 , which accounted for about 8% of the total N removed by the wetland. Internal retention was the main N-removal mechanism. Synoptic water quality surveys indicated that denitrification was limited by a lack of nitrification within the wetland. Between April 1998 and January 1999, the wetland was reconfigured as a hemi-marsh system, having equal areas of interspersed emergent marsh and deep open water. In May 1999, measured denitrification rates averaged 1414 ± 298 μmol N m −2 h −1 within the emergent marsh zones and 682 ± 218 μmol N m −2 h −1 in the open water areas. The mean areal denitrification removal rate was 3.58 kg N ha −1 d −1 , which accounted for 40% of the total N removed by the wetland. A synoptic water quality survey indicated that nitrification within the wetland had been enhanced by the reduction of emergent macrophyte biomass and the increase in the area of interspersed deep open water. The modifications to the wetland shifted the nitrogen balance from a large internal storage component and a small denitrification component in 1998 to a more denitrifying system in 1999.

Wetlands↗

USGS2000

Plant-herbivore-hydroperiod interactions: effects of native mammals on floodplain tree recruitment

Floodplain plant–herbivore–hydroperiod interactions have received little attention despite their potential as determinants of floodplain structure and functioning. We used five types of exclosures to differentially exclude small-, medium-, and large-sized mammals from accessing Fremont cottonwood ( Populus deltoides Marshall subsp. wizlizenii (Watson) Eckenwalder) seedlings and saplings growing naturally on four landform types at an alluvial reach on each of two rivers, the Green and Yampa, in Colorado and Utah. The two study reaches differed primarily as a result of flow regulation on the Green River, which began in 1962. Landforms were a rarely flooded portion of the alluvial plain, geomorphically active slow- and fast-water channel margin sites on the Yampa reach, and an aggrading side channel on the Green. Small-mammal live-trapping and observational data indicated that, with minor exceptions, the kinds of mammals eating cottonwood within each reach were identical. We monitored condition and fates of individual cottonwood plants from October 1993 through the 1997 growing season. Differences in survival and growth were noted both within and between reaches, and both due to, and independent of, mammalian herbivory. Comparisons of cottonwood growth and survivorship among exclosures and between exclosures and controls indicated that a small mammal, Microtus montanus, reduced seedling and sapling survivorship at the Green River reach, but to a lesser extent (seedlings) or not at all (saplings) on the Yampa reach. In contrast, reductions in sapling height increment attributable to medium- and large-sized herbivores were detected only at the Yampa site. We suggest that these differences are a result of (1) flow regulation allowing Microtus populations to escape the mortality normally accompanying the large, snowmelt-driven spring flood, as well as regulation promoting a herbaceous understory favorable to voles, and (2) greater browsing pressure from overwintering deer and elk at the Yampa reach, unrelated to flow regulation. Within areas used by foraging beaver, the probability of a sapling being cut by beaver was similar on the two reaches. This study suggests that changes in riparian plant–herbivore relationships due to shifts in river hydrology may be a common and important consequence of river regulation.

Ecological Applications↗

USGS1999

Butterfly (Papilionoidea and Hesperioidea) assemblages associated with natural, exotic, and restored riparian habitats along the lower Colorado River, USA

Butterfly assemblages were used to compare revegetated and natural riparian areas along the lower Colorado River. Species richness and correspondence analyses of assemblages showed that revegetated sites had fewer biological elements than more natural sites along the Bill Williams River. Data suggest that revegetated sites do not provide resources needed by some members of the butterfly assemblage, especially those species historically associated with the cottonwood/willow ecosystem. Revegetated sites generally lacked nectar resources, larval host plants, and closed canopies. The riparian system along the regulated river segment that contains these small revegetated sites also appears to have diminished habitat heterogeneity and uncoupled riparian corridors. Revegetated sites were static environments without the successional stages caused by flooding disturbance found in more natural systems. We hypothesize that revegetation coupled with a more natural hydrology is important for restoration of butterfly assemblages along the lower Colorado River.

Bill Williams River, Colorado River↗