Geology topics

Emily C. Palmquist

Publications and source records attributed to Emily C. Palmquist.

29 records · Page 2Linked to original sources

USGS2020

Assessment of rangeland ecosystem conditions in Grand Canyon-Parashant National Monument, Arizona

Sustainability of dryland ecosystems depends on the functionality of soil-vegetation feedbacks that affect ecosystem processes, such as nutrient cycling, water capture and retention, soil erosion and deposition, and plant establishment and reproduction. Useful, common indicators can provide information on soil and site stability, hydrologic function, and biotic integrity. Evaluation of rangeland health thus relies on describing the condition and sustainability of these individual, measurable, and observable indicators that are linked to important ecosystem processes. This report focuses on the ~200,000 acres of the Grand Canyon-Parashant National Monument that is administered by the National Park Service (NPS)—one of the largest NPS units where livestock grazing is a permitted land-use activity. Many ecosystems in the monument are characterized by a low degree of resilience to improper grazing because of low and variable precipitation. The monument is marked by a high degree of environmental heterogeneity, including a large elevation gradient, widely differing precipitation patterns, a diversity of geologic substrates, and unique combinations of plant species. The objective of this report is to (1) increase our understanding of the underlying landscape, soil, and climate setting factors that affect Grand Canyon-Parashant National Monument dryland ecosystem structure and function (also referred to as land potential) and (2) characterize the condition of monument ecosystems in relation to management concepts, such as rangeland health. Data were analyzed by elevation zone using both univariate and multivariate approaches. Survey results document the high level of diversity within the study area, including 15 unique soil taxa and 271 species of plants. We collected three new plant species for Grand Canyon-Parashant National Monument and 17 new species for the NPS portion of the monument. Results also document a strong association between rangeland health indicators and elevation, topographic setting, and soils. Soil factors found to explain important variation across plots include the amount of exposed bedrock, soil rockiness, soil texture (and associated hydrologic properties), and soil depth. We also found that dominant species turnover across elevation may represent species’ differences in adaptation to climates, including Larrea tridentata , Coleogyne ramosissima , and Artemisia spp. Bromus rubens is the most common invasive species of concern recorded in this study, but other common invasive species are Bromus tectorum , Erodium cicutarium , and Schismus arabicus . Correlations between an index of cattle use and indicators of rangeland health suggest that areas with high cattle use have increased bare ground, decreased ground cover, increased frequency of Schismus arabicus , decreased cover of Coleogyne ramosissima and Ephedra spp., and increased cover of Gutierrezia spp. The few strong correlations observed between indicators of vascular plant community cover or abundance and indicators of cattle activity support rangeland assessment and monitoring strategies that do not rely solely on plant-based indicators are needed. This work supports management of dryland ecosystems, including Grand Canyon-Parashant National Monument, using concepts of land potential. We conclude the report with recommendations on improving existing land-potential-based classification systems, associated interpretations, and methods for moving forward with a Grand Canyon-Parashant National Monument rangeland monitoring program.

Arizona↗

USGS2020

Associations between riparian plant morphological guilds and fluvial sediment dynamics along the regulated Colorado River in Grand Canyon

Effects of riparian vegetation on fluvial sediment dynamics depend on morphological traits of the constituent species. Determining the effects of different morphological guilds on sedimentation rates, as influenced by multiple aspects of dam operations, can help identify viable strategies for streamflow and vegetation management to achieve riparian resource goals. Plants of increasing size and branching density or complexity have been found to have greater effects on sedimentation in free‐flowing systems; however, this relationship could differ in regulated rivers. We tested the hypothesis that plant guilds of increasing height and branching complexity would be positively associated with sedimentation rates on 23 sandbars deposited in zones of recirculating flow (eddies) along the Colorado River in Grand Canyon. We used an image‐based vegetation classification and digital elevation models from annual topographic surveys to track associations between six plant morphological guilds and topographic change over 5 years. Vegetation had significant associations with deposition after accounting for geomorphic setting, but the ordinal guild scale was not positively correlated with deposition magnitude. Instead, low‐statured rhizomatous and herbaceous guilds were particularly effective at capturing sediment in the separation zone of sandbars, whereas tall herbs and large shrubs were most effective at capturing sediment in reattachment zones. These nuanced interactions between geomorphic position and morphological guild may be a direct consequence of flow regulation through modifications to physical deposition and erosion processes. Flow regulation may also select for a narrow subset of morphological guilds, reducing the diversity of vegetation feedbacks on sedimentation and emphasizing geomorphic drivers.

Arizona↗

USGS2019

A comparison of riparian vegetation sampling methods along a large, regulated river

Monitoring riparian vegetation cover and species richness is an important component of assessing change and understanding ecosystem processes. Vegetation sampling methods determined to be the best option in other ecosystems (e.g., desert grasslands and arctic tundra) may not be the best option in multilayered, species rich, heterogeneous riparian vegetation. This study examines the strengths and weaknesses of two common vegetation sampling methods, line‐point intercept and ocular quadrat estimates. Permutational analysis of variance analyses indicate that cover estimates among observers did not differ significantly for either line‐point intercept or ocular quadrat estimates. Line‐point intercept cover estimates resulted in lower coefficient of variation among observers than ocular quadrat estimates, but the ocular quadrat estimates recorded significantly more species. Line‐point estimates of cover were generally larger than ocular quadrat estimates. Ocular quadrat estimates are appropriate when assessment of richness is important, in areas with heterogeneous geomorphology and hydrology where fine‐scale measurements are most useful, and in areas where continuous sampling transects are impracticable. Line‐point intercept estimates are useful when minimum variation among observers is necessary, continuous transects are logical and practicable for the sampling area, woody cover does not present a logistical complication, and species richness is not a priority.

River Research and Applications↗

USGS2019

Effects of high flow experiments on riparian vegetation resources in Grand Canyon

Flood events have historically had a strong impact on riparian vegetation within Grand Canyon. Pre-dam sandbars were nearly devoid of perennial riparian vegetation due to the magnitude and frequency of periodic floods (Turner and Karpiscak, 1980). Vegetation has increased since dam closure (Waring, 1995), particularly since the early 1990s (Sankey and others, 2015). This increase in vegetation is attributable to multiple aspects of dam operations, including the low magnitude and duration of High-Flow Experiments (HFEs), specifically flows at 45,000 cfs or smaller over 96 hours. Thus, we begin by providing a broader context for understanding vegetation change, and how other factors interact with HFEs to determine their influence on riparian vegetation. We then discuss the potential mechanisms by which HFEs may impact vegetation, the empirical evidence for those impacts and associated confidence in that evidence, and future research approaches to better fill these gaps in our understanding.

Arizona↗

USGS2018

Hydrological regime and climate interactively shape riparian vegetation composition along the Colorado River, Grand Canyon

Question How closely do riparian plant communities track hydrological and climatic variation in space, and how do interactions among hydrological and climatic filters influence success of flow management strategies? Location Grand Canyon, Arizona, USA. Methods Multi‐year vegetation surveys were conducted across three hydrological zones – active channel, active floodplain and inactive floodplain – within each of 42 sandbars that vary geographically in temperature and precipitation along a 400‐km river segment. Ecological niche models were used to estimate locally optimal conditions of maximum inundation duration, elevation above daily peak flow, mean annual precipitation, and mean maximum and minimum temperature for 16 of the most abundant woody and 58 most abundant herbaceous plant species. These estimates were used to calculate community‐weighted mean (CWM) environmental preferences, which were used to determine how closely vegetation preferences tracked local variation in environmental factors, and to assess interactive responses of species and communities to variation in hydrology and climate. Results Communities closely tracked hydrological variation across zones, but less so within zones. Communities tracked variation in minimum temperature more closely than maximum temperature or precipitation. At the species level, woody plants that were more abundant in wetter hydrological conditions were also more abundant in wetter climatic conditions, and vice versa. This relationship was even stronger at the community level, where there were significant negative relationships between CWM preferences of inundation duration and temperature for both woody and herbaceous vegetation. Conclusions The climate‐hydrology linkages found in this system suggest that increasing temperatures and drought are likely to reduce the inundation tolerance of riparian vegetation within the Grand Canyon. Increasing the duration of high flow events would likely reduce the abundance of encroaching woody vegetation, but could also reduce the resilience of remaining vegetation to heat waves and drought. The reinforcing effects of climatic and hydrological filters are likely to generally result in greater sensitivity of species composition to environmental change than if those environmental filters acted independently. These results have implications for predicting resource responses to environmental change, as well as prescriptions for direct vegetation management to enhance resilience.

Colorado River, Grand Canyon↗

USGS2018

Monitoring riparian-vegetation composition and cover along the Colorado River downstream of Glen Canyon Dam, Arizona

Vegetation in the riparian zone (the area immediately adjacent to streams, such as stream banks) along the Colorado River downstream of Glen Canyon Dam, Arizona, supports many ecosystem and societal functions. In both Glen Canyon and Grand Canyon, this ecosystem has changed over time in response to flow alterations, invasive species, and recreational use. Riparian-vegetation cover and composition are likely to continue to change as these pressures persist and new ones emerge. Because this system is a valuable resource that is known to change in response to flow regime and other disturbances, a long-term monitoring protocol has been designed with three primary objectives: Annually measure and summarize the status (composition and cover) of native and non-native vascular-plant species within the riparian zone of the Colorado River between Glen Canyon Dam and Lake Mead. At 5-year intervals, assess change in vegetation composition and cover in the riparian zone, as related to geomorphic setting and dam operations, particularly flow regime. Collect data in a manner that can be used by multiple stakeholders, particularly the basinwide monitoring program overseen by the National Park Service’s Northern Colorado Plateau Network Inventory and Monitoring program. A protocol for the long-term monitoring of riparian vegetation is described in detail and standard operating procedures are included herein for all tasks. Visual estimates of foliar and ground covers are collected in conjunction with environmental measurements to assess correlations of foliar cover with abiotic and flow variables. Sample quadrats are stratified by frequency of inundation, geomorphic feature, and by river segment to account for differences in vegetation type. Photographs of sites are also taken to illustrate qualitative characteristics of the site at the time of sampling. Procedures for field preparation, generating random samples, data collection, data management, collecting and managing unknown species collections, and reporting are also described. Although this protocol is intended to be consistent over the long-term, procedures for minor and major revisions to the protocol are also outlined.

Arizona↗

USGS2018

Landscape-scale processes influence riparian plant composition along a regulated river

Hierarchical frameworks are useful constructs when exploring landscape- and local-scale factors affecting patterns of vegetation in riparian areas. In drylands, which have steep environmental gradients and high habitat heterogeneity, landscape-scale variables, such as climate, can change rapidly along a river's course, affecting the relative influence of environmental variables at different scales. To assess how landscape-scale factors change the structure of riparian vegetation, we measured riparian vegetation composition along the Colorado River through Grand Canyon, determined which factors best explain observed changes, identified how richness and functional diversity vary, and described the implications of our results for river management. Cluster analysis identified three divergent floristic groups that are distributed longitudinally along the river. These groups were distributed along gradients of elevation, temperature and seasonal precipitation, but were not associated with annual precipitation or local-scale factors. Species richness and functional diversity decreased as a function of distance downstream showing that changing landscape-scale factors result in changes to ecosystem characteristics. Species composition and distribution remain closely linked to seasonal precipitation and temperature. These patterns in floristic composition in a semiarid system inform management and provide insights into potential future changes as a result of shifts in climate and changes in flow management.

Arizona↗

USGS2017

Variation in species-level plant functional traits over wetland indicator status categories

Wetland indicator status (WIS) describes the habitat affinity of plant species and is used in wetland delineations and resource inventories. Understanding how species-level functional traits vary across WIS categories may improve designations, elucidate mechanisms of adaptation, and explain habitat optima and niche. We investigated differences in species-level traits of riparian flora across WIS categories, extending their application to indicate hydrologic habitat. We measured or compiled data on specific leaf area (SLA), stem specific gravity (SSG), seed mass, and mature height of 110 plant species that occur along the Colorado River in Grand Canyon, Arizona. Additionally, we measured leaf δ 13 C, δ 15 N, % carbon, % nitrogen, and C/N ratio of 56 species with C3 photosynthesis. We asked the following: (i) How do species-level traits vary over WIS categories? (ii) Does the pattern differ between herbaceous and woody species? (iii) How well do multivariate traits define WIS categories? (iv) Which traits are correlated? The largest trait differences among WIS categories for herbaceous species occurred for SSG, seed mass, % leaf carbon and height, and for woody species occurred for height, SSG, and δ 13 C. SSG increased and height decreased with habitat aridity for both woody and herbaceous species. The δ 13 C and hence water use efficiency of woody species increased with habitat aridity. Water use efficiency of herbaceous species increased with habitat aridity via greater occurrence of C4 grasses. Multivariate trait assemblages differed among WIS categories. Over all species, SLA was correlated with height, δ 13 C, % leaf N, and C/N; height was correlated with SSG and % leaf C; SSG was correlated with % leaf C. Adaptations of both herbaceous and woody riparian species to wet, frequently inundated habitats include low-density stem tissue. Adaptations to drier habitats in the riparian zone include short, high-density cavitation-resistant stem tissue, and high water use efficiency. The results enhance understanding about using traits to describe plant habitat in riparian systems.

Arizona↗

USGS2017

Changes in community-level riparian plant traits over inundation gradients, Colorado River, Grand Canyon

Comparisons of community-level functional traits across environmental gradients have potential for identifying links among plant characteristics, adaptations to stress and disturbance, and community assembly. We investigated community-level variation in specific leaf area (SLA), plant mature height, seed mass, stem specific gravity (SSG), relative cover of C4 species, and total plant cover over hydrologic zones and gradients in years 2013 and 2014 in the riparian plant community along the Colorado River in the Grand Canyon. Vegetation cover was lowest in the frequently inundated active channel zone, indicating constraints on plant establishment and production by flood disturbance and anaerobic stress. Changes in trait values over hydrologic zones and inundation gradients indicate that frequently inundated plots exhibit a community-level ruderal strategy with adaptation to submergence (high SLA and low SSG, height, seed mass, C4 relative cover), whereas less frequently inundated plots exhibit adaptation to drought and infrequent flood disturbance (low SLA and high SSG, height, seed mass, C4 relative cover). Variation in traits not associated with inundation suggests niche differentiation and multiple modes of community assembly. The results enhance understanding of future responses of riparian communities of the Grand Canyon to anticipated drying and changes in hydrologic regime.

Arizona↗

USGS2017

Functional traits and ecological affinities of riparian plants along the Colorado River in Grand Canyon

Trait-based approaches to vegetation analyses are becoming more prevalent in studies of riparian vegetation dynamics, including responses to flow regulation, groundwater pumping, and climate change. These analyses require species trait data compiled from the literature and floras or original field measurements. Gathering such data makes trait-based research time intensive at best and impracticable in some cases. To support trait-based analysis of vegetation along the Colorado River through Grand Canyon, a data set of 20 biological traits and ecological affinities for 179 species occurring in that study area was compiled. This diverse flora shares species with many riparian areas in the western USA and includes species that occur across a wide moisture gradient. Data were compiled from published scientific papers, unpublished reports, plant fact sheets, existing trait databases, regional floras, and plant guides. Data for ordinal environmental tolerances were more readily available than were quantitative traits. More publicly available data are needed for traits of both common and rare southwestern U.S. plant species to facilitate comprehensive, trait-based research. The trait data set is free to use and can be downloaded from ScienceBase: https://www.sciencebase.gov/catalog/item/58af41dee4b01ccd54f9f2ff and https://dx.doi.org/10.5066/F7QV3JN1

Arizona↗

USGS2015

Evaluating rehabilitation efforts following the Milford Flat Fire: successes, failures, and controlling factors

Uncontrolled wildfire in arid and semiarid ecosystems has become an increasing concern in recent decades. Active rehabilitation of fire-affected areas is often quickly initiated to minimize long-term ecosystem damage. However, the complex soil-geomorphic-vegetation patterns and low and variable moisture conditions in these regions makes restoration challenging. To further inform these post-fire management decisions, we present results from 5 years of vegetation and sediment flux monitoring following the Milford Flat Fire in west-central Utah, USA. Our sampling design includes monitoring plots in areas not burned, areas burned but where no rehabilitation was attempted, and burned areas where various rehabilitation approaches were implemented. At each of the 25 plots, vegetation cover and composition data were collected annually, and wind-driven sediment flux was measured using passive dust traps. To evaluate effectiveness of post-fire rehabilitation treatments in establishing desired species and limiting dominance of undesired species, we analyzed the temporal response of individual species and functional groups as well as community-level multivariate responses. The warm and dry conditions that persisted for approximately 12 months post-treatment, coupled with the surface disturbing rehabilitation approaches used, resulted in near-surface dust fluxes several orders of magnitude higher in treated areas than in unburned or burned areas where no rehabilitation occurred. These dry conditions and high surface sediment flux limited the establishment of seeded species in rehabilitation areas for nearly 3 years. Post-fire rehabilitation did not limit dominance by invasive annual species of concern. Perennial species composition in the areas burned but not subject to post-fire rehabilitation was relatively similar to unburned throughout the study period. In contrast, the burned plots where rehabilitation was attempted were characterized by no (<3%) perennial cover or, in response to moister conditions, seeded forage species. These results suggest the post-fire rehabilitation efforts conducted in the lower elevation regions affected by the Milford Flat Fire were not generally successful. Though dry conditions are likely to blame for the lack of success, the low and variable precipitation characteristic of these regions suggest future post-fire rehabilitation decisions must assume that precipitation is going to be insufficient and plan rehabilitation efforts that are resilient to dry conditions.

Utah↗