Collection of published works by members of the Southwest Chapter of the Ecological Society of America

Description

This collection was established to engage Southwest Chapter members and facilitate interaction between them and to enhance discovery of relevant ecological research.

latest article added on December 2013

ArticleFirst AuthorPublished
Rangeland Health Attributes and Indicators for Qualitative AssessmentPyke, David A.2002

Rangeland Health Attributes and Indicators for Qualitative Assessment

Keywords

alexander, b, bestelmeyer, biological integri-, authors wish to, w, usgs and ars jointly, ty, thank drs, soil stability, nrcs, m, l, krueger, karl, j, inventory, infiltration, hydrologic function, funded this project, erosion, eddleman, ecosystem status, c, blm

Abstract

Panels of experts from the Society for Range Management and the National Research Council proposed that status of rangeland ecosystems could be ascertained by evaluating an ecological site’s potential to conserve soil resources and by a series of indicators for ecosystem processes and site stability. Using these recommendations as a starting point, we developed a rapid, qualitative method for assessing a moment-in-time status of rangelands. Evaluators rate 17 indicators to assess 3 ecosystem attributes (soil and site stability, hydrologic function, and biotic integrity) for a given location. Indicators include rills, water flow patterns, pedestals and terracettes, bare ground, gullies, wind scour and depositional areas, litter movement, soil resistance to erosion, soil surface loss or degradation, plant composition relative to infiltration, soil compaction, plant functional/structural groups, plant mortality, litter amount, annual production, invasive plants, and reproductive capability. In this paper, we detail the development and evolution of the technique and introduce a modified ecological reference worksheet that documents the expected presence and amount of each indicator on the ecological site. In addition, we review the intended applications for this technique and clarify the differences between assessment and monitoring that lead us to recommend this technique be used for moment-in-time assessments and not be used for temporal monitoring of rangeland status. Lastly, we propose a mechanism for adapting and modifying this technique to reflect improvements in understanding of ecosystem processes. We support the need for quantitative measures for monitoring rangeland health and propose some measures that we believe may address some of the 17 indicators.

Authors

Pyke, David A., Herrick, Jeffrey E., Shaver, Patrick and Pellant, Mike

Year Published

2002

Publication

Journal of Range Management

Locations
    DOI

    10.2307/4004002

    Soil Heterogeneity Effects on Tallgrass Prairie Community Heterogeneity: An Application of Ecological Theory to Restoration Ecology.Baer, Sara G.2005

    Soil Heterogeneity Effects on Tallgrass Prairie Community Heterogeneity: An Application of Ecological Theory to Restoration Ecology.

    Keywords

    grassland;Panicum virgatum;restoration;soil heterogeneity;Switchgrass;tallgrass prairie

    Abstract

    Spatial heterogeneity of resources can influence plant community composition and diversity in natural communities. We manipulated soil depth (two levels) and nutrient availability (three levels) to create four heterogeneity treatments (no heterogeneity, depth heterogeneity, nutrient heterogeneity, and depth + nutrient heterogeneity) replicated in an agricultural field seeded to native prairie species. Our objective was to determine whether resource heterogeneity influences species diversity and the trajectory of community development during grassland restoration. The treatments significantly increased heterogeneity of available inorganic nitrogen (N), soil water content, and light penetration. Plant diversity was indirectly related to resource heterogeneity through positive relationships with variability in productivity and cover established by the belowground manipulations. Diversity was inversely correlated with the average cover of the dominant grass, Switchgrass (Panicum virgatum), which increased over time in all heterogeneity treatments and resulted in community convergence among the heterogeneity treatments over time. The success of this cultivar across the wide range of resource availability was attributed to net photosynthesis rates equivalent to or higher than those of the native prairie plants in the presence of lower foliar N content. Our results suggest that resource heterogeneity alone may not increase diversity in restorations where a dominant species can successfully establish across the range of resource availability. This is consistent with theory regarding the role of ecological filters on community assembly in that the establishment of one species best adapted for the physical and biological conditions can play an inordinately important role in determining community structure.

    Authors

    Baer, Sara G., Scott L Collins, John M. Blair, Alan K. Knapp and Anna K. Fiedler.

    Year Published

    2005

    Publication

    Restoration Ecology

    Locations
    DOI

    10.1111/j.1526-100X.2005.00051.x

    TEMPORAL AND SPATIAL VARIATION IN POLLINATION OF A MONTANE HERB: A SEVEN-YEAR STUDY.Price, Mary V.2005

    TEMPORAL AND SPATIAL VARIATION IN POLLINATION OF A MONTANE HERB: A SEVEN-YEAR STUDY.

    Keywords

    field study;floral larcenists;floral visitation rates;flower-visitor community;hummingbirds;insects;Ipomopsis aggregata;long-term study;path analysis;plant population dynamics;pollen delivery;pollination services;structural equation modeling

    Abstract

    Pollination by animals is critical to sexual reproduction of most angiosperms. However, little is known about variation in pollination service to single plant species. We report results of a long-term study of Ipomopsis aggregata, a semelparous montane herb whose flowers are visited by hummingbird and insect pollinators as well as “floral larcenists.” We censused flower visitors over seven summers at permanent study sites separated by several hundred meters, and counted pollen delivered to flowers on a subset of plants observed for visitation. The species composition of the community of visitors varied significantly across years and within the flowering season; sites varied significantly only in the magnitude of parallel annual changes in the visitor community. Rates of flower visitation fluctuated over an order of magnitude or more. Variation in mean stigma pollen load among plants flowering in the same site and year was explained by a causal path model in which visitation rates by pollinators and larcenists had linear positive and negative effects, respectively. A simplified model including only pollinators explained almost as much variance as did the full model. However, qualitatively different parameter estimates were produced by an analogous causal model based on population means across site–year combinations. Discrepant results from within- and between-population levels of analysis suggest that pollen receipt is influenced by environmental factors that vary among sites and years, as well as by pollinator visit rates. We present a heuristic causal model that includes such factors, and we note its implications for ecological and evolutionary studies of pollination.

    Authors

    Price, Mary V., Nickolas M. Waser, Rebecca E. Irwin, Diane R. Campbell, and Alison K. Brody.

    Year Published

    2005

    Publication

    Ecology

    Locations
    DOI

    10.1890/04-1274

    This article contributed by:

    Ecological Society of America

    Population and clonal level responses of a perennial grass following fire in the northern Chihuahuan DesertDrewa, Paul B.2006

    Population and clonal level responses of a perennial grass following fire in the northern Chihuahuan Desert

    Keywords

    Bouteloua eriopoda; fire intensity; grazing; precipitation; resprouting

    Abstract

    Relationships involving fire and perennial grasses are controversial in Chihuahuan Desert grasslands of southern New Mexico, USA. Research suggests that fire delays the resprouting of perennial grasses well after two growing seasons. However, such results are confounded by livestock grazing, soil erosion, and drought. Additionally, post-fire grass responses may depend on initial clone size. We evaluated the effects of fire, grazing, and clone size on Bouteloua eriopoda (black grama) in southern New Mexico grasslands. Four 2-ha plots were established in each of four sites. Fire and grazing were applied or not applied in 1999 such that four treatment combinations were assigned randomly to plots within each site. Within each plot, small (0-10 cm(2) basal area), medium (10-30 cm(2)), and large (> 30 cm(2)) clones were initially mapped in five 0.91-m(2) quadrats where grass attributes and litter cover were evaluated before and at the end of two growing seasons following fire. Maximum fire temperature was also measured. At a population level, canopy and litter cover were each approximately 50% less in burned than unburned areas. However, compared to initial levels, canopy height had increased by 10% at the end of the study, regardless of fire. At a clonal level, basal cover reductions were attributed mostly to large clones that survived fire. Smaller clone densities had decreased by as much as 19% in burned compared to unburned areas, and fire reduced the basal cover of medium clones. Basal and canopy cover, recruitment, and clone basal area decreased with increased fire temperatures. Almost all responses were independent of grazing, and interactive effects of grazing and fire were not detected. Fire did not kill all perennial grass clones, regardless of size. However, rapid responses were likely influenced by above-average precipitation after fire. Future studies in desert grasslands should examine how perennial grass dynamics are affected by fire, precipitation patterns, and interactions with grazing.

    Authors

    Drewa, Paul B.; Peters, Debra P. C.; Havstad, Kris M.

    Year Published

    2006

    Publication

    Oecologia

    Locations
    DOI

    10.1007/s00442-006-0502-4

    Multi-scale factors and long-term responses of Chihuahuan Desert grasses to droughtYao, Jin2006

    Multi-scale factors and long-term responses of Chihuahuan Desert grasses to drought

    Keywords

    arid grasslands; desertification; drought; grazing; perennial grasses; transport processes

    Abstract

    Factors with variation at broad (e.g., climate) and fine scales (e.g., soil texture) that influence local processes at the plant scale (e.g., competition) have often been used to infer controls on spatial patterns and temporal trends in vegetation. However, these factors can be insufficient to explain spatial and temporal variation in grass cover for and and semiarid grasslands during an extreme drought that promotes woody plant encroachment. Transport of materials among patches may also be important to this variation. We used long-term cover data (19152001) combined with recently collected field data and spatial databases from a site in the northern Chihuahuan Desert to assess temporal trends in cover and the relative importance of factors at three scales (plant. patch, landscape unit) in explaining spatial variation in grass cover. We examined cover of five important grass species from two topographic positions before, during, and after the extreme drought of the 1950s. Our results show that dynamics before, during, and after the drought varied by species rather than by topographic position. Different factors were related to cover of each species in each time period. Factors at the landscape unit scale (rainfall, stocking rate) were related to grass cover in the pre- and post-drought periods whereas only the plant-scale factor of soil texture was significantly related to cover of two upland species during the drought. Patch-scale factors associated with the redistribution of water (microtopography) were important for different species in the pre- and post-drought period. Another patch-scale factor, distance from historic shrub populations, was important to the persistence of the dominant grass in uplands (Bouteloua eriopoda) through time. Our results suggest the importance of local processes during the drought, and transport processes before and after the drought with different relationships for different species. Disentangling the relative importance of factors at different spatial scales to spatial patterns and long-term trends in grass cover can provide new insights into the key processes driving these historic patterns, and can be used to improve forecasts of vegetation change in and and semiarid areas.

    Authors

    Yao, Jin; Peters, Debra P. C.; Havstad, Kris M.; Gibbens, Robert P.; Herrick, Jeffrey E.

    Year Published

    2006

    Publication

    Landscape Ecology

    Locations
    DOI

    10.1007/s10980-006-0025-8

    Woody plant invasion at a semi-arid/arid transition zone: importance of ecosystem type to colonization and patch expansionPeters, Debra P. C.2006

    Woody plant invasion at a semi-arid/arid transition zone: importance of ecosystem type to colonization and patch expansion

    Keywords

    biome transition; Chilmalman Desert; ecotone; invasive species; patch dynamics; patch structure; shortgrass steppe

    Abstract

    Question: How do patterns in colonization and patch expansion of an invasive woody plant (Larrea tridentata, Zygophyllaceae) differ between two grassland ecosystems at a biome transition zone? Location: Semi-arid/arid transition zone in central New Mexico. Methods: Frequency of occurrence, height, and surface area of saplings (n = 134) and patches of adult plants (n = 247) of the invasive shrub, L. tridentata, were measured within a mosaic of ecosystems dominated either by the Chihuahuan Desert species, Bouteloua eriopoda (Poaceae),or the shortgrass steppe species, B. gracilis, located within I km of the L. tridentata-dominated ecosystem. Distances between L. tridentata patches and patch area were used to estimate connectivity as a measure of propagule pressure. Sapling age (estimated from height using previously established relationships) and distance to the L. tridentata-dominated ecosystem was used to evaluate patterns in dispersal. Cover by species or functional group inside each L. tridentata patch was compared with surrounding vegetation to estimate changes in species composition with patch expansion. Results: L. tridentata saplings (< 1%) and adult patches (15%) occurred less frequently in B. gracilis-dominated ecosystems than expected based on areal extent of this ecosystem type. Propagule pressure did not differ with distance from the core ecosystem dominated by L. tridentata. Evidence for both local and long-distance dispersal events was found. Similar relationships between number of plants and patch area in both grassland types indicate similar patterns in patch expansion. Cover of perennial forbs was higher and cover of dominant grasses was lower in L. tridentata patches compared with the surrounding vegetation for both ecosystem types. Conclusions: Spatial variation in L. tridentata saplings and patches at this biome transition zone is related to the different susceptibilities to invasion by two grassland ecosystems. The persistence of grasslands at this site despite region-wide expansion by L. tridentata may be related to the spatial distribution of B. gracilis-dominated ecosystems that resist or deter invasion by this woody plant.

    Authors

    Peters, Debra P. C.; Yao, Jin; Gosz, James R.

    Year Published

    2006

    Publication

    Journal of Vegetation Science

    Locations
    DOI

    10.1111/j.1654-1103.2006.tb02459.x

    Bottom-up regulation of plant community structure in an aridland ecosystemBaez, Selene2006

    Bottom-up regulation of plant community structure in an aridland ecosystem

    Keywords

    Chihuahuan desert; grassland; long-term study; precipitation; shrubland; small mammals

    Abstract

    We conducted a long-term rodent exclosure experiment in native grass- and shrub-dominated vegetation to evaluate the importance of top-down and bottom-up controls on plant community structure in a low-productivity aridland ecosystem. Using multiple regressions and analysis of covariance, we assessed how bottom-up precipitation pulses cascade through vegetation to affect rodent populations, how rodent populations affect plant community structure, and how rodents alter rates of plant community change over time. Our findings showed that bottom-up pulses cascade through the system, increasing the abundances of plants and rodents, and that rodents exerted no control on plant community structure and rate of change in grass-dominated vegetation, and only limited control in shrub-dominated vegetation. These results were discussed in the context of top-down effects on plant communities across broad gradients of primary productivity. We conclude that bottom-up regulation maintains this ecosystem in a state of low primary productivity that constrains the abundance of consumers such that they exert limited influence on plant community structure and dynamics.

    Authors

    Baez, Selene; Collins, Scott L.; Lightfoot, David; Koontz, Terri L.

    Year Published

    2006

    Publication

    Ecology

    Locations
    DOI

    10.1890/0012-9658(2006)87[2746:BROPCS]2.0.CO;2

    This article contributed by:

    Ecological Society of America

    New opportunities in ecological sensing using wireless sensor networksCollins, Scott L.2006

    New opportunities in ecological sensing using wireless sensor networks

    Keywords

    No keywords available

    Abstract

    Measuring environmental variables at appropriate temporal and spatial scales remains an important challenge in ecological research. New developments in wireless sensors and sensor networks will free ecologists from a wired world and revolutionize our ability to study ecological systems at relevant scales. In addition, sensor networks can analyze and manipulate the data they collect, thereby moving data processing from the end user to the sensor network itself. Such embedded processing will allow sensor networks to perform data analysis procedures, identify outlier data, alter sampling regimes, and ultimately control experimental infrastructure. We illustrate this capability using a wireless sensor network, the Sensor Web, in a study of microclimate variation under shrubs in the Chihuahuan Desert. Using Sensor Web data, we propose simple analytical protocols for assessing data quality "on-the-fly" that can be programmed into sensor networks. The ecological community can influence the evolution of environmental sensor networks by working across disciplines to infuse new ideas into sensor network development.

    Authors

    Collins, Scott L.; Bettencourt, Luis M. A.; Hagberg, Aric; Brown, Renee F.; Moore, Douglas I.; Bonito, Greg; Delin, Kevin A.; Jackson, Shannon P.; Johnson, David W.; Burleigh, Scott C.; Woodrow, Richard R.; McAuley, J. Michael

    Year Published

    2006

    Publication

    Frontiers In Ecology And The Environment

    Locations
    DOI

    10.1890/1540-9295(2006)4[402:NOIESU]2.0.CO;2

    This article contributed by:

    Ecological Society of America

    Spatial variation in remnant grasses after a grassland-to-shrubland state change: Implications for restorationPeters, Debra P. C.2006

    Spatial variation in remnant grasses after a grassland-to-shrubland state change: Implications for restoration

    Keywords

    Bouteloua eriopoda; Larrea tridentata; Flourensia cernua; perennial grasslands; shrub invasion

    Abstract

    Around the world rangelands that have been degraded, such as historical desert grasslands now dominated by woody shrubs, are resistant to restoration efforts. The goal of this descriptive research was to examine the potential for black grama(Bouteloua eriopoda [Torr.] Torr.) recovery by remnant plants in a degraded area as a function of plant location across a landscape. Our objectives were 1) to document the historical dominant vegetation as a perennial grassland and determine broad-scale changes in dominance through time and 2) to examine fine-scale patterns of black grama presence and basal area with respect to microenvironmental conditions that indicate the landscape positions favorable for restoration. Historical vegetation maps starting in 1858, a field survey in 2002-2003 of the location of all individual black grama plants in a 29-ha area, and spatial data layers in a geographic information system were used to address these objectives. Upland grasses, including black grama, dominated the study site in 1858, although tarbush (Flourensia cernua DC.) was the dominant species by 1915, and creosotebush (Larrea tridentata [DC.] Cov.) is the current dominant. A total of 3 334 black grama plants were found for an average density of 0.01 plants . m(-2). High spatial variation was found in the occurrence and basal area of black grama plants that was related to water availability rather than livestock grazing: most plants were found in or adjacent to an arroyo (67%), at a northern aspect (47%), and outside experimental exclosures established in 1930 (43%). Largest average basal areas were found in the livestock exclosure, and in general, average basal area was not related with aspect or canopy microsite. These remnant plants can be used as propagule sources in restoration efforts, and information on microsite conditions for black grama survival can be used to improve restoration potential for similar sites.

    Authors

    Peters, Debra P. C.; Mariotto, Isabella; Havstad, Kris M.; Murray, Leigh W.

    Year Published

    2006

    Publication

    Rangeland Ecology & Management

    Locations
    Additional Information:

    http://srmjournals.org/doi/abs/10.2111/05-202R1.1

    Using Unmanned Aerial Vehicles for Rangelands: Current Applications and Future PotentialsRango, Albert2006

    Using Unmanned Aerial Vehicles for Rangelands: Current Applications and Future Potentials

    Keywords

    No keywords available

    Abstract

    High resolution aerial photographs have important rangeland applications, such as monitoring vegetation change, developing grazing strategies, determining rangeland health, and assessing remediation treatment effectiveness. Acquisition of high resolution images by Unmanned Aerial Vehicles (UAVs) has certain advantages over piloted aircraft missions, including lower cost, improved safety, flexibility in mission planning, and closer proximity to the target. Different levels of remote sensing data can be combined to provide more comprehensive information: 15–30 m resolution imaging from space-borne sensors for determining uniform landscape units; < 1 m satellite or aircraft data to assess the pattern of ecological states in an area of interest; 5 cm UAV images to measure gap and patch sizes as well as percent bare soil and vegetation ground cover; and < 1 cm ground-based boom photography for ground truth or reference data. Two parallel tracks of investigation are necessary: one that emphasizes the utilization of the most technically advanced sensors for research, and a second that emphasizes the minimization of costs and the maximization of simplicity for monitoring purposes. We envision that in the future, resource management agencies, rangeland consultants, and private land managers should be able to use small, lightweight UAVs to satisfy their needs for acquiring improved data at a reasonable cost, and for making appropriate management decisions.

    Authors

    Bestelmeyer, Brandon, Herrick, Jeffrey E., Laliberte, Andrea, Rango, Albert, Steele, Caiti, Schmugge, Thomas, Roanhorse, Abigail and Jenkins, Vince

    Year Published

    2006

    Publication

    Environmental Practice

    Locations
    DOI

    10.1017/S1466046606060224

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