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
A Comparison of Cover Pole With Standard Vegetation Monitoring MethodsToledo P, David2010

A Comparison of Cover Pole With Standard Vegetation Monitoring Methods

Keywords

assessment;gap intercept;habitat quality;monitoring;visual obstruction;wildlife habitat

Abstract

The ability of resource managers to make informed decisions regarding wildlife habitat could be improved with the use of existing data sets and the use of cost-effective, standardized methods to simultaneously quantify vertical and horizontal cover. We characterized vegetation structure of 3 semiarid plant communities to compare cover pole measurements, standard measurements of vegetation cover, composition, height, and the proportion of the soil surface exposed by large intercanopy gaps. We propose that a more versatile and interpretable description of wildlife habitat can be generated using a line-point intercept method together with measurements of vegetation height and the proportion of the soil surface exposed by large intercanopy gaps. © The Wildlife Society.

Authors

Toledo P, David, Herrick, Jeffrey E. and Abbott, Laurie B.

Year Published

2010

Publication

Journal of Wildlife Management

Locations
DOI

10.2193/2009-136

Above- and belowground responses to nitrogen addition in a Chihuahuan Desert grasslandLadwig, Laura M.2012

Above- and belowground responses to nitrogen addition in a Chihuahuan Desert grassland

Keywords

Semiarid grassland; N deposition; Aboveground production; Belowground production; Species richness

Abstract

Increased available soil nitrogen can increase biomass, lower species richness, alter soil chemistry and modify community structure in herbaceous ecosystems worldwide. Although increased nitrogen availability typically increases aboveground production and decreases species richness in mesic systems, the impacts of nitrogen additions on semiarid ecosystems remain unclear. To determine how a semiarid grassland responds to increased nitrogen availability, we examined plant community structure and above- and belowground net primary production in response to long-term nitrogen addition in a desert grassland in central New Mexico, USA. Plots were fertilized annually (10 g N m(-2)) since 1995 and NPP measured from 2004 to 2009. Differences in aboveground NPP between fertilized and control treatments occurred in 2004 following a prescribed fire and in 2006 when precipitation was double the long-term average during the summer monsoon. Presumably, nitrogen only became limiting once drought stress was alleviated. Belowground NPP was also related to precipitation, and greatest root growth occurred the year following the wettest summer, decreasing gradually thereafter. Belowground production was unrelated to aboveground production within years and unrelated to nitrogen enrichment. Species richness changed between years in response to seasonal precipitation variability, but was not altered by nitrogen addition. Community structure did respond to nitrogen fertilization primarily through increased abundance of two dominant perennial grasses. These results were contrary to most nitrogen addition studies that find increased biomass and decreased species richness with nitrogen fertilization. Therefore, factors other than nitrogen deposition, such as fire or drought, may play a stronger role in shaping semiarid grassland communities than soil fertility.

Authors

Ladwig, Laura M.; Collins, Scott L.; Swann, Amaris L.; Xia, Yang; Allen, Michael F.; Allen, Edith B.

Year Published

2012

Publication

Oecologia

Locations
DOI

10.1007/s00442-011-2173-z

Aboveground net primary production dynamics in a northern Chihuahuan Desert ecosystemMuldavin, Esteban H.2008

Aboveground net primary production dynamics in a northern Chihuahuan Desert ecosystem

Keywords

aboveground net primary production; Bouteloua eriopoda; chihuahuan desert; desert grassland; desert shrubland

Abstract

Aboveground net primary production (ANPP) dynamics are a key element in the understanding of ecosystem processes. For semiarid environments, the pulse-reserve framework links ANPP to variable and unpredictable precipitation events contingent on surficial hydrology, soil moisture dynamics, biodiversity structure, trophic dynamics, and landscape context. Consequently, ANPP may be decoupled periodically from processes such as decomposition and may be subjected to complex feedbacks and thresholds at broader scales. As currently formulated, the pulse-reserve framework may not encompass the breadth of ANPP response to seasonal patterns of precipitation and heat inputs. Accordingly, we examined a 6-year (1999-2004), seasonal record of ANPP with respect to precipitation, soil moisture dynamics, and functional groups in a black grama (Bouteloua eriopoda) grassland and a creosotebush (Larrea tridentata) shrubland in the northern Chihuahuan Desert. Annual ANPP was similar in the grassland (51.1 g/m(2)) and shrubland (59.2 g/m(2)) and positively correlated with annual precipitation. ANPP differed among communities with respect to life forms and functional groups and responses to abiotic drivers. In keeping with the pulse-reserve model, ANPP in black grama grassland was dominated by warm-season C-4 grasses and subshrubs that responded to large, transient summer storms and associated soil moisture in the upper 30 cm. In contrast, ANPP in creosotebush shrubland occasionally responded to summer moisture, but the predominant pattern was slower, non-pulsed growth of cool-season C-3 shrubs during spring, in response to winter soil moisture accumulation and the breaking of cold dormancy. Overall, production in this Chihuahuan Desert ecosystem reflected a mix of warm-temperate arid land pulse dynamics during the summer monsoon and non-pulsed dynamics in spring driven by winter soil moisture accumulation similar to that of cool-temperate regions.

Authors

Muldavin, Esteban H.; Moore, Douglas I.; Collins, Scott L.; Wetherill, Karen R.; Lightfoot, David C.

Year Published

2008

Publication

Oecologia

Locations
DOI

10.1007/s00442-007-0880-2

Acquisition, Orthorectification, and Object-based Classification of Unmanned Aerial Vehicle (UAV) Imagery for Rangeland MonitoringLaliberte, Andrea S.2010

Acquisition, Orthorectification, and Object-based Classification of Unmanned Aerial Vehicle (UAV) Imagery for Rangeland Monitoring

Keywords

No keywords available

Abstract

The use of unmanned aerial vehicles (UAVs) for natural resource applications has increased considerably in recent years due to their greater availability, the miniaturization of sensors, and the ability to deploy a UAV relatively quickly and repeatedly at low altitudes. We examine in this paper the potential of using a small UAV for rangeland inventory, assessment and monitoring. Imagery with a ground resolved distance of 8 cm was acquired over a 290 ha site in southwestern Idaho. We developed a semiautomated orthorectification procedure suitable for handling large numbers of small-footprint UAV images. The geometric accuracy of the orthorectified image mosaics ranged from 1.5 m to 2 m. We used object-based hierarchical image analysis to classify imagery of plots measured concurrently on the ground using standard rangeland monitoring procedures. Correlations between imageand ground-based estimates of percent cover resulted in r-squared values ranging from 0.86 to 0.98. Time estimates indicated a greater efficiency for the image-based method compared to ground measurements. The overall classification accuracies for the two image mosaics were 83 percent and 88 percent. Even under the current limitations of operating a UAV in the National Airspace, the results of this study show that UAVs can be used successfully to obtain imagery for rangeland monitoring, and that the remote sensing approach can either complement or replace some ground-based measurements. We discuss details of the UAV mission, image processing and analysis, and accuracy assessment.

Authors

Laliberte, Andrea S., Herrick, Jeffrey E., Rango, Albert and Winters, Craig

Year Published

2010

Publication

Photogrammetric Engineering & Remote Sensing

Locations
DOI

10.14358/pers.76.6.661

Assessing Impacts of Roads: Application of a Standard Assessment ProtocolDuniway, Michael C.2013

Assessing Impacts of Roads: Application of a Standard Assessment Protocol

Keywords

adaptive management, assessment, monitoring, off-highway vehicles, oil and gas, rangeland health

Abstract

Adaptive management of road networks depends on timely data that accurately reflect the impacts those systems are having on ecosystem processes and associated services. In the absence of reliable data, land managers are left with little more than observations and perceptions to support management decisions of road-associated disturbances. Roads can negatively impact the soil, hydrologic, plant, and animal processes on which virtually all ecosystem services depend. The Interpreting Indicators of Rangeland Health (IIRH) protocol is a qualitative method that has been demonstrated to be effective in characterizing impacts of roads. The goal of this study were to develop, describe, and test an approach for using IIRH to systematically evaluate road impacts across large, diverse arid and semiarid landscapes. We developed a stratified random sampling approach to plot selection based on ecological potential, road inventory data, and image interpretation of road impacts. The test application on a semiarid landscape in southern New Mexico, United States, demonstrates that the approach developed is sensitive to road impacts across a broad range of ecological sites but that not all the types of stratification were useful. Ecological site and road inventory strata accounted for significant variability in the functioning of ecological processes but stratification based on apparent impact did not. Analysis of the repeatability of IIRH applied to road plots indicates that the method is repeatable but consensus evaluations based on multiple observers should be used to minimize risk of bias. Landscape-scale analysis of impacts by roads of contrasting designs (maintained dirt or gravel roads vs. non- or infrequently maintained roads) suggests that future travel management plans for the study area should consider concentrating traffic on fewer roads that are well designed and maintained. Application of the approach by land managers will likely provide important insights into minimizing impacts of road networks on key ecosystem services.

Authors

Duniway, Michael C. and Herrick, Jeffrey E.

Year Published

2013

Publication

Rangeland Ecology & Management

Locations
DOI

10.2111/rem-d-11-00130.1

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

Differential performance of reciprocal hybrids in multiple environmentsKimball, Sarah2008

Differential performance of reciprocal hybrids in multiple environments

Keywords

cytoplasmic genes, elevational gradient, genotype-by-environment interactions, hybridization, hybrid zones, local adaptation, Penstemon , reciprocal transplant experiment, Sierra Nevada

Abstract

1. Closely related taxa may be maintained as distinct species by a variety of reproductive isolating mechanisms. These include: inability to produce hybrid offspring, endogenous selection against hybrids in the form of genomic incompatibilities, and exogenous selection observable in genotypeby- environment interactions. To understand the relative importance of these three isolating mechanisms, we performed hand-pollination and reciprocal transplant experiments in a natural plant hybrid zone. 2. We measured reproductive isolation by making crosses between two parent species of Penstemon and naturally occurring hybrids. Inclusion of reciprocal hybrid crosses allowed us to determine whether fitness components differed depending on the identity of the mother. 3. Hybrid performance was evaluated in the greenhouse and in a reciprocal transplant experiment in the field. We measured fruit set, seed set, seed weight, time required for fruits to mature and seedling growth for potted plants. To test for exogenous isolation, we planted pure parents, reciprocal F 1 hybrids and later generation hybrids in a reciprocal transplant experiment, and measured survival. 4. On average, interspecific crosses produced as many seeds as conspecific crosses. Hybrid performance was also equal to or greater than parents in all environments, including the greenhouse and all field gardens, indicating a lack of endogenous isolation. Parent species and reciprocal F 1 hybrids differed in many traits measured. In each field garden, the hybrid with the native cytoplasm had a higher survival rate, suggesting local adaptation to different elevations. 5. Synthesis . Exogenous factors that differ along elevational gradients can be more important than intrinsic genetic incompatibilities in determining the fitness of plant hybrids. Our results illustrate the importance of studying hybrid performance in multiple environments and in generating reciprocal hybrids to test for isolating mechanisms in natural hybrid zones.

Authors

Kimball, Sarah, Campbell, Diane R. and Lessin, Carrie

Year Published

2008

Publication

Journal of Ecology

Locations
DOI

10.1111/j.1365-2745.2008.01432.x

Directional climate change and potential reversal of desertification in arid and semiarid ecosystemsPeters, Debra P. C.2012

Directional climate change and potential reversal of desertification in arid and semiarid ecosystems

Keywords

extreme events; grasslands; regime shift; shrublands; spatial context; wet-dry climatic periods

Abstract

Our objective was to determine if long-term increases in precipitation can maintain grasslands susceptible to desertification, and initiate a reversal of historic regime shifts on desertified shrublands. Perennial grass production and species richness in a multi-year wet period were hypothesized to be greater than expected based on precipitation in a sequence of dry years. These responses were expected to differ for grasslands and shrublands with different dominant species and topo-edaphic properties. Long-term trends in desertification were documented using vegetation maps beginning in 1858, 1915, 1928, and 1998). These trends were compared with herbaceous and woody species responses to a sequence of dry (19942003) and wet years (20042008) for two grassland (uplands, playas) and three desertified shrubland types (honey mesquite, creosotebush, tarbush) in the Chihuahuan Desert. Analyses showed that both types of grasslands decreased in spatial extent since 1858 whereas areas dominated by mesquite or creosotebush increased. Production of upland grasslands in the wet period was greater than expected based on responses during the dry period whereas the relationships between species richness and precipitation was the same for both periods. Precipitation was not important to responses in playa grasslands in either period. For all ecosystem types, the production response in wet years primarily was an increase in herbaceous plants, and the most pronounced responses occurred on sandy sites (upland grasslands, mesquite shrubland). Results suggest that multiple wet years are needed to initiate a sequence of grass establishment and survival processes that can maintain upland grasslands without management inputs and lead to a state change reversal in desertified shrublands. Restoration strategies need to take advantage of opportunities provided by future climates while recognizing the importance of ecosystem type.

Authors

Peters, Debra P. C.; Yao, Jin; Sala, Osvaldo E.; Anderson, John P.

Year Published

2012

Publication

Global Change Biology

Locations
DOI

10.1111/j.1365-2486.2011.02498.x

Discovering Ecologically Relevant Knowledge from Published Studies through Geosemantic SearchingKarl, Jason W.2013

Discovering Ecologically Relevant Knowledge from Published Studies through Geosemantic Searching

Keywords

georeferencing, metadata, semantic search, spatial distribution, knowledge discovery

Abstract

It is easier to search the globe for research on the genes of a local plant than it is to find local research on that plant’s ecology. As a result, ecologists are often unaware of published local research and unlikely to find relevant studies from similar environments worldwide. Location information in ecological studies can be harnessed to enable geographic knowledge searches and could be standardized to make searches more fruitful. To demonstrate this potential, we developed the JournalMap Web site (www.journalmap.org). Easy access to geographic distributions of knowledge opens new possibilities for using ecological research to detect and interpret ecological patterns, evaluate current ecological knowledge, and facilitate knowledge creation. We call on journals and publishers to support standard reporting of study locations in publications and metadata, and we advocate georeferencing past studies.

Authors

Karl, Jason W., Herrick, Jeffrey E., Unnasch, Robert, Gillan, Jeffrey K., Ellis, Erle C., Lutters, Wayne G. and Martin, Laura J.

Year Published

2013

Publication

BioScience

Locations
    DOI

    10.1525/bio.2013.63.8.10

    Does shrub invasion indirectly limit grass establishment via seedling herbivory? A test at grassland-shrubland ecotonesBestelmeyer, Brandon T.2007

    Does shrub invasion indirectly limit grass establishment via seedling herbivory? A test at grassland-shrubland ecotones

    Keywords

    alternative state; Bouteloua eriopoda; Chihuahuan Desert; desertification; Dipodomys; foraging behavior; Lepus californicus; restoration; small mammal

    Abstract

    Question: Does shrub invasion at ecotones indirectly limit grass establishment by increasing mammalian seedling herbivory? Location: Chihuahuan Desert, New Mexico, USA. Methods: We tested the hypothesis that herbivore-related mortality of seedlings of the dominant perennial grass Bouteloua eriopoda would be highest in shrub-dominated portions of grassland-shrubland ecotones. We tested the hypothesis in two Chihuahuan Desert sites featuring similar shrub encroachment patterns but different shrub species, grass cover, and different abundances of small mammals. Within each site we transplanted B. eriopoda seedlings to grass-dominated, middle, and shrub-dominated positions of replicate ecotones during the time of year (mid-summer) when they would naturally appear and monitored seedling fates. We estimated population size/activity of putative small mammal herbivores. Results: Seedlings were killed by mammals in greater numbers in shrubland than in grassland or middle ecotone positions at the site with large herbivore numbers. At the site with low herbivore numbers, most seedlings were killed in middle ecotone positions. The abundance patterns of herbivores did not parallel patterns of seedling herbivory across the ecotones or between sites. Conclusions: Seedling herbivory is an important process and is related to vegetation composition, but the mechanisms underlying the relationship are not clear. We speculate that variation in small mammal foraging behavior may contribute to seedling herbivory patterns. Restoration strategies in the Chihuahuan Desert need to account for the abundance and/or behavior of native herbivores.

    Authors

    Bestelmeyer, Brandon T.; Kalil, N. I.; Peters, Debra P. C.

    Year Published

    2007

    Publication

    Journal of Vegetation Science

    Locations
    DOI

    10.1111/j.1654-1103.2007.tb02548.x

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