Life Sciences Commons^™

A Plea For Scale, And Why It Matters For Invasive Species Management, Biodiversity And Conservation, Nicholas A. Mcmillan, Samuel D. Fuhlendorf, Craig A. Davis, Robert G. Hamilton, Landon. K. Neumann, Samantha M. Cady

Department of Agronomy and Horticulture: Faculty Publications

1. Invasive species are suspected to be major contributors to biodiversity declines worldwide. Counterintuitively, however, invasive species effects are likely scale dependent and are hypothesized to be positively related to biodiversity at large spatial scales. Past studies investigating the effect of invasion on biodiversity have been mostly conducted at small scales (<100 m²) that cannot represent large dynamic landscapes by design. Therefore, replicated experimental evidence supporting a negative effect of invasive plants on biodiversity is lacking across many landscape types, including large grasslands.

2. We collected data across eight large (333–809 ha) grassland landscapes managed with pyric herbivory—that is the recoupling …

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Tracking Spatial Regimes In Animal Communities: Implications For Resilience-Based Management, Caleb P. Roberts, Daniel R. Uden, Craig R. Allen, David G. Angeler, Larkin A. Powell, Brady W. Allred, Matthew O. Jones, Jeremy D. Maestas, Dirac L. Twidwell Jr

Department of Agronomy and Horticulture: Faculty Publications

Spatial regimes (the spatial extents of ecological states) exhibit strong spatiotemporal order as they expand or contract in response to retreating or encroaching adjacent spatial regimes (e.g., woody plant invasion of grasslands) and human management (e.g., fire treatments). New methods enable tracking spatial regime boundaries via vegetation landcover data, and this approach is being used for strategic management across biomes. A clear advancement would be incorporating animal community data to track spatial regime boundaries alongside vegetation data. In a 41,170-hectare grassland experiencing woody plant encroachment, we test the utility of using animal community data to track spatial regimes via two …

Land-Use Type As A Driver Of Large Wildfire Occurrence In The U.S. Great Plains, Victoria M. Donovan, Carissa L. Wonkka, David A. Wedin, Dirac Twidwell

Department of Agronomy and Horticulture: Faculty Publications

Wildfire activity has surged in North America’s temperate grassland biome. Like many biomes, this system has undergone drastic land-use change over the last century; however, how various land-use types contribute to wildfire patterns in grassland systems is unclear. We determine if certain land-use types have a greater propensity for large wildfire in the U.S. Great Plains and how this changes given the percentage of land covered by a given land-use type. Almost 90% of the area burned in the Great Plains occurred in woody and grassland land-use types. Although grassland comprised the greatest area burned by large wildfires, woody vegetation …

Use Of Uav Imagery And Nutrient Analyses For Estimation Of The Spatial And Temporal Contributions Of Cattle Dung To Nutrient Cycling In Grazed Ecosystems, Amanda Shine

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Nutrient inputs from cattle dung are crucial drivers of nutrient cycling processes in grazed ecosystems. These inputs are important both spatially and temporally and are affected by variables such as grazing strategy, water location, and the nutritional profile of forage being grazed. Past research has attempted to map dung deposition patterns in order to more accurately estimate nutrient input, but the large spatial extent of a typical pasture and the tedious nature of identifying and mapping individual dung pats has prohibited the development of a time- and cost-effective methodology. The first objective of this research was to develop and validate …

A Field Study Of Wind Erosion Following A Grass Fire On The Llano Estacado Of North America, J.E. Stout

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Interactions between earth, wind, and fire have always played an important role in the formation and evolution of the level plains of the Llano Estacado of North America. The uppermost sediments of this vast region are aeolian deposits, formed by aeolian deposition into grassland vegetation. Grass cover enhances aeolian deposition by slowing near-surface winds and vegetation secures sediments once they are deposited. The benefits of grass cover, however, are lost when occasional fires remove protective vegetation fromfields. After a fire, the underlying soil surface becomes exposed and susceptible to wind erosion until the vegetative cover is re-established. The purpose of …

Primary Productivity And Water Balance Of Grassland Vegetation On Three Soils In A Continuous Co2 Gradient: Initial Results From The Lysimeter Co2 Gradient Experiment, Philip A. Fay, Alexia M. Kelley, Andrew C. Procter, Dafeng Hui, Virgina L. Jin, Robert B. Jackson, Hyrum B. Johnson, H. Wayne Polley

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Field studies of atmospheric CO₂ effects on ecosystems usually include few levels of CO₂ and a single soil type, making it difficult to ascertain the shape of responses to increasing CO₂ or to generalize across soil types. The Lysimeter CO₂ Gradient (LYCOG) chambers were constructed to maintain a linear gradient of atmospheric CO₂ (~250 to 500 µ 1^-1) on grassland vegetation established on intact soil monoliths from three soil series. The chambers maintained a linear daytime CO₂ gradient from 263 µ 1^-1 at the subambient end of the gradient to 502 …

Physiological And Environmental Regulation Of Interannual Variability In Co2 Exchange On Rangelands In The Western United States, H. Wayne Polley, William Emmerich, James A. Bradford, Phillip L. Sims, Douglas H. Johnson, Nicanor Z. Saliendra, Tony Svejcar, Raymond Angell, Albert B. Frank, Rebecca L. Phillips, Keirith A. Snyder, Jack A. Morgan

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

For most ecosystems, net ecosystem exchange of CO₂ (NEE) varies within and among years in response to environmental change.We analyzed measurements of CO₂ exchange from eight native rangeland ecosystems in the western United States (58 site-years of data) in order to determine the contributions of photosynthetic and respiratory (physiological) components of CO₂ exchange to environmentally caused variation in NEE. Rangelands included Great Plains grasslands, desert shrubland, desert grasslands, and sagebrush steppe.

Root Responses Along A Subambient To Elevated Co2 Gradient In A C3–C4 Grassland, Laurel J. Anderson, Justin D. Derners, H. Wayne Polley, Wendy S. Gordon, David M. Eissenstat, Robert B. Jackson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Atmospheric CO₂ (C_a) concentration has increased significantly during the last 20 000 years, and is projected to double this century. Despite the importance of belowground processes in the global carbon cycle, community-level and single species root responses to rising C_a are not well understood. We measured net community root biomass over 3 years using ingrowth cores in a natural C₃–C₄ grassland exposed to a gradient of C_a from preglacial to future levels (230–550 µmol mol^-1).

Spatiotemporal Dynamics Of Black-Tailed Prairie Dog Colonies Affected By Plague, David J. Augustine, Marc R. Matchett, Theodore P. Toombs, Jack F. Cully, Tommy L. Johnson, J. G. Sidle

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Black-tailed prairie dogs (Cynomys ludovicianus) are a key component of the disturbance regime in semi-arid grasslands of central North America. Many studies have compared community and ecosystem characteristics on prairie dog colonies to grasslands without prairie dogs, but little is known about landscape-scale patterns of disturbance that prairie dog colony complexes may impose on grasslands over long time periods. We examined spatiotemporal dynamics in two prairie dog colony complexes in southeastern Colorado (Comanche) and northcentral Montana (Phillips County) that have been strongly influenced by plague, and compared them to a complex unaffected by plague in northwestern Nebraska (Oglala). …

Increasing Co2 From Subambient To Superambient Concentrations Alters Species Composition And Increases Above-Ground Biomass In A C3/C4 Grassland, H. W. Polley, Hyrum B. Johnson, Justin D. Derner

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The glacial-to-present increase in atmospheric CO₂ concentration is likely to have stimulated plant production, but experimental tests in natural ecosystems are lacking.

Net Grassland Carbon Flux Over A Subambient To Superambient Co2 Gradient, P. C. Mielnick, W. A. Dugas, H. B. Johnson, H. W. Polley, J. Sanabria

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Increasing atmospheric CO₂ concentrations may have a profound effect on the structure and function of plant communities. A previously grazed, central Texas grassland was exposed to a 200-µmol mol^-1 to 550 µmol mol^-1 CO₂ gradient from March to mid-December in 1998 and 1999 using two, 60-m long, polyethylene-covered chambers built directly onto the site. One chamber was operated at subambient CO₂ concentrations (200-360 µmol mol^-1 daytime) and the other was regulated at superambient concentrations (360-550 µmol mol^-1). Continuous CO₂ gradients were maintained in each chamber by photosynthesis during the day and …

Gas Exchange And Photosynthetic Acclimation Over Subambient To Elevated Co2 In A C3-C4 Grassland, Laurel J. Anderson, Hafiz Maherali, Hyrum B. Johnson, H. Wayne Polley, Robert B. Jackson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Atmospheric CO₂ (C_a) has risen dramatically since preglacial times and is projected to double in the next century. As part of a 4-year study, we examined leaf gas exchange and photosynthetic acclimation in C₃ and C₄ plants using unique chambers that maintained a continuous C_a gradient from 200 to 550 µmol mol^-1 in a natural grassland. Our goals were to characterize linear, nonlinear and threshold responses to increasing C_a from past to future C_a levels. Photosynthesis (A), stomatal conductance (g_s), leaf water-use efficiency (A/g_{s …}