Statement of the ProblemThe rate and magnitude of ecosystem responses to climatic warming, land-use change, and alterations of major biogeochemical cycles at the Earth’s surface are variable and uncertain, ranging from gradual to abrupt, from moderate to profound. The least understood and least predictable responses—those that are both abrupt and profound—are perhaps those of greatest importance to natural resource managers. Recent examples of such responses include ongoing, drought-induced tree mortality on millions of hectares of forest in New Mexico, Arizona, and southern California; increases in area burned by severe wildfires in the western United States during the late 1980s to the first years of the 21st century; and exceedance of thresholds for eutrophication from atmospheric deposition. In all cases, ecosystem thresholds were quickly exceeded, leading to large and often unexpected changes that will have long-term consequences for protected areas.
ObjetivesProgram element and goal: Terrestrial, Freshwater, and Marine Ecosystems, Goal 3 - Develop indexes of ecosystem sensitivity to change and vulnerability to potential stressors, and tools to predict ecosystem responses to environmental change. Objectives for this program are to observe, conduct research, and synthesize knowledge gained about the function of ecosystems experiencing changes in climate, land use, and biogeochemical cycling. Specific goals are to address (1) how climatic variability and change, alterations in N and C cycles, and land use change are likely to affect spatial and temporal patterns of ecological disturbance, ecosystem processes, and biogeochemical cycles; (2) how changing climate, disturbance, and biogeochemistry are likely to affect the composition, structure, and productivity of terrestrial and aquatic vegetation; and (3) which mountain and arctic resources and ecosystems are likely to be most sensitive/vulnerable to future climatic or biogeochemical change, and what are the possible management responses.
Strategy and Approachhe Integrated Assessments Project incorporates and supports long-term monitoring, experimental studies, ecological and physical modeling, paleoecological reconstructions, remote sensing, and spatial surveys of similar processes. Tasks will be conducted by USGS scientists, their students and collaborators, and stakeholders where appropriate. The approach will be one of rigorous science at all stages, culminating in professional publications or graduate degrees, and knowledge transfer to stakeholders and decision-makers.
Relevance and ImpaceHumankind is one of the two or three major driving environmental forces on Earth today. Over the past several decades we have come to a global awareness of societal ability to affect major Earth system functions, including cycles of water, nutrients, and even climate. Our information on the consequences to both natural ecosystems and human-dominated systems has grown commensurately with our understanding of the human role in changing Earth processes. There is a good chance that some of the changes now occurring due to human actions are irrevocable, launching the Earth into excursions in biogeochemical and water cycling never seen before in the four billion year history of the planet. Society relies completely on natural ecosystem functions for economic and social well-being, and very life support. Integrated Assessments are tools to gather, evaluate, and synthesize information that is important to society and land managers. Thay can include physical and ecosystem research, economic and social science inputs, and collaborative efforts between scientists and decision makers.
Documenting Naturally Occurring Bacteria in Bats
Bat with white-nose syndrome. Photograph by U.S. Fish & Wildlife Service.
White-nose syndrome (WNS) and/or Pseudogymnoascus destructans (P.d.), the causal agent, has spread westward across 26 states and 5 provinces within the eastern United States and Canada, respectively, over a short period of time. In 2015, three tri-colored bats (Perimyotis subflavus), a species found primarily in the eastern United States, tested positive for P.d. in eastern Oklahoma. Until March 2016, the discovery of WNS and P.d. in Washington state, these records represented the westernmost occurrence of the disease causing fungus. In addition, records of P.d from eastern Oklahoma are also on the same latitude and trajectory as a possible corridor to the western United States via northeastern New Mexico and southeastern Colorado. In 2003, tri-colored bats were discovered in northeastern New Mexico, thus suggesting that this species is moving into the West via the riparian corridors of northeastern New Mexico.
Given the proximity of Bent’s Old Fort National Historic Site (BEOL, approx. 135 km away) in southeastern Colorado and Capulin Volcano National Monument (CAVO, approx. 75 km away) in northeastern New Mexico to the record of P. subflavus recorded in 2003, these two monuments are at the frontline to the introduction of P.d. and WNS. Further, Pecos National Historic Park (PECO) is at an ecotone between grassland-woodland and montane forest relative to the two aforementioned national parks and likely possess a greater diversity of bat species that could be affected by WNS. Overall, these sites serve as critical locations prior to exposure to P.d. for the diagnosis of naturally occurring microbiota that could act as natural defenses against WNS.
During the spring and summer of 2016, FORT Scientist Dr. Ernie Valdez and his collaborators at the University of New Mexico sampled bats from all BEOL, CAVO, and PECO in an effort to document naturally occurring bacteria belonging to the group known as Actinobacteria. In general, this particular group of bacteria is known for producing many of the world’s antibiotics. As shown in previous research by Dr. Valdez and his collaborators, some Actinobacteria sampled from the external surfaces of western bats produce antifungal properties that impact the growth of P.d. (see figure 1). The discovery and future testing of the anti-fungal properties from these bacteria may lend themselves as possible bio-control agents against WNS.
Population Genetic Structuring of the Lesser Prairie-chicken
A Lesser Prairie-chicken. Photo by Dan Wundrock with permission.
The goals of this study are to characterize patterns of connectivity across the Lesser Prairie-chicken range, document levels of genetic variability among populations, identify the source population(s) for the region of recent range expansion, and determine the level of introgression with the Greater Prairie-chicken in areas where the two species overlap in distribution. This project is revealing relatively strong population structure that falls largely along ecoregion boundaries. This study also shows that the species is expanding its range into previously unoccupied or sparsely occupied habitat from the mixed grass prairie ecoregion and to a lesser extent from the sand sagebrush ecoregion (due to enrollment of agricultural land into the Conservation Reserve Program) and is actively hybridizing with Greater Prairie-chickens in the area of expansion, information that is highly relevant for management. This research is in collaboration with Texas A&M-Kingsville, Oregon State University, University of North Texas, University of Oklahoma, and the Sutton Avian Research Center.
Patterns and causes of observed piñon pine mortality in the southwestern United States
Meddens, A.J.H., J.A. Hicke, A.K. Macalady, P.C. Buotte, T.R. Cowles, and C.D. Allen
Recently, widespread piñon pine die-off occurred in the southwestern United States. Here we synthesize observational studies of this event and compare findings to expected relationships with biotic and abiotic factors. Agreement exists on the occurrence of drought, presence of bark beetles and increased mortality of larger trees. However, studies disagree about the influences of stem density, elevation and other factors, perhaps related to study design, location and impact of extreme drought. Detailed information about bark beetles is seldom reported and their role is poorly understood. Our analysis reveals substantial limits to our knowledge regarding the processes that produce mortality patterns across space and time, indicating a poor ability to forecast mortality in response to expected increases in future droughts.
Chemical contaminants, health indicators, and reproductive biomarker responses in fish from the Colorado River and its tributaries
Hinck, J.E., V.S. Blazer, N.D. Denslow, K.R. Echols, T.S. Gross, T.W. May, P.J. Anderson, J.J. Coyle, and D.E. Tillitt
We documented arroyo evolution at the tree, trench, and arroyo scales along the lower Rio Puerco and Chaco Wash in northern New Mexico, USA. We excavated 29 buried living woody plants and used burial signatures in their annual rings to date stratigraphy in four trenches across the arroyos. Then, we reconstructed the history of arroyo evolution by combining trench data with arroyo-scale information from aerial imagery, light detection and ranging (LiDAR), longitudinal profiles, and repeat surveys of cross sections. Burial signatures in annual rings of salt cedar and willow dated sedimentary beds greater than 30 cm thick with annual precision. Along both arroyos, incision occurred until the 1930s in association with extreme high flows, and subsequent filling involved vegetation development, channel narrowing, increased sinuosity, and finally vertical aggradation. A strongly depositional sediment transport regime interacted with floodplain shrubs to produce a characteristic narrow, trapezoidal channel. The 55 km study reach along the Rio Puerco demonstrated upstream progression of arroyo widening and filling, but not of arroyo incision, channel narrowing, or floodplain vegetation development. We conclude that the occurrence of upstream progression within large basins like the Rio Puerco makes precise synchrony across basins impossible. Arroyo wall retreat is now mostly limited to locations where meanders impinge on the arroyo wall, forming hairpin bends, for which entry to and exit from the wall are stationary. Average annual sediment storage within the Rio Puerco study reach between 1955 and 2005 was 4.8 × 105 t/yr, 16% of the average annual suspended sediment yield, and 24% of the long-term bedrock denudation rate. At this rate, the arroyo would fi ll in 310 yr.
Effects of riparian vegetation on topographic change during a large flood event, Rio Puerco, New Mexico, USA
Perignon, M.C., G.E. Tucker, E.R. Griffin, and J.M. Friedman
 The spatial distribution of riparian vegetation can strongly influence the geomorphic evolution of dryland rivers during large floods. We present the results of an airborne lidar differencing study that quantifies the topographic change that occurred along a 12 km reach of the Lower Rio Puerco, New Mexico, during an extreme event in 2006. Extensive erosion of the channel banks took place immediately upstream of the study area, where tamarisk and sandbar willow had been removed. Within the densely vegetated study reach, we measure a net volumetric change of 578,050 ± ∼ 490,000 m3, with 88.3% of the total aggradation occurring along the floodplain and channel and 76.7% of the erosion focusing on the vertical valley walls. The sediment derived from the devegetated reach deposited within the first 3.6 km of the study area, with depth decaying exponentially with distance downstream. Elsewhere, floodplain sediments were primarily sourced from the erosion of valley walls. Superimposed on this pattern are the effects of vegetation and valley morphology on sediment transport. Sediment thickness is seen to be uniform among sandbar willows and highly variable within tamarisk groves. These reach-scale patterns of sedimentation observed in the lidar differencing likely reflect complex interactions of vegetation, flow, and sediment at the scale of patches to individual plants.
An integrated model of environmental drivers of growth, carbohydrate balance, and mortality of Pinus ponderosa forests in the Southern Rocky Mountains
Climate-induced tree mortality is an increasing concern for forest managers around the world. We used a coupled hydrologic and ecosystem carbon cycling model to assess temperature and precipitation impacts on productivity and survival of ponderosa pine (Pinus ponderosa). Model predictions were evaluated using observations of productivity and survival for three ponderosa pine stands located across an 800 m elevation gradient in the southern Rocky Mountains, USA, during a 10-year period that ended in a severe drought and extensive tree mortality at the lowest elevation site. We demonstrate the utility of a relatively simple representation of declines in non-structural carbohydrate (NSC) as an approach for estimating patterns of ponderosa pine vulnerability to drought and the likelihood of survival along an elevation gradient. We assess the sensitivity of simulated net primary production, NSC storage dynamics, and mortality to site climate and soil characteristics as well as uncertainty in the allocation of carbon to the NSC pool. For a fairly wide set of assumptions, the model estimates captured elevational gradients and temporal patterns in growth and biomass. Model results that best predict mortality risk also yield productivity, leaf area, and biomass estimates that are qualitatively consistent with observations across the sites. Using this constrained set of parameters, we found that productivity and likelihood of survival were equally dependent on elevation-driven variation in temperature and precipitation. Our results demonstrate the potential for a coupled hydrology-ecosystem carbon cycling model that includes a simple model of NSC dynamics to predict drought-related mortality. Given that increases in temperature and in the frequency and severity of drought are predicted for a broad range of ponderosa pine and other western North America conifer forest habitats, the model potentially has broad utility for assessing ecosystem vulnerabilities.
Using occupancy models to investigate the prevalence of ectoparasitic vectors on hosts: An example with fleas on prairie dogs
Eads, D.A., D.E. Biggins, P.F. Doherty, Jr., K.L. Gage, K.P. Huyvaert, D.H. Long, and M.F. Antolin
Updated Date (text):
Parent Publication Title:
International Journal of Parasitology: Parasites and Wildlife
A new field method was developed to study ectoparasite prevalence on hosts.
We describe the approach using a study of fleas on prairie dogs.
Data were analyzed with occupancy models to account for imperfect detection.
There was a 99.3% probability of detecting a flea on a flea-occupied host.
Flea occupancy varied among months, sites, sampling plots, and hosts.
The field method can be used in the future to study ectoparasite communities.
Abstract Ectoparasites are often difficult to detect in the field. We developed a method that can be used with occupancy models to estimate the prevalence of ectoparasites on hosts, and to investigate factors that influence rates of ectoparasite occupancy while accounting for imperfect detection. We describe the approach using a study of fleas (Siphonaptera) on black-tailed prairie dogs (Cynomys ludovicianus). During each primary occasion (monthly trapping events), we combed a prairie dog three consecutive times to detect fleas (15 s/combing). We used robust design occupancy modeling to evaluate hypotheses for factors that might correlate with the occurrence of fleas on prairie dogs, and factors that might influence the rate at which prairie dogs are colonized by fleas. Our combing method was highly effective; dislodged fleas fell into a tub of water and could not escape, and there was an estimated 99.3% probability of detecting a flea on an occupied host when using three combings. While overall detection was high, the probability of detection was always <1.00 during each primary combing occasion, highlighting the importance of considering imperfect detection. The combing method (removal of fleas) caused a decline in detection during primary occasions, and we accounted for that decline to avoid inflated estimates of occupancy. Regarding prairie dogs, flea occupancy was heightened in old/natural colonies of prairie dogs, and on hosts that were in poor condition. Occupancy was initially low in plots with high densities of prairie dogs, but, as the study progressed, the rate of flea colonization increased in plots with high densities of prairie dogs in particular. Our methodology can be used to improve studies of ectoparasites, especially when the probability of detection is low. Moreover, the method can be modified to investigate the co-occurrence of ectoparasite species, and community level factors such as species richness and interspecific interactions.