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2002 Progress Report: Interactions Among Climate, Humans and Playa Wetlands on the Southern High Plains
EPA Grant Number: R829641Title: Interactions Among Climate, Humans and Playa Wetlands on the Southern High Plains
Investigators: McMurry, Scott T. , Dayawansa, W. P. , Dixon, K. R. , Martin, C. F. , Smith, L. M. , Theodorakis, C. W. , Willis, D. B.
Current Investigators: McMurry, Scott T. , Dayawansa, W. P. , Smith, L. M. , Willis, D. B.
Institution: Texas Tech University
EPA Project Officer: Jones, Brandon
Project Period: July 1, 2002 through June 30, 2005 (Extended to June 30, 2006)
Project Period Covered by this Report: July 1, 2002 through June 30, 2003
Project Amount: $900,000
RFA: Assessing the Consequences of Global Change for Aquatic Ecosystems: Climate, Land Use, and UV Radiation (2001)
Research Category: Global Climate Change , Ecological Indicators/Assessment/Restoration
Description:
Objective:We hypothesize that climatic variability, and past, current, and future land-use practices (e.g., crop production, conversion to grasslands) dictate hydroperiod and spatial distribution of wet playas (playas that contain water), influencing the ecological structure of vegetation and animal communities that rely on playa lakes for many life history requisites. The overall goal of this research project is to: test the above hypothesis through the interactive use of climate models and field tests, and model the potential long-term (e.g., 40 years) effects of climate change in the Southern Great Plains on land use, as related to water availability, and subsequent dynamics of playa lakes and biotic communities in playa wetlands. The specific objectives of this research project are to: (1) determine the structure and composition of oral, amphibian, and avian communities in different playa wetland systems; (2) classify the playa system according to the hydroperiod and spatial distribution of wet playas using climatic, soil, and geomorphic data; (3) study population dynamics of vegetative, amphibian, and avian community composition in response to hydroperiod and spatial distribution of wet playas as emergent properties of objectives 1 and 2; and (4) study long-term (40 years) changes in climate (temperature, rainfall amounts, and patterns) and resulting interactions among human influences (e.g., irrigation practices, ground water levels, land-use patterns), hydroperiod and distribution of playas, and responses of biota requiring playa lakes.
Progress Summary:We randomly selected 40 playas (20 with grassland watersheds and 20 with cultivated watersheds) across the Southern High Plains following the main precipitation events in early June 2003. The 40 playas are located in Crosby, Deaf Smith, Floyd, Hale, Hockley, Lamb, Lubbock, and Randall counties.
Hydroperiod (the amount of time a playa contains water) was 12.9 weeks (standard deviation [SD] 4.18) in cropland playas, and 13.4 weeks (SD 5.77) in grassland playas. The numbers of playas containing water were higher in croplands than on grasslands in July, and were higher in grasslands than croplands from August to October.
We conducted three sets of vegetation structure and composition surveys in early July, early August, and September, respectively (120 vegetation structure and 120 composition surveys). The analysis of vegetation data is in progress. Sediment depths currently are being measured in cropland and grassland playas. Depths will be related back to hydroperiod in croplands and grasslands.
We conducted 306 avian surveys (228 at wet playas and 78 at dry playas) from June through October. All the bird species were enumerated biweekly in wet playas. As playas dried, distance sampling methods (point/line transect) were employed to estimate monthly avian density. Among all the avian surveys, 151 surveys were conducted at grassland playas, and 155 surveys were conducted at cropland playas. Ninety-two bird species were observed in playas. The number of species gradually increased from June and peaked in August. A similar trend was observed in both grassland and cropland playa sets. There were 74 and 80 species in grassland playas and cropland playas, respectively, from June to October. In general, the number of individual birds observed was higher in grassland playas than cropland playas. Sophisticated analyses are being conducted to elucidate the dynamics of species composition in grassland and cropland playas.
Amphibian sampling occurred in the same 40 playas used for the bird surveys. Most playas were sampled five times if they were wet; however, we continued to sample playas in which we still found amphibians. A few grassland playas were sampled for much longer than cropland playas. We identified seven species including the Great Plains Toad, Woodhouse's Toad, Plains Spadefoot, New Mexico Spadefoot, Plains Leopard Frog, Spotted Chorus Frog, and Barred Tiger Salamander. The Great Plains Toad, Plains Spadefoot, and New Mexico Spadefoot were the most prevalent species across land uses, but all species were found via different sampling techniques in both land uses. Abundances for certain species identified were significantly different (i.e., one individual of a Woodhouse's Toad seen once on a night transect at a grassland playa compared to seining and day and night transect identification multiple times in a cropland playa). Spea tadpole abundance quickly declined after the first sampling period at the end of June. Ambystoma (salamander) abundance also declined, with an apparent greater decline in grassland playas.
Individually, 0-4 species were identified in seine hauls from any single cropland playa compared to 0-3 species in a single grassland playa. However, grassland playas averaged a slightly higher species richness (2.0 species in grassland and 1.85 species in cropland playas). Six species were identified in seine hauls, with a maximum of five species in any one land-use type. Because spadefoot (Spea) tadpoles are indistinguishable as metamorphs, we decided to combine them and count them as one species.
Transects were conducted during the day and night. We identified four species in both land-use types during night transects. Daytime transects resulted in higher species richness in cropland playas (five species) than grassland playas (four species). Similar to the seining data, we combined the metamorphs of the two spadefoot species.
Call counts were conducted following the U.S. Geological Survey North American Amphibian Monitoring Program protocol. Surveys were conducted until August 18, unless reinundation occurred in a playa. Call count data is still being analyzed.
Software models have been developed to compare extreme value statistics of temperature and rainfall data in the region. These models use the profile maximum likelihood method to find relevant parameters of generalized extreme value distribution. The intended purpose of these models is to quantify the gradients of extreme values of weather data across the Southern Great Plains. One of the stated objectives of the U.S. Environmental Protection Agency (EPA) grant was to use the existing gradient of temperature and rainfall across the Southern Great Plains as a test bed to predict effects of climate changes on plant and animal life, as well as agricultural production. We are in the process of analyzing extreme weather data collected from the National Oceanographic and Atmospheric Association Web Sites.
We currently are reviewing the literature on the economic costs and benefits of wetland management. In addition, we currently are working with the newest release of the Agricultural Policy Environmental Extender (APEX), (version 1310, July 2003) software program developed at the Blackland Research and Extension Center in Temple, TX. APEX will be used to evaluate the environmental consequences of alternative land management practices on lands adjacent to playa lakes. APEX has detailed components for routing water, sediment, nutrients, and pesticides across complex landscapes and channel systems to the watershed outlet. Moreover, APEX is capable of simulating the biological effect of management changes with regard to irrigation, drainage, furrow diking, buffer strips, pesticide use, fertilization, crop selection, reservoir use, tillage, and grazing) in small watersheds (less than 965 mi2). The simulated agronomic and biological response functions for anticipated changes in agricultural land management practices resulting from climatic change will subsequently be linked to the yet-to-be developed economic optimization model. The economic model will serve two purposes. First, it will be used to estimate both the economic impact climatic change will have on production agriculture, and the change in the environmental externality irrigated agriculture imposes on the integrity of the playa lake ecosystem. The second use of the economic model will be to estimate the agricultural cost and environmental benefit of implementing polices to minimize environmental damages.
We currently are collecting data on the agricultural lands adjacent to the surveyed playa wetlands, and it will subsequently be loaded into APEX. We also have developed a panel display for airports that educates the public about the value of playa wetlands and about current research. The display is currently being used at Lubbock International Airport.
Future Activities:Surveys will continue to focus on avian and amphibian community dynamics in grassland and cropland playas, especially in response to hydroperiod and wet playa spatial distribution. How avian and amphibian communities change along with wet and dry phases of playas also will be emphasized. We also will examine the different responses of specific avian guilds to land-use types and hydroperiod. The volume loss by sediments of both grassland and cropland playas will be estimated by measuring sediment depth and elevation changes. This will allow us to further evaluate the impact of land-use types and how they influence amphibian, avian, and vegetation communities. Forty additional playas will be selected for study in the spring of 2004.
Developed estimation methods will be used to validate data and develop models of amphibian migration patterns. Extreme weather gradients will be correlated with gradients of animal and plant populations, as well as agricultural production.
Journal Articles:No journal articles submitted with this report: View all 10 publications for this project
Supplemental Keywords:water, watersheds, land, soil, sediments, global climate, precipitation, ecological effects, animal, population, stressor, ecosystem, terrestrial, aquatic, habitat, cost benefit, survey, conservation, biology, ecology, hydrology, mathematics, modeling, monitoring, surveys, climate models, southwest, Texas, TX, U.S. EPA Region 6, agriculture, amphibians, birds, hydroperiod, playas, prairie, vegetation, wetlands, precipitation. , Water, Air, Scientific Discipline, RFA, Water & Watershed, climate change, Ecological Risk Assessment, Atmospheric Sciences, Hydrology, Watersheds, temperature variables, Global Climate Change, hydrologic models, landscape characterization, land use, vulnerability assessment, wetlands, vegetation models, agriculture, environmental monitoring, climate models, agricultural watershed, anthropogenic processes, climate variability, land and water resources, global change, regional hydrologic vulnerability, water resources, anthropogenic stress
Relevant Websites:
http://www.rw.ttu.edu/smith/Smith_L.htm 
http://www.rw.ttu.edu/smith/playa.htm
Progress and Final Reports:
Original Abstract
2003 Progress Report
Final Report