Grantee Research Project Results
2003 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. , Willis, D. B. , Martin, C. F. , Smith, L. M. , Dayawansa, W. P. , Dixon, K. R. , Theodorakis, C. W.
Current Investigators: McMurry, Scott T. , Willis, D. B. , Smith, L. M. , Dayawansa, W. P.
Institution: Towson University
EPA Project Officer: Packard, Benjamin H
Project Period: July 1, 2002 through June 30, 2005 (Extended to June 30, 2006)
Project Period Covered by this Report: July 1, 2003 through June 30, 2004
Project Amount: $900,000
RFA: Assessing the Consequences of Global Change for Aquatic Ecosystems: Climate, Land Use, and UV Radiation (2001) RFA Text | Recipients Lists
Research Category: Climate Change , Ecological Indicators/Assessment/Restoration , Water , Aquatic Ecosystems
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 goals of this research project are 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:
- determine the structure and composition of oral, amphibian, and avian communities in different playa wetland systems;
- classify the playa system according to the hydroperiod and spatial distribution of wet playas using climatic, soil, and geomorphic data;
- 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 study long-term (40 years) changes in climate (temperature, rainfall amounts and patterns) and resulting interactions among human influences (e.g., irrigation practices, groundwater levels, land-use patterns), hydroperiod and distribution of playas, and responses of biota requiring playa lakes.
Progress Summary:
Forty new wet playas (20 playas with native grassland watersheds and 20 with cropland watersheds) in the Southern High Plains (SHP) were randomly chosen in 2004 using ground surveys, aerial surveys, and maps. All of the new playas were located in Bailey, Briscoe, Crosby, Dawson, Deaf Smith, Floyd, Hale, Hockley, Lamb, Lynn, Parmer, and Swisher counties, in the State of Texas (see Figure 1).
Most playas remained wet during summer 2004 (see Figure 2). Difference of hydroperiod between land uses will be tested later. Sediment depth and percent volume loss will be determined after the playas dry. Of some significance is the fact that 2004 has been an extremely wet year compared to 2003 (roughly four times the rainfall in 2004; about 40-50 inches). Thus, most playas are still wet as of January 2005.
Figure 2. Number of Wet Playas in the SHP From June 2004 to August 2004
Three sets of vegetation structure and composition surveys were conducted each summer. Sixty vegetation structure surveys and 60 vegetation composition surveys were conducted in cropland and grassland playas in both years. Data entry and analysis of these data are in progress.
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 currently is being used at Lubbock International Airport.
Avian Component
To date, we have conducted 211 avian surveys (202 at wet playas [5.05 surveys/playa] and 9 at dry playas [0.225 surveys/playa]) from June through August 2004. Among all avian surveys, 106 and 105 surveys were conducted at cropland and grassland playas, respectively.
We observed 68 bird species across all playas, with 58 species in both cropland and grassland playas. There was no difference in species richness (by playa within a season) between land uses in wet playas (F 1, 38 = 1.56, p = 0.22) or in dry playas (F 1, 38 = 2.14, p = 0.15) during summer 2004 (see Table 1).
In wet playas, species richness did not differ between land uses (F 1, 76 = 0.71, p = 0.40), but richness differed between years (F 1, 76 = 3.03, p = 0.09) (see Table 2). There was no interaction between land use and year (F 1, 76 = 0.95, p = 0.33). Summer 2003 had higher mean species richness (8.01, n = 40, SE = 0.51) than summer 2004 (6.92, n = 40, SE = 0.53).
Table 1. Mean Species Richness (by Playa With a Season), Standard Error (SE), and Sample Playas (numbers [n]) of Wet and Dry Playas in Each Treatment of SHP, Summer 2004
|
Cropland Playas | Grassland Playas | |||||
Mean |
SE |
n |
|
Mean |
SE |
n |
|
Wet |
7.68 |
0.84 |
20 |
|
6.16 |
6.16 |
20 |
|
|
|
|
|
|
|
|
Dry |
1.54 |
0.42 |
6 |
|
2.00 |
0.00 |
1 |
Table 2. Mean Species Richness (by Playa Within a Season), Standard Error (SE), and Number (n) of Wet and Dry Playas in Each Treatment in SHP, Summer 2003 and 2004
Cropland Playas |
|
Grassland Playas | ||||||||||
Mean |
SE |
n |
|
Mean |
SE |
n |
||||||
Wet |
|
|
|
|
|
|
|
|||||
2003 Summer |
7.88 |
0.69 |
20 |
|
8.15 |
0.78 |
20 |
|||||
2004 Summer |
7.68 |
0.84 |
20 |
|
6.16 |
0.61 |
20 |
|||||
Dry |
|
|
|
|
|
|
|
|||||
2003 Summer |
3.23 |
0.62 |
11 |
|
3.77 |
0.52 |
11 |
|||||
2004 Summer |
1.58 |
0.42 |
6 |
|
2.00 |
0.00 |
1 |
Analyses of specific guilds and species, as well as natives versus exotics will be carried out in the future to examine the potential difference between land uses. Density and species diversity also will be compared between different land uses.
The mean area of cropland playas was 9.30 h ectares (SE = 1.89) and 11.97 h ectares (SE = 1.87) in grassland playas (F 1, 38 = 1.00, p = 0.32). The analysis was only conducted with wet playas because there were not enough samples of dry playas during summer. A strong species-area relationship was found in wet playas (Model: mean species richness = 0.25 [area] +1.3, r 2 = 0.176, p = 0.007). This preliminary result in summer 2004 also supports the hypothesis that the number of individuals is the main factor influencing species richness because the number of habitats does not increase as playa area increases (Luo, et al., 1997).
Amphibian Component
Amphibians were sampled in the same 40 playas as birds in 2004. Sampling continued through October 15, which is the average freeze date in this area. In the 2 to 3 weeks prior to October 15, most call counts were not completed because of temperatures deemed too cold for resident amphibians to be calling.
The overall average species richness in grassland playas was 4.35, while in cropland playas the overall average species richness was 3.70. This is an increase and a switch from 2003, in which cropland playas had an average species richness of 3.40, while grassland playas had an average of 3.20 species per playa. Average abundances of Spea spp. tadpoles and Ambystoma tigrinum mavortium larvae were less in 2004 than in 2003 (see Figure 3). Individual sampling methods followed similar trends of average species richness (see Table 3). We hypothesize that some of the differences can be attributed to the moisture present throughout the summer, which may have allowed an increase in movement by amphibians or opportunistic calling; however, because initial inundation of the playas was in midsummer, amphibian fecundity may not have been as high in 2004 as in 2003. Other factors influencing the increase in the number of species detected include proximity to the edge of the Caprock, geographic location of the grassland playas, and effects from previous years.
Table 3. Average Species Richness of Each Sampling Technique by Year and Land-Use
2003 Crop |
2003 Grass |
2004 Crop |
2004 Grass |
|
Seining | 1.85 |
2.00 |
1.95 |
1.90 |
Transects |
1.65 |
1.45 |
1.95 |
2.80 |
Call Counts |
1.50 |
1.20 |
1.95 |
2.20 |
Overall |
3.40 |
3.20 |
3.70 |
4.35 |
Total Species |
8 |
6 |
8 |
10 |
Abiotic factors such as land use, hydroperiod, playa size and depth, geographic range, precipitation, and temperature will be incorporated into analyses that are sensitive to species identity. Approaches we plan to use to distinguish the factors influencing amphibian community composition include Mantel matrix correlation, indirect gradient analysis, redundancy analysis, and canonical correspondence analysis.
Figure 3. Abundance of Spea spp. Tadpoles and A. tigrinum mavortium Larvae Seined Per Playa by Year and Land Use
Modeling Component
We developed a set of procedures that enable us to use the Agricultural Policy Environmental Extender (APEX) computer simulation program to estimate the impact that alternative agricultural land-use practices have on playa hydro-period. APEX was developed at the U.S. Department of Agriculture Blackland Research and Extension Center in Temple, Texas, and has detailed components for routing water, sediment, nutrients, and pesticides across complex landscapes and channel systems into and from watersheds.
APEX now is being used to simulate the effect of soil type, crop selection (cotton, corn, sorghum, wheat), slope (1, 3, and 5 percent slopes), and irrigation technology (center pivot and furrow) on playa hydroperiod and sedimentation rate for a representative playa lake (15.5 hectares of surface area with an average depth of 2 meters) over a 50-year planning horizon under average long-run weather conditions. For each scenario considered (a specific slope/crop/irrigation/soil type combination), the simulated data on per-acre crop yield, the number of wet days, and the volume of stored water within the playa are collected. Preliminary results reveal that both hydroperiod and playa volume will significantly decrease over time in response to existing agricultural land-use practices. Results significantly vary by crop type, soil type, and slope. In the most severe cases, because of heavy sedimentation into the playa, more than 70 percent of a playa’s initial stored volume is lost by the end of the 50-year simulation. As storage volume decreases over time, evaporation increases and hydroperiod decreases.
The simulated APEX data is summarized for two critical time periods each year. The first time period is for the months of May through August, which is an important time period for breeding amphibians. The second time period is for the months of October through February, which is an important time period for winter waterfowl.
The conservation effectiveness and agricultural cost of establishing buffer zones around the representative playa to reduce sedimentation rates into the playa for buffer zones of 15, 30, and 45 feet wide under each alternative land management scenario now is being investigated. Overtime, conservation benefits are measured in terms of reduced cumulative sedimentation levels, the additional number of wet days in each critical period, and the increase in average water volume level in each critical period. Costs are measured in terms of forgone crop yields and the annualized cost to establish and maintain buffer strips.
Establishment and maintenance budgets for the use of buffer strips have been developed. APEX is used to measure crop yield losses because of reduced planted acreage and/or lower per-acre yields because of changing per-acre irrigation water application rates.
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 grant was to use the existing gradient of temperature and rainfall across the Southern Great Plains as a test bed to predict the effects of climate change on plant and animal life, as well as agricultural production. We are in the process of analyzing extreme weather data collected from various National Oceanic and Atmospheric Administration Web sites.
Future Activities:
We will continue to conduct surveys on avian community dynamics in grassland and cropland playas through winter 2004/2005. We also will finish collecting physical data on playas as they dry over the next few months. Much of the future work will be devoted to integrating the results from the field and modeling efforts.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 18 publications | 12 publications in selected types | All 12 journal articles |
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Type | Citation | ||
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Gray MJ, Smith LM, Brenes R. Effects of agricultural cultivation on demographics of Southern High Plains amphibians. Conservation Biology 2004;18(5):1368-1377. |
R829641 (2003) R829641 (Final) |
Exit Exit |
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Gray MJ, Smith LM, Leyva RI. Influence of agricultural landscape structure on a Southern High Plains, USA, amphibian assemblage. Landscape Ecology 2004;19(7):719-729. |
R829641 (2003) R829641 (Final) |
Exit Exit |
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, EPA Region 6, agriculture, amphibians, birds, hydroperiod, playas, prairie, vegetation, wetlands,, RFA, Scientific Discipline, Air, Water, Hydrology, Water & Watershed, climate change, Atmospheric Sciences, Ecological Risk Assessment, Watersheds, anthropogenic stress, water resources, anthropogenic processes, wetlands, environmental monitoring, global change, regional hydrologic vulnerability, agricultural watershed, hydrologic models, playa wetlands, climate models, agriculture, vulnerability assessment, temperature variables, land and water resources, landscape characterization, climate variability, Global Climate Change, land useRelevant Websites:
http://www.rw.ttu.edu/smith/Smith_L.htm Exit
http://www.rw.ttu.edu/smith/playa.htm Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.