W. Dean Kettle

The Responses of Plankton Communities in Experimental Ponds to Atrazine, the Most Heavily Used Pesticide in the United States

Experimental ponds received single additions of the herbicide atrazine in concentra- tions of 20 and 500 gg/L, and were compared to control ponds for 136 d. Atrazine is an inhibitor of photosynthesis, and both concentrations depressed phytoplankton growth in the ponds within a few days. This was followed by successional changes leading to the establishment of species of phyto- plankton more resistant to inhibition by atrazine. Laboratory studies verified this resistance and verified effects on other species at concentrations of atrazine as low as 1-5 Jig/L. When and to what extent resistant species appeared in the phytoplankton communities differed with treatment. At the atrazine concentration of 500 gg/L, there was a delayed appearance but eventually a greater biomass and persistence of these species. The grazing zooplankton influenced these differences and were in turn affected by them. Natural interactions such as competition and predation among the species of the communities greatly affected their responses to the toxic chemical. The importance of atrazine as an environmental pollutant is suggested by these responses to concentrations of 1-5 gg/L, which are common downstream in many agricultural watersheds, 20 /Ig/L, which is the high level found in these waters, and 500 gg/L, which is the high level found in waters directly adjacent to treated fields. zine in experimental ponds. This study will demon- strate both the immediate inhibition of certain species and the secondary effects which such a response has on other species. Species with some tolerance to the effects of the chemical will be identified in the com- munities, and their role in the changing conditions will also be considered. Atrazine (2-chloro-4-ethylamino-6-isopropylamino- s-triazine) is the single most heavily used pesticide in the United States. In 1976, 41 million kilograms (active ingredient) of this herbicide were applied on farms in

Relations between NDVI, Grassland Production, and Crop Yield in the Central Great Plains

Abstract Satellite remote sensing of normalized difference vegetation index (NDVI) provides a means for characterizing landscape level patterns of net primary productivity (NPP). Within the Great Plains, landscapes are dominated by grassland and agricultural ecosystems. We demonstrated that NDVI integrated over time is an excellent measure of prevailing patterns of NPP, which can be measured as biomass production in local‐scale native grasslands (tallgrass prairie), as well as landscape and regional scale yield of corn and wheat. Within the growing season, the temporal pattern of grassland biomass production covaries with NDVI, with a four‐week lag time. Across years, grassland biomass production covaries with NDVI integrated over appropriate time intervals, which can range from part to all of the current growing season. For calculation of landscape patterns of crop production, regional maps (masks) for corn and wheat field identification can be constructed by analysis of temporal patterns of NDVI. Calculation windows that average NDVI for adjacent pixels can enhance the ability to predict local NPP.

Estimation of population size and probabilities of survival and detection in Mead's milkweed

Statistical similarities exist between estimating numbers of cryptic animals and of inconspicuous plants. Without flowers, Meads milkweed ( Asclepias meadii )i s an unobtrusive prairie plant, and most plants flower irregularly. We used maximum likelihood to estimate probabilities of survival and detection for milkweeds in annual censuses during 1992-1999. Initially, we assumed no recruitment and fit models to all data and to flowering plants only. Because plants were marked when located, probabilities of resighting exceeded those of initial discovery. Plants were most likely to flower and be detected in years when the prairie was burned. We marked 177 plants in eight years but estimated the 1992 pop- ulation to be 337 or 191 plants with 166 or 121 surviving to 1999, depending on the data set. Thus, estimated population size exceeded number of plants seen. Estimated annual survival probability was generally

An 11-Year Ecological Study of a Rare Prairie Perennial (Asclepias Meadii): Implications for Monitoring and Management

0.95, but aggregate survival over eight years predicted rapid extinction without recruitment. When we included recruitment, estimates of survival changed little, and estimated population size varied between 118 and 147 individuals. Discovery of new plants in two additional years (2000 and 2001) appeared to be consistent with required recruitment, but simple counts of these plants did not track population trends.

Detection and Plant Monitoring Programs: Lessons from an Intensive Survey of Asclepias meadii with Five Observers

Abstract Meads milkweed, Asclepias meadii, is a rare long-lived perennial of North American tallgrass prairies. Stems of this clonal species are spatially aggregated and, therefore, observing survivorship and flowering of “patches” of stems best approximates the fate of genetic individuals. Population size is likely to be underestimated because more than one genotype can sometimes occur in a patch. The number of patches detected at a site in Kansas has greatly increased over the last 11 y since marking locations of individual patches allowed detection of nonflowering stems in subsequent years. The A. meadii population at our site (managed by biennial dormant-season burning) often had more flowering ramets and produced more mature follicles in years with burning. High rainfall in the preceding year, in conjunction with burning, was associated with the highest follicle production. The difficulties in detection of plants at the site mean that counts of numbers of patches over an 11-y period cannot be used to assess whether the population is increasing, decreasing or remaining constant. Several factors indicate a positive outlook for the population: management (burning) enhances fruit production, patch survivorship is high and a likelihood that more patches exist than are counted. However, the low fruit production in most years at the site is a concern for the long-term viability of the population.

Effects of Cadmium Stress on the Plankton Communities of Experimental Ponds

Monitoring programs, where numbers of individuals are followed through time, are central to conservation. Although incomplete detection is expected with wildlife surveys, this topic is rarely considered with plants. However, if plants are missed in surveys, raw count data can lead to biased estimates of population abundance and vital rates. To illustrate, we had five independent observers survey patches of the rare plant Asclepias meadii at two prairie sites. We analyzed data with two mark-recapture approaches. Using the program CAPTURE, the estimated number of patches equaled the detected number for a burned site, but exceeded detected numbers by 28% for an unburned site. Analyses of detected patches using Huggins models revealed important effects of observer, patch state (flowering/nonflowering), and patch size (number of stems) on probabilities of detection. Although some results were expected (i.e. greater detection of flowering than nonflowering patches), the importance of our approach is the ability to quantify the magnitude of detection problems. We also evaluated the degree to which increased observer numbers improved detection: smaller groups (3–4 observers) generally found 90 – 99% of the patches found by all five people, but pairs of observers or single observers had high error and detection depended on which individuals were involved. We conclude that an intensive study at the start of a long-term monitoring study provides essential information about probabilities of detection and what factors cause plants to be missed. This information can guide development of monitoring programs.

The University of Kansas Field Station: A Platform for Studying Ecological and Hydrological Aspects of Climate Change

Abstract Experimental ponds were used to determine the impact of a single low-level addition of cadmium on naturally occuring plankton communities. Cadmium (as CdCl2) was added to two ponds to create nominal concentrations of 5 μgCd/1 and two ponds served as non-addition controls. Plankton responses were then monitored for 31 days. Cadmium concentrations declined rapidly in treated ponds to < 1 μg/1 by day 10. Biomass and productivity of the phytoplankton community were slightly lower in treated ponds immediately following cadmium addition, but by day 10 had returned to control pond levels. The zooplankton community exhibited a wide range of responses. Simocephalus serrulatus populations were virtually eliminated in treated ponds initially, but later recovered. In situ and laboratory bioassays verified this decreasing effect of cadmium with time. Populations of another cladoceran, Diaphanosoma brachyurum, were enhanced in the cadmium ponds; it appeared earlier and was more abundant on each date sampled. C...

Diet and reproductive success of bluegill recovered from experimental ponds treated with atrazine

The University of Kansas Field Station (KUFS) is a year-round environmental field station located within the ecotone between the eastern deciduous forest and tallgrass prairie of eastern Kansas (Fig. 1). The KUFS mission is to foster scholarly research, environmental education, and science-based stewardship of natural resources. We accomplish our mission by providing the platform—facilities, habitats, databases, and assistance—from which researchers and educators launch innovative programs. Within this framework, KUFS supports many research and teaching efforts, including those focused on understanding the consequences of climate change on ecological and hydrological aspects of ecosystems. This paper provides an overview of KUFS and describes ecohydrological studies there that contribute to understanding climate change.