Mesocosm Projects

Mesocosm Projects at the Konza Prairie
		Experimental mesocosm are being used at the Konza Prairie to simulate future climate conditions projected to occur in the Midwest, USA. These large outdoor experiments provide realistic context for manipulations of precipitation patterns, increased air temperatures, and simulated droughts. Large outdoor facilities like mesocosms allow for complete manipulation of the physical environment to match climate change predictions, automation of sensor networks, and organismal, community, and ecosystem ecological research in a natural setting. This approach provides more realism and has many advantages over laboratory studies, or small-plot field research. At present, there are two current mesocosm facilities and one pending facility. The RaMPs facility was established in 1997 to manipulate the role of altered patterns of precipiation on tallgrass communities, The aboveground mesocosms were established in 2003 to alter both rainfall patterns and amount in a factorial matrix.
RaMPs Experiment; Photo © Judd Patterson 2004

The RaMPs Project:
The Rainfall Manipulations Plots (RaMPs) were originally established by Dr. Alan Knapp (Colorado State University) and Dr. John Blair (Kansas State University) and have been funded by NSF, NRI, and DOE over the past 10 years. This experiment has 15 seperate mesocosms consisting of 3 experimental shelter treatments: 3 unsheltered controls, 6 sheltered controls, and 6 sheltered treatments. Experimental manipulations of rainfall and temperature are conducted in a split-plot design, with rainout shelters as whole plots and warming treatments as subplots. Two rainfall treatments are prescribed to the sheltered treatments. The sheltered control plots receive the natural amount and pattern of precipiation experienced on site. The sheltered treatment plots receive a 50% extension of the natural interval between rainfall events, but the same total amount of precipitation received over the summer is applied. This results in more infrequent events of a greater magnitude. Each RaMP and unsheltered plot contains four 2 x 2-m subplots. Two of the subplots receive 20-25 W m -2 of downward infrared radiation to the soil surface/plant canopy year round from infrared lamps suspended 1.2 m above the canopy. A sheet metal housing identical in size to the lamps is suspended above a third sub plot to control for the presence of the lamp housing, and the fourth subplot is unaltered. Lamp height is increased periodically as the canopy height increases. The microclimate beneath the rainout shelters is characterized in four rainfall manipulation shelters and in an unsheltered control plot. Measurements of PFD are made with a quantum sensor (LI-190SB), and net radiation with a Fritschen-type net radiometer. Soil, air (shielded, aspirated), and stored water temperatures are measured with thermisters. Radiation and air temperature sensors are mounted in the center of the plot, 1.5 m above ground level. To characterize the warming treatments, thermisters or thermocouples are buried at 2, 5 and 15cm in warmed and ambient subplots, and canopy temperatures are monitored with infrared thermometers. Sensor outputs are recorded on Campbell CR10X data loggers. Temporal patterns of soil water content are measured weekly using time domain reflectometry. Stainless steel probes are inserted to 15 and 30 cm depths in each heated and unheated subplot, and moisture content determinations are made with a Tektronix 1502B cable tester. This experiment provides a novel platfrom to measure changes in the tallgrass prairie from the simulated effects of key constructs of global climate change: altered precipiation patterns and elevated air temperatures.Using the 10-year dataset measuring these effects, multiple investigators are presently relating changes seen at the organismal, community and ecosystem level to environmental alterations mimicing projected climate changes.
An individual shelter in the RaMPs. Black containers contain stored rainfall.		Collaborative summer fieldwork within the RaMPs


The Aboveground Mesocosms:
With Dr. Clint Springer (St. Joseph's University) and Dr. Phil Fay (USDA-ARS), we are investigating how plasticity in plant functioning varies in response to future climate changes and how this will impact populations of Panicum virgatum in native tallgrass prairie. Our focus is on populations of switchgrass (P. virgatum, a C4 grass), which occurs throughout eastern North America, and is a dominant plant species within tallgrass prairie ecosystems. P.virgatum ecotypes are genotypically and phenotypically diverse, and commonly exhibit broad adaptation to a range of environmental variability. Climatic variability within the central Great Plains is predicted to increase in the future, with the most likely impacts on changes in precipitation. Currently, there is uncertainty for directional changes in annual precipitation amount (wetter / drier), but there is less uncertainty that future changes in climate will alter the distribution of precipitation events. Additionally, atmospheric N deposition continues to increase in this region. In order to accurately predict the ecological responses to future climate change, it is imperative we assess the evolutionary responses to future climate change. Using the mesocosm faciltity, we are imposing experimental treatments that simulate two forms of altered precipitation pattern: a longer interval between rainfall events and an equal distribution of rainfall between the growing and non-growing seasons. Mesocosms are cultivated using native P. virgatum ecotypes collected from 4 populations spanning the historic latitudinal gradient of tallgrass prairie in the Great Plains: S. Dakota, Kansas, Oklahoma, and Texas.

The mesocosms were established by Dr. Phil Fay in 2003 (USDA-ARS, Temple, TX), and initally funded by NSF. This facility contains 64 seperate containers arranged in two banks of 32 (2 x 16). The containers are 1.2 m x 1.2 m with a depth of 1.8 m (2.6 m³). They are constructed of 12 mm plywood lined with 0.15 mm polyethylene. These dimensions provide a large soil volume for root development, and allow for a 1.0 x 1.0 m central sampling area where soil attributes and above- and belowground plant responses can be measured without edge effects from the mesocosm walls. Each mesocosm container is equipped with automated soil moisture probes (TDR-100) to measure volumetric water content in the top 30-cm and a mini-rhizotron access tube to measure root turnover and productivity.

Mescosom facility with permanent, transparent roof		Dr. Clint Springer & Jacob Carter planting switchgrass (2008)