The soil system exists at a junction of and develops as a result of interaction between the geology, atmosphere, hydrology, and vegetation at a given site. From this perspective, soils regulate the exchange of matter and energy between other components of an ecosystem, allowing substances such as water and nutrients, and fluxes of energy to pass through, while reflecting, retaining, or accumulating others at its surface, or within the soil profile.

The soils data collected for the FIFE project provide measurements of key parameters that are necessary to understand and model the dynamics of soils within a grassland ecosystem. The Soil Survey Data describes properties of the major soils within the FIFE site based on the Soil Survey Map. Specific chemical and physical information is given which indicated the fertility, water holding potential, and other factors related to the carrying capacity of that given soil to support vegetative growth.

Other data presented here represent soil properties at specific points across the landscape whose locations are important for more focussed experiments within the project. These data are critical for understanding the density, porosity, water holding capacity, thermal and moisture flux, and other important parameters required for modeling for the sites at which these measurements were taken.

In 1987, the FIFE study area was surveyed by United States Department of Agriculture (USDA), Soil Conservation Service (SCS) personnel. Five major soil series were identified in the FIFE study area as Clime, Benfield, Dwight, Florence, and Tully. Standard soil characterization was performed at a sites representative of each of these five soil series. The characterization included a detailed field description and laboratory analysis of soil physical and chemical properties for each soil layer (horizon). Each of the FIFE sites were classified within one of these major soil series with the exception of Station 13 (6735-SCS) which was classified within the Hobbs soil series. No characterization was performed for the Hobbs series.

These data identify the soil series at each of the FIFE sites as identified by the USDA SCS.

Bulk density describes the weight per unit volume of a given soil sample and is required for converting between soil data given as a weight or volume. These data were collected and measured by KSU/FIFE staff. Samples were taken at most FIFE sites as volumetric cores or with plastic bags to determine the volume.

Field saturated hydraulic conductivity was measured using the constant well head permeameter method (dry auger hole method) at two depths (approximately 10 cm and at greater depth within a different horizon) for five sites representing each of the five major soil series during the 1989 Intensive Field Campaign.

Samples to derive soil moisture release curves were taken at the same locations and at the same depths as the soil hydraulic conductivity measurements. Samples for tension values of .02, .033, and .066 MPa were performed on intact samples; for tension values of 0.1, 0.3, 0.5, 1.0, and 1.5 MPa, soil samples were ground and sieved before measurements were taken.

Soil thermal conductivity was determined at 26 locations within the FIFE sites in October, 1987 using the Hot Wire Method.

These data are miscellaneous derived characteristics for each of the five major soil series at the same depths as the hydraulic conductivity and moisture release curve data. These properties include porosity, saturated water potential, and the B factor (Clapp and Hornberger, 1978).

Soil Survey data is presented here in profile form, i.e., data is available for each soil horizon with depth within the soil profile. Soil series classification are based on a similarity of properties within a whole profile. Users must realize that within a particular soil series, the properties for a given layer (e.g., surface layer or A horizon) may vary within a range permitted by the definition of that series.

Because these data are presented in horizon form, users must decide whether they want to use values for specific horizons (e.g., the clay content of the surface horizon) , as an average for the total profile (e.g., pH for the total soil), or as a cumulative value for the total profile (total organic carbon content summed for each horizon within the profile).

The soil water properties are a derived data set that were determined from soil hydraulic conductivity and moisture release data.

All soils information given here can be related spatially to a point on the landscape represented as a "mapping unit" displayed on the Soil Survey Map. Once the series name within the mapping unit has been identified, information from the Soil Survey Data can be obtained which represents general characteristics of the mapping unit within a range of properties. It is important to understand, however, that the Soil Survey Data are results of meaurements taken from one sampling point within the mapping unit, and thus, may not precisely decribe the soil properties within the unit at a location different from the original sampling point. In fact, soil properties may vary greatly, within an accepted range of values from that sampling point. Other data collected at points of specific interest (i.e. Soil Bulk Density Data, Soil Hydraulic Conductivity Data, Soil Moisture Release Data, Soil Thermal Conductivity Data, and Soil Water Properties) are usable only for the point at which they have been sampled. Extrapolation of data for regional assessment of soil properties must be done with the understanding that measurements were obtained from a minimal number of sample points across the experimental site and may give misleading results.

Note that county soil survey maps were digitized by FIFE staff and are available on CD-ROM Volume 5. These and related data are summarized in the Geographic Reference summary document on this CD-ROM.

The soil survey was performed at a scale of 1:24,000 and thus, the soil series identified correspond to a minimum surveying size of approximately 1.6 ha. Inclusions of other soil series that exist within the FIFE study area are not given here.

Soil bulk density measurements may contain large errors. Sampling was not done consistently, and in the case of the volumetric cores, were not taken specifically for the purpose of determining bulk density. Values given here tend to be lower than expected. More reliable bulk density data is available in the Soil Moisture Transect data set and in the Soil Survey data set.

Soil moisture release measurements were done by different techniques, i.e., those at tensions less than 1 bar were performed on intact cores, while those measured at 1 bar or greater were ground and passed through a 2-mm sieve before being placed on the pressure plate.

There are six soil series identified in the FIFE study area: