Walker Branch Watershed Research Articles

Atmospheric input and origin of selected elements in Walker Branch Watershed, Oak Ridge, Tennessee

The elemental composition and relative contribution to input of precipitation and aerosols have been determined for the Walker Branch Watershed in Oak Ridge, Tennessee, U.S.A. Comparison of elemental ratios in rain to those in local soils indicates that Cu, Hg, and Pb are enriched with respect to soil by a factor of 30 to 170 and must have a non-soil source. Due to inherent problems encountered in determining elemental deposition velocities, elemental input by dry deposition was calculated using literature value upper and lower limits. If the higher deposition velocities are chosen, dry deposition could constitute from 62 to 96% of the total input for selected elements to the watershed.

Elemental analysis of water and air solids by neutron activation analysis

Instrumental neutron activation analysis was used to determine the elemental concentrations in water and air solid samples collected on Nuclepore and Whatman filters from the Walker Branch Watershed. The results from this study show that the trace element concentrations removed by water from the watershed vary seasonally, as well as geographically. The data point up the usefulness and versatility of absolute neutron activation analysis. The NBS Standard Orchard Leaves was assayed in a similar manner, and good agreement was obtained between results here and standard values.

Mass balance of trace elements in Walker branch watershed: relation to coal-fired steam plants.

A mass balance study of trace element flows at the TVA Allen Steam Plant at Memphis showed that most of the released Hg, some Se, and probably most Cl and Br are discharged to the atmosphere as gases. The elements As, Cd, Cu, Ga, Mo, Pb, Sb, Se, and Zn were concentrated in fly ash compared to slag and were more concentrated in the ash discharged through the stack than in that collected by the precipitator, while Al, Ba, Ca, Ce, Co, Eu, Fe, Hf, K, La, Mg, Mn, Rb, Sm, Sr, Ta, Th, and Ti showed little preferential partitioning between the slag and the collected or discharged fly ash. The elements Cr, Cs, Na, Ni, U, and V exhibited behavior intermediate between the latter two groups. This information about stack emissions of trace elements from the Allen Plant was used to estimate the likely range of air concentrations and input (dry and wet deposition) to the Walker Branch Watershed. The watershed, which is on the ERDA reservation at Oak Ridge, is within 20 km of three coal-fired steam plants, two in the TVA system and one belonging to ERDA. The estimated input values are compared to measurements of Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn in wet precipitation falling on the watershed during 1973 and 1974. Dry deposition of these elements could not be measured directly but estimates indicated that this could be of the same order of magnitude as the rainwater input. A six-month mass balance indicated that the watershed efficiently retains Pb (97-98% of the atmospheric input,) Cu (82-84%), while Cr (69%), Mn (57%), Zn (73%), and Hg (69%) are less well retained.

Analysis of Litterfall in a Deciduous Forest on Walker Branch Watershed, Tennessee: Data Stratification by Two Alternative Methods

Litterfall was monitored for 1 year on Walker Branch Watershed (97.5 ha) in eastern Tennessee. Data were collected from 80 plots, each with a 1 m$sup 2$ litter trap, and were stratified in two alternate ways for analysis. In one case, a conventional cover-type map was used to separate the plots into one of four cover types. In the other case, plots were separated into four groups based on multivariate stratification of overstory basal-area data. Subtle differences among strata in seasonal dynamics, total annual quantity, and elemental concentration of litterfall were detected better under the multivariate stratification than under the cover-type stratification. This study demonstrates that analysis of the structure of an ecosystem using multivariate techniques provides a firm basis for subsequent analysis of functions within that system. (auth)

Habitat Selection of Breeding Birds in an East Tennessee Deciduous Forest

Bird populations were sampled between May 30 and July 20, 1972, on twenty—four 0.08—ha plots on Walker Branch Watershed, a primarily deciduous forest located in Anderson County, Tennessee. Univariate analysis of variance was used to test for differences in abundance categories of each bird species with respect to 28 habitat variables. Differences in habitat preferences within major bird families (Picidae, Parulidae, Paridae, and Thraupidae) were apparent from this analysis. Discriminant function analysis was therefore used to order the variables according to their strength in separating abundance categories for 13 of the more abundant bird species. This analysis indicated that some bird species were distributed according to specific habitat variables. For example, Downy Woodpecker abundance was highly correlated with the number of saplings on a plot. Distributions of other species (e.g., the Scarlet Tanager) were not strongly related to any single variable but were related weakly to a large number of variables. The results form a basis for predicting avifaunal composition changes resulting from alteration of habitat structure.

An Integrated Ordination-Classification Analysis of an Intensively Sampled Oak-Hickory Forest

relate the structure to the environment, and develop means of comparing systems. The key to successful synthetic modelling lies in understanding the complex structure of the ecosystem. This structure involves a very large number of interrelated variables and parameters. Hence a good analytic model is a prerequisite for any attempt to create a synthetic model. Our work has been directed toward comparing several quantitative classification methods and combining several classification and ordination techniques into a unified analytic modelling strategy. We have shown how the different techniques complement one another and thus produce a clearer analytic model than any one technique could produce by itself. Another example of the use of complementary techniques is the recent work in the analysis of tropical rainforests (Williams et al. 1969). We have applied the techniques to vegetation data collected during the initial characterization of Walker Branch Watershed. The watershed is a monitored ecosystem on which the secondary effects of forest fertilization are to be studied (Curlin & Nelson 1968). Our goal was to determine whether stands of similar species composition existed which could be used to define vegetation groups. These groups could then be used to make the sampling and study of processes more efficacious.