Dean W. Coble

SOIL LEACHATE RESPONSES DURING 10 YEARS OF INDUCED WHOLE-WATERSHED ACIDIFICATION

Soil solution was collected from zero-tension lysimeters for 10 yr on two small central Appalachian watersheds in West Virginia, U.S.A. Ammonium sulfate fertilizer was applied to onecatchment 3 times per year during each year. The other watershedwas used as a reference to account for ambient baseline conditions. Ca and Mg concentrations collected below the A- andB-horizons of the treated watershed increased and then decreasedover time as a result of the treatment. By contrast, Ca and Mgconcentrations in the C-horizon continued to increase throughoutthe study period. The depletion in Ca and Mg that occurred inthe upper levels apparently occurred due to charge pairing andleaching of those base cations with NO3 and SO4. Theprogressively greater amounts of Ca and Mg carried through thesoil with these acid anions provided their continued increasingconcentrations in the C-horizon. NO3 concentrations increased progressively with depth due to both the assimilationof NO3 by vegetation and microorganisms in the upper soillayers and leaching of NO3 into deeper soils by mesoporeflow. NO3 became a more important ion over time with respectto pairing and leaching with base cations because its concentrations continued to increase in all soil layers, whereasSO4 became retained in all soil layers after after severalyears of treatment, presumably induced by adsorption from increasing SO3 concentrations.

Relationships Between Habitat and Snag Characteristics and the Reproductive Success of the Brown-headed Nuthatch (Sitta pusilla) in Eastern Texas

Abstract Habitat use and reproductive success of the Brown-headed Nuthatch (Sitta pusilla Latham) were studied in East Texas during the 2001–2002 breeding seasons. We compared nest cavity selection at used and randomly selected non-used areas. Height of nest trees, midstory density, and percent leaf litter were negatively correlated with nest site selection. Brown-headed Nuthatches showed a strong preference for short snags; yet placed their nest cavity entrances near the top of the snags. While nuthatches may be selecting for habitats with little or no midstory density, percent of leaf litter in the nest sites is most likely the consequence of frequent burning. No significant differences among habitat variables and snag characteristics were found between successful and failed nest cavities. Additionally, no habitat variables were correlated with the number of chicks fledged per nest. Predation was the major cause of nest failure in this study.

A survival model for unthinned loblolly pine plantations that incorporates non-planted tree competition, site quality, and incidence of fusiform rust

Future biomass yields are functionally related to the number of trees surviving at a given age. A stand level survival model was developed that incorporates competition of non-planted trees, site quality, and the incidence of fusiform rust (Cronartium quercuum [Berk.] Miyabe ex Shirai f. sp. fusiforme). The model consists of a system of two equations, one of which represents the number of surviving trees infected by fusiform rust while the other represents the number of trees not infected by fusiform rust. Data from unthinned loblolly pine (Pinus taeda L.) plantations in East Texas were used to fit and evaluate the survival model and illustrate its use. The model successfully predicted that the number of surviving loblolly pine trees decreased as the number of non-planted trees increased. The model also successfully predicted the transition of loblolly pine trees from an uninfected to an infected status by fusiform rust.

Plant Communities Associated with Pinus Ponderosa Forests in the Sky Islands of the Davis Mountains, Texas1

Abstract Species composition of Pinus ponderosa P.&C. Lawson var. scopulorum Engelm. forests in the sky islands of the Davis Mountains was evaluated and classified using ordination and classification techniques. Twelve study sites were established within Pinus ponderosa forests in the summers of 2002 and 2003. Overstory (tree) and understory (shrub and herbaceous) vegetation strata were sampled. Thirteen associations were recognized by combining four overstory groups and eight understory groups. The associations reflected a wide range of ecological conditions with Juniperus deppeana associations occupying dry sites and Pinus ponderosa associations occupying wetter sites. The major environmental factors responsible for the differences in vegetation of these forests were altitude, slope position, slope inclination, and soil moisture.

Use of the Centroid Method to Estimate Volumes of Japanese Red Cedar Trees in Southern Korea

Cubic-meter volumes estimated from two proxy taper functions were compared to observed volumes of Japanese red cedar trees (Cryptomeria japonica D. Don) to evaluate accuracy and precision in the centroid method. Centroid volume estimates were also compared to volume estimates from existing whole-tree volume equations developed for another geographic region. This study found that one proxy function produced unbiased volume estimates while the other was biased. Volume estimates from the whole-tree equations were also biased. However, the volume estimates from the whole-tree equations were more precise than those from the centroid method. These results support previous studies that the centroid method can produce reliable volumes of trees when no other reliable volume equations exist.