David Wm. Smith

Soil and plant water stress in an Appalachian oak forest in relation to topography and stand age

SummaryA Forest Site Quality Index (FSQI) formulated to predict site quality in Ridge and Valley terrain based on the topographic parameters of aspect, slope inclination and slope position was used to verify moisture gradients along the southeast face of Potts Mountain in Craig County, Virginia. A gradient of site quality index values representing xeric to mesic sites was established in both recently clearcut and adjacent uncut second-growth forest stands. Soil moisture content was determined gravimetrically at ten day intervals from May to October, 1981. Plant moisture stress measurements were taken in conjunction with soil moisture sampling using the pressure chamber technique on three dominant hardwood tree species.For both clearcut and uncut forest stands, a general gradient of increasing soil moisture availability with increasing FSQI was evident, although differences were not large between index values of 8 and 11 in either stand type. Soil water potential and predawn plant water potential exhibited a strong seasonal trend, their direct relationship suggesting that available soil water is probably the critical factor controlling base P levels. Growth limiting stress levels began in late July and continued for the remainder of the growing season.

Vegetative Structure of an Appalachian Oak Forest in Southwestern Virginia

Structural parameters were used to assess differences among major vegeta- tion types in an Appalachian oak forest in southwestern Virginia. Cluster analysis re- sulted in ordering stands along a moisture gradient determined from site topographic features. Position along the moisture gradient from mesic to xeric was reflected in a number of vegetative structural variables. For the overstory these included decreased canopy coverage, decreased stand height and decreased stem basal area. Trends in the shrub stratum (l-5m) tended to be the reverse of those in the overstory. The results indicate that vegetative structure is strongly influenced by site relationships reflecting differences in moisture regime. A number of investigators have demonstrated the importance of stand structure to analysis of forest ecosystems. Horn (1971, 1975) examined the relationship be- tween structural development and succession. Whittaker (1956), Mowbray and Oosting (1968) and Whittaker and Woodwell (1969) noted structural and com- positional changes in vegetation along a moisture gradient. Whittaker (1966) demonstrated a relationship between stand structure and forest production in the Great Smoky Mountains of Tennessee. MacArthur and MacArthur (1961), James and Shugart (1970) and Morse (1976) described the importance of vegetation structure in defining certain niche requirements of bird species. The present study attempts to add to existing knowledge of forest ecosystems by structural analysis of major vegetation types in the Appalachian Oak Forest Region of southwestern Virginia. A cluster analysis of vegetative structural attributes is employed to determine interstand distances associated with a topographically de- rived moisture gradient. The relationship between the vertical stratification of foliage in forest stands and the more traditional measures of stand structure is evaluated. Methods Nine sample areas were selected on the SE slope of Potts Mountain in Craig Co., Virginia, to represent a large area of forested land in the Ridge and Valley Province. The areas are noncontiguous and extend across 5.2 km of midslope at approximately 730 m elevation. Slopes vary from 8-45%, while aspect varies from E to SW. Soils are derived mainly from ortho-quartzite sandstone with some interbedded shale outcroppings. Sites range from dry to infertile on main slopes and spur ridges to relatively fertile and mesic in coves. According to Braun (1950), the site falls within the Ridge and Valley Section

A comparison of two water potential predictors for use in plant and soil thermocouple psychrometry

SummaryA linear and a non-linear equation for predicting soil and plant water potentials as measured by thermocouple psychrometric techniques were compared. The non-linear predictor was often just as accurate as the linear predictor. The non-linear predictor did not predict positive water potentials. The non-linear predictor was most accurate in the range of zero to 10 negative bars water potential range. The linear predictor was more accurate than the non-linear predictor when water potentials were larger than −30 bars.

A forest management gaming model of the nitrogen cycle in Appalachian upland oak forests

Abstract A forest management gaming model of the nitrogen cycle, NITCOMP, was developed to simulate changes in gross site nitrogen capital resulting from intensive harvesting on sites of different quality. Version 2.1 of this model provides a user-friendly simulation model of the nitrogen cycle in Appalachian upland oak forest ecosystems. The model incorporates current hypotheses concerning nitrogen cycling in forest ecosystems into a system of 16 differential equations, defined by 47 flow equations with 41 parameters. By design, any of the equations and parameter values which implement current hypotheses may be readily changed to reflect new knowledge or user preferences. Yield table data, which synthesize the effects of climate, soil, and competition, are a major external driving function of the model. The use of yield table data allows the user to account for differences in site quality. The model may be used to portray a single site for which site-specific data are available, or an idealized “average” site when only off-site data are available. NITCOMP allows forest managers to estimate, through a gaming strategy, the harvesting intensity a given site can support without depleting the gross nitrogen capital. The more site-specific information available, the better the forest manager can estimate non-depleting harvesting intensity.

Nutrient distribution in an 8-year-oldPinus virginiana (Mill.) stand

SummaryHalf-sib progeny from ten selected Virginia pine trees were grown on two randomized blocks and harvested at age eight. The trees were divided into four components: foliage, branches, bolewood, and bolebark. The concentration of N, P, K, and Ca was determined for each component of each tree. The results were combined with dry matter distribution data to find the total content of each nutrient for each tree.Significant family effects were observed for Ca concentration in bolewood and Ca content in bolebark. Block effects were significant in many instances. An estimate of the total nutrient content of the above-ground portion of the stand was made for each block.