Ray R. Hicks

Influence of topographic aspect, precipitation and drought on radial growth of four major tree species in an Appalachian watershed

This study used dated and measured tree-ring data to examine relationships between radial growth, topographic aspect, and precipitation for four hardwood species, yellow-poplar (Liriodendron tulipifera L.), northern red oak (Quercus rubra L.), chestnut oak (Quercus prinus L.), and red maple (Acer rubum L.), growing on contrasting aspects in north-central West Virginia (39839 0 43 00 N, 79845 0 28 00 W). The main objectives of the study were to determine variation in growth between northeast and southwest aspects, examine changes in annual growth related to changes in precipitation and Palmer drought severity index (PDSI), and test for the existence of an interaction between species’ growth response to drought and topographic aspect. The study found that all species except northern red oak showed significant differences in growth between the northeast and southwest aspects (P < 0:05). Where significant differences were found, all except chestnut oak exhibited higher growth rates at the northeast aspect. The largest and the least difference in growth between the northeast and southwest aspects were found for yellow-poplar and northern red oak, respectively. Among the four species studied, yellow-poplar showed a sharp decline in growth from the late 1950s to the late 1960s, which was evidently caused by several years of below-average precipitation. The more conservative species, red oak, chestnut oak and red maple, showed a mild response to the drought compared to yellow-poplar which experienced 30‐40% less growth relative to its peak growth in the late 1950s. A rapid growth recovery, in the early 1970s, following the decline in the late 1960s was associated with wetter than average conditions of the early 1970s. Analysis of drought effects in 1953, 1966, 1988 and 1991 indicated that most species experienced below-average growth although drought-related growth declines lasted only for a few years and recovery following drought was rapid. Regarding the interaction of aspect and response to drought, yellow-poplar displayed greater response to periodic droughts at the southwest aspect while the oaks showed little evidence of an aspect-related interaction with drought response. The results of this study are logical in terms of the ecological strategies of the species; yellow-poplar is widely known to be site specific and exploitive, whereas oaks and maples are more conservative. # 2002 Elsevier Science B.V. All rights reserved.

Oak establishment and canopy accession strategies in five old-growth stands in the central hardwood forest region

Using a radial growth averaging technique, decadal-scale changes in growth rates of overstory oaks were used to identify canopy accession events at five old-growth sites. A review of tree-ring chronologies yielded three growth strategies: (1) one-half of the oaks originated in a large opening and achieved overstory status before canopy closure; (2) 38% originated in a smaller opening and required a second gap event to attain overstory status; and (3) 13% achieved overstory status after an extended period of very low growth in understory shade and one or two subsequent gap releases. For trees that required a major canopy release, understory residence times averaged 89, 54, 50 and 38 years for white oak, northern red oak, black oak, and chestnut oak, respectively. Average diameters (inside bark) at canopy accession were 13.3, 11.7, 10.0, and 6.2 cm for the four oak species, respectively. Although there is some historical precedence for these values, few contemporary second-growth forests contain understory oaks of this age, particularly red oak. These long understory residence times suggest that the level of understory shade, and by inference, the abundance of shade tolerant understory species, was considerably less before 1900.

Decomposition of leaf litter in an Appalachian forest: effects of leaf species, aspect, slope position and time

Abstract Leaf decomposition was studied using leaves of three species (yellow-poplar, red maple, and chestnut oak). Litterbags containing 10 g of leaves were placed on a northeast-facing slope and a southwest-facing slope and at three slope positions (upper, middle, and lower) on each aspect. Bags were initially placed in January and samples were removed to determine mass loss beginning in April, then at 2 month intervals until December. The main effects (aspect, species, slope position and time of removal) were all statistically significant. Yellow-poplar and red maple litter decomposed much faster than did chestnut oak, and leaves placed on north-facing slopes decomposed faster than those on south-facing slopes. Generally, leaves placed at the middle slope position decomposed slower than at those at either the upper or lower positions. We examined the microarthropods in leaf litter during the growing season and found that Oribatei and Collembola dominated the populations present. They were generally more abundant in leaves on north-facing slopes, and numbers of microarthropods generally increased throughout the year. Chemical analysis of decomposing leaf litter revealed that nitrogen and phosphorus contents of leaves were relatively stable over time. Sodium dropped quickly at first, then stabilized. Potassium and magnesium decreased with the time whereas calcium increased in the leaves of some species and decreased in others.

Relationship of aspect to soil nutrients, species importance and biomass in a forested watershed in West Virginia

Abstract A relationship between importance values of several tree species and aspect was found in a north-central West Virginia catchment. Corresponding differences in soil chemical properties with aspect were also observed. North and east aspects had larger amounts of manganese and potassium in the A horizon than did south and west slopes. The converse was true for iron and hydrogen ion (acidity). It is proposed that greater quantities of certain elements in the topsoil on north and east aspects relates to more complete litter decomposition and more rapid nutrient cycling on these sites.

Rating forest stand susceptibility to southern pine beetle in East Texas

Abstract A stand rating system was developed from site and stand data collected from 900 beetle-infested and non-infested pine stands in eastern Texas. The model predicts the probability of southern pine beetle attack over a 3-year period and requires data for pine basal area/ha, average tree height, and a categorical evaluation of landform. All variables can readily be determined in the field. Predicted probabilities of attack are valid given certain geographical constraints and assuming epidemic beetle population levels.