Shepard M. Zedaker

Fine root biomass, distribution, and production in young pine-hardwood stands

Patterns of fine root biomass, production, and distribution were estimated for pure stands and mixtures of three-year-old loblolly pine (Pinus taeda L.) with red maple (Acer rubrum L.) or black locust (Robinia pseudoacacia L.) on the Virginia Piedmont to determine the role of fine roots in interference between pine and hardwood tree species. Estimates were based on amounts of live and dead fine roots separated from monthly core samples during the third growing season after planting. Live and dead fine root biomass and production varied by species, but mixtures of loblolly pine and black locust generally had greater fine root biomass and fine root production than pure stands or loblolly pine-red maple mixtures. Hardwood species had greater live fine root biomass per tree in mixtures with pine compared to pure stands. Greater live fine root biomass in pine-locust stands may be attributed to differential utilization of the soil volume by fine roots of these species. For all stands, approximately 50% of live five root biomass was located in the upper 10 cm of soil.

Control of rhododendron (Rhododendron ponticum and R. flavum) in the eastern beech (Fagus orientalis) forests of Turkey

Because purple-flowered rhododendron (Rhododendron ponticum L.) and yellow-flowered rhododendron (R. flavum Don.) significantly reduce seedling growth and regeneration of eastern beech (Fagus orientalis Lipsky) as well as local floristic diversity in northern Turkey, effective and cost-efficient woody control is needed. Various manual (cut and grub) and herbicide (foliar and cut-stump spray) woody control techniques were used in two different beech-rhododendron sites in the Black Sea Region (BSR) of Turkey. Two years later, biological and economic effectiveness were substantially greater with foliar-applied herbicide and grubbing treatments than with the cutting, cut-stump, and check treatments. Yet, grubbing showed a great potential for sprout crown reduction. Cut-stump spray was intermediate in effectiveness. Cutting had the least woody control and economic effectiveness among all of the treatments. Foliar-applied Arsenal SL (imazapyr) had significantly greater rhododendron control than foliar-appliied Garlon 4 (triclopyr ester). Increasing rates did not enhance herbicide efficacy. Reducing rates further may provide the same level of control at less cost.

Succession dynamics in a maritime forest following Hurricane Hugo and fuel reduction burns

Abstract In 1989, Hurricane Hugo devastated the maritime forest communities on Bull Island, SC, where a system of permanent plots was established. This catastrophic disturbance and subsequent fires provided an opportunity to study secondary succession following interacting disturbances. This study quantifies the effects of the disturbances on woody vegetation and investigates potential long-term community change using TWINSPAN. Overstory live oak ( Quercus virginiana Miller) remained relatively intact, whereas old-growth loblolly pines ( Pinus taeda L.) and stands of the exotic tallow tree ( Sapium sebiferum (L.) Roxb.) were destroyed. Aggressive recruitment by S. sebiferum , unfavorable conditions for loblolly growth, and broad changes in sapling community composition indicate that successional trajectories in some sites may have been changed by severe disturbances.

Short-term effects of hexazinone applications on woody species diversity in young loblolly pine (Pinus taeda) plantations

Abstract Data from four studies determining the susceptibility of woody plant species to foliar applications of several rates of liquid hexazinone (Velpar L®) were used to examine the short-term effects of the herbicide on woody species diversity in young loblolly pine plantations. Woody species diversity, as measured by four similarity measures between pretreatment and post-treatment species importance or diversity, decreased significantly with increasing hexazinone rate. Woody species shown to be among the most susceptible (sumacs ( Rhus spp.) and oaks ( Quercus spp.)), and least susceptible (loblolly and other pines, and Vaccinium spp.) to hexazinone in previous herbicide screening trials decreased and increased in importance, respectively. Differences in similarity measures between the no-hexazinone treatment and the 1.0 × hexazinone rate (1.2 to 1.5 kg a.i./ha depending on the study location) 2 years after herbicide application were small.

Stand characteristics of inter-cropped loblolly pine and black locust

Abstract Inter-cropping conifers and hardwoods provides greater economic flexibility, biological diversity and aesthetic benefits, relative to traditional, single species plantations. This study evaluates the biological feasibility of inter-cropping loblolly pine (Pinus taeda L.) and black locust (Robinia pseudoacacia L.). Seedlings of both species were established from 1-0 seedlings in pure stands and 25:75, 50:50 and 75:25 mixtures under tall fescue (Festuca arundinacea Schreb.) cover or maintained weed-free conditions. Both species established well under weed-free conditions but black locust survival and growth were severely reduced by herbaceous cover. After 5 years, herbaceous cover reduced mean stem volume 45% and 88% for loblolly pine and black locust, respectively, relative to weed-free conditions. When grown in mixture, both species had larger stem volume, and crown volume, relative to monocultures. Height to the lowest living branch decreased for both species as the proportion of pine decreased. In loblolly pine, live crown ratio increased and stem height:diameter ratio decreased as the proportion of pine decreased, indicating that intensity of competition for aboveground resources was directly related to the proportion of pine in these stands. Pine foliar N did not vary with stand type or herbaceous cover. The results of this study suggest that mixed stands of loblolly pine and black locust can be established from seedlings, provided herbaceous vegetation is controlled. If the present growth patterns continue, inter-cropping will result in the production of merchantable trees of both species earlier than in monoculture stands.

The influence of elevated carbon dioxide and water availability on herbaceous weed development and growth of transplanted loblolly pine (Pinus taeda)

Loblolly pine (Pinus taeda L.) seedlings were grown in competition with native weeds using soil and seed bank collected from recently chopped and burned areas near Appomattox, Virginia. One-year-old seedlings were planted and weeds allowed to germinate from the native seed bank while being exposed to CO(2) (ambient and elevated - approximately 700 ppm) and water (water stressed and well watered) treatments for approximately one growing season in a greenhouse. Elevated CO(2) did not influence total weed biomass; however, C(3) weed community development was favored over C(4) weed community development in elevated CO(2) regardless of water availability. This suggests that weed community composition may shift toward C(3) plants in a future elevated CO(2) atmosphere. Pine growth was significantly greater in the well watered and elevated CO(2) treatments compared to the water stressed and ambient treatments, respectively, even though they were competing with native herbaceous weeds for resources. There was a significant water and CO(2) interaction for pine root:shoot ratio. Under elevated CO(2), root:shoot ratio was significantly greater in the water stressed treatment than the well watered treatment. In contrast, there was no significant difference in the root:shoot ratio under the ambient CO(2) treatment for either water treatment. These results suggest that loblolly pine seedlings will respond favorably in an elevated CO(2) atmosphere, even under dry conditions and competing with herbaceous weeds.

Drainage effects on plant diversity and productivity in loblolly pine (Pinus taeda L.) plantations on wet flats

Abstract Silvicultural practices are under increased scrutiny with respect to environmental impacts and intensive forestry is often cited as a contributing factor in the decline of biodiversity. However, there are few studies which evaluate the long-term impact of forest operations on plant diversity and production. The objective of this project was to determine the rotation age effects of three site preparation methods on plant diversity and productivity in wet pine flat plantations. The study are consisted of three wetland sites in the coastal plain of Virginia. Treatments were originally established in 1969 to study the effects of site preparation on loblolly pine ( Pinus taeda ) growth. The three site preparation treatments applied were: chop and burn, bedding between windrows (windrow-bedding), and secondary ditching. This study was conducted in 1991 when stands were near rotation age (22 years). Plant diversity was lowest and total biomass highest on the windrow-bedding treatment. Windrow-bedding appeared to increase pine growth by providing seedlings with more available soil volume and by reducing the vegetative regeneration of hardwoods and shrubs, thereby decreasing diversity. Secondary ditching increased pine growth by lowering water table levels, but had little effect on plant diversity.

Long-term growth trends of red spruce and fraser fir at Mt. Rogers, Virginia and Mt. Mitchell, North Carolina

Cross-sectional area growth and height growth of Fraser fir and red spruce trees growing in Virginia and North Carolina were analyzed to identify possible long-term growth trends. Cross-sectional area growth provided no evidence of growth decline. The individual discs were classified according to parameter estimates of the growth trend equation. The predominant pattern of growth was a steady increase followed by fluctuation about a horizontal line. Other cross-sections exhibited a steady increase throughout the series. The only discs that represent declining growth patterns were from trees in subordinate crown position or which had previous top damage. No unexplained growth decline was present in any disc. The results regarding height growth were uncertain. A slight decline in height growth was present although we suggest that this observation was due to problems with the data or the model used to fit height growth. These findings contradict other studies suggesting that a recent growth decline has occurred in red spruce in the southern Appalachians.

Expected stand behavior: site quality estimation for southern Appalachian red spruce

An indicator of site productivity and quality was provided for mixed, uneven-aged natural stands of southern Appalachian red spruce (Picea rubens Sarg.). A set of anamorphic site index curves was developed and validated using the Meyer (1940) nonlinear function using diameter at breast height as a predicting variable. The coefficient of determination for the base curve was good (R2 = 0.626) and no consistent bias was detected. Average site quality index decreased with increasing elevation. Site index was highest in pure spruce stands but decreased with increasing elevation and/or increasing Fraser fir (Abies fraseri (Pursh) Poir.) or yellow birch (Betula lutea Michaux f.) component.

The effects of sulfometuron on the root growth of loblolly pine.

The effect of sulfometuron (Oust™) on the root growth of loblolly pine (Pinus taeda L.) seedlings was studied in the field and in two soil types in the greenhouse. In the greenhouse study sulfometuron was applied to the foliage only, the soil only, and to both foliage and soil at the rates of 0.10, 0.21, and 0.42 kg ai/ha. Twenty-eight days after application root growth significantly decreased for all methods of application and with increasing rates e.g., 0.10, 0.21, and 0.42 kg ai/ha sulfometuron reduced new root length by 42%, 53%, and 64%, respectively. Application in the field at the rate of 0.30 kg ai/ha resulted in a 68% reduction in root growth. However, by the end of the growing season treated seedling root and shoot biomass were 115% and 64% greater, respectively. To ensure earlier season survival the rate of sulfometuron applied should be kept at a minimum level that will allow both weed control and adequate root growth. Low rates would be particularly important during a dry planting season.