John D. Hodges

Development and ecology of bottomland hardwood sites

Abstract A basic knowledge of the origin, development, and ecology of bottomland hardwood sites is important for assessing harvesting impacts on those sites. This paper presents an overview of the geologic origin and development of hardwood sites, species-site relationships and the natural patterns of ecological succession on those sites, and the implications of that information for forest management. Bottomland hardwoods occur on floodplain sites primarily in the Atlantic and Gulf Coastal Plains. Past geologic events led to the formation of broad stream valleys in those areas because of the erodible, sedimentary geologic materials. Natural patterns of ecological succession on floodplain sites are influenced by autogenic and allogenic processes in that the sites may undergo constant change because of deposition. Three natural patterns of succession are recognized for floodplain sites of major river bottoms—those occurring on permanently flooded sites, those on low elevation wet sites, and those on higher elevation, better drained sites. Floristic composition and successional patterns are strongly influenced by the hydrologic events on the sites and particularly by rates and types of deposition.

Growth and biomass distribution of cherrybark oak (Quercus pagoda Raf.) seedlings as influenced by light availability

Cherrybark oak (Quercus pagoda Raf.) seedlings were established and raised in the field under four light levels (100%, 53%, 27% or 8% of full sunlight) to study the effects of light availability on their shoot growth, biomass accumulation, and biomass distribution. After two growing seasons, greatest stem growth was observed on seedlings which received intermediate light levels, and this growth was associated to a greater accumulation of total seedling biomass and a distribution pattern which balanced accumulation of root and shoot biomass. In contrast, less biomass accumulation and a biomass distribution pattern that favored root growth over stem growth were characteristic of seedlings receiving full sunlight. These results suggest that regeneration of cherrybark oak on mesic sites may be limited by preferential root growth, but reproduction of this species may be amenable to silvicultural practices that improve the light environment through stand manipulation.

Seasonal cambial growth and development of loblolly pine: Xylem formation, inner bark chemistry, resin ducts, and resin flow

Abstract Cambial activity of loblolly pine in central Louisiana under mild soilwater deficit lasted for 252 days, one-third of which was used in the formation of early-wood. Although more cells formed in the late-wood, the radial increments for both were statistically similar (1750 μm). Vertical resin duct formation started 12 weeks after cambial reactivation with the first duct in each tree, except two, forming at the early-wood. Resin flow, an important factor in pine resistance to bark beetle attack, was moderately correlated with vertical duct density, growth variables, and all measured environmental variables with total soilwater storage, cumulative water deficit, and maximum air temperature combined accounting for 73% of the variation. Levels of starch continuously declined from May to December, while total sugar fluctuated with no seasonal pattern. Amino nitrogen and total nitrogen changed seasonally with peak concentrations coinciding with cell initiation and active growth, leaf fall, and winter cold temperatures. Seasonal change in resin flow was associated with changes in physiology related to ontogeny as well as environment. Knowledge of such relationships improves the basis for future study of pine/bark beetle interactions.

Role of Oleoresin Flow in Initial Colonization of Loblolly Pine by Southern Pine Beetle (Coleoptera: Scolytidae)

The influence of total resin flow in loblolly pine, Pinus taeda L., on initial colonization by the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae), was investigated. Resin flow of trees was manipulated mechanically so that it followed the same pattern of decrease and near cessation as seen in trees successfully attacked by southern pine beetle. There were also intermediate treatments where resin flow was allowed to recover after near cessation. Beetles were introduced by means of mesh cages attached to the mid-bole of trees and left until the end of the longest wounding treatment. In trees where resin flow was reduced, significant increases in number of attacks, total gallery length, and length of gallery free of resin occurred.

Carbon allocation and morphology of cherrybark oak seedlings and sprouts under three light regimes

Abstract• Continued problems in regenerating oak forests has led to a need for more basic information on oak seedling biology.• In the present study, carbon allocation and morphology were compared between cherrybark oak (Quercus pagoda Raf.) seedlings and sprouts at 1-Lag grown in full, 47%, and 20% sunlight.• Results indicated that cherrybark oak seedling carbon allocation and morphology responded plastically to light availability. In full light, roots were sinks for 14C, while shoots were sinks for 14C under reduced light availability. Cherrybark oak sprouts exhibited similar carbon allocation patterns in response to light availability, but displayed stronger shoot sinks than seedlings when grown underreduced light availability. We also showed that young oak sprout roots are a sink for 14C-photosynthates.• Results from this study point to the need for a morphological index for oak sprout development so more precise comparisons in sprout development and physiology can be made with seedlings.Résumé• Des problèmes continus pour la régénération des forêts de chêne ont conduit à un besoin de plus d’informations de base sur la biologie des semis de chêne.• Dans la présente étude, l’allocation de carbone et la morphologie ont été comparées entre des semis de Quercus pagoda Raf. et des rejets au stade de développement 1Lag cultivés en pleine lumière, à 47 % et à 20 % de lumière.• Les résultats ont indiqué que l’allocation de carbone et la morphologie des semis de chêne ont répondu plastiquement à la disponibilité en lumière. En pleine lumière, les racines ont été des puits pour 14C, tandis que les pousses ont été des puits pour 14C sous une disponibilité réduite de la lumière. Les rejets ont montré des modes d’allocation de carbone similaires en réponse à la disponibilité en lumière, mais ont montré des puits plus importants que les jeunes plants quand ils ont été cultivés sous un éclairement réduit. Nous avons également montré que les jeunes chênes pousses des racines sont un puits pour photosynthats 14C.• Les résultats de cette étude soulignent le besoin d’un indice morphologique de développement des rejets de chêne de manière à pouvoir faire des comparaisons plus précises en ce qui concerne le développement des rejets et leur physiologie par rapport aux jeunes plants.

Influence of Resin Duct Size and Number on Oleoresin Flow in the Southern Pines

The number of radial resin ducts was significantly higher in slash pines than in loblolly, longleaf, or shortleaf. Average width of resin ducts was less in shortleaf than in the other three species. Flow rate of oleoresin was not correlated with size or number of resin ducts for any of the four species. Additional keywords: Pinus echinata, Pinus elliottii, Pinus palustris, Pinus taeda, Dendroctonus frontalis.

Obtaining Adequate Light for Planted Bottomland Oak (Quercus spp.) Seedlings: A Case Study Utilizing Midstory Control

Bottomland hardwood forests of the United States have drastically declined since European settlement. Although much of the reported loss has resulted from conversion to agriculture and urban development, thousands of additional hectares have been degraded due to selective harvesting and a lack of effort to establish desirable regeneration prior to harvesting. Research has indicated that seedlings of some oak species perform best with intermediate levels of light, while performing less desirably at both high and low levels. This study demonstrates that controlling undesirable midstory trees through herbicide injection alone can be sufficient to create suitable light conditions for oak regeneration in some circumstances. We were able to increase the average percentage of total available light to 31.5% (SE = 0.029) as compared to only 14.2% (SE = 0.011) in untreated areas (F1,33 = 46.57, p < .0001). Additionally, oak seedlings planted in areas receiving midstory control exhibited good to excellent survival compared to results of other relevant studies. The present case study supports the belief that performance of oak seedlings can be increased by establishing appropriate light conditions.

Biotic Agents of Stress in the South

Biotic agents affect millions of hectares of forests throughout the world each year. Of all the environmental stresses affecting trees, insects and diseases are by far the most widespread and most studied but, perhaps, the least understood. Their influence on forest productivity may be relatively small, as during low-level infestations that produce nagging drains on growth, or catastrophic, as during epidemic outbreaks that may destroy thousands of hectares in a short period of time. In contrast to air pollutants, whose effects are primarily regional in nature, biotic pests permeate nearly every forest in all parts of the world and constantly pose a threat to the health of these ecosystems. Biotic pests commonly interact with other agents of stress, both natural and anthropogenic, to produce complex problems for forest managers throughout the world. These complex interactions between biotic pests and other agents of stress are beyond the scope of this chapter and are discussed elsewhere in this book (Chapter 7). This chapter addresses the relationships between susceptible hosts and the major biotic pests in the southern United States.

Forest Pests: Influence of Forest Management Practices on Pest Population Dynamics and Forest Productivity

Considerable interest now exists in understanding how the host tree, pest population, associated microorganisms, and the environment interact to determine if a pest outbreak will occur. However, most research in the past has focused on individual components which determine pest outbreaks. To address management of “pest” stress it will be essential that we develop a better understanding of the repertoire of host defenses, and how genetics and environment interact to control expression of these defense mechanisms. The objective of this chapter will be to (1) bring together information gained through several studies which have attempted to elucidate the interrelationships between host, pathogens, etc. and (2) illustrate how this information can be incorporated into a forest management program to lessen the stress on the residual forest and decrease the susceptibility to pest attack.