Brian Roy Lockhart

Bottomland Forests in the Lower Mississippi Alluvial Valley Associated with the Endangered Lindera melissifolia

Abstract Forest canopy and subcanopy data were collected from and compared among five disjunct bottomland hardwood forests in the Lower Mississippi Alluvial Valley, each with known occurrence of a population of the federally endangered shrub Lindera melissifolia. All study sites are cut-over forests, underlain by hydric soils, and have a seasonal high water table. Canopy and subcanopy species are similar among sites, but species differ in relative importance, and flood tolerant tree species exceed that of flood intolerant species. Distribution of L. melissifolia colonies within each study site was not associated with mean tree density or d.b.h. Forest composition and structure at each study site reflect hydrologic regime, topography, historical disturbance, and an absence of recent disturbance. Results of this study provide a quantitative description of bottomland forests that currently sustain L. melissifolia populations. This information may be utilized for development of forest management plans aimed at ensuring continued sustainability of existing L. melissifolia populations and assessing other bottomland hardwood forests for potential reintroduction of this endangered species.

Flooding Facility Helps Scientists Examine the Ecophysiology of Floodplain Species Used in Bottomland Hardwood Restorations

Bottomland hardwood ecosystems, important for their unique functions and values, have experienced considerable degradation since European settlement through deforestation, development, and drainage. Currently, considerable effort is underway to restore ecological functions on degraded bottomland sites. Restoration requires a better understanding of the biological components, especially plants, and their interactions with other biotic and abiotic components of the ecosystem. Previous experimental approaches have focused on the effects of stress on floodplain plant species in controlled, small-scale studies or large, uncontrolled ecosystem-scale studies. We describe a facility, named the Flooding Research Facility (FRF), where hydrologic regimes can be manipulated to study ecophysiology of floodplain species. Key features of the FRF include the ability to establish experiments on a scale larger than would be possible in a greenhouse, but small enough to control key abiotic variables, such as flood frequency, duration, and light availability on native bottomland soil. Design of the FRF allows for random and replicated treatment applications. Additionally, we provide an example of ongoing research on the effects of flooding and light availability on pondberry (Lindera melissifolia), a federally endangered shrub found in the southeastern United States.

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.

Tree Species Composition and Structure in an Old Bottomland Hardwood Forest in South-Central Arkansas

Abstract Tree species composition and structure was determined for an old bottomland hardwood forest located in the Moro Creek Bottoms Natural Area in south-central Arkansas. Diversity for this forest was high with species richness ranging from 33 for the overstory and sapling strata to 26 for the seedling stratum and Shannon-Weiner values of 2.54 to 1.02 for the overstory and seedling strata. Sweetgum (Liquidambar styraciflua L.) and oaks (Quercus spp.) dominated the overstory stratum with 66 percent of the importance values. American hornbeam (Carpinus caroliniana Walter) dominated the midstory and sapling strata with 32 and 42 percent of the importance values. Despite the large tree sizes and ages of several trees, comparison of the forest with models of bottomland hardwood succession and eastern United States old-growth definitions indicate the forest can best be described as old pioneer in transition to changing old growth.