Geology topics
J. L. Chambers
Publications and source records attributed to J. L. Chambers.
Towards sustainable management of Louisiana's coastal wetland forests: Problems, constraints, and a new beginning
Over 345,000 ha of forested swamps occur throughout the Mississippi River Deltaic Plain. Natural and anthropogenic changes in hydrology and geomorphology at local and landscape levels have reduced the productivity in many of these coastal wetland forests areas and have caused the complete loss of forest cover in some places. A summary and interpretation of the available science, suggestions for policy change, and a multidisciplinary (multi-responsibility) approach were needed to address these issues [in the context of private land]. In response, the Louisiana Governor's office formed a Coastal Wetland Forest Conservation and Use Science Working Group (SWG) and an associated Advisory Panel to provide the Governor with information and suggestions of strategies for environmental and economic utilization, conservation, and protection of Louisiana's coastal wetland forest ecosystem in the long-term. The process of engaging scientists, resource managers, and other stakeholders in this effort is described, and the recommendations of the SWG are presented relative to forestry practices and the potential for sustainable management of coastal wetland forests.
Ecological consequences of changing hydrological conditions in wetland forests of coastal Louisiana
Large-scale and localized alterations of processes affecting deltaic coastal wetlands have caused the complete loss of some coastal wetland forests and reduced the productivity and vigor of many areas in coastal Louisiana. This loss and degradation threatens ecosystem functions and the services they provide. This paper summarizes ecological relationships controlled by hydrological processes in coastal wetland forests of the Mississippi River delta and presents two case studies that illustrate the complexity of assessing hydrological control on swamp forest establishment and growth. Productivity of overstory trees has been affected by these changes, but the first case study illustrates that the relationship between flooding and growth may be site-specific. An important effect of increased flooding has been to reduce regeneration of swamp forest trees. The second case study is an outline of the kind of hydrological analysis required to assess probability of regeneration success.
Effects of salinity on baldcypress seedlings: Physiological responses and their relation to salinity tolerance
Growth and physiological responses of 15 open-pollinated families of baldcypress ( Taxodium distichum var. distichum ) subjected to flooding with saline water were evaluated in this study. Ten of the families were from coastal sites in Louisiana and Alabama, USA that have elevated levels of soil-water salinity. The other five families were from inland, freshwater sites in Louisiana. Seedlings from all families tolerated flooding with water of low (2 g 1 −1 ) salinity. Differences in biomass among families became most apparent at the highest salinity levels (6 and 8 g 1 −1 ). Overall, increasing salinity reduced leaf biomass more than root biomass, which in turn was reduced more than stem biomass. A subset of seedlings from the main greenhouse experiment was periodically placed indoors under artificial light, and measurements were made of gas exchange and leaf water potential. Also, tissue concentrations of Cl − , Na + , K + , and Ca 2+ were determined at the end of the greenhouse experiment. Significant intraspecific variation was found for nearly all the physiological parameters evaluated, but only leaf concentrations of Na + and Cl − were correlated with an index of family-level differences in salt tolerance.
Interaction of flooding and salinity stress on baldcypress ( Taxodium distichum )
Coastal wetlands of the southeastern United States are threatened by increases in flooding and salinity as a result of both natural processes and man-induced hydrologic alterations. Furthermore, global climate change scenarios suggest that, as a consequence of rising sea levels, much larger areas of coastal wetlands may be affected by flooding and salinity in the next 50 to 100 years. In this paper, we review studies designed to improve our ability to predict and ameliorate the impacts of increased flooding and salinity stress on baldcypress ( Taxodium distichum (L.) Rich.), which is a dominant species of many coastal forested wetlands. Specifically, we review studies on species-level responses to flooding and salinity stress, alone and in combination, we summarize two studies on intraspecific variation in response to flooding and salinity stress, we analyze the physiological mechanisms thought to be responsible for the interaction between flooding and salinity stress, and we discuss the implications for coastal wetland loss and the prospects for developing salt-tolerant lines of baldcypress.
Prospects for increasing the salt tolerance of forest trees: A review
Three major themes related to the improvement of salt tolerance in forest tree species are examined. First, evidence demonstrating that substantial intraspecific variation in salt tolerance exists in many species is presented. This evidence is important because it suggests that efforts to improve salt tolerance through conventional plant breeding techniques are justified. Second, the physiological and genetic mechanisms controlling salt tolerance are discussed briefly. Although salt tolerance involves the integration of numerous physiological processes, there is considerable evidence that differences in the ability to exclude Na + and Cl - from leaves are the most important factors underlying intraspecific differences in tolerance . It is also becoming apparent that, although salt tolerance is a multigenic trait, major genes play an important role. Third, progress to date in improving salt tolerance of forest tree species is assessed. Compared with agricultural crops, relatively little progress has been made with either conventional or biotechnological methods, but field trials designed to test clones identified as salt tolerant in screening trials are underway now in several countries. We conclude that there is justification for cautious optimism about the prospects for improving salt tolerance in forest tree species. © 1994 Heron Publishing.