Nekton Use of Flooded Salt Marsh and an Assessment of Intertidal Creek Pools as Low-Tide Refuges

Patterns of nekton occurrence on the salt marsh surface at high tide and in an adjacent intertidal creek pool at low tide were used to investigate movements of nekton in an intertidal basin. Paired collections were made in North Inlet estuary, SC on 67 dates over 9 years. Comparisons of high- and low-tide total abundance indicated that what remained in the creek pool at low tide was representative of the nekton on the flooded marsh. Of the 64 taxa collected, the same 8 species ranked in the top 10 in both the high- and low-tide collections. Abundances of most resident species were positively correlated with the area of marsh flooded, but mummichog (Fundulus heteroclitus), the most abundant resident, was not. Abundances of young-of-the-year transient species were not related to the extent of tidal flooding. Some transient species used the flooded marsh but did not occupy the pool at low tide, and others found in the pool did not use the marsh. Differences in abundance, biomass, and length between the marsh and pool collections indicated differences in the tendency of species and life stages to retreat downstream of the pool to the subtidal channel. Proportionately more of the nekton that were present on the flooded marsh left the intertidal basin when large changes in temperature and salinity occurred between high and low tides. More transients left the basin following higher tides, but more residents did not. The results demonstrate a wide range of taxonomic and ontogenetic patterns among nekton using intertidal salt marsh basins and the underappreciated importance of intertidal creek pools as alternative low-tide refuges.     

Stress dependence of recrystallized-grain and subgrain size in olivine

New experiments on Mt. Burnet dunite have been carried out to evaluate the effects of important physical parameters on recrystallized-grain size and subgrain size in olivine deforming under steady-state conditions. The experiments, done under both wet and dry conditions in a Griggs solid-pressure-medium apparatus, were conducted in constant strain rate, constant stress and stress relaxation modes at 10 kbar confining pressure, temperatures from 1000°C to 1300°C, strain rates from 10⁻⁴ to 10⁻⁸/sec and stress differences of from 0.5 to 10 kbar. For dunite deformed under wet conditions, recrystallized-grain size is slightly temperature-dependent but under dry conditions it is only stress-dependent with D = 137 σ^−1.27 for D in μm and σ in kbar. Subgrain sizes also depend only on stress; for the dry experiments d = 28 σ^−0.62 and for the wet ones d = 15 σ^−0.69. Subgrain sizes decrease with increasing stress but do not increase with decreasing stress and hence record only maximum stress levels. Recrystallized-grain sizes adjust to both increasing and decreasing stress levels, at minimal strains and times, and thus record the stress history. Because of this and of the inherent stability of recrystallized grains, this technique is regarded as more reliable than the subgrain size and free dislocation density and curvature methods for estimating stress magnitudes in tectonites having deformed in the steadystate.     

Sediment transport analysis as a component of coastal management— a UK example

Detrimental effects of engineering works on the coast and a wish to conserve parts of the coastline have increased realization among coastal managers of the need to examine shoreline problems and proposals for protection in a wider spatial context than the site itself and over a longer time scale than the past few years. This paper outlines the approach taken in one region of the United Kingdom, the central south coast of England, to provide that wider perspective. Authorities responsible for coastal protection and sea defenses formed a coastal group, which, among other activities, commissioned research aimed at providing a greater understanding on which to base shoreline management decisions. A major project undertaken was a sediment transport study in which all existing information relating to coastal sediment processes in the region was collated and analyzed. All inputs, flows, and outputs of sediment were documented. Links between processes were examined for each part of the region. Finally, nine littoral cells of sediment circulation were identified and were suggested as forming a framework for shoreline management. The methods of compilation and analysis are outlined here and are exemplified for one area in the region. The approach is recommended as a cost-effective basis for strategic management of the coast in developed regions.     

Estimation of tree water stress from stem and soil water monitoring with time‐domain reflectometry in two small forested basins in Spain

Soil‐tree water relationships were studied using time domain reflectometry (TDR) in two small forested basins in Spain. The stem water content of two Mediterranean Quercus species (Quercus pyrenaica and Quercus rotundifolia) was measured using previously constructed species‐specific equations. To monitor soil moisture, a TDR station network was used in both cases. Sixteen Q. pyrenaica and six Q. rotundifolia individuals were selected to install two TDR probes in their trunks (at 20 and 120 cm above the ground) to monitor stem water content. Stem and soil water contents were measured fortnightly. The stem water content of both species showed a similar temporal trend for the period studied. A spring maximum (0·654 cm³ cm^?3 for Q. pyrenaica and 0·568 cm³ cm^?3 for Q. rotundifolia) was found to be associated with high transpiration and no soil moisture deficit, and a late‐summer minimum (0·520 cm³ cm^?3 for Q. pyrenaica and 0·426 cm³ cm^?3 for Q. rotundifolia) was associated with the end of the dry season. This drop in stem water content occurs when the available water in the soil decreases. This seasonal difference presumably reflects water withdrawn from stem storage to support the transpirational demands of the tree. Since plant water stress results in reduced stem water content and since this drop can be measured by TDR, it may be concluded that this technology offers a suitable tool for detecting plant water stress. Copyright © 2007 John Wiley & Sons, Ltd.     

Assessing impacts of climate change on forests: The state of biological modeling

Models that address the impacts of climate change on forests are reviewed at four levels of biological organization: global, regional or landscape, community, and tree. The models are compared for their ability to assess changes in fluxes of biogenic greenhouse gases, land use, patterns of forest type or species composition, forest resource productivity, forest health, biodiversity, and wildlife habitat. No one model can address all of these impacts, but landscape transition models and regional vegetation and land-use models have been used to consider more impacts than the other models. The development of landscape vegetation dynamics models of functional groups is suggested as a means to integrate the theory of both landscape ecology and individual tree responses to climate change. Risk assessment methodologies can be adapted to deal with the impacts of climate change at various spatial and temporal scales. Four areas of research needing additional effort are identified: (1) linking socioeconomic and ecologic models; (2) interfacing forest models at different scales; (3) obtaining data on susceptibility of trees and forest to changes in climate and disturbance regimes; and (4) relating information from different scales.The U.S. Government right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.Managed by Martin Marietta Energy Systems, Inc., for the U.S. Department of Energy under contract DE-AC05-84OR21400.