Kevin T. Smith

Aluminum-Induced Calcium Deficiency Syndrome in Declining Red Spruce

Prolonged suppression of cambial growth has apparently caused a decline in radial growth in many mature red spruce, Picea rubens. Surveys indicate that this decline occurs in trees throughout the natural range of red spruce and is independent of elevation, tree size, and age class. In addition, crowns of mature red spruce at high elevations across the northeastern United States have been dying back. Understanding the physiological basis for the growth decline is essential for the judicious management of the red spruce resource. A sequence of events is inferred through which an imbalance of aluminum and calcium in the fine root environment reduces the rate of wood formation, decreases the amount of functional sapwood and live crown, and leaves large trees more vulnerable to extant secondary diseases and insect pests.

Fire-scar formation and compartmentalization in oak

Fire scars result from the death of the vascular cambium resulting from excessive heating, which exposes sapwood to infection and initiates the wood decay process. In southeastern Ohio, prescribed fires in April 1995 and 1997 scarred Quercus prinus L. and Q. velutina Lam. Low-intensity fires scorched bark and produced scars, primarily on the downslope side of the stem. Eighteen scorched trees (4-23 cm at DBH) were dissected in November 1997, 14 of which had fire scars. The vascular cambium beneath natural bark fissures was most vulnerable to injury. No charred or scorched wood was associated with scars of trees exposed to single fires; wood exposed by scars from the 1995 fire was charred by the 1997 fire. Consistent with the compartmentalization process, discoloration and whiterot occurred within compartment boundaries of wood present at the time of wounding. Scars from the prescribed fires were consistent in size and shape with scars in nearby oak trees previously hypothesized to have been burned prior t...

Plasticity in Dendroclimatic Response across the Distribution Range of Aleppo Pine (Pinus halepensis)

We investigated the variability of the climate-growth relationship of Aleppo pine across its distribution range in the Mediterranean Basin. We constructed a network of tree-ring index chronologies from 63 sites across the region. Correlation function analysis identified the relationships of tree-ring index to climate factors for each site. We also estimated the dominant climatic gradients of the region using principal component analysis of monthly, seasonal, and annual mean temperature and total precipitation from 1,068 climatic gridpoints. Variation in ring width index was primarily related to precipitation and secondarily to temperature. However, we found that the dendroclimatic relationship depended on the position of the site along the climatic gradient. In the southern part of the distribution range, where temperature was generally higher and precipitation lower than the regional average, reduced growth was also associated with warm and dry conditions. In the northern part, where the average temperature was lower and the precipitation more abundant than the regional average, reduced growth was associated with cool conditions. Thus, our study highlights the substantial plasticity of Aleppo pine in response to different climatic conditions. These results do not resolve the source of response variability as being due to either genetic variation in provenance, to phenotypic plasticity, or a combination of factors. However, as current growth responses to inter-annual climate variability vary spatially across existing climate gradients, future climate-growth relationships will also likely be determined by differential adaptation and/or acclimation responses to spatial climatic variation. The contribution of local adaptation and/or phenotypic plasticity across populations to the persistence of species under global warming could be decisive for prediction of climate change impacts across populations. In this sense, a more complex forest dynamics modeling approach that includes the contribution of genetic variation and phenotypic plasticity can improve the reliability of the ecological inferences derived from the climate-growth relationships.

Dendroecological applications in air pollution and environmental chemistry: research needs

Summary During the past two decades, dendrochronology has evolved in new dimensions that have helped address both the extent and causes of impacts of regional scale environmental pollution on the productivity and function of forest ecosystems. Initial focus on the magnitude and timing of alterations of baseline growth levels of individual forest trees has now broadened to include characterization of the geographic extent of effects, their distribution among species, and their relationship to soils and biogeochemical cycles. Increasingly dendrochronology has benefitted from and contributed to improved understanding of the physiological and biogeochemical basis of air pollution effects on forest ecological processes. In addition, the need to consider levels and types of remedial action has raised concerns about the relative roles of anthropogenic and natural causative factors. The subdisciplines of dendroecology and dendrochemistry have evolved in response to those needs. Such applications have extended the field from its initial primary focus on historical growth and climatic reconstruction to an emerging role as an exploratory research tool with the potential to address basic questions about the roles of air pollution in modifying relationships between the amount, timing, distribution, and quality of tree growth and biogeochemical and atmospheric processes. In this paper we focus on two regional scale air quality issues, acidic deposition and tropospheric ozone, as stressors. We evaluate past success, current limitations, and future potential of dendrochronology as an investigative tool for both quantifying and understanding the effects of these stressors on forests. Important issues related to the use of dendrochemistry to evaluate effects of acidic deposition include the role of natural vs anthropogenic processes in cation mobilization in soils; biological and geochemical significance of increases in potentially phytotoxic metals and depletion of essential base cations in stem wood; and quantitative vs qualitative interpretation of patterns of element changes in wood related to metal mobility and species differences in accumulation. Shifts in root growth, function, and distribution and increased sensitivity of tree growth to temperature stress are important indicators that cation depletion can alter forest function and the dendroclimatic signal. Critical challenges in evaluating forest responses to ozone, include defining the relative roles of episodic and chronic exposures in seasonal and annual growth cycles, and the quantifying impacts of ozone on the water relations of trees and stands. Here high-resolution measures of diurnal growth and water use patterns have the potential to identify critical features of both pollutant exposure and plant response. These insights should enhance our analytical capabilities in examining annual-scale measures of growth and provide needed understanding of changes in relationships of growth to climate. We conclude that dendrochronology, when coupled with mechanistic understanding of underlying ecological processes influencing growth, has been, and will continue to be, a valuable monitoring and investigative tool for exploring relationships between trees and their growing environment. We expect this role to become even more important in the future as better ways are sought to evaluate and predict forest growth and function in a changing global environment.

Conservation of element concentration in xylem sap of red spruce

Abstract. We investigated the chemistry of xylem sap as a marker of red spruce metabolism and soil chemistry at three locations in northern New England. A Scholander pressure chamber was used to extract xylem sap from roots and branches cut from mature trees in early June and September. Root sap contained significantly greater concentrations of K, Ca, Mg, Mn, and Al than branch sap. Sap collected in June contained a signficantly greater concentration of Mn than sap collected in September. Sap concentration was related to forest location for N and Mn. Variations in concentrations of N and K were significantly related to the interaction of tree organ and month of collection. Variations in concentrations of P, Cu, Zn, and Fe were not attributable to tree organ, month of collection, or forest location. Patterns of element concentration in xylem sap compared to previously published data on soil solution chemistry indicated a high degree of homeostatic control of xylem sap chemistry. This control likely represents a significant allocation of resources within the tree energy budget.

Applied Dendroecology and Environmental Forensics. Characterizing and Age Dating Environmental Releases: Fundamentals and Case Studies

Dendroecology, or the use of ring patterns to assess the age of trees and environmental factors controlling their growth, is a well-developed method in climatologic studies. This method holds great potential as a forensic tool for age dating, contamination assessment, and characterization of releases. Moreover, the method is independent of the physical presence of contamination at the time of sampling because it is focused on the effect rather than the cause. This review is one of the very few articles published to date exploring the forensic applicability of dendroecology. This article is organized in two parts: Part I describes the method principles and proposes a practical procedure for forensic applications; Part II exemplifies and validates the method through six case studies of successful forensic application (related to petroleum products and chlorinated solvent spills).

Decay Column Boundary Layer Formation in Maple

The wounding of sapwood in living trees results in a cascade of processes, including the formation of wound-initiated discoloration (Shigo, 1965). In three dimensions, this discoloration appears in the form of columns parallel to the stem axis with ragged, conical ends. All published reports indicate that in living trees, decayed wood only occurs in tissue that has undergone wound-initiated discoloration. The visible degree of discoloration and other features following wounding vary from one tree species to another. The size of wounds capable of inducing the decay process range from very small branch and root stubs to the mechanical breakage of main stems of adult trees.

Changes in tracheid and ray traits in fire scars of North American conifers and their ecophysiological implications

BACKGROUND AND AIMS Fire scars have been widely used as proxies for the reconstruction of fire history; however, little is known about the impact of fire injury on wood anatomy. This study investigates changes in tracheid and ray traits in fire scars of Douglas fir (Pseudotsuga menziesii), western larch (Larix occidentalis) and ponderosa pine (Pinus ponderosa), and discusses their ecophysiological implications for tree recovery from fire. METHODS Transverse and tangential microsections were prepared for light microscopy and image analysis. Measurements of tracheids and rays were made in the three spatial dimensions: axially (at different section heights), radially (in different rings) and tangentially (with increasing distance from the wound margin). KEY RESULTS Changes were strongest in the first year after fire injury, with a decrease in tracheid size (by 25-30 %) and an increase in tracheid density (by 21-53 %) for the three species. In addition, an increase in ray size (by 5-27 %) and an increase in ray density (by 19-36 %) were found in P. menziesii and L. occidentalis. Changes were comparable along the fire-injured stem and were often most marked close to the fire scar. CONCLUSIONS The differentiation after fire injury of narrower and more numerous tracheids expresses a trade-off between hydraulic safety and hydraulic efficiency, while that of larger and more numerous rays serves compartmentalization and wound closure, mechanical strength and defence responses. Pinus ponderosa does not generally produce more ray tissue after fire injury and thus appears to be more adapted to fire.

Tree Survival and Growth Following Ice Storm Injury

Nearly 25 million acres of forest from northwestern New York and southern Quebec to the south-central Maine coast were coated with ice from a 3-day storm in early January 1998. This storm was unusual in its size and the duration of icing. Trees throughout the region were injured as branches and stems broke and forks split under the weight of the ice. These injuries reduced the size of tree crowns and exposed wood to infection that can lead to wood decay.In addition to regional assessments, forest managers need to know how much damage to expect in the years following the storm due to loss of wood quality, loss of tree growth, or tree death. The purpose of this study was to determine tree survival, stem growth, and response to infection following injury to major hardwood tree species from the 1998 ice storm.

Development of wood decay in wound-initiated discolored wood of eastern red cedar.

Abstract Logs of eastern red cedar, Juniperus virginiana L., with well-developed bands of light-colored wood (“included sapwood”) within heartwood can be unsuitable for sawn wood products. This finding is in contrast to published information that the “included sapwood” is (1) a heartwood anomaly rather than sapwood and (2) its occurrence is not a reason to exclude this type of wood from commercial use. The alternative view presented here is that “included sapwood” is wound-initiated discolored wood which is the starting point for wood decay in living trees and which has adversely altered wood properties before the development of decay symptoms. Our study of the patterns of discoloration and decay, electrical resistance properties, elemental analysis, wood acidity, solubility in dilute NaOH, total phenol content, and tests of wood decay resistance indicated that the so-called included sapwood was discolored wood. This light-colored discolored wood had no greater decay resistance than sapwood, a common finding in other tree species in which “included sapwood” is found. Half the sample disks sent to our laboratory had symptomatic decay within the bands of light-colored discolored wood bounded by a phenol-enriched protective layer on the bark side and phenol-enriched heartwood on the pith side of the band. This ring-rot, even in its pre-symptomatic stage, can cause problems during processing for sawn wood products. Therefore, logs with well-developed bands of light-colored discolored wood should be considered high-risk material for some products, although they could be useful for others.