Darrin L. Rubino

Comparative analysis of dendroecological methods used to assess disturbance events

Summary The use of dendroecological methods to identify and describe disturbance histories has become quite common, and numerous techniques have been developed. These methods simultaneously use accurately dated and measured tree rings and objective criteria to identify release events; i. e., sustained increases in radial growth. The goals of this investigation were to perform a literature review to identify the various methods used to identify release events, critically compare the methods, and use an appropriate method to describe the disturbance history of a mixed mesophytic old-growth forest of Ohio, U. S. A. Application of 30 different methods resulted in substantial differentes in the number of disturbance events and the disturbance return interval. Analysis of individual growth segments revealed a large portion to be non-normally distributed. Furthermore, non-normality was especially high during identified disturbance events. We subsequently modified an existing disturbance identification method by changing the measure of central tendency from the mean to the median growth rate since medians are more robust estimators of central tendency than means. Application of this running median method (> 25 or 50 % increase in radial growth when medians of adjacent 10-yr growth segments are compared) to tree-ring series obtained from the study site led to the identification of numerous synchronous and asynchronous radial-growth increases among the individual tress. Based an the observed release patterns, we hypothesize that the disturbance regime of the old-growth stand is best categorized by gap-phase dynamics.

Evaluation of coarse woody debris and forest vegetation across topographic gradients in a southern Ohio forest

In highly dissected landscapes, topographic gradients and their associated microhabitat conditions have been shown to greatly influence the distribution of woody vegetation. However, little is known about the influence of these gradients on the spatial distribution of coarse woody debris (CWD), especially in unglaciated eastern North America. The main goal of this study was to examine the influence of topography (slope aspect, percent slope, and slope position as calculated from a landform index (LI)) and plot characteristics (tree height, age, and canopy cover) on the distribution of trees (diameter at breast height, dbh≥10 cm), saplings (dbh<10 cm), and CWD in a mixed-oak forest of unglaciated southern Ohio (USA). CWD was defined in this study as any downed bole or limb with a diameter≥10 cm over a length≥0.5 m. Redundancy analysis (RDA) of the three structural layers revealed that the measured parameters explained a significant (P<0.05) percentage of the variation in individual species distributions. In all three structural layers, slope aspect and LI were consistently important in explaining individual taxa distributions. Total CWD density (pieces ha−1) was significantly (P<0.05) correlated with LI (r=0.299) and percent slope (r=−0.433). Total tree density was significantly negatively correlated with slope position (r=−0.469), slope aspect (r=−0.328), and canopy cover (r=−0.391), and total sapling density was significantly negatively correlated with height of the dominant tree in each plot (r=−0.283). According to an analysis of similarities between the three structural layers, species assemblages were significantly (P<0.05) different between all three layers. The tree and CWD strata showed the highest similarity (rho, R=0.216) while the CWD and sapling layers showed the lowest (R=0.762). Oak (Quercus spp.) dominated the tree and CWD layers while mesophytic species (maple (Acer spp.) and beech (Fagus grandifolia)) dominated the sapling layer. Analyses of CWD distributions in relation to both living vegetation and topographic gradients suggest that a complex interplay of factors dictate the distribution of CWD loads across the landscape. Differences in distributions were observed for total and individual CWD taxa. Given its importance in forested ecosystems, a better understanding of CWD spatial distribution is necessary if CWD dynamics and function (habitat and nutrient cycling) are to be fully understood.

Presence of aposematic (warning) coloration in vascular plants of southeastern Ohio

RUBINO, D. L. AND B. C. MCCARTHY (Department of Environmental and Plant Biology, Ohio University, Athens, OH 45701). Presence of aposematic (warning) coloration in vascular plants of southeastern Ohio. J. Torrey Bot. Soc. 131: 252-256. 2004.-Aposematic coloration, use of conspicuous colors to advertise unpleasant qualities to potential predators, is well documented in the animal kingdom. However, similar use of warning coloration in plants to advertise physical armaments (spines, thorns, or prickles) has been, until recently, unreported. A preliminary survey of physically armed plants in southeastern Ohio (USA) revealed a high incidence of aposematic coloration-the presence of physical armaments colored differently than the structure on which they are borne. Furthermore, aposematic coloration was found in a wide variety of taxonomically diverse vascular plants. Future research into the possible role of aposematic coloration in vascular plants could greatly expand our knowledge of plant/herbivore interactions.

Herbaceous layer contrast and alien plant occurrence in utility corridors and riparian forests of the Allegheny High Plateau

communities by alien plant species that can adversely affect community structure and function. To determine how corridor establishment influences riparian vegetation of the Allegheny High Plateau of northwestern Pennsylvania, we compared the species composition and richness of the herbaceous layer (all vascular plants s 1 m tall) of utility corridors and adjacent headwater riparian forests, and tested the hypothesis that utility corridors serve as foci for the invasion of adjacent riparian forest by alien vascular plants. We contrasted plant species richness and vegetative cover, cover by growth form, species richness and cover of alien plants and cover of microhabitat components (open soil, rock, leaf litter, log, bryophyte) in utility corridors and adjacent riparian forest at 17 sites. Cluster analysis revealed that herbaceous layer species assemblages in corridors and riparian forest were compositionally distinct. Herbaceous layer cover and species richness were significantly (P s 0.05) greater in corridors than in riparian forest. Fern, graminoid, and forb species co-dominated herbaceous layer cover in corridors; fern cover dominated riparian forests. Cover of alien plants was significantly greater in corridors than in riparian forest. Alien plant species richness and cover were significantly and positively correlated with open soil, floodplain width, and active channel width in corridors but were significantly and negatively correlated with litter cover in riparian forest. Given that the majority of alien plant species we found in corridors were shade-intolerant and absent from riparian forests, we conclude that open utility corridors primarily serve as habitat refugia, rather than as invasion foci, for alien plant species in riparian forests of the Allegheny High Plateau.

Dendro-archeo-ecology in North America and Europe: Re-purposing Historical Materials to Study Ancient Human-Environment Interactions

The unique position of dendrochronology at the nexus of archeology, ecology, and climatology allows it to play a pivotal role in the study of past human-environment interactions. Yet, few tree-ring studies in Europe and eastern North America have been used to study pre-industrial land-use changes, forest ecology, and carbon dynamics and thus to constrain the uncertainties surrounding the Early Anthropocene hypothesis (Ruddiman Clim Chang 61:261–293, 2003; Rev Geophys 45(4):RG4001, 2007). Here, we discuss the potential of dendro-archeo-ecology—the use of dendroarcheological material in the study of forest ecology—to document past human land-use and forest alteration, which started in the Neolithic Era (∼12,000–4000 BP) in Europe and after European immigration into eastern North America in the 1620s. In this context, we focus on the dendro-archeo-ecology of (1) Neolithic pile dwellings in the Euro-Mediterranean region and (2) old-growth forest dynamics in eastern North America. We discuss recurring challenges (e.g., low sample depth, short series length) and uncertainties (e.g., species and tree size bias) related to the use of (pre)historic timbers for ecological purposes that need to be carefully addressed. We advocate for a concerted effort to move the use of dendro-archeological material from strictly archeological applications towards exploration of its ecological potential and for a close alliance of dendrochronology with related disciplines that aim to address the same subjects.

DENDROPEDAGOGY: Teaching Botany, Ecology & Statistical Principles Through Tree-Ring Studies

When we meet people in the woods, we are often asked if it is true that one can tell the age of a tree by counting its rings. We tell them that not only can age be determined but also that a glimpse at the trees history can be found in the rings. In temperate regions, trees deposit a single layer of wood around their circumference every year. Dendrochronology (dendron = tree; chronos = time; logos = the study of) is the science that uses tree rings, dated to their exact year of formation, to analyze temporal and spatial patterns of various processes (e.g., biological, physical, or cultural). The width of a tree ring in a given year represents the radial-growth response of the tree to prevailing environmental conditions. The width of a tree ring can be determined by noting the pattern of earlywood and latewood cells that are produced during secondary or radial growth. During the early part of the growing season, trees often produce large, thinwalled cells, and during the later period of the growing season, they produce smaller, thickerwalled cells. Hence, an annual ring will contain both an earlywood and latewood portion. By measuring the distance from the earlywood boundary of one ring to the earlywood boundary of another ring, the amount of wood produced during a given year can be quantified. Dendrochronologists have used accurately dated and measured tree rings in various research arenas: forest dynamics, reconstruction of past climate, dating archeological sites, dating forest fires, and even forensics. Needless to say, dendrochronology is an exciting field with many subdisciplines sure to interest many students.

Determination of Death Dates of Coarse Woody Debris of Multiple Species in the Central Hardwood Region (Indiana, USA)

Abstract Coarse woody debris (CWD; i.e. downed limbs and boles) serves numerous ecosystem functions, which vary according to the degree of decay. CWD decay is often described using five categories based on readily observed physical characteristics ranging from freshly fallen (Class I) to advanced decay with little structural integrity (Class V). Though useful in categorizing downed wood in a forest, these categories do not necessarily provide information about time since death or the decay process. Dendrochronology can be used to assign death dates to CWD and begin to provide a temporal description of the decay process. We used standard dendrochronological techniques to determine the death dates of 94 CWD samples from five common hardwood taxa in southern Indiana. Across taxa, the time since death of Class I (1.4 ± 1.7 years; mean ± SD; least decayed class) was significantly shorter than Class II (5.2 ± 3.6 years), which was shorter than the more decayed classes (Class III: 11.5 ± 4.9, and Class IV: 11.2 ± 5.6 years). Within this general trend, time since death within a decay class varied greatly among taxa. Combining dendrochronology techniques with visual decay characteristics can improve our understanding of CWDs role and provide a more precise timeline for biomass and nutrient turnover within forested systems.