Tree-Ring Research, Volume 75 (2019)

Utility of Herbaceous Annual Rings as Markers of Plant Response to Disturbance: A Case Study Using Roots of a Common Milkweed Species of the US Tallgrass Prairie

Fri, 01 Mar 2019 00:00:00 GMT

Utility of Herbaceous Annual Rings as Markers of Plant Response to Disturbance: A Case Study Using Roots of a Common Milkweed Species of the US Tallgrass Prairie Dee, Justin R.; Palmer, Michael W. Herb-chronology, the study of annual growth rings in the root to shoot transitional zone of perennial forbs, involves efforts mostly devoted to finding correlations between growth increment and annual climate. The potential of using growth rings as markers of plant growth response to more ecological phenomena such as periodic disturbance still remains mostly untapped. By monitoring the 2016 growth increment of 64 individuals of a common milkweed species (Asclepias viridis) from the US tallgrass prairie system we investigate plant response to factorial treatments of early season shoot removal and neighbor thinning. These treatments simulate bouts of herbivory, grazing, and dormant-season fire, each of which should have differential effects on plant growth. Neighbor thinning had the strongest effects of the study, moderately increasing ring widths. Conversely, ring widths were moderately decreased by shoot removal. Individual age had negative effects on ring width. These results are the first evidence of herbaceous annual ring sensitivity to sudden amelioration of resources as well as a significant loss of aboveground biomass. Herb-chronology could be useful in future studies monitoring the effects of disturbance on plant growth, increasing our understanding of these phenomena and their overall effect on grassland composition.

Sapwood Rings Estimation for Pinus Sylvestris L. in Lithuania and Latvia

Fri, 01 Mar 2019 00:00:00 GMT

Sapwood Rings Estimation for Pinus Sylvestris L. in Lithuania and Latvia Vitas, Adomas; Zunde, Maris Pinus sylvestris L. is the predominant tree species used for wooden constructions in the Baltic area. Accordingly, the timber of Pinus is the most important object for investigation and dating carried out by dendrochronologists of the Baltic countries. However, the dating of historical Pinus is often challenging when the outer sapwood rings are missing in the wood samples. In Pinus, sapwood rings increase in number as the tree ages, and therefore calculating the approximate number of missing outer rings from a set range, a technique used for oak, is not possible. In Norway, a simple method for estimating the number of sapwood rings has been developed for some native species of conifers. The aim of this small-scale study was to assess the validity and the practical suitability of the Norwegian method for estimating the number of missing sapwood rings of mostly historical Pinus wood samples obtained in the southeastern part of the Baltic region. Our findings indicate that this method is not acceptable for estimating the number of missing sapwood rings for individual trees, but suggest that it may be applicable when dating tree-ring chronologies for a minimum of 20 trees, containing individuals up to 200 years old.

No Significant Increase in Tree Mortality Following Coring in a Temperate Hardwood Forest

Fri, 01 Mar 2019 00:00:00 GMT

No Significant Increase in Tree Mortality Following Coring in a Temperate Hardwood Forest Helcoski, Ryan; Tepley, Alan J.; McGarvey, Jennifer C.; Gonzalez-Akre, Erika; Meakem, Victoria; Thompson, Jonathan R.; Anderson-Teixeira, Kristina J. The collection of tree-ring data from living trees is widespread and highly valuable in ecological and dendro-climatological research, yet there is concern that coring injures trees, potentially contributing to mortality. Unlike resinous conifers that can quickly compartmentalize wounds, less decay-resistant angiosperms may face more pronounced risk of injury from coring. To test if coring increases mortality rates in temperate hardwood trees, we leverage a unique dataset tracking the mortality of cored and uncored hardwood trees representing 19 species from 10 genera in a 26-ha plot in Virginia, USA. We compare mortality rates between 935 cored trees and 8605 uncored trees for seven years following coring. Annual mortality rates did not differ between cored trees (1.71% yr(-1); 95% CI 1.40 to 2.20) and uncored trees (1.85% yr(-1); 95% CI 1.70 to 2.28) across the full dataset, nor were there differences by genus or size class. These results indicate that the risk of hardwood mortality caused by increment coring is probably lower than previously assumed. However, these results cannot rule out the possibility that coring elevates hardwood mortality in other climates or when trees facemultiple additional stressors that were not influential over the course of our study.

Identifying Old Trees to Inform Ecological Restoration in Montane Forests of the Central Rocky Mountains, USA

Fri, 01 Mar 2019 00:00:00 GMT

Identifying Old Trees to Inform Ecological Restoration in Montane Forests of the Central Rocky Mountains, USA Brown, Peter M.; Gannon, Benjamin; Battaglia, Mike A.; Fornwalt, Paula J.; Huckaby, Laurie S.; Cheng, Antony S.; Baggett, L. Scott Old trees (defined here as >= 150 years old) can be rare in many forests because of past timber harvest, uncharacteristically severe wildfires, and-increasingly-climate change. Old trees provide unique structural, ecological, scientific, and aesthetic values missing in forests containing only younger trees. Here we compile crossdated ages from over 10,000 living and dead trees sampled in montane forests of the central Rocky Mountains in Colorado and southern Wyoming, USA, to examine changes in age structure of the oldest trees since Euro-American settlement and to provide guidelines to aid in identification of old trees for retention during ecological restoration treatments. Eroded stumps (containing only heartwood) were found in over 93% of 179 randomly sampled plots. Number of stumps found in each plot was proportional to reconstructed historical (1860 C. E.) stand basal area. The regional median date of maximum plot tree recruitment was over 150 years older when including stumps versus only living trees, suggesting that if all those harvested trees had survived to the present, the ages of oldest trees would be substantially greater than it is today. However, the regional median age of oldest trees in 1860 before harvesting was not different from the median age of oldest living trees in the current forest (246 vs. 248 years), which alternatively suggests that the regional population of oldest trees has recovered to near historical levels in the time since early Euro-American harvests. Each living tree at the time of sampling was assigned to one of three potential age classes based on a subjective assessment of tree morphology: old (likely >= 150 years old), young (likely <150 years old), or transitional (containing a mixture of young and old tree characteristics). Trees assigned to the old and young morphology categories were classified correctly 88% to 96% of the time depending on species as confirmed by their crossdated ages. Regression tree analysis revealed that tree diameter at breast height was not as reliable a predictor of tree age as were morphological characteristics. A measure of site productivity was a significant variable to use to separate transitional morphology trees into old and young age classes, but classification accuracy was not high because of large variability in ages of these trees. Our results suggest that residual live old trees in the current forest, although perhaps not rare compared to historical age distributions, should be retained during restoration treatments, and that using simple morphological and environmental criteria to identify old trees is more reliable than tree size alone.