Populus tremuloides seedling establishment: An underexplored vector for forest type conversion after multiple disturbances

Ecosystem resilience to climate change is contingent on post-disturbance plant regeneration. Sparse gymnosperm regeneration has been documented in subalpine forests following recent wildfires and compounded disturbances, both of which are increasing. In the US Intermountain West, this may cause a shift to non-forest in some areas, but other forests may demonstrate adaptive resilience through increased quaking aspen (Populus tremuloides Michx.) dominance. However, this potential depends on ill-defined constraints of aspen sexual regeneration under current climate. We created an ensemble of species distribution models for aspen seedling distribution following severe wildfire to define constraints on establishment. We recorded P. tremuloides seedling locations across a post-fire, post-blowdown landscape. We used 3 algorithms (Mahalanobis Typicalities,Multilayer Perceptron Artificial Neural Network, and MaxEnt) to create spatial distribution models for aspen seedlings and to define constraints. Each model performed with high accuracy and was incorporated into an ensemble model, which performed with the highest overall accuracy of all the models. Populus tremuloides seedling distribution is constrained primarily by proximity to unburned aspen forest and annual temperature ranges, and secondarily by light availability, summer precipitation, and fire severity. Based on model predictions and validation data, P. tremuloides seedling regeneration is viable throughout 54% of the post-fire landscape, 97% of which was previously conifer-dominated. Aspen are less susceptible to many climatically-sensitive disturbances (e.g. fire, beetle outbreak, wind disturbance), thus, aspen expansion represents an important adaptation to climate change. Continued aspen expansion into post-disturbance landscapes through sexual reproduction at the level suggested by these results would represent an important adaptation to climate change and would confer adaptive forest resilience by maintaining forest cover, but would also alter future disturbance regimes, biodiversity, and ecosystem services.Ye

The Importance of Saperda Inornata and Oberea Schaumii (Coleoptera: Cerambycidae) Galleries as Infection Courts of Hypoxylon Pruinatum in Trembling Aspen, Populus Tremuloides

(excerpt) Trembling aspen, Populus tremuloides Michaux, and bigtooth aspen, P. grandidentata Michaux, are hosts of numerous species of injurious insects and microorganisms (Harrison 1959). Only a few of those organisms, however, are directly responsible for mortality of healthy trees. The fungus Hypoxylon pruinatum (Klotzsche) Cke. is most important in that respect, killing 1-2%o f the standing volume annually in the Lake States (Anderson 1964). It invades and spreads in cambial tissue, killing it and eventually the branch or stem by girdling. Initially, a canker appears as a sunken, yellowish-orange area in the bark (Anderson 1956). In a later stage the outer bark raises in blister-like patches and sloughs off exposing blackened, crumbling cortex

The Distribution of Saperda Inornata and Oberea Schaumii (Coleoptera: Cerambycidae) within the Crowns of Large Trembling Aspens, Populus Tremuloides

The larvae of Saperda inornata Say and Oberea schaumii LeConte inhabit the stems of trembling aspen (Populus tremuloides Michaux) root suckers and the twigs of larger trees. Nord et al. (1972a, 1972b) reported the biologies of these species in Upper Michigan and northern Wisconsin. S. inornata has a one or two year life cycle, probably depending on how early the egg is laid. Most (77.5%) 0. schaumii develop in three years while 5.0% require only two years and 17.5% require four years to develop. Knight (1963) described the distribution of galleries made by S. inornata and 0. schaumii in the crowns of large trembling aspen, P. tremuloides, in Upper Michigan. Similar distribution data were gathered from 180 large trembling aspen felled in a survey designed to determine the relative abundance of S. inornata and 0. schaumii in stands of different site quality (Nord and Knight 1972b). The analysis of that distribution data and comparisons with that of Knight (1963) are presented here. Inter- and intra-specific competition in light of the results and other behavioral information are discussed

The Relationship of the Abundance of \u3ci\u3eSaperda Inornata\u3c/i\u3e and \u3ci\u3eOberea Schaumii\u3c/i\u3e (Coleoptera: Cerambycidae) in Large Trembling Aspen, \u3ci\u3ePopulus Tremuloides\u3c/i\u3e, to Site Quality

Saperda inornata Say and Oberea schaumii LeConte are cerambycids that inhabit the stems of trembling aspen, Populus tremuloides Michaux, root suckers and the twigs of larger trees. The biologies of those species in northern Wisconsin and Upper Michigan were reported by Nord et al. (1972a and 1972b). S. inornata oviposits on the cambium under horseshoe- or shield-shaped egg niches gnawed in the outer bark by the female. The term egg niche, connotes an oviposition place prepared by the female using the mandibles and ovipositor (Linsley 1959). There are usually 2 or 3 egg niches at one level on the stem or twig, and a globose gall consisting of callus tissue forms there. The larvae feed in the cambial and callus tissue around the gall and require 1 or 2 years to complete development. The 0. schaurnii female gnaws an elongate, rectangular egg niche in the outer bark and deposits an egg on the cambium beneath it. The larva bores downward from the egg niche in the wood. Most individuals require 3 years to complete the life cycle; but some take only 2 years, while others take 4 years. A survey designed to determine the importance of the egg niches and galleries of S. inornata and 0. schaumii as infection courts of Hypoxylon pruinatum (Klotzsche) Cke. in large trembling aspen was begun in 1962 in Iron and Ontonogan Counties, Michigan. The data from that survey indicated that abundance of borers might be correlated with the site quality of the stand. Therefore in 1963 the survey was redesigned to detect differences in abundance between stands of different site quality. Since the redesign concerned only the selection of stands, not the sampling procedures used within the stand, most of the trees sampled in 1962 were incorporated into the redesigned survey. The data collected in conjuction with the survey also make possible conclusions regarding the distribution of borer galleries within the crowns of large trees. Those results and a discussion of competition between S. inornata and 0. schaurnii are given in another paper (Nord and Knight, 1972a). The incidence of H. pruinatum in the galleries was reported by Nord and Knight (1972b)

A phytosociological survey of the boreal forest (Vaccinio-Piceetea) in North America

A survey of syntaxa of vegetation of North American boreal forests (class Vaccinio-Piceetea) is presented. This phytosociological survey, carried out combining the Braun-Blanquet method with numerical syntaxonomical analyses (cluster and correspondence analysis), describes the associations of the North American boreal forests, which have several species, varieties or vicariant species in common with their Eurasian counterparts, and can be placed in the class Vaccinio-Piceetea. By means of tabular and multivariate analyses, 2084 North American relevés were compared with 3273 relevés from European, Japanese and Korean boreal forest, to describe and typify 4 orders, 10 alliances and 37 associations. Diagnostic tables, ordination, clustering, and climatic, edaphic and biogeographical data were used to show floristic affinities among these syntaxa and interpret their distribution areas. Syntaxa were briefly characterized by their floristic composition, physiognomy, succession, zonation, and biogeographical distribution

Analyzing tree distribution and abundance in Yukon-Charley Rivers National Preserve: developing geostatistical Bayesian models with count data

Master's Project (M.S.) University of Alaska Fairbanks, 2018Species distribution models (SDMs) describe the relationship between where a species occurs and underlying environmental conditions. For this project, I created SDMs for the five tree species that occur in Yukon-Charley Rivers National Preserve (YUCH) in order to gain insight into which environmental covariates are important for each species, and what effect each environmental condition has on that species' expected occurrence or abundance. I discuss some of the issues involved in creating SDMs, including whether or not to incorporate spatially explicit error terms, and if so, how to do so with generalized linear models (GLMs, which have discrete responses). I ran a total of 10 distinct geostatistical SDMs using Markov Chain Monte Carlo (Bayesian methods), and discuss the results here. I also compare these results from YUCH with results from a similar analysis conducted in Denali National Park and Preserve (DNPP)

The Response of Aspen \u3ci\u3e(Populus Tremuloides)\u3c/i\u3e to Artificial Defoliation

(excerpt) In the summers of 1939 and 1940 hand defoliation oftrembling aspen, Populus tremuloides Michx., was carried on in a young stand located a few miles north of Itasca State Park. This study was undertaken to determine the response of aspen trees to several amounts of defoliation at four different times during the summer. Other similar artificial defoliation studies have been reported by Wallace (1945), Giese et al. (1964), Skilling (1964), Kulman (197 I), and Heichel and Turner (1976)

Effects of Aspen Phenolic Glycosides on Gypsy Moth (Lepidoptera: Lymantriidae) Susceptibility to \u3ci\u3eBacillus Thuringiensis\u3c/i\u3e

Performance of the gypsy moth, Lymantria dispar, on quaking aspen, Populus tremuloides, is strongly affected by foliar concentrations of phenolic glycosides. Because the microbial insecticide Bacillus thuringiensis is widely used against gypsy moths and has a mode of action similar to that of phenolic glycosIdes, we investigated the combined effects of the two toxins on gypsy moth larvae. The experimental design was a 2 x 2 factorial: two levels (0, +) of phenolicglycosides for each of two levels (0, +) of B. thuringiensis. The toxins were incorporated into artificial diets and bioassayed against first and fourth instars. Bacillus thuringiensis and phenolic glycosides ne~atively and addi· tively affected larval survival, growth and development tImes. Both agents slightly reduced consumption rates. In addition, B. thuringiensis reduced diet digestibility whereas phenolic glycosides decreased the efficiency with which food was converted to biomass. These results suggest that the efficacy of B. thuringiensis applications in aspen forests is likely to be affected by the allelo· chemical composition of foliage