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

A Simplified Summary of Supersymmetry

I give an overview of the motivations for and theory/phenomenology of supersymmetry.Comment: 24 pages, to appear in ``Future High Energy Colliders'', proceedings of the ITP Symposium, U.C. Santa Barbara, October 21-25, 1996, AIP Press. Also presented at the Aspen Winter Conference on High Energy Physics, January 1997, Aspen, CO. Full postscript file, is available via anonymous ftp at ftp://ucdhep.ucdavis.edu/gunion/itp96.p

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

Wood pyrolisys using aspen plus simulation and industrially applicable model

Over the past decades, a great deal of experimental work has been carried out on the development of pyrolysis processes for wood and waste materials. Pyrolysis is an important phenomenon in thermal treatment of wood, therefore, the successful modelling of pyrolysis to predict the rate of volatile evolution is also of great importance. Pyrolysis experiments of waste spruce sawdust were carried out. During the experiment, gaseous products were analysed to determine a change in the gas composition with increasing temperature. Furthermore, the model of pyrolysis was created using Aspen Plus software. Aspects of pyrolysis are discussed with a description of how various temperatures affect the overall reaction rate and the yield of volatile components. The pyrolysis Aspen plus model was compared with the experimental data. It was discovered that the Aspen Plus model, being used by several authors, is not good enough for pyrolysis process description, but it can be used for gasification modelling

Exploring emerging technologies for extreme scale HPC architectures

While architectures and programming models have remained relatively stable for almost two decades, new architectural features, such as heterogeneous processing, nonvolatile memory, and optical interconnection networks, will demand that software systems and applications be redesigned so that they expose massive amounts of hierarchical parallelism, carefully orchestrate data movement, and balance concerns over performance, power, and resiliency. This instability has led to two inevitable problems: decreased programmer productivity, and difficult performance prediction. In this talk, I will describe two solutions to these problems, respectively: our OpenARC compiler and runtime system, and our Aspen performance modeling language. First, OpenARC is a research compiler that supports OpenACC and OpenMP4, and can generate code in CUDA, OpenCL, and LLVM IR. OpenARC has enabled us to explore how to enable performance portability of applications across diverse architectures. Second, Aspen is a domain specific language for structured analytical modeling of applications and architectures. It is designed to enable rapid exploration of new algorithm and architectures. Once created, Aspen models can then be used for a variety of purposes including predicting performance of future applications, evaluating system architectures, informing runtime scheduling decisions, and identifying system anomalies

Isoprene Emission and Carbon Dioxide Protect Aspen Leaves from Heat Stress

High temperature, especially above 35oC, is known to reduce leaf photosynthetic rate in many tree species. This study investigated the effect of high temperature on isoprene-emitting (aspen) and non- emitting (birch) trees under ambient and elevated CO2 under open field conditions. Aspen trees tolerate heat better than birch trees and elevated CO2 protects both species against moderate heat stress. The increased thermotolerance in aspen trees compared to the birch trees may result from the aspen's ability to produce isoprene. Elevated CO2 increased carboxylation capacity, photosynthetic electron transport capacity and triose phosphate use in both birch and aspen trees. High temperature decreased all of these parameters in birch regardless of CO2 treatment but only photosynthetic electron transport and triose phosphate use at ambient CO2 were reduced in aspen. As temperature rises, non-isoprene-emitting trees will be at a disadvantage and biological diversity and species richness might be lost in some ecosystems. Our results indicate that isoprene emitting tree species will have an advantage over non-isoprene emitting ones under high temperatures

Baryogenesis and the New Cosmology

In this talk I begin with a brief review of the status of approaches to understanding the origin of the baryon asymmetry of the universe (BAU). I then describe a recent model unifying three seemingly-distict problems facing particle cosmology: the origin of inflation, the generation of the BAU and the nature of dark energy.Comment: 16 pages, RevTeX, Plenary talk presented at PASCOS-03, Mumbai, India; COSMO-02, Chicago, and at the Aspen Winter 2003 Conference on Particle Physics: At the Frontiers of Particle Physics, Aspen Center for Physics. To appear in the proceedings of PASCOS-0

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