Recognizing the Toxicodendrons (poison ivy, poison oak, and poison sumac).
Poison ivy, poison oak, and poison sumac are now classified in the genus Toxicodendron which is readily distinguished from Rhus. In the United States, there are two species of poison oak, Toxicodendron diversilobum (western poison oak) and Toxicodendron toxicarium (eastern poison oak). There are also two species of poison ivy, Toxicodendron rydbergii, a nonclimbing subshrub, and Toxicodendron radicans, which may be either a shrub or a climbing vine. There are nine subspecies of T. radicans, six of which are found in the United States. One species of poison sumac, Toxicodendron vernix, occurs in the United States. Distinguishing features of these plants and characteristics that separate Toxicodendron from Rhus are outlined in the text and illustrated in color plates.
Toxicodendrons of the United States.
Abstract What is a Toxicodendron and why is poison ivy now termed Toxicodendron radicans rather than Rhus radicans ? Many scientific articles today continue to use Rhus to describe poison oak and poison ivy, because Linnaeus, the father of taxonomic botany, classified poison ivy, poison oak, and poison sumac in the genus Rhus . The name Toxicodendron originated with Tournefort, 1 who preceded Linnaeus, so it is not new. The reasons for its separation from Rhus are cogent, 1,2 but until classic treatises by Barkley 3 on the Anacardiaceae and Gillis 1 on Toxicodendron , there was little tendency to change from the old ways. Brizicky, 4 emphasizing exceptions, argued against separation of Toxicodendron , and Barkley 5 wrote a rebuttal. Fortunately, a major shift toward use of Toxicodendron now has occurred in scientific publications. Excluding Toxicodendron , (true) Rhus rarely causes contact dermatitis, so these plants should be considered benign. There also are allergenic Anacardiaceae other than Toxicodendron that contain alk(en)yl catechols, so the separation of these genera is based not only on allergenicity, but on a multiplicity of reliable botanic features, many of which can be used in field recognition. Accurate identification of poison ivy throughout all four seasons and in various stages of growth requires practice as well as knowledge of other plants in that locality and terrain. Unfortunately, many persons who can "reliably" recognize these plants often use leaf morphology as their primary criterion, even though leaves are not present much of the year. The material in this chapter is intended as a basis for developing a successful identification system; however, to become proficient, one should identify several plants in a location where they can be observed throughout the year. Before long, the differences between the benign and toxic plants will become so obvious that field identification of typical plants will be almost automatic. Extremely young plants, some winter specimens, and some clones of (eastern) poison oak still can be a problem for almost anyone.
Assessment of Ground Regeneration around Borehole Heat Exchangers between Heating Seasons in Cold Climates: A Case Study in Bialystok (NE, Poland)
Based on the experimental studies, the process of ground regeneration around the borehole loaded with brine-water heat pumps working exclusively for heating purposes in the period of four consecutive heating seasons in a cold climate was presented. The research was conducted in north-eastern Poland. The aim of the work is to verify the phenomenon of thermal ground regeneration in the period between heating seasons on the basis of the recorded data and to check whether the ground is able to regenerate itself and at what rate. It was noticed that the ground does not fully regenerate, especially during heating seasons with lower temperatures. In the analyzed period, from 22 September 2016 to 12 October 2020, the ground probably cooled irreversibly by 1.5 °C. In order to illustrate and evaluate the speed of changes in the ground, the one’s profile with an undisturbed temperature field was presented for each month of the year. The presented results can be a very important source of information for the analysis of geothermal conditions occurring in the ground. They can be used to verify mathematical models and conduct long-term simulations that allow us to see the complexity of the processes taking place in the ground.