David R. Carter

Bio: David R. Carter is an academic researcher from Virginia Tech. The author has contributed to research in topics: Broom & Cytisus scoparius. The author has an hindex of 6, co-authored 22 publications receiving 104 citations. Previous affiliations of David R. Carter include University of Maine & University of Minnesota.

Tree Growth and Resilience to Extreme Drought Across an Urban Land-use Gradient

Abstract: Understanding the response of urban forests to extreme climatic events, such as drought, will be essential to predicting impacts of climate change on the urban tree canopy and related ecosystem services. This study evaluated variation in tree growth and drought resistance (growth during drought) and resilience (growth in period following drought) across four land-use categories (built, transportation, park, and semi-natural forest) and four species (Acer saccharum, Gymnocladus dioicus, Liriodendron tulipifera, and Pinus strobus) at The Morton Arboretum in suburban Lisle, Illinois, U.S. Tree growth and resistance to drought both varied as an interaction between land-use and species (F 15, 100 = 5.25, p < 0.001; F 15, 100 = 2.42, p = 0.005). Resilience of tree growth to extreme drought was generally high and did not vary across species and land-uses. In this study, individual tree species responses to drought varied across land-uses, illustrating the difficulty of predicting the reaction of urban forests to projected increases in the frequency of extreme climatic events. Tree growth response to drought varied even across the relatively narrow range of growing conditions studied here. Investigation of a broader range of sites, encompassing the full urban forest continuum, would likely demonstrate even greater variation in tree response to extreme climatic events.

Scotch broom (Cytisus scoparius) modifies microenvironment to promote nonnative plant communities.

Abstract: Scotch broom [Cytisus scoparius (L.) Link] is a globally important nitrogen (N)-fixing invasive plant species that has potential to alter soil water dynamics, soil chemistry, and plant communities. We evaluated the effects of Scotch broom on soil moisture, soil chemistry, soil temperature, photosynthetically active radiation (PAR), and vegetation communities over 4 years at a site recently harvested for timber. Treatments of Scotch broom (either present via planting or absent) and background vegetation (either present or absent via herbicide treatments) were applied to 4 m2 plots. Background vegetation was associated with the greatest decrease of soil water content (SWC) among treatments. During the driest year, Scotch broom showed some evidence of increased early-and late-season soil water usage, and, briefly, a high usage relative to background vegetation plots. On a percent cover basis, Scotch broom had a substantially greater negative influence on SWC than did background vegetation. Surprisingly, Scotch broom was not consistently associated with increases in total soil N, but there was evidence of increasing soil water N when Scotch broom was present. Scotch broom-only plots had greater concentrations of soil water magnesium (Mg2+) and calcium (Ca2+) than other treatments. On a percent cover basis, Scotch broom had a uniquely high demand for potassium (K+) relative to the background vegetation. Average soil temperature was slightly greater, and soil surface PAR lower, with Scotch broom present. Scotch broom-absent plots increased in species diversity and richness over time, while Scotch broom-present plots remained unchanged. Scotch broom presence was associated with an increase in cover of nonnative sweet vernalgrass (Anthoxanthum odoratum L.). Scotch broom generated positive feedbacks with resource conditions that favored its dominance and the establishment of nonnative grass.

Crown architecture, crown leaf area distribution, and individual tree growth efficiency vary across site, genetic entry, and planting density

Abstract: We examined crown architecture and within crown leaf area distribution effects on Pinus taeda L. growth in North Carolina (NC), Virginia (VA), and Brazil (BR) to better understand why P. taeda can grow much better in Brazil than in the southeastern United States. The NC, VA, and BR sites were planted in 2009, 2009, and 2011, respectively. At all sites, we planted the same two genetic entries at 618, 1236, and 1854 trees ha−1. In 2013, when trees were still open grown, the VA and NC sites had greater branch diameter (24%), branch number (14%), live crown length (44%), foliage mass (82%), and branch mass (91%), than the BR site. However, in 2017, after crown closure and when there was no significant difference in tree size, site did not significantly affect these crown variables. In 2013, site significantly affected absolute leaf area distribution, likely due to differences in live crown length and leaf area, such that there was more foliage at a given level in the crown at the VA and NC sites than at the BR site. In 2017, site was still a significant factor explaining leaf area distribution, although at this point, with crown closure and similar sized trees, there was more foliage at the BR site at a given level in the crown compared to the VA and NC sites. In 2013 and 2017, when including site, genetic entry, stand density, and leaf area distribution parameters as independent variables, site significantly affected individual tree growth efficiency, indicating that something other than leaf area distribution was influencing the site effect. Better BR P. taeda growth is likely due to a combination of factors, including leaf area distribution, crown architecture, and other factors that have been identified as influencing the site effect (heat sum), indicating that future work should include a modeling analysis to examine all known contributing factors.

Rapid aerosol particle growth and increase of cloud condensation nucleus activity by secondary aerosol formation and condensation: A case study for regional air pollution in northeastern China

Abstract: [1] This study was part of the international field measurement Campaigns of Air Quality Research in Beijing and Surrounding Region 2006 (CAREBeijing-2006). We investigated a new particle formation event in a highly polluted air mass at a regional site south of the megacity Beijing and its impact on the abundance and properties of cloud condensation nuclei (CCN). During the 1-month observation, particle nucleation followed by significant particle growth on a regional scale was observed frequently (~30%), and we chose 23 August 2006 as a representative case study. Secondary aerosol mass was produced continuously, with sulfate, ammonium, and organics as major components. The aerosol mass growth rate was on average 19 μg m -3 h -1 during the late hours of the day. This growth rate was observed several times during the 1-month intensive measurements. The nucleation mode grew very quickly into the size range of CCN, and the CCN size distribution was dominated by the growing nucleation mode (up to 80% of the total CCN number concentration) and not as usual by the accumulation mode. At water vapor supersaturations of 0.07-0.86%, the CCN number concentrations reached maximum values of 4000-19,000 cm -3 only 6-14 h after the nucleation event. During particle formation and growth, the effective hygroscopicity parameter κ increased from about 0.1-0.3 to 0.35-0.5 for particles with diameters of 40-90 nm, but it remained nearly constant at ~0.45 for particles with diameters of ~190 nm. This result is consistent with aerosol chemical composition data, showing a pronounced increase of sulfate.

Climate change effects on plant-soil feedbacks and consequences for biodiversity and functioning of terrestrial ecosystems

Abstract: Plant-soil feedbacks (PSFs) are interactions among plants, soil organisms, and abiotic soil conditions that influence plant performance, plant species diversity, and community structure, ultimately driving ecosystem processes. We review how climate change will alter PSFs and their potential consequences for ecosystem functioning. Climate change influences PSFs through the performance of interacting species and altered community composition resulting from changes in species distributions. Climate change thus affects plant inputs into the soil subsystem via litter and rhizodeposits and alters the composition of the living plant roots with which mutualistic symbionts, decomposers, and their natural enemies interact. Many of these plant-soil interactions are species-specific and are greatly affected by temperature, moisture, and other climate-related factors. We make a number of predictions concerning climate change effects on PSFs and consequences for vegetation-soil-climate feedbacks while acknowledging that they may be context-dependent, spatially heterogeneous, and temporally variable.

Windthrow probability as a function of stand characteristics and shelter

Abstract: In 1981 a storm caused windthrow of 3 million cubic meters of softwood in Denmark, equal to the normal removals of three years. The object of the present analysis is to determine the way in which the probability of windthrow depends on parameters that can be affected by forest management, viz. rotation age, thinning programme, choice of species, spatial distribution of stands and drainage. An empirical data set from 612 stands is used in the estimations. It is found that the windthrow probability is negatively affected by tree diameter, drainage, the time since last thinning and the protection from other stands. The probability increases with tree height, age and relative thinning volume in the latest thinning. Picea is more stable than Abies and Pseudotsuga.

Flipped Learning: Gateway to Student Engagement

Abstract: Jonathan Bergmann and Aaron Sams, Flipped Learning: Gateway to Student Engagement, International Society for Technology in Education: Eugene, Oregon and Washington, DC, 2014; 169 pp.: ISBN 978-1-56484-344-9There are two main reasons for the book Flipped Learning: Gateway to Student Engagement being an interesting read. The first is that the book discusses a relatively new concept, dating back to only 2006. The second is that it is written by the pioneers of the concept of flipped learning. Both reasons add to high expectations for this book.The authors of the book, Jonathan Bergmann and Aaron Sams, both have teaching experience and were in fact colleagues when they started developing the idea of flipped learning. They were both teaching high school chemistry and shared a common vision: 'to put our students first so they could develop both cognitively and affectively' (p. ix). From their initial collaboration and the idea of flipping, stemmed a numerous online community of educators interested in flipping their teaching, the Flipped Learning Network (flippedclassroom.org) with a membership of over 20,000 in 2014.The book Flipped Learning: Gateway to Student Engagement is divided into two halves. In the first four chapters, the authors explain their background and aim to persuade the reader about the efficiency of the presented concept. Bergmann and Sams substantiate their thesis of flipped learning being a unique experience for each teacher and their class by including stories from a wide range of subject matter teachers, such as math, chemistry, physical education, biology, history, English and science (Chapters 5 to 11). There is also a story by a primary school fifth-grade teacher who flips her classes (Chapter 12) and a story of flipping professional development courses for teachers (Chapter 13). The final chapter summarises the teachers' stories, reviews the benefits of flipping, and even suggests that school administrators should flip their staff meetings to make better use of face-to-face time and thus empower teachers.The book cover presents the book as a 'revolutionary education philosophy' taken to the next level. This refers to Bergmann and Sams' previous book, Flip Your Classroom: Reach Every Student in Every Class Every Day (2012), in which the authors focused mainly on producing high-quality videos for students, while in Flipped Learning, the classroom is truly student-centred and the teacher individualises instruction in order to engage each student. The book offers a general introductory look into the concept of flipped learning and indicates possible further exploration. The authors have expanded these primary notions by writing four more books dedicated to different subjects of flipping - a book series that supports flipped learning in five topic areas: science, math, English, social studies, and the elementary classroom.Bergmann and Sams define flipped learning as an instructional model in which direct instruction is delivered individually through videos. The amount of whole-class instruction is minimised and time and space are given to other student grouping forms and activities, such as problem-based learning, discussion, inquiry, project work, etc. Throughout the book, the 'One Question' that the authors pose in the Introduction, is a common thread and this question is "What is the best use of face-to-face time with students?" (p. 3). Bergmann and Sams insist that this is the question that is the core of flipped learning and one that each teacher should ask constantly. Moreover, they believe each teacher should provide a unique and individual answer to it, according to the needs of their own students.The concept of flipped learning appeared in 2006 and has passed several developmental stages since then, which also affected the terminological aspect of the concept. Originally, the concept of the flipped classroom, as it was then called, was based on the use of video as a medium of content transfer, while the teacher was at the centre of instruction. …