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435 results on '"Thompson, Jonathan R."'

6. Carbon budget of the Harvard Forest Long‐Term Ecological Research site: pattern, process, and response to global change

Author

Finzi, Adrien C, Giasson, Marc‐André, Plotkin, Audrey A Barker, Aber, John D, Boose, Emery R, Davidson, Eric A, Dietze, Michael C, Ellison, Aaron M, Frey, Serita D, Goldman, Evan, Keenan, Trevor F, Melillo, Jerry M, Munger, J William, Nadelhoffer, Knute J, Ollinger, Scott V, Orwig, David A, Pederson, Neil, Richardson, Andrew D, Savage, Kathleen, Tang, Jianwu, Thompson, Jonathan R, Williams, Christopher A, Wofsy, Steven C, Zhou, Zaixing, and Foster, David R

Subjects
Life on Land, belowground production, carbon cycling, climate change, disturbance, ecosystem ecology, eddy covariance, forest ecosystems, gross primary production, long-term ecological research, net primary production, permanent plots, Physical Geography and Environmental Geoscience, Ecological Applications, Ecology
Abstract

How, where, and why carbon (C) moves into and out of an ecosystem through time are long-standing questions in biogeochemistry. Here, we bring together hundreds of thousands of C-cycle observations at the Harvard Forest in central Massachusetts, USA, a mid-latitude landscape dominated by 80–120-yr-old closed-canopy forests. These data answered four questions: (1) where and how much C is presently stored in dominant forest types; (2) what are current rates of C accrual and loss; (3) what biotic and abiotic factors contribute to variability in these rates; and (4) how has climate change affected the forest’s C cycle? Harvard Forest is an active C sink resulting from forest regrowth following land abandonment. Soil and tree biomass comprise nearly equal portions of existing C stocks. Net primary production (NPP) averaged 680–750 g C·m−2·yr−1; belowground NPP contributed 38–47% of the total, but with large uncertainty. Mineral soil C measured in the same inventory plots in 1992 and 2013 was too heterogeneous to detect change in soil-C pools; however, radiocarbon data suggest a small but persistent sink of 10–30 g C·m−2·yr−1. Net ecosystem production (NEP) in hardwood stands averaged ~300 g C·m−2·yr−1. NEP in hemlock-dominated forests averaged ~450 g C·m−2·yr−1 until infestation by the hemlock woolly adelgid turned these stands into a net C source. Since 2000, NPP has increased by 26%. For the period 1992–2015, NEP increased 93%. The increase in mean annual temperature and growing season length alone accounted for ~30% of the increase in productivity. Interannual variations in GPP and NEP were also correlated with increases in red oak biomass, forest leaf area, and canopy-scale light-use efficiency. Compared to long-term global change experiments at the Harvard Forest, the C sink in regrowing biomass equaled or exceeded C cycle modifications imposed by soil warming, N saturation, and hemlock removal. Results of this synthesis and comparison to simulation models suggest that forests across the region are likely to accrue C for decades to come but may be disrupted if the frequency or severity of biotic and abiotic disturbances increases.

Published
2020

11. Vascular Surgery

Author

Thompson, Jonathan R., Johanning, Jason, Lee, Andrew G., editor, Potter, Jane F., editor, and Harper, G. Michael, editor

Published
2021
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14. Generalized Assembly of Semiconductor–Molecule Superlattices

Author

Peterson, Duncan A., Farnsworth, Tyler W., Woomer, Adam H., Fishman, Zachary S., Shapiro, Sydney H., Radomsky, Rebecca C., Barron, Emily A., Thompson, Jonathan R., and Warren, Scott C.

Abstract

The synthesis of structurally precise materials that combine diverse building blocks will accelerate the development of artificial solids for electronics, energy, and medicine. Here, we utilize simulation to identify how organic molecules can self-assemble with 2D materials into periodic superlattices with alternating layers of molecules and 2D monolayers. We experimentally demonstrate the generalizability of this mechanism by applying it to 2D semiconductors and various organic molecules or polymers. The resulting superlattices have unique and well-defined lattice constants that depend on the dimensions of the organic species. We are able to design superlattices with a wide variety of molecules (photoresponsive, chelating, light-emitting moieties), suggesting that the self-assembly does not depend on any specific chemical interaction and yet can accommodate chemically diverse functional groups. We also observe that the 2D materials within the superlattices (MoS2, WSe2) remain quantum-confined, even though the superlattice retains excellent electrical conductivity. This introduction of a mechanism and its experimental realization yield a general design strategy for a large class of quantum-confined, molecule–2D hybrid materials.

Published
2025
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42. Size-related scaling of tree form and function in a mixed-age forest

Author

Anderson-Teixeira, Kristina J., McGarvey, Jennifer C., Muller-Landau, Helene C., Park, Janice Y., Gonzalez-Akre, Erika B., Herrmann, Valentine, Bennett, Amy C., So, Christopher V., Bourg, Norman A., Thompson, Jonathan R., McMahon, Sean M., and McShea, William J.

Published
2015

47. Communicating Grammatically: Evaluating a Learner Strategy Website for Spanish Grammar

Author

Cohen, Andrew D., Pinilla-Herrera, Angela, and Thompson, Jonathan R.

Abstract

After a brief introduction to language learner strategies and grammar strategies as a subcategory, it is pointed out that research on the use of grammar strategies by learners of a second language (L2) has been limited. The article then describes the construction of a website with strategies for learning and performing Spanish grammar, with a focus on grammar that was found to be problematic for both nonnative learners and teachers alike. The website is divided into strategies for learning a specific grammar form and strategies which are consistent with the learners' style preferences and which could be applied to various grammar forms. The website's focus is on strategizing about the learning and use of Spanish grammar rather than as a compendium of rules for Spanish grammar. The article ends with a report on a small-scale study using largely qualitative means to determine the impact of a Spanish grammar strategies website on 15 learners who agreed to track their experiences with selected strategies over a period of 6-8 weeks. Students' responses on the strategy tracking forms and in the interviews over the course of study indicated that the learners generally benefited to some extent and in some cases greatly from use of the website, suggesting its potential for supporting learners of Spanish in remembering and correctly using various grammatical forms that had previously been problematic for them. (Contains 3 figures, 2 tables, and 2 notes.) [This paper was presented at the 2009 Annual Meeting of the American Council on the Teaching of Foreign Languages, San Diego, CA, Nov 20, 2009.]

Published
2011

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