Chris E Johnson

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Chemical changes along headwater streams at the Hubbard Brook Experimental Forest in New Hampshire suggest that important differences exist in biogeochemical cycles along an altitudinal gradient within small watershed ecosystems. Using data collected during the period 1982–92, we have constructed element budgets [Ca, Mg, K, Na, Si, Al, dissolved organic(More)
The depletion of calcium in forest ecosystems of the northeastern USA is thought to be a consequence of acidic deposition and to be at present restricting the recovery of forest and aquatic systems now that acidic deposition itself is declining. This depletion of calcium has been inferred from studies showing that sources of calcium in forest ecosystems(More)
We present a range of estimates for future radiative forcings due to changes in tropospheric ozone (O3T ). Ozone distributions were generated by the UKMO 3-D chemistry-transport model for 1990, 2030, 2060, and 2100, using four sets of boundary conditions. Anthropogenic emissions evolved following either the IPCC SRES “high” (A2) or “central” (B2) case. Each(More)
Atmospheric impact of the 1783–1784 Laki eruption: Part I Chemistry modelling D. S. Stevenson, C. E. Johnson, E. J. Highwood, V. Gauci, W. J. Collins, and R. G. Derwent Institute for Meteorology, University of Edinburgh, Edinburgh, UK Met Office, Bracknell, UK Department of Meteorology, University of Reading, UK Department of Earth Sciences, The Open(More)
We quantified the dynamics of the tree stratum at Hubbard Brook Experimental Forest (HBEF), New Hampshire, to examine why live biomass reached a plateau in about 1980. Total aboveground biomass increased from 209 Mg ha–1 in 1981 to 216 Mg ha–1 in 2001. From 1991 to 2001, in-growth of ‡10 cm diameter at breast height (DBH) trees averaged 4.7 trees ha–1 year(More)
Soil Sci. Soc. Am. J. 78:1458–1468 doi:10.2136/sssaj2014.03.0114 Received 26 Mar. 2014. *Corresponding author ( © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including(More)
Watershed 1 (W1) at the Hubbard Brook Experimental Forest in New Hampshire, with chronically low pH and acid neutralizing capacity (ANC) in surface water, was experimentally treated with calcium silicate (CaSiO3; wollastonite) in October 1999 to assess the role of calcium (Ca) supply in the structure and function of base-poor forest ecosystems. Wollastonite(More)
The X-ray photoelectron spectra of the 2p, 3s and 3p levels of iron in oxidized Clostridium pasteurianum ferredoxin indicate that the eight iron atoms in the molecule are indistinguishable. Their magnetic state is indicated both by core polarization splitting of the 3s electrons, and by "shake-up' satellites on the 2p lines. Similar satellites are observed(More)
1. The Mössbauer spectra of Scenedesmus ferredoxin enriched in (57)Fe were measured and found to be identical with those of two other plant-type ferredoxins (from spinach and Euglena) that had been previously measured. Better resolved Mössbauer spectra of spinach ferredoxin are also reported from protein enriched in (57)Fe. All these iron-sulphur proteins(More)
The Mössbauer spectra of both oxidized and reduced ferredoxin from Bacillus stearothermophilus have been analysed using computer fits to theoretical spectra obtained from a spin Hamiltonian. A consistent set of parameters was obtained from fits to spectra obtained over a wide range of temperature and magnetic field. These results are interpreted in terms of(More)