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An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The western San Bernardino Mountains have received one of the highest loads of atmospheric nitrogen (N) deposition in North America over the past 50 years because of fossil fuel combustion in the adjacent Los Angeles Basin. Further to the east, areas with the same vegetation, soil type, and climate remain less polluted, creating an ideal setting in which to observe the effects of N fertilization on storage and turnover of soil carbon (C). In this study, I examined the response of soil carbon cycling to N deposition by measuring the ∆14C signature of soil fractions from two sites along an air pollution gradient in the San Bernardino Mountains. The polluted site's labile fraction turnover times were decreased on average by 20 years in the O horizon and by 50 years in the A horizon in comparison to the unpolluted site. Recalcitrant fraction turnover times increased by 50 years in the O horizon and 80 years in the A horizon. These results suggest that high level, long term N fertilization accelerates decomposition in labile soil fractions and slows decomposition of recalcitrant fractions. Additionally, N fertilization may be responsible for an order of magnitude reduction in C storage of multidecadal- cycling pools observed at the polluted site.

The problem of kaleidoscopically tiling a surface by congruent triangles is equivalent to finding groups generated in certain ways. In order to admit a tiling, a group must have a specific set of generators as well as an involutary automorphism, µ, that acts to reverse the orientation of the tiles. The purpose of this paper is to explore group theoretic and computational methods for determining the existence of symmetry groups and tiling groups, as well as to classify the symmetry and tiling groups on hyperbolic Riemann surfaces of genus 6 and 7.