were used to calculate mass transfer (tau) and weathering solute profiles, which in turn were used to 10 determine weathering mechanisms and to estimate weathering rates. 11Regolith formed on both lithologies is highly leached of most labile elements, although Mg 12 and K are less depleted in the granitic than in the volcaniclastic profiles, reflecting residual biotite (McDowell and Asbury, 1994; Murphy et al., 1998; White et al., 1998; Schulz and White, 1999; 99 Buss et al., 2008; 2010;Stallard, 2012; Buss et al., 2013) METHODS 6Regolith cores, approximately 10 cm diameter, were collected by hand-augering to the point of 171 refusal at 5 sites ( Fig. 1) (Fig. 1). were purged using a plastic syringe prior to sampling. Samples were taken with a gas-tight 203 apparatus attached to a needle and collected in septa-sealed gas canisters under vacuum, which were 204 7 shipped to the USGS in Menlo Park for measurement of O 2 and CO 2 by gas chromatography (GC Average estimated porosity and % water content by mass (

In order to assess the effects of critical zone processes on Mg concentrations and isotopic signatures of tropical streams, we studied a well constrained, highly weathered andesitic volcaniclastic catchment in the Luquillo Critical Zone Observatory, Puerto Rico. Our results indicate that dissolved Mg concentrations and isotope ratios in the regolith pore water are mainly controlled by rain input, with weathering inputs being more important at sites with thinner regolith (2.7 to 0.9 m deep) and at

Tropical cyclones play an increasingly important role in shaping ecosystems. Understanding and generalizing their responses is challenging because of meteorological variability among storms and its interaction with ecosystems. We present a research framework designed to compare tropical cyclone effects within and across ecosystems that: a) uses a disaggregating approach that measures the responses of individual ecosystem components, b) links the response of ecosystem components at fine temporal scales to meteorology and antecedent conditions, and c) examines responses of ecosystem using a resistance–resilience perspective by quantifying the magnitude of change and recovery time. We demonstrate the utility of the framework using three examples of ecosystem response: gross primary productivity, stream biogeochemical export, and organismal abundances. Finally, we present the case for a network of sentinel sites with consistent monitoring to measure and compare ecosystem responses to cyclones across the United States, which could help improve coastal ecosystem resilience.

The thick regolith developed in the humid tropics represents an endmember of critical zone evolution, where shallow and deep biogeochemical cycles can be decoupled in terms of the predominant source of trace elements (atmospheric input at the surface, weathering at depth) and of the processes that control their cycling. To investigate the influence of lithology on trace element behavior and in this potential decoupling, we studied two deep (9.3 and 7.5 m), highly-leached, ridgetop regolith profiles at the Luquillo Critical Zone Observatory, Puerto Rico. These profiles have comparable internal (degree of weathering, topography) and external (vegetation, climate) characteristics, but differ in their underlying bedrock (andesitic volcaniclastic and granitic). At these two sites, we analyzed a large suite of trace elements and used the rare earth elements and yttrium (REY) as tracers of critical zone processes because they are fractionated by the chemical reactions involved in weathering and pedogenesis (e.g., sorption, dissolution, colloidal transport) and by redox fluctuations. ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P TWe found that both regolith profiles show atmospheric inputs of trace elements at the surface and evidence of bedrock dissolution at depth, as expected. We also found noticeable differences in the re-distribution of trace elements and REY within the profiles, indicative of different geochemical environments with depth and lithology. In the volcaniclastic profile, trace element and REY behavior is controlled mainly by redox-mediated, sorption/desorption reactions, whereas pHcontrolled dissolution/precipitation and sorption reactions predominate in the granitic profile. The most noticeable difference between the two regolith profiles is in the long-term redox conditions, inferred from redox-sensitive elements and Ce anomaly variations, which are more variable and stratified in the volcaniclastic profile and change gradually with depth in the granitic profile. The contrasting redox conditions and the different sources of elements (dust vs. bedrock) produce a decoupling between the surface and deep geochemical environments of the volcaniclastic regolith.The difference in redox conditions between the two lithologies likely stems from the finer grain size and higher clay content of the volcaniclastic regolith.