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Full-Text Articles in Life Sciences
Environmental Forcing Does Not Induce Diel Or Synoptic Variation In The Carbon Isotope Content Of Forest Soil Respiration, Steven J. Hall, D. R. Bowling, J. E. Egan
Environmental Forcing Does Not Induce Diel Or Synoptic Variation In The Carbon Isotope Content Of Forest Soil Respiration, Steven J. Hall, D. R. Bowling, J. E. Egan
Steven J. Hall
Recent studies have examined temporal fluctuations in the amount and carbon isotope content (δ13C) of CO2 produced by the respiration of roots and soil organisms. These changes have been correlated with diel cycles of environmental forcing (e.g., sunlight and soil temperature) and with synoptic-scale atmospheric motion (e.g., rain events and pressure-induced ventilation). We used an extensive suite of measurements to examine soil respiration over 2 months in a subalpine forest in Colorado, USA (the Niwot Ridge AmeriFlux forest). Observations included automated measurements of CO2 and δ13C of CO2 in the soil efflux, the soil gas profile, and forest air. There …
Lignin Decomposition Is Sustained Under Fluctuating Redox Conditions In Humid Tropical Forest Soils, Steven J. Hall, Whendee L. Silver, Vitaliy I. Timokhin, Kenneth E. Hammel
Lignin Decomposition Is Sustained Under Fluctuating Redox Conditions In Humid Tropical Forest Soils, Steven J. Hall, Whendee L. Silver, Vitaliy I. Timokhin, Kenneth E. Hammel
Steven J. Hall
Lignin mineralization represents a critical flux in the terrestrial carbon (C) cycle, yet little is known about mechanisms and environmental factors controlling lignin breakdown in mineral soils. Hypoxia is thought to suppress lignin decomposition, yet potential effects of oxygen (O2) variability in surface soils have not been explored. Here, we tested the impact of redox fluctuations on lignin breakdown in humid tropical forest soils during ten-week laboratory incubations. We used synthetic lignins labeled with 13C in either of two positions (aromatic methoxyl or propyl side chain Cb) to provide highly sensitive and specific measures of lignin mineralization seldom employed in …
Large Fluxes And Rapid Turnover Of Mineral-Associated Carbon Across Topographic Gradients In A Humid Tropical Forest: Insights From Paired 14c Analysis, Steven J. Hall, G. Mcnicol, T. Natake, W. L. Silver
Large Fluxes And Rapid Turnover Of Mineral-Associated Carbon Across Topographic Gradients In A Humid Tropical Forest: Insights From Paired 14c Analysis, Steven J. Hall, G. Mcnicol, T. Natake, W. L. Silver
Steven J. Hall
It has been proposed that the large soil carbon (C) stocks of humid tropical forests result predominantly from C stabilization by reactive minerals, whereas oxygen (O2) limitation of decomposition has received much less attention. We examined the importance of these factors in explaining patterns of C stocks and turnover in the Luquillo Experimental Forest, Puerto Rico, using radiocarbon (14C) measurements of contemporary and archived samples. Samples from ridge, slope, and valley positions spanned three soil orders (Ultisol, Oxisol, Inceptisol) representative of humid tropical forests, and differed in texture, reactive metal content, O2 availability, and root biomass. Mineral-associated C comprised the …