SummaryÐCarbon dioxide and methane are important greenhouse gases whose exchange rates between soils and the atmosphere are controlled strongly by soil temperature and moisture. We made a laboratory investigation to quantify the relative importance of soil moisture and temperature on¯uxes of CO 2 and CH 4 between forest soils and the atmosphere. Forest¯oor and mineral soil material were collected from a mixed hardwood forest at the Harvard Forest Long-Term Ecological Research Site (MA) and were incubated in the laboratory under a range of moisture (air-dry to nearly saturated) and temperature conditions (5±258C). Carbon dioxide emissions increased exponentially with increasing temperature in forest¯oor material, with emissions reduced at the lowest and highest soil moisture contents. The forest¯oor Q 10 of 2.03 (from 15±258C) suggests that CO 2 emissions were controlled primarily by soil biological activity. Forest¯oor CO 2 emissions were predicted with a multiple polynomial regression model (r 2 =0.88) of temperature and moisture, but the ®t predicting mineral soil respiration was weaker (r 2 =0.59). Methane uptake was controlled strongly by soil moisture, with reduced¯uxes under conditions of very low or very high soil moisture contents. A multiple polynomial model accurately described CH 4 uptake by mineral soil material (r 2 =0.81), but only weakly (r 2 =0.45) predicted uptake by forest¯oor material. The mineral soil Q 10 of 1.11 for CH 4 uptake indicates that methane uptake is controlled primarily by physical processes. Our work suggests that inclusion of both moisture and temperature can improve predictions of soil CO 2 and CH 4 exchanges between soils and the atmosphere. Additionally, global change models need to consider interactions of temperature and moisture in evaluating e ects of global climate change on trace gas¯uxes. #
We measured CO2, N2O, and CH4 fluxes between soils and the atmosphere in ambient and N‐addition plots at a productive black cherry‐sugar maple forest in northwest Pennsylvania to examine the link between N‐cycling and trace gas fluxes. Fluxes were estimated the using in‐situ chambers. Net annual N mineralization was 121.0 kg N ha−1yr−1, and net nitrification was 85.8 kg N ha−1 yr−1, or 71% of net mineralization. Carbon dioxide (5.09 Mg C ha−1 yr−1) efflux and CH4 uptake (8.90 kg C ha−1 yr−1) were among the highest rates reported for temperate deciduous forests. Emissions of N2O (0.228 kg N ha−1 yr−1) were within the range of rates reported elsewhere, including locations with lower rates of N‐cycling. A short‐term study (May–Oct.) showed that N fertilization reduced both CO2 emissions and CH4 uptake (CO2 by 19%; CH4 by 24%). N2O effluxes in fertilized plots were not different from control plots. The relatively high rate of soil respiration corresponded to a high rate of N‐cycling; however, N2O emissions were not substantially greater than those measured at other locations, suggesting that rapid N‐cycling or N additions in temperate forests do not necessarily result in large emissions of N2O. Concurrent rapid rates of N‐cycling and high rates of CH4 uptake did not support the hypothesis that N‐cycling rates directly control CH4 uptake. Links between N‐cycling and CH4 oxidation are complex; the influence of N‐cycling on flux rates must consider not only the rate of cycling, but also the disposition of N‐cycling products, and the factors that influence rates of N dynamics.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.