Abstract
The oxidative ratio (OR) of organic material integrates the ratio of CO2 sequestered in biomass vs. O2 produced over longer timescales, but the temporal and spatial variability within a single ecosystem has received very limited attention. Between October 2017 and October 2019, we repeatedly sampled leaves, twigs, bark, outer stem wood, understorey vegetation and litter in a temperate beech forest close to Leinefelde (Germany) for OR measurements across a seasonal and spatial gradient. Plant component OR ranged from 1.004 ± 0.010 for fine roots to 1.089 ± 0.002 for leaves. Inter- and intra-annual differences for leaf and twig OR exist, but we found no correlation with sampling height within the canopy. Leaf OR had the highest temporal variability (minimum 1.069 ± 0.007, maximum 1.098 ± 0.002). This was expected, since leaf biomass of deciduous trees only represents the signal of the current growing season, while twig, stem and litter layer OR integrate multiple years. The sampling years 2018 and 2019 were unusually hot and dry, with low water availability in the summer, which could especially affect the August leaf OR. Total above-ground OR is dominated by the extremely stable stem OR and shows little variation (1.070 ± 0.02) throughout the two sampling years, even when facing extreme events.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
It is no surprise that average above-ground ecosystem oxidative ratio (OR) is very close to average stem OR
Ecosystem OR is dominated by stem wood OR and is stable within a period of several years represented in the stem cores
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Land ecosystems play an important role in the global carbon cycle. Due to constant exchange with the biosphere via processes like respiration and assimilation, atmospheric carbon dioxide (CO2 ) and oxygen (O2 ) concentrations are subject to continuous temporal and spatial variation [1,2,3]. One key method to estimate the land carbon sink uses relative changes of O2 and CO2 concentrations in the atmosphere [3]. One of the parameters in this approach is the O2 :CO2 ratio of the land biosphere exchange with the atmosphere [3]
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