Partitioning Soil Respiration: Differentiating Root Contributions and Environmental Factors

Abstract

An essential factor for understanding root respiration, in addition to carbon dioxide emission, is the soil oxygen influx, thus the objective was to evaluate carbon dioxide (CO₂) emissions and oxygen (O₂) influx (soil respiration) in soils with and without vegetation, understanding the contribution of root respiration to total soil respiration and its correlation with meteorological variables. Monitoring took place with readings at 7, 10, 12, 15 and 17 h (system 24 h) in different environmental conditions. To design the experiment, two plots of 1m² were adopted under the conditions of bare soil and soil vegetated with grass (Paspalum Notatum). To determine the emission of CO₂ from the soil, the Li-8100 portable system was used, while the influx of O₂ from the soil was obtained by linear interpolation of the oxygen variation in the chamber using a smart oxygen sensor UV Flux 25% model CM-42,951. The data were subjected to analysis of variance for repeated measures over time. The results demonstrated that CO₂ emission and O₂ influx are higher in vegetated soil. The peak CO₂ emission and the peak oxygen influx occur between 10 and 15 h. CO₂ emission was strongly associated with soil moisture without vegetation (r = 0.76; p < 0.05) and with vegetation (r = 0.80, p < 0.05). The soil O₂ influx in the vegetated soil was associated with photosynthetically active radiation (r = 0.85, p < 0.05) and is linked to the activity of photosynthesis and consequently root respiration. The existence of root respiration and its dependence on the soil O₂ influx are concluded, as the O₂ influx is increased in vegetated soils in relation to bare soil. And finally, root respiration represented 27 to 48% of soil respiration for the evaluated scenario.