Effect of Fungus-Growing Termite on Soil CO2 Emission at Termitaria Scale in Dry Evergreen Forest, Thailand

Termites are one of the major contributors to high spatial variability in soil respiration. Although epigeal termite mounds are considered as a point of high CO2 effluxes, the patterns of mound CO2 effluxes are different, especially the mound of fungus-growing termites in a tropical forest. This study quantified the effects of a fungus-growing termite (Macrotermes carbonarius) associated with soil CO2 emission by considering their nesting pattern in dry evergreen forest, Thailand. A total of six mounds of M. carbonarius were measured for CO2 efflux rates on their mounds and surrounding soils in dry and wet seasons. Also, measurement points were investigated for the active underground passages at the top 10% of among efflux rates. The mean rate of CO2 emission from termitaria of M. carbonarius was 7.66 µmol CO2/m2/s, consisting of 2.94 and 9.11 µmol CO2/m2/s from their above mound and underground passages (the rate reached up to 50.00 µmol CO2/m2/s), respectively. While the CO2 emission rate from the surrounding soil alone was 6.86 µmol CO2/m2/s. The results showed that the termitaria of M. carbonarius contributed 8.4% to soil respiration at the termitaria scale. The study suggests that fungus-growing termites cause a local and strong variation in soil respiration through underground passages radiating out from the mounds in dry evergreen forest.

Soil CO2 emission in ‘Tifton 85’ bermudagrass pasture fertilized with liquid pig slurry

The application of liquid pig slurry (LPS) to pastures offers potential as a fertilizer but could have a direct influence on soil CO2 emissions. This study evaluated soil carbon dioxide emissions after successive LPS applications to soils under pasture cultivation. The experiment was carried out on ‘Tifton-85’ bermudagrass pasture cultivated in a red-yellow oxisol soil in the municipality of Lucas do Rio Verde-MT, Brazil. Two treatments were evaluated: the control and an application of 20 m3 ha-1 of LPS after each cut of the pasture. The CO2 emissions from the soil were determined using a high-precision infrared gas analyzer. Soil temperature and soil moisture were determined as were micrometeorological variables. The application of LPS had a significant effect on soil C-CO2 flow. The average flow of C-CO2 from the soil for the control treatment and with the application of LPS was 0.236 g C-CO2 m-2 h-1 and 0.291 g C-CO2 m-2 h-1, respectively. The application of LPS increased the accumulated CO2 emissions from the soil by 23.2%. Soil temperature and moisture are the main factors regulating the process of soil CO2 emission. These factors therefore need to be considered when evaluating the impact of LPS application on greenhouse gas emissions

Does Biochar Influence Soil CO2 Emission Four Years After Its Application to Soil?

Biochar application into soil has potential as a means for reducing soil greenhouse gas emissions and climate mitigation strategy. In this study, we evaluated the impact of two doses of biochar (10 and 20 t.ha−1) applied in 2014, combined with three fertilization levels (N0, N1, N2) on carbon dioxide (CO2) in field conditions during the growing season (April – October) in 2018. The field site is located in the Nitra region of Slovakia – Malanta. The soil in the field was classified as a silt loam Haplic Luvisol. There was not found any statistically significant (P <0.05) decreasing effect of biochar with or without N-fertilizer after four years of its application on average daily and cumulative CO2 emissions, while the CO2 emissions increased with additional N-fertilizer. Biochar decreased (insignificantly) the daily and cumulative CO2 emissions only in the treatments without N-fertilization and in the treatment fertilized with higher level of biochar application (20 t.ha−1) and N-fertilizer (80 kg.N.ha−1). According to these results it can be concluded that the biochar applied to soil is not able to reduce CO2 emissions after four years of its application when it is combined with usual agriculture practices which include N-fertilization.

Elevated Tropospheric Ozone Concentration Alters Soil CO2 Emission: A Meta-Analysis

Elevated tropospheric ozone (O3) concentration may substantially influence the below-ground processes of terrestrial ecosystems. Nevertheless, a comprehensive and quantitative understanding of O3 impacts on soil CO2 emission remains elusive, making the future sources or sinks of soil C uncertain. In this study, 77 pairs of observations (i.e., elevated O3 concentration treatment versus control) extracted from 16 peer-reviewed studies were synthesized using meta-analysis. The results depicted that soil CO2 efflux was significantly reduced under short-term O3 exposure (≤1 year, p < 0.05), while it was increased under extended duration (>1 year, p < 0.05). Particularly, soil CO2 emission was stimulated in nonagricultural ecosystems, in the free-air CO2 enrichment (FACE) experiment, and in the soils of lower pH. The effect sizes of soil CO2 efflux were significantly positively correlated with experimental duration and were significantly negatively correlated with soil pH, respectively. The ozone effect on soil CO2 efflux would be enhanced at warm temperatures and high precipitation. The duration of O3 exposure was the fundamental factor in analyzing O3 impacts on soil CO2 emission.