Long-term annual burning of grassland increases CO 2 emissions from soils

Abstract

Grasslands have potential to mitigate against climate change because of their large capacity to store soil organic carbon (SOC). However, the long-term impact of grassland management such as burning, which is still common in many areas of the world, on SOC is still a matter of debate. The objective of this study was to quantify the longterm effects of annual burning on CO 2 output from soils and SOC stocks. The study was performed on a 62 years old field trial comparing annual burning (AB) to no burning associated with tree encroachment (NB), and to annual mowing (AM) with all treatments laid out in randomized block design with three replicates per treatment. CO 2 emissions from soil were continuously measured over two years and were correlated to soil chemical and physical properties. AB and AM produced 30 and 34% greater CO 2 emissions from soil than NB (1.80 ± 0.13 vs. 2.34 ± 0.18 and 2.41 ± 0.17 g C-CO 2 m −2 d −1 for NB, AB and AM respectively). AB and AM also produced greater CO 2 emissions from soil and per gram of soil carbon (1.32 ± 0.1 and 1.35 ± 0.1 mg C-CO 2 g C −1 d −1 , respectively) than NB (1.05 ± 0.07 mg C-CO 2 g C −1 d −1), which corresponded to significant differences of respectively 26% and 29%. Overall, CO 2 emissions from soil (per m 2) significantly increased with soil water content (r = 0.72) followed by SOC stocks (r = 0.59), SOC content (r = 0.50), soil bulk density (r = 0.49), soil temperature (r = 0.47), C:N ratio (r = 0.46) and mean weight diameter (r = 0.38). These findings suggest that long-term annual burning increases CO 2 output from soils. Additional greenhouse gases emissions from burning itself and alternative grassland management techniques were finally discussed.

Aggregation, carbon, and total soil nitrogen in crop-livestock-forest integration in the Eastern Amazon

“…Soil aggregation contributes to the increase in aggregate diameter, and C and N stocks in the soil; and minimizes the changes in the carbon cycle that are influenced by the availability of nitrogen from soil (Zhu et al, 2017), because the greater the aggregation, the lower the flow of CO 2 from the soil (Abdalla et al, 2016).…”

Ecological Effects of Grazing in the Northern Tianshan Mountains

“…Grassland ecosystems serve important economic and ecological functions, such as material production, climate regulation, soil and water conservation, sand stabilization, soil improvement and biodiversity preservation [1][2][3]. However, grassland ecosystems are easily susceptible to disturbances and highly vulnerable to climate change and human activities, particularly in arid areas [4][5][6][7].…”

Long‐term (64 years) annual burning lessened soil organic carbon and nitrogen content in a humid subtropical grassland

“…Therefore, the present study investigated the proportion of aggregate fractions and the SOC and N content associated with these fractions in a long-term grassland experiment established in 1950 at the Ukulinga research farm in South Africa. The obtained SOC data were correlated to soil CO 2 emissions measured at the same site by Abdalla et al (2016) to address the potential effect of SOC in different aggregate fractions on soil CO 2 emissions. The study hypothesized that first, long-term annual burning would decrease aggregate stability, and C and N pools in the soils compared to annual mowing and undisturbed grassland because the combustion of aboveground biomass and litter reduces fresh C input to soils.…”