Global Journal of Human-Social Science, B: Geography, Environmental Science and Disaster Management, Volume 23 Issue 6

Evaluating Soil Carbon Efflux Responses to Soil Moisture and Temperature Variations in Brazilian Biomes © 2023 Global Journals Volume XXIII Issue VI Version I 11 ( ) Global Journal of Human Social Science - Year 2023 B Jonathan Willian Zangeski Novais α , Fernando da Silva Sallo σ , Maria Aparecida Pereira Pierangelli ρ , Osvaldo Borges Pinto Junior Ѡ , Danielle da Silva Batista ¥ & Levi Pires de Andrade § Abstract- Changes in soil moisture and temperature can directly influence soil carbon emissions, which can add carbon to the atmosphere and make the greenhouse effect more intense. In this sense, research is needed that contributes to this knowledge and that simulates future scenarios, allowing actions to be taken in advance. Thus, an experiment was set up in which carbon dioxide efflux was collected over a period of one year in three Brazilian biomes, Cerrado, Pantanal, and Cerrado-Amazonian Ecotone, and to verify the influence of soil moisture, leaf area index and litter, multiple regression models were carried out. Correlation analyses were performed, and subsequently, sensitivity analyses were conducted for possible efflux increases owing to 2 ºC and 10% decreases or increases in soil temperature and moisture, respectively, simulating possible climate change scenarios. The results showed that of the three study areas, the Cerrado forest was most resistant to changes in these variables, and the correlation between the carbon efflux and the variables, soil temperature and moisture, were positive and significant for Cerrado and Pantanal. However, for the Cerrado- Amazonian Ecotone, only the correlation between the efflux and soil temperature was positive and significant. Additionally, the Cerrado-Amazonian Ecotone was the most sensitive to soil temperature variations, while the Pantanal forest, which showed a 26% increase in emissions owing to a 10% increase in soil moisture content, was the most sensitive to soil moisture variations, highlighting how global warming can interfere with carbon balance. Moreover, the biomes examined in this study present a complex mosaic landscape, with various regions exhibiting distinct responses to climate change. This underscores the importance of alerting government officials and emphasizes the necessity for proactive measures to mitigate soil CO2 emissions. The rise in atmospheric carbon content contributes to the greenhouse effect, reinforcing the urgency of addressing and curbing these emissions. Keywords: soil carbon efflux, soil temperature, soil moisture, forests, climate change. I. I ntroduction ver the years, there has been a rapid increase in the number of ecosystem warming-related experiments, covering almost all terrestrial biomes, and the results of these studies provide relevant understanding regarding global soil respiration patterns owing to a warming climate (Wang et al., 2014), in that soil respiration plays a crucial role in regulating carbon cycling in terrestrial ecosystems and the atmospheric carbon dioxide (CO 2 ) concentration (Yang et al., 2022), and respiratory effluxes of carbon from the soil to the atmosphere are expected to rise with temperature, potentially intensifying future climate warming (Yan et al., 2022). Carbon cycling in ecosystems occurs depending on the balance between CO2 fixation by plants and losses from respiration or physical removal from the soil. This is contingent on gross primary production and litter decomposition over time (Strong et al., 2017). Additionally, it is influenced by the underground environment, encompassing factors such as root biomass (Søe and Buchmann, 2005) and soil microbial biomass (Neergaard et al., 2002). Therefore, to understand the global carbon cycle, it is necessary to identify the factors that interfere with soil carbon dynamics (Neff and Hooper, 2002). Reportedly, it is expected that average global temperatures will rise 2–6 ºC by the end of the century (IPCC, 2007), and this increase may alter soil respiration. Kirshbaum (1995) reported that a rise in temperature by 1 ºC can bring about a 10% increase in carbon emission in regions where the annual mean temperature is 5 ºC. The effect of soil temperature on carbon dioxide efflux has been sufficiently reported (Bond-Lamberty and Thomson, 2010a; Mahecha et al., 2010), and it is well established that temperature increases can stimulate microbial activity. However, for tropical ecosystems, soil moisture has also been identified as a factor that can affect soil carbon dynamics (Davidson et al., 2000; Adachi, 2006), with peak emissions being recorded at the beginning of the wet period (Chou et al., 2008; Borken and Matzner, 2009; Bowling et al., 2011; Nielsen and Ball, 2015; Wang et al., 2019) justified the need for forecast models, based on climate change scenarios. Soils represent the most significant carbon store in the world (1500 Gt, e.g. 1.5×10 21 g). According to the European Commission (2006), tropical forests contain large amounts of C in vegetation and soil, equivalent to 37% of the global terrestrial C pool (Dixon et al., 1994). In this light, there are several biomes in the Brazilian territory, where it is necessary to evaluate these carbon emissions and the possible variables that influence them. The Amazon rainforest occupies an area O Author α Ѡ ¥ : Master's Program in Environmental Sciences, Cuiabá University – UNIC. e-mails: _jonathan.novais@kroton.onmicrosoft.com , osvaldo.borges@cogna.com.br , danielle.batista@unemat.br Author σ § : Federal Institute of Mato Grosso – IFMT. e-mails: fernando.sallo@ifmt.edu.br, levi.pires@hotmail.com Author ρ : State University of Mato Grosso – UNEMAT. e-mail: mapp@unemat.br