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

© 2023 Global Journals Volume XXIII Issue VI Version I 15 ( ) Global Journal of Human Social Science - Year 2023 B Evaluating Soil Carbon Efflux Responses to Soil Moisture and Temperature Variations in Brazilian Biomes The annual averages of the soil carbon efflux were 6.52 ± 2.31, 2.12 ± 0.81, and 5.91 ± 2.03 for the Ecotone, the Cerrado, and the Pantanal forests, respectively. Additionally, there was no significant statistical difference ( p < 0.05) between the flows in the Cerrado-Amazonian Ecotone and the Pantanal forests. Maximum emissions (9.96 and 4.19 µmolm -2 s -1 , respectively) were observed in March 2018 to the Ecotone and Cerrado, and the maximum emission (8.37 µmolm -2 s -1 ) was observed in December 2014 to Pantanal, The litter production values for Pantanal and the Ecotone, as well as those for Cerrado and the Ecotone, were found to be statistically different (p < 0.05). However, the values corresponding to the Cerrado and Pantanal forests did not exhibit a significant difference. In September, both the Ecotone and Cerrado forests displayed their highest litter production, at approximately 0.325 kgm -2 and 0.15 kgm -2 , respectively. It is noteworthy that the Ecotone and Cerrado forests produced the highest litter amounts during this month. In a study by Costa et al. (2022), it was reported that the dense Cerrado, exhibiting characteristics closer to the ecotone, had a monthly average litter production of 0.37 kgm - ². In the Pantanal, the highest level of litter production (0.10 kgm -2 ) was observed in August 2014, values close to those found by Pinto Jr. et al. (2018) for the same month and biome. August and September months were considered as dry periods (Vourlitis and da Rocha, 2011), during which the plants in deciduous forests loose leaves the most as a result of water stress (Pavão et al., 2018), justifying these results. This pattern was found to be reversed for the leaf area index (LAI), which as the rain starts, increases owing to the production of new leaves (Novais et al. 2018b), and corresponding to a significant positive correlation coefficient ( p < 0.01), i.e., 0.74 and 0.84 for LAI and precipitation in Cerrado and the Cerrado- Amazonian Ecotone, respectively. There was a statistically significant difference ( p < 0.001) between the LAI results for the Cerrado and Ecotone, 4.64 ± 1.38 and 7.6 ± 1.92 m 2 .m -2 respectively. The average annual soil temperature and soil moisture for Cerrado, Pantanal, and the Ecotone were 25.08 ± 3.40 ºC and 10.60 ± 4.61%, 26.37 ± 2.13 ºC and 13.52 ± 5.62%, and 23.88 ± 1.35 ºC and 11.30 ± 5.73%, respectively. Correlation analysis showed that there was a positive and significant correlation between soil moisture and efflux in Cerrado and Pantanal ( ρ = 0.755 and p = 0.003; ρ = 0.629 and p = 0.0263, respectively), and the correlation with soil temperature was not significant. However, for the Ecotone, a positive and significant correlation was observed between the efflux and soil temperature ( ρ = 0.893 and p < 0.001), while that between soil moisture and the efflux was insignificant ( ρ = 0.683). b) Models According Table 1, the regression models were set up from a combination of environmental variables or/and vegetation parameters. Pantanal - Regression Model: = 2 + � 0.2 � 2.5 Parameters Value p-value R² a 0.011 < 0.001 0.745 b -134.44 < 0.001 Ecotone - Regression model: = 2.4 + � � 0.4 + 0.4 Parameters Value p-value R² a 0.00235 < 0.05 b -5.2436 < 0.05 0.832 c 1.0048 < 0.01 Cerrado - Regression model: = 0.25 + 1.25 0.25 + −3 Parameters Value p-value R² a 0.5654 < 0.001 b 0.0655 < 0.05 0.916 c 2.20E-08 < 0.001 AI = leaf area index; Ts = soil temperature; = soil moisture; I S = LAI/S; S I = S/LAI * L