## 4 Discussion  
Here, we compare differences in the mean and seasonal distribution of \(\mathrm{SIF_{d}}\) for the country of Brazil by biome and vegetation classes within biomes. The results of our analyses and significant interaction between vegetation class and biome demonstrates that average values for vegetation classes should consider the biomes in which they occur. Furthermore, average values (Figure 4) do not capture important seasonal dynamics (Figures 5 and 6), which show that high mean values can result from low rates of productivity over a longer period of time or high seasonal pulses that may be brief (Figure 5, Figures S12 and S13). Through an examination of differences in mean and seasonality of \(\mathrm{SIF_{d}}\) from satellite we were able to construct a more complete picture of vegetation photosynthetic activity of regions in Brazil as captured by OCO-2, a satellite-based instrument. In the Amazon, we found that mean \(\mathrm{SIF}\) for the biome was highest and variation of \(\mathrm{SIF_{d}}\) lowest of all other biomes, which was not surprising based on our understanding of the effects of biomass and chlorophyll content on vegetation remote sensing measurements. To our knowledge, however, no studies have previously shown these results. Mean \(\mathrm{EBF\ SIF_{d}}\) was highest of vegetation classes within the Amazon and highest of \(\mathrm{EBF\ SIF}\) in all biomes. Positive correlations between mean \(\mathrm{GRA}\), \(\mathrm{SAV}\), and \(\mathrm{WSAV\ SIF}\) and \(\mathrm{T_{can}}\), \(\mathrm{T_{air}}\), and \(\mathrm{VPD}\) were found in the Amazon and the strongest correlations were with \(\mathrm{VPD}\), indicating that a higher \(\mathrm{VPD}\) is correlated with higher \(\mathrm{SIF_{d}}\) for these classes. However, a lack of correlation of \(\mathrm{DBF}\) and \(\mathrm{EBF\ SIF}\) with \(\mathrm{T_{can}}\), \(\mathrm{T_{air}}\), and \(\mathrm{VPD}\) may be attributed to the relatively small range of values for \(\mathrm{SIF_{d}}\), \(\mathrm{T_{can}}\), \(\mathrm{T_{air}}\), and \(\mathrm{VPD}\) for \(\mathrm{DBF}\) and \(\mathrm{EBF}\) in the Amazon. Looking at seasonal metrics shows \(\mathrm{SIF_{d}}\) seasonal dynamics in the Amazon that are masked by analysis of mean \(\mathrm{SIF_{d}}\). Although Amazon \(\mathrm{EBF}\) had the highest mean \(\mathrm{SIF_{d}}\) than any other vegetation class in all biomes, investigating the seasonality of \(\mathrm{SIF}\) revealed that the Pantanal had a stronger seasonal pulse of integrated \(\mathrm{SIF_{d}}\), higher total integrated \(\mathrm{SIF_{d}}\) and the longest growing season length. In contrast, Amazon forests remained productive throughout the year (based integrated \(\mathrm{SIF_{d}}\)) with little seasonality (pulse integrated \(\mathrm{SIF_{d}}\)). Overall, values for \(\mathrm{VPD}\) in the Amazon were the lowest of the biomes in the study, just behind the Pampa, and \(\mathrm{T_{can}}\) and \(\mathrm{T_{air}}\) were relatively  
Figure 6: Total integrated \(\mathrm{SIF_{d}}\) versus length of season with generalized linear model represented (black line) and gray region represents 95% confidence interval (adjusted \(\mathrm{R^{2}}=0.30\), intercept \(=0.68\), slope \(=0.01\), \(p<0.01\)). moderate, which indicates the most favorable photosynthetic conditions and is supported by the high rates of base integrated SIF relative to other biomes and higher base integrated SIF\({}_{\text{d}}\) for the Amazon found in the study (Figure 5, Figures S8-S10). For the Atlantic Forest, mean SIF\({}_{\text{d}}\) for the biome was not different from the Cerrado, Pampa, or Pantanal. Mean EBF SIF\({}_{\text{d}}\) was higher than other vegetation classes in the Atlantic Forest and was correlated positively with T\({}_{\text{can}}\), T\({}_{\text{air}}\), and VPD, and the strongest of these was with T\({}_{\text{air}}\).