The first case represents a biologically true case where the absolute abundance matches the relative abundance observations. There are no changes in biomass from t1 to t2 and species A increases, whereas species B decreases. The second case represents a case where there is an overall increase in biomass from t1 to t2 caused by an absolute increase in species B and no absolute changes in species A. Species A would then appear to have reduced its relative abundance levels, when in fact that was caused by a change in species B alone. The third case represents an opposite scenario case where there is a total decrease in biomass from t1 to t2 caused by a decrease in species B and no changes in species A. Again, in a relative abundance plot, species B would appear to have decreased its relative abundance levels (true), but inferences regarding species A would be false. The fourth case represents a case where there is a general increase in biomass from t1 to t2 prompted by increases in absolute abundances of both species A and B. The fifth case represents an opposite scenario where there is a general decrease in biomass from t1 to t2 caused by decreases in absolute abundances of both species A and B. In these last two cases, as long as the proportion between the two species stays the same, the relative abundance plot reflects biological changes.  
Novel tools such as HiPR-FISH could allow for high-phylogenetic-resolution microbiome mapping in soil samples in the future \cite{Shi_2020} but go beyond the scope of the soil microbiome studies addressed in this perspective article.
For example, processes in the rhizosphere including changes to the community are expected to occur at higher rates than in bulk soil (REFs). 
In a forest soil the temporal dynamics including microbial turnover most likely differ from an agricultural soil,