Hard to predict: synchrony in epiphytic biomass in a floodplain is independent of spatial proximity, environmental distance, and environmental synchrony

Abstract

Population synchrony occurs when local population abundances increase and decrease simultaneously over time. In terms of other characteristics that can be measured in ecosystems, such as biomass and nutrient content, intrinsic and extrinsic processes have also been used to explain synchronic variation patterns. Synchrony may clarify whether regional processes are more important than local processes. This study used epiphytic biomass data (chlorophyll-a) collected from eight locations in a floodplain over 11 years. The goal was to estimate epiphytic biomass synchrony. We anticipated that high synchrony levels would be consistent with the strong impact of floods, which affect different floodplain habitats simultaneously. This is equivalent to the Moran effect. In contrast, low synchrony levels would be consistent with the hypothesis that the high environmental heterogeneity of floodplains hampers synchrony. Our results indicated low synchrony, and its variation was not correlated with geographic or environmental distances nor with environmental synchrony. Also, regression models demonstrated low predictive power of local environmental variables in predicting biomass variation in the different sites. In addition, we performed a meta-analysis that confirms the generality of our findings. In conclusion, these results challenge the efficiency of epiphytic biomass as an ecological indicator, at least in floodplain systems.