Disturbance reshapes the productivity–diversity relationship

Abstract

AbstractQuestionWe evaluated the effect of disturbance on the productivity–diversity relationship in a long‐term monitoring study. We asked whether the same productivity–diversity relationship applies to 12 years of pre‐fire (undisturbed) conditions and to eight years of post‐fire succession studied in the same plots.LocationBugac, Kiskunság, Central Hungary.MethodsWe studied 20 permanent plots for 20 years in grassland patches of a forest–steppe vegetation complex, 12 years before (2000–2011), and eight years after (2012–2019) a severe wildfire. The cover values of each vascular plant species were visually estimated each year. We used total cover as a proxy for productivity and species richness as a measure of diversity. We assessed changes in the productivity–diversity relationship before and after the disturbance event. Temporal changes of the pre‐fire and post‐fire relationship were analysed separately by generalized estimation equations in the R environment.ResultsIn the pre‐fire period, we found a positive linear productivity–diversity relationship, and no time effect. However, in the post‐fire period, we found a unimodal relationship, which changed gradually from year to year. The disturbance event moved the vegetation out of a stable state, increased the range of both productivity and diversity, and resulted in a decreasing linear component of the relationship after the fire. Our results provide a striking example of the influence of succession on the shape of the productivity–diversity relationship.ConclusionsDisturbance may create considerable and long‐lasting changes in the productivity–diversity relationship of formerly stable communities. The changing shape of the productivity–diversity relationship over time after disturbance suggests that the evaluation of broad‐scale productivity–diversity relationships should control for disturbance history.