Integrating permanent plot and palaeoecological data to determine subalpine post‐fire succession, recovery and convergence over 128 years

Abstract

AbstractAimsPost‐fire succession in low‐productivity ecosystems is rarely directly measured. We test whether taxonomic, functional, or baseline convergence has occurred 128 years after a major fire in 1890 in a low‐productivity, fire‐susceptible subalpine ecosystem. The historical plots represent one of the longest‐running quantitative ecological studies in the world.LocationArthur's Pass, South Island, New Zealand.MethodsWe remeasured historical plots at sites established 42 years after the fire, and modernised previous chart quadrat data to percentage frequency. We tested whether taxonomic and functional dissimilarity within the site, and within environmentally similar transect groups, reduced over time. We used pollen data preserved in soil cores taken on the plots to test whether the site had returned to the reference pre‐fire baseline.ResultsThere is little evidence of taxonomic convergence across the site and dissimilarity remains high. Functional dissimilarity showed little reduction or evidence of convergence. Within maximally similar groups of transects, taxonomic and functional dissimilarity declined over time. Tree frequency increased significantly year‐on‐year. There is a lack of convergence with the pre‐fire baseline, accompanied by a reduction in the proportion of tree pollen represented on most transects.ConclusionsThe taxonomic rate of successional change has yet to slow, and a steady state has yet to be reached, suggesting it is too early to consider the site has attained maximal convergence. Palaeoecological data have allowed quantification of the effect of a novel fire regime to which the ecosystems are poorly adapted: we found compositional, structural, and dominant‐species differences between pre‐ and post‐fire vegetation. Combining permanent transects and palaeoecological data allows for a synthesis of data at multiple time scales, permitting investigations of long‐duration successions.