Temporal shifts in the interaction between woody resprouters and an obligate seeder tree during a post-fire succession in Patagonia

LANDESMANN, J.B.; GOWDA, J.H.; KITZBERGER, T.

JOURNAL OF VEGETATION SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016

1100-9233

Question: The study of temporal variation of plant?plant interactions hasreceived little attention despite its importance in community dynamics. Succes-sional processes triggered by disturbances such as fire may be determined bychanges in key interactions between dominant woody plants. Taking advantageof a 95-yr-old post-fire natural experiment we assessed temporal shifts inpost-fire interactions between woody resprouters and the obligate seeder treeAustrocedrus chilensis. We hypothesized that during the initial post-fire period,resproutersmay facilitate A. chilensis tree growth, while at advanced time since firethe interaction between A. chilensis trees and resprouters may turn to competition.Location: Northwestern Rıo Negro province, Patagonia, Argentina.Methods: We selected pairs of A. chilensis trees and woody resprouters growing80 cm apart (growing in association) and both A. chilensis trees and resproutersgrowing at more than 3 m apart from any individual (controls). We cored allindividuals, measured ring widths and calculated basal area increment (BAI)and the relative interaction index (RII).Results: During mid-early stages of post-fire succession, A. chilensis trees BAIwas suppressed for at least 15 yr when growing in association with resprouters,and accordingly displayed a negative RII. Strikingly, during the same period,resprouters associated with A. chilensis trees showed higher BAI than controlresprouters, and a positive RII. At advanced time since fire, RII showed a neutralinteraction, and according to model estimations, the BAI of A. chilensis trees inassociation may eventually exceed control BAI whereas resprouter BAI in asso-ciation may decline earlier than that of the controls. Interestingly, A. chilensistrees and resprouter growth was less correlated with climate when growing inassociation than when growing in isolation.Conclusions: Competition of resprouters over A. chilensis tree growth duringintermediate post-fire stages may be slowing the successional process. However,the association appears to be at the same time mutually beneficial as it buffersagainst adverse climatic conditions. Studying how plant growth varies along thesuccession is essential to understand community functioning and to predict pos-sible alterations associated with changes in disturbance regimes due to climatechange.