Climate sensitive tree growth modelling of Myrocarpus frondosus in Southern Brazil using tree-ring time series and distributed generalized additive lag models

Abstract

Climate change is expected to strongly affect the functioning of tropical and subtropical forest ecosystems around the globe, and tree-ring analysis is proving increasingly useful for understanding the changing dynamics in these environments. However, traditional dendroecological methods were not originally designed to jointly consider inter-annual and inter-tree variations, often assuming linear growth-climate relationships, and limiting the potential to address in-deep questions regarding the tree growth sensitivity to environmental drivers. In the present study, we applied a flexible generalized additive model to assess the climate-sensitivity of the species Myrocarpus frondosus Allemão growing in a subtropical Atlantic Forest (AF) site in southern Brazil. Tree-ring width time series from 117 stem cores together with monthly climate data of temperature and precipitation covering the period from 1968 to 2021 were used for model construction. The model was designed to simultaneously encompass detrending, to capture nonlinear effects of climate variables and their interactions and to predict mean tree-ring widths for the species. Based on a distributed lag model approach, we also tested the influence of different lengths of lagged climate series over the model accuracy. Both precipitation and temperature proved to be strong drivers of M. frondosus radial growth in the subtropical AF. An interaction effect between these regressor variables revealed a likely water stress scenario arising from warm and dry summer conditions, with strongly negative impacts for the species. Detrimental impacts on tree dormancy period can also be expected due to milder winters, with legacy effects on the radial increments across two subsequent years. In addition to monitoring, the approach applied here meets the needs for more robust predictions of the impacts of future climate conditions on species and communities, contributing to efforts aimed at the management and conservation in tropical and subtropical ecosystems, particularly in the AF.