Predicting seedling development for two commercial forest species under current and future climates: A multi-model assessment

Abstract

Development models are tools that couple environmental effects on development, allowing to predict development dynamics and to quantify the seedling phase duration for forest species under current and future climate conditions. Unfortunately, studies on forest species are scarce, even for commercially important species. This study calibrates and evaluates two development models under current climate conditions, and identifies possible changes in future climate conditions on the development of Corymbia citriodora (Hook.) (K.D. Hill & L.A.S. Johnson) and Eucalyptus urophylla (S.T. Blake), which are widely used in Brazilian forest plantations. The Phyllochron (Phyl) and Wang and Engel (WE) development models estimate the daily cumulative leaf number (CLN), and when integrated over time, gives the seedling phase duration (SPD). Field experiments were conducted using eleven sowing dates (SD) during 2014 and 2015 growing seasons in Itajubá, Minas Gerais, Brazil to evaluate the performance and calibrate the model coefficients for predicting the development of the two species. Subsequently, the best model was simulated for current climate conditions (1980–2005) and projected for future climates (2021–2050 and 2071–2100) under two radiative forcing scenarios (RCP 4.5 and 8.5) considering eleven SDs. Data from nine Earth System Models from the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP), that are derived from Coupled Model Intercomparison Project Phase 5 (CMIP5) were used. The Phyl and WE models were capable of predicting the CLN and SPD developmental dynamics for both species. However, the cumulative errors in CLN from the Phyl model, generated less accurate estimates for SPD. By contrast, the WE model was excellent (superior to the Phyl) at estimating CLN and SPD, with an error of less than 2.6 leaves, and 6 days, respectively. Additionally, the projected increases of up to 4 °C throughout the 21st century may modify the development rates, increase the SPD (∼+ 15 days), thus interfering with the permanence time of the two species at forest nursery, the date of sale, and seedling quality. Since the climate change time ranges exert greater influence on the SPD of both species, changing the sowing date and artificially controlling seedling production environments are the most viable adaptation measures to cope future climate change threats.