Predicting temperature ranges for the initial development of two native Brazilian tree species using multiple sowing dates

Abstract

Accurate data on development responses to air temperature are essential to feed development and productivity models through which it is possible to analyze the global warming impacts. The cardinal temperatures – base (Tb), optimum (Topt), and maximum (TB) - delimit the temperature range in which development occurs, while the phyllochron (ºC day per leaf) defines the thermal requirements necessary for leaf appearance and development rate of tree species. Field experiments employing multiple sowing dates provide a wide range of temperature regimes closer to natural field conditions and, at the same time, allow obtaining accurate and reliable estimates of cardinal temperatures and phyllochron values. This study estimated the cardinal temperatures – Tb, Topt, and TB – and the phyllochron of tree species Cybistax antisyphilitica (Mart.) Mart. and Platycyamus regnellii Benth., both native to Brazil, using multiple sowing dates. For this, leaf appearance data from field experiments conducted outdoors during the 2017 and 2018 growing seasons with twelve sowing dates were used. C. antisyphilitica develops properly among 13 °C (Tb), 20 °C (Topt), and 48.4 °C (TB) temperature ranges, and P. regnellii among 13.7 °C (Tb), 21.5 °C (Topt) and 43.4 °C (TB). The phyllochron for leaf appearance was different between the two species. On average, C. antisyphilitica needs to accumulate 88.2 °C day to emit a leaf on the main stem, while P. regnellii needs to accumulate 109.7 °C day per leaf, and both values correspond to a development rate of 0.0134 and 0.0091 leaf per ºC day, respectively. Information about cardinal temperatures provides valuable insights into the development patterns and thermal requirements, which can be used in development models to project the development under future climates.