Temperaturas cardinais e modelagem do desenvolvimento inicial de duas espécies florestais sob clima presente e futuro

Abstract

Increases in air temperature projected throughout the 21st century may impact the initial development dynamics of forest species, especially those located in persistent climate change hotspots. To deal with such threats, it is essential to know the thermal thresholds, evaluate development in current climate conditions and identify the climate change impacts, as well as assess the financial viability for seedling production in future climate conditions. This dissertation aims to: i) estimate the cardinal temperatures and the thermal requirements for the initial development of two native Brazilian forest species - Cybistax antisyphilitica (Mart.) Mart. and Platycyamus regnellii Benth - using data from multiple sowing dates, ii) calibrate and evaluate the performance of both developmental models – Philochron (Phyl) and Wang and Engel (WE) - in estimating the initial development dynamics of both species, and , iii) identify the possible impacts of projected increases in air temperature on the seedling phase duration, and financial viability for the production of seedlings of the two forest species in a forest nursery. To achieve i and ii aims, phenological data from experiments conducted over twelve sowing dates during the years 2017 and 2018 in Itajubá, Minas Gerais were used. The three cardinal temperatures were estimated using appropriate statistical methods. The two development models – Phyl and WE – were calibrated and evaluated for experimental conditions. Regarding iii aim, data from 13 Earth System Models (ESM) from the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP), i.e., the new generation from the Coupled Model Intercomparison Project Phase 6 (CMIP6) were used. The development model (Phyl or WE) that presented the best performance for the experimental conditions was fed with the ESMs outputs simulated for the current climate (CC, 1995-2014), and projected for the near future (NF, 2041-2060) and far future (FF, 2081-2100) in two radiative forcing scenarios (SSP2-4.5 and SSP5-8.5). In addition, the financial viability of producing seedlings of both species was analyzed using the net present value for CC, NF and FF. C. antisyphilitica develops properly between temperatures of 13 °C, 20 °C and 48.4 °C and P. regnellii between 13.7 °C, 21.5 °C and 43.4 °C. For C. antisyphilitica, the Phyl and WE models were remarkably similar in estimating the cumulative leaf number (CLN), and seedling phase duration (SPD), with an error of ~3.3 leaves and 25 days, respectively. On the other hand, the WE model was slightly superior for P. regnellii, with an error of less than 2.06 leaves (CLN) and 13.1 days (SPD). The projected increases in air temperature between ~ 1.1 °C and ~ 4 °C for Itajubá should not make the SPD of the two forest species unfeasible. However, they could generate financial losses in forest nurseries due adaptation measures. Simulated sowing dates between January and June may have SPD reductions for both forest species (up to 36 days). On the contrary, the simulated sowing dates from July to December may have small SPD increases (between 1 and 10 days). It will be necessary to adopt adaptive measures to maintain the seedlings quality and vigorin NF and FF, which will generate increases in seedling production costs from approximately 9% to 137%. More significant increases in costs will occur from August to November, exactly when the SPD increases are projected.