Comportamento fenológico e modelagem do desenvolvimento de espécies florestais: clima atual e futuro

Abstract

Projected increases in air temperature emerge as the primary constraint for forest species development, particularly during the initial stage when seedlings are most sensitive to thermal variability. Understanding the phenology of the initial development is essential for enhancing resilience strategies in forest nurseries and reforestation programs under future climatic conditions. This thesis addresses this issue through five key aims: I) assess the influence of weather variables and storage duration on seed viability in six forest species—Bauhinia forficata Link, Ceiba speciosa (A.St.-Hil.) Ravenna, Handroanthus chrysotrichus (Mart. ex DC.) Mattos, Handroanthus impetiginosus (Mart. ex DC.) Mattos, Tabebuia rosea (Bertol.) Bertero ex A.DC., and Tabebuia roseoalba (Ridl.) Sandwith—using principal component analysis (Chapter I); II) adapt the BBCH phenological scale to describe the initial development stages of five native species (B. forficata, C. speciosa, H. chrysotrichus, H. impetiginosus, and T. roseoalba) (Chapter II); III) estimate the thermal thresholds and requirements for the initial development of these species (Chapter III); IV) calibrate and evaluate the performance of the Phyllochron (FIL) and Wang & Engel (WE) models in estimating the initial development; and V) identify the impact of projected air temperature increases on the duration of initial development (Chapter IV) and the financial feasibility (Chapter V) of seedling production in forest nurseries. To achieve these aims, seedling emergence tests were performed on seed samples, and field experiments were conducted across fourteen sowing dates from 2022 to 2024 in Itajubá, Brazil. The forest species' seeds were sourced from multiple places and exhibited distinct viability patterns regarding emergence percentage, emergence speed index, mean emergence time and mean emergence rate. H. chrysotrichus, H. impetiginosus, T. rosea, and T. roseoalba seeds were more sensitive to storage duration, decreasing viability proportionally with increased storage time. Weather conditions influenced the physiological maturation and emergence of the studied species, with samples from warmer and drier regions showing higher emergence indices. The first BBCH scale adapted to describe the initial development of the studied species identified two main development stages: 0 (germination) and 1 (leaf development), along with twelve substages (codes 00-09 to 110). The species reached substage 110 (10th visible leaf on the main stem) in approximately 171 to 190 days, with differences in the duration of substages (00 to 110) observed across all species. Estimated thermal thresholds ranged from 10.6 to 12.6°C (base temperature), 20.3 to 21.5°C (optimum), and 41.9 to 43.9°C (maximum). C. speciosa exhibited the lowest thermal requirement for initial development (160.5°C day leaf⁻¹), whereas B. forficata had the highest (224.4°C day leaf⁻¹). The Phyllochron and Wang & Engel models estimated leaf number (NFA) with higher accuracy (error < 1.5 leaves) compared to initial development duration (DDI) (error between 11 and 32 days). The Phyllochron model provided better estimates for C. speciosa and H. chrysotrichus development, while the Wang & Engel model performed better for B. forficata, H. impetiginosus, and T. roseoalba. Lastly, to achieve aim V, the best-performing model (Phyllochron or Wang & Engel) was integrated into 16 General Circulation Models (GCMs) from the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP-CMIP6). Simulations of NFA and DDI were performed for the current period (CA, 1995–2014) and projected for three future periods: near future (NF, 2041–2060), intermediate future (FI, 2061–2080), and far future (FD, 2081–2100), under three Shared Socioeconomic Pathways scenarios (SSP2-4.5, SSP3-7.0, and SSP5-8.5). The financial feasibility of seedling production was analyzed based on the net present value (NPV) of calculated costs for CA, NF, IF, and DF (under the three SSPs). Despite projected air temperature increases (+1.3 to +4.5°C) and heterogeneous development responses (-55 to +24 days), financial feasibility is expected to remain unaffected. Adopting adaptive measures to ensure seedling quality and vigor in the future will increase production costs by ~0.2% to 3.5%.