Name: Felipe Cassa Duarte Venâncio
Type: PhD thesis
Publication date: 28/04/2022
Advisor:
Name |
Role |
|---|---|
| Geraldo Rogério Faustini Cuzzuol | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| Adriana Grandis | External Examiner * |
| Antelmo Ralph Falqueto | Internal Examiner * |
| Bernardo Pretti Becacici Macieira | External Alternate * |
| Diolina Moura Silva | Internal Examiner * |
| Geraldo Rogério Faustini Cuzzuol | Advisor * |
| João Vitor Toledo | External Examiner * |
| José Eduardo Macedo Pezzopane | Co advisor * |
| Paulo Cezar Cavatte | Internal Alternate * |
Summary: The climate projections for the Atlantic Forest biome indicate different regimes for the
Brazilian coast with a higher frequency of extreme events of heat and droughts from the
second half of the 21st century onwards. The Intergovernmental Panel on Climate
Change (IPCC) introduced some scenarios called Representative Concentration
Pathways (RCP) with changes in [CO2], temperature and evaporative demand. Two
climate scenarios are predicted for Atlantic Forest, Brazil: an optimistic one (RCP 4.5)
with moderate increase in [CO2], temperature and evaporative demand and a pessimistic
one (RCP 8.5) with extreme conditions that causes prolonged droughts. The
ecophysiological responses of tropical tree species in altered atmospheric conditions are
still poorly understood, so a questions arises in this climate scenario: how will shadetolerant and sun-tolerant tropical trees respond to these new conditions? The
brazilwood (P. echinata) is a native Atlantic forest species wich has three different
ecotypes in terms of ecological habit (small, medium and large leaf) and is threatened
with extinction. Due to the difficulties in carrying out works of this magnitude under
controlled conditions with different species, the use of a species with intraspecific and
ecophysiological variations is a solution. The current study was divided into three
chapters to evaluate the ecophysiology of two ecotypes of P. echinata, the small leaf
(shade tolerant) and the medium leaf (sun tolerant) under altered atmospheric
conditions. The seedlings were cultivated for 90 days in OTC`s inside an acclimatized
greenhouses in three climate scenarios: in a current Atlantic forest-control scenario (T=
26.1ºC, RH= 82% and [CO2]= 400 ppm) and in two scenarios of climate change-RCP
4.5 (T= 28.1ºC, RH = 80% and [CO2]= 580 ppm) and RCP 8.5 (T= 29.6ºC, RH= 74%
and [CO2]= 936 ppm). Within each scenario, two levels of substrate moisture were
adopted: 80% (control) and 40% (water restriction). Were performed analyzes of
growth, gas exchange, leaf water potential, crop water stress index, chlorophyll
fluorescence, non-structural carbohydrates (starch, glucose, fructose and sucrose) and
cell wall polymers (cellulose, hemicellulose and lignin). Young plants of the two
ecotypes respond positively to increased [CO2], tolerating climate change scenarios
through adjustments in growth, photosynthesis and carbon allocation. Under altered
atmospheric conditions, plants regulated heat exchange, which is essential to ensure
greater photosynthetic performance under water restriction, and change the carbon
allocation, producing energy and structural reservoirs. The high [CO2] probably has a
buffering effect on the two ecotypes, increasing photosynthesis and initial growth,
preventing decreases in biomass accumulation with a reflex of greater mobilization and
accumulation of carbohydrates, mainly starch, in the roots of plants cultivated under
water restriction. The results suggest that young plants of the two P. echinata ecotypes
may respond positively to climate change through physiological and biochemical
tolerance mechanisms
