Name: Bernardo Pretti Becacici Macieira
Type: PhD thesis
Publication date: 13/09/2019
Advisor:

Name	Role
Geraldo Rogério Faustini Cuzzuol	Advisor *
Marcos Silveira Buckeridge	Co-advisor *

Examining board:

Name	Role
Camilla Rozindo Dias Milanez	Internal Examiner *
Elias Terra Werner	Internal Examiner *
Geraldo Rogério Faustini Cuzzuol	Advisor *
Gloria Maria de Farias Viégas Aquije	External Alternate *
José Eduardo Macedo Pezzopane	External Examiner *
Marcelo Schramm Mielke	External Examiner *
Marcos Silveira Buckeridge	Co advisor *
Paulo Cezar Cavatte	Internal Alternate *

Summary: Tropical forests have a crucial role of the global carbon and climate cycle, cover 10
% of the surface of the Earth and store 25 % of global terrestrial carbon pool.
Structural carbon pool (SC) of tree species that make up tropical forests may
account 42 – 61 % dry biomass, while non-structural carbon pool (NSC) range for
25 – 35 %. Therefore, it is important to understand the dynamics of SC (cellulose,
hemicelluloses and lignin) and NSC (soluble sugars and starch) allocation in
tropical tree species, specifically in the face of climate variations, as well as the
relationship of water and carbon in a systemic view. The aim of the present study
was to evaluate how short-term climate variations modulate the allocation
dynamics of SC and NCS in pioneer (Senna multijuga) and non-pioneer
(Hymenaea aurea) tropical trees of Atlantic forest (Chapter 1). Another aim of this
study was to provide a systemic view of balance between carbon allocation and
hydraulics in different populations of tree species Neotropical Hymenaea courbaril
distributed in a microclimate and continentalization gradient (Chapter 2). Our
results showed that the leaf and wood SC and NSC pools of S. multijuga and H.
aurea were influenced by climate variations with trends of higher values in winter.
In this season of lower temperature and precipitation, we observed higher levels of
soluble sugars (glucose, fructose and sucrose), hemicelluloses and their galactose
and glucose monomers in S. multijuga. In this same season, H. aurea showed
higher levels of leaf and wood starch and leaf hemicelluloses, including its
arabinose monomer. The only carbohydrate that increased in summer was leaf
cellulose in H. aurea. Generally, pioneer tree species showed higher levels of NSC
in both source and sink organs, while the non-pioneer tree species exhibited higher
levels of SC. Systemic view of H. courbaril populations revealed that changes leaf
physiology is not necessarily associated with changes in volumetric growth rate,
but it may be associated with changes in wood density. It indicates that trees are
likely to invest in the addition of SC in a similar volume of wood. Another interesting
result shows that trees precisely finely tune the concentrations of some cell-wall
monosaccharides, more specifically xylose and mannose. These changes in cellwall
composition are also associated with changes in the allocation of NSC likely
related to the resilience of trees. We concluded that short-term climate variations
influenced the SC and NSC contents and composition of pioneer and non-pioneer
tree species increasing the size of these carbon pools in winter. Systemic view of
the balance between carbon allocation and tree hydraulics has indicated that
changes in leaf-level physiology, including assimilation and stomatal conductance,
is a central feature in the coordination between carbon allocation and water
transport in trees with important implications for the resilience of trees to climate
change.
Keywords: Atlantic forest • cellulose • cell-wall monosaccharides • hemicelluloses
• soluble sugars • starch •