Functional and Floristic Dynamics of Amazonian Forests

264 Pages·2016·6.27 MB·English

by  Adriane Esquivel Muelbert

Functional and Floristic Dynamics
of Amazonian Forests

Adriane Esquivel Muelbert

Submitted in accordance with the requirements for the degree of
Doctor of Philosophy

The University of Leeds
School of Geography

September 2016
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iii

The candidate confirms that the work submitted is her own, except where work
which has formed part of jointly-authored publications has been included. The
contribution of the candidate and the other authors to this work has been explicitly
indicated below. The candidate confirms that appropriate credit has been given
within the thesis where reference has been made to the work of others.
Chapter 3
Esquivel-Muelbert, A., Baker, T. R., Dexter, K. G., Lewis, S. L., ter Steege, H.,
Lopez-Gonzalez, G., Monteagudo Mendoza, A., Brienen, R., Feldpausch, T. R.,
Pitman, N., Alonso, A., Van Der Heijden, G., Peña-Claros, M., Ahuite, M.,
Alexiaides, M., Álvarez Dávila, E., Murakami, A. A., Arroyo, L., Aulestia, M.,
Balslev, H., Barroso, J., Boot, R., Cano, A., Chama Moscoso, V., Comiskey, J. A.,
Cornejo, F., Dallmeier, F., Daly, D. C., Dávila, N., Duivenvoorden, J. F., Duque
Montoya, A. J., Erwin, T., Di Fiore, A., Fredericksen, T., Fuentes, A., García-
Villacorta, R., Gonzales, T., Guevara Andino, J. E., Honorio Coronado, E. N.,
Huamantupa-Chuquimaco, I., Killeen, T. J., Malhi, Y., Mendoza, C., Mogollón, H.,
Jørgensen, P. M., Montero, J. C., Mostacedo, B., Nauray, W., Neill, D., Vargas, P.
N., Palacios, S., Palacios Cuenca, W., Pallqui Camacho, N. C., Peacock, J., Phillips,
J. F., Pickavance, G., Quesada, C. A., Ramírez-Angulo, H., Restrepo, Z., Reynel
Rodriguez, C., Paredes, M. R., Sierra, R., Silveira, M., Stevenson, P., Stropp, J.,
Terborgh, J., Tirado, M., Toledo, M., Torres-Lezama, A., Umaña, M. N., Urrego,
L. E., Vasquez Martinez, R., Gamarra, L. V., Vela, C. I. A., Vilanova Torre, E.,
Vos, V., von Hildebrand, P., Vriesendorp, C., Wang, O., Young, K. R., Zartman,
C. E. & Phillips, O. L. 2016. Seasonal drought limits tree species across the
Neotropics. Ecography
AEM, OLP, TRB, KGD, HtS and SLL design the study; all authors contributed to
data collection and/or data management; AEM analysed the data and wrote the
paper
Chapter 4
Esquivel-Muelbert, A., Galbraith, D., Dexter, K. G., Baker, T. R., Lewis, S. L., Da
Costa, A. C. L., Meir, P., Nepstad, D., Rowland, L. & Phillips, O. L. in review in
Journal of Ecology - Biogeographic distributions predict drought tolerances of
Neotropical tree genera.
AEM, OLP, DG, KGD, TRB and SLL designed the study; ACLDC, PM, DN, LR
collaborated with experimental data, AEM analysed the data and wrote the paper.
Chapter 5
In preparation. AEM, OLP, KGD, TRB and SLL designed the study; RAINFOR
data network provided the data; AEM analysed the data and wrote the paper.
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Chapter 6
In preparation. AEM, OLP, KGD, TRB and SLL designed the study; RAINFOR
data network provided the data; AEM analysed the data and wrote the paper.

This copy has been supplied on the understanding that it is copyright material and
that no quotation from the thesis may be published without proper
acknowledgement.

Assertion of moral rights:
The right of Adriane Esquivel Muelbert to be identified as Author of this work has
been asserted by her in accordance with the Copyright, Designs and Patents Act
1988.

© 2016 The University of Leeds and Adriane Esquivel Muelbert
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Acknowledgments
Bringing a four-year project together in one document showed me how
much I have achieved during this process. Looking at all these pages I see a dream
becoming reality, which was only possible because of the amazing people that
supported me along this journey.
I feel particularly lucky. I had Oliver Phillips as my main supervisor who
guided me through this intellectual Amazonian adventure and from whom I have
learned so much about science and tropical forests. His dedication and patience
helped me improve at each of the uncountable supervision meetings. Together with
Oliver, I had a stellar team of ecologists as co-supervisors: Kyle Dexter, Tim Baker
and Simon Lewis, who were always supportive and inspirational. Working with
them was a privilege and I thank them for their help, great ideas and dedication. I
further thank Hans ter Steege for contributing with data and ideas for Chapter 3.
I was part of the Ecology and Global Change (EGC) research group at the
University of Leeds, which helped to expand my understanding of climate change.
From EGC I specially thank David Galbraith, who helped to developed Chapter 4,
and Sarah Batterman for providing me with a writing retreat and Olivia’s company.
EGC gave me amazing friends: Jess Baker, Freddie Draper, Greta Dargie, Sophie
Fauset, Martin Gilpin, Michelle Johnson, Joey Talbot, Euridice Honorio, Rosie
Goodman, Yunxia Wang and Michelle Kalamandeen. My PhD was part of the T-
FORCES project and I had the great help of Gabriela Lopez Gonzalez and Georgia
Pickavance, whose organization and patience solve any data issue. Martin Sullivan,
Lan Qie (Lainie) and Wannes Hubau were also really helpful in sharing codes and
discussing plot issues.
I had the chance to dive into the forest for a few months during the course
of my PhD. In Nova Xavantina I joined Beatriz Marimon, Ben Hur Marimon Junior
and their lovely students who adopted me in 2013 and taught me how to achieve
excellence in data collection. Across BR-319 I joined Thaiane de Souza and a dream
in an Amazon boot camp that changed my perception of fieldwork. Flavia Costa
and her lab hosted me in INPA providing a great and insightful time in Manaus.
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Leeds became a few degrees warmer during my PhD, not only as a
consequence of global warming, but driven by the arrival of the Brazilian crew.
They brought high quality volleyball, pão de queijo and tight hugs. Julia Tavares,
Fernanda Coelho (my great tree id teacher across BR-319), Marta Giannichi, Bruno
Cintra, Francisco Diniz, Karina Melgaço, Alfredo Filho, Matheus Grandi and
William Goulart. Obrigada pelo carinho, atencão e risadas.
Thanks to the Department of Geography things went smooth. The helpful
and friendly staff was essential, especially Jacqui Manton, Dom Emery, Emma
Sanderson and Fikir Assefa. Here I made amazing friends and learnt from their
interesting research topics: Kathryn, Dylan, Liz, Will, Tom(s), Magaly, Heru,
Marrie, Marina, Khalil, Rachel, Federico and Ersilia. Among the human
geographers I met a special friend from Taipei, Hui-Fang Liu, my yoga guru whom
words of wisdom brought things to perspective. I also met Ana Julia Cabrera
Pacheco from Yucatan who went through this adventure with me from day one to
submission and who I thank for being practicamente familia, for showing me that
sí se puede! even when we were under pressure, and for every evening she
convinced me to take a break and go for a pint.
My friends and family from Brazil join me in this project caring, supporting
and making me feel close to our southern island. I thank my siblings Juan and Luíse,
Mum and Dad for all the love and understanding, for making any challenge seem
easy and for being great friends at all times. I thank Mathew Richardson, who by
accident ended up learning quite a lot about how global change affects tropical
forests. I thank you for your enthusiasm about my endless results and conclusions,
for reading drafts several times and for keeping me smiling all the way through.
This thesis is not an individual's work, but one of the fruits from large tree
of researchers passionate about the Amazon. It was only possible to analyse data
from more than 500 plots monitored at times over 30 years because of those who
collected, organized and managed the data from these plots so that humanity could
understand and protect the most diverse and fascinating forest on the planet. I
dedicate my thesis to every person that contributed to this process from tape
measurements and botanical vouches to numbers and names in huge tables of data.
I am extremely grateful to have the opportunity to contribute to this team.
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Abstract
Intact Amazonian forests are often considered to be in a steady-state, where gains
in growth and recruitment are offset by losses in mortality and where net carbon
accumulation is close to zero. However, permanent plot data have shown that this
ecosystem removes ca. 0.4 Pg of carbon per year from the atmosphere,
approximately 5% of annual anthropogenic emissions. This thesis tests several
competing hypothesized drivers of detected shifts in the structure and dynamics of
intact forest, by assessing changes in functional and floristic composition over the
last 30 years in over 100 long-term tree monitoring plots distributed across the
Amazon. I first show that the majority of species are restricted to wetter conditions,
indicating that stronger and more frequent droughts could threaten many species
(Chapter 3). I generated an index of water-deficit affiliation for more than 500
genera and 1800 species (Chapter 3), and demonstrated that this index can predict
drought-induced mortality in several drought experiments (Chapter 4). Finally, I
document how floristic and functional composition of Amazonian forests has
shifted over the last 30 years: forests are increasingly dominated by large-statured
taxa, and further, large trees are becoming even larger in absolute size (Chapters 5
and 6). However, relative gains in basal area were similar across size classes and
canopy status. In addition, recruits are increasingly comprised of dry-affiliated
genera, while the mortality of wet-affiliated genera has increased in plots where the
dry season has become more intense. Communities are becoming more dry-
affiliated, although these changes still lag behind the drying trend. Overall, this
thesis shows the potential vulnerability of Amazonian biodiversity to an increase in
aridity and supports the hypotheses that a changing climate and increased
atmospheric CO are driving changes in Amazonian floristic and functional
2
dynamics.
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Contents
Acknowledgments ......................................................................................... v
Abstract ...................................................................................................... vii
List of Tables .............................................................................................. xii
List of Figures ........................................................................................... xiii
Abbreviations ............................................................................................ xvi
Introduction .................................................................................................. 1
1.1 Environmental conditions ................................................................ 4
1.1.1 Climate in tropical rainforests ............................................. 4
Forest and climate feedbacks ............................................... 8
1.1.2 Soil and nutrient availability in tropical forests .................. 8
1.2 Physical and Environmental Changes in Tropical Forests ............ 10
1.2.1 Atmospheric changes ......................................................... 10
Greenhouse gasses ............................................................. 10
Aerosol concentration ........................................................ 11
Nitrogen deposition ........................................................... 12
1.2.2 Changes in climate ............................................................ 13
Temperature ....................................................................... 13
Precipitation ....................................................................... 13
1.2.3 Direct anthropogenic impacts ............................................ 15
Deforestation ..................................................................... 15
Defaunation ....................................................................... 16
1.2.4 Previous disturbances ........................................................ 16
1.3 The Ecology of tropical forests in a changing environment .......... 18
1.3.1 Ecophysiology ................................................................... 19
Increase in resources .......................................................... 19
Ecophysiological challenges to plants ............................... 21
1.3.2 Changes to forest communities.......................................... 24
Increase in resources .......................................................... 24
Ecophysiological challenges.............................................. 26
Direct human impact ......................................................... 28
Previous disturbances ........................................................ 28
Increase in lianas ............................................................... 29
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1.3.3 Changes to tropical forests structure and dynamics .......... 29
Increase in resources ......................................................... 29
Environmental challenges ................................................. 30
Direct human impact ......................................................... 30
Previous disturbances ........................................................ 31
Increase in lianas ............................................................... 31
1.4 Sample sufficiency ........................................................................ 31
1.5 Aims and objectives ...................................................................... 32
1.5.1 Aims .................................................................................. 33
1.5.2 Objectives .......................................................................... 33
Conceptual Approach and Methods ......................................................... 35
2.1 Introduction ................................................................................ 36
2.2 Proposed overall conceptual approach ....................................... 38
2.2.1 Predictions ......................................................................... 42
2.2.2 Prioritizing hypotheses to be tested .................................. 43
2.2.3 Hypotheses testing ............................................................ 44
2.2.4 Possible hypotheses ........................................................... 47
2.2.5 Selecting the most parsimonious explanations: ................ 48
2.3 Review of Amazonia’s vegetation data...................................... 48
2.3.1 Amazon Tree Diversity Network (ATDN) ....................... 48
2.3.2 RAINFOR ......................................................................... 50
2.3.3 Smaller plots ..................................................................... 50
2.4 Analytical approach ................................................................... 53
Seasonal drought limits tree species across the Neotropics .................... 57
3.1 Introduction ................................................................................... 58
3.2 Methods ......................................................................................... 63
3.2.1 Precipitation in the Western Neotropics ........................... 63
3.2.2 Vegetation data set ............................................................ 64
Precipitation and diversity................................................. 65
Metacommunity structure ................................................. 65
Precipitation and taxa distribution .................................... 66
Taxa precipitation affiliation ............................................. 67
3.3 Results ........................................................................................... 68
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3.4 Discussion ...................................................................................... 74
Biogeographic distributions predict drought tolerances of neotropical
tree genera .......................................................................................... 79
4.1 Introduction ................................................................................... 80
4.2 Methods ......................................................................................... 87
4.2.1 Water deficit affiliation ..................................................... 87
4.2.2 Experiments and field observation .................................... 88
4.2.3 Controlling for the baseline mortality ............................... 90
4.2.4 Statistical approach ............................................................ 90
4.3 Results ........................................................................................... 91
4.4 Discussion ...................................................................................... 95
Changing composition of Amazonian tree communities ...................... 101
Trends in functional composition .................................... 112
The influence of climate on functional composition ....... 113
Trends in floristic composition ........................................ 113
Tree-size dynamics in the Amazon: winners take most but not all ..... 129
6.1 Introduction ................................................................................. 130
6.2 Methods ....................................................................................... 133
6.2.1 Vegetation data set........................................................... 133
6.2.2 Size structure ................................................................... 134
6.2.3 Canopy status ................................................................... 135
6.2.4 Wood density ................................................................... 136
6.2.5 Analytical approach ......................................................... 137
6.2.6 Testing for alternative drivers of change in tree size ....... 137
6.3 Results ......................................................................................... 138
6.3.1 Trends in tree-size across the Amazon ............................ 138
6.3.2 Winners are taking most but not all ................................. 144
6.3.3 Alternative drivers of change in tree size ........................ 146
6.4 Discussion .................................................................................... 147
Synthesis and Conclusions ....................................................................... 151
7.1 Research synthesis ....................................................................... 151
7.1.1 The majority of the Neotropical tree taxa are restricted to
wet areas .......................................................................... 152