Climate change in Brazilian ecosystems:
functional responses of native plants
Rafael S. Oliveira
Plant Biology
Department/UNICAMP
Context:
• Native vegetation covers a significant portion of the Earth‟s surface
• Plants as engineers – water pumps to the
atmosphere (main conduits from land to the
atmosphere)
they recycle ~66% of all the fresh water on
Earth each year (~7,500,000 km3 moves through
trees each year)
• The “climate” system has long been thought to
„drive‟ this water movement through forests
Context:
BUT . . .
• Vegetation significantly modify the climate and microclimates that are known to drive water loss
Plant function – a major uncertainty in climate models
• There is a pressing need to determine the relative importance of
biological & physical drivers of the hydrological cycle via,
» Precise characterizations of the biological activities of trees
» Precise characterizations of the environmental drivers
CLIMATE

VEGETATION
Hierachy of spatial scales
First study case: The Amazonian
Paradox
• About half of the Amazon rainforest is subject
to seasonal droughts of three months or more
Map of Annual Precipitation
in Amazônia
72º
68ºW
Tapajós
Forest
64º
60ºW
56º
52ºW
48º
4º N
0º
0º
4º S
8º
8ºS
12 º S
12º
Extent of
continuous
16ºS tree-cover
76ºW
72º
16 º
68ºW
64º
60ºW
Source: Precipitation map: Sombroek (2001)
Tree-cover extent: Defries et al. (2000)
56º
52ºW
48º
First study case: The Amazonian
Paradox
• About half of the Amazon rainforest is subject
to seasonal droughts of three months or more
• El Niño years – severe droughts
Total annual precipitation
Cross-hatching indicates ENSO influence
Amazonian Paradox:
• About half of the Amazon rainforest is subject
to seasonal droughts of three months or more
• El Niño years – severe droughts
• Despite this drought, several studies have
shown that these forests, under a strongly
seasonal climate, do not exhibit significant water
stress during the dry season
Forest “green up”during the 2005 drought
Saleska et al. 2007 Science
Why???
Dimorphic roots – many trees share this trait
Lateral
roots
Tap root
Heat ratio sapflow method
Heat Ratio Sapflow
Method (Burgess et al. 2001)
Probe set
Solar
power
Data logger,
storage module &
battery in tree
Well-organized
multiplexer &
wiring set-up
Heat Ratio Method
(Burgess et al. 1998, 2001)
T1
Heater
Flow velocity (V)
is logarithmically
related to the ratio
of temperature
increases up- and
downstream from
a heater
T2
V = thermal diffusivity x Ln T1
probe distance
T2
Rainfall exclusion experiment
Seca plot
Control plot
Hydraulic redistribution of water mediated by root systems
b
Sap-flow velocity
b
c
a
b
a
c
+: fluxo de água em direção à planta
-: fluxo de água em direção ao solo
a
Antes chuva
c
b
Dia
Depois chuva
Hydraulic redistribution banks excess water in deep
soil to allow ET to extend into the dry season
Transpiration difference: HR-Con
In: Lee, Oliveira et al. 2005, PNAS
ET increased
over where
water stress
exists:
coincides with
the places
where HR is
observed.
Annual Mean
Temperature decreased where ET
increased
Temperature difference: HR-con
In: Lee, Oliveira et al. 2005, PNAS
Second study case
Climate change in Brazilian Mountains:
functional responses of native plants to
extreme droughts
Mountain-top ecosystems are characterized climatically by
receiving constant FOG events
Fog, and its importance
in mountain-top
ecosystems are
unknown, yet could be
central to explain the
persistence of some
species and a have
major role in hydrology
Ecological role?
• Approach -In order to investigate plant/ecosystem response
to climate change we need to know:
• »how they function in response to current climate
• »what climatic factors shape function and ecology most and
what will change most significantly
•
• Some objectives
• »characterize the climate factors that impact plants
»characterize plant and ecosystem responses to these factors
Mountain ecosystems are some of the most vulnerable
to climate change
Irrigação
(regas diárias do solo)
Neblina
(exposição exclusiva da parte
aérea à neblina artificial)
Seca
(exclusão total de água)
Monitoramento ambiental dos experimentos em casa de
vegetação
Temperatura & Umidade
Relativa
Umidade foliar e Radiação
fotossinteticamente ativa
Controle
LY – 24hs
Controle
LY – 24hs
Barras: 5 µm
Sap flow reversals during fog
25
2,95
V (cm/h)
2,45
*
1,95
*
15
*
1,45
10
0,95
5
0,45
0
05°
-5
*
X
08°
-0,05
11°
14°
Dias
16°
18°
20°
-0,55
VPD (kPa)
Velocidade do fluxo de seiva- V (cm/h)
VPD (KPa)
20
Water absorption by leaves: an alternative drought avoidance
mechanism?
Fogged plants
– higher
stomata
conductance
and carbon
gain
Dias
Dias
Dias
SPAC MODEL (Soil-plant-atmosphere continuum)
c
Scientific challenges
- Monitor ecosystem responses to extreme droughts
- Savanna-forest interface – provide mechanisms to
understand what drives this interface
- Scale integration
Scales of life:
spam 14 orders of magnitude!
Challenges
Sites are complex and heterogenous (temporally and
spatially)
- Species responses are complex and unpredictable
(we need to monitor in multiple scales)
- Technical challenges (data transmission,
robustness, size)
- Financial
Water absorption by leaves: alternative drought
avoidance mechanism in amazon forests?
Evidence from deuterium irrigation experiment, sapflow, water potential
Cardinot et al, in review