Climate change in Brazilian ecosystems: functional responses of native plants

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1 Climate change in Brazilian ecosystems: functional responses of native plants Rafael S. Oliveira Plant Biology Department/UNICAMP

2 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 km 3 moves through trees each year) The climate system has long been thought to drive this water movement through forests

3 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

4 CLIMATE VEGETATION

5 Hierachy of spatial scales

6 First study case: The Amazonian Paradox About half of the Amazon rainforest is subject to seasonal droughts of three months or more

7 Map of Annual Precipitation in Amazônia Tapajós Forest 72º 68ºW 64º 60ºW 56º 52ºW 48º 4º N 0º 0º 4º S 8ºS 8º 12º 16ºS Extent of continuous tree-cover 12 º S 16 º 76ºW 72º 68ºW 64º 60ºW 56º 52ºW 48º Source: Precipitation map: Sombroek (2001) Tree-cover extent: Defries et al. (2000)

8 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

9 Total annual precipitation Cross-hatching indicates ENSO influence

10 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

11 Forest green up during the 2005 drought Saleska et al Science Why???

12 Dimorphic roots many trees share this trait Lateral roots Tap root

13 Heat ratio sapflow method

14 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

15 V = thermal diffusivity x Ln T 1 probe distance T 2 Heat Ratio Method (Burgess et al. 1998, 2001) T 1 Heater Flow velocity (V) is logarithmically related to the ratio of temperature increases up- and downstream from a heater T 2

16 Rainfall exclusion experiment Seca plot Control plot

17 Sap-flow velocity Hydraulic redistribution of water mediated by root systems b b c a b a c +: fluxo de água em direção à planta -: fluxo de água em direção ao solo a b c Antes chuva Dia Depois chuva

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19 Hydraulic redistribution banks excess water in deep soil to allow ET to extend into the dry season Transpiration difference: HR-Con ET increased over where water stress exists: coincides with the places where HR is observed. In: Lee, Oliveira et al. 2005, PNAS Annual Mean

20 Temperature decreased where ET increased Temperature difference: HR-con In: Lee, Oliveira et al. 2005, PNAS

21 Second study case Climate change in Brazilian Mountains: functional responses of native plants to extreme droughts

22 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?

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24 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

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26 Irrigação (regas diárias do solo) Neblina (exposição exclusiva da parte aérea à neblina artificial) Seca (exclusão total de água)

27 Monitoramento ambiental dos experimentos em casa de vegetação Temperatura & Umidade Relativa Umidade foliar e Radiação fotossinteticamente ativa

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29 Controle LY 24hs Controle LY 24hs Barras: 5 µm

30 Velocidade do fluxo de seiva- V (cm/h) VPD (kpa) Sap flow reversals during fog 25 2,95 V (cm/h) 20 VPD (KPa) 2,45 15 * * 1,95 * 1, ,95 5 0,45 0 * X ,05-5 Dias -0,55

31 Water absorption by leaves: an alternative drought avoidance mechanism? Dias Dias Dias Fogged plants higher stomata conductance and carbon gain

32 SPAC MODEL (Soil-plant-atmosphere continuum)

33 c

34 Scientific challenges - Monitor ecosystem responses to extreme droughts - Savanna-forest interface provide mechanisms to understand what drives this interface - Scale integration

35 Scales of life: spam 14 orders of magnitude!

36 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

37 Water absorption by leaves: alternative drought avoidance mechanism in amazon forests? Evidence from deuterium irrigation experiment, sapflow, water potential Cardinot et al, in review