Tropical forests in a changing world: Investigating global change impacts in Amazonia and Puerto Rico

Tropical forests in a changing world:Investigating global change impacts

in Amazonia and Puerto Rico

Christine S. O’Connell

University of California, BerkeleyEnvironmental Science, Policy, & Management (ESPM) Seminar

Feb 25, 2016

Tropical forests and global change

How is forest biogeochemistry affected by land use and climate change in two tropical sites?

- Agriculture, energy and biogeochemistry in Amazonia

- Drought, oxygen and biogeochemistry in Puerto Rico

Foley et al. (2011)

Agriculture occupies ~38% of Earth’s terrestrial surface

Agricultural expansion and trade forces subsequently drive deforestation

Hansen et al. (2013) (fig), Lenzen et al. (2012), Lambin et al. (2003), DeFries et al. (2010)

Both

IPCC AR5 (2014)

Remaining forests will likely experience changes to precipitation timing and amount

Land and climate are changing with poorly

known consequences for tropical forest

biogeochemistry


Agriculture, energy and biogeochemistry in Amazonia

- Extensification- Intensification

Saatchi et al. (2011), Brienen et al. (2012)

Amazonia is the globe’s largest tract of tropical forest, contains 100 Gt of carbon in biomass, and rapidly cycles water

Nepstad et al. (2014)

Deforestation (~20%) has been falling since 2004, as intensification on agricultural lands rises.

QHow does agricultural extensification impact carbon, energy and habitat? Can we balance these ecosystem services across space?

We combined data from remote sensing, model output, andgeostatistical datasets to assess spatial variation in services


• Changes in carbon (C) stocks• Energy balance regulation

• Habitat quality


• Changes in carbon (C) stocks• Energy balance regulation

• Habitat qualityWe hypothesized that comparing these impacts to agricultural gains from expansion would lead to different conservation implications for each environmental goal.

C stock reductions relate to precipitation, landscape degradation, and soils

Net aboveground biomass and mineral soil C lost after land

use change

Local atmospheric drying after land use change is greater in the strongly seasonal east

Reduction in exported moisture per day (via

evapotranspiration)

…and local warming is higher in the same area

Increase in local atmospheric

temperature (annual average)

Plants, birds and mammals all have the highest relative species diversity in the Andes Amazon

Number of species ranges represented in

each grid cell

Tradeoffs consider both gains and losses

Calories gained / change in ecosystem property

Ecosystem services: potential cobenefits



The location of future agricultural expansion will largely dictate the impacts of Amazonian land use on ecosystem services

Doubling Amazonia's agricultural lands at least harm to the environment

We ran an algorithm that expands agriculture at the least combined “harm,” while changing the priority between C, energy balance and habitat

Carbon storage

priority levelCarbon storage

priority levelCarbon storagepriority level

TgC

Emitt

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Spec

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ffec

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Carbon storagepriority level

Carbon storage priority levelCarbon storage

priority level

TgC

Emitt

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Spec

ies

Rang

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ffec

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Regi

onal

Clim

ate

Inde

x





TgC

Emitt

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Spec

ies

Rang

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ffec

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Regi

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Clim

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Where matters:balancing ecosystem services in the tropics may require tradeoffs

between environmental goals



- Extensification- Intensification

Tanguro Ranch

Tanguro Ranch: Land use change impacts case study







Tanguro Ranch has three land uses:

transitional Amazon forest (F), soybean cultivation (S), and

soybean/maize (double cropped)

cultivation (M).

MAT: 27°C

MAP: 1800 mm/y

Management: N- (x2, M only) and P-fertilizer (x2), lime, pesticide, herbicide

Soils: ~40% clay; pH 4.5 (F), 5.5-6 (S, M)

QAmazon intensificationtrace gas patterns: How does cropland management affect CO2, N2O and CH4 in Southeastern Amazonia?

Do the impacts of land use propagate down the soil profile in a way that may influence trace gas emissions?

10m soil pit!

15 cm

40 cm

75 cm

150 cm

250 cm

350 cm

450 cm

Gas Sampling Data

ThermocoupleandTime-Domain Reflectometry

Three pits in transitional Amazon forest (For), three in

agriculture (Ag).

Agricultural soils are wetter, with a pronounced dip at crop rooting depth; high forest moisture variability

Land use effect, p < 0.0001; depth effect, p < 0.0001; interaction, p < 0.001

Agricultural soils are also hotter, and less variable than forest temperatures –promoting trace gas production

Land use effect, p < 0.0001; depth effect, p < 0.0001; interaction NS

How do these abiotic factors interact with N fertilizer management to influence trace gas

emissions in cropland and forest?

Field measurement of N pools and GHG fluxes

+ 30 kgN/yr as nitrate+ 45 kgN/yr as urea

Forest (F) Soybean (S) Soybean/Maize (M)

Dry season N2O emissions are uniformly near zero (~0-0.5 ngN/cm2/h). Surprisingly, wet season emissions

remain low as well, between 1-4 ngN/cm2/h. Land uses did not significantly differ.

S MF

While post-fertilization N2O peaks can be substantial, in several cases they barely deviated from the baseline.

S MF

NO3- concentrations

are significantly higher in N-fertilized maize fields than in forests (p < 0.01).

However, there is not a significant

correlation between N2O emissions and

soil inorganic N availability.


CO2 fluxes are highest in soybean/maize sites (p < 0.01). Comparison of row-interrow chambers indicated

that cropland row chambers had fluxes ~90% higher than inter-row chambers.

S MF


CH4 emissions in forests had strong heterogeneity within site. Forest soil uptake of CH4 was significantly

larger than in agricultural soils (p < 0.001).

S MF

What are the implications of these differences for global climate?

We extrapolated to an annual flux on each land use by calculating the average dry season flux, wet season flux, and “post-fertilization” flux (<15 days after N fertilization)

Take-away: N2O sees re-ranking between forest/ag annual emissions with management

Amazonian intensification may have limited greenhouse

gas consequences, with profound implications for tropical agriculture



Drought, oxygen and biogeochemistry in Puerto Rico

Luquillo Experimental Forest: Historic drought

QHow does severe drought impact belowground biogeochemistry and GHG emissions?

Field array (O2 and TDR sensors, automated GHG chambers) allowed high temporal resolution data before, during and after

Soil moisture and O2 exhibited a threshold response to drought with lengthy persistence; valley less sensitive to O2 changes

Soil moisture and O2 exhibited a threshold response to drought with lengthy persistence; valley less sensitive to O2 changes

Greenhouse gas emissions show patterns across topographic space: particularly CO2 on slopes.

Iron(II) concentrations decreased post-drought, particularly in the valleys, while Iron(III) concentrations increased, associated with Iron(II) oxidation to Iron(III) after soil oxygen availability rose.

Inorganic phosphorus concentrations declined dramatically during the drought, possibly due to Fe-P bonding. Organic P increased slightly, possibility due to decreased decomposition rates.

Drought may impact tropical forest carbon storage both directly via moisture changes,

and indirectly via nutrient availability

Summary: Land use change

Deforesting tropical land likely has much larger

biogeochemical ramifications than intensification on

tropical agricultural lands

Summary: Climate change

Climate change impacts on tropical forest

functioning will likely feature complex feedbacks

between nutrient cycles

Improving our knowledge about how global change impacts tropical forests will be critical to managing these key

ecosystems in a changing world

Thanks very much

Photo creditsFlickr CC Users

CIFORBilltacular

Jacsonquerubinflinner!

Carine06LeoFFreitas

terryduggalliceIcelight

MODIS images via NASA

Obrigada toThe Silver Lab and ESPM for postdoctoral support

My wonderful mentors at Minnesota: Sarah Hobbie, Steve Polasky, Jennifer Powers, Rod Venterea, and Jon Foley

Colleagues at collaborating institutions: Mike Coe, Eric Davidson, Chris Neill, Marcia Macedo, Paul Lefebvre, Chelsea Nagy, Carlos Cerri, and Paulo Brando

The field team at Tanguro: Santarem, Bati, Darlisson, Ebis, Sandro and Dona Lucia

Supporting agencies below:

Christine S. O’Connell, [email protected], UC-B ESPM

IPCC AR5 (2014)

Remaining forests will likely experience changes to precipitation timing and amount

Carbon storage priority changes

Habitat quality priority changes

Regional climate priority changes

Tg C Effects Habitat Effects Reg. Clim. Effects







