S pruce and P eatland R esponses U nder C limatic and E nvironmental Change Paul J. Hanson...

Spruce and

Peatland

Responses

Under

Climatic and

Environmental Change

Paul J. HansonEnvironmental Sciences Division

http://mnspruce.ornl.gov

An experiment to assess the response of northern peatland ecosystems to increases in temperature and exposures to elevated atmospheric CO2 concentrations

2 Managed by UT-Battellefor the U.S. Department of Energy SPRUCE Experiment Summary

What is SPRUCE?

A multi-year cooperative among scientists of the Oak Ridge National Laboratory operated by UT-Battelle, LLC and the USDA Forest Service Northern Research Station at the Marcell Experimental Forest in northern Minnesota

→ An experiment to assess the response of northern peatland ecosystems to increases in temperature and exposures to elevated atmospheric CO2 concentrations.

→ Sponsored by the Office of Biological and Environmental Research within the US Dept. of Energy’s Office of Science.


An experimental system to measure the effects of environmental and atmospheric changes on peatlands.

Study responses within a peatland to multiple levels of warming at ambient and elevated CO2 levels, in a replicated design:

–Warming levels from ambient to +9°C (above and below ground) inside

large, open-top chambers.

–Elevated CO2 in the range of 800 to 900 ppm for the ambient and +9°C

warming treatments.

Questions to be addressed• How vulnerable are peatland ecosystems and their component

organisms to atmospheric and climatic change? – Can we quantify the potential for shifts in local species dominance and regeneration

success to assist projections of future biome changes over decades to centuries? – Will species assemblages or loss of species have unanticipated impacts on ecosystem

processes? – Do changes in ecosystem services precipitate a change in state (e.g., loss of a dominant

plant functional type)?

• To what degree will changes in plant physiology under elevated CO2 impact a species’ sensitivity to climate or competitive capacity within the community?

• Will full belowground warming release unexpected amounts of greenhouse gases and solutes from high-C-content northern forests?

– How will decomposition, nutrient cycling, and feedbacks on solute availability affect ecosystem productivity, solute efflux, and trace gas emissions?

• What are the critical air and soil temperature response functions for ecosystem processes and their constituent organisms? – Do those response functions for ecosystem processes depend on shifts in species

interactions and composition?

• Will ecosystem services (e.g., biogeochemical, hydrological, or societal) be compromised or enhanced by atmospheric and climatic change?

ECOSYTEM SCALES

microbial processes /

plant species

entire peatland

ecosystems


The Picea – Sphagnum Ecosystem

•A Critical Ecosystem–The experiment will be conducted in a Picea mariana [black spruce] – Sphagnum spp. forest in northern Minnesota. –This ecosystem located at the southern extent of the spatially expansive boreal peatland forests is considered vulnerable to climate change and is expected to generate important greenhouse gas feedbacks to the atmosphere under changing future climates.


SPRUCE Project SettingThe S1 bog watershed at the

Marcell Experimental Forest of the Northern Research Station of the USDA Forest Service.

North of Grand Rapids in Itasca County, MNDeer River Ranger DistrictChippewa National Forest

A mix of uplands, bogs, fens, lakes, and streams in the

Marcell hills moraine.


Looking into a 1974 Strip-cut Area24 March 2010


SPRUCE will be conducted in the S1-Bog -- a well-studied hydrologic and ecological setting


• By 2100 future terrestrial environments may be 4 to 8°C warmer than today (Solomon et al. 2007) depending on the location.

• An overlooked reality is that mean deep (>1m) soil temperatures will also rise with climate warming (Huang 2006).

• Experimental systems must be improved to provide the best atmospheric and soil conditions appropriate for characterizing terrestrial ecosystem responses to year 2100 scenarios -- air and soil warming by as much as 8 to 10 °C.

• Effective deep belowground heating requires an effective aboveground heating method capable of maintaining the same target temperature differential for deep belowground warming.

ORNL’s Approach for Ecosystem Warming

A SPRUCE Experimental Plot

Isolated belowground

corral includes peat layers

Recirculating forced-air heaters with

internal air mixing provide above ground

heating (x6 to 8)

Belowground heating provided by gradual heat inputs from deep heating probes located away from the target biology

A movable roof could be added to this

chamber during non-precipitating night hours

to reduce operational costs.

Precipitation DepositionRadiation

• 12 m diameter, 8 m tall, deep heating at -2 to -3 meter


In larger plots, circumferential heating is supplemented with interior deep-only heating to maintain uniform warming throughout the soil volume.

• Belowground heating designs to accommodate full ecological diversity have been simulated and are being constructed for testing for application to the whole-ecosystem manipulations in the replicated study in the S-1 bog.

Simulated Differential Temperature Contours

(°C)


Experimental BlocksAnd Approximate

Plot Positions:

• Shorter trees• Uniform peat depth

• Standard age

Block 4

Block 3

Block 2

Block 1


System Modeling of Biogeochemical Cycles and Organism Responses

Carbon, water, energy, and nutrient exchange

GPP, Respiration, Allocation

Variable acrotelm depth and activity

Variable catotelm activity

Light penetration to foliage and Sphagnum(sun vs. shade issues)

Hummock and hollow issues

Ground area coverage

Heterotrophs:CO2 vs. CH4


Why we do ecosystem experiments:• As a US DOE laboratory Oak Ridge National Laboratory Scientists

seek to understand the implications of energy and energy use technologies on humans and the Environment.

• We plan and conduct targeted experiments to predict vulnerability of important terrestrial ecological systems and their function to projected changes in climate and atmospheric composition

• We develop experimental platforms for testing mechanisms controlling vulnerability of organisms, ecosystems and ecosystem functions to a range of temperature, precipitation, CO2, and air pollution treatments for important ecosystems.


http://earthobservatory.nasa.gov

SPRUCE


Project Organization


Complex fluid dynamics simulations are being used to enhance our system design for field applications.

wind

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