Water and Carbon Cycles in Heterogeneous Landscapes:
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Water and Carbon Cycles in Heterogeneous Landscapes: An Ecosystem Perspective. Chapter 4. How water and carbon cycles connect the organizational levels of organisms, ecosystem, and landscape, and what we know of the mechanisms of their operation. .

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Water and Carbon Cycles in Heterogeneous Landscapes: An Ecosystem Perspective

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Water and Carbon Cycles in Heterogeneous Landscapes:

An Ecosystem Perspective

Chapter 4

How water and carbon cycles connect the organizational levels of organisms, ecosystem, and landscape, and what we know of the mechanisms of their operation.

  • Obstacles that one faces trying to connect these different levels and the ways to tackle them;

  • Current research questions and approaches;


  • Ecosystem vs landscape

  • Ecosystem ecology vs landscape ecology

  • Lack of ecosystem studies at landscape level

  • Extremely difficulty to measure an ecosystem process (e.g., water and carbon fluxes)

  • Sound experimental design is extremely difficult to develop

  • Challenge in scaling (up and down)

Spatial display of growing season ecosystem evapotranspiration from eight ecosystems

Organizational levels above and below ecosystem. We differentiate between change in organizational level (shown with arrows) and simple aggregation.

Major water fluxes in a forested watershed

Water Fluxes: Growing season evapotranspiration for five ecosystems and their relative contributions at a landscape scale in northern Wisconsin.

Ecosystem transpiration flux saturates with increasing vapor pressure deficit

Evapotranspiration (E) – Monteith Model (1965)

E is evapotranspiration,  is the slope of the saturation vapor pressure-temperature curve, Rn is canopy net radiation, cp is the specific heat capacity of air, a is the density of air, VPD is vapor pressure deficit from canopy to air, ra is the bulk vegetation aerodynamic resistance, w is the density of water,  is the latent heat of evaporation,  is the psychrometric constant, and rc is canopy resistance. Aerodynamic resistance, ra, is affected by canopy properties and the flow of air through and above the canopy, while rc = (GSL)-1, where GS is canopy average stomatal conductance and L is canopy leaf area.

Stomata Conductance (Gs) – Jarvis Model (1976)

where -m is the logarithmic sensitivity of the GS response to VPD. GSref is defined as maximum GS at VPD=1 kPa. This model is preferred over the Ball-Berry stomatal conductance model (Ball et al., 1987) because of its use of relative humidity as the driving factor instead of VPD.

Topography (A) and ecosystem types (B) of a section of CNNF

Seasonal dynamics of simulated and measured ecosystem evapotranspiration and volumetric soil moisture

Major Carbon fluxes in a forest

Global carbon cycle

Atmospheric carbon pools can be reduced by:

  • 1) Reduce carbon emission from fossil fuel combustion.

  • 2) Increase carbon storage by:

    • Increasing ecosystem productivity, and

    • Decreasing plant decomposition

Terrestrial ecosystem carbon cycle

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units: Pg/yr (1x 1015 g)

Forests cover a wide geographical area and contain 80% of all aboveground terrestrial carbon(Waring and Running, 1998)


Small Carbon Storage



Large Carbon Storage

The ability for terrestrial ecosystems to store carbon depends on the rate at which carbon dioxide is absorbed through photosynthesis and released by decomposition





Units: Tons C ha-1 yr-1








In the United States, major carbon sinks are in the east part of the continent (Myneni et al., 2001).

Units: Tons C ha-1 yr-1

Why focus on timber harvesting?

Timber harvesting is a major agent of ecosystem disturbance worldwide.

Timber harvesting affects microclimate, carbon pool sizes, decomposition, and ecosystem respiration.

Decomposition and Respiration

They are the primary mechanisms that recycles carbon bound in plant tissue or in organisms back to the atmosphere.

These two processes determine the capacity of an ecosystem pool to hold carbon.

Swiss-Cheese Mosaic

Pine Barrens

The Checker-board landscape

Spatial Mosaics of Managed Landscapes in N. WI

An accurate assessment of the contribution of terrestrial ecosystems to the global carbon budget should consider the diversity of site conditions and developmental stages

within the landscape mosaic.


The cumulative C fluxes of a landscape are determined by the land mosaic; that is, the various ages and types of ecosystems present, as well as their size and shape.

Landscapes are composed of a variety of ecosystems differing in type, age, size, shape, and spatial arrangement. A key question is:

Are managed landscapes a C sink or source?




Changes in NEP with age (a) and the age structure of a hypothetical landscape (b) together determine the cumulative NEP of the landscape (c)

Chen et al. 2004.

Autotrophic respiration

Leaf gross photosynthesis

Net ecosystem exchange

Leaf net photosynthesis

Leaf respiration


Stem respiration

Gross primary production

Net primary production

Root & mycorrhizal respiration

Leaf litter respiration

CWD respiration

Heterotrophic soil respiration

Heterotrophic respiration

Soil surface CO2 efflux

Respiration: forest ecosystem carbon fluxes





Leaf litter



Modified from Gifford 2003

J-Rover: The Mobile Flux Cart

Net ecosystem exchange of carbon (NEE) as a function of ambient photosynthetically active radiation (PAR)

Growing season cumulative NEE, ER, and GEP in stands of different ages

Landscape-level variation in gross ecosystem productivity, ecosystem respiration and net ecosystem exchange of carbon

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