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

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;


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

Background

  • 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)


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

Spatial display of growing season ecosystem evapotranspiration from eight ecosystems


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

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


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

Major water fluxes in a forested watershed


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

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


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

Ecosystem transpiration flux saturates with increasing vapor pressure deficit


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

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.


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

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.


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

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


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

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


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

Major Carbon fluxes in a forest


Global carbon cycle

Global carbon cycle


Atmospheric carbon pools can be reduced by

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

Terrestrial ecosystem carbon cycle

- 3

720

Atmosphere

-2

X

0

13

39

480

+2

43

74

2

24

80

31

31

140

25

900

Pools

Fluxes

1500

units: Pg/yr (1x 1015 g)


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

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

http://www.globalforestwatch.org


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

Small Carbon Storage

Fast

Fast

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

Fast

Slow


In the united states major carbon sinks are in the east part of the continent myneni et al 2001

50N

40N

Units: Tons C ha-1 yr-1

30N

120W

110W

90W

70W

100W

80W

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

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

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.


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

Swiss-Cheese Mosaic

Pine Barrens

The Checker-board landscape

Spatial Mosaics of Managed Landscapes in N. WI


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

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.


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

Hypothesis

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?


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

(a)

(c)

(b)

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.


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

Autotrophic respiration

Leaf gross photosynthesis

Net ecosystem exchange

Leaf net photosynthesis

Leaf respiration

Photorespiration

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

Atmosphere

Photo-tissue

Non-photo-tissue

CWD

Leaf litter

Soil

Roots

Modified from Gifford 2003


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

J-Rover: The Mobile Flux Cart


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

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


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

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


Water and carbon cycles in heterogeneous landscapes an ecosystem perspective

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


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