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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An Ecosystem Perspective
How water and carbon cycles connect the organizational levels of organisms, ecosystem, and landscape, and what we know of the mechanisms of their operation.
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 differentiate between change in organizational level (shown with arrows) and simple aggregation. 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) pressure deficit
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 (G pressure deficit s) – 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 pressure deficit
Seasonal dynamics of simulated and measured ecosystem evapotranspiration and volumetric soil moisture
Major evapotranspiration and volumetric soil moisture Carbon fluxes in a forest
units: Pg/yr (1x 1015 g)
Small Carbon Storage evapotranspiration and volumetric soil moisture
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
50N evapotranspiration and volumetric soil moisture
Units: Tons C ha-1 yr-1
80WIn 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
Timber harvesting is a major agent of ecosystem disturbance worldwide.
Timber harvesting affects microclimate, carbon pool sizes, decomposition, and ecosystem 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 evapotranspiration and volumetric soil moisture
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.
Hypothesis ecosystems to the global carbon budget should consider the diversity of site conditions and developmental stages
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?
(a) ecosystems to the global carbon budget should consider the diversity of site conditions and developmental stages
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 ecosystems to the global carbon budget should consider the diversity of site conditions and developmental stages
Leaf gross photosynthesis
Net ecosystem exchange
Leaf net photosynthesis
Gross primary production
Net primary production
Root & mycorrhizal respiration
Leaf litter respiration
Heterotrophic soil respiration
Soil surface CO2 efflux
Respiration: forest ecosystem carbon fluxes
Modified from Gifford 2003
J-Rover: The Mobile Flux Cart ecosystems to the global carbon budget should consider the diversity of site conditions and developmental stages
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