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Harvested C and Secondary forest area:

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Change of albedo vs. canopy area

EXPECTED IMPACT

New approach to perform C-based wood harvest in ELM-FATES:

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Re-harmonization of C-based global harvest rate

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DEVELOPMENT REQUIRED

Limited understanding of logging impact on land biogeophysical properties:

Forest logging is one of the major land use activities which disturb the physical

properties and surface energy balance of the land surface, including albedo, surface roughness

and leaf area, thus influencing the absorbed radiation, ratio of transpiration versus evaporation,

which is called the local biogeophysical effects.

Uncertainties from forcing data and modeling approaches:

• A widely used approach of logging is through land model simulation forced by area-based

global harvest rate.

• Area-based harvest schemes that do not account for the correct amount of wood

product may create heavily biased wood product amounts.

• Carbon-based harvest schemes are important to accurately account for the harvested biomass,

but the estimated secondary forest area is dependent on model estimation of biomass density.

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The purpose of this work is to explore biogeophysical impact using ELM-FATES and examine

the divergent results after considering the uncertainty from forcing data and modeling approaches.

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HYPOTHESIS

Spinup plan:

Land only case (I1850ELMFATES) with GSWP3.1 atmospheric forcing. (1901 -1925 for spinup and transient before 20th century)

Forced by historical CO2. No N and P cycle in the current model. Wood harvest method is clear-cut.

1. Phase 1: No logging activities to build forest biomass. (100 years)

2. Phase 2: Forced by primary forest and non-forest harvest rates during 1700 - 1799 to build potential secondary forest. 

3. Phase 3: Forced by harvest rates from all 5 harvest categories during 1800 - 1849 to adjust the effect from regrowth.

• Modeling approaches can largely change the logged area and harvested C, and even the

direction of the biogeophysical impact due to the different logging timing and the dominant

impact factor to current forest stand, either under logging or under regrowth.

• The structural changes of FATES model on calculating the canopy radiative transfer

Can also bring additional biogeophysical impact. Next step we will check the difference

between current ELM and ELM-FATES.

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Summary and next step

Change of sensible heat and latent heat