Title: 2.27. Transient Land Use and Land Cover Change — ctsm CTSM master documentation

URL Source: https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Transient_Landcover/CLM50_Tech_Note_Transient_Landcover.html

Markdown Content:
CLM includes a treatment of mass and energy fluxes associated with prescribed temporal land use and land cover change (LULCC). The model uses an annual time series of the spatial distribution of the natural and crop land units of each grid cell, in combination with the distribution of PFTs and CFTs that exist in those land units. Additional land use is prescribed through annual crop-specific management of nitrogen fertilizer and irrigation (described further in [2.26](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Crop_Irrigation/CLM50_Tech_Note_Crop_Irrigation.html#rst-crops-and-irrigation)), and through wood harvest on tree PFTs. For changes in the distributions of natural and crop vegetation, CLM diagnoses the change in area of the PFTs and CFTs on January 1 of each model year and then performs mass and energy balance accounting necessary to represent the expansion and contraction of the PFT and CFT areas. The biogeophysical impacts of LULCC are simulated through changes in surface properties which in turn impact the surface albedo, hydrology, and roughness which then impact fluxes of energy, moisture and momentum to the atmosphere under the altered properties. Additionally, changes in energy and moisture associated with changes in the natural and crop vegetation distribution are accounted for through small fluxes to the river and atmosphere. The biogeochemical impacts of LULCC are simulated through changes in CLM carbon pools and fluxes (see also Chapter [2.16](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/CN_Pools/CLM50_Tech_Note_CN_Pools.html#rst-cn-pools)).

CLM can also respond to changes in ice sheet areas and elevations when it is coupled to an evolving ice sheet model (in the CESM context, this is the Community Ice Sheet Model, CISM; see also Chapter [2.13](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Glacier/CLM50_Tech_Note_Glacier.html#rst-glaciers)). Conservation of water, energy, carbon and nitrogen is handled similarly for glacier-vegetation transitions as for natural vegetation-crop transitions.

