### 2.2.1.2. Vegetation Composition[¶](#vegetation-composition "Permalink to this headline")

Vegetated surfaces are comprised of up to 15 possible plant functional types (PFTs) plus bare ground ([Table 2.2.1](#table-plant-functional-types)). An additional PFT is added if the irrigation model is active and six additional PFTs are added if the crop model is active (Chapter [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)). In [Table 2.2.1](#table-plant-functional-types), IVT = 0,14 refers to the index of PCT\_NAT\_VEG on the surface dataset while IVT = 15,18 refers to the index of PCT\_CFT on the surface dataset. These plant types differ in leaf and stem optical properties that determine reflection, transmittance, and absorption of solar radiation ([Table 2.3.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Surface_Albedos/CLM50_Tech_Note_Surface_Albedos.html#table-plant-functional-type-optical-properties)), root distribution parameters that control the uptake of water from the soil ([Table 2.11.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Plant_Hydraulics/CLM50_Tech_Note_Plant_Hydraulics.html#table-plant-functional-type-root-distribution-parameters)), aerodynamic parameters that determine resistance to heat, moisture, and momentum transfer ([Table 2.5.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fluxes/CLM50_Tech_Note_Fluxes.html#table-plant-functional-type-aerodynamic-parameters)), and photosynthetic parameters that determine stomatal resistance, photosynthesis, and transpiration ([Table 2.9.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Photosynthesis/CLM50_Tech_Note_Photosynthesis.html#table-plant-functional-type-pft-stomatal-conductance-parameters), [Table 2.9.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Photosynthesis/CLM50_Tech_Note_Photosynthesis.html#table-temperature-dependence-parameters-for-c3-photosynthesis)). The composition and abundance of PFTs within a grid cell can either be prescribed as time-invariant fields (e.g., using the present day dataset described in section 21.3.3) or can evolve with time if the model is run in transient landcover mode (Chapter [2.27](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Transient_Landcover/CLM50_Tech_Note_Transient_Landcover.html#rst-transient-landcover-change)).

Table 2.2.1 Plant functional types[¶](#id15 "Permalink to this table")   
| IVT
 | Plant functional type

 | Acronym

 |
| --- | --- | --- |
| 0

 | Bare Ground

 | NET Temperate

 |
| 1

 | Needleleaf evergreen tree – temperate

 | NET Temperate

 |
| 2

 | Needleleaf evergreen tree - boreal

 | NET Boreal

 |
| 3

 | Needleleaf deciduous tree – boreal

 | NDT Boreal

 |
| 4

 | Broadleaf evergreen tree – tropical

 | BET Tropical

 |
| 5

 | Broadleaf evergreen tree – temperate

 | BET Temperate

 |
| 6

 | Broadleaf deciduous tree – tropical

 | BDT Tropical

 |
| 7

 | Broadleaf deciduous tree – temperate

 | BDT Temperate

 |
| 8

 | Broadleaf deciduous tree – boreal

 | BDT Boreal

 |
| 9

 | Broadleaf evergreen shrub - temperate

 | BES Temperate

 |
| 10

 | Broadleaf deciduous shrub – temperate

 | BDS Temperate

 |
| 11

 | Broadleaf deciduous shrub – boreal

 | BDS Boreal

 |
| 12

 | C3 arctic grass

 | 

 |
| 13

 | C3 grass

 | 

 |
| 14

 | C4 grass

 | 

 |
| 15

 | C3 Unmanaged Rainfed Crop

 | UCrop UIrr

 |
| 16

 | 1C3 Unmanaged Irrigated Crop

 | UCrop Irr

 |
| 17

 | 2Managed Rainfed Crop

 | Crop UIrr

 |
| 18

 | 2Managed Irrigated Crop

 | Crop Irr

 |

1Only used if irrigation is active (Chapter [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)). 2Only used if crop model is active (see Chapter [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) for list of represented crops).

