LPJ-GUESS is a process-based, dynamic global vegetation model (DGVM) that simulates global and regional dynamics and composition of vegetation in response to changes in climate, land-use change, atmospheric CO2, and nitrogen. The model distinguishes between natural, pasture and cropland, and managed forest land-cover types, all of which include C–N dynamics. Vegetation dynamics in natural land cover are characterized by the establishment, competition, and mortality of 12 plant functional types (PFTs) in a number of replicate patches. Physiological processes like photosynthesis, autotrophic, and soil heterotrophic respiration are calculated in natural and managed ecosystems; a set of carbon allocation rules determines plant growth. Plant establishment, growth, mortality, and decomposition, as well as their response to resource availability (light, nutrients, water), modulate seasonal and successional population dynamics arising from a carbon allocation trade-off. Vertical forest structure is accounted for by the use of different age classes for woody PFTs.

In managed ecosystems, pastures are populated by C3 or C4 grasses which are annually harvested. Croplands are represented by prescribed fractions of five crop functional types (CFTs), which are moderately tilled, fertilized, and harvested, and are prescribed to be either irrigated or rain-fed. The CFT yields are used as input to PLUMv2. Managed forests can be thinned, clear-felled or selectively harvested.

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