1. General Model Information
Name: Mapped Atmosphere Plant Soil System
Main medium: aquatic+terrestrial
Main subject: biogeochemistry
Organization level: ecosystem
Type of model: 3D
Keywords: hydrology, vegetation characteristics, water balance, biogeography, water-balance, runoff, transpiration, forest, grassland,savannah, shrub steppe, desert, ecotone, leaf area Index (LAI).
Ronald P. Neilson or Jesse Chaney
USFS/ PNW, Global Change Program
Forest Science Lab 3200
Southwest Jefferson Way
Corvallis, OR 97331
Phone: 503 750-7303
Fax: 503 750-7329
MAPSS (Mapped Atmosphere Plant Soil System) is a predictive and
deterministic point model used to examine the relationship between
vegetation growth and distribution, and site water-balance.
It is being developed by Ron Neilson at the USFS/PNM Global Change
Program Office in Corvallis, Oregon. The model is to be used as a
General Vegetation Model (GVM) which could be linked to Global Circulation
Water-balance calculations include snow dynamics, evapotranspiration, and
The input requirements are:
- monthly precipitation,
- average temperature,
- humidity and
- wind speed data.
The model also requires soil texture information.
The output of the model includes vegetation characteristics (such
as leaf area index of trees, shrubs and grasses), monthly soil
moisture and monthly surface and base flow for total runoff. The
model is executed in monthly and annual time steps.
The model has been calibrated by executing it at many sites. It has been
used to predict vegetation characteristics over the conterminous U.S.
at 10 km resolution.
Author of the abstract:
Validation Procedures: 1) Calibrated at 1211 sites to observed vegetation and runoff. 2) Predicted
vegetation at ca. 80,000 pixels (10 km. resolution) on a digital elevation model over contiguous U.S. with
high level of accuracy of prediction. (3) Predicted global vegetation and runoff (0.5 degree resolution) with
high degree of accuracy (Neilson, R. J. and D. Marks, 1995.J. Veg. Sci. 5:715-730)
How Model Functions: Calculates site water balance (snow dynamics, evapotranspiration, runoff,
change in soil storage). Evapotranspiration is a function of LAI and stomatal conductance. Measures
competition between tree or shrub vegetation and grass for both light and water over 3 layer soil.
Iteratively calculates the LAI and woody / grass mixture to just use up soil moisture during growing
For an extended Abstract see here
II. Technical Information
Operating System(s): UNIX Computer Requirements: Approximately 28 hours of CPU on a SPARC 2 over the contiguous U.S. (ca.80,000 points) or ca. 3 hours if distributed over a network of over 20 SPARC stations.
Programming Language(s): C
III. Mathematical Information
Infiltration, and saturated and unsaturated percolation, are represented by an analog of Darcy's Law specifically calibrated to a monthly time step. Water holding capacities at saturation, field potential, and wilting point are calculated from soil texture, as are soil water retention curves (Saxton et al., 1986). Transpiration is driven by potential evapotranspiration (PET) as calculated by an aerodynamic turbulent transfer model based upon Brutsaert's (1982) ABL model (Marks and Dozier, 1992; Marks 1990), with actual transpiration being constrained by soil water, leaf area and stomatal conductance. Stomatal conductance is modulated as a function of PET (a surrogate for vapor pressure deficit) and soil water content (Denmead and Shaw 1962). Canopy conductance ( i.e., actual transpiration) is an exponential function of LAI, modulated by stomatal conductance.
Monthly precipitation data, mean temperature, humidity andwindspeed. Soil texture in 3 layers.Model Input Data Source: NCDC meteorologic data, SCS SNOTEL data, DOE windspeed data(quarterly), airport humidity data, SCS and FAO soils data. All data has been interpolated or modeled(rainfall) to a 10 km resolution digital elevation model. Vegetation classification (monthly), LAI of trees, shrubs, grasses (phenology);
Vegetation classification (monthly), LAI of trees, shrubs, grasses (phenology);monthly soil moisture in three layers, monthly surface and base flow for total runoff; monthly stomatalconductance; indices of productivity and water-use-efficiency.
Temporal Scale: Monthly and annual time-steps.
Spatial Scale: This is a 1-D model. Currently 10 km to 0.5 degree grid cells. MAPSS is being implemented in 3-D with 30 km grid cells.
Neilson, R.P. 1995. A Model for Predicting Continental Scale VegetationDistribution and Water Balance. Ecol. Applic. 5:362-385
Neilson, R. J. and D. Marks, 1995.A global perspective of regional vegetation and hydrologic sensitivities from climatic change.J. Veg. Sci. 5:715-730
V. Further information in the World-Wide-Web
VI. Additional remarks
Global change implications:This model is intended to be usedfor global change research and to be linked to GCMs. It will examine the effecs of climate change on many different types of forests in the United States.
Source : CIESIN Report
Last review of this document by: T. Gabele: 18. 07. 1997
Status of the document:
last modified by
Tobias Gabele Wed Aug 21 21:44:45 CEST 2002