Influence of greater Nitrogen
Deposition in Missoula, MT
Anne Trainor
Exercise 3
October 2, 2007
Introduction

Substantial increase of nitrogen deposition since
the industrial boom


large impacts on forested ecosystems.
Objective:

Examine how a significant increase in nitrogen could
influence annual and seasonal nutrient cycling
dynamics within an evergreen forest.
Study System



Missoula, MT
Meteorological Data: 1950-1993
1 m Loamy Soil


30% sandy, 50% silt, 20% clay
Evergreen Needleleaf system

Used all defaults
Modeling


Biome-BGC (version 4.1.2)
Carbon levels constant at default value
(294.842 ppm)

Consisted of 3 runs for 88 years



A) Spin up: Default pre-industrial nitrogen level (0.0001
kgm2yr1)
B) Typical Nitrogen: Based off previous Spinup ran
simulation with default pre-industrial nitrogen level (0.0001
kgm2yr1)
C) Increased Nitrogen: Based off original Spinup ran
simulation with Nitrogen increased to 0.005 kgm2yr1
Methods
Selected a consecutive dry and wet year to compare extremes
1980 and 1981
1973 and 1974
Relevant Variables Modeled
Variables
Annual
Maximum LAI
LAI
NPP
NPP
GPP
Soil carbon fluxes
(SoilC 1-4)
Litter stores
(LitterC 1-4)
Leaf water potential
Evapotranspiration
Daily