Interaction of Climate Change and Acid Deposition - Climate Change Impacts on Freshwater Ecosystems - page 171

Table 7.1 Summary of the relative importance of factors drivers by climate change
that affect soil and water acidification. (Modified from Wright et al . 2006.)

Potential effect on
ANC

Relationship
to climate Factor Importance

Sea salts Decrease Coastal sites only Empirical links to

NAO

Dust Increase Southern sites only Empirical links to

NAO

Runoff Increase Medium Precipitation,

temperature from
GCMs

Weathering Increase Low Temperature, from

GCMs

Organic acids No change High Poorly understood

Soil pCO 2 No change Low From GCMs

Forest growth Decrease Low Temperature,

moisture, pCO 2 ,
complicated

Organic matter
decomposition

Decrease High Temperature,

moisture, complicated

potential effect of climate change on soil and water chemistry. Wright et al .
(2006) used MAGIC to examine the relative sensitivity of eight major climate-
sensitive processes on the recovery of soil and water from acidification (Table 7.1).
They found that several of the factors are of minor importance, several are
important only in specific areas and several are of widespread importance. The
effect of climate change on production and loss of organic acids is one of the
important processes, and mineralization and loss of N from soil is another.
This exercise simply tested the relative importance of various processes and did
not involve the use of actual climate scenarios in projecting future response in soil
and water chemistry. Hardekopf et al . (2008) took the next step and used the best
available information to set the rates and parameter values for several of the key
climate-driven processes in MAGIC to project future acidification and recovery at
Litavka, a small catchment in the Czech Republic. Their simulation included the
temperature dependence of weathering rate, DOC release from soil, net soil N
mineralization and forest growth. They used several future climate scenarios
derived from GCMs and downscaled to the Litavka site. They concluded that
future climate change will have little effect on chemical recovery at this site.
Evans (2005) took another approach and used empirical statistical
relationships between climate variables and observed streamwater chemistry at
Afon Gwy, a small stream in Wales, the United Kingdom, to set parameter values
and rates in MAGIC for evaluation of future climate scenarios. Evans used three
empirical relationships: (i) discharge as a function of rainfall and temperature;
(ii) sea-salt deposition as a function of the North Atlantic Oscillation Index
(NAOI); and (iii) stream concentrations of DOC as a function of summer