Geoscience Reference
In-Depth Information
0
Fs
i
=
0
∨
AgS
i
=
0
⎨
⎩
(25)
Ftdec
i
=
x
i
Fs
i
>
0
∧
AgS
i
>
0
c
o
x
i
=
(26)
⎛
⎜
⎞
⎟
c
2
Fs
i
+
c
e
AgS
i
+
Pd
i
+
e
−
c
1
+
c
4
⋅
Pd
i
+
c
5
⋅
c
6
⋅
GDP
i
1
+
The deforestation rates (Ft
dec
) were taken from (FAO, 2005), where the forest area
from 1990, 2000, and 2005 for each country was given. For the estimation of the mod-
el parameters the area difference between 1990 and 2005 was used to infer the defor-
estation rate. All values which showed an increase of the forest area have been set to 0,
because the model should only predict the deforestation. Countries with an increasing
forest area have a deforestation rate of 0. It should be mentioned that the change rate is
based on the total land area in the grid i and not on the current forest area.
By using c
2
/F
s
the model can only be used on grid's where there is some share of
forest. This makes sense, because on places where there is no forest, no deforestation
can appear. The model will only be usable on grids where forests occur. Therefore, for
parameterization, the average agricultural suitability and the population density of a
country are also only taken from grids which indicate forest cover.
Development of Forest Share
After calculating the deforestation rate, the forest share has to be updated each year
with equation (27) assuring that the forest share stays within the permissible range of
0-1.
(
)
⎧
fsx
i
,
year
fsx
i
,
year
≤
1
−
Bul
i
+
Crl
i
⎪
⎪
(27)
Fs
i
,
year
=
(
)
(
)
1
−
Bul
i
+
Crl
i
fsx
i
,
year
>
1
−
Bul
i
+
Crl
i
fsx
i
,
year
=
Fs
i
,
year
−1
−
F
i
,
dec
(28)
Aboveground Carbon in Forest Biomass
The model describes the area covered by forests on a certain grid. It can also describe
the forest biomass if the average biomass on a grid is known and the assumption was
made, that the biomass in forests on the grid is proportional to the forest area.
For this reason a global carbon map of aboveground carbon in forest biomass,
was created, based on country values from (FAO, 2005). By dividing the given total
carbon, for each country, with the forest area of the country, the average biomass per
hectare can be calculated. Now the assumption was made, that the stocking biomass
per hectare on sites with a higher productivity is higher than on sites with a low pro-
ductivity. Not for every country with forests (FAO, 2005) gives values of the stocking
biomass. So a regression, describing the relation between tC/ha and NPP, was calcu-
lated and the biomass of grids of missing countries have been estimated to obtain a
complete global forest biomass map.
