– 0.2 0.2 – 0.3 0.3 – 0.4 – 0.5 0.5 – 0.6 0.6 – 0.9 Fraction of Photosynthetically Active Radiation FPAR
39
Figure 4.4 Time series of annual distribution FPAR value in Sumatra
The first group of FPAR ranges from 0.1 to 0.2. Estimation result values of this group show with stable graph and with percentage from 1.4 to 5.8.
Increase value occurred in year 2002 with peak percentage to 5.8. This group value indicated as canopy photosynthesis in sparsely vegetation occurred in
surrounding settlement areas or inside urban areas. The second group of FPAR ranges from 0.2 to 0.3. Estimation results of
this group show stable graph with percentage from 8.6 to 15.3. High percentage value occurred in 2002 and low value occurred in 2008. Canopy
photosynthesis estimation has increased about 4.4 during year 2001 to 2002. However, during 2002 to 2003 canopy photosynthesis estimation has decreased
about 5.9. Fluctuation values of this group have affected from climate variability. In normal climate condition or non El Nino year, canopy
photosynthesis increase meanwhile in abnormal climate condition canopy photosynthesis decrease, for example when El Nino event occurred, the vegetation
are susceptible from fires and usually followed with vegetation fires. This condition affected to reduced canopy photosynthesis and as the result annual
estimation after El Nino years show with decreased FPAR value. The third group of FPAR ranges from 0.3 to 0.4. Estimation results of this
group show fluctuated graph and with percentage from 16.6 to 24.3. High percentage value occurred in 2002 and 2006 24 and 24.3 and low value
0.0 5.0
10.0 15.0
20.0 25.0
30.0 35.0
40.0
2001 2002
2003 2004
2005 2006
2007 2008
2009
Pe rc
ent ag
e of
FP A
R V
al ue
Year Periods
Annual Distribution of FPAR Value Over Sumatra, 2001 - 2009
FPAR 0.1-0.2 FPAR 0.2-0.3
FPAR 0.3-0.4 FPAR 0.4-0.5
FPAR 0.5-0.6 FPAR 0.6-0.9
40 occurred in 2008 16.3. Fluctuated result of this group during normal climate
condition non ENSO or abnormal climate condition ENSO has showed with increase or decrease FPAR value and it has affected by climate variability.
The fourth group of FPAR ranges from 0.4 to 0.5. Estimation results of this group show fluctuated graph and with percentage from 18.2 to 26.6. High
percentage value of this group occurred in 2006 26.6 and low value occurred in 2002 18.2. During El Nino event has abundance of sun radiation and it has
caused with increase photosynthesis, increase vegetation density and canopy cover and that is why the highest FPAR value occurred. However, the ENSO year
always followed by fires event and it has affected to vegetation and as the result is decreased in FPAR value as shown in year 2002.
The fifth group of FPAR ranges from 0.5 to 0.6. Estimation results of this group show fluctuated graph and with percentage from 12.5 to 25.3. High
percentage value occurred in 2001 25.3 and low value occurred in 2002 12.5. During 2001 FPAR value sharply decreased and as the result is low
FPAR value in 2002. Transition value from high to low FPAR value in this group are correlated with human management practices in conversion forest land into
non forest land. The sixth group of FPAR ranges from 0.6 to 0.9. Estimation results of this
group show fluctuated result and with percentage from 10.2 to 33.8. High percentage value occurred in 2008 33.8 and low value occurred in 2006
10.2. Transition value from high to low FPAR value in this group are correlated with human management practices in conversion forest land into non
forest land. Meanwhile transition from low percentage value to high values during 2006 to 2008 has indicated of young vegetation has grown to be mature
vegetation. Result of FPAR estimation has shown fluctuation of canopy
photosynthesis. There are other factors can affect the fluctuation of canopy photosynthesis such are photosynthetic efficiency of plants, influencing such as
in-situ environmental conditions; soil moisture, water table position, nutrient availability and weather conditions.
41 Monthly average values of FPAR is relatively constant and has range
value between 0.4 – 0.6. Normally FPAR values should fall between 0 and 1,
however on a number of occasions FPAR values were greater than 1 which usually related to sensor failure. FPAR estimation result has given information
about pattern of monthly average FPAR which could be used to explain about growing season length during normal climate condition or during abnormal
climate condition. The pattern of growing season is started to increase on April and decrease in October.