– 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.

4.3 Optimal Temperature and Water Deficit

Monthly minimum and maximum temperature and precipitation from this data source are used analysisforecast system to perform data assimilation data from 1979 to near present. Temperature and precipitation data from this source has provided for global gridded with spatial coverage of 1.875-degree latitude x 1.875-degree longitude global grid of monthly anomalies of observed precipitation and temperature. Climatic data were provided in the UniData netCDF network Common Data Form format. In this study, temperature and precipitation data has selected into the same years of analyses with MODIS EVI and FPAR data. Time series of monthly temperature and precipitation are used data from 2001 – 2009. Figure 4.5 and 4.6 show monthly average of climatic data precipitation and temperature. Monthly average precipitation in Sumatra ranges between 100 mm to 500 mm. During normal year, precipitation values increased until May period and begin to decrease in June. However, lowest precipitation value occurred in July and August. During El Nino event, precipitation value increased in February and lowest precipitation value occurred in July to October. During La Nina event, high precipitation value increased in May and lowest value occurred in July and August but precipitation started to increase in September. 42 Figure 4.5 Time series of monthly average of precipitation The monthly average temperature in Sumatra ranges between 26°C to 28°C. The pattern of monthly average temperature showed that monthly temperature in Sumatra reach highest temperature value during May and June. Figure 4.6 Time series of monthly average temperature Monthly temperature and monthly water deficit used to provide information of T scalar and W scalar . T scalar is computed with reference to derivation of optimal temperatures T opt for plant production. W scalar is the effect of water deficit on plant photosynthesis. The result of estimation T scalar and W scalar as shown in mean T scalar and W scalar in Figure 4.7. 50 150 250 350 450 550 P re ci pi tat ion m m m on th Monthly Period Monthly Average Precipitation Over Sumatra, Year 2001 - 2009 Mean Rainfall 26 26.5 27 27.5 28 T em pe rat ur e o C el ci us Monthly Period Monthly Average Temperature Over Sumatra, Year 2001 - 2009 Mean Temp