Estimation of NPP for Sumatra

46 In year 2001, total estimation of NPP is 1414 g C m -2 yr -1 . In year 2002, total estimation of NPP is 1475 g C m -2 yr -1 . In year 2003, total estimation of NPP is 1369 g C m -2 yr -1 . In year 2004, total estimation of NPP is 1399 g C m -2 yr -1 . In year 2005, total estimation of NPP is 1417 g C m -2 yr -1 . In year 2006, total estimation of NPP is 1227 g C m -2 yr -1 . In year 2007, total estimation of NPP is 1510 g C m -2 yr -1 . In year 2008, total estimation of NPP is 1367 g C m -2 yr -1 . In year 2009, total estimation of NPP is 1404 g C m -2 yr -1 . Figure 4.8 show trends of annual distribution NPP over Sumatra. Figure 4.8 Trends of annual distribution NPP in Sumatra Estimation result of annual NPP distribution has shown fluctuated graph. NPP values slightly increased 62 g C m -2 yr -1 during year 2001 to 2002, NPP values decreased 106 g C m -2 yr -1 during 2002 to 2003. The NPP values slightly increased again in years 2003 to 2004 with increased value to 30 g C m -2 yr -1 and in year 2004 to 2005 increase NPP value to 18 g C m -2 yr -1 . Meanwhile in year 2005 to 2006, NPP value decreased sharply about 192 g C m -2 yr -1 and this was the highest decrease NPP value during nine year monitoring period. In years 2007 to 2008 with value 283 g C m -2 yr -1 and this was the highest increase valued during this nine year monitoring period. In years 2007 to 2008 NPP value decreased to 143 g C m -2 yr -1 meanwhile in years 2008 to 2009, NPP values increased again up to 30 g C m -2 yr -1 . Figure 4.9a show the differences of NPP distribution in Sumatra during normal and abnormal climate event January 1000 1200 1400 1600 2001 2002 2003 2004 2005 2006 2007 2008 2009 Y ear ly N P P g C m -2 yr -1 Yearly Periods Trends of Annual Distribution of NPP in Sumatra NPP Total 47 Period. Figure 4.9b show the differences of NPP distribution in Sumatra during normal and abnormal climate event September Period. Figure 4.9a Maps of comparison monthly average NPP distribution in Sumatra during normal and abnormal climate event January period 48 Figure 4.9b Maps of comparison monthly average NPP distribution in Sumatra during normal and abnormal climate event September period NPP distribution value ranges from 0 to 150. Low NPP values show in white and purple color. Medium NPP values show in blue and green color and high NPP values show in orange and brown color. 49 During normal year, precipitation value increased until to May period and decrease in June. However, low precipitation value occurs on July and August. Meanwhile in El Nino event, high precipitation value increased in February and the lowest precipitation value occurred in July to October. In La Nina event, high precipitation value increased in May and the lowest precipitation value occurred in July and August however in September period the precipitation started to increase. NPP distribution of normal climate event is used NPP estimation data in year 2005. Two monthly periods have selected to provide the differences of NPP distribution and the period is January and September. During normal or abnormal climate condition precipitation still occurred in January. However, during normal climate event precipitation also occurred in September, meanwhile limited precipitation occurred during September in abnormal climate event. As show in Figure 4.9a NPP distribution occurred in northern, northeast, northwest and southwest of Sumatra Island, also in western part of the Island NPP distribution occurred during January. In the same monthly period, in middle and southern part Sumatra Island, NPP distribution occurred and dominated by medium and low NPP value. This condition related to precipitation. In northern part of Island, temperature and water has optimal value for plant growth and photosynthesis and it caused NPP distribution occurred with dominated by high value. Conversely, in middle and southern part of Island, temperature and water has not in optimal value for plant growth and photosynthesis and it caused NPP distribution occurred but dominated with medium and low values. However, in September period as show in Figure 4.9b, NPP distribution over Sumatra has changed. During normal climate condition, NPP distribution almost occurred in any part of the Island, except in southern part of the Island. During abnormal climate condition in year 2006 El Nino event, NPP distribution has changed during El Nino event. In northern and central part of Sumatra Island, temperature and water has not in optimal value for plant growth and photosynthesis and it caused NPP distribution occurred but dominated with medium and low values. However, in southern and western part of the Island, NPP has increased, this condition related to optimal precipitation and temperature for plant growth and photosynthesis over the area. Furthermore, during abnormal 50 climate condition in year 2007 La Nina event, part of northern and southern of Sumatra Island, NPP distribution occurred with medium value meanwhile in central and other southern part of Island has dominated with high NPP value. Figure 4.10 show the differences of EVI distribution during normal and abnormal climate event. Figure 4.10 Maps of comparison monthly average EVI distribution in Sumatra during normal and abnormal climate event 51 Another explanation regarding compared result of NPP distribution could be explained using other information for example with used the differences of Enhanced Vegetation Index. Result of differences between one image with other image are using subtract method from one image to other. For example, monthly EVI image in January during abnormal climate condition El Nino or La Nina subtracted with monthly EVI image in January during normal climate condition. Result of subtracted EVI in January and September as show in Figure 4.10. Figure 4.10 show result of EVI differences during normal compare to abnormal climate condition. Dark green color indicated as high level of vegetation greenness and also indicated as increased change of vegetation over the areas. However, purple color indicated as low level of greenness vegetation and also indicated as decreased change of vegetation over the areas. Compared result of EVI during monthly January in El Nino event has shown with increased of vegetation greenness almost occurred over the Island and during September in El Nino event has shown with decreased of vegetation greenness in northern part of Sumatra. However, vegetation greenness has increased in middle part of Sumatra Island. During monthly January in La Nina event has shown with increased of vegetation greenness occurred over the Island and during September in La Nina event has shown with increased occurred in middle part of Sumatra and decreased vegetation greenness occurred in southern part of the island. Result comparison of EVI and NPP distribution related connection. For example in January period during normal or abnormal climate condition, EVI and NPP distribution occurred almost in part of Sumatra Island. Meanwhile, other example in September period during normal or abnormal climate condition, EVI and NPP distribution occurred in some part of Sumatra Island. As stated previously, EVI and NPP distribution has related with precipitation and temperature for optimal plant growth and photosynthesis. Transition of NPP distribution or EVI has moved from north to south during normal to abnormal climate condition. This moved also affected by water availability. Limited of waters condition because of high temperature regulates the 52 evapotranspiration and thus influences the variation of soil moisture and this condition affected to limited photosynthesis activity. In this case, local climate variability has major influenced in NPP distribution and EVI. Some areas which have optimal precipitation and temperature will increase in NPP distribution. Figure 4.11 Monthly average of distribution NPP in Sumatra Estimation result of monthly average of NPP distribution is important to do. Using monthly average information will derive information about trends of the monthly NPP distribution in Sumatra. Figure 4.11 show trends of average NPP distribution over Sumatra during 2001 – 2009. Analysis and estimation of average distribution NPP has derived information about the correlation between NPP with seasonal effect. In year 2001, 2002, 2004 and 2006, average distribution NPP increased from April to October. However in year 2003 and 2005, 2007, 2008 and 2009 average distribution of NPP increased from January to October. Highest average distribution of NPP during nine-year monitoring of estimation NPP occurred in April 2009 with monthly average NPP in Sumatra reach to value 74.1 g C m -2 yr -1 and followed in month of April 2007 with the monthly average NPP value reach to 65.6 g C m -2 yr -1 . 20 40 60 80 N P P V al ue Monthly Period Monthly Average NPP Value Over Sumatra, Year 2001 - 2009 Mean NPP 53

4.4.2. Correlation of NPP with Climate Variability

Historical of climate data show that Sumatra terrestrial has experienced substantial with inter-annual variations and spatial variations in temperature and rainfall during the study period and tightly associated with ENSO. However, ENSO has correlated with temperature and precipitation. Correlation between NPP and climate variability in this study are used estimation data during normal year in 2005 and during ENSO year 2006 El Nino Event and 2007 La Nina event as shown in Figure 4.12. Figure 4.12 Relation between NPP and Precipitation and Temperature data in Sumatra 25.5 26.5 27.5 28.5 20 40 60 80 M on thl y av er ag e te m pe ra tur e M on thl y av er ag e N PP Monthly Period Correlation between monthly average NPP and temperature Mean NPP Mean Temp 25 26 26 27 27 28 28 29 10 20 30 40 50 60 70 80 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100103106 M on th ly M ea n Te m pe ra tu re M ea n M on th ly N PP g C m -2 y r- 1 Relation Between NPP and Temperature In Sumatra, During 2001-2009 Mean NPP Mean Temperature 54 During normal year, average maximum temperature reached on June and other monthly period temperature was decreased. However, average maximum of precipitation reached on May and other monthly period until July the precipitation was decreased, meanwhile in the August to October the precipitation was increased. Distribution NPP value show increased in April and in other monthly period until August the NPP distribution was stable. Increased of NPP occurs in September followed with increasing in precipitation. During El Nino year, average maximum of temperature reached on May and other monthly period temperature was decreased. However, average maximum of precipitation reached on June and other monthly period until October the precipitation was decreased, meanwhile in the October to November the precipitation was increased. The distribution NPP value show increased until May and in other monthly period until October the NPP distribution was decreased. Increased of NPP occurs in October to December followed with increasing in precipitation. During La Nina year, average maximum of temperature reached on May and other monthly period temperature was decreased. However, average maximum of precipitation reached on March and other monthly period until July the precipitation was decreased, meanwhile in the July to November the precipitation was increased. The distribution NPP value show increased in March and in other monthly period until July, the NPP distribution was decreased. However, increased of NPP distribution occurs in August followed with increasing in precipitation during this period. However, the effects of ENSO to the temporal changes of NPP are small. In comparison to the temperature sensitivity of NPP, the variability of NPP responses to the historical precipitation was much higher. Refer to the measurement result of NPP estimation in previously explained that decrease in NPP distribution is mainly related to the precipitation and temperature. Decrease in precipitation will make drought intensified, and affected to limit the photosynthesis. Meanwhile, the increase in temperature makes respiration and consumption increase, resulting in NPP decline. Therefore, increasing