Net Primary Production Climate change

II. LITERATURE REVIEW

2.1 Net Primary Production

NPP is a measurement of plant growth obtained by calculating the quantity of carbon absorbed and stored by vegetation. NPP is equal to photosynthesis minus respiration. It is sometimes expressed in grams of carbon per square meter per year. It is a major component of the carbon cycle. Net primary productivity NPP is also defined as the net flux of carbon from the atmosphere into green plants per unit time. NPP refers to a rate process, i.e., the amount of vegetable matter produced net primary production per day, week, or year. It is a tool for measuring forest productivity and establishing carbon budgets. The data obtained by calculating NPP can be used as the basis for estimating the impact of both natural disturbances and management activities on forest productivity, assessing the effects of climate change on forests, and assessing the role that these forests can play in achieving our greenhouse-gas reduction objectives Lobell et al. 2002, Mingkui and Woodward 1998. MODIS NPP is an annual value and provides a means of evaluating spatial patterns in productivity as well as interannual variation and long term trends in biosphere behavior Turner et al. 2006.

2.2 Climate change

Plants capture and store solar energy through photosynthesis. During photosynthesis, living plants convert carbon dioxide in the air into sugar molecules they use for food. In the process of making their own food, plants also provide the oxygen that is very important for human beings. Plant productivity also plays a major role in the global carbon cycle by absorbing some of the carbon dioxide released from the people activities sech as burning coal, oil, and other fossil fuels. The carbon plants absorbed would becomes part of leaves, roots, stalks or tree trunks, and ultimately, the soil. Climate change is a long-term change in the statistical distribution of weather patterns over periods of time that range from decades to millions of years. It may cause a change in the average weather conditions for example greater frequency of rains or longer time of drought season Maslin 2004. Factors that affected the climate are climate forcing such variations in solar radiation, deviations in the earths orbit, and changes in greenhouse gas concentrations. There are a variety of climate change feedbacks that can either amplify or diminish the initial forcing. Some parts of the climate system, such as the oceans and ice caps, respond slowly in reaction to climate forcing because of their large mass. Therefore, the climate system can take centuries or longer to fully respond to new external forcing.

2.3 MODIS