Spatio-temproal Simulation Of Forest Net Primary Productivity And Its Influencing Factors

Forest ecosystem is one of the most important parts of the global carbon cycle.Vegetation net primary productivity(NPP)is the key parameter on reflecting the terrestrial vegetation carbon fixation capacity and terrestrial ecological processes;it's also the independence part of understanding of surface carbon cycle.NPP which has been used to judge the carbon sink effect of ecosystem could directly reflect the production capacity of terrestrial vegetation in natural conditions.Therefore,NPP has special significance to estimate the support capacity of the earth and sustainable development of terrestrial ecosystem.This study estimates vegetation NPP using CASA model,geographic information system and remote sensing technology,combined with Landsat TM remote sensing images,CRU meteorological data,and forest distribution map of Tuqiang Forestry Bureau of Da Hinggan Mountains in July during the 1987 to 2011.References to relevant research and detailed analysis,the main conclusions are as follows:As a result of the fire in 1987,the forest was burned down and NPP production has been severely reduced.After that,the diversity of NPP yield between north and south area was remarkably.The northern region appeared a large area of lower NPP yield and the diversity was weakening gradually until 2005.Since 1988,NPP yield has gradually recovery and reached peak level at 5.748×1011gC.The data shows that the total value of NPP output in July could be more than 5.6×1011gC.NPP statistical analysis of different tree species shows the main source of NPP production of Tuqiang Forestry Bureau in July is the white birch.The NPP yield of white birch is about 50.1% of the total output value while larch and Mongolian Scotch were approximately 34.6% and 9.9%,respectively.In the unit NPP production value is also birch > Larch >Mongolian Scotch.The control experiment shows that both the vegetation elements and rainfall factors impact the production.When the rainfall is insufficient,the yield could be reduced while the rainfall exceeds the fitness value could do no change of the yield because of the absorption of vegetation on the water has the most fitness value.The vegetation element has higher influence on the net primary productivity of the ecosystem.If the forest vegetation decreases rapidly due to natural disasters or human factors,it will affect the ecological balance of the region.After five years of artificial forest planting in 1988,the forests recovered slowly and began better from the beginning of 1993 when the difference of NPP value betweenburned areaand the no fire zone is gradually narrowing.By 2009,it had almost no difference which means the forest vegetationof burned area has been completely restored.The forest NPP reached the average value after 21 years shows the NPP production of the forest recovered slowly after the fire.