Remote Sensing Research On NPP Of Regions In Jilin Province Based On CASA Model

Since the industrial revolution, rapid economic development of mankind makes the content of CO2 in air increased, at the same time, causing many environmental problems, so international environmental organizations launched a series of studies. Among them, the carbon cycle associated with the mobile of C element of land, air, rocks and other circles, the capacity of carbon sequestration is particularly important. Vegetation is an integral part of human environment, through photosynthesis, vegetation converts light into chemical energy and stores in plant, which is the only way of converting CO2 to O2 naturally. So, vegetation plays an important role in terrestrial carbon circle.Net Primary Productivity, which can be understood as the difference between photosynthesis products and respiration, stands for the quantity converting from light to organic. Therefore, NPP directly relates to the terrestrial ecosystems in land-atmosphere carbon cycle and the CO2 fixation capacity, thereby affecting other aspects of the carbon cycle.Carrying out research on NPP, is helpful for understanding the impact of environmental factors contribute to human life, understanding the photosynthesis constraints of different types of plants, accordingly, we can grasp the development potential of environment, promote cultivation of plants that possess carbon sequestration capacity, it also provides a clear understanding and necessary decision support for environment management and research.In this thesis, using TM/ETM+ remote sensing data to extract the vegetation cover/land use information, get the distribution pattern of vegetation and other surface feature elements of different phases, and conduct statistical analysis; based on remote sensing data, access to classified Vegetation Index (NDVI, Normalized Difference Vegetation Index)for growth conditions,comparison different geographical landscapes and different time; using NDVI information combined with the land-surface meteorological observation data (monthly mean temperature, monthly total precipitation, monthly total solar radiation,etc.) of different time, take CASA (Carnegie-Ames-Stanford Approach) model as a tool to estimate the NPP of western, central, and eastern typical regions in Jilin Province, visually displayed the relationship between vegetation coverage, growth state and NPP, analyzed the changes of NPP under different seasons in same region; the total distribution feature of NPP combined with the vegetation in different regions and landscape features; explained NPP of different vegetation types.By researching on the previous studies, we carried out the NPP research of typical regions in Jilin Province based on CASA model. Mainly made the following conclusions:(1) Through study and research, remote sensing information extraction will be restricted by remote sensing data, the higher resolution data, the higher accuracy. Parameters are related to remote sensing data,a continuous time series will be more helpful for researching.(2) For the existing phases, the overall distribution of NPP in three typical landscape of eastern, central and western regions is: Changbai Mountain forest month maximum is 96.64g C?m-2?month-1, Central Plain area month maximum is 62.77g C?m-2?month-1, Western Salt lakes, Desertification area month maximum is 50.41g C? m-2?month-1. the distribution feature is: Changbai Mountain forest area>Central Plain area>Western Salt lakes, Desertification area, this is consistent with the situation of vegetation cover and landscape pattern.(3) For the same study area, the eastern region summer NPP is higher than that in autumn; the central region autumn NPP is higher than that in early winter; the western region early autumn NPP is higher than that in early summer. It can be interpreted from seasonal perspective as: vegetation growth state in summer-early autumn got a crest, it has a high land vegetation cover , good water and heat conditions for plant photosynthesis, however in the beginning of summer or winter, vegetation growth have just started litter, or crop harvest has completed, which resulted in sparse vegetation, and low coverage, the radiation absorption ratio that absorbed by vegetation layer decreased, this can be considered as the main reason for the low NPP values.(4) By researching on NPP of different regions, we could identify ways to improve the productivity of ecological systems: coordination and increase the supply of water required for photosynthesis; foster and promote high-yielding new varieties to fully use the solar energy, and improve photosynthetic efficiency and light utilization; widely cultivate the good vegetation to improve the capability of carbon sequestration for ecological system, and then we can grasp the ecological state of the environment, understand the development potential of the landscape in different environment, ensure the mechanism of carbon cycle, make programming for typical regions of different geographical landscapes to improve the effectiveness of environment, provide suggestions for reference and decision-making cognition.