Information Extraction And Analysis Of Spectral And Physicochemical Parameters Of Nanhui Tidal Flat Advantage Vegetation In The Yangtze River Estuary

Beach vegetation is advantage vegetation communities in the silt tidal flat, the environment is high salinity and high soil moisture. Vegetation can be classified in different growing environment, environmental factors such as light, temperature and rainfall all can affect growth and distribution of vegetation, therefore, different environment and climate formed different plant community composition. Different types of vegetation has an important influence with local soil and the environment, changes of physiological indexes may reflect changes of the local environment, so the research of vegetation is conducive to better understand the state of the environment in some areas. Remote sensing technology is macro, low cost, fast and dynamic. It has become one of the main means of obtaining vegetation information.Nanhui tidal flat at the intersection of the Yangtze River estuary and Hangzhou Bay, was formed by the Yangtze River estuary sediment long-term accumulation, is a typical silt tidal flat environment. In recent years, human development and the construction of dams in Nanhui district, making Nanhui tidal natural environment has been destroyed. Outside and inside of the dam tidal flat environment have produced a significant difference, the primarily advantage vegetation of outside dam are Phragmites australi and Scirpus mariqueter, the primarily advantage vegetation of inside dam are Spartina alterniflora and Solidago decurrens Lour..Field collected spectral data and three physicochemical indexes, such as soil moisture、 SPAD and PAR, in the growing environment of four dominant vegetation. Using first derivative technique to get the vegetation spectral information, compared the spectral information of different vegetation, and analyzes the impact of physicochemical indexes for each of the three vegetation spectral curve. Obtaining the following aspects in the research process:(1)Taking the dominant canopy species Phragmites australis and Scirpus mariqueter of Nanhui tidal flat in the Yangtze Estuary as research objects, five calculation methods of extracting the red edge position were compared and analyzed, including polynomial fitting, four-point interpolation, first derivative technique, Lagrange interpolation and linear extrapolation. The four test areas have different Soil moisture. The results show that, the polynomial fitting to obtain the highest accuracy and the maximum sensitivity to the soil moisture; the four-point interpolation method on soil moisture sensitivity greater; the linear extrapolation obtained unstable red edge position; the first derivative technique and Lagrange interpolation have the minimum sensitivity to soil moisture, more suitable for obtaining the vegetation red edge position in such high soil moisture Nanhui tidal flat area.(2)Analysis of the spectral data of Phragmites australis, Scirpus mariqueter, Spartina alterniflora and Solidago decurrens Lour., the results showed that, vegetation in the growth peak, the spectral reflectance of corresponding wavelength is higher, the gap of Red edge slope of Phragmites australis and Scirpus mariqueter is obvious, red edge slope is the best spectral parameter to distinguish the two vegetation, the Green Peak reflectance, YEP and red edge slope can be the parameters to distinguish Spartina alterniflora and Solidago decurrens Lour..(3)Analysis of the effects of different soil moisture, SPAD and PAR on vegetation spectra, found that, soil moisture affect the spectral reflectance of Phragmites australi, Scirpus mariqueter and Spartina alterniflora, as the SPAD was similar, the soil moisture increased, the corresponding spectral reflectance of vegetation were lower, Solidago decurrens Lour. is less sensitive to soil moisture, as the soil moisture was similar, the Green Peak reflectance increased, the Red Valley absorption rate dropped, the REP moved to right, PAR can promote leaf green synthesis for beach vegetation, indirect effect the spectral curve, in the higher PAR environment, vegetation is greater, red edge slope is increased.