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Research For The Influenting Factors And Model Of Light Use Efficiency Estimated By Physiological Reflectance Index

Posted on:2016-05-28Degree:MasterType:Thesis
Country:ChinaCandidate:J X WangFull Text:PDF
GTID:2180330470477354Subject:Forest management
Abstract/Summary:PDF Full Text Request
Light Use Efficiency(LUE) as a key variables to estimate the NPP, the model based on LUE has become the main method in large scale. It is important to research the energy distribution and the global environment change with the reliable LUE. With hyperspectral remote sensing, many experts found that Physiological Reflectance Index(PRI) was a great tool to investigate the energy distribution of LUE.The factors which affect the relationship between LUE and PRI were researched.,combined the field observation and simulation of radiative transfer model. The models were established to estimate LUE with six types of PRI, and the best was selected according to the relativity between LUE and PRI. The main contents include: 1) Based on the data collected by experiment, the parameters’ sensitivity to the different types of PRI was researched, with PROSAIL model which needed the content of chlorophyll, equivalent water thickness, dry matter quantity, leaf area index, solar zenith angle and the observing zenith angle; 2) Analysised the relationship between different types of PRI and LUE of three kinds wetland vegetation at Hangzhou bay. And based on measuring PRI and LUE of reed with the different nitrogen treatment and water treatment, studied how the external environment impact on PRI and LUE and their relationship; 3) Analysised the correlation between the different types of PRI and LUE, and established the model to estimate the LUE at leaf and canopy leavel respectively.Results showed that:(1) Based on the simulation reflectance by PROSPECT model, mesophyll structure parameter N has a great influence on PRI. PRI570、PRI1、PRI3 and PRI4 have less sensitivity to N value when N has a bigger value, and the sensitivity of PRI2 and PRI5 to N value is more. With the increase of chlorophyll concentration, PRI change is uneven. PRI3 has less sensitivity to the chlorophyll concentration, PRI2 and PRI5 have more sensitivity to chlorophyll. The influence of equivalent water thickness and the dry matter quantity on PRI can be ignored because of the lower influence on the reflectance of visible spectrum;(2) LAI and geometrical angles on canopy scale influence reflectance at all band and significantly effected on PRI. PRI5 is not sensitive to the change of LAI and geometrical angles, the rest of five types of PRI is more sensitive;(3) At the canopy leavel, LAI was less than 5, PRI is sensitive to the ground surface under the canopy, the canopy reflectance can’t be expressed correctly. When LAI > 5, the canopy PRIwas not be influenced, so the PRI remain in a stable state;(4) the PRI and LUE of wetland vegetation have a clear change trend in a day at Hangzhou bay, the correlation between PRI and LUE for the same plant is better than mixed different plants. The relationship between PRI5 and LUE is greater than other PRI type established by the mixed different plants;(5) under different nitrogen treatment conditions, the correlation of PRI3 with LUE is best on leaf leavel; the relationship between PRI5 and LUE is best on canopy leavel. With water treatment, the relationship between PRI5 and LUE was the best compared with other PRI on leaf and canopy leavel;(6) based on the total leaf data, the relationship between PRI3 and LUE was best on leaf leavel, R2=0.4837,the LUE estimated model was: PRI = 0.4662*LUE- 0.0339;(7) on canopy scale, the relationship between PRI5 and LUE was best based on the total canopy data, R2=0.5571, the LUE estimated model was: PRI=-1.8167*LUE-0.2242.
Keywords/Search Tags:Light Use Efficiency, Physiological Reflectance Index, Chlorophyll, Leaf Area Index, Reed, PROSAIL Model
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