Chang Cun

Analysis of the spectral response of flourishing-withering vegetation changes based on ground spectral measurements

A structural mode was used to characterize vegetation composition at the plant leaf level and a flourishing-withering ratio was developed. The spectral responses of vegetation with different flourishing-withering ratios were analyzed, the change rates of the chlorophyll and moisture content indices of vegetation with different flourishing-withering ratios were compared, and correlations between the chlorophyll and moisture content indices were analyzed. The results reveal that leaves with an intermediate flourishing-withering ratio can increase the absorption signatures of vegetation and that band ranges of 570–700 nm and 1300–1540 nm can play a role in indicating changes in the flourishing-withering ratios of vegetation; NPQI, NPCI, R695/R420, R695/R760, R750/R700, the peak-value area of red selvedge, the red selvedge amplitude, the ratio between the red selvedge amplitude and the minimum amplitude, and the NDVI of vegetation change regularly with the change in flourishing-withering ratios, and these nine vegetation indices are highly related to the chlorophyll content. Vegetation indexes of NDWI and PRI are very sensitive to the flourishing-withering change in vegetation and are closely related to the moisture content, and the correlation coefficient is higher than 0.9. The derivative of the spectra is more effective in describing changes in the structural mode of vegetation with different flourishing-withering ratios, especially at band ranges of 552–628 nm and 630–686 nm, and it is more sensitive to the mixed flourishing-withering ratios of leaves rather than to the vegetation indices. The red selvedge position in the spectrum is highly related to the chlorophyll content and is not sensitive to changes in the structural mode of mixed flourishing-withering leaves. The red selvedge parameters are sensitive to changes in the flourishing-withering ratio at the peak-value area of the red selvedge amplitude and the ratio between the red selvedge amplitude and the minimum amplitude. The effect of a sand background on the spectrum of withering leaves is higher than that of flourishing leaves; the effect of a sand background increases with increasing proportions of withering leaves, the superposition effect of the sand background on mixed flourishing-withering leaves is about 7% at visible light bands of 400–700 nm and 1300–1540 nm, and is over 10% at the near infrared band range of 700–1300 nm.

Application of Solar Heating System in Biogas Production

In the biogas production from agriculture manure by anaerobic digestion, it is necessary to keep the bioreactor optimum and steady temperature. The optimum condition usually can not be achieved automatically in winter in North China. The solar water heating system using evacuated tubes with auxiliary electrical heater was adopted to charge the thermal energy to the bioreactor, which made the bioreactor work regularly. It was experimentally investigated that the required solar collector area, the production amount of the biogas and the auxiliary electrical power at the temperature of 15°C, 20 °C and 25 °C of the bioreactor. The biogas production system has been running steadily for two years. As a result, when the daily average solar flux was 13.2 MJ/m2 and the temperature of a bioreactor of 6m3 was optimized to be at (20±1) °C in the coldest month in Beijing, 3.85m2 of solar collector area was required, and 0.2-0.25m3/m3d of biogas can be obtained.

An Index of Vegetation Water Content Invasion by Landsat 5, in Semi-arid Area: The Tarim River Basin

Estimation of vegetation water content is central to the understanding of water cycle processes. The information of vegetation water content presents the healthy condition of the plant. Various methods were used to extract vegetation water content in semiarid area, however, Spectral indices were still widely used. In this paper, a global sensitivity analysis (GSA) using PROSPECT model was used to understand and quantify vegetation water content effects on the signal measured at leaf level. The NIR region was therefore required in combination with SWIR to retrieve equivalent water thickness (EWT). An index EWTsparsecanopy was created to provide an operational method for quantitatively retrieving vegetation water content at satellite scale in a rapid and reliable fashion for sparsely vegetated arid area based in tarim river basin. Compared with EWTcanopy,the former one had a better relationship to normalized difference infrared index(NDII), With the R2 =0.553. Finally, the regression equation(Y=0.05552 +0.53512*NDII) was used to estimate EWT sparsecanopy from the Landsat TM imagery.