Hyperspectral Characteristics Of Typical Plants In Sphagnum Wetlands

The spectral characteristics of the surface features are the physical basis for the application of remote sensing technology and also the basis for quantitative analysis of remote sensing.At the same time,the study of spectral spectrum of surface features is one of the important content of remote sensing research.The characteristics of surface spectral information reflect the existence,change,and difference of the surface feature itself.With the developing of hyper-spectral remote sensing technology,it is likely to extract more accurate feature information from tiny spectral differences.Wetlands are one kind of unique,multi-functional and high-value ecosystems that play an important role in carbon storage and greenhouse gas production.As a special type of wetland,Chinese Sphagnum wetlands are mainly distributed in Daxing'anling,Xiaoxing'anling,Changbai Mountain,and other areas,with sporadic distributions in subtropical mountains with high altitudes.Remote investigation of Chinese Sphagnum wetland have not been reported and the resources of Sphagnum wetland are unclear till now due to short of spectral characteristics of the Sphagnum wetlands.The spectral information of Sphagnum wetland species from Tianbaoyan National Nature Reserve in Fujian province and Hani National Nature Reserve in Jilin province was collected and analyzed.The spectral characteristics of Sphagnum and other typical surrounding plants were studied by field and laboratory measurement.The main results as the follows,1.Derivative reflectance method can highlight slope of the spectral curve,thus capture the subtle changes in the spectral curve,such as the “green peak” and “red edge”.It is also possible to further distinguish the spectral characteristics of the Sphagnum from surrounding vascular plants,Phyllostachys heteroclada and Isachne.2.Based on cotinuum removal method,the spectral reflectance characteristics,such as“green peak”,“red valley”,“red edge position”,“absorption depth” and “absorption area” of the four absorption valley in visible band and near-infrared band,and other spectral characteristics can be used to distinguish different Sphagnum.By performing the cotinuum removal method,the "absorption valley" of ten bryophytes can be magnified,thus facilitating the differentiation of different bryophytes.3.Through the principal component analysis(PCA)method,the six peat mosses with similar spectral reflectance curves can be distinguished after spectral reflectance transformation.The results showed that the spectral distribution of Sphagnum capillifolium was more dispersible and could be distinguished from other species after derivative transformation.In two-dimensional space,the distributions of Sphagnum multifibrosum and S.palustre ssp.psedocymbifolium were concentrated.The distributions of S.fuscum,S.magellanicum,and S.palustre were concentrated,while S.fuscum and S.magellanicum were hard to distinguish from each other due to many overlapping portions.4.The spectral characteristics of S.junghuhnianum under different water levels were studied in laboratory and the results show that the spectral curves are very different under different water conditions.With the decreasing of water level,the reflectance of visible band and near infrared band increased,but the depth of the water absorption valley in the near-infrared band deepened with the increasing of water level.With the chlorophyll content decreasing,the red edge position showed a tendency moving to short wave band in all the samples with water level of 1cm,2cm and 5cm,after 20-days experiment.5.After 24 hours,48 hours and 48 hours of drying,the reflectance characteristics of S.palustre ssp.psedocymbifolium was obviously different from those without water stress,mainly being reflected in the green peak,red peak,reflectance of near-infrared band,and water absorption valley at 960 and 1200 nm.6.The water depth of the Sphagnum will affect the water content,thus have a significant effect on it's spectral characteristics.The spectral reflectance characteristics of three Sphagnum showed that the reflectance of low-hummock samples was low,while high in high-hummock samples.The most obvious differences were found in S.palustre.7.The leaf structures of Sphagnum will have a significant effect on it's spectral characteristics.