Key Words: Wetland Vegetation, Productive 3-D Structure, Multi Angles, Spectral Reflectance, Vegetation Indices
Abstruct: The canopy spectral reflectance at multi angles and the 3-D structures of vegetation were measured in "Kushiro wetland" and " Akkeshiko - Bekanberushi Wetland" located in the eastern part of Hokkaido; the north island of Japan in the summer of 1998. Our purpose of this research was to clarify the characteristics of spectral reflectance and to develop the algorithm according to the wave bands and the band ratio with multi angles effective to the classification and the estimation biomass used cross - near range R.S.
We clarified the relationship of the spectral reflectance and each 3-D biomass layer structure specific to the wetland vegetation. The bi-band ratio of reflectance and the LAD ( Leaf Area Density) - SLA (Specific Leaf Area) and the productive structure by the stratified clip method was measured. And we specified the canopy layer structure by the observation at not only the nadir angle but also the plural angles from±15°to ±45°range.
The values with remarkable difference could be seen at multi angle rather than nadir, and also infrared rather than red range, especially among the similar vegetation canopies located in the transition moor. While we could not find out any effectively different values for the classification among the fens and the transition moors in G/NIR, R/NIR, and NDVI, though the effectiveness of those could be seen in only bog Muskege and the fen and the transition - moor mixed with shrub. On the other hand, G/R and VI were effective to them classify. The spectral reflectance of the canopies depended on their canopy 3-D structures and their dominant vegetation types. Selecting the specific wave bands and their band ratio observed at multi - plural angle with cross - near range R.S. data was effective for the estimation of the biomass and the classification of wetland vegetation.
1. Introduction
The estimation of CH4 flux at each wetland vegetation in global wide range is in urgent necessity for the study of the influence of the global warming. From the local point of view, it is necessary to grasp the vegetation distributions in wide range to understand the extension of the migration belt and the biodiversity to preserve the wetland vegetation.
So many researchers are trying to classify vegetation in wetlands using satellite or aeroplane .S. in order to make vegetation maps. Recently, the spectral reflectance of vegetation canopy measured at multi angles has a lot of information of canopy structure as well as species types. However the precision of classification of wetland vegetation based on R.S. is not enough for the reason why the wetland vegetation has the complicated layer structure and its specific characteristics especially situated in bog and transition mixed vegetation. Our goal of this research is to develop the algorithms and make it clear the relationship of the characteristics of the spectral reflectance measured at plural angles and the 3 - D layer biomass structure.
2. Study Area
The research was carried out at typical fen, transitional, bog vegetation in Akkeshiko Bekkanberushi wetland, and Akanuma in Kushiro wetland, eastern part in Hokkaido( Fig.1 ). The former is the second largest and the latter is the largest wetland in Japan and they have been registered in the list of wetlands of international importance. Especially, the bog in Akkeshiko Bekkanberushi wetland is known as the academically precious existence with little artificial impact. The concrete investigation site was peat bog in which the Sphagnum moss piled up located in the confluence point of Toraibetsu River and Bekkanberushi River and where precious alpine plant develops ( site A - C ) and the fen besides Taibetsu River ( site D ) ( Fig.2 ). In Kushiro at the bog right bank of Kushiro River ( site E - G ), the fen along the walk street inside the wetland ( site H, I ) and the transitional moor paralleled old railway ( site J ). This research was carried out in June and July, 1998.
The vegetation research and the biomass were measured. Since the layer structure is complicated, the productive structure figure were made with the combination of dominant species and other species. Each 0.5m×0.5m quadrat was set based on the simple random sampling method. We measured occurrence, dominance, sociability, vegetation cover, and height above the ground for herbaceous layer, moss layer, bush layer. Each vegetation photos in the quadrate were taken above two m high from the canopy by using long pole carried with two steel cameras and optical tube sensor on the top. Based on the stratified clip technique, the biomass measurement was carried by cutting down from the top of the plant community in every 10cm interval. The dry mass were measured ( 48 hours at 80 degrees ) after they were diffrenciated in photosynthesis organ ( assimilatory organ ; lamina ) and non-photosynthesis organ ( non- assimilatory organ ; stem, spike, petiole, flower ) on each 10 cm layer and the species. Leaf Area Index {LAI: all leaf area ( cm2) / 0.5m×0.5m quadrat} and Leaf Area Density ( LAD: all leaf area ( cm2) / 0.5m×0.5m quadrat / 10 cm layer ) were also measured. And we examined the relationship between LAD - SLA in each layer to specify the two dimension data of each biomass and leaf area.
