The relationship between phytomass, NDVI and vegetation communities on Svalbard

Several studies have shown a close relationship between vegetation fertility and different vegetation indices extracted from satellite data. The vegetation fertility in Arctic is at overall scales highly related to temperature. At lower scales surface material, snow cover, hydrology and anthropogenic effects (geese, reindeer) are determinant in constituting the different vegetation communities. The extent and occurrence of different vegetation communities are expressed in vegetation maps. On Svalbard a vegetation map covering the entire archipelago has recently been developed. The map is differentiated into 18 map units showing large areas of nonand sparsely vegetated ground. The most favorable vegetation is seen as productive marshes and moss tundra communities in the lowland. Various mathematical combinations of spectral channels in satellite images have been applied as sensitive indicators of the presence and condition of green vegetation. Today the normalized difference vegetation index (NDVI) is mostly used to display this information. NDVI is an indicator of the density of chlorophyll in leaf tissue calculated from the red and near infrared bands: NDVI = (NIR − RED)/(NIR + RED). NDVI gives values between −1 and +1 where vegetated areas in general yield high positive values, while non-vegetated ground is found on the negative side. The overall aim of the present study was to test the correlation between NDVI and field-recorded phytomass on Svalbard, Arctic Norway. During the field study the clip-harvest method was conducted on 104 plot sites in the areas of Adventdalen and at Kapp Linné. Every sites recorded was geo-located using GPS. In the image processing part, the available Landsat 7/ETM+ image from 17th of August 2000, was converted into an NDVI-image. From this image NDVI data at the plot sites were recorded. The NDVI data were recorded inside a circle of 100 m around the measurement center. The correspondence between the point-recorded phytomass and correspondent NDVI data show a correlation of R2 = 0.68. Comparable comparison of NDVI extracted from vegetation communities and recorded phytomass show a correlation 2 of R = 0.74. The recorded correlation of community based NDVI and the plant phytomass were used to estimate the total plant phytomass for the entire Nordenskjöld peninsula. The overall phytomass for the entire Nordenskjöld peninsula (3972 km2) is estimated to 604.4 ton × 103 giving an average amount of 152 ton/km2 or 152 g/m2. Correspondent values for lowland and upland areas are 239 ton/km2 (239 g/m2) and 94 ton/km2 (94 g/m2), respectively. Svalbard Miljøfond has funded the project with some support oject from the NCoE/Tundra pr