The Relationship Between the Above-Ground Biomass and the Vegetation Cover Indices at Different Salinity Levels

Abstract

Abstract The current study was carried out to find out the relationship between the Above-Ground Biomass and the spectral vegetative indices (Normalized Difference Vegetation Index, Soil Adjusted Vegetation Index, Difference Vegetation Index) (NDVI, SAVI, DVI) for soils with different salinity levels. Al Salamiyat Project was chosen as a study area located at an altitude of 34 m above sea level and within the geographical coordinates (E 44°.09´13.65´´ N 33°.25´ 07.87´´ and E 44°.17´ 46.03´´ N 33°.2l´40.72´´), with a total area of 14265 Dunum. Surface and subsurface soil samples were chosen from the study area and according to the previously defined salinity units, except for the salinity map that was updated based on the soil samples of the current study. After updating the salinity map of this project, 12 Pedons (two Pedon for each salinity unit) were excavated and morphologically described. Then, the soil samples were taken from each horizon to estimate the physical and chemical properties and biomass values for each site. The study showed that the soil salinity Ece in the study Pedon ranged from 1.1 dS/m in the C2 horizon for the twelfth Pedon to 41.6 dS/m in the upper Az horizon of the ninth Pedon. It also showed that there is a high correlation (r = 0.553) between the values of soil salinity and the biomass of plants growing in it, which confirms that the biomass was increasing with the increase in soil salinity. Furthermore, the (NDVI) showed a variation in the study area, ranging from 0.386 to 0.473, while the values of this index ranged from 0.1568 to 0.4093, as it was observed that there is a direct relationship between them (r = 0.643). The values of (SAVI) showed a difference between the studied Pedon sites, the values of this index ranged from 0.0581 to 0.7100, and it was also ranged from 0.1087 to 0.6213 for the same Pedon value. Whereas the values of the (DVI) index ranged between -0.0023 to 0.0942 and from 0.0197 to 0.0874 for the study Pedon, this index showed a highly significant relationship with the above-ground biomass (r = 0.825).