Fine-scale vertical position as an indicator of vegetation in alkali grasslands – Case study based on remotely sensed data

• Small-scale elevation gradients affect salt and water balance in alkali landscapes.
• Elevation–vegetation correlations have not been studied in inland alkali landscapes.
• We linked elevation data with vegetation patterns using remote sensing techniques.
• Main vegetation categories can be separated by their small-scale vertical positions.
• Remote sensing based vegetation mapping is an ideal tool in such complex landscapes.

Vertical position is an important driver of vegetation zonation at multiple scales, via determining abiotic environmental parameters, such as climate, soil properties and water balance. In inland alkali landscapes, elevation is a key factor for understanding patterns of salt accumulation and water table which is therefore considered a good indicator of alkali vegetation types. Remote sensing techniques offer viable solutions for linking elevation data to vegetation patterns by providing an elevation model of extended areas. Our goal was to test the relationships between fine-scale differences in vertical position and vegetation patterns in inland alkali landscapes by vegetation data collected in the field and elevation data generated using airborne laser scanning (ALS). We studied whether vertical position influences vegetation patterns at the level of main vegetation groups (based on alliances) or even at the level of associations. Our study sites were situated in a lowland alkali landscape in Hortobágy National Park (East-Hungary). We grouped the associations into four main vegetation groups: loess grasslands, alkali steppes, open alkali swards and alkali meadows. Even though we detected a very limited range (121 cm) in the vertical position of the main vegetation groups, they were well separated by their vertical positions. At the level of associations, a more detailed elevation-based distinction was also possible in many cases. The revealed elevation–vegetation correlations show that high-resolution mapping based on ALS remote sensing techniques is an ideal solution in complex lowland areas, such as alkali landscapes. Our findings suggest that in other types of lowland landscapes, characterised by elevation differences, the applied method might hold a great potential as a supporting tool for vegetation mapping.