Investigating plant response to soil characteristics and slope positions in a small catchment

Methods enabling stakeholders to receive information on plant stress in agricultural settings

in a timely manner can help mitigate a possible decrease in plant productivity. The present work

aims to study the soil–plant interaction using field measurements of plant reflectance, soil water

content, and selected soil physical and chemical parameters. Particular emphasis was placed on

sloping transects. We further compared ground- and Sentinel-2 satellite-based Normalized Vegetation

Index (NDVI) time series data in different land use types. The Photochemical Reflectance Index (PRI)

and NDVI were measured concurrently with calculating the fraction of absorbed photochemically

active radiation (fAPAR) and leaf area index (LAI) values of three vegetation types (a grassland,

three vineyard sites, and a cropland with maize). Each land use site had an upper and a lower

study point of a given slope. The NDVI, fAPAR, and LAI averaged values were the lowest for

the grassland (0.293, 0.197, and 0.51, respectively), which showed the highest signs of water stress.

Maize had the highest NDVI values (0.653) among vegetation types. Slope position affected NDVI,

PRI, and fAPAR values significantly for the grassland and cropland (p < 0.05), while the soil water

content (SWC) was different for all three vineyard sites (p < 0.05). The strongest connections were

observed between soil physical and chemical parameters and NDVI values for the vineyard samples

and the selected soil parameters and PRI for the grassland. Measured and satellite-retrieved NDVI

values of the different land use types were compared, and strong correlations (r = 0.761) between

the methods were found. For the maize, the satellite-based NDVI values were higher, while for the

grassland they were slightly lower compared to the field-based measurements. Our study indicated

that incorporating Sentinel-derived NDVI can greatly improve the value of field monitoring and

provides an opportunity to extend field research in more depth. The present study further highlights

the close relations in the soil–plant–water system, and continuous monitoring can greatly help in

developing site-specific climate change mitigating methods.