Monitoring Effects of Drought on Nitrogen and Phosphorus in Temperate Oak Forests Using Machine Learning Techniques
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Remote Sensing Division, Space Technologies Center, Łukasiewicz Research Network - Institute of Aviation, Al. Krakowska 110/114, Warsaw, 02-256, Poland
Faculty of Civil Engineering and Geodesy, Military University of Technology in Warsaw, ul. gen. Sylwestra Kaliskiego 2, 00 -908 Warszawa 46, Poland
Katarzyna Anna Kubiak   

Zakład Teledetekcji, Sieć Badawcza Łukasiewicz - Instytut Lotnictwa, Aleja Krakowska 110/114, 02-256, Warszawa, Poland
Submission date: 2020-10-28
Final revision date: 2021-07-27
Acceptance date: 2021-08-16
Online publication date: 2021-12-31
Publication date: 2022-02-16
Pol. J. Environ. Stud. 2022;31(2):1137–1151
Pedunculate oak (Quercus robur. L) is a European tree species highly sensitive to drought. If declining symptoms appear they are often detectable at the crown (such as dieback) enabling monitoring using aerial images and remote sensing methods. Here, we analyzed the impact of short and long-term drought on oaks located in western Poland, between the years of 2014 and 2017. We used both leaf nitrogen (N) and leaf phosphorus (P) concentrations measured in the laboratory, aerial images collected in the range of 460-880 nm and machine learning techniques to estimate nutrient concentrations on the > 4000 oaks growing on stagnic luvisols in the study area. We determined a negative impact on N and P concentrations during both types of drought stress (-23% and -19% for N concentration in leaves; -27% and -10% for P concentration in leaves). Decreased water availability had inconsiderable impact on N:P values (3% increase of N:P ratio during short and 7% decrease of N:P ratio during long-term drought stress). We found that the long-term drought impact was spatially diverse, possibly depending on the presence of drainage ditches and competing species.