Reply on RC2

Abstract

Global sustainable agricultural systems are under threat, due to projected increases of co-occurring drought and salinity with climate change. Combined effects of drought and salinity on agricultural crops have traditionally been evaluated in small-scale experimental studies. As such the need exists for large scale studies that increase our understanding and assessment of the combined impacts in agricultural practice in real life scenarios. This study aims to provide a new approach to estimate and compare the impacts of drought, salinity and their combination on crop traits at large spatial (138.74 km2) and temporal extents in the Netherlands using remote sensing observations. Specifically, for both maize and potato, we calculated five functional traits from Sentinel-2 observations, namely: leaf area index (LAI), the fraction of absorbed photosynthetically active radiation (FAPAR), the fraction of vegetation cover (FVC), leaf chlorophyll content (Cab) and leaf water content (Cw). Individual and combined effects of the stresses on the seasonal dynamics in crop traits were determined using both one-way and two-way ANOVAs. We found that both stresses (individual and co-occurring) affected the functional traits of both crops significantly (with R2 ranging from 0.326 to 0.796), though with stronger sensitivities to drought than to salinity. While we found exacerbating effects within co-occurrent stresses, the impact-level depended strongly on the moment in the growing season. For both crops, LAI, FAPAR and FVC dropped the most under severe drought stress conditions. The patterns for Cab and Cw were more inhibited by co-occurring drought and salinity. Consequently, our study constitutes a way towards evaluating drought and salinity impacts in agriculture with the possibility of potential large-scale application for a sustainable food security.