Comparing water requirements of urban landscape plants in an arid environment: An application of the WUCOLS method in the National Botanical Garden of Iran

Abstract

Water scarcity is a pressing issue in many arid and semi-arid regions worldwide, requiring effective water resource management. To address this challenge in the National Botanical Garden of Iran, we analyzed the water requirements for the irrigation of ten tree species over the entire growth period, spanning from January 2021 to January 2022. We employed the Water Use Classification of Landscape Plants (WUCOLS) method, and used remote and on-site measurements to obtain the required data (i.e., enhanced vegetation index, leaf area index, rainfall, and site and species characteristics) for the analysis. We found that Ficus carica L., Cercis siliquastrum L., and Ulmus glabra Hudson had high landscape evapotranspiration (ETL) values, showing their elevated water requirements. Among all the species studied, F. carica, C. siliquastrum, and U. glabra showed the highest total ETL, reaching 1033, 1031, and 1002 mm respectively, highlighting their overall greater water needs throughout the study period. Further, we computed the annual net water requirement (IRn) for each plant species, taking into account the effective rainfall of 123.5 mm during the growth period of the study garden. We found that F. carica, C. siliquastrum, and U. glabra had the highest IRn among all the species with values of 950, 948, and 919 mm respectively. In contrast, Olea europaea L., and Quercus robur L. had the lowest IRn values of 681, and 711 mm, respectively. Additionally, we assessed the difference between annual irrigation values (AI) and gross water requirement values (IRg). Cercis siliquastrum and F. carica with values of −519 mm and − 511 mm had the largest negative differences, indicating that these species received the least irrigation water in comparison with their gross water requirements among all the species. In contrast, Cotinus coggygria, and O. europaea, with values of 182 mm and 125 mm had the largest positive differences, suggesting that these species received the most irrigation water in comparison with their gross water requirements among all the species. Our findings hold significance for the management of urban green spaces, including botanical gardens, parks, and street trees, contributing to the well-being of urban residents and visitors.