Responses of drought-tolerant Tipuana tipu trees to long-term irrigation: A tree-ring study in Lisbon, Portugal
| Authors: | Augusto Akio Lucchezi Miyahara, Ana Paula Ramos, Filipa Maia, Ana Julia Francisco, Milena Godoy-Veiga, Mario Tomazello-Filho, Francisco William da Cruz, Francisco J. Escobedo, Laia Andreu-Hayles, Giulia Nunes de Aguiar Souto, Giuliano Maselli Locosselli |
| Year: | 2026 |
| Type: | Scientific Journal |
| Station: | Pacific Southwest Research Station |
| DOI: | https://doi.org/10.1016/j.ufug.2026.129341 |
| Source: | Urban Forestry and Urban Greening |
Abstract
Tree planting is a key strategy for the adaptation of cities to climate change. However, cities in semi-arid and Mediterranean climates struggle to sustain tree growth, often relying on irrigation systems. Literature suggests that irrigation enhances tree growth and ecosystem service provision at the cost of structural and physiological adjustments that can lead to lower wood density, compromising tree’s mechanical stability and pathogen resistance. Yet, the response of trees to irrigation is species dependent, raising uncertainty about its possible costs and benefits. We investigate how drought-tolerant Tipuana tipu trees – a common species in Lisbon and other cities worldwide – responded to six years of irrigation using a multi-proxy tree-ring approach. We examined even sized and aged trees growing under comparable conditions in the Duque de Saldanha Square, differing only in irrigation regime. The strong positive relationship between growth and oxygen stable isotopes of control trees suggests that growth is associated with high atmosphere demand during the warm and dry season. Starting in 2017, the irrigation alleviated the stomatal conductance limitations in the treatment trees, as evidenced by the significant decrease in stable carbon isotope values and a twofold increase in growth rate compared to control trees. Notably, irrigation did not result in any significant wood density reduction. These findings challenge the assumption of wood density reduction under irrigation and further highlight this drought-tolerant species capacity to increase growth rate and maintain wood density. A trait combination likely to enhance ecosystem services delivery without compromising mechanical stability under long-term irrigation.