What does this research mean for the field?

C. betulus is a more promising riparian tree species for urban landscapes under drought-prone conditions compared to Q. robur. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

The aim is to understand how two riparian tree species respond to drought stress in urban environments.

March 12, 2026Forests2 citationsOpen Access

Leaf Functional Traits and Water-Use Strategies of Two Riparian Tree Species in an Urban Environment

EVErna VaštagUniversity of Novi Sad LKLazar KesićUniversity of Novi Sad CCClaudia CocozzaUniversity of Florence

Key Points

The aim is to understand how two riparian tree species respond to drought stress in urban environments.
Assessed leaf gas exchange and chlorophyll a fluorescence of Quercus robur and Carpinus betulus
Conducted monthly evaluations from June to September in Novi Sad, Serbia
Measured stomatal density and size to compare physiological responses
Q. robur maintained photosynthetic activity and transpiration under drought due to reduced stomatal sensitivity
C. betulus displayed stricter stomatal regulation with lower assimilation rates
Fluorescence indices indicated higher NPQ values in C. betulus, suggesting lower photosynthetic efficiency under stress
C. betulus had higher stomatal density and smaller stomatal size, indicating faster response rates compared to Q. robur

Abstract

Urban roadside environments are characterized by altered microclimate and soil conditions that impose recurrent drought stress on trees, affecting their physiological performance and adaptive capacity. Understanding species-specific physiological and structural responses to drought stress is crucial for selecting tree species that are suitable for urban environments. In the present study, we investigated the species-specific and temporal (monthly) patterns of the in situ leaf physiological status and structural traits of two riparian tree species, Quercus robur L. and Carpinus betulus L., cultivated as urban roadside trees in Novi Sad, Serbia, throughout the growing season (from June to September). This was achieved by assessing leaf gas exchange and rapid light curves of chlorophyll a fluorescence together with leaf structural traits. Under drought stress, Q. robur exhibited sustained photosynthetic activity and transpiration rates due to reduced stomatal sensitivity, indicative of a more anisohydric behavior with respect to its water relations strategy. In contrast, C. betulus exhibited tighter stomatal regulation and showed lower assimilation rates accompanied by reduced cooling capacity, indicating stricter, more conservative water-balance management indicative of isohydric species. Fluorescence indices revealed contrasting behavior: C. betulus showed enhanced NPQ values accompanied by a decline in photosynthetic efficiency, while Q. robur exhibited lower NPQ, suggesting better maintenance of photosynthetic performance and electron transport in PSII under the observed drought stress. These patterns were further supported by higher stomatal density combined with smaller stomatal size, indicating faster stomatal response rates in C. betulus compared to Q. robur. Overall, these results suggest that C. betulus is a more promising riparian tree species for urban landscapes, particularly under drought-prone conditions and predicted climate changes, in comparison to Q. robur.

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