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- Foliar optical traits indicate that sealed planting conditions negatively affect urban tree healthPublication . Yu, Kang; Geel, Maarten Van; Ceulemans, Tobias; Geerts, Willem; Ramos, Miguel Marcos; Sousa, Nadine; Castro, Paula M. L.; Kastendeuch, Pierre; Najjar, Georges; Ameglio, Thierry; Ngao, Jérôme; Saudreau, Marc; Honnay, Olivier; Somers, BenUrban trees play a key role in mitigating environmental problems in cities, but they often face harsh environmental conditions as they generally grow in sealed soils that have small rooting space and low water availability. In this context, rapid monitoring and assessment of tree health status is critical to maintain urban trees and secure the provisioning of urban ecosystem services. Across three European cities we selected 187 Tilia tomentosa trees growing under following planting conditions: (i) sealed, trees planted in small soil pits or strips surrounded by highly sealed surfaces (concrete, pavement or asphalt); and (ii) unsealed, trees planted in roomy soil surfaces (e.g. parks). We measured leaf reflectance and fluorescence and derived a set of optical traits from the measurements. We examined whether these non-destructively measured optical traits differ between planting conditions and whether they correlate with leaf functional traits, e.g. specific leaf area (SLA), leaf water content (LWC) and leaf water per area (LWA). Compared to the unsealed trees, sealed trees showed decreased SLA and LWC while increased LWA. Leaf optical traits differed between the unsealed and sealed trees. Highly sealed soilsaccelerated leaf senescence of the sealed trees compared to the unsealed trees, embodied in the temporal trend of optical traits. Sealed planting conditions negatively affect urban tree health status and phenology. These negative effects can be estimated by leaf optical traits, emonstrating the great potential of optical traits in assessing tree health status. Our findings provide insights into facilitating urban green management using optical traits and remote sensing data.
- Variation in ectomycorrhizal fungal communities associated with Silver linden (Tilia tomentosa) within and across urban areasPublication . Geel, Maarten Van; Yu, Kang; Ceulemans, Tobias; Peeters, Gerrit; Acker, Kasper van; Geerts, Willem; Ramos, Miguel M.; Serafim, Cindy; Kastendeuch, Pierre; Najjar, Georges; Ameglio, Thierry; Ngao, Jérôme; Saudreau, Marc; Waud, Michael; Lievens, Bart; Castro, Paula M.L.; Somers, Ben; Honnay, OlivierTrees in urban areas face harsh environmental conditions. Ectomycorrhizal fungi (EcM) form a symbiosis with many tree species and provide a range of benefits to their host through their extraradical hyphal network. Although our understanding of the environmental drivers and large scale geographical variation of EcM communities in natural ecosystems is growing, our knowledge of EcM communities within and across urban areas is still limited. Here, we characterized EcM communities using Illumina miseq sequencing on 175 root samples of the urban tree Tilia tomentosa from three European cities, namely Leuven (Belgium), Strasbourg (France) and Porto (Portugal). We found strong differences in EcM richness and community composition between cities. Soil acidity, organic matter and moisture content were significantly associated with EcM community composition. In agreement, the explained variability in EcM communities was mostly attributed to general soil characteristics, whereas very little variation was explained by city and heavy metal pollution. Overall, our results suggest that EcM communities in urban areas are significantly associated with soil characteristics, while heavy metal pollution and biogeography had little or no impact. These findings deliver new insights into EcM distribution patterns in urban areas and contribute to specific inoculation strategies to improve urban tree vitality.