Bottom–up and top–down drivers influence urbanization effects on insect herbivory in oaks
Year: 2025
Type: article
Abstract: Urban forests provide essential ecosystem services, including pest control, biodiversity conservation, and human health benefits. Herbivory is a widespread biotic interaction that shapes ecosystem functions, such as primary productivity and soil fertility, which underpin these services. Urbanization can disrupt plant–herbivore interactions by altering plant traits, such as nutrient content or phenolic compounds (bottom–up factors), or by changing the abundance of herbivore natural enemies (top–down control), potentially threatening pest regulation and the ecosystem services provided by urban forests. Disentangling these drivers of herbivory is crucial for designing and managing urban forests to enhance resilience. To address this, we examined insect leaf herbivory on Quercus robur trees in urban and rural forest stands across 13 European cities (n = 104 trees). To assess top–down effects on herbivory, we excluded vertebrate (e.g. birds, bats), invertebrate (e.g. ants), or both groups of predators from branches on each tree using different exclosure types. We then measured insect damage on both control and predator‐excluded branches. To evaluate bottom–up drivers, we measured leaf traits, specifically nutrients and phenolic compounds, and tested for correlations with leaf damage. Additionally, we recorded temperature within stands, an abiotic factor that may modulate both top–down and bottom–up forcing on herbivory. Herbivory was 24% lower on urban trees compared to rural trees. In turn, excluding vertebrate (but not invertebrate) predators increased herbivory, on average, by 40%, but predator effects were stronger in urban stands. Urban trees also had higher leaf quality, with higher nutrient and lower phenolic concentrations; however, these traits did not correlate with herbivory. Temperature was positively associated with urbanization and correlated positively with predation, but did not correlate with herbivory and did not mediate the bottom–up or top–down effects of urbanization. Overall, we find that urbanization affects herbivory through both bottom–up and top–down processes, independent of temperature‐related local conditions. Despite stronger predator effects and higher leaf quality, urban trees experienced lower herbivory, suggesting that unmeasured factors, such as changes in herbivore behaviour or community structure, may play an important role. Further studies are needed to deepen our understanding and inform urban forest management.
Source: Oikos
DOI: 10.1002/oik.11751
Authors: Gabriela Quiroga, Carla Vázquez‐González, Víctor M. Rodríguez, Beatriz Lago‐Núñez, Astrid Van den Bossche, Pieter De Frenne, Martin M. Gossner, Johan A. Stenberg, Kristoffer Hylander, Ayco J. M. Tack, Mona Chor Bjørn, Katerina Sam, Jovan Dobrosavljević, Slobodan Milanović, Olivier Bonnard, Bastien Castagneyrol, Felisa Covelo, Luis Abdala‐Roberts, Xoaquín Moreira
Institutions: Consejo Superior de Investigaciones Científicas, Misión Biológica de Galicia, Ghent University, Swiss Federal Institute for Forest, Snow and Landscape Research, ETH Zurich, Institute of Terrestrial Ecosystems, Swedish University of Agricultural Sciences, Swedish University of Agricultural Sciences, Alnarp, Stockholm University, University of Copenhagen, Czech Academy of Sciences, University of South Bohemia in České Budějovice, Institute of Entomology, Czech Academy of Sciences, Biology Centre, University of Belgrade, Mendel University in Brno, Université de Bordeaux, Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement, UMR BIOdiversity, GEnes & Communities, Universidad Pablo de Olavide, Universidad Nacional Autónoma de México
Language: English
Subfield: Insect Science
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,640
Awards: G113891353, G1166395665, G1300322159, G1302679915, G2158536057, G2427304157, Ecological meltdown in the absence of birds and spiders?, G320354664, G470202589, G477656039, G5725584387, Large solitary trees in the face of climate change: contributions to biodiversity and ecosystem functions, G8073255712, G8247344930, G8365838752, G8920660035, G996282059
OpenAlex ID: W4415947710