Individual tree traits shape insect and disease damage on oak in a climate‐matching tree diversity experiment

Abstract

Diversifying planted forests by increasing genetic and species diversity is often promoted as a method to improve forest resilience to climate change and reduce pest and pathogen damage. In this study, we used a young tree diversity experiment replicated at two sites in the UK to study the impacts of tree diversity and tree provenance (geographic origin) on the oak ( Quercus robur ) insect herbivore community and a specialist biotrophic pathogen, oak powdery mildew. Local UK, French, and Italian provenances were planted in monocultures, provenance mixtures, and species mixes, allowing us to test whether: (a) local and nonlocal provenances differ in their insect herbivore and pathogen communities, and (b) admixing trees leads to associational effects on insect herbivore and pathogen damage. Tree diversity had variable impacts on foliar organisms across sites and years, suggesting that diversity effects can be highly dependent on environmental context. Provenance identity impacted upon both herbivores and powdery mildew, but we did not find consistent support for the local adaptation hypothesis for any group of organisms studied. Independent of provenance, we found tree vigor traits (shoot length, tree height) and tree apparency (the height of focal trees relative to their surroundings) were consistent positive predictors of powdery mildew and insect herbivory. Synthesis . Our results have implications for understanding the complex interplay between tree identity and diversity in determining pest damage, and show that tree traits, partially influenced by tree genotype, can be important drivers of tree pest and pathogen loads.

Associational resistance to both insect and pathogen damage in mixed forests is modulated by tree neighbour identity and drought

“…Contrary to our hypothesis and previous studies, we did not find evidence for a positive association between insect defoliation on primary growth and oak powdery mildew infection on lammas shoot growth (Field et al, 2019;Marçais & Desprez-Loustau, 2014). Leaf chewer damage was the main contributor to leaf defoliation ( Figure S7) but was not a significant predictor of oak powdery mildew infection (Table 1).…”

“…We predicted that both tree height and shoot length would be positive predictors of insect herbivory and oak powdery mildew, as has been seen in previous studies (Castagneyrol et al, 2013;Field et al, 2019;Gripenberg, Morriën, Cudmore, Salminen, & Roslin, 2007). We found partial support for this hypothesis, as at both the individual shoot and tree level, leaf mines were more abundant on longer shoots, and individual shoot length positively predicted mildew infection.…”

Plant provenance affects pollinator network: Implications for ecological restoration

“…However, plants are the basis of most terrestrial ecosystems and there are myriads of other organisms that depend on them. Especially herbivores and pathogens differentiate among plant genotypes and some provenances support more herbivores than others (Crémieux et al, 2008;Field et al, 2019;Macel et al, 2017;Pearse et al, 2015;Sinclair et al, 2015). Moreover, there can be complex interaction patterns across trophic levels, so that herbivores are adapted to their local plant provenances (Garrido et al, 2012;Kalske et al, 2012;Runquist et al, 2020).…”

Influence of the Urban Environment on the English Oak (Quercus Robur L.) Growth and Development

“…Morphological indicators are a reflection of all processes occurring in the plant, its balance of energy production and consumption, can developing morphological adaptations (Duarte et al 2020, Khan et al 2020; their analysis is available -on the basis of a modern system of computerized phenodata processing, it is much easier to conduct monitoring studies. In addition, signs of viability (shoot length, tree height) and habit are predictors of plant damage by pathogens of various nature (Field et al 2019).…”