The effect of willow diversity on insect herbivory and predation

Abstract

The relationship between plant diversity and ecosystems functions such as regulation of insect herbivory is complex and context‐dependent. The empirical data necessary to account for these interactions are scarce. Our objective is to test the top‐down effects of predation and bottom‐up effects of plant traits to understand what drives patterns of herbivory in managed systems. We established single‐ and multiple‐variety willow field plots with up to four varieties, to study herbivory and predation, and greenhouse experiments to investigate the effects on insect preference and performance. Herbivore damage in the field was higher in single‐ as opposed to multiple‐variety plots for the two most prevalent insect types in one of the 3 years. Predation was higher in multiple‐variety plots than in pure plots during 2016 but the opposite occurred in 2018. Predation on leaf beetle eggs was higher in multiple‐variety plots, but the result was related to specific variety mixtures rather than increased numbers of varieties. Leaf beetle feeding choice and egg‐laying were influenced to some extent by plant diversity. Our results give insights into the links between plant diversity, composition and levels of herbivore damage. They also spark questions about how temporal aspects influence these links.

Enhancing Tree Performance Through Species Mixing: Review of a Quarter-Century of TreeDivNet Experiments Reveals Research Gaps and Practical Insights

“…Several studies used model caterpillars made from plasticine to measure predation rates of arthropods and/or birds [e.g. [94][95][96], but also counts of spider webs [97], and assessment of mycophagy [98] were used to assess predation. In addition, survival of specific leaf herbivores was classified here [99,100].…”

Attraction of Bees to Native and Introduced Willows (Salix spp.)

“…Throughout several countries, multiple studies have shown that SRC plantations provide habitats for a wide array of animals and fungi and also support higher arthropod species richness and density when planted on established agricultural land [16][17][18][19]. Incorporating different willow taxa into bioenergy plantations has previously been suggested to result in more resilient plantings and reduction of herbivorous predation that ensure plant survival and, in turn, protect pollinator communities [20,21].…”

“…There is an established connection between male willows and the attraction of a high number of bees [27]. Males, which provide both pollen and nectar, support insect diversity more readily and consistently compared to their female counterparts, which provide only nectar [21]. Male willows have been shown to support approximately 39% greater abundance, 20% more richness, and 9% greater diversity of bee visitors than female willows [12].…”