Multi-trophic communities re-establish with canopy cover and microclimate in a subtropical forest biodiversity experiment

Felix Fornoff,Alexandra-Maria Klein,Michael Staab,Chao-Dong Zhu

doi:10.1007/s00442-021-04921-y

Abstract

Plant diversity affects multi-trophic communities, but in young regrowth forests, where forest insects are in the process of re-establishment, other biotic and also abiotic factors might be more important. We studied cavity-nesting bees, wasps and their natural enemies along an experimental tree diversity gradient in subtropical South-East China. We compared insect communities of experimental young forests with communities of established natural forests nearby the experiment and tested for direct and indirect effects of tree diversity, tree basal area (a proxy of tree biomass), canopy cover and microclimate on bee and wasp community composition, abundance and species richness. Finally, we tested if the trophic levels of bees, herbivore-hunting wasps, spider-hunting wasps and their natural enemies respond similarly. Forest bee and wasp community composition re-established towards communities of the natural forest with increasing tree biomass and canopy cover. These factors directly and indirectly, via microclimatic conditions, increased the abundance of bees, wasps and their natural enemies. While bee and wasp species richness increased with abundance and both were not related to tree diversity, abundance increased directly with canopy cover, mediated by tree biomass. Abundance of natural enemies increased with host (bee and wasp) abundance irrespective of their trophic position. In conclusion, although maximizing tree diversity is an important goal of reforestation and forest conservation, rapid closure of canopies is also important for re-establishing communities of forest bees, wasps and their natural enemies.

Highlights

Forests harbor 80% of Earth’s biodiversity and provide crucial ecosystem functions, but are in constant decline through deforestation (FAO 2011; Basset et al 2012)
To inform forest management, we studied the relative importance of bottom-up and top-down effects induced by tree species richness, biomass and microclimate for forest community re-establishment, abundance and species richness of multiple trophic levels in an experimental young regrowth forests and in comparison to a nearby established natural forest
In young regrowth forests, cavity-nesting bee and wasp community composition re-established with increasing canopy cover and basal area

Summary

Introduction

Forests harbor 80% of Earth’s biodiversity and provide crucial ecosystem functions, but are in constant decline through deforestation (FAO 2011; Basset et al 2012). Ecosystem multifunctionality and biodiversity are driven by trophic interactions and biodiversity at multiple trophic levels (Soliveres et al 2016; Schuldt et al 2018). To investigate interactions and diversity at different trophic levels, cavitynesting insects are an established study system (Tscharntke et al 1998; Staab et al 2018). These communities consist of Hymenoptera and their natural enemies. They represent multiple trophic levels ranging from herbivores to parasitoids of predators and mediate functions such as pollination, herbivore-control and parasitism (Staab et al 2018)

Methods

Results

Conclusion