Compendium Vol. 4 No. 1: Worthy miscellany article summary

Biodiversity increases multitrophic energy use efficiency, flow and storage in grasslands, Buzhdygan 2020

While several studies have shown that biodiversity within a trophic level (among plants, for example) increases ecosystem function (such as productivity), this study examines the effects of increased plant diversity on multi-trophic networks (encompassing plants, soil microorganisms, and above- and belowground invertebrates). The authors compared monoculture plots (with one plant species) to plots containing 60 plant species, and found that:

higher plant diversity leads to more energy stored, greater energy flow and higher community-energy-use efficiency across the entire trophic network. These effects of biodiversity on energy dynamics were not restricted to only plants but were also expressed by other trophic groups and, to a similar degree, in aboveground and belowground parts of the ecosystem, even though plants are by far the dominating group in the system [Buzhdygan 2020: 1].

“More energy stored” means there is more standing biomass in the system, including plants, plant litter, microorganisms, insects and other invertebrates – in short, more life.

Compared to monoculture plots, high-diversity plots also had 50% greater energy flow, which implies “that the overall amount of resources consumed and recycled by the community increased with greater plant diversity” [Buzhdygan 2020: 2].

A community with “higher energy-use efficiency” has lower “maintenance costs,” referring to the amount of energy expended (through respiration) “to support the energetic demands of the living biomass stored in the system” [Buzhdygan 2020: 2]. In other words, organisms in an ecological community with high energy-use efficiency collectively work less hard to sustain themselves compared to, collectively, the organisms in a community with low energy-use efficiency. Biodiversity increases energy-use efficiency by increasing the quantity and variety of resources available to consumers.

Plant communities with a high plant diversity are typically more productive than low-diversity communities and, therefore, provide a larger quantity and variety of resources to consumers. This increase in resource availability can reduce competition and increase energy flow to consumers. A larger variety of resources can also attract a higher number of specialized species, supporting trophic complementarity across the network and resulting in a reduction of community maintenance costs [Buzhdygan 2020: 4].

In this way, higher energy-use efficiency boosts ecosystem function.

Higher energy use efficiency at high plant species richness may be an additional mechanism that contributes to the resilience of ecosystems because communities with low maintenance costs have a higher potential to compensate for energy loss during disturbance. … Moreover, lower community maintenance costs may imply a reduced ‘leakiness’ of ecosystems at high biodiversity. Indeed, evidence is mounting that high-biodiversity ecosystems lose less soil nitrogen, store more carbon in the soil and have more efficient soil microbial communities [Buzhdygan 2020: 7].

Inversely,

the reduced community-energy-use efficiency and standing stock biomass in species-poor ecosystems indicates that more carbon is released into the atmosphere; this implies potential feedback effects of the ongoing global biodiversity loss on carbon sequestration and climate change [Buzhdygan 2020: 8].