Biodiversity and ecosystem functioning in naturally assembled communities

Abstract

Approximately 25 years ago, ecologists became increasingly interested in the question of whether ongoing biodiversity loss matters for the functioning of ecosystems. As such, a new ecological subfield on Biodiversity and Ecosystem Functioning (BEF) was born. This subfield was initially dominated by theoretical studies and by experiments in which biodiversity was manipulated, and responses of ecosystem functions such as biomass production, decomposition rates, carbon sequestration, trophic interactions and pollination were assessed. More recently, an increasing number of studies have investigated BEF relationships in non-manipulated ecosystems, but reviews synthesizing our knowledge on the importance of real-world biodiversity are still largely missing.I performed a systematic review in order to assess how biodiversity drives ecosystem functioning in both terrestrial and aquatic, naturally assembled communities, and on how important biodiversity is compared to other factors, including other aspects of community composition and abiotic conditions. The outcomes of 258 published studies, which reported 726 BEF relationships, revealed that in many cases, biodiversity promotes average biomass production and its temporal stability, and pollination success. For decomposition rates and ecosystem multifunctionality, positive effects of biodiversity outnumbered negative effects, but neutral relationships were even more common. Similarly, negative effects of prey biodiversity on pathogen and herbivore damage outnumbered positive effects, but were less common than neutral relationships. Finally, there was no evidence that biodiversity is related to soil carbon storage.Most BEF studies focused on the effects of taxonomic diversity, however, metrics of functional diversity were generally stronger predictors of ecosystem functioning. Furthermore, in most studies, abiotic factors and functional composition (e.g. the presence of a certain functional group) were stronger drivers of ecosystem functioning than biodiversity per se. While experiments suggest that positive biodiversity effects become stronger at larger spatial scales, in naturally assembled communities this idea is too poorly studied to draw general conclusions.In summary, a high biodiversity in naturally assembled communities positively drives various ecosystem functions. At the same time, the strength and direction of these effects vary highly among studies, and factors other than biodiversity can be even more important in driving ecosystem functioning. Thus, to promote those ecosystem functions that underpin human well-being, conservation should not only promote biodiversity per se, but also the abiotic conditions favouring species with suitable trait combinations.

Greater than the sum of the parts: how the species composition in different forest strata influence ecosystem function

“…Each of quadrats represents the neighbourhood scale and each of plots represents the community scale. phosphorus concentration (LPC), wood density and seed mass) for species in the different forest strata (Table S4) following the protocols of Cornelissen et al (2003) and P erez- Harguindeguy et al (2013). These traits are physical characteristics that affect the growth, survival and reproduction of individuals, hence the functioning of communities (Garnier et al 2004;McGill et al 2006).…”

Biodiversity mediates the effects of stressors but not nutrients on litter decomposition

“…These early experiments also focused on species richness as the sole biodiversity index, and manipulated it directly and randomly. However, environmental change will often elicit non-random changes in several facets of biodiversity 9–11 (community composition and population densities 12,13 , functional diversity 14–16 , trophic diversity 17,18 , or intra-specific diversity 19 ). The selective effects of environmental change emerge because different organisms differ in their response to environmental change.…”

“…When environmental change affects these mechanisms, teasing out the relative importance of biodiversity-mediated effects is complicated even more. Given the number of different potential mechanisms, quantifying the extent to which shifts in biodiversity underpin the effect of environmental change on ecosystem functioning under real-world scenarios of global change is a key challenge for ecology 5–8,11,23 . Incorporating the impacts of environmental change drivers into BEF studies and meta-analyses is an important step forward to address such questions 5,6 .…”

Non-production vegetation has a positive effect on ecological processes in agroecosystems

“…There is increasing evidence (e.g. Tilman and Downing 1994, Srivastava and Vellend 2005, Cardinale et al 2006, van der Plas 2019), that a positive relationship exists between biodiversity and ecosystem function , although the exact nature and strength of the relationship is process- and context-dependent (Gamfeldt and Roger 2017, van der Plas 2019). Thus, biodiversity itself is fundamental to sustaining the biotic and abiotic ecosystem processes that underpin sustainable and resilient agroecosystems (‘ functional biodiversity ’, sensu Moonen and Barberi 2008, Martin et al 2019) and the downstream delivery of ecosystem services .…”

“…The majority of the 500 research questions from the 342 reviewed articles (83%; n = 416) were posed using variables that have only been hypothesised to represent ecosystem function, such as biodiversity and soil physicochemical properties. There is only variable and/ or weak evidence for many hypothesised causal relationships between such proxy variables and ecosystem functions, such as the links between biodiversity and soil carbon, decomposition rates, or herbivory (van der Plas 2019) or the links between indicators of soil properties and processes such as nutrient cycling and water quality (Bünemann et al 2018). In other cases, links have been shown to be weak or absent.…”