The Relationship Between Plant Diversity and Productivity in Natural and in Managed Grasslands

Abstract

Assaf et al.: The relationship between plant diversity and productivity in natural and in managed grasslands - Abstract. Despite the fact that several experiments have been conducted to explore the biodiversityproductivity relationship in synthesized and natural plant communities, the results obtained were contradictory and no clear consensus has been reached. Recent experiments that surveyed mature natural plant communities have investigated this relationship across environmental gradients, where biotic and/or abiotic factors are correlated with the observed diversity and productivity levels. We studied the effect of plant diversity on ecosystem productivity in agriculturally managed (managed at a low intensity with moderate level of disturbance) and natural (no history of management) grasslands at a within-site scale in order to minimize the confounding effect of environmental factors. We tested the effects of two diversity measures (species richness and species evenness) on productivity within-and across-sites scale. Our results indicated that this relationship was different between the natural and the managed grasslands and varied according to the diversity measure. Species richness only poorly explained the variation in productivity for the managed grasslands, while the variations in system productivity were better explained by species evenness. Interestingly, our results from the natural low productive, species poor grassland are in agreement with the results obtained from the recent experiments that artificially manipulated diversity levels and found an asymptotic increase in productivity along with increasing species richness. Our results provide additional evidence of the complex behavior that measures of species diversity that combine several aspects of diversity such as species evenness, species identity as well as the interactions among the species may be better determinants of the response of the ecosystem to biodiversity.

Overyielding in mixed forests decreases with site productivity

“…b). This result is consistent with findings in grasslands where species identity and species evenness have been put forward to explain the relationship between productivity and diversity (Wilsey & Potvin ; Assaf, Beyschlag & Isselstein ). On average, the three mixed stands in highlands, European beech–Norway spruce, European beech–silver fir and to a lesser extent, silver fir–Norway spruce mixtures overyielded (Fig.…”

Effects of species evenness can be derived from species richness – ecosystem functioning relationships

“…Species evenness describes how uniform the population sizes of the different species in a community are and, together with species richness, determines a community's species diversity (Smith and Wilson 1996). The first experiments on the influence of species evenness on ecosystem processes are relatively recent (Wilsey and Potvin 2000, Wilsey and Polley 2002, Mattingly et al 2007) and the debate on the effects of evenness on ecosystem functioning still continues today (Assaf et al 2011, Schmitz et al 2013, Rohr et al 2016), due to differences in methodology and practical limitations of testing species evenness effects at high richness levels in experiments (Naeem 2009). Indeed, because the number of different communities that are required to manipulate species evenness becomes excessive once there are more than just a few species, studies on synthesized communities have only rarely expanded to more than four plant species (Wilsey and Potvin 2000, Kirwan et al 2007, Mattingly et al 2007, Wittebolle et al 2009, Schmitz et al 2013.…”

Effects of Climate Change on Grassland Biodiversity and Productivity: The Need for a Diversity of Models

“…In grassland experiments with low ground cover, biodiversity still conferred stability but productivity depended more on ground cover than on species richness [65]. Also, experiments in Germany by Assaf et al [66] suggest that biodiversity has a stronger effect on productivity in unmanaged than in managed grasslands. De Boeck et al [67] found by experiment that warming may increase the detrimental effect of species loss on grassland productivity in temperate climates.…”