Question

"Here we report results of a field experiment in which the number of plant species was experimentally controlled (Fig. 1 legend). Our 147 plots, located on nitrogen-limited soil24, were planted with either 1, 2, 4, 6, 8, 12, or 24 species. The species assigned to each plot were chosen by a separate random draw of the appropriate number of species from a pool of 24 North American prairie species. The impacts of diversity on plant productivity, nutrient capture and nutrient leaching were observed during the second year of growth. We also sampled a native grassland to determine the relationships between these variables in an undisturbed mature ecosystem. Treatments created an experimental biodiversity gradient. THE functioning and sustainability of ecosystems may depend on Plant species richness, Shannon diversity (H1 and effective their biological diversity1-a. Elton's' hypothesis that more diverse ecosystems are more stable has received much attention 1,.3 6,,7 10- 14, but Darwin's proposal615 that more diverse plant communities are more productive, and the related conjectures,4.s1 6.17 that they have lower nutrient losses and more sustainable soils, are less well studied 4-6,s,t, 7 l8_ Here we use a well-replicated field experi­ ment, in which species diversity was directly controlled, to show that ecosystem productivity in 147 grassland plots increased significantly with plant biodiversity. Moreover, the main limiting nutrient, soil mineral nitrogen, was utilized more completely when there was a greater diversity of species, leading to lower leaching loss of nitrogen from these ecosystems. Similarly, in nearby native grassland, plant productivity and soil nitrogen utilization increased with increasing plant species richness. This supports the diversity-productivity and diversity-sustainability hypotheses. Our results demonstrate that the loss of species threatens ecosystem functioning and sustainability. The diversity-productivity hypothesis is based on the assump­ tion that interspecific differences in the use of resources by plants allow more diverse species richness (e8 ' ; Fig. la) were all significantly correlated with the number of species seeded into the plots (Pearson's r = 0.81, r = 0.74, r = 0.75, respectively; n = 147, P < 0.001 for all). Two measures of peak standing crop (our estimate of plant productivity) were positively correlated with the species-richness treatment (total plantcover:r 0.39,n = 147,P < 0.001, Fig. lb; biomass estimated by light penetration: r = 0.27, n = 147, P < 0.001). Both estimates were similarly dependent on observed plot species richness (rcover = 0.55, rbiomass = 0.42, n = 147, P < 0.001 for both) and effective species richness (rcover = 0.29, rbiomass = 0.29,n = 147,P < 0.001 for both). Thus, greater plant diversity led to greater productivity during the second year of ecosystem establishment."

Can someone draw and explain the experimental design, thank you!

Answer 1

Okay, so this experiment wants to prove one thing: Does species richness has a positive impact on productivity and sustainability?

Because there is a model that states that a high number of different species has a negative effect on productivity and sustainability, while there is another model stating just the contrary.

For this, the research team had to test the plant productivity, nutrient capture and nutrient leaching in different plant diversity conditions, that's why they made 147 plots. Such plots correspond to different treatments, as each plot had a different number of species and kind of species growing together in them. Then the parameters were measured for each one of the plots, results showed that a larger number of species (high richness) has a positive effect on productivity and sustainability.

Fig. We can see an scheme of the plots. Each treatment has a different number of species. Once stablished, the plants started to grow and cohabitate the same space, taking nutrients, leaching them, being productive at certain level. Then the parameters were measured and compared between plots. That's how we obtained results that led to a discussion.

The a disucussion took place based on these results, leading to topics surrounding diversity loss and species extinction. The diversity loss leads to poor plant productivity, poor nutrient capture and nutrient leaching in the soil. Social, economical and management measures may be taken due to the results and discussion from this survey.