\"Here we report results of a field experiment in which thenumber of plant species was experimentally controlled (Fig. 1legend). Our 147 plots, located on nitrogen-limited soil24, wereplanted with either 1, 2, 4, 6, 8, 12, or 24 species. The speciesassigned to each plot were chosen by a separate random draw of theappropriate number of species from a pool of 24 North Americanprairie species. The impacts of diversity on plant productivity,nutrient capture and nutrient leaching were observed during thesecond year of growth. We also sampled a native grassland todetermine the relationships between these variables in anundisturbed mature ecosystem. Treatments created an experimentalbiodiversity gradient. THE functioning and sustainability ofecosystems 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 hasreceived much attention 1,.3 6,,7 10- 14, but Darwin's proposal615that more diverse plant communities are more productive, and therelated conjectures,4.s1 6.17 that they have lower nutrient lossesand more sustainable soils, are less well studied 4-6,s,t, 7 l8_Here we use a well-replicated field experi­ ment, in which speciesdiversity was directly controlled, to show that ecosystemproductivity in 147 grassland plots increased significantly withplant biodiversity. Moreover, the main limiting nutrient, soilmineral nitrogen, was utilized more completely when there was agreater diversity of species, leading to lower leaching loss ofnitrogen from these ecosystems. Similarly, in nearby nativegrassland, plant productivity and soil nitrogen utilizationincreased with increasing plant species richness. This supports thediversity-productivity and diversity-sustainability hypotheses. Ourresults demonstrate that the loss of species threatens ecosystemfunctioning and sustainability. The diversity-productivityhypothesis is based on the assump­ tion that interspecificdifferences in the use of resources by plants allow more diversespecies richness (e8 ' ; Fig. la) were all significantly correlatedwith 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 forall). Two measures of peak standing crop (our estimate of plantproductivity) were positively correlated with the species-richnesstreatment (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 plotspecies 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 plantdiversity led to greater productivity during the second year ofecosystem establishment.\"

Can someone draw and explain the experimental design, thankyou!