Many recent ecological experiments ask whether more species-rich plots of grassland produce more aboveground biomass on average than do species-poor plots. Alternatively, one might hypothesize that biomass production depends mainly on the presence or absence of N-fixing legumes, which enrich the soil with nitrogen (a key limiting nutrient) and so promote plant growth. To test these possibilities, you plan to sow plots with all possible combinations of 1-8 grassland plant species chosen from a "pool" of 8 species. The pool includes 1 legume species, and 7 non-legumes. You plan to have 2 replicate plots of every species growing on its own (single-species plots), 2 replicate plots of every possible combination of 2 species growing together (two-species plots), and 2 replicate plots of all 8 species growing together. Your planned statistical analysis will relate the total aboveground biomass in each plot (dependent variable) to the predictor variables species richness (numerical variable; 1, 2, or 8 species), legume presence/absence (categorical variable), and their interaction. 2 (2 marks). Is this a balanced design for purposes of your planned statistical analysis? Explain why or why not in 3 sentences, max