OOS 46-9
Can ecological knowledge be used to design cover crop mixtures that provide multiple ecosystem services?
A central tenet of biodiversity-ecosystem function (BEF) theory is that greater biodiversity increases function. Research conducted in natural ecosystems shows that both plant phylogenetic and functional diversity are useful in predicting ecosystem functions such as net primary productivity. We extend this concept to examine the role of plant phylogenetic and functional diversity in the provision of ecosystem goods and services in agroecosystems. In particular, we focus on the potential for strategic use of biodiversity to enhance cover crop functions. The expectation is that phylogenetic distance and functional diversity are positively correlated and, while this is often true, there are many exceptions, particularly in agriculture where crop breeding has manipulated intra-specific variation to create distinct crop ecotypes. As a result, agricultural systems have largely relied on intra-specific rather than inter-specific diversity and it is not yet clear how well BEF theory predicts the relative benefits of these different levels of phylogenetic diversity. We used a combination of field experiments and meta-analysis to assess the impact of increased intra- and inter-specific biodiversity. We tested to efficacy of phylogenetic distance as a predictor of ecosystem functions such as productivity, weed suppression and biological nitrogen fixation.
Results/Conclusions
Field experiments demonstrated that biomass production, weed suppression and nitrogen fixation were not always greater in cover crop mixtures compared to monocultures. The outcomes of greater phylogenetic diversity depended in part on the functional diversity of these multi-species mixtures. In our meta-analysis of forty studies testing the impact of cultivar mixtures found that phylogenetic distance was a reasonably good predictor of biomass production and yields. We compared 1250 pairs where single cultivar plantings were compared to cultivar (intra-specific) mixtures of grain crops such as wheat, barley, soybean, maize and sorghum using yield as the response variable. We found that 65% of the comparisons reported greater yields in cultivar mixtures compared to those with a single cultivar. Our preliminary results suggest that both intra-specific and inter-specific plant diversity can plant important roles in enhancing the provision of ecosystem services; however these metrics of phylogenetic diversity were not always sufficient in prediction outcomes.