Positive biodiversity-productivity relationships have been found in biodiversity field experiments of grassland, forestry, and other natural terrestrial ecosystems, where diversity effects were separated by complementarity (CE) and selection effects (SE). However, we know little about how CE and SE are related to root traits and root dissimilarity. A four-year field experiment was carried out with a split-plot design, where main plot was four nitrogen (N) applications (N0, N1, N2, N3) and five cropping systems (maize (Zea mays L.)/soybean (Glycine max L. Merrill.), maize/peanut (Arachis hypogaea L.) intercropped and the corresponding monocultures) with three replicates. Roots were sampled in the N0 and N2 treatments in two years. Intercropping effects were analyzed based on grain yield for four years and roots were sampled down to 60 cm depth, and analyzed with morphological parameters at different crop growth stages in two years. Intercropping significantly increased grain yield and aboveground biomass in both intercropping systems under all N treatments. The partitioning of the net intercropping effects showed that yield advantage in intercropping was due to a positive CE under the N0 treatment, and to a positive SE with N application. Maize showed greater root morphological plasticity than the legumes did, with greater changes in root length density (RLD), root weight density (RWD) and total root surface (TS) in intercropping than in monoculture. Intercropped maize occupied a larger soil space, while lateral RLD distribution of legumes was decreased by maize. The RLD, RWD, and TS of intercropped maize were constant or increased in later growth stages. SE showed a significantly positive relationship with root dissimilarity. Principal component analysis showed mean root depth and specific root length of legumes drove the positive CE in the absence of N fertilization. Root dissimilarity determined by maize explained the selection effects in overyielding. Complementarity effects under N0 were closely associated with specific root traits such as mean root depth and specific root length. Linking changes of root traits with intercropping effects aboveground helps understand yield advantages in diverse agroecosystem. In general, a cereal species with strong phenotypic plasticity intercropped with a legume species with strong physiological plasticity can maximize the yield advantage of intercropping.
|Date made available||2022|