9627928 Biondini The objective of the proposed research is to investigate how the competitive ability of plants is linked to an interaction between their root scaling properties and the supply rate and scaling properties of soil resources. The operating hypothesis is that: (1) nutrient supply rates and the spatial scaling of soil nutrients are two equally important and interactive constraints to plant growth; and (2) plants contend with these constraints through a trade-off in the way they scale root biomass to total rooting volume, root surface density, and root proliferation. Testable hypotheses were derived from a model that relates the competitive ability of plants to the interaction between the scaling properties of their root system and the scaling properties of the resources they utilize. The protocols for testing the proposed hypotheses involve two sets of experiments. The first is designed to determine the root lateral spread, root length, root density, and the distribution of root surface areas of selected plants in the presence and absence of nutrient patches. Plants will be grown in containers with grid panels located at fixed intervals designed to keep roots in place once the soil is removed. Nutrient patches will be generated by Sierra slow release fertilizer prills. Roots will be sampled by grid depth, separated based on fertilizer location, digitized, and analyzed for the desired parameters with a Delta-T Scan imaging system. The second set of experiments will test how the spatial distribution and supply rate of nutrients can affect plant competition. The experimental system consists of a 3x12x0.3 m growth container equipped with 3,600 trickle irrigation emitters arranged in a grid pattern at 10 cm intervals. This system is designed to control the spatial scaling, and supply rates of nutrients. Each emitter is controlled by one of 10 Dosatron injectors that delivers the desired amount of nutrient within a lOxlO cm area. The design has the capability of generating spatial patter ns as well as independent or simultaneous time patterns for nutrients and water delivery. All experiments will be organized as 2x3 factorials. Factor 1 will consist of 2 spatial scaling factors for either N or P. Factor 2 will consist of 3 mean N or P supply rates. N and P will be used to account for differences in mobility and buffer power among soil nutrients. Each of 5 replications will consist of 400 plants from 10 species (40 plants/species) with distinct root scaling patterns selected from the root architecture experiment. To test the repeatability of results, each experiment will be conducted twice with two distinctly different combinations of 10 species.
