Recipient Organization
MICHIGAN STATE UNIV
(N/A)
EAST LANSING,MI 48824
Performing Department
PLANT SOIL MICROBIAL
Non Technical Summary
Development of new bioenergy crops has the potential to reduce consumption of fossil fuels while also enhancing environmental benefits, including through building belowground soil carbon stocks. Switchgrass, a member of North American tallgrass prairie, has become a promising feedstock for bioenergy production. Yet, it is notoriously slow in generating soil carbon gains. We envision two solutions to this problem: 1) breeding switchgrass to have higher capacity to build soil carbon, and 2) developing switchgrass cropping systems that include other plant species to enhance the stabilization of carbon in the soil. To explore the feasibility of these solutions, we need to gain a better understanding of how switchgrass root systems and soil microorganisms interact with soil pore structure, and how this interaction results in stabilization of the fixed carbon that switchgrass allocates belowground.We will perform an in-depth analysis of the root biomass and structure, microbial symbionts, soil pores, and resulting soil carbon accumulation in two experiments. In the first, we will collect data from 18 switchgrass genotypes grown in the field at three locations (in MI, MO, and TX). In the second, we will collect data from a field experiment in which switchgrass is grown with nine other species as neighbors, including native species of grasses, forbs, and legumes. This study will provide knowledge about how soil structure, which is critical for protection of carbon in soil, is affected by switchgrass roots and microbial symbionts. In addition, we will be able to assess the most promising traits for plant breeding, and the most promising additional plant species for a multi-species cropping system, with the goal of enhanced soil carbon sequestration. The results of this study will benefit society by providing knowledge needed to design bioenergy cropping systems that have both high productivity and can capture carbon from the atmosphere.
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Goal: Bioenergy cropping systems that produce sizeable belowground C inputs may have a beneficial impact on climate change mitigation. Yet, monoculture switchgrass, one of the promising bioenergy crops, is notorious for being slow in generating lasting soil C gains. Our goal is to investigate two potential solutions leading to increased soil C sequestration:1) Selection of particularly beneficial switchgrass genotypes. We will work with multiple switchgrass genotypes at three field sites in a latitudinal gradient across the U.S., representing highly contrasting soil and climatic conditions. Our aim is to identify the traits that are promising for future breeding to enhance soil C sequestration.2) Multicropping with other plant species. We will survey multiple native plant species (including grasses, forbs, and legumes) for potential inclusion in switchgrass stands. In a field experiment involving switchgrass paired with other species, we will use 13C to label switchgrass-derived C. Our aim is to identify plant species that result in enhanced soil C sequestration when planted into switchgrass stands, and the mechanisms through which this occurs.Objectives: Our specific objectives for both goals and experiments described above include measurement of:Aboveground biomass, root biomass, and root trait data (including in switchgrass genotypes and neighboring species)Mycorrhizal fungal colonization and community composition (including in switchgrass genotypes and neighboring species)Soil pore structure and its relationship with soil CSoil C levels and fractionsSwitchgrass-derived portion of each C fraction in the 13C-labeled multicropping experimentIn addition, we will use structural equation modeling and path analysis to address complex casual relationships between the effects of plant genotypes, root characteristics, neighboring species, mycorrhizal colonization, and inherent soil properties resulting in sequestration of soil C.
Project Methods
Methods for Goal 1.To assess the variability of switchgrass root characteristics and their associations with AMF, pore structure formation, and soil C we will work with a Switchgrass diversity panel experiment that is replicated at three field sites. Each site features 18 switchgrass genotypes, which vary widely in their aboveground characteristics, as well as in rhizosphere and microbiota. The experimental sites are located in Austin, TX; Columbia, MO; and KBS, MI, and are representative of, respectively, three major soil types of the contiguous US (Alfisols, Entisols, and Mollisols). To understand the magnitude of variation among switchgrass genotypes, we will examine belowground biomass and a suite of root and mycorrhizal traits that represent key controls over the mechanisms of deposition and stabilization of belowground plant C in soil. Because the experiment is replicated in three regions with contrasting soils and climates, we will begin to understand plasticity in these traits and the strength of genotypic versus environmental controls. Intact soil cores will be taken from genotypes at each site, with (i) intact cores for root analyses (10 cm diameter), (ii) disturbed soil samples for C measurements, and (iii) intact soil cores for μCT pore characterizations. Root and fungal tissue will be sampled intensively using a combination of approaches. We will isolate roots, rhizosphere soil, and bulk soil from intact soil cores and, using root sections from these samples, we will examine morphological, anatomical, and chemical traits in roots, separately by root orders where appropriate. AM fungal communities in roots and soil will be characterized by next-generation sequencing, which will also be leveraged to measure AM fungal abundance in roots and soil, complementing microscopy in roots. Soil carbon will be characterized by fractionation into various labile and recalcitrant pools. In addition, X-ray μCT scanning at 10-30 μm resolutions, image analyses, and soil pore structure characterization will be conducted.Methods for Goal 2.To assess the role of the plant neighbor identity on the switchgrass-derived soil C inputs we will work in the Switchgrass neighbor experiment (KBS, MI). Switchgrass (var. Cave-in-Rock) is grown there with neighbors of three functional plant groups: grasses, forbs, and legumes. Each group is represented by three species common in the prairie community of the Midwest; selected, when possible, based on previous evidence of positive contributions to soil C gains. Root biomass and traits and AM fungal communities will be characterized within intact soil cores (5 cm diameter) collected in the space between the switchgrass individuals and neighbor species. To detect carbon of switchgrass origin we will conduct 13C pulse labeling of the switchgrass in the experimental plots, followed by root and soil sampling, X-ray μCT scanning and analyses of the intact cores, as well as soil analyses. In addition, 13C will be measured in MBC, POM-C, POX-C, MAOM, and SOC.