Plant functional trait approach to manage short and long-term soil organic carbon Humans have extensively altered natural ecosystems for food production resulting in the loss of soil organic carbon (SOC) and a vast carbon debt. Regenerative practices such as utilizing diverse plant mixtures are recommended to enhance SOC in managed ecosystems. However, it is vital to understand how various plant species with distinct functional traits facilitate the sequestration of SOC that occurs along a plant-microbe-mineral continuum. Even more critical is to gain a comprehensive understanding of where this newly formed carbon is stored to predict the persistence and function of SOC under global changes. We utilize monocultures and diverse mixtures of cover crops belonging to various plant functional types as a model system, to predict the accrual and chemical composition of SOC in particulate -and mineral-associated soil fractions, representing the short and long-term soil carbon pools, respectively. (Funding: NSF CAREER grant; Startup funds from Clemson; Collaborator: Jason Kaye (Penn State). Zhang et al. 2022. Cover crop functional types differentially alter the content and composition of soil organic carbon in particulate and mineral- associated fractions. Global Change Biology; DOI: 10.1111/gcb.16296.
Fine root responses to global changes and soil resource heterogeneities Fine roots of trees that help in the uptake and transport of nutrients and water are constantly exposed to biotic and abiotic stress. Thus, they face an optimization challenge in the construction of their tissues to maximize defense against environmental stress without compromising their resource uptake functions. Although root morphological and physiological plasticity in response to stress is well studied, the accompanying plasticity in the quantity, composition, and localization of small molecules and biopolymers such as lignins, tannins, and suberins (chemical plasticity) are relatively less explored. We explore the chemical plasticity of fine roots along with their implications for fine root symbiosis with arbuscular and ectomycorrhizal fungi and soil carbon sequestration. We utilize advanced spectrometric techniques, confocal and FLIM microscopy, and chemometric approaches to unravel the chemical plasticity of fine roots. (Funding: NSF Ecosystems, EMSL-PNNL; Collaborators: Nishanth Tharayil, Luke McCormack, Peter Kennedy, Galya Orr, Dehong Hu).
Root exudate complexity and microbial functional redundancy This project is part of a recently funded National Science Foundation (NSF) Rules of Life (RoL) five-year grant that explores how microbial functional redundancy varies with substrate complexity. Functional redundancy, which is the extent of the duplicity of function across different microbial taxa, is an important driver of ecosystem resilience. As part of this collaborative project, our lab would explore the effect of increasing root exudate complexity on soil microbiome using plants belonging to different functional types including legumes, grasses, and brassica. We will detect and quantify the major root exudate metabolites and stable intermediaries that originate from the plant biosynthetic pathways. (Collaborators: Barbara Campbell, Sharon Bewick, Feng Luo & Anna Seekatz). For more information see the project website.
Mechanisms that regulate the specificity in the outcome of plant-arbuscular mycorrhizal symbiosis The high energy consumption for fertilizer manufacturing, coupled with the rapid depletion of raw materials for fertilizer production undermines the sustainability of current agricultural practices. Also, the aberrant climate exposes the crops to severe biotic and abiotic stressors, further compromising the potential yield. The association of plants with arbuscular mycorrhizal fungi (AMF) enhances the overall biomass productivity of ecosystems through enhanced stress resilience, and by facilitating resource foraging. Despite their potential benefits, the lack of a mechanistic understanding of the processes that drive the specificity of symbiotic associations precludes its utilization to enhance agricultural productivity. To elucidate the mechanisms underlying the specificity in the outcome, we focus on understanding the chemical communication between diverse Sorghum genotypes and AMF species that vary in their functional traits. (Funding: USDA NIFA; Collaborators: Barbara Campbell, Stephen Kresovich, Nishanth Tharayil).
Secondary metabolite mediated novel niche construction and implications for habitat restoration One of the pathways by which exotic invasive plant species engage in niche construction is through the production of secondary metabolites novel to the ecosystems they invade. A majority of these metabolites that enter the soil through decomposition of senesced tissues and/ or through root exudates have long-lasting properties that make irrevocable changes to soil properties, nutrient cycling, and soil microbial and faunal communities. Although previous research has elucidated the function of plant secondary metabolites from a defense perspective, a mechanistic understanding of the processes involving the post-establishment success of plant species through secondary metabolite mediated niche construction is lacking. Such interactions could ultimately lead to the successful colonization and spread of many invasive species. We investigate the pathways through which invasive species engage in niche construction and formulate strategies to reverse their legacy effect. [Funding: United States Department of Agriculture (USDA)- Agricultural Food Research Initiative (AFRI); Collaborator: Prasanta C Bhowmik]