Microbial Mutualisms and Belowground Plant-microbe Interactions
In our lab, we study how plant-microbe interactions belowground affect plant performance, plant response to stressors and global change, and other species interactions, including plant competition.
PLANT-SOIL FEEDBACKS AND THE INVASION AND IMPACT OF INTRODUCED PLANTS
Plants growing in Dittrichia-conditioned vs control soil
PLANT-SOIL FEEDBACKS AND RANGE EXPANSION
As plants spread to new environments during range expansion, they will experience changes in the soil microbial community, which may affect both mutualistic and pathogenic plant-soil interactions. Using parallel greenhouse experiments in collaboration with Wim van der Putten at the Netherlands Institute of Ecology, we are studying how plant-soil interactions have changed during the native and exotic range expansion of Dittrichia graveolens (L.) Greuter (Asteraceae). This annual plant is currently expanding both its European native range with climate change and invading California, allowing us to examine the impact of plant-soil feedbacks under these two scenarios.
SOIL LEGACY EFFECTS OF AN INVASIVE SHRUB
The impacts of an invasive species may persist even after the invader itself has been removed from the system. Such “legacy effects” on an ecosystem may include both biotic and abiotic factors, and their temporal dynamics are remarkably poorly known considering their importance. Our lab, collaborating with Karen Haubensak at Northern Arizona University, has been at the forefront of investigating the legacy effects of invasive Scotch broom (Cytisus scoparius (L.) Link; Fabaceae) on soil microbial communities and biogeochemistry.
For more examples see our publications, including:
Grove, S., Haubensak, K. A., Gehring, C., & Parker, I. M. 2017. Mycorrhizae, invasions, and the temporal dynamics of mutualism disruption. Journal of Ecology, 105(6), 1496-1508.
Davis et al. 2021, Graphic @ Erin Aiello
PLANT-SOIL FEEDBACKS AND INVASION IMPACTS
It has been proposed that invasive plants may reach high density because they show positive plant-soil feedbacks. Our most recent experiments have shown that the microbial mutualists mycorrhizae and rhizobia both did increase in soils invaded by C. scoparius, yet we also found that the overall net effect of the plant-soil feedback was negative.
For more details, see:
Grove, S., Parker, I. M., & Haubensak, K. A. 2017. Do impacts of an invasive nitrogen‐fixing shrub on Douglas‐fir and its ectomycorrhizal mutualism change over time following invasion? Journal of Ecology, 105(6), 1687-1697.
Davis, EJ, S Grove, KA Haubensak, and IM Parker. 2021. A widespread nitrogen-fixing invader experiences neative soil feedbacks despite enhancing the abundance of beneficial soil microbes. Plant and Soil. doi.org/10.1007/s11104-020-04804-w
MYCORRHIZAE AND INTERACTIONS BETWEEN NATIVE AND INVASIVE PLANTS
Mycorrhizal fungi can mediate plant stress in many ways. These mutualists can increase a plant's reach into the soil and break down nutrients otherwise unavailable to the plant. Mycorrhizal fungi can also form a network between plants in the community, enabling them to share resources underground. By these mechanisms, mycorrhizal fungi reduce stress from drought, limited nutrients, and asymmetric competition. Mycorrhizae can also bolster a plant's defenses against pathogens.
Invasive plants can disrupt mycorrhizal mutualisms for native plants, lowering their resistance to the aforementioned stressors. Invasive plants can also tap into mycorrhizal hyphal networks and steal resources from nearby natives, and their own mycorrhizae help them to compete more strongly. Further, added stress from invasive plants can weaken a native plant, making it less resistant to disease.
We have studied this in Douglas-fir forests that have been invaded by Cytisus scoparius. In the greenhouse, we found that C. scoparius invasion decreases mycorrhizal colonization of Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco; Pinaceae) roots and changes the effect of soil microbes on Douglas-fir stress, survival, and growth - hinting that C. scoparius may also decrease Douglas-fir's resistance to soil pathogens. We are currently asking whether native plants facilitate invasion of Genista monspessulana (L.) O.Bolós & Vigo (Fabaceae) by sharing beneficial microbes with them, and whether this relationship changes when competing native plants are removed, but their microbes remain.
You can find publications from these projects and more at Ingrid's Google Scholar page.