Role of soil organisms in response of plants to novel environments

Our high elevation mixed conifer site 

We study plant-soil organism interactions and how these interactions may facilitate plant adaptation to novel environments. Climate change has the ability to force plants into novel environments in multiple ways. For one, as temperatures warm, plants may be forced to adapt to warmer and potentially drier environments while staying where they currently live. Alternatively, plants may be able to migrate to environments that are either higher in elevation or further away from the equator in latitude allowing them alleviate stress from a warming environment by moving to a cooler one. The second option may require that plants are exposed to other novel aspects of their environment, such as different soils derived from unique parent materials, new soil organism communities, or different combinations of plant and insect communities. Plant migration could also be accelerated by the hand of land managers, but at what cost?

A natal site for blue grama in the middle of monsoon season

Ponderosa Pine growing at its
natal site 

To address these issues my research uses common gardens across an elevation gradient with several unique soils. We are focusing on two important plant species in the southwest, Bouteloua gracilis (Blue grama) and Pinus ponderosa (Ponderosa Pine). We grow plants in the following soil and soil organism combinations 1) natal soil with home team soil organism, 2) natal soil with away team soil organism, 3) novel soil with home team soil organisms, and 4) novel soil with away team soil organisms. Each one of these treatment combinations is then planted at the plants home site and then two sites of lower elevation to simulate warming and two sites at higher elevation to simulate cooling, a phenomena a plant may experience in assisted migration or rapid natural migration. One generalized hypothesis is that plants will be dependent on their home team soil organisms when adapting to novel environments, especially when the novel environment is stressful. Thus we expect to find that soil organisms from the plant's home site help alleviate limitations in plant growth when plants are moved to higher or lower elevations and when plants are grown in novel soil environments.

In the past, we have conducted smaller projects to address the following questions:

1. Can soil organisms from a dry environment facilitate plant adaptation to drought?
2. Does cheatgrass change soil organism communities in a way that has a lasting negative legacy on the native blue grama?

These studies showed us that plants receive the greatest benefit of being paired with their "home-team" soil organisms, regardless of environmental conditions. We found that as long as plants were paired with the home-team, their growth was enhanced, both under dry and wet watering regimes, relative to sterile controls or away-team pairing.

We also found that soil organisms communities that had bee manipulated by cheatgrass inhibiting growth of blue grama, even relative to sterile controls.  This is likely due to the combined effects of reduced mycorrhizal fungi abundance and the presence of soil pathogens.

Both these findings support the idea that in both adaptive management and ecological restoration, pairing plants with their home team soil organisms enhance plant growth relative to pairing plants with the soil organisms present in their novel environment. These studies show the role soil organisms play in facilitating plant adaptation to novel environments created in climate change and plant migration scenarios or those created by the invasion of exotic plant species.

A low elevation desert grassland site being used in our experimental garden