Prairie restoration is a major focus of CNLM and its partner organizations. Conservationists invest significant time and resources growing native forb (wildflower) and grass seedlings in nurseries and then planting out those seedlings on former prairie lands to restore habitat. The restored habitat is essential for the survival of native fauna, such as Taylor’s checkerspot butterfly, a candidate for listing under the Federal Endangered Species Act.
Re-planting the prairies in this way has been fairly successful: 80% of the seedlings survive the initial year after planting. However, only 20 to 30% make it through the third year. CNLM wants to increase the odds of seedling survival.
To do that, conservationists at CNLM are focusing on the soil. Scientists believe that the small plug of nutrient-rich soil from the nurseries that is planted with the seedlings gets them through the first year. It appears that the die-off rate increases only after that healthy soil is depleted.
Poor-quality soil in prairie restoration areas is not surprising, given the history of these sites. The prairie soils naturally have very low nitrogen and phosphorus concentrations, however, native plants are adapted to these conditions. Scientists suspect that sites previously invaded by non-native species bear soil with chemical and biological legacies of those invasive species that may make it harder for native plants to establish. In other words, the soil is chemically depleted from those quick-growing invasives and also likely home to imported microbial communities unfavorable to native plants. Natural factors, such as Pacific Northwest summer droughts, also contribute to seasonably arid and inhospitable conditions.
Significantly altering the quality of prairie soil to be more amenable to native species would be a fairly large undertaking. What conservationists are hoping to do instead is alter the seedlings’ access to the nutrients that are present and protect them from drought and unfamiliar microbial pathogens by co-planting them with supportive mycorrhizae (the singular form is mycorrhiza).
Mycorrhizae, a type of fungus (myco) that creates a mutually beneficial (symbiotic) relationship with the roots of plants (rhiza), is known to be associated with 85 to 95% of terrestrial plants. Mycorrhizae create an intricate, underground network of structures called hyphae, which increase the absorptive surface area for nutrient and water uptake by up to 200 times. The relationship between the plant and the fungus is usually mutually-beneficial: mycorrhizae provide nitrogen, phosphorus and water to the plants and, in return, receive carbon (sugars) that the plants have acquired through photosynthesis.
The potential benefits of mycorrhizae are clear. The question CNLM is asking is whether the organisms can improve the long-term establishment of nursery plantings in prairie restoration areas. Conservationists also want to know whether mycorrhizae will increase the establishment of sown seeds, because seeding can be an efficient way of restoring prairies. While commercial mycorrhizal mixes are available, conservationists suspect that these generic mixes might not benefit the specialist prairie species. Prairie plants tend to be habitat-specific and thus will likely require specific mycorrhizal communities. Accordingly, researchers at CNLM have created a mycorrhizal mix specific to native PNW prairie plants.
CNLM researchers have also initiated a multi-year controlled study to determine the effectiveness of the native mix relative to a generic mix. In the Fall of 2011, researchers, Americorps members and interns outplanted seedlings and sowed seeds of ten native forb species in prairie habitat. The seeds and seedlings each were divided into three groups. One group of each was planted/seeded with no mycorrhizal inoculum (the control), one with the native inoculum and one with a generic, commercial inoculum. This summer, conservationists are evaluating the root systems to determine whether the mycorrhizae successfully colonized the prairie plants. In 2013, the researchers will evaluate the treatments by monitoring plant germination, survival and vigor (as measured by the size of the plant, number of flowers and number of flowering stems).
If the study shows that mycorrhizae are beneficial to certain native prairie seeds and seedlings, mycorrhizal inoculation of prairie restoration sites or individual species may become part of the restoration process for South Puget Sound prairies.
Article written by Carol Elewski
Edited by Sarah Hamman