Potential alteration of plant-soil feedbacks following severe tornado damage in southern Appalachian forests

Background/Question/Methods

Plants alter their immediate soil environment in ways that may promote or inhibit recruitment and growth of the same species.  These plant-soil feedbacks are often mediated by accumulation of soil pathogens, microbial mutualists, or favorable nutrient ratios. Disturbances in general, and wind disturbance in particular, alter the environment in ways that may change plant-soil feedbacks during early stages of regeneration. Tornado-damaged patches exhibit higher temperatures, drier soils, and loss of fine root biomass that may change abundance or composition of soil microbes. Thus, soil organisms mediating plant-soil feedbacks in intact forests may be reduced or absent in blowdown patches. In this study, we examine a) differences in performance of three common southern Appalachian seedlings in same-species and different-species soil and b) whether the same relationship remains in tornado-damaged patches as in intact forest.

In April 2011, a severe (EF-5) tornado damaged sections of the Chattahoochee National Forest. We collected soil from the base of mature individuals of five species in intact patches and in tornado-damaged patches. Seedlings of three species (Quercus alba, Nyssa sylvatica, and Pinus strobus) were grown in same-species and different-species soil in a three-month greenhouse study. Plant-soil feedbacks are measured by differences in growth rate and biomass. 

Results/Conclusions

Preliminary results from one month of growth in the greenhouse suggest that Q. alba plant-soil feedbacks are neutral, and that severe tornado damage does not alter this relationship. Q. alba seedlings did not show any difference in growth rates between same-species (4.54 +/- 5.16 cm) and different-species (6.35 +/- 4.58 cm) soil treatments, nor between intact-forest (5.58 +/- 4.73 cm) and tornado-damaged (5.92 +/- 4.98 cm) soil treatments after one month (df = 3, p = 0.25). Oak seedling reliance on acorns for early nutrition may delay evidence of plant-soil feedbacks, by reducing the need for soil mutualists or by buffering seedlings against soil pathogens. Results for two other tree species, Nyssa sylvatica and Pinus strobus, will be presented when they are available.