Incorporating microbes into plant community ecology
Mangan, Scott A. , Schnitzer, Stefan A. .
Plant-soil feedbacks and relative tree species abundance in a tropical forest in Panama.
Negative interactions between plants and their soil biota have been hypothesized to be important in maintaining plant diversity and determining plant relative abundance in both grassland and forest ecosystems. Negative plant-soil feedbacks (NPSF) occur when species-specific soil enemies accumulate under established plants, and in turn, reduce the recruitment of conspecific offspring relative to heterospecific offspring, thereby preventing any one species from dominating the plant community. In a previous study, we showed that variation in strengths of negative feedback caused by some aspect of the soil biota is important in determining relative abundance of tropical trees in Panama. Here, we present results from a fully reciprocal biocide experiment designed to test whether an important group of soil-borne enemies (oomycetes) are the primary soil-borne enemies driving NPSF at the seedling stage. We hypothesized that if oomycetes are sufficiently species-specific with their hosts and drive NPSF, then the strength of NPSF should lessen with the application of an oomycete-specific biocide. Contrary to our hypothesis, the addition of the biocide significantly increased the strength of community-wide NPSF relative to unmanipulated soil communities (P = 0.010). Specifically, the strength of NPSF per species increased in all five species examined, and significantly so in three of those species. The unequal effect of biocide on NPSFs among species led to the breakdown in the relationship between the strength of feedback and relative abundance. In unmanipulated soils, tree species exhibiting stronger negative feedbacks were less common as adults than those species exhibiting weaker negative feedbacks or positive feedbacks (R2 = 0.82, P =0.034). However, no relationship between the strength of feedback and abundance was detected in biocide-treated soils (R2= 0.19, P = 0.458). Our multiple plant-species approach contradicts single-species studies and suggests that oomycetes are not direct drivers of NPSFs. Instead, oomycetes appear to be generalists and may compete with other species-specific organisms important to this process.
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1 - University of Wisconsin - Milwaukee, Department of Biological Sciences, P. O. Box 413, Milwaukee, WI, 53201, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Westminster Room/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 9:15 AM