Exploring the importance of time and location - when plant genotypes shape biogeochemical cycling

Background/Question/Methods

nteractions among organisms can shape biogeochemical cycling. In fact many of the talks in this session explore this topic. These interactions, especially when embedded in different climates, can shape plant traits. Differences among individuals in plant traits, via differences in genotypes and phenotypes, can alter the way nutrients are cycled in an ecosystem. For example, changes in leaf nitrogen resorption can alter the amount of nitrogen reaching the decomposer community; while changes in leaf area may alter soil microclimate. The impact of these genotype-specific traits may vary over time or across different types of ecosystems with different nutrient and climate constraints. We will present case studies from seemingly disparate systems that explore how changes in plant genotypes/phenotypes alter biogeochemical cycling over long and short time periods. The first study was conducted in a semi-arid piñon-juniper woodland that contains piñons that were either susceptible or resistant to a chronic herbivore. The second study takes advantage of a common garden study in Connecticut and Tennessee that measured decomposition rates of different combinations of Solidago genotypes in home and away systems. 

Results/Conclusions

Like many other studies, our work shows that plant genotypes can alter ecosystem process; however, these impacts can vary from system to system as well as over time. For example, we found that herbivore resistance and susceptible traits of piñon pine increased the amount of nitrogen entering the soil system, but this effect did not alter nutrient cycling in the ecosystem over several years. Because herbivores make susceptible trees grow more slowly, herbivore-susceptible trees slowed nutrient cycling on the landscape. Similarly, in a decomposition experiment at two sites where we selected Solidago genotypes from each site with the widest leaf litter trait variation, we found that our trait of interest (specific leaf area) predicted mass loss, but the ecosystem it was being decomposed in affected the trait’s control over decomposition rate. We will wrap things up by comparing the relative influence of genotype/phenotype expression in our systems with that of species diversity. Relative to shifts in species diversity, are the impacts of genotypes on biogeochemical cycling ephemeral?