A Mechanistic Study of Plant and Microbial Controls over R* for Nitrogen in an Annual GrasslandReport as inadecuate




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Differences in species- abilities to capture resources can drive competitive hierarchies, successional dynamics, community diversity, and invasions. To investigate mechanisms of resource competition within a nitrogen N limited California grassland community, we established a manipulative experiment using an R* framework. R* theory holds that better competitors within a N limited community should better depress available N in monoculture plots and obtain higher abundance in mixture plots. We asked whether 1 plant uptake or 2 plant species influences on microbial dynamics were the primary drivers of available soil N levels in this system where N structures plant communities. To disentangle the relative roles of plant uptake and microbially-mediated processes in resource competition, we quantified soil N dynamics as well as N pools in plant and microbial biomass in monoculture plots of 11 native or exotic annual grassland plants over one growing season. We found a negative correlation between plant N content and soil dissolved inorganic nitrogen DIN, our measure of R*, suggesting that plant uptake drives R*. In contrast, we found no relationship between microbial biomass N or potential net N mineralization and DIN. We conclude that while plant-microbial interactions may have altered the overall quantity of N that plants take up, the relationship between species- abundance and available N in monoculture was largely driven by plant N uptake in this first year of growth.



Author: Stephanie G. Yelenik , Benjamin P. Colman , Jonathan M. Levine, Janneke HilleRisLambers

Source: http://plos.srce.hr/



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