The Environmental & Plant Biology Colloquium Series presents Ryan Dorkoski on “Investigating the Influence of Phosphorus Availability on Below-ground Processes in Forested Ecosystems” on Friday, Feb. 19, at 11:50 a.m. in Porter Hall 104.
Ryan Dorkoski
Dorkoski is a Ph.D. candidate in Dr. Jared DeForest’s lab in the Environmental & Plant Biology Department at Ohio University.
Abstract: As a consequence of chemical climate change, acid rain has been altering our forest ecosystem structure and function over the last several decades. Acid rain deposition acidifies the environment and adds nitrogen, which may shift historic nitrogen limitation in temperate forests to more stress being placed on phosphorus. While ecosystem nitrogen dynamics are fairly well understood, further research is needed on how decreased phosphorus availability may be impacting soil microbial community function, and inputs of soil carbon from fine root turnover. These investigations made use of field sites established in 2009 based on soil age by considering glaciated and unglaciated soils in Eastern Ohio. Field sites were manipulated annually to indirectly and directly increase phosphorus availability, with the intent of reaching soil phosphorus saturation. Overall, phosphorus enrichment decreased soil phosphorus-acquiring enzyme activity compared with ambient soils. Interestingly, soil phosphorus-acquiring enzyme activity was increasingly suppressed over the six years since site initiation due to indirect phosphorus treatments (P < 0.01) in the glaciated (r = 0.50) and unglaciated soils (r = 0.42). Decreased soil biota phosphorus-acquiring enzyme dependence suggested that phosphorus saturation has not yet been met in these acidic soils, even after six growing seasons of phosphorus enrichment. Further, direct phosphorus additions were responsible for decreased plant dependence on arbuscular mycorrhizal fungi in unglaciated soils (P < 0.01), which is likely reducing energy available to the microbial community and therefore may suppress ecosystem nutrient cycling. In conclusion, the findings presented here add to the body of evidence suggesting that environmental acidification may be shifting emphasis from temperate forest nitrogen limitation to more importance on phosphorus, which could drastically alter the function and structure of our hardwood forest ecosystems.
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