Ecological Contingency

Priority and Year Effects in Restoration (PRYER)

In 2013, I began working as a graduate student researcher on an NSF-funded multi-year experiment headed by Truman Young on contingencies in plant community ecology in the context of ecological restoration, and I remain a collaborator on this project post-graduation. Certain contingencies are familiar to most ecologists- it’s not surprising to find that similar studies conducted in different ecosystems, or with different species, have different outcomes. Other contingencies are less widely acknowledged. For instance, will the exact same experiment have different results if initiated in different years? Experiments are rarely initiated more than once, but literature review suggests that different results (which often point to entirely different conclusions!) are frequently obtained from experiments conducted in different years. The PRYER project examines several layers of contingency by initiating the same two experiments over four years in three different locations in California.

PRYER experiment at the UC Hopland Research and Extension Center

PRYER experiment at the UC Hopland Research and Extension Center

Short-term priority experiment: To examine short-term priority effects on the success of native grasses, native and exotic grasses are seeded into experimental plots either alone, together, or with exotics planted two weeks after natives.

Long-term priority experiment: To examine long-term priority effects on the relative success of two guilds of native grassland species, native forbs and native grasses are seeded into plots alone, together, or with one guild planted one year after the other.

Results from all years of initiation are monitored over time, to track how initial differences translate to long-term differences in plant community composition. Such experiments in restoration ecology are excellent opportunities to test theories in plant community ecology, like succession and assembly theory. Broadly speaking, succession theory would suggest that plant communities should converge on a “climax state” with a relatively fixed species assemblage over time, while assembly theory would suggest that multiple alternative stable states with different species composition could arise based on different initial conditions. The extent to which resultant plant communities are governed by successional inevitability vs. initial conditions is of critical importance to restoration practitioners, who constantly struggle with restoring habitat to a desired state in economical and effective ways.

My roles in the PRYER project have included hiring and organizing teams of undergraduate field assistants, assisting in project implementation, analyzing and graphically presenting data, and preparing scientific papers.


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