Controls on the productivity of exploited ecosystems
My dissertation explores several case studies on how we can better understand ecological drivers of productivity in exploited systems in order to improve resource management. In marine ecosystems, I am focusing on how predation influences fish population productivity. In terrestrial systems, I am exploring methods to better quantify productivity and carbon sequestration and their drivers in second-growth forests.
I first examined how well we can infer top-down effects from predators based on time series of aggregated biomass in age-structured populations of marine fish. I showed that we may often have trouble inferring predation effects because the populations have a complex structure, are very variable, and we do not observe them perfectly– not necessarily because the effects are not present.
- Oken, K.L. and T.E. Essington (2015) How detectable is predation in stage-structured populations? Insights from a simulation-testing analysis. Journal of Animal Ecology, 84: 60-70
In a collaboration with The Nature Conservancy, I then looked at a case study off the Washington coast to examine whether understanding and accounting for species interactions might actually create new fishing opportunities for piscivorous and highly productive lingcod populations that exist within rockfish conservation areas. I found that it is possible to balance lingcod predation on juvenile rockfish with incidental bycatch of adult rockfish and still sustain rockfish populations, but the patterns are highly dependent on how much and which sizes of rockfish lingcod consume.
- Oken, K.L. and T.E. Essington (2016) Evaluating the effect of a selective piscivore fishery on rockfish recovery within marine protected areas. ICES Journal of Marine Science.
- See the University of Washington press release here.
Carbon accretion in Southeast Alaska forests
As a statistics intern with the U.S. Forest Service Pacific Northwest Research Station, I worked with Ashley Steel, David D’Amore, and Paul Hennon to quantify the carbon accretion rate of young growth stands in Southeast Alaska. We utilized a long time series of growth measurements from a chronosequence of forest plots to obtain estimates of how carbon accretion changed as forest stands aged and experienced different management regimes. The work involved fitting non-linear mixed-effect models.
- D’Amore, D.V., K.L. Oken, P.Herendeen, E.A. Steel, and P.E. Hennon (2015) Carbon accretion in unthinned and thinned young-growth froest stands of the Alaskan perhumid coastal temperate rainforest. Carbon Balance and Management. 10: 1-12
Occupancy estimation of river otter populations
For my undergraduate thesis, I worked on a project with Bob Dobrow at Carleton, John Fieberg, who was then at the Minnesota DNR, and two other students to use occupancy models to study river otter populations in southeastern Minnesota based on wintertime aerial track surveys conducted over rivers. We used Bayesian models that incorporated a spatial component and false detection
- Aing, C., Halls, S., Oken, K., Dobrow, R. and Fieberg, J. (2011), A Bayesian hierarchical occupancy model for track surveys conducted in a series of linear, spatially correlated, sites. Journal of Applied Ecology, 48: 1508–1517