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My full publication list can be found here: https://scholar.google.com/citations?user=2RHw5JYAAAAJ&hl=en&oi=ao
Some highlighted projects are described below:
Tracing salmon-derived nutrients through mycorrhizal fungal networks
The return of Pacific salmon from the ocean allows for the transfer of marine-derived nutrients (MDN) from marine to terrestrial ecosystems. However, the effect of MDN on fungi and the significance of fungi as an MDN sink in the soil has been almost entirely overlooked. We examined the effect of salmon carcass deposition on fungi using stable isotope analysis and genetic sequencing at one of the most studied salmon stream in the world in SW Alaska. We found that fungi uptake and retain MDN in fungal tissue for years following a long-term carcass deposition, suggesting a potentially significant MDN sink in fungi. We also found that MDN increased %N in fungal tissue and is thus ecologically significant for fungi and riparian functions.
Mapping fungal communities in salmon forests
Fungal communities have rarely been examined in riparian systems, especially fungi associated with salmon. We found that salmon altered fungal communities, and effects on community structure varied with spatiotemporal scale. Short-term, nearby decomposing carcasses increased the richness and diversity of saprotrophic fungi, and also increased the relative abundance and diversity of long-distance and medium-distance ectomycorrhizal fungal species. A multi-decadal, long-term carcass deposition experiment increased the relative abundance, richness, and diversity of long-distance ectomycorrhizal fungi, yet decreased the richness and diversity of short-distance ectomycorrhizal fungi. Long-distance fungal foragers can maintain a large network structure and efficiently mine nutrient hotspots, particularly phosphorus, likely limiting in this system. These fungi are also especially effective with pulsed nutrient additions that creates resource spatio-temporal heterogeneity, such as salmon inputs. Many long-distance types are in global decline, suggesting that preserving salmon habitat and salmon populations might be important for the conservation of genetically significant and threatened long-distance fungal taxa in these areas, as well as for promoting carcass-associated saprotrophic fungal taxa.
Modeling drivers of forest belowground productivity and carbon allocation
Forests are threatened by a multitude of stressors, including anthropogenic disturbances and climate change. Assessing how forests will respond to these stressors requires a comprehensive understanding of net primary productivity (Npp), environmental constraints on growth, and adaptive capacity. A parameter of significant uncertainty is belowground Npp (bNpp), which can account for up to 80% of total Npp but is poorly estimated and rarely measured directly. We used a global dataset of direct, field-based measurements of aboveground and belowground primary productivity alongside climatic and soil variables to identify potential constraints on bNpp and belowground carbon allocation. Across biomes, soil variables, rather than climate variables, were the main drivers of bNpp and belowground allocation. This suggests that soil nutrient dynamics, especially soil nutrient pool and flux variables, must be explicitly modeled to more accurately predict feedbacks between climate, productivity, and within-tree carbon allocation. Within biomes, environmental drivers of belowground allocation varied between low vs. high allocation forests, indicating that environmental drivers are site-specific and the development of within-biome, site-scale classifications for forest ecosystems could be useful. Changes in soil variables, such as increasing soil nitrogen pools, caused abrupt and large decreases in bNpp for boreal, but not cold temperate forests. These threshold-like shifts indicate that boreal forests might have lower adaptive capacity and higher sensitivity to disturbances than cold temperate forests. With 70% of boreal forests characterized by low bNpp, disturbances such as nitrogen deposition could cause large-scale decreases in bNpp that could push these forests beyond their adaptive capacity.
Remnant trees increase bat activity and facilitate the use of vineyards by edge-space bats
Conversion of natural habitats to vineyard monoculture is rapidly increasing both globally and on the California central coast. Although agricultural expansion typically decreases species diversity and abundance, landscape heterogeneity can maintain biodiversity, ecosystem function, and provide pest control services within agricultural systems. Large remnant oak trees are sometimes retained within vineyards, yet little is known about their value to biodiversity or the beneficial services to grape growers. While insectivorous bats (order: Chiroptera) are natural predators of agricultural pests and commonly utilize trees for foraging and roosting, no study has quantified the influence of remnant trees within vineyards on bat abundance and diversity. We found that bat activity rates were were significantly higher at trees compared to open areas. Activity levels of low-frequency echolocators adapted to open habitats did not differ between trees and open areas; however, activity levels of high frequency echolocators adapted to edge habitats were 2.4 times higher at trees than open areas. Bat activity at trees increased with larger tree size, closer neighboring remnant trees, and lower remnant tree density in the surrounding landscape. This indicates that remnant trees within vineyards provide important habitat value for bats at the landscape-scale by allowing edge-space adapted bat species access to vineyards. Retention of individual large trees can help to maintain biodiversity and ecological function in vineyard landscapes, a benefit for both conservation and agricultural production.
Safety in numbers keeps Pacific salmon safe at sea
Grouping is ubiquitous across animal taxa and environments. Safety in numbers is perhaps the most cited reason for grouping, yet this fundamental tenet of ecological theory has rarely been tested in wild populations. We analyzed a multidecadal dataset of Pacific salmon at sea and found that individuals in larger groups had lower predation risk; within groups of fish, size outliers (relatively small and large fish) had increased predation risk. For some species, grouping decreased foraging success, whereas for other species, grouping increased foraging success, indicating that safety competition trade-offs differed among species. These results indicate that survival and growth depend on group size; understanding the relationship between group size distributions and population size may be critical to unraveling ecology and population dynamics for marine fishes.
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