FUNCTIONAL CONSEQUENCES OF SPECIES RANGE SHIFTS IN SUBALPINE WETLANDS
I've worked in a pond and wetland system near the Rocky Mountain Biological Laboratory since my undergraduate years at Allegheny College. This system is shaped by multiple ecological gradients, including an elevational gradient from montane (~8,000 m) to subalpine (~12,800 m) and a “predator-permanence” gradient that influences predator types (vertebrate vs. invertebrate) and pond hydroperiods (temporary, semi-permanent, and permanent). Long-term monitoring has documented seven upslope species range expansions over 30 years, showing how climate change is reshaping pond communities. My research focuses on the roles of individual species and entire pond communities in key ecosystem functions, such as nutrient cycling and detritus processing, across these gradients and over time. Here is a link to recording of an invited seminar about this work, hosted by the Rocky Mountain Biological Laboratory on 21 June 2022. Otherwise, read more about some of my individual publications below!
High interspecific variation in nutrient excretion within a guild of closely related caddisfly speciesBalik, J. A., Taylor, B. W., Washko, S. E., & Wissinger, S. A. (2018). High interspecific variation in nutrient excretion within a guild of closely related caddisfly species. Ecosphere, 9(5), e02205. (DOI, PDF) Organisms can have large effects on ecosystem processes such as nutrient cycling, but these can be difficult to study directly in natural systems. Single species contributions are often particularly challenging to isolate and measure. However, species’ functional traits provide mechanistic links between organisms and their effects on ecosystem processes, and thus provide an indirect method of understanding species’ functional roles and contributions to overall ecosystem processes. In this first chapter of my dissertation, I quantified species-specific nutrient excretion rates of larval caddisflies that are biomass-dominant detritivores in subalpine ponds. I found considerable interspecific variation in biomass-specific excretion of nitrogen (eightfold differences) and phosphorus (sevenfold differences) among 10 larval caddisfly species. Then, through a meta-analysis, I compared the variation within this guild to the overall range in variation found among other family-level assemblages and found that, comparatively, the interspecific variation among caddisfly excretion rates was high for N and intermediate for P. This suggests that functional redundancy among species is difficult to predict, and consequently the functional outcomes of species gains or losses could be substantial. |
Animal-driven nutrient supply declines relative to ecosystem nutrient demand along a pond hydroperiod gradientBalik, J. A., Jameson, E. E., Wissinger, S. A., Whiteman, H. H., & Taylor, B. W. (2021). Animal-Driven Nutrient Supply Declines Relative to Ecosystem Nutrient Demand Along a Pond Hydroperiod Gradient. Ecosystems, 1-19. (DOI, PDF) Here, I combine nutrient excretion rates and biomasses of pelagic and benthic invertebrates and salamanders with nutrient uptake rates in a novel simulation model to estimate animal-driven nutrient supply and pond-level demand along a hydroperiod gradient of permanent ponds that never dry, semi-permanent ponds that dry in some years, and temporary ponds that dry annually. I found that animal biomass increased with hydroperiod duration, and biomass predicted animal-driven supply contributions among hydroperiod classifications. Consequently, community-wide supply was greatest in permanent ponds. N supply exceeded demand in permanent and semi-permanent ponds, whereas P supply equaled demand in both. Conversely, temporary ponds had large deficits in both nutrients due to lower biomass and hydroperiod-induced constraints on dominant suppliers (oligochaetes and chironomids). Thus, as climate warming causes hydroperiods to become increasingly temporary and indirectly prompts biomass declines and compositional shifts, animal-driven nutrient supply will decrease and strong nutrient limitation may arise due to loss of animal-driven supply. |
NSF Postdoctoral Research - Curating and archiving long-term ecological datasets
During my NSF Postdoctoral Scholar position at NCSU, I curated a 30-year dataset of montane and subalpine pond invertebrate communities and pond hydrology—the life’s work of my late undergraduate advisor, Dr. Scott Wissinger. When Scott passed unexpectedly in 2019, most of his data remained handwritten in field books. I had already digitized the larval caddisfly surveys during winter 2020 to complete my dissertation, but broader benthic invertebrate surveys and hydrology notes remained. To preserve this invaluable dataset, my doctoral advisor, Brad Taylor, and I secured funding for me to continue curating it post-graduation. Our group is now finalizing plans for archiving, and multiple manuscripts using these long-term data, led by collaborators at the University of Maine and Murray State University, are forthcoming.
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NSF Postdoctoral Research – Do Range-Shifting Species Alter Ecosystem Phenology? In September 2021, I became a co-PI on an NSF-RAPID grant with Drs. Amanda Klemmer (lead PI) and Hamish Greig (University of Maine) and Howard Whiteman (Murray State University) to study how a range-shifting larval caddisfly affects ecosystem phenology. During the 2021 summer field season at the Rocky Mountain Biological Laboratory, we documented an unprecedented population explosion of Nemotaulius hostilis, a recent range-expanding species. Based on egg mass counts, we estimate a 10–84× increase in density relative to previous observations. This surge in a potentially highly interactive detritivore is unparalleled in 30 years of long-term data. Extensive sampling of caddisflies, salamander predators, and ecosystem processes (nutrient excretion and detritus breakdown) from egg hatching in August 2021 through larval development in spring 2022 will reveal the mechanisms and consequences of this dramatic biotic perturbation. Manuscripts on this range-expanding species are forthcoming. |
Nemotaulius hostilis
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EFFECTS OF EARLY SNOWMELT PHENOLOGY ON HEADWATER STREAM BIOGEOCHEMISTRY
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When I began my doctoral studies at NCSU, I also did some work in streams near the Rocky Mountain Biological Laboratory. The objective of my stream research was to understand how climate induced changes in the phenology of seasonal transitions could affect stream ecosystem structure and function. Understanding phenological changes is pressing because shifts in the seasonal phenologies of both aquatic and terrestrial processes will accompany and could compound other ecological impacts of climate warming on stream ecosystems. In mountainous regions, recent studies show shifts towards earlier spring snowmelt and associated runoff, causing river flows to peak earlier and consequently reducing late season flow. Flow is a fundamental driver of water quality, energy and material transport, physical habitat, life history evolution, productivity, and biotic interactions in rivers; thus, changes in flow or its timing can transform a river’s structure and function.
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High-discharge disturbance does not alter the seasonal trajectory of nutrient uptake in a montane stream
Balik, J. A., West, D. C., & Taylor, B. W. (2021). High-discharge disturbance does not alter the seasonal trajectory of nutrient uptake in a montane stream. Hydrobiologia, 848(19), 4535-4550. (DOI, PDF)
Here, we document the effects of a large midsummer flood event on the seasonal trajectory of reach-scale nitrogen and phosphorus uptake in the East River, a high elevation oligotrophic stream in central Colorado near the RMBL. Classic stream disturbance literature predicts that reach-scale nutrient demand should increase as benthic biofilms recover from the bed scour that occurs during floods. However, these classic studies are based on streams that flood frequently and are highly adapted to disturbance. In contrast, the East River experiences spring snowmelt peak flows followed by typically stable summertime base flows. We found that biofilm biomass accrued and areal P uptake increased after the midsummer flood. Whereas, during the same seasonal timeframe in a reference year without any midsummer floods, biofilm biomass and P uptake declined. N uptake did not change in either year. A higher proportion of algae in benthic biofilms was associated with greater uptake of both nutrients, suggesting that algae drive uptake. Thus, in a stream that infrequently receives floods during the growing season, algal biofilm accrual following a midsummer flood is a significant predictor of nutrient processing rates.
Balik, J. A., West, D. C., & Taylor, B. W. (2021). High-discharge disturbance does not alter the seasonal trajectory of nutrient uptake in a montane stream. Hydrobiologia, 848(19), 4535-4550. (DOI, PDF)
Here, we document the effects of a large midsummer flood event on the seasonal trajectory of reach-scale nitrogen and phosphorus uptake in the East River, a high elevation oligotrophic stream in central Colorado near the RMBL. Classic stream disturbance literature predicts that reach-scale nutrient demand should increase as benthic biofilms recover from the bed scour that occurs during floods. However, these classic studies are based on streams that flood frequently and are highly adapted to disturbance. In contrast, the East River experiences spring snowmelt peak flows followed by typically stable summertime base flows. We found that biofilm biomass accrued and areal P uptake increased after the midsummer flood. Whereas, during the same seasonal timeframe in a reference year without any midsummer floods, biofilm biomass and P uptake declined. N uptake did not change in either year. A higher proportion of algae in benthic biofilms was associated with greater uptake of both nutrients, suggesting that algae drive uptake. Thus, in a stream that infrequently receives floods during the growing season, algal biofilm accrual following a midsummer flood is a significant predictor of nutrient processing rates.
