Scholarly Work - Ecology
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/8716
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Item Environmental warming increases the importance of high‐turnover energy channels in stream food webs(Wiley, 2024-05) Junker, James R.; Cross, Wyatt F.; Hood, James M.; Benstead, Jonathan P.; Huryn, Alexander D.; Nelson, Daniel; Ólafsson, Jón S.; Gíslason, Gísli MárWarming temperatures are altering communities and trophic networks across Earth's ecosystems. While the overall influence of warming on food webs is often context-dependent, increasing temperatures are predicted to change communities in two fundamental ways: (1) by reducing average body size and (2) by increasing individual metabolic rates. These warming-induced changes have the potential to influence the distribution of food web fluxes, food web stability, and the relative importance of deterministic and stochastic ecological processes shaping community assembly. Here, we quantified patterns and the relative distribution of organic matter fluxes through stream food webs spanning a broad natural temperature gradient (5–27°C). We then related these patterns to species and community trait distributions of mean body size and population biomass turnover (P:B) within and across streams. We predicted that (1) communities in warmer streams would exhibit smaller body size and higher P:B and (2) organic matter fluxes within warmer communities would increasingly skew toward smaller, higher P:B populations. Across the temperature gradient, warmer communities were characterized by smaller body size (~9% per °C) and higher P:B (~7% faster turnover per °C) populations on average. Additionally, organic matter fluxes within warmer streams were increasingly skewed toward higher P:B populations, demonstrating that warming can restructure organic matter fluxes in both an absolute and relative sense. With warming, the relative distribution of organic matter fluxes was decreasingly likely to arise through the random sorting of species, suggesting stronger selection for traits driving high turnover with increasing temperature. Our study suggests that a warming world will favor energy fluxes through “smaller and faster” populations, and that these changes may be more predictable than previously thought.Item The ghosts of ecosystem engineers: Legacy effects of biogenic modifications(Wiley, 2022) Albertson, Lindsey K.; Sklar, Leonard S.; Tumolo, Benjamin B.; Cross, Wyatt F.; Collins, Scott F.; Woods, H. ArthurEcosystem engineers strongly influence the communities in which they live by modifying habitats and altering resource availability. These biogenic changes can persist beyond the presence of the engineer, and such modifications are known as ecosystem engineering legacy effects. Although many authors recognize ecosystem engineering legacies, and some case studies quantify the effects of legacies, few general frameworks describe their causes and consequences across species or ecosystem types. Here, we synthesize evidence for ecosystem engineering legacies and describe how consideration of key traits of engineers improves understanding of which engineers are likely to leave persistent biogenic modifications. Our review demonstrates that engineering legacies are ubiquitous, with substantial effects on individuals, communities and ecosystem processes. Attributes that may promote the persistence of influential legacies relate to an engineer's traits, including its body size, life span and living strategy (individual, conspecific group or collection of multiple co-occurring species). Additional lines of inquiry, such as how the recipients respond (e.g. density or richness) or the mechanism of engineering (e.g. burrowing or structure building), should be included in future ecosystem engineering legacy research. Understanding patterns of these persistent effects of ecosystem engineers and evaluating the consequences of losing them is an important area of research needed for understanding long-term ecological responses to global change and biodiversity loss.Item Facilitation strength across environmental and beneficiary trait gradients in stream communities(Wiley, 2023-08) Tumolo, Benjamin B.; Albertson, Lindsey K.; Daniels, Melinda D.; Cross, Wyatt F.; Sklar, Leonard L.Ecosystem engineers modify habitats in ways that facilitate other community members by ameliorating harsh conditions. The strength of such facilitation is predicted to be influenced by both beneficiary traits and abiotic context. One key trait of animals that could control the strength of facilitation is beneficiary body size because it should determine how beneficiaries fit within and exploit stress ameliorating habitat modifications. However, few studies have measured how beneficiary body size relates to facilitation strength along environmental gradients. We examined how the strength of facilitation by net‐spinning caddisflies on invertebrate communities in streams varied along an elevation gradient and based on traits of the invertebrate beneficiaries. We measured whether use of silk retreats as habitat concentrated invertebrate density and biomass compared to surrounding rock surface habitat and whether the use of retreat habitat varied across body sizes of community members along the gradient. We found that retreats substantially concentrated the densities of a diversity of taxa including eight different Orders, and this effect was greatest at high elevations. Caddisfly retreats also concentrated invertebrate biomass more as elevation increased. Body size of invertebrates inhabiting retreats was lower than that of surrounding rock habitats at low elevation sites, however, body size between retreats and rocks converged at higher elevation sites. Additionally, the body size of invertebrates found in retreats varied within and across taxa. Specifically, caddisfly retreats functioned as a potential nursery for taxa with large maximal body sizes. However, the patterns of this taxon‐specific nursery effect were not influenced by elevation unlike the patterns observed based on community‐level body size. Collectively, our results indicate that invertebrates use retreats in earlier life stages or when they are smaller in body size independent of life stage. Furthermore, our analysis suggests that facilitation strength intensifies as elevation increases within stream invertebrate communities. Further consideration of how trait variation and environmental gradients interact to determine the strength and direction of biotic interactions will be important as species ranges and environmental conditions continue to shift.Item Nutrient enrichment intensifies the effects of warming on metabolic balance of stream ecosystems(Wiley, 2022-02) Cross, Wyatt F.; Hood, James M.; Benstead, Jonathan P.; Huryn, Alexander D.; Welter, Jill R.; Gíslason, Gísli M.; Ólafsson, Jón S.Climate warming and eutrophication are leading drivers of environmental change, and both are likely to alter the role of freshwaters in the global carbon cycle. Recent studies demonstrate that warming of streams can increase freshwater contributions of CO2 to the atmosphere, yet little is known about how such contributions are modulated by the identity or supply of limiting nutrients. We quantified responses of ecosystem metabolism and metabolic balance to whole-stream enrichments of either nitrogen or phosphorus across a 5°C range of ambient temperature. We show that nutrient enrichment drove large reductions in net ecosystem production, and interactions with temperature amplified these effects in warm N-enriched streams. Partitioning of autotrophic and heterotrophic respiration revealed that these responses were driven by increased respiration of microbial heterotrophs. Our study provides direct experimental evidence that warming-induced increases in CO2 emissions to the atmosphere are likely intensified in stream ecosystems subject to eutrophication.Item Uncovering process domains in large rivers: Patterns and potential drivers of benthic substrate heterogeneity in two North American riverscapes(2021-02) Scholl, Eric A.; Cross, Wyatt F.; Baxter, Colden V.; Guy, Christopher S.Identifying and understanding functional process domains (sensu Montgomery, 1999) in rivers is paramount for linking the physical habitat template to ecosystem structure and function. To date, efforts to do this have been rare, especially in large rivers, as they require appropriate tools for quantifying habitat heterogeneity with fine-scale resolution across broad spatial extents. In this study, we used side-scan sonar technology to map riverbed substrate at six sites in the Yellowstone and Missouri rivers. Substrate maps were then analyzed and visualized using geospatial analysis to relate fine-grained spatial substrate patterns to process domain structure. Our findings revealed two distinct nested domains of substrate patchiness, suggesting that different factors are responsible for shaping patterns of substrate at different scales. Although small-scale patchiness in substrate was likely driven by internal, or autogenic, physical processes, patterns at larger segment extents (>3 km) were often driven by abrupt transitions in habitat related to exogenous factors such as lateral erosion of talus, tributary inputs, and bank armoring. Additionally, we found that heterogeneity in benthic substrate increased with spatial extent at all of our study sites; however, this relationship was lower in the Missouri River, which is altered by impoundment. Our study represents one of the first efforts to relate benthic habitat heterogeneity to nested process domain structure in large riverscapes, and offers a unique perspective for linking landscape processes, geomorphological habitat heterogeneity, and biological structure and function in large rivers.Item Resource Supply Governs the Apparent Temperature Dependence of Animal Production in Stream Ecosystems(2020-10) Junker, James R.; Cross, Wyatt F.; Benstead, Jonathan P.; Huryn, Alexander D.; Hood, James M.; Nelson, Daniel; Gislason, Gisli M.; Olafsson, Jon S.Rising global temperatures are changing how energy and materials move through ecosystems, with potential consequences for the role of animals in these processes. We tested a central prediction of the metabolic scaling framework—the temperature independence of animal community production—using a series of geothermally heated streams and a comprehensive empirical analysis. We show that the apparent temperature sensitivity of animal production was consistent with theory for individuals (Epind = 0.64 vs. 0.65 eV), but strongly amplified relative to theoretical expectations for communities, both among (Epamong = 0.67 vs. 0 eV) and within (Epwithin = 1.52 vs. 0 eV) streams. After accounting for spatial and temporal variation in resources, we show that the apparent positive effect of temperature was driven by resource supply, providing strong empirical support for the temperature independence of invertebrate production and the necessary inclusion of resources in metabolic scaling efforts.Item Food web controls on mercury fluxes and fate in the Colorado River, Grand Canyon(2020-05) Walters, David M.; Cross, Wyatt F.; Kennedy, Theodore A.; Baxter, Colden V.; Hall, R. O. Jr.; Rosi, E. J.Mercury (Hg) biomagnification in aquatic food webs is a global concern; yet, the ways species traits and interactions mediate these fluxes remain poorly understood. Few pathways dominated Hg flux in the Colorado River despite large spatial differences in food web complexity, and fluxes were mediated by one functional trait, predation resistance. New Zealand mudsnails are predator resistant and a trophic dead end for Hg in food webs we studied. Fishes preferred blackflies, which accounted for 56 to 80% of Hg flux to fishes, even where blackflies were rare. Food web properties, i.e., match/mismatch between insect production and fish consumption, governed amounts of Hg retained in the river versus exported to land. An experimental flood redistributed Hg fluxes in the simplified tailwater food web, but not in complex downstream food webs. Recognizing that species traits, species interactions, and disturbance mediate contaminant exposure can improve risk management of linked aquatic-terrestrial ecosystems.Item Evaluating Irrigation Efficiency: Toward a Sustainable Water Future for Montana(The Montana University System Water Center, 2020-11) Lonsdale, Whitney R.; Cross, Wyatt F.; Dalby, Charles E.; Meloy, Sara E.; Schwend, Ann C.Water is our most valuable natural resource, and is used to support the demands of industry, agriculture, hydroelectric power generation, and municipalities. Water also sustains Montana’s booming recreation and tourism economy and maintains the diverse freshwater ecosystems that provide natural goods and services and promote human well-being. As our population continues to grow, and the collective demand for water increases, it is imperative that we carefully assess how our water is used, as well as how changes in water distribution, management, and governance are likely to influence its availability in the future. This is especially important in the context of a changing climate.