02268nas a2200157 4500008004100000245014000041210006900181300001400250490000700264520169100271100002501962700002401987700002002011700002102031856005802052 2021 eng d00aTracking nutrients in space and time: Interactions between grazing lawns and drought drive abundances of tallgrass prairie grasshoppers0 aTracking nutrients in space and time Interactions between grazin a5413-54230 v113 a

1. We contrast the response of arthropod abundance and composition to bison grazing lawns during a drought and non-drought year, with an emphasis on acridid grasshoppers, an important grassland herbivore.
2. Grazing lawns are grassland areas where regular grazing by mammalian herbivores creates patches of short-statured, high nutrient vegetation. Grazing lawns are predictable microsites that modify microclimate, plant structure, community composition, and nutrient availability, with likely repercussions for arthropod communities.
3. One year of our study occurred during an extreme drought. Drought mimics some of the effects of mammalian grazers: decreasing above‐ground plant biomass while increasing plant foliar percentage nitrogen.
4. We sampled arthropods and nutrient availability on and nearby (“off”) 10 bison-grazed grazing lawns in a tallgrass prairie in NE Kansas. Total grasshopper abundance was higher on grazing lawns and the magnitude of this difference increased in the wetter year of 2019 compared to 2018, when drought led to high grass foliar nitrogen concentrations on and off grazing lawns. Mixed-feeding grasshopper abundances were consistently higher on grazing lawns while grass‐feeder and forb‐feeder abundances were higher on lawns only in 2019, the wetter year. In contrast, the abundance of other arthropods (e.g., Hemiptera, Hymenoptera, and Araneae) did not differ on and off lawns, but increased overall in 2019, relative to the drought of 2018.
5. Understanding these local scale patterns of abundances and community composition improves predictability of arthropod responses to ongoing habitat change.

1 aOzment, Katerina, A.1 aWelti, Ellen, A. R.1 aShaffer, Monica1 aKaspari, Michael uhttps://onlinelibrary.wiley.com/doi/10.1002/ece3.743502635nas a2200169 4500008004100000245010400041210007300145260001400218490000700232520203900239100002402278700002502302700002402327700002502351700002102376856006802397 2020 eng d00aBottom‐up when it is not top‐down: Predators and plants control biomass of grassland arthropods0 aBottom‐up when it is not top‐down Predators and plants control b c1286-12940 v893 a

1) We investigate where bottom‐up and top‐down control regulates ecological communities as a mechanism linking ecological gradients to the geography of consumer abundance and biomass. We use standardized surveys of 54 North American grasslands to test alternate hypotheses predicting 100‐fold shifts in the biomass of four common grassland arthropod taxa—Auchenorrhyncha, sucking herbivores, Acrididae, chewing herbivores, Tettigoniidae, omnivores, and Araneae, predators.

2) Bottom‐up models predict that consumer biomass tracks plant quantity (e.g. productivity and standing biomass) and quality (nutrient content) and that ectotherm access to food increases with temperature. Each of the focal trophic groups responded differently to these drivers: the biomass of sucking herbivores and omnivores increased with plant biomass; that of chewing herbivores tracked plant quality; and predator biomass did not depend on plant quality, plant quantity, or temperature.

3) The exploitation ecosystem hypothesis (EEH) is a top‐down hypothesis that predicts a shift from resource limitation of herbivores when plant production is low, to predator limitation when plant production is high. In grasslands where spider biomass was low, herbivore biomass increased with plant biomass, whereas bottom‐up structuring was not evident when spiders were abundant. Furthermore, neither predator biomass nor trophic position (via stable isotope analysis) increased with plant biomass, suggesting predators themselves are top‐down limited.

4) Stable isotope analysis revealed that trophic position of the chewing herbivore and omnivore increased significantly with plant biomass, suggesting these groups increased scavenging and meat consumption in grasslands with higher carbohydrate availability.

5) Taken together, our snapshot sampling documents gradients of food web structure across 54 grasslands, consistent with multiple hypotheses of bottom‐up and top‐down regulation.

1 aWelti, Ellen, A. R.1 aPrather, Rebecca, M.1 aSanders, Nathan, J.1 adeBeurs, Kirsten, M.1 aKaspari, Michael uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/1365-2656.1319100604nas a2200181 4500008004100000245010300041210007100144300001400215490000700229100001800236700002000254700001600274700001400290700001800304700001800322700002400340856005800364 2020 eng d00aMicronutrients enhance macronutrient effects in a meta‐analysis of grassland arthropod abundance0 aMicronutrients enhance macronutrient effects in a meta‐analysis  a2273-22880 v291 aPrather, R.M.1 aCastillioni, K.1 aKaspari, M.1 aSouza, L.1 aPrather, C.M.1 aReihart, R.W.1 aWelti, Ellen, A. R. uhttps://onlinelibrary.wiley.com/doi/10.1111/geb.1319600645nas a2200181 4500008004100000245010800041210007100149300001600220490000900236100002400245700002100269700002600290700002400316700002300340700002100363700002100384856005800405 2020 eng d00aSalty, mild, and low plant biomass grasslands increase top‐heaviness of invertebrate trophic pyramids0 aSalty mild and low plant biomass grasslands increase top‐heavine a1474 - 14850 v29581 aWelti, Ellen, A. R.1 aKuczynski, Lucie1 aMarske, Katharine, A.1 aSanders, Nathan, J.1 aBeurs, Kirsten, M.1 aKaspari, Michael1 aMadin, Elizabeth uhttps://onlinelibrary.wiley.com/doi/10.1111/geb.1311901641nas a2200157 4500008004100000245009400041210006900135300001100204490000900215520109300224100002401317700002401341700002301365700002101388856007401409 2019 eng d00aA distributed experiment demonstrates widespread sodium limitation in grassland food webs0 adistributed experiment demonstrates widespread sodium limitation ae026000 v71133 a

Sodium (Na) has a unique role in food webs as a nutrient primarily limiting for plant consumers, but not other trophic levels. Environmental Na levels vary with proximity to coasts, local geomorphology, climate, and with anthropogenic inputs (e.g., road salt). We tested two key predictions across 54 grasslands in North America: Na shortfall commonly limits herbivore abundance, and the magnitude of this limitation varies inversely with environmental Na supplies. We tested them with a distributed pulse experiment and evaluated the relative importance of Na limitation to other classic drivers of climate, macronutrient levels, and plant productivity. Herbivore abundance increased by 45% with Na addition. Moreover, the magnitude of increase on Na addition plots decreased with increasing levels of plant Na, indicating Na satiation at sites with high Na concentrations in plant tissue. Our results demonstrate that invertebrate primary consumers are often Na limited and track local Na availability, with implications for the geography of invertebrate abundance and herbivory.

1 aWelti, Ellen, A. R.1 aSanders, Nathan, J.1 aBeurs, Kirsten, M.1 aKaspari, Michael uhttps://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.260002170nas a2200181 4500008004100000245009200041210007100133300001400204490000700218520157000225100002401795700001201819700002001831700001801851700002001869700001901889856008001908 2019 eng d00aFire, grazing and climate shape plant–grasshopper interactions in a tallgrass prairie0 aFire grazing and climate shape plant–grasshopper interactions in a735 - 7450 v333 a

1. Species interactions are integral to ecological community function, and the      structure of species interactions has repercussions for the consequences of species extinctions. Few studies  have examined the role of environmental factors in controlling species interaction networks across time.
2. We examined variation in plant–grasshopper network structural properties in response to three major grassland drivers: periodic fire, ungulate grazing and climate.
3. We sequenced a plant barcoding gene from extracted grasshopper gut contents to characterize diets of 26 grasshopper species. Resulting grasshopper species’ diets were combined with long‐term plant and grasshopper surveys to assemble plant–grasshopper networks across 13–19 years for six watersheds subjected to varying fire and grazing treatments.
4. Network modularity, generality and predicted grasshopper community robustness to plant species loss all increased in grazed watersheds. Temperature decreased predicted grasshopper community robustness to plant species loss.
5. Grasshopper communities were found to be vulnerable to climatic warming due to host plant loss. However, intermediate disturbance from ungulate grazers may maintain grasshopper diversity and buffer community robustness to species loss. Our results suggest that climate and disturbance shape the structure of ecological interaction networks and thus have many indirect effects on species persistence though direct effects on interaction partners.

1 aWelti, Ellen, A. R.1 aFan, Q.1 aTetreault, H.M.1 aUngerer, M.C.1 aBlair, John, M.1 aJoern, Anthony uhttps://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2435.1327202299nas a2200193 4500008004100000245011700041210007100158300001200229490000800241520165500249653002201904653001601926653002401942653001701966653001601983100002401999700001902023856006302042 2018 eng d00aFire and grazing modulate the structure and resistance of plant–floral visitor networks in a tallgrass prairie0 aFire and grazing modulate the structure and resistance of plant– a517-5280 v1863 a

Significant loss of pollinator taxa and their interactions with flowering plants has resulted in growing reductions to pollination services globally. Ecological network analysis is a useful tool for evaluating factors that alter the interaction structure and resistance of systems to species loss, but is rarely applied across multiple empirical networks sampled within the same study. The non-random arrangement of species interactions within a community, or “network structure” such as nested or modular organization, is predicted to prevent extinction cascades in ecological networks. How ecological gradients such as disturbance regimes shape network structural properties remains poorly understood despite significant efforts to quantify interaction structure in natural systems. Here, we examine changes in the structure of plant–floral visitor networks in a tallgrass prairie using a decadal and landscape-scale experiment that manipulates prescribed burn frequency and ungulate grazing, resulting in different grassland states. Plant and floral visitor communities and accompanying network structure were impacted by grassland fire and grazing regimes. The presence of grazers increased flowering plant species richness, network floral visitor species richness, and decreased network nestedness. Fire frequency affected flowering plant and floral visitor community composition; community composition impacted network specialization and modularity. Grassland state resulting from fire-grazing interactions has important implications for the resistance of flowering plant and floral visitor communities to species loss.

10aCommunity ecology10adisturbance10aEcological networks10aInteractions10aPollinators1 aWelti, Ellen, A. R.1 aJoern, Anthony uhttp://link.springer.com/article/10.1007/s00442-017-4019-902567nas a2200217 4500008004100000245005900041210005900100260004300159490002100202520191100223653002302134653001202157653001302169653001402182653001502196653002202211100002402233700001902257700002002276856005302296 2017 eng d00aEcological networks of grassland plants and arthropods0 aEcological networks of grassland plants and arthropods aManhattan, KSbKansas State University0 vPhD Dissertation3 a

Ecological communities are comprised both of species and their interactions. The importance of species interactions is embraced by ecological network analysis, a framework used to identify non-random patterns in species interactions, and the consequences of these patterns for maintaining species diversity. Here, I investigated environmental drivers of the structure of plant-pollinator and plant-herbivore networks. Specifically, I asked: (1) Do global-scale climate gradients shape mutualistic and antagonistic networks? (2) At a landscape scale (within a 3,487 ha research site), how do contrasting regimes of major grassland disturbances - fire frequency and grazing by bison (Bison bison) - shape plant-pollinator network structure? (3) How do fire and grazing affect plant-grasshopper network structure? And, (4) What is the role of plant species diversity in determining plant-herbivore network structure? At the global scale, variability in temperature was the key climatic factor regulating both antagonistic and mutualistic network structural properties. At the landscape scale, fire and grazing had major consequences for plant-pollinator and plant-herbivore communities. In particular, bison grazing increased network complexity and resistance to species loss for both plant-pollinator and plant-herbivore systems. Results from an experimental grassland restoration that manipulated plant diversity suggest that plant diversity directly affects plant-herbivore structure and increases network stability. Collectively, these results suggest that environmental gradients and plant species diversity regulate the network structure of ecological communities. Determining how the structure of ecological interactions change with environmental conditions and species diversity improves our ability to identify vulnerable communities, and to predict responses of biodiversity to global change.

10aEcological network10aecology10aFood web10aHerbivore10aPollinator10atallgrass prairie1 aWelti, Ellen, A. R.1 aJoern, Anthony1 aBlair, John, M. uhttp://krex.k-state.edu/dspace/handle/2097/35284