Browsing by Subject "functional traits"

Now showing 1 - 5 of 5

Butterfly Responses To Management Of Disturbance-Dependent Ecosystems In North America And Australia.
(2021-09) Leone, Julia
Fire and grazing are primary sources of natural disturbance in grasslands and savannas worldwide, but they are also shaped by human impacts and decision-making. Appropriate management is therefore an essential goal for biodiversity conservation in disturbance-dependent landscapes. The butterflies which inhabit these ecosystems are reliant on the disturbances necessary for grassland and savanna persistence. Regular fire, herbivory, and drought shape and maintain these ecosystems, keeping woody plants from dominating. How, then, do butterflies persist and respond to disturbance in their chosen habitats? What management regimes are required in human-altered landscapes to conserve grassland and savanna butterfly biodiversity? I examine butterfly responses to management of disturbance-dependent ecosystems in North American and Australian using both taxonomic and functional trait lenses. In Chapter 1, I assess the impacts of current fire and grazing management regimes on butterfly communities in Minnesota tallgrass prairie and compare butterfly and bee responses to management. In Chapter 2, I assess the impacts of these same fire and grazing regimes on monarch butterflies (Danaus plexippus) and their milkweed host plants in Minnesota tallgrass prairie. In Chapter 3, I examine butterfly and butterfly resource responses to fire regimes in Australian tropical savanna, and in Chapter 4, I demonstrate the utility of trait-based ecology to explain global and mechanistic patterns in butterfly responses to fire by presenting and comparing butterfly traits associated with fire regimes in U. S. temperate prairie and Australian tropical savanna. I present findings that butterfly and bee abundances in tallgrass prairie are significantly negatively correlated. Butterfly abundance, but not species richness, is nearly twice as high at tallgrass prairie sites managed with fire compared to grazing, and prairie-associated grass-feeding butterflies are more abundant at sites with higher plant species richness. I find that monarch butterflies are also more abundant at tallgrass prairie sites managed with fire than with grazing, and that this association is not related to milkweed or forb frequencies, which are similar between burned and grazed prairies. In Australian tropical savanna, I find that recent, early dry season burning promotes butterfly diversity and abundance by increasing the supply of nectar resources in tropical savanna fire treatments. In my evaluation of butterfly traits associated with fire, diapause strategy, host plant specificity, wingspan, voltinism, and flight period are all associated with at least one fire treatment, but trait associations are not shared across Australian tropical savanna and U.S. temperate prairie. In tallgrass prairie, land managers and conservation practitioners interested in promoting butterfly abundance and diversity may consider increasing plant species richness and maintaining fire in the landscape. Because species composition differs between sites managed with fire and grazing and among sites managed for different numbers of years, I suggest a variety of management strategies is required to support the entire suite of butterfly species. In tropical savanna, land managers and conservation practitioners can ensure some areas of recent, early-season fire are maintained and focus on additional actions that will promote floral resource abundance and diversity, which will benefit butterflies as well as many other animal taxa. Trait-based ecology methods can help us understand the role of traits such as diapause strategy, host plant specificity, wingspan, voltinism, and flight period in explaining general patterns in butterfly responses to fire. However, to inform good conservation and management, trait-based findings should be tied back to the local species and landscapes being managed. The second chapter of this dissertation is published in Frontiers in Ecology and Evolution (Leone et al. 2019) and the first chapter is currently under review with the Journal of Insect Conservation. As a reflection of the collaborative nature of the work I present, I will use the first-person plural voice “we” throughout the rest of this dissertation.
Data set used in publication titled: All the light we cannot see: Climate manipulations leave short and long-term imprints in spectral reflectance of trees
(2024-12-10) Stefanski, Artur; Butler, Ethan B.; Williams, Laura J.; Bermudez, Raimundo; Guzman, J. Antonio; Larson, Andrew; Townsend, Philip A.; Montgomery, Rebecca A.; Cavender-Bares, Jeannine; Reich, Peter B.; astefans@uwsp.edu; Stefanski, Artur; ASCEND
Anthropogenic climate change, particularly changes in temperature and precipitation, affects plants in multiple ways. Because plants respond dynamically to stress and acclimate to changes in growing conditions, diagnosing quantitative plant-environment relationships is a major challenge. One approach to this problem is to quantify leaf responses using spectral reflectance, which provides rapid, inexpensive, and nondestructive measurements that capture a wealth of information about genotype as well as phenotypic responses to the environment. However, it is unclear how warming, and drought affect spectra. To address this gap, we used an open-air field experiment that manipulates temperature and rainfall in 36 plots at two sites in the boreal-temperate ecotone of northern Minnesota, USA. We collected leaf spectral reflectance (400-2400 nm) at the peak of the growing season for three consecutive years on juveniles (two to six years old) of five tree species planted within the experiment. We hypothesized that these mid-season measurements of spectral reflectance capture a snapshot of the leaf phenotype encompassing a suite of physiological, structural, and biochemical responses to both long- and short-time scale environmental conditions. We show that the imprint of environmental conditions experienced by plants hours to weeks before spectral measurements is linked to regions in the spectrum associated with stress, namely the water absorption regions of the near-infrared and shortwave infrared. In contrast, the environmental conditions plants experience during leaf development leave lasting imprints on the spectral profiles of leaves, attributable to leaf structure and chemistry (e.g., pigment content and associated ratios). Our analyses show that after accounting for baseline species spectral differences, spectral responses to the environment do not differ among the species. This suggests that building a general framework for understanding forest responses to climate change through spectral metrics may be possible, likely having broader implications if the common responses among species detected here represent a widespread phenomenon. Consequently, these results demonstrate that examining the entire spectrum of leaf reflectance for environmental imprints in contrast to single features (e.g. indices and traits) improves inferences about plant-environment relationships, which is particularly important in times of unprecedented climate change.
Does relatedness matter? Phylogenetic density-dependent survival of seedlings in a tropical forest
(Ecological Society of America, 2014) Lebrija-Trejos, Edwin; Wright, S. Joseph; Hernandez, Andres; Reich, Peter B
A complex set of interactions among neighbors influences plant performance and community structure. Understanding their joint operation requires extensive information on species characteristics and individual performance. We evaluated first-year survival of 35 719 tropical forest seedlings of 222 species and 15 annual cohorts relative to the density of conspecific and heterospecific neighbors and the phylogenetic similarity of heterospecific neighbors. Neighbors were from two size classes, and size asymmetric interactions provided insight into likely mechanisms. Large heterospecific and conspecific neighbors reduced seedling survival equally, suggesting resource competition rather than host-specific enemies as a mechanism. In contrast, much stronger negative conspecific effects were associated with seedling neighbors capable of limited resource uptake, suggesting shared pests rather than competition as the mechanism. Survival improved, however, near phylogenetically similar heterospecific neighbors, suggesting habitat associations shared among closely related species affect spatial patterns of performance. Improved performance near phylogenetically similar neighbors is an emerging pattern in the handful of similar studies.
Shocks to the system: Community assembly of the oak savanna in a 40-year fire frequency experiment
(Ecological Society of America, 2012) Cavender-Bares, Jeannine; Reich, Peter B
Fire is a major force driving the evolution of plants and the structure and function of ecosystems globally. It thus likely operates as an important environmental filter that selects for species that have evolved to tolerate and depend on fire. Across a 40-year experimental fire gradient from frequently burned open savanna to unburned dense woodland in Minnesota, USA, we examined the relationships among community assembly, evolutionary history, and functional trait composition. Close relatives had similar abundance patterns across the fire gradient, providing evidence for phylogenetic conservatism in fire adaptation and highlighting the importance of shared ancestry in predicting species responses to fire. Phylogenetic beta diversity was greatest between the most extreme fire treatments across the gradient, indicating that species in the most contrasting fire regimes were most distantly related. Fire strongly influenced diversity, co-occurrence patterns, and leaf trait means and variances within communities. The most frequently burned communities had the highest species richness, exhibited the most resource-conservative leaf traits, and spanned the greatest number of phylogenetic lineages but harbored more close relatives within those lineages than other communities. In contrast, unburned communities had the lowest species diversity, the most acquisitive leaf traits, and the fewest phylogenetic lineages, but close relatives co-occurred less frequently. The largest difference in abundance between treatments occurred within the Rosales, Asteraceae, Vitaceae, and the Poaceae; woody Rosales were strongly selected for in unburned communities, while composites and grasses of the Poaceae were strongly selected for under frequent burning. A major climatic perturbation of consecutive hot, dry summers in the late 1980s prompted a significant shift in the functional and phylogenetic composition of communities. Greater than expected turnover in species composition occurred following the drought years, and then again during the subsequent five-year rebound period. Just after the drought year, turnover was greatest among recently diverged taxa, whereas during the rebound period turnover was greater among taxa that diverged deep in the phylogeny. The drought years also caused a short-term shift in functional traits, including declines in specific leaf area and leaf nitrogen content and an increase in leaf length. These results indicate that the phylogenetic and functional trait composition of communities are responsive both to fire gradients and to shocks to the system, such as climatic perturbation.
Species with greater seed mass are more tolerant of conspecific neighbours: a key driver of early survival and future abundances in a tropical forest
(Wiley, 2016) Lebrija‐Trejos, Edwin; Reich, Peter B; Hernández, Andres; Wright, S Joseph
Multiple niche‐based processes including conspecific negative density dependence (CNDD) determine plant regeneration and community structure. We ask how interspecific and intraspecific density‐dependent interactions relate to plant life histories and associated functional traits. Using hierarchical models, we analysed how such interactions affected first‐year survival of seedling recruits of 175 species in a tropical forest, and how species abundances and functional traits are related to interspecific variation in density‐dependent effects. Conspecific seedling neighbour effects prevailed over the effects of larger conspecific and all heterospecific neighbours. Tolerance of seedling CNDD enhanced recruit survival and subsequent abundance, all of which were greater among larger seeded, slow‐growing and well‐defended species. Niche differentiation along the growth–survival trade‐off and tolerance of seedling CNDD strongly correlated with regeneration success, with manifest consequences for community structure. The ability of larger seeded species to better tolerate CNDD suggests a novel mechanism for CNDD to contribute to seed‐size variation and promote species coexistence through a tolerance–fecundity trade‐off.

University Digital Conservancy

Browse by Subject

Browsing by Subject "functional traits"