ItemDeer browsing and light availability limit post oak (Quercus stellata) sapling growth and post-fire recovery in a xeric woodland(Elsevier, 2022-06-06) Cory, Beverly J.; Russell, F. LelandHistorically, oaks dominated the canopies of large regions of eastern North American forests, but at many sites current recruitment is insufficient to sustain oak dominance. Intense browsing by white-tailed deer (Odocoileus virginianus) and light limitation due to expansion by fire-intolerant tree species may cause poor oak recruitment. In a xeric woodland in Kansas USA, we used a deer exclusion experiment in natural canopy gaps to quantify effects of browsing and light availability on post oak (Quercus stellata) sapling performance, meaning growth and survival. Two weeks after beginning the experiment, a prescribed fire occurred that, due to natural burn heterogeneity, affected 29 of 31 experimental canopy gaps and top-killed 78.6% of experimental saplings. This allowed us to examine post-fire recovery in a sub-set of saplings. Our hypotheses were 1) ambient deer browsing intensity reduces post oak sapling performance, 2) sapling performance increases with gap size and light availability, 3) deer browsing effects on sapling performance vary with light availability, and 4) re-growth rate of saplings that were top-killed by fire is affected by light, deer browsing and the interaction of light and browsing. After five years, deer exclusion increased sapling growth in height and aboveground biomass. Sapling height growth was positively correlated with light. Deer effects on sapling performance generally were consistent across light environments. However, there was a weak pattern toward more negative effects of browsing in high light than in low light environments for saplings that re-sprouted post-fire. Protection from deer shortened the time required for saplings to re-attain their pre-fire height from five to three years. We conclude that deer browsing reduces post oak recruitment in canopy gaps in these xeric woodlands. Further, under current browsing intensity, fire return intervals less than five years will strongly limit oak recruitment. ItemAssociational effects, landscape context, and plant height affect white-tailed deer (Odocoileus virginianus) browse selectivity in oak woodlands(John Wiley & Sons, Ltd, 2022-07-01) Minette, Justin H.; Keoshkerian, Noah; Russell, F. LelandQuestions Large spatial variation in damage intensity is a pervasive, but poorly explained, feature of herbivore?plant interactions. To predict herbivore effects on plant communities, ecologists need greater understanding of the mechanisms and relative importance of processes driving variation in damage at the spatial scales of individual plant, plant community, and landscape. We ask: (1) what are the relative strengths of traits of individual plants versus landscape context in affecting white-tailed deer (Odocoileus virginianus) browsing on saplings in oak woodlands; and (2) is browsing intensity on post oak (Quercus stellata) influenced by associational effects related to density or frequency of more-selected or less-selected species? Location Dry oak-dominated woodlands, Kansas, USA. Methods We sampled deer browsing on saplings in three woodlands, each containing five transects, with 21 10-m2 plots per transect. Transects ran from woodland?grassland edges into woodlands. In each plot, we identified saplings to species, measured variables in individual-plant (height) and landscape contexts (distance from edge and proximity to deer trails), and quantified proportion of stems browsed per sapling. Results Browsing intensity varied greatly among the 18 tree species encountered. Browsing increased with sapling height and decreased with distance from woodland edges. The effect size of distance from edge was twice that of sapling height, although both effect sizes were small. Browsing on post oaks increased with local frequency of saplings of more-selected species. Conclusions Our comparison of individual-plant versus landscape context variables and our assessment of associational effects supports a substantial role for coarse-scale foraging decisions in explaining browsing damage. However, sapling species identity was most influential. Associational susceptibility of a less-selected species, post oak, near more-selected neighbors is consistent with a mobile herbivore choosing between patches. The pre-eminence of frequency of more-selected species in mediating associational susceptibility may reflect decreased handling time in pure patches and/or attempts to balance nutrients. ItemPost-dispersal factors influence recruitment patterns but do not override the importance of seed limitation in populations of a native thistle(Springer, 2020-04-22) Rand, Tatyana A.; West, Natalie M.; Russell, F. Leland; Louda, Svata M.Whether plant populations are limited by seed or microsite availability is a long-standing debate. However, since both can be important, increasing emphasis is placed on disentangling their relative importance and how they vary through space and time. Although uncommon, seed addition studies that include multiple levels of seed augmentation, and follow plants through to the adult stage, are critical to achieving this goal. Such data are also vital to understanding when biotic pressures, such as herbivory, influence plant abundance. In this study, we experimentally added seeds of a native thistle, Cirsium canescens, at four augmentation densities to plots at two long-term study sites and quantified densities of seedlings and reproductive adults over 9 years. Recruitment to both seedling and adult stages was strongly seed-limited at both sites; however, the relative strength of seed limitation decreased with plant age. Fitting alternative recruitment functions to our data indicated that post-dispersal mortality factors were important as well. Strong density-dependent mortality limited recruitment at one site, while density-independent limitation predominated at the other. Overall, our experimental seed addition demonstrates that the environment at these sites remains suitable for C. canescens survival to reproduction and that seed availability limits adult densities. The results thus provide support for the hypothesis that seed losses due to the invasive weevil, Rhinocyllus conicus, rather than shifting microsite conditions, are driving C. canescens population declines. Shifts in the importance of density-dependent recruitment limitation between sites highlights that alternate strategies may be necessary to recover plant populations at different locations. ItemModeling control methods to manage the sylvatic plague in black-tailed prairie dog towns(Rocky Mountain Mathematics Consortium, 2020-01-24) Elzinga, David C.; Stowe, Shelby R.; Russell, F. LelandBlack-tailed prairie dogs (Cynomys ludovicianus) are a keystone species of shortgrass and midgrass prairies, and they are essential for successful reintroduction efforts of endangered black-footed ferrets (Mustela nigripes). Sylvatic plague extirpates black-tailed prairie dog colonies. We present a model to determine optimal control methods to sustain a black-tailed prairie dog colony against the plague, including a recently developed vaccine. Our host submodel is a susceptible, exposed, infectious, vaccinated model, and our vector submodel is a susceptible, exposed, early-stage and late-stage infectious model with questing and on-host vectors. Both submodels are hybrid ordinary differential and difference equation models to reflect the phenology of black-tailed prairie dogs. Our model suggests vaccination efforts can substantially outperform previous control methods (e.g. reactive insecticidal dusting). Our model suggests that a vaccine that provides 18 months of immunity, administered annually, starting one year before an outbreak, can efficiently sustain a black-tailed prairie dog colony against the plague. Recommendations for resource managers The current sylvatic plague vaccine, administered annually, is insufficient to protect a black-tailed prairie dog colony against the sylvatic plague. Developing a vaccine with an immunity period of 18 months is critical for the persistence of a colony against the plague. While insecticidal dusting appears unable to assist in helping a black-tailed prairie dog colony recover from a plague outbreak, insecticidal dusting is still a critical prevention tool as plague transmission from the prairie dog flea is capable of causing a plague outbreak by itself. Black-tailed prairie dog colony recovery efforts appear sensitive to regularly administered culling. We recommend that colonies that are designated as part of the black-footed ferret recovery program be protected from population losses from recreational hunting and poisoning. ItemAre buffalograss (Buchloë dactyloides) cytotypes spatially and ecologically differentiated?(John Wiley and Sons, 2019-07-23) Hadle, Jacob J.; Russell, F. Leland; Beck, James B.Premise: Although autopolyploidy is common among dominant Great Plains grasses, the distribution of cytotypes within a given species is typically poorly understood. This study aims to establish the geographic distribution of cytotypes within buffalograss (Buchloë dactyloides) and to assess whether individual cytotypes have differing ecological tolerances. Methods: A range-wide set of 578 B. dactyloides individuals was obtained through field collecting and sampling from herbarium specimens. The cytotype of each sample was estimated by determining allele numbers at 13 simple sequence repeat loci, a strategy that was assessed by comparing estimated to known cytotype in 79 chromosome-counted samples. Ecological differentiation between the dominant tetraploid and hexaploid cytotypes was assessed with analyses of macroclimatic variables. Results: Simple sequence repeat variation accurately estimated cytotype in 89% of samples from which a chromosome count had been obtained. Applying this approach to samples of unknown ploidy established that diploids and pentaploids are rare, with the common tetraploid and hexaploid cytotypes generally occurring in sites to the north/west (tetraploid) or south/east (hexaploid) portions of the species range. Both MANOVA and niche modeling approaches identified significant but subtle differences in macroclimatic conditions at the set of locations occupied by these two dominant cytotypes. Conclusions: Incorporating chromosome count vouchers and cytotype-estimated herbarium records allowed us to perform the largest study of cytotype niche differentiation to date. Buffalograss cytotypes differ greatly in frequency, the common tetraploid and hexaploid cytotypes are non-randomly distributed, and these two cytotypes are subtly ecologically differentiated.