Eric Ribbens

Seedling Recruitment in Forests: Calibrating Models to Predict Patterns of Tree Seedling Dispersion

Recruitment, the addition of new individuals into a community, is an im- portant factor that can substantially affect community composition and dynamics. We present a method for calibrating spatial models of plant recruitment that does not require identifying the specific parent of each recruit. This method calibrates seedling recruitment functions by comparing tree seedling distributions with adult distributions via a maximum likelihood analysis. The models obtained from this method can then be used to predict the spatial distributions of seedlings from adult distributions. We calibrated recruitment functions for 10 tree species characteristic of transition oak- northern hardwood forests. Significant differences were found in recruit abundances and spatial distributions. Predicted seedling recruitment limitation for test stands varied sub- stantially between species, with little recruitment limitation for some species and strong recruitment limitation for others. Recruitment was limited due to low overall recruit production or to restricted recruit dispersion. When these seedling recruitment parameters were incorporated into a spatial, individual-based model of forest dynamics, called SOR- TIE, alterations of recruitment parameters produced substantial changes in species abun- dance, providing additional support for the potential importance of seedling recruitment processes in community structure and dynamics.

Spatial and temporal variation of seed rain in a tropical lowland wet forest

Patterns of seed rain were observed at five forest locations in recent treefall gaps and paired understory sites in a tropical wet forest in northeast Costa Rica. Seed rain was dominated by animal-dispersed species. Overall, significantly more wind-dispersed seeds arrived into treefall gaps than into forest understory. Contrary to expectations, understory sites received a greater seed rain than did gap sites during three of four sample periods over the course of one year. Considerable spatial heterogeneity, however, existed among forest locations, with some forest sites receiving up to three times more seed rain input than others. Results from this seed rain study generally matched those from an earlier study at this site in terms of seed rain volume and dominant plant families. Composition of seed rain was more similar among habitat types (i.e., gap, understory) than among forest locations (i.e., paired sites) suggesting that spatial foraging activity and habitat preference of seed dispersers result in non-random patterns of seed rain. If true, then such patterns have implications for evolution of fruit and seed characters that promote survival and establishment of seeds under certain environmental conditions.

Chromosome Counts of Opuntia (Cactaceae), Prickly Pear Cacti, in The Midwestern United States and Environmental Factors Restricting the Distribution of Opuntia Fragilis

Abstract: Opuntia fragilis, O. humifusa s.l., and O. macrorhiza s.l. are widely distributed prickly pear taxa that have been studied cytologically mostly in western North America, but upper Midwestern United States populations, which form most of the northeastern-most extent of their distributions, have not been analyzed previously. The wide-ranging and most northern of all cacti, O. fragilis, is relatively abundant, at least historically, in the upper Midwestern United States but does not occur further southeast than Jo Daviess County, Illinois, while O. humifusa s.l. is found throughout most of the eastern United States. This difference in distribution may indicate that environmental variables impede the establishment of O. fragilis in most of the eastern United States. We present the first chromosome counts of O. fragilis, O. humifusa s.l., and O. macrorhiza s.l. for 40 populations over part of their Midwestern range and employ habitat niche modeling using 19 environmental variables to extrapolate potential reasons why O. fragilis may not be found in the eastern United States.All twelve populations of O. fragilis analyzed were hexaploid, a finding consistent with previous reports, and adding further evidence for its vegetative dispersal from the southwestern United States, where the species likely originated. Populations of O. humifusa s.l. and O. macrorhiza s.l. were all tetraploid, indicating that the northeastern-most range of those taxa is occupied by polyploid derivatives of their southern diploid relatives. Results from niche modeling suggest suitable habitat for O. fragilis in the upper Midwest is strongly predicted for areas with seasonal fluctuations in temperature but annual precipitation homogeneity, variables that may present significant environmental barriers to the existence of the species in the eastern United States.

Opuntia fragilis: Taxonomy, Distribution, and Ecology

Abstract Opuntia fragilis is the smallest and most cold-hardy species of North American prickly pear, with an unusual distribution. This document is a review of its taxonomy, distribution, and ecology.

Using citizen science to bridge taxonomic discovery with education and outreach

Premise of the Study Biological collections are uniquely poised to inform the stewardship of life on Earth in a time of cataclysmic biodiversity loss. Efforts to fully leverage collections are impeded by a lack of trained taxonomists and a lack of interest and engagement by the public. We provide a model of a crowd‐sourced data collection project that produces quality taxonomic data sets and empowers citizen scientists through real contributions to science. Entitled MicroPlants, the project is a collaboration between taxonomists, citizen science experts, and teachers and students from universities and K–12. Methods We developed an online tool that allows citizen scientists to measure photographs of specimens of a hyper‐diverse group of liverworts from a biodiversity hotspot. Results Using the MicroPlants online tool, citizen scientists are generating high‐quality data, with preliminary analysis indicating non‐expert data can be comparable to expert data. Discussion More than 11,000 users from both the website and kiosk versions have contributed to the data set, which is demonstrably aiding taxonomists working toward establishing conservation priorities within this group. MicroPlants provides opportunities for public participation in authentic science research. The projects educational component helps move youth toward engaging in scientific thinking and has been adopted by several universities into curriculum for both biology and non‐biology majors.

Opuntia fragilis (Nuttall) Haworth in Illinois: Pad Dynamics and Sexual Reproduction

Abstract We studied the sole population of Opuntia fragilis in Illinois for four years, tracking plant and individual pad fates, and investigating flowering success. The population appears to be fairly stable in size from year to year. The fate of a given pad is strongly dependent upon the position of the pad within the plant; basal pads and transitional pads are likely to remain from year to year, while terminal pads experience substantially higher rates of death or fragmentation, and are much more likely to produce new growth and thus become transitional pads themselves. A fungal “black spot” disease, probably a result of winter damage, appears to negatively affect pad survival during some winters but not during other winters. While genetic diversity is not low, flowers do not produce viable seed, even when controlled cross-pollinations are performed, although they are visited by a variety of potential insect pollinators.

IMPERFECT FLOWERS OF OPUNTIA FRAGILIS IN KALADAR, ONTARIO

Abstract: The easternmost population of Opuntia fragilis occurs on a remote rock outcrop in Eastern Ontario. The Kaladar population is located almost 1,000 km away from its nearest neighbor and has recovered from previous vandalism. Recent visits to this site have discovered a plant producing flowers with viable pollen, but without carpels.

Scientific Uncertainty and Environmental Problem Solving.

Introduction: Scientific Uncertainty And Environmental Problem-Solving Methodological Rules For Four Classes Of Scientific Uncertainty Uncertainties In The Disposal Of High-Level Nuclear Waste Scientific Uncertainty As A Constraint To Environmental Problem-Solving: Large-Scale Ecosystems Uncertainty In Managing Ecosystems Sustainably Scientific Uncertainty And Environmental Policy: Four Pollution Case Studies Uncertainties Associated With Extrapolating From Toxicological Responses In Laboratory Systems To The Responses Of Natural Systems The Conservation Of Biodiversity: Scientific Uncertainty And The Burden Of Proof Resolving Uncertainty In Marine Fisheries Management: Can We? Scientific Uncertainties And Water Resources Management Scientific Uncertainty And The Environmental Impact Assessment Process In The United States Implications Of Scientific Uncertainty To Environmental Impact Assessment: The International Environment Environmental Problem-Solving In An Age Of Electronic Communications: Towards An Integrated Or Reductionist Model? The Implications Of Scientific Uncertainty To Environmental Law Science Assumptions And Misplaced Certainty In Natural Resources And Environmental Problem-Solving