Archbold Biological Station, Biennial Report 1997-1998

Members of the Plant Ecology Lab in spring 1997: L-R; Pedro Quintana-Ascencio, Michael Kelrick, Kurt Reinhart, Rebecca Yahr, Christina Casado, Eric Menges, Satya Maliakal, Graham Walker, Dorothy Mundell; photo by Nancy Deyrup


       Accomplishments 1997-98
  • Published 9 peer-reviewed papers and book chapters in such journals as Conservation Biology, Journal of Ecology, Ecological Applications, and American Journal of Botany.
  • Worked under 8 extramural grants involving demography, genetics, fire management, and conservation of Florida scrub plants.
  • Awarded a 5-year grant from National Science Foundation to continue data collection and population viability analyses on Florida scrub plants.
  • Continued collection of long-term demographic data on Florida scrub plants, now in the 11th year for 3 species.
  • Facilitated many research projects, including 5 Ph.D. projects from 5 universities.

A conceptual model for vegetation dynamics in an upland Florida landscape. Arrows indicate hypothesized transitions under various disturbance regimes: FF = frequent fires (110 yr), MF = moderately frequent fires (520 yr), IF = infrequent fires (15100 yr), NF = no fires within 100 yr, WF = winter fires, PR = pine removal, F = fire reintroduction (Ecol. Appl. 8:935946, 1998).

Plant Ecology Research &
Plant Ecology: New Approaches and New Species

Project Director: Eric S. Menges
Research Assistants (Full Time): Christina M. Casado, Carl W. Weekley, Rebecca Yahr
Research Assistants (Part Time): Michael N. Gushee, Christine V. Hawkes, Richard J. Lavoy, Dorothy E. Mundell, William R. Smith, Donald M. Stillwaugh Jr., Helen A. Violi, Diane Willis
Graduate Intern: Pedro F. Quintana-Ascencio
Undergraduate Interns: Matthew S. Finer, Erica M. Goss, Phillip E. Higuera, Molly E. Hunter, Satya K. Maliakal, Abigail L. McCarthy, Patrick J. McIntyre, Kurt O. Reinhart
Volunteers: Dorothy E. Mundell, Graham Walker; Partners for Plants volunteers--Vickie Denton, Helen Goodhue, Frances Hufty, Sally Robinson, Mary Frances Wagley, Robbie Wurts
Outside Collaborators: Dawn M. Berry, Florida Game and Fresh Water Fish Commission; Rebecca W. Dolan, Butler University; Margaret E.K. Evans, University of Arizona; Daniel Gagnon, University of Quebec at Montreal; Doria R. Gordon, The Nature Conservancy; Michael L. Kelrick, Truman State University; Peter L. Marks, Cornell University; Pedro F. Quintana-Ascencio, ECOSUR, Mexico; Tammera Race, Bok Tower Gardens; Richard B. Root, Cornell University; Joan L. Walker, Clemson University; Rebecca Yahr, Duke University
Visiting Researchers: Christine V. Hawkes, University of Pennsylvania; Olle Pellmyr, Vanderbilt University; Sonja Scheffer U.S. Department of Agriculture; Gayle vande Kerckhove, University of Florida

[ Biennial Contents | Biennial 95-96]

Highlights of plant ecology research during 1997-98 include the conclusion of several important projects (a major, integrative rangewide study of genetic variation in seven Florida scrub endemic plant species; the first population viability analysis for a scrub plant), integrative summaries (two reviews of scrub ecology, a review of population viability analysis in plants), complementary projects on the life history of several scrub plants, and the initiation of projects on new species and new management strategies (see below). Long-term funding was secured from the National Science Foundation to build, analyze, model, and expand decade-long databases on the demography of scrub plants.

     Genetic Patterns in Scrub Plants. A multi-year study on the genetics, ecology, and preserve design of seven Florida scrub endemic plants continued in 1997–98, with one of the highlights being an 11-chapter report to The Nature Conservancy (see Doria Gordon, which helped fund the project. This study combined detailed experiments on life history with a rangewide survey of genetic variation (see maps, page 11 and page 29 [d] ). The species were found to be dependent upon pollinators, but five of seven can produce seeds from within-plant pollinations. Gene flow via pollinators varies but that due to seed dispersal is very limited. Isozyme (genetic) variation is rather low, but varies widely across species. Within species, larger populations in larger soil patches have more genetic variation for three species, but results vary depending on the measure of genetic variation. Comparing species, long-lived outcrossing species with stable demography and strong pollen flow had greater genetic variation. Genetic data were used to identify populations that are especially significant for conservation. The good news is that the proposed reserve system protects over 85% of polymorphic alleles detected by the study.

     Standing out among the seven species was Hypericum cumulicola, which contains an extraordinary proportion of its limited genetic variation among (rather than within) populations. Genetic differences among populations also occur at smaller scales, such as within Archbold. Genetic patterns of transplants, native plants, and their offspring were used as evidence for limited gene flow and metapopulation dynamics in a collaborative paper published in 1998 in Journal of Ecology by Pedre Quintana-Ascencio, Rebecca Dolan, and Eric Menges. [ Quintana-Ascencio, P.F., R.W. Dolan, and E.S. Menges. 1998. Hypericum cumulicola demography in unoccupied and occupied Florida scrub patches with different time-since-fire. J. Ecol. 86:640-651. ]

     Population Viability Analyses and Long-Term Research. Population viability analyses (PVA) project the future of populations based on demographic and other data, and are often used to evaluate alternative management strategies for endangered species. In 1997, Quintana-Ascencio completed the first PVA for a Florida scrub plant, using a modeling approach that incorporated stochastic variation in demographic parameters and the fire/recovery cycle of Florida scrub. Populations of Hypericum cumulicola are viable when frequently-burned but can often persist as dormant seed banks for several decades after aboveground populations have perished between fires. Menges conducted a literature review of plant PVAs for talks in Sweden and Italy, finding that plant PVAs differed in important ways from PVAs constructed for animals, and finding disturbing limitations in the duration of studies and in the numbers of populations considered. He has been invited to write a review of plant PVAs for Trends in Ecology and Evolution. Menges and Dolan also published a PVA for a midwestern prairie plant in Journal of Ecology, finding that fire management was the most important factor in ensuring population viability for this species.

     Further PVAs are planned for scrub species with long-term demographic data, ranging from perennial shrubs to an annual herb. The long-term datasets collected on a number of scrub species, up to 11 years in length from multiple populations (see Table 1), provide a rich source of data on temporal variation in demography which is key for PVAs. The National Science Foundation’s Program, Long-Term Research in Environmental Biology, has awarded funding for 5 years, beginning in 1999, for additional data collection, population viability modeling, and explicit spatial analyses, both at within-patch and landscape scales.

     Integration of Scrub Ecology. The Plant Ecology Lab has been the home of myriad projects conducted by staff, visiting scientists, and graduate students during the last decade. Integration of these data provides efficient communication of results and can stimulate new projects. Two integrative reviews were published in 1998. Menges and Christine Hawkes reviewed the interactive role of fire and microhabitat on Florida scrub plants in an article published in Ecological Applications. They emphasized changes that occur at landscape scales, local patches, and microsites. Alterations in fire regimes cause complex feedbacks at both scales and can then alter future fire effects (see fig., page 10). A more general review of scrub biology by Menges includes summaries of demographic and metapopulation research on a variety of Florida scrub organisms.

     Complementary Approaches: Dicerandra frutescens. Another type of integrative science occurs when different studies on the same organism combine to provide additional insights. This is illustrated by various projects on the endangered scrub mint, Dicerandra frutescens. The long-term demographic work suggests that fire-suppression is a threat to this species, and more recent publications on its microhabitat show that structural habitat changes occurring between fires cause a decline. Genetic analyses reveal extremely narrow variation, perhaps due to periodic population crashes. However, little genetic difference exists among various populations, suggesting that gene flow has connected these patches in the past. Pollination studies recently published by Menges and Mark Deyrup suggest that pollination doesn’t limit fruit production, but it may affect the fitness of subsequent seedlings. Outbreeding depression, studied by intern Abigail McCarthy, has the potential to reduce the fitness of seedlings resulting from long-distance crosses. While gene flow by pollen may be substantial, intern Matthew Finer showed that seed dispersal is rare much beyond the parental canopy. Consequently, loss of dormant seed banks due to fire suppression could be very important to population persistence. Recent experimental fires in long-unburned populations, combined with a 3-year field seed bank experiment conducted in collaboration with Michael Kelrick (Truman State Univ.), will help evaluate the longevity and resilience of dormant seed banks in D. frutescens.

Partners for Plants volunteers, including Frances Hufty of Archbold Expeditions (seated in the vehicle) assemble at Carter Creek Preserve, April 1998, with Rebecca Yahr (standing left) and Eric Menges (far right) of the Plant Ecology Lab; photo by Eric Menges.

Eric Menges and Daniel Gagnon install a soil moisture probe, photo by Nancy Deyrup.

Plant Ecology: New Approaches and New Species   
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Conservation Biology. Crises in conservation and management need prompt attention from researchers in conservation biology.  During 1997–98, the Plant Ecology Lab initiated new projects to gather important data on two critical species and on some alternative management strategies. With help from Partners for Plants volunteers (see photo, this page), we initiated studies of Crotalaria avonensis at its largest remaining site, the Carter Creek Preserve, managed by the Florida Game and Fresh Water Fish Commission (FGFWFC). Initial data suggest that this plant can thrive in a variety of microsites, but that limited fecundity, irregular growth patterns, and herbivory may be factors that could affect its demography. Ongoing research on the extremely endangered shrub, Ziziphus celata, now part of the Plant Lab program, has been conducted by Carl Weekley with the collaboration of Tammera Race (Bok Tower Gardens). Recent breeding systems experiments show that only certain crosses among particular genotypes and populations result in fruit and seed production. Such information is of practical use in planned introductions of this species to new protected sites on the Lake Wales Ridge.

     Alternatives to Fire Management. Although fire management is widely viewed as necessary for management of Florida scrub and adjacent vegetation in the Florida landscape, it is often difficult to apply for logistical and political reasons. However, the effects of additional or alternative management practices are poorly known. The Plant Lab started two studies to examine mechanical treatments and pre-treatments and their effect on scrub communities. Both involve close collaboration with stage agencies. At Lake Wales Ridge State Forest, we are examining sand pine scrub response to logging and fire in cooperation with two state agencies. Extensive before-treatment sampling has been concluded and treatments are slated for 1999. Similarly, 1999 treatments following extensive before-treatment data from three sites are the exciting next step in a project on mowing and fire conducted in collaboration with the FGFWFC, and supported by a grant from the U.S. Fish and Wildlife Service.

     Differences between fire treatments, with and without mechanical pretreatments may be due to differences in fire intensity and its heterogeneity over space. We are planning comparative studies in fire intensity and heterogeneity in South Carolina sandhill vegetation and Florida scrub vegetation, in concert with Joan Walker (Clemson Univ.).

     Water and Nutrient Dynamics. While data from Archbold provide many interesting examples of spatial patterning and habitat specialization among Florida scrub plants, the mechanisms for these phenomena are poorly known. For example, it is widely viewed that plant communities may be distributed in the landscape in response to water availability, nutrient levels, fire, or combinations of these three. However, little work on water or nutrients has been done. In 1998 Daniel Gagnon has brought new technologies and ideas to bear. Frequency domain reflectometry measures soil water outside 78 permanent tubes in various locations at Archbold (see photo, this page). The role of crytobiotic soil crusts in providing nitrogen to the low-nutrient scrub soils is one of the questions in Christine Hawkes’ ongoing Ph.D. investigations.


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Archbold Biological Station, 4 April 2000
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