Bruce M. Pavlik

Marine beach and dune plant communities

The biology of beach and dune plants along North American shores has received scientific attention for nearly 100 years. Cowles founded his dynamic view of plant communities on examples of succession in coastal dunes (albeit Great Lakes dunes; Cowles, 1891). Within 20 years, Harshberger (1900,1902, 1903, 1908, 1914) had contributed many field observations from Atlantic and Gulf coasts and Cooper (1936) had begun a long-term study of Pacific coast strand plant distribution.

Assessing limitations on the growth of endangered plant populations, II. Seed production and seed bank dynamics of Erysimum capitatum ssp. Angustatum and Oenothera deltoides ssp. Howellii

Abstract Herein we extend a related study of Erysimum capitatum ssp. angustatum (= ECA) and Oenothera deltoides ssp. howellii (= ODH), two highly endangered plants, by examining seed production and seed bank dynamics at Antioch Dunes National Wildlife Refuge in central California (USA). ECA and ODH were found to produce large numbers of seeds at the refuge, comparing favorably with closely related but non-endangered taxa. Extrinsic limits on seed production, such as the availability of effective pollinators, were found to important rather than intrinsic (i.e. genetic) limits. More than half of the ovules initiated by ODH during the two-year study period failed to become seeds. These ovules were contained by ovaries that failed to develop because effective pollinators (e.g. hawkmoths) were not available to carry pollen between flowers of different individuals in this outcrossing taxon. Management of the ODH population, therefore, will require special efforts to protect local populations of effective pollinators in order to minimize the pollination limitation in the future. Pollination and could also limit seed production in ECA, but only when the plant population was small and competition for pollinators from other species intense. Pre-dispersal insect predation was also more important when the ECA population was small. Management of the ECA population to maximize seed production, therefore, requires increasing population size by maximizing germination, seedling establishment, and growth in years of poor rainfall. Controlling competition from introduced annual grasses, particularly for moisture, is most important in this regard. The seed banks of ECA and ODH were large compared to the number of established plants, and exhibited typical seasonal patterns of depletion and replenishment. A minimum residual bank of viable ECA seeds remained during the entire year, suggesting there was overlap of generations and a buffer against catastrophic events that affect established plants. ODH, however, had a smaller residual bank and was, therefore, less well-buffered against the erosion of genetic variation and catastrophic events that affect the adult population. The long-term status and dynamics of the ECA and ODH seed banks will depend on management that reduces the seed density of introduced annual grasses in the refuge seed bank.

The Role of Botanic Gardens in the Science and Practice of Ecological Restoration

Many of the skills and resources associated with botanic gardens and arboreta, including plant taxonomy, horticulture, and seed bank management, are fundamental to ecological restoration efforts, yet few of the worlds botanic gardens are involved in the science or practice of restoration. Thus, we examined the potential role of botanic gardens in these emerging fields. We believe a reorientation of certain existing institutional strengths, such as plant-based research and knowledge transfer, would enable many more botanic gardens worldwide to provide effective science-based support to restoration efforts. We recommend botanic gardens widen research to include ecosystems as well as species, increase involvement in practical restoration projects and training practitioners, and serve as information hubs for data archiving and exchange.

Assessing limitations on the growth of endangered plant populations, I. Experimental demography of Erysimum capitatum ssp. Angustatum and Oenothera deltoides ssp. Howellii

Abstract This study was designed to identify factors that limit the growth of populations of two federally-listed endangered plants— Erysimum capitatum ssp. Angustatum (= ECA) and Oenothera deltoides ssp. howellii (= ODH)—both endemic to Antioch Dunes National Wildlife Refuge (Contra Costa County, California, USA). Herein we report on the relevant aspects of experimental seedling demography in situ . Seeds were precisely sown into areas that differed with respect to substrate (dune, clay and clay that had been mechanically disked) and exposure (shaded and exposed dune areas). ECA was very dependent on sandy dune substrate for high germination and survivorship, as well as the vigorous growth of established plants. Mortality was linked to exposure and substrate drought, rather than herbivory or soil nutrient deficiency. Disking the clay substrate promoted germination but not survivorship or plant growth and could not, therefore, be used to improve the availability of high-quality habitat for ECA at the refuge. In contrast, substrate characteristics and exposure were not as critical to ODH because individuals became established and reproductive on disked clay as well as on exposed dune sand. Mortality of ODH was linked to insect herbivory on the dune sand and moisture or nutrient availability on the disked clay and clay substrates. Therefore, in order to increase the size and areal extent of these populations at Antioch Dunes, management should include (1) mechanical disking of clay substrate to improve habitat availability for ODH; (2) removal of non-native vegetation to provide more unstabilized, shaded dune substrate for ECA and to reduce insect herbivory on ODH seedlings; (3) creation of new sand-dune habitat for both taxa by importing riverine sand; and 94) re-establishment of ODH and ECA populations in habitat restored by disking or weeding or into habitat created by sand importation.

The reproductive attributes of an endangered plant as compared to a weedy congener

Abstract Comparisons of reproductive attributes related to fitness can help explain differences in the distribution and abundance of rare and common plant species. This study was conducted to characterize a rare taxon (Amsinckia grandiflora (Gray) Kleeb, ex Greene) and its widespread congener (Amsinckia menziesii (Lehm.) Nels. and Macbr. var. intermedia (Fischer and Meyer) Ganders) with respect to major fitness components and variables. These included: (1) inflorescence output (number of inflorescences per plant); (2) floral cache (number of flowers per inflorescence); (3) floral seed cache (number of seeds per flower); (4) seed weight (per 100 seeds); (5) seed output (total number of seeds per plant); and (6) seed yield (total seed weight per plant). All significant correlations among these fitness components were positive. Inflorescence output was the most important variable determining seed output and seed yield for both the rare and common species, whereas seed weight had no significant direct effect on seed output or seed yield. The rare species. A. grandiflora, was especially sensitive to floral seed cache while the common species, A. menziesii var. intermedia, was especially sensitive to inflorescence output. These results are discussed with respect to the evolution of weediness and the conservation of rarities in the native California flora.

Demographic monitoring of endemic sand dune plants, Eureka Valley, California

Abstract A two-year study of the perennial endemics Swallenia alexandrae, Oenothera avita ssp. eurekensis and Astragalus lentiginosus var. micans was conducted at Eureka Dunes, Inyo County, California. Based on analyses of survivorship it was concluded that the populations are at least stable (even short-lived Oenothera cohorts survive long enough to reproduce) or growing (the number of established Swallenia and Astragalus plants doubled during the study). The high mortality and short life span of Oenothera and Astragalus populations were offset by copious seed production, long-lived seeds, low to moderate seed predation, and frequent establishment. The low and variable seed production, high seed predation, and infrequent establishment of Swallenia populations were counterbalanced by a low mortality of recruits and established plants, a long reproductive life, and long-lived seeds. It is concluded that the factors endangering these endemic populations are mostly extrinsic to the plant population (e.g. human disturbance, pollinator availability, climatic fluctuation) and that no additional manipulations of the populations are necessary.

Reproductive ecology and the persistence of an endangered plant

Amsinckia grandiflora (large-flowered fiddleneck)is an extremely rare California annual wildflower, known only from threepopulations. We conducted field and greenhouse experiments to compare the rareheterostyle with a cryptic self-incompatibility system (A.grandiflora) to a common, self-compatible, homostylous, sympatriccongener (A. tessellata). Inter-species comparisons ofadult plants suggested that in the greenhouse, A.grandiflora balances low floral seed set (seeds per flower) withincreased floral output (flowers/plant) and a greater number of flowers perinflorescence. Seed set from active self-, intra- and inter-morph pollinationswas high in A. grandiflora, indicating that the crypticself-incompatibility system does not prevent seed set in the species. In thefield, A. grandiflora floral output was only slightlygreater than for A. tessellata, and did not fully balance lowerfloral seed set. Amsinckia tessellata average seed weightwas lower than that of A. grandiflora, which, along with the lowernumber of flowers produced, indicated lower maternal investment per nutlet thanfor A. grandiflora. Under conditions of unlimited resources, itappears that A. grandiflora fitness is not intrinsicallylimited when compared to its weedy relative A. tessellata.The differences in nutlet output between A. grandiflora andA. tessellata under field conditions are more likely due todifferential responses to extrinsic factors such as competition and pollinatoravailability.

Seasonal Patterns of Growth, Water Potential and Gas Exchange of Red and White Fir Saplings across a Montane Ecotone

-Saplings of Abies magnifica (red fir) and A. concolor (white fir) were measured for leaf gas exchange characteristics, xylem water potential and growth during 1 growing season. Eight saplings of each species, 22-34 yr old, were located along a 170-m elevational transect. Although white and red fir replace each other as dominants along the transect, ecophysiological traits of saplings were statistically identical. Net photosynthesis rates, leaf conductance to water vapor, water-use efficiency, xylem water potential and patterns of interactions or change through time were all similar for the two species. Height growth of white fir began earlier, peaked earlier and was greater than that of red fir. Diameter growth of white fir was also greater. Differences and similarities in physiological responses between the species were unaffected by position along the transect. We suggest that environmental factors which favor red fir at high elevation and white fir at low elevation are either not integrated by gas exchange behavior, not operative in summer, not differentially important this particular drought year or not differentially effective at this stage of the life cycle.

Management plan for an alkali sink and its endangered plantCordylanthus palmatus

Cordylanthus palmatus is a hemiparasitic annual of the family Scrophulareacae. It is on both the federal and state lists of endangered species. Only four widely separated populations remain, all of them in alkali sinks, where the plant thrives in saline-sodic soils. The largest population is at Springtown, Alameda County, California. This article reports on efforts to develop a management plan for both the plant and the alkali sink ecosystem. The plan is based on: (1) characterization of hydrology, soils and geomorphology of the site; (2) characterization of the land use impacts to the site; (3) analysis of plant distribution in relation to gradients of elevation and soil chemistry; (4) studies on water potential and water stress inCordylanthus palmatus and associated species. On the basis of this plan, both the State of California and private groups are cooperating to create, restore, and manage a preserve in the Springtown Alkali Sink.

The Role of Botanic Gardens in the Science and Practice of Ecological Restoration: Role of Botanic Gardens in Restoration

Many of the skills and resources associated with botanic gardens and arboreta, including plant taxonomy, horticulture, and seed bank management, are fundamental to ecological restoration efforts, yet few of the worlds botanic gardens are involved in the science or practice of restoration. Thus, we examined the potential role of botanic gardens in these emerging fields. We believe a reorientation of certain existing institutional strengths, such as plant-based research and knowledge transfer, would enable many more botanic gardens worldwide to provide effective science-based support to restoration efforts. We recommend botanic gardens widen research to include ecosystems as well as species, increase involvement in practical restoration projects and training practitioners, and serve as information hubs for data archiving and exchange.