What determines the number and size of the seeds produced by a plant? How often should it reproduce them? How often should a plant produce them? Why and how are seeds dispersed, and what are the implications for the diversity and composition of vegetation? These are just some of the questions tackled in this wide-ranging review of the role of seeds in the ecology of plants. The authors bring together information on the ecological aspects of seed biology, starting with a consideration of reproductive strategies in seed plants and progressing through the life cycle, covering seed maturation, dispersal, storage in the soil, dormancy, germination, seedling establishment, and regeneration in the field. The text encompasses a wide range of concepts of general relevance to plant ecology, reflecting the central role that the study of seed ecology has played in elucidating many fundamental aspects of plant community function.

The ecology of seeds

The Ecology of Seeds: Seedling establishment

We evaluated effects of rooting by feral hogs (Sus scrofa) on total emergent vegetation cover, vegetation species richness, and diversity of plant-defined microhabitat types in an impounded floodplain marsh in central Florida. Data were collected in 6 split-plots (rooted and control) over 10 post-rooting, monthly sampling periods. Hog rooting led to reduced plant cover in broadleaf marsh habitats and to significantly higher microhabitat diversity and species richness. Although feral hogs can have detrimental effects on native biota and community structure, our data suggest that hog rooting is a disturbance that can enhance plant species richness and associated microhabitat diversity in wetland habitats.

Effects of rooting by feral hogs Sus scrofa L. on the structure of a floodplain vegetation assemblage

Effects of Litter, Soil Surface Conditions, and Microhabitat on Cercocarpus ledifolius Nutt. Seedling Emergence and Establishment

There is concern that the conifer component of mixed coniferndeciduous forests in the Great Lakes region is on the decline, possibly the result of insufficient conifer regeneration. Limitations on conifer regeneration that occur during the first 18 months of seedling emergence and establishment were examined for Abies balsamea (L.) Mill. and Pinus strobus L. in two mixed coniferndeciduous forest types in northeastern Minnesota. We hypothesized that the removal of potential barriers to regeneration, including forest floor, seed predation, and competition with understory vegetation, will enhance conifer regeneration. We also hypothesized that the importance of the above regeneration barriers, and early regeneration success of each species, will differ beneath deciduous and conifer canopy types. The study was conducted under conifer and deciduous canopy types for two sites of each forest type: Abies balsamea n Populus tremuloides Michx. forest and Thuja occidentalis L. n Betula papyrifera Marsh. Germination experiments were conducted with seeds of A. balsamea and P. strobus. Experimental treatments included forest floor removal, caging to exclude seed predators and herbivory, and weeding to study the effects of understory competition. Abies balsamea and P. strobus responded differently to experimental treatments at different developmental stages. The best conditions for early regeneration of both A. balsamea and P. strobus included reduction of seed predation (p < 0.0001) and competition with understory vegetation (p ≤ 0.001). Abies balsamea additionally benefited from a conifer overstory (p < 0.0001) and a reduction in thickness of the forest floor (p < 0.01).

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Canopy type, forest floor, predation, and competition influence conifer seedling emergence and early survival in two Minnesota conifer-deciduous forests

-A greenhouse experiment was conducted to determine the effect of soil surface and litter cover on germination, survival and biomass production of chicory (Cichorium intybus L.). Surface treatments which had more microtopographical relief (soil covered with clods or rocks) were better for germination and growth compared to treatments in which surfaces were smooth or covered with fine or coarse litter. Seeds germinated in crevices formed where clods or rocks interfaced with the soil surface creating "safe sites" which retained moisture and provided seedling roots an opportunity to become established. Optimal experimental treatments were similar to chicory's roadside habitat which appears to be hot, dry and inhospitable, but provides the topographical heterogeneity necessary for successful germination and seedling establishment.

Marian Smith

Papers

Effects of Soil Surface Microtopography and Litter Cover on Germination, Growth and Biomass Production of Chicory (Cichorium intybus L.)