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.

Germination of Six Grassland Herbs in Microsites with Different Water Contents

The ecology of seeds

Understanding the adaptations that allow species to live in temporally variable environments is essential for predicting how they may respond to future environmental change. Variation at the intergenerational scale can allow the evolution of bet-hedging strategies: a novel genotype may be favoured over an alternative with higher arithmetic mean fitness if the new genotype experiences a sufficiently large reduction in temporal fitness variation; the successful genotype is said to have traded off its mean and variance in fitness in order to ‘hedge its evolutionary bets’. We review the evidence for bet-hedging in a range of simple plant systems that have proved particularly tractable for studying bet-hedging under natural conditions. We begin by outlining the essential theory, reiterating the important distinction between conservative and diversified bet-hedging strategies. We then examine the theory and empirical evidence for the canonical example of bet-hedging: diversification via dormant seeds in annual plants. We discuss the complications that arise when moving beyond this simple case to consider more complex life-history traits, such as flowering size in semelparous perennial plants. Finally, we outline a framework for accommodating these complications, emphasizing the central role that model-based approaches can play.

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https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2010.0707

Evolutionary bet-hedging in the real world: empirical evidence and challenges revealed by plants

(1) Changes in vegetation structure, species composition, and species dominance were studied over the first twenty-two months of succession after the cutting and burning of several mature tierra firme (i.e. non-flooded) forest sites in south Venezuela in the upper Rio Negro region of the Amazon Basin. To explain the observed succession, additional field investigations were undertaken. (2) Four months after burning the density of plants was less than 1 m-2. The density of successional woody plants, forbs, and grasses increased rapidly from the fourth to the tenth month of succession. There was little change in plant density between the tenth and twenty-second month, but a large change in vegetation height occurred during this time. By the twenty-second month a loose canopy of Cecropia spp. was present at 5 m height. (3) Many of the forest tree species sprouted from the stump when cut, but burning killed sprouts and significantly reduced the size of the seed bank. Nevertheless, the first successional woody colonizers established from seed which survived the burn. The first forb and grass colonizers established from seeds dispersed onto the site after the burn. (4) The common successional woody species had bator bird-dispersed seeds. Many forbs and grasses had wind-dispersed seeds. (5) Population densities were low during the first months of succession because of the low density of propagules and because the low rainfall during this time was not favourable for seedling germination or establishment. The rapid increase in plant density after about the fourth month occurred because the early colonizers had then begun to produce, and disperse locally, large numbers of seeds. (6) There were six distinct microhabitat types present on the sites after burning. Most species tested showed distinct microhabitat preferences.

http://www.jstor.org/stable/pdfplus/2259689.pdf

Early plant succession after cutting and burning in the upper rio negro region of the amazon basin

The safe sites, i. e., microsite requirements for germination and establishment, were partially characterized for three of the dominant grass species of the Edwards Plateau of central Texas, Aristida longiseta, Bouteloua rigidiseta and Stipa leucotricha. Seeds were germinated and grown in field-collected soil in a greenhouse under different watering regimes and in soil-filled benches with various soil surfaces and with adult plants. Both watering regime and microsite type strongly affected germination and establishment. Litter and rocks, but not the proximity of an adult plant, increased germination, survival and growth. A safe site for these species appears to be a microsite that prevents desiccation. Differences among the species in the relative favorableness of different types of microsites were slight. Species differed more in the timing of germination. Since the timing of rainfall and of temperature fluctuations varies considerably between years in central Texas, different cohorts of seedlings, and hence different species, may be successful in different years.

Germination of Six Grassland Herbs in Microsites with Different Water Contents

Citations

The ecology of seeds

Evolutionary bet-hedging in the real world: empirical evidence and challenges revealed by plants

Early plant succession after cutting and burning in the upper rio negro region of the amazon basin

Microsite requirements for germination and establishment of three grass species

The Ecology of Seeds: Seedling establishment

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