Understanding the Importance of Seed Banks in Ecosystems
Seed banks, categorized into soil and aerial types, serve as essential reservoirs for viable seeds and propagules. Soil seed banks are natural storage areas for seeds within ecosystems and play a crucial role in plant regeneration. They can persist for varying durations, influencing plant diversity and weed management. Species like Agrostemma githago and Medicago have distinct behaviors in seed persistence. The longevity of seeds varies widely, with some species capable of lasting over 100 years.
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SEED BANK Seed bank is the reservoir of viable seeds or vegetative propagules. 2 types of seed bank: Soil seed bank Arial seed bank
Types of Seed Banks-Thompson and Grime (1979) 2 types: A)Arial seed bank. B)Soil seed bank. Transient: persist < 1 yr Persistent: persist > 1 yr i. Short term persistant_1 to 5 yrs ii. Long term-more than 5 yrs (Chenopodium album-40 to 1600) A species forming no soil seed bank at all (except the dry season between ripening and the first autumnal rains) is Agrostemma githago (Corncockle), which is a formerly widespread cereal weed
Which species form large, persistent SB? Disturbance spp Annuals/biennials Small-seeded spp
Ref: seed bank and its perspective by Junling Ma Zhimin Liu Dehui Zeng
Soil seed bank The soil seed bank is the natural storage of seeds, often dormant, within the soil of most ecosystems. The study of soil seed banks started in 1859 when Charles Darwin observed the emergence of seedlings using soil samples from the bottom of a lake. The first scientific paper on the subject was published in 1882 and reported on the occurrence of seeds at different soil depths.
Living seeds have been found in or on the soil for different durations ,different seasons , at different depths (buried light-germinate)(Duvel, 1902; Grundy et al., 2003; Benvenuti, 2007), in different quantities and in different states of dormancy or procession to germination (Baskin and Baskin,1998) In agro ecosystem,the soil seed bank is closely associated to weed studies a. Weed control programmes b. SCMP-Rational use of Herbicides
Seeds of several plant species hardly ever enter the soil but persist at its surface or in the litter for many years, prominent examples are the large and hard fruits of Medicago and Neurada, which contain dozens of seeds and can give rise to several plants over several years. Plants differ in the duration their seeds remain in the soil and even within a species and among seeds of the same cohort there is variability in the time they spend in the soil seedbank.
Seed longevity: Longevity of seeds is very variable and depends on many factors; few species exceed 100 years. In typical soils the longevity of seeds can range from nearly zero (germinating immediately when reaching the soil or even before) to several hundred years. Some of the oldest still-viable seeds were those of Lotus (Nelumbo nucifera) found buried in the soil of a pond; these seeds were estimated by carbon dating to be 1,040 years old.
Density: The mortality of seeds in the soil is one of the key factors for the persistence and density fluctuation, especially for annual plants. Studies on the genetic structure of Androsace septentrionalis populations. There are indications that mutations are more important for species forming a persistent seed bank compared to those with only transient seeds. The increase of species richness in a plant community due to a species-rich and abundant soil seed bank is known as the storageeffect.
Associated ecosystem processes The term soil diaspore bank can be used to include non-flowering plants such as ferns and bryophytes. In addition to seeds, many plants have vegetative propagules to facilitate forming new plants, migration into new ground, or reestablishment after being top-killed. These propagules are collectively called the soil bud bank, which includes dormant and adventitious buds on stolons, rhizomes, and roots.
Arial seed bank A canopy seed bank or aerial seed bank is the aggregate of viable seed stored by a plant in its canopy Canopy seed banks occur in plants that postpone seed release for some reason. It is often associated with serotiny, the tendency of some plants to store seed in a cone (e.g. in the genus Pinus) or woody fruits (e.g. in the genus Banksia), until seed release is triggered by the passage of a wildfire. It also occurs in plants that colonise areas of shifting sands such as sand dunes. In such cases, the seed is held in the canopy even if the canopy becomes buried; thus the seed is anchored in place until good germination conditions occur.
Seed bank-Conservative of genetic diversity Role in genetic diversity and natural restoration as well as to recover endangered plant species. (Red data books document) Coleanthus subtilis- today highly endangered or extinct plant species. One characteristic of such plants is their capacity to survive in the soil seed bank during unsuitable conditions. Due to the longevity of seeds, those species remain present for decades Reference: K.G. BERNHARDT & E. ULBEL University of Natural Resources and Applied Life Sciences, Department of Integrative biology, Gregor-Mendel-Strasse 33, 1180 Vienna, Austria
Environment Re-Constituting natural environment of many ecosystems (by wildfire, catastrophic weather timber harvesting is largely due to the soil seed bank)agricultural operations. Forest ecosystems and wetlands contain a number of specialized plant species forming persistent soil seedbanks. Before the advent of herbicides a good example of a persistent seed bank species, Papaver rhoeas, sometimes was so abundant in agricultural fields in Europe that it could be mistaken for a crop. The absence of a soil seed bank impedes the establishmentof vegetation during primary succession, while presence of a well-stocked soil seed bank permits rapid development of species-rich ecosystems during secondarysuccession
