Annually-recurring ephemerals often respond to temperature, as well. In such a case seed coatings may be sensitive to soil salinity, which decreases as more rainfall seeps into the ground. Some annuals that require at least one inch (two to three cm) of precipitation in order to complete their life cycle will not germinate when only one centimeter has fallen. In addition, seeds have highly sensitive germination triggers. In the drier deserts of Egypt, where rain may not fall for a decade or more, dormant seeds must survive for a much longer time before germination. In the Sonoran Desert of California and Arizona, annual precipitation allows ephemeral plants to reappear almost every year. The frequency of desert ephemeral recurrence depends upon moisture availability. Because water is usually unavailable in such environments, many desert perennials also behave like ephemeral plants, lying dormant and looking dead for months or years but suddenly growing and setting seed after a rare rain fall. Often widespread and abundant after a rain, these plants provide an essential food source for desert animals, including domestic livestock. In some very dry deserts, as in North Africa, ephemeral annuals comprise the majority of living species -although this rich flora can remain hidden for years at a time. Eggs, or sometimes the larvae of these animals, then remain in the soil until the next moisture event.Įphemerals play an important role in many plant communities. The spadefoot toad ( Scaphiopus multiplicatus ), for example, matures and breeds in as little as eight days after a rain, feeding on short-lived brine shrimp, which in turn consume algae and plants that live as long as water or soil moisture lasts. Here small insects and even amphibians have ephemeral lives. Ephemeral ponds, short-duration desert rain pools, are especially noted for supporting ephemeral species. Tiny, usually microscopic, insects and other invertebrate animals often appear with these desert annals, feeding on briefly available plants, quickly reproducing, and dying in a few weeks or less. In such cases the amount and frequency of rainfall determine entirely how frequently ephemerals appear and how long they last. The most common types of ephemeral species are desert annuals, plants whose seeds remain dormant for months or years but which quickly germinate, grow, and flower when rain does fall. Ephemeral species are plants and animals whose lifespan lasts only a few weeks or months.
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