Cryptobiotic Crusts: Enabling Nativeplants by Wayne P
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Cryptobiotic Crusts: Enabling NativePlants by Wayne P. Armstrong Arid desert regions where vegetation is sparse often have miniature communities of Close-up view of the soil lichen Th e slender black threads spore-bearing “plants” called Cryptobiotic crust along Placidium lacinulatum. Th e with forked branching are the cryptogams living together on the Travertine Palms Wash in thallus is composed of dark, rolled-up, desiccated thalli of soil surface. Th ey include colonies northeastern San Diego County. scalelike squamules. Th e a liverwort in Palm Canyon. of lichens, mosses, liverworts Th e dark crust is mostly the common name of “brown Th e hydrated green thalli and cyanobacteria. Unlike true squamulose soil lichen Placidium stipplescale” refers to the color in lower part of photo have vascular plants, their plant body is lacinulatum. and pitted squamules where the unrolled into their characteristic called a thallus and they have no fungal spores are released. fl attened,scalelike structure. fl owers or seeds. Th ese unique associations and their by-products form a crust of Cryptobiotic soil crusts are fragile and beautifully illustrated book A Field Guide soil particles bound together by organic easily damaged or destroyed by crushing to Biological Soil Crusts of Western U.S. materials. Th ey are commonly referred and trampling. Th is includes hikers and Drylands which is available on-line as a pdf to as biological soil crust or cryptobiotic horseback riders, not to mention off - fi le (see bibliography). Scytonema species crust, and are readily distinguished from road vehicles and the clearing of land for have an amazing worldwide distribution, nonbiological features, such as salt crusts agriculture and housing. In range lands of including black, fi brous, felt-like layers on desert playas. Th e name is derived from the western United States, well-developed on the surface of rocks and soil. Th ey are “crypto” (hidden) and “biotic” (life), and crust communities fl ourish only where one of the primary reasons why ancient literally refers to a layer of hidden life on cattle are excluded. It is very important to Maya pyramids in Guatemala appear the soil surface. Cryptobiotic crust is well stay on designated trails and roads. Even black. Another valuable contribution developed and widespread in Anza-Borrego when you are examining this remarkable by cyanobacteria is nitrogen fi xation, a Desert State Park. It forms a dark, thin desert phenomenon, it is important to remarkable bacterial skill in which inert layer on sun-baked soils of the badlands, tread lightly and not allow your shoes to atmospheric nitrogen gas is converted ancient riverbeds, and parched mountain penetrate the fragile crust. Like the Arctic into ammonia, thereby making the vital slopes. To appreciate these marvelous tundra, once this delicate community of element nitrogen available to the roots of organisms, you really need to get down on cryptogams has been damaged, it may take higher plants your knees, preferably with a good hand years to grow back. Large areas of crust In the Anza-Borrego Desert region, lens or magnifying glass. damaged by human activities may never several genera of lichens produce visible recover. Areas where cryptobiotic crusts Cryptobiotic crusts are important to desert soil crust that covers many miles of have been stripped away are vulnerable ecosystems throughout the world because undisturbed soils. Lichens are a very to wind and water erosion, fl ooding, dust they hold soils in place and protect the successful life form resulting from the storms and the invasion of naturalized underlying sediments from wind and water merging of genomes from two diverse weeds that thrive on disturbed soil. erosion. Members of the cryptobiotic crust kingdoms, the Fungi and Protista. Th ey stabilize soil particles with intertwining Cyanobacteria consist of microscopic contain fungal hyphae and photosynthetic cellular strands and intricate, root-like fi laments of cells with sticky polysaccharide algal cells living together in a mutualistic extensions called rhizoids and rhizines. sheaths that adhere to soil particles. relationship. Since the main body of All of these organisms promote soil water Th ey were once called blue-green algae; the lichen is composed of fungal tissue, retention which is vital to seed germination however, they share more characteristics they are usually referred to as lichenized and the survival of seedlings. Cryptobiotic with bacteria than true algae and are now fungi. In some species, the photosynthetic crusts are an important pioneer stage in placed in the kingdom Monera. Two symbiont is cyanobacteria rather than plant succession, thus enabling native fi lamentous species Microcoleus vaginatus algae. Lichens can survive in some of the grasses and herbs to become established in and Scytonema myochrous are listed as most inhospitable environments on earth, an otherwise hostile environment. important soil binders by Rosentretor, where neither symbiont could survive on Bowker and Belnap (2007) in their its own. In fact, lichens are an excellent 11 Continued on Page 12 squamules. When Plantae. Th ey are small, spore-bearing, wet the thallus nonvascular plants without cones, fl owers turns olive green. or seeds. Th ey are fairy common in wet Psora decipiens has meadows and along the banks of mountain larger, pinkish- streams; however, they are also found tan squamules in desert habitats as a component of with several black, cryptobiotic crust. In the Anza-Borrego spore-bearing Desert they grow in mountain canyons apothecia along the where they receive some shade and margins. Because rain. Liverworts have a green, fl attened, of its distinctive branched thallus that superfi cially reddish-tan color, resembles a foliose lichen. Th e underside this species is called is black, and when the thallus becomes “blushing scale.” desiccated, it rolls up into tiny black Th e photosynthetic cylinders resembling black threads. Th is Close-up view of the dark soil lichen called tarpaper lichen. Th e symbiont strategy reduces the surface area of the thallus is composed of numerous spherical granules called isidia, each (photobiont) for delicate thallus exposed to the sun and capable of growing into a new colony. Several disk-shaped fungal both of these dry air. Desert liverworts are practically fruiting bodies (called apothecia) are also visible. Th e inset shows a soil lichens is a unrecognizable at this stage. Th e closely- greatly magnifi ed view of the photosynthetic partner of this lichen, unicellular green related desert mosses also lose water and cellular fi laments of the cyanobacterium Nostoc. alga. dry up. Th eir bright green leaves wither example of synergism, because the whole is Another widespread and fade to brown or pale greenish-white. truly greater than the sum of its parts. Th e soil lichen in Anza-Borrego Desert is Th e cryptobiotic crust is certainly not algal and fungal components develop into Collema coccophorum. Th e granular black as showy as fi elds of desert ephemeral a unique body form with morphological thallus resembles a thin layer of tar or wildfl owers or the lush creosote bush features quite diff erent from either dried oil and is the derivation of the scrub in full bloom. Nonetheless, it plays symbiont. Th e fungal component typically common name “tarpaper lichen.” When an important role in the desert ecosystem produces its characteristic reproductive wet the thallus imbibes water, swells and by stabilizing vital soils necessary for body consisting of a spore-bearing cup- becomes gelatinous and shiny olive-green the perpetuation of native seed-bearing like structure (apothecium) or a vase- to greenish-black. In this condition it fi ts species. shaped perithecium lined on the inside another common name of “jelly lichen.” with spores. Th ese same structures are Like Psora, the fungal component produces References also produced by non-lichenized fungi in a minute disk-shaped apothecium, 1. Armstrong, W.P. 2008. “Cryptobiotic forested areas. although it is often diffi cult to spot because Crust in Anza Borrego Desert State It is not surprising that lichens form an it blends in with the thallus. Unlike Park.” Available on-line at: http:// important component of cryptobiotic Placidium and Psora, the photosynthetic waynesword.palomar.edu/crypto1.htm. partner of Collema is Nostoc, a microscopic crust in desert regions. Some species are 2. Nash, T.H. III, Ryan, B.D., Diederich, extremely drought resistant and survive cyanobacterium. Nostoc is a widespread genus that is found in freshwater ponds P., Gries, C. and F. Bungartz. 2004. for many months in a desiccated, dormant Lichen Flora of the Greater Sonoran state. In fact, some lichens may lose up to and creeks, and as a symbiont in cavities within the leaves of the water fern (Azolla) Desert Region. Volumes 1 & 2. Arizona 98 percent of their water content. When State University, Tempe, Arizona. a lichen is wetted by an occasional rain, and the coralloid surface roots of many it quickly imbibes water like blotting cycads. It is also the primary ingredient of 3. Rosentretor, R., Bowker, M. and paper, and photosynthesis within its “fat choy” (Nostoc fl agelliforme) in Chinese Jane Belnap. 2007. A Field Guide to algal symbiont is revived for a while. Th e cuisine, an important member of the soil Biological Soil Crusts of Western U.S. body (thallus) of two common species crust in northern China. Under high Drylands. USGS Canyonlands Research in Anza Borrego Desert State Park is magnifi cation the cells occur in fi laments Station, Moab, Utah. Available on-line composed of overlapping, scalelike lobes resembling minute strings of beads. Several at: sbcs.wr.usgs.gov/products/pdfs/Field_ called squamules. Th e foliose soil lichen species of Collema, Placidium and Psora are Guide_Book_25.pdf. Placidium lacinulatum is fairly widespread listed in Lichen Flora of the Greater Sonoran in the Park.