Presentation on theme: "Soil Biological Crusts On Rangelands: Their Role In Soil Conservation And Habitat Restoration James P. Dobrowolski Extension Watershed Specialist 32 nd."— Presentation transcript:
Soil Biological Crusts On Rangelands: Their Role In Soil Conservation And Habitat Restoration James P. Dobrowolski Extension Watershed Specialist 32 nd Annual Pacific Northwest Range Management Workshop Spokane, Washington April 1, 2003 Natural Resource Sciences Washington State University Pullman, Washington
Biological Soil Crust = Cryptogamic = Cryptobiotic = Microbiotic = Microphytic u Biological soil crusts are a complex mosaic of cyanobacteria, green algae, lichens, mosses, microfungi, and other bacteria.
Soil Biological Crust Structures u Many of these organisms form microscopic fibers and secrete polysaccharide compounds that bind surface soil particles into stable biological soil crusts that are very resistant to wind and water erosion
u These crusts affect soil stability, water infiltration, and fertility of soils. Disturbance of these crusts can lead to increased erosion and resultant losses of organic matter, fine soil particles, nutrients and microbial populations in soils.
Vesicular horizons or crusts are formed through cyclic wetting and drying in silt-dominated soils
What was driving vertical soil moisture movement between sagebrush plants?
u Disturbance can directly and indirectly affect many aspects of the structure and function of biological crust communities, including cover, species composition, and carbon and nitrogen fixation. The impact of a given disturbance depends on its severity, frequency, timing, and type, as well as the climatic conditions during and after it.
What Happens When You Disturb Soil Biological Crusts?—It Depends! u Comparing recovery rates from different studies can be problematic, as factors known to control recovery rates (such as site stability and precipitation following disturbance) are often not reported.
What Happens When You Disturb Soil Biological Crusts?—It Depends! u More importantly, disturbance severity is seldom quantified. Studies generally report disturbance levels as “light,” “moderate,” or “heavy” without any definition of these categories; thus, what is “moderate” in one study may be considered “heavy” in another. u As studies cover a large range of climatic zones, soil types, and levels of disturbance, recovery rates reported in the literature have ranged widely (2 to more than 3,800 years), and either appear to show no pattern or often appear contradictory.
What Happens When You Disturb Soil Biological Crusts?—It Depends! u On silty soils of the Great Basin, early wet season (winter) use by livestock has been shown to have less impact on crust cover and species composition than late winter or spring use. u As crustal species are only metabolically active when wet and are brittle when dry, disturbance in dry seasons is generally more destructive, and organisms are less able to recover. u Crusts on clay soils can be an exception, as they are often more vulnerable when wet.
What Happens When You Disturb Soil Biological Crusts?—It Depends!
The Military Meets Environmental Regulations u Over 70% of all Department of Defense lands are in the semiarid and arid regions of the United States. u Stable, realistic training and testing environments in arid and semiarid landscapes exist across the West. u Although traditionally viewed as less habitable, public sentiment toward arid ecosystems has shifted toward environmental accountability and habitat protection. Once thought to be sterile environments, deserts are now known to promote endemic biodiversity, provide sensitive habitats and support endangered species.
The Military Meets Environmental Regulations u When Belnap and Warren (2002) studied the tank tracks from World War II-era training (Patton’s tanks) in the Mojave, the tracks were still visible. u Based on biomass estimates, the cyanobacterial component of biological soil crusts had recovered 46- 65% in tracks when compared with outside. u Recovery of lichen cover has been much slower—in plant interspaces where tracks occur, the most “disturbance sensitive” lichen showed only 3% recovery. Assuming recovery is linear—and complete only when the most sensitive species has fully recovered in the most limiting habitats—2000 years?
u Four to ten passes of an M110 vehicle pulverized the crust, reduced infiltration capacity, increased sediment transport after simulated rainfall and reduced the threshold friction velocity (u *t ) for soil particle entrainment after wind simulation.
The Military Meets Environmental Regulations u Reestablishment of biological soil crusts following disturbance represents our best and most economical alternative to maintaining and rehabilitating disturbed arid lands. u The alternatives - pave the desert, irrigate it, or sacrifice it - are unacceptable. u Live cultures of several species of cyanobacteria have been pelletized in an alginate matrix. When applied to disturbed soils, the pellets have been shown to significantly increase the cyanobacterial population, nitrogen fixation, and infiltration of rainfall into the soil.
Soil Biological Crusts as Vehicles of Rangeland Repair u Why cyanobacteria? “Kicks off” succession—autogenic repair. u Cyanobacteria survives pellitization and can successfully escape from crushed alginate pellets. Improved colonization and nitrogen fixation were observed in the laboratory on Dugway Proving Ground soils in Utah (Buttars et al. 1998). u Study plots were established in 1992 at Dugway Proving Ground, UT and during 1995 at Yuma Proving Ground, AZ, and Fort Bliss, TX. The effects of cyanobacterial pellet application are being monitored on plots that were previously trampled or burned. To date, the results are promising.
Soil Biological Crusts as Vehicles of Rangeland Repair Other mixed life form applications: u St. Clair et al. (1986) inoculated a severely burned “blowout” site with a soil crust slurry. u Belnap (1993) inoculated scalped plots with crushed biological crust—better than uninnoculated scalped sites. u At a large scale, you might have to destroy a site to save another…