PARENT SESSION
Poster Session 23: Soil Ecology
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Islands of fertility in deserts: do biological crusts affect their formation?
Housman, David*,1, Belnap, Jayne1, Darby, Brian2, Neher, Deborah2, 1 USGS-Canyonlands Research Station, Moab2 University of Vermont, Burlington
ABSTRACT- The island of fertility concept has been widely studied in semiarid regions of the American southwest, emphasizing accumulation of essential nutrients under plant canopies and depletion within plant interspaces. However, while past studies have frequently classified the interspace as simply bare soil, there are many areas where it contains biological soil crusts that positively affect nutrient availability. The positive effect of these soil crusts on soil water and nutrients becomes more pronounced as later successional mosses and lichens colonize. Therefore, to see if the island of fertility concept is valid in areas with biological soil crusts, we compared nutrient content in the interspace and understory of a shrub (Coleogyne ramosissima) and grass (Stipa hymenoides) that coexisted with early and later developing biological soil crusts. Levels of organic matter, NO3, NH4, and P were not consistently greater in soils under plants compared to interspace soils. The presence of later successional crusts appeared to equalize distribution of these nutrients, especially in the grass community and for soil P. Soil Ca, Cu, and CaCO3 were often greater in the interspace. Soil amoebae, ciliate, and flagellate abundance was not different between plant canopies and the interspace. In contrast, nematode abundance was significantly higher under plants. Our results indicate that biological soil crusts increase the content of some soil nutrients in plant interspaces, counteracting the fertile island effect. As we continue our assessments it is clear that biological soil crusts are an important component of the nutrient cycling in these ecosystems and deserve further study.
Key words: biological soil crust, islands of fertility, soil chemistry, soil fauna