Biological Soil Crusts and Ecosystem Nitrogen and Carbon Dynamics

Abstract

Biological soil crusts are found in diverse ecosystems. They reach their best development in deserts and polar/alpine regions where harsh environments limit growth by higher plants allowing the ground surface to be exposed to direct sunlight (see Chap. 1). Coverage of soil crusts in these ecosystems can approach 100% in plant interspaces and total coverage may exceed that of higher plants (Kleiner and Harper 1972; Harper and Marble 1988). The capability of the dominant species in soil crusts to conduct photosynthesis and nitrogen (N) fixation, coupled with their high coverage, has led many researchers to conclude that they are dominant components of ecosystem carbon (C) and N cycles (Harper and Marble 1988; West 1990; Evans and Johansen 1999). However, relatively few studies have assessed the role of biological soil crusts in ecosystem C and N dynamics, and thus it is difficult to make broad generalizations regarding their role in these dynamics, due to variation in crust species composition and environments both within and between ecosystems (West 1990).