Microbiotic soil crusts - a review of their roles in soil and ecological processes in the rangelands of Australia

Abstract

Microbiotic crusts are assemblages of non-vascular plants (mosses, liverworts, algae, lichens, fungi, bacteria and cyanobacteria) which form intimate associations with surface soils. They play a major role in infiltration processes through changes to soil physico-chemical properties, and through their influence on soil surface roughness. Whilst some research suggests that they may restrict infiltration, Australian experience is that they are generally associated with enhanced infiltration. Unlike physical soil crusts, microbiotic crusts stabilize the soil against water and wind erosion, increasing landscape stability, particularly in areas of low vascular plant cover. Microbiotic crusts are thus useful indicators of soil surface condition, and cyanobacteria in the crusts fix nitrogen which may be utilized by developing vascular plant seedlings. Little is known, however, about how they interact with vascular plants and soil invertebrates. Their role in rangeland ecosystems has received renewed attention over the past few years with an increasing interest in ecologically sustainable development of arid and semi-arid grazing systems.In this review we discuss the characteristics and distribution of microbiotic crusts in the rangelands of Australia, their roles in soil and eco!ogical processes and the impacts of fire and grazing. Finally we propose a new system for classifying crusts into functional groups and identify areas requiring further investigation.

Analysis of environmental factors determining development and succession in biological soil crusts

“…In desert regions, such as Shapotou and Dalate Banner regions, once BSCs have formed, their development and succession would be a natural process, which generally begins from the stage of cyanobacterial crusts (Eldridge and Greene, 1994;Zaady et al, 2000;Garcia-Pichel and Pringault, 2001;Zhang et al, 2006). As the special crust type in Shapotou region, lichen crusts develop and succeed from cyanobacterial crusts, and that process might include two stages of lichen emergence and reproduction.…”

“…In arid and semi-arid regions, many types of vegetation are restricted to the severe environmental conditions, while biological soil crusts (BSCs) appear commonly there, and even occupy more than 70% of the Science of the Total Environment 538 (2015) [492][493][494][495][496][497][498][499] living coverage in some regions (Eldridge and Greene, 1994;Belnap and Lange, 2001;Hu et al, 2012). BSCs are the complex biological-soil mosaic layers within the top millimeters of soil surface, composed of photoautotrophic cyanobacteria, algae, lichens, mosses and heterotrophic bacteria and micro-fungi (Belnap and Lange, 2001;Hu and Liu, 2003;Lan et al, 2012a).…”

Cladonia lichens on extensive green roofs: evapotranspiration, substrate temperature, and albedo

“…Other plant growth forms have also been used on extensive green roofs, with grasses, forbs, and mosses among the most frequent 3, 4 . Lichens are often found on conventional roof surfaces 5 and form an important component of cryptogamic crusts in terrestrial ecosystems 6 . Cryptogamic crusts in arid environments perform a range of ecosystem services, such as stabilizing soil, fixing nitrogen, and enhancing soil water holding capacity 7 , but have not been intentionally planted in green roof ecosystems.…”

Small-Scale Vertical Distribution of Algae and Structure of Lichen Soil Crusts

“…They are composed of algae (including cyanobacteria and eukaryotic algae), lichens, mosses, fungi, and bacteria. BSCs are the main contributors to water and nutrient cycling [1][2][3][4][5], sand stabilization [1,6], and soil formation [7], playing important roles in the establishment and performance of vascular plants [8,9], and serve as habitats for a dependent food web [10]. According to the different dominant species in different developmental stages, BSCs can be classified into three typical stages: algae soil crusts (ASCs), lichen soil crusts (LSCs), and moss soil crusts [11].…”

“…Most studies of LSCs have focused on the composition and distribution of the crust species [15][16][17][18] and ecological functions [3,6,7,13,14]. Few studies have been performed on their inner structures, algae distribution.…”