COVER AND FLORISTICS OF MICROPHYTIC SOIL CRUSTS IN RELATION TO INDEXES OF LANDSCAPE HEALTH

An extensive field survey of 282 sites over 500 000 km(2) of rangeland in eastern Australia was carried out to investigate the relationships between cover and floristics of microphytic soil crusts and indices o f landscape health. Empirical quadrat-based data were used to calculat e three indices of landscape health (soil stability, infiltration capa city and nutrient status) according to the method of Tongway (1994). A nalyses were based on a subset of 104 sites from landscapes dominated by red earths and calcareous earths, where the loss of microphytic cru st cover is indicative of a loss in soil productive potential. Crust c over and floristics were further compared with an objective but widely used method of assessing rangeland condition based on the use of phot ostandards. Crust cover was a significant though weak predictor of sta bility of calcareous earth soils only (P < 0.001, R-2 = 0.106). On red earths, cover was a significant descriptor of rangeland condition (P < 0.001, R-2 = 0.171). However, overall, the percentage of the soil oc cupied by soil crusts was regarded a poor predictor of landscape healt h. Generally, increases in the number of lichen and bryophyte taxa at a site were associated with increasing rangeland condition (P < 0.001, R-2 = 0.178), landscape stability (P = 0.047, R-2 = 0.027) and nutrie nt status (P < 0.001, R-2 = 0.115), though these relationships varied according to soil type. Canonical Correspondence Analyses indicated th at some Lichens and bryophytes were consistently associated with eithe r stable, good condition sites (Xanthoparmelia spp., Catapyrenium laci nulatum, Buellia subcoronata, Aloina bifrons, Riccia lamellosa, Fossom bronia spp.) or unstable, poor condition sites (Heterodea benugleholei , Cladonia spp., Barbula calycina, Bryum spp., Desmatodon convolutus, Eccremidium arcuatum). The majority of taxa however had no strong affi nity with the four indices of landscape health. When easily recognisab le morphological groups of lichens were related to landscape health in dices, the group comprising yellow-green foliose lichen was the most s trongly associated with stable, healthy sites. The results suggest tha t disturbances influencing soil stability and soil surface condition s uch as trampling and fire are likely to lead to changes in the composi tion of soil crust communities.