Laboratory-based techniques for assessing the functional traits of biocrusts

Functional traits are increasingly being used to assess the degree to which ecosystems maintain key processes. The functional traits of vascular plants are well-documented but those of non-vascular plants are poorly known. We describe a comprehensive methodology to measure the functional traits of soil-borne lichens, mosses and liverworts making up biocrust (biological soil crust) communities. We collected 40 biocrust taxa from across 10,000 km(2) of eastern Australia, and measured eight functional traits using a combination of mensurative studies and laboratory-based experiments. These traits were sediment capture, absorptivity, root (or rhizine) length, height, and the activity of four enzymes involved in key nutrient cycles; beta-glucosidase, beta-D-cellobiosidase, N-acetyl-beta-glucosaminidase and phosphatase. Taxa were distributed across a broad range of trait values. Sediment capture values ranged from 2 % in the crustose lichen Diploschistes thunbergianus to 83 % in the tall moss Triquetrella papillata. The highest absorptivity value was observed in the moss Bartramia hampeana ssp. hampei, which was able to absorb 12.9 times its dry mass in water, while the lowest value, 0.3, was observed in Diploschistes thunbergianus. Multivariate analyses revealed that biocrust morphological groups differed significantly in their functional profiles. Our results indicate that biocrust taxa vary greatly in their functional traits and that morphological groups explain, in part, the ability of biocrusts to sequester resources (sediment, moisture) and to undertake key processes associated with the cycling of carbon, nitrogen and phosphorus. This methodology will enhance our understanding of ecosystem functioning in drylands where biocrusts make up a large component of the surface cover and provide a range of ecosystem goods and services.