Biological Soil Crusts in a Xeric Florida Shrubland: Composition, Abundance, and Spatial Heterogeneity of Crusts with Different Disturbance Histories

Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
Microbial Ecology (Impact Factor: 2.97). 02/2002; 43(1):1-12. DOI: 10.1007/s00248-001-1017-5
Source: PubMed


Biological soil crusts consisting of algae, cyanobacteria, lichens, fungi, bacteria, and mosses are common in habitats where water and nutrients are limited and vascular plant cover is discontinuous. Crusts alter soil factors including water availability, nutrient content, and erosion susceptibility, and thus are likely to both directly and indirectly affect plants. To establish this link, we must first understand the crust landscape. We described the composition, abundance, and distribution of microalgae in crusts from a periodically burned, xeric Florida shrubland, with the goal of understanding the underlying variability they create for vascular plants, as well as the scale of that variability. This is the first comprehensive study of crusts in the southeastern United States, where the climate is mesic but sandy soils create xeric conditions. We found that crusts were both temporally and spatially heterogeneous in depth and species composition. For example, cyanobacteria and algae increased in abundance 10-15 years after fire and away from dominant shrubs. Chlorophyll a levels recovered rapidly from small-scale disturbance relative to intact crusts, but these disturbances added to crust patchiness. Plants less than 1 m apart can experience different crust environments that may alter plant fitness, plant interactions, and plant community composition.

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    • "A potentially significant nutrient source is nitrogen-fixing cyanobacteria found in soil crusts in rosemary scrubs. Density of cyanobacteria increases from zero immediately post-fire to a peak 8-15 years post-fire and declines thereafter (Hawkes and Flechtner 2002). "

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    • "[4]. However, our understanding of the community structure remains very limited, not least because the majority of studies investigating phototroph diversity in BSCs have used culture dependent methods which are prone to bias [5], [7], [9], [32], [33], or molecular methods that target 16S rRNA of bacteria, which ignore the diversity of eukaryotic phototrophs [2], [3], [6], [10], [11], [34]. Molecular microbial community analysis of bacterial diversity at the soil surface has shown a dominance by cyanobacteria [2], [3], [6], [11], for example, Abed et al. [6] found that 77–81% of clones from BSCs of Oman had close homology to cyanobacteria. "
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