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). "
    Proceedings- Entomological Society of Washington 04/2014; 116(2):199-202. DOI:10.4289/0013-8797.116.2.199 · 0.53 Impact Factor
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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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    ABSTRACT: The upper few millimeters of soil harbour photosynthetic microbial communities that are structurally distinct from those of underlying bulk soil due to the presence of light. Previous studies in arid zones have demonstrated functional importance of these communities in reducing soil erosion, and enhancing carbon and nitrogen fixation. Despite being widely distributed, comparative understanding of the biodiversity of the soil surface and underlying soil is lacking, particularly in temperate zones. We investigated the establishment of soil surface communities on pasture soil in microcosms exposed to light or dark conditions, focusing on changes in phototroph, bacterial and fungal communities at the soil surface (0-3 mm) and bulk soil (3-12 mm) using ribosomal marker gene analyses. Microbial community structure changed with time and structurally similar phototrophic communities were found at the soil surface and in bulk soil in the light exposed microcosms suggesting that light can influence phototroph community structure even in the underlying bulk soil. 454 pyrosequencing showed a significant selection for diazotrophic cyanobacteria such as Nostoc punctiforme and Anabaena spp., in addition to the green alga Scenedesmus obliquus. The soil surface also harboured distinct heterotrophic bacterial and fungal communities in the presence of light, in particular, the selection for the phylum Firmicutes. However, these light driven changes in bacterial community structure did not extend to the underlying soil suggesting a discrete zone of influence, analogous to the rhizosphere.
    PLoS ONE 07/2013; 8(7):e69048. DOI:10.1371/journal.pone.0069048 · 3.23 Impact Factor
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    • "Disturbed soil lacks the mat of cyanobacterial and algal soil crust that covers much of xeric habitat (Johansen 1993), potentially allowing for the establishment of non-native species. The distribution of types and cover of soil crust is heterogeneous across ABS scrub (Hawkes and Flechtner 2002), suggesting that soil disturbance may play a role at the microhabitat level. "
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    ABSTRACT: Preventing the establishment of a non-native species is critical for ensuring the species does not become invasive, yet most non-native species will have little impact on their environment. Despite this, little is known about what influences whether a species will remain relatively benign, or whether it will cause economic or ecological harm. Understanding a plant’s microhabitat provides insight into the necessary conditions for establishment and the current distribution limitations of a population. We investigated microhabitat preference of the non-native natal grass (Melinis repens (Willd.) Zizka) in Florida scrub using microhabitat sampling to measure vegetation composition. We examined the extent to which microhabitats were associated with natal grass presence and biomass in invaded disturbed scrub and roadside plots using backwards stepwise logistic regression and general linear models to identify significant microhabitat variables. We further compared these plots with those in undisturbed, uninvaded scrub to characterize vegetation across habitat types, and used our model to predict the probability of natal grass invasion in undisturbed scrub. Natal grass preferred microhabitats with high litter volume and distance to shrubs and intermediate cactus, graminoid, and vine cover. Roadside natal grass achieved higher biomass and was less microhabitat limited than disturbed scrub natal grass. We determined that undisturbed scrub plots represent distinct microhabitats that natal grass is unlikely to invade. Microhabitat sampling provides land-managers a non-intrusive technique to assess potential habitat suitability based non-native plant preferences before a costly invasion occurs. KeywordsFlorida scrub–Invasive species– Melinis repens –Invasiveness–Microhabitat–Disturbance–Archbold Biological Station
    Biological Invasions 10/2011; 13(10):2309-2322. DOI:10.1007/s10530-011-0044-5 · 2.59 Impact Factor
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