Article

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: 3.12). 02/2002; 43(1):1-12. DOI: 10.1007/s00248-001-1017-5
Source: PubMed

ABSTRACT 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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    • "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 · 2.72 Impact Factor
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    • "Identification was made on the basis of morphology using standard authoritative references (Anagnostidis and Komárek, 1988, 1990; Hawkes and Flechtner, 2002; H. J. Hu and Wei, 2006; Komárek and Anagnostidis, 2005, 1999; Johansen et al., 1982). Because many cyanobacteria grew poorly on artificial media, additional methods were needed to identify cyanobacteria from wetted soil samples incubated 48–72 h in light (Flechtner et al., 1998; Hawkes and Flechtner, 2002). Dominant species were determined by direct microscopic observation. "
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    ABSTRACT: In Gurbantunggut Desert, cyanobacterial and microalgal components were characterized within 60 soil samples collected from sand dunes. Fifty-one taxa of cyanobacteria and algae were identified. Without exception, the soils were alkaline, poor in nutrients, and showed large variations in other soil properties. Spatial heterogeneity for distribution of cyanobacteria and microalgae (diversity of morphotypes, species composition, and microbiomass) existed. Compared with other deserts in the world, the Gurbantunggut Desert has a greater diversity of cyanobacterial-microalgal morphotypes. Results from step regression showed that the diversity of morphotype was determined by total P, available P, and soil layer. Filamentous cyanobacteria dominated the community. Microcoleus vaginatus (Vauch.) Gom was the dominant species in most positions on sand dune, while the abundance of other dominant species varied depending on the sand dune position and the soil layer in which they occurred. The microalgal biomass was influenced by the content of Mg, crust type, soil moisture, sunlight, and oxygen concentration. A significant positive relation was found between microalgal biomass and diversity of morphotype. Species composition, diversity of morphotype, and microalgal biomass interacted with each other. The contents of P and Mg ion, soil texture, and soil moisture may be the main factors responsible for cyanobacterial-microalgal distribution.
    Arid Land Research and Management 07/2011; 25(3-3):275-293. DOI:10.1080/15324982.2011.565858 · 0.56 Impact Factor
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    • "More recent investigations have provided support for the improved chromatographic resolution when buffered with ammonium acetate (Wright et al., 1997) or MgCO 3 , as in this study. DMSO is a solvent that has been used by previous researchers in the extraction of biological soil crust chla (Beymer and Klopatek, 1991; Belnap et al., 1993; Hawkes and Flechtner, 2002) as well as lichens (Ronen and Galun, 1984). In our tests, we found that DMSO is well suited for the extraction of all soil crusts (Fig. 1), but there are significant health concerns associated with the routine use of DMSO that should be taken into consideration. "
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    ABSTRACT: We tested the efficacy of four different commonly used solvents (acetone, ethanol, dimethyl sulfoxide, methanol) for the extraction of chla from biological soil crusts of three different successional stages (dark, intermediate, and light). Our results indicate that a double extraction technique is necessary in order to achieve chla recovery in the range of 76–87 percent. For all crust types, ethanol and dimethyl sulfoxide extracted the greatest amount of chla using a two-extraction efficiency calculation.Research highlights► Chla extraction was greatest with Ethanol = DMSO > Methanol > Acetone. ► A two extraction method achieved a 76–87% extraction efficiency with Ethanol and 79–87% with DMSO. ► Caution should be used when comparing chla concentrations across different methodologies.
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