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Plant Effects on Soils in Drylands: Implications for Community Dynamics and Ecosystem Restoration

DOI: 10.1007/1-4020-3447-4_6
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    ABSTRACT: Exotic species have been widely used in reforestation in arid areas in northern Africa, as they provide ecosystem services that native species may be unable to supply. But information on their effect on ecosystem function and composition is scarce. We have evaluated the effect of 20-year-old Acacia saligna (Labill.) H.L. Wendl. plantations on the soil surface conditions and vascular plant composition in central Tunisia. Landscape function analysis (LFA) indices of soil stability, infiltration, and nutrient recycling underneath A. saligna increased by 1%, 138%, and 148%, respectively, in comparison to bare areas. This species, however, did not affect indicators of soil surface functionality, the spatial pattern of resource sinks-sources, or vascular plant species composition at a plot scale. This was probably due to low A. saligna cover, and a limited degree of litter incorporation into the soil surface. Our results suggest that the potential for improving ecosystem function and fostering succession by using this species seems to be limited in this arid environment.
    Arid Land Research and Management 01/2009; 23(1):28-46. · 0.56 Impact Factor
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    ABSTRACT: Water relations are essential in plant–plant interactions, particularly in Mediterranean coastal sand dunes, owing to marked drought periods and the possibility of groundwater (GW) salinization. In this study, seasonal water use dynamics were explored in the interaction between a native–invasive species, Retama monosperma, and the endangered Thymus carnosus, in south-western Spain. The following variables were measured: xylem water isotopic composition to determine water sources, predawn and midday stem water potential and free leaf proline content as stress indicator. GW electrical conductivity and stable isotopes were also analysed to assess water table salinity. In late summer and spring, the warmest seasons, Thymus beneath Retama displayed significantly lower water potential and higher leaf proline content than isolated Thymus, whereas Retama showed the highest proline content in autumn and winter. Water sources showed different patterns depending on the Thymus situation: Isolated ones always matched the brackish GW, as well as Retama plants, whereas Thymus beneath Retama switched among rainfall, soil and water table, showing a seasonal change in the water-harvesting strategy. Overall, competition for water sources between both species was discovered, which led to a shift in water use and water uptake strategies of understorey Thymus. The results also demonstrate the importance and potential use of species interaction studies in the development of threatened species management strategies. Copyright © 2013 John Wiley & Sons, Ltd.
    Ecohydrology 05/2013; 7(2). · 2.78 Impact Factor
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    ABSTRACT: Aims Studies of species distribution patterns traditionally have been conducted at a single scale, often overlooking species–environ-ment relationships operating at finer or coarser scales. Testing diversity-related hypotheses at multiple scales requires a robust sampling design that is nested across scales. Our chief motivation in this study was to quantify the contributions of different predictors of herbaceous species richness at a range of local scales. Methods Here, we develop a hierarchically nested sampling design that is balanced across scales, in order to study the role of several envi-ronmental factors in determining herbaceous species distribution at various scales simultaneously. We focus on the impact of woody vegetation, a relatively unexplored factor, as well as that of soil and topography. Light detection and ranging (LiDAR) imaging enabled precise characterization of the 3D structure of the woody veg-etation, while acoustic spectrophotometry allowed a particularly high-resolution mapping of soil CaCO 3 and organic matter contents. ImportantFindings We found that woody vegetation was the dominant explanatory variable at all three scales (10, 100 and 1 000 m 2), accounting for more than 60% of the total explained variance. In addition, we found that the species richness–environment relationship was scale dependent. Many studies that explicitly address the issue of scale do so by comparing local and regional scales. Our results show that efforts to conserve plant communities should take into account scale dependence when analyzing species richness–envi-ronment relationships, even at much finer resolutions than local vs. regional. In addition, conserving heterogeneity in woody veg-etation structure at multiple scales is a key to conserving diverse herbaceous communities.
    Journal of Plant Ecology 03/2012; · 2.28 Impact Factor

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