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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    • "Although changes in soil properties underneath shrubs are consistent across soil types, climatic conditions, and plant species, the magnitude of such changes is highly variable (Cortina and Maestre 2005). The formation and development of fertile islands are shaped by a range of interacting physical and biotic concentrating mechanisms that are closely related to a number of factors (Li et al. 2007; Schlesinger et al. 1996) that includes shrub species characteristics, canopy size, nutrient uptake via roots and litter deposition (Li et al. 2007), aeolian dust deposition, stem-flow (Whitford et al. 1997), microbial population and rhizosphere root activity, accelerated biogeochemical cycling underneath the canopy (Li et al. 2007), habitat, and climatic conditions (Cortina and Maestre 2005). Shrub species (Li et al. 2007; Titus et al. 2002) and habitat (Li et al. 2008; Su et al. 2004) represent the principle factors that affect the formation and concentration of resource islands. "
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    ABSTRACT: Shrub-induced soil property spatial heterogeneity is common in arid and semi-arid ecosystems and aids desertified land restoration. However, the effectiveness of this technique may rely on the plant species used and the habitat conditions present. To assess the degree to which planting two native species, Haloxylon salicornicum and Calligonum polygonoides, facilitates degraded land restoration, soil and herbaceous plant community properties were measured 7 years after planting. Soil samples were extracted at two depths (0-5 and 5-20 cm) from three sub-habitats, i.e., under the shrub canopy, from alleys between shrubs and from the open area. Shrub planting increased the quantity of silt + clay content (30-39 %); enhanced water holding capacities (24-30 %); increased the levels of organic carbon (48-69 %), available nitrogen (31-47 %), available phosphorus (32-41 %), and electrical conductivity (21-33 %); and decreased the pH (7-12 %) and bulk density levels (5-6 %) in the surface layer of soils beneath the canopy. Soil property changes were more significant at the surface (0-5 cm) than in the deeper layer (5-20 cm), and were more pronounced under H. salicornicum than under C. polygonoides. Furthermore, the density and biomass levels of herbaceous plants were 1.1 to 1.2 and 1.4 to 1.6 times greater, respectively, in the shrub alleys than in open area. H. salicornicum induced more robust soil amelioration and herbaceous plant facilitative properties than did C. polygonoides. Artificially planting these shrubs may thus be employed to restore degraded areas of arid regions.
    Environmental Management 09/2014; 55(1). DOI:10.1007/s00267-014-0372-1 · 1.72 Impact Factor
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    • "Nevertheless, a shift from facilitation to competition under high-abiotic-stress conditions may occur when the levels of the most limiting resource are so low that the benefits provided by the facilitator cannot overcome its own resource uptake (Maestre and Cortina, 2004). Thus, despite the fact that in water-limited environments, plants generally improve soil fertility and microclimate under their canopies (Cortina and Maestre, 2005), these changes do not always translate into increased water availability in their immediate vicinity (Sala et al., 1989; Valladares and Pearcy, 2002). Canopy interception can reduce the amount of water reaching the soil, and root competition for water can make the understorey drier than open patches (Abrams and Mostoller, 1995; Valladares and Pearcy, 2002; Hamerlynck et al., 2011). "
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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 04/2014; 7(2). DOI:10.1002/eco.1401 · 2.43 Impact Factor
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    ABSTRACT: Shrubs often dominate early successional stages in areas that are suitable for the establishment of forests. Under a dense shrub canopy, the density of seedlings of late successional tree species can be low, suggesting that colonisation by forest species may be hampered. In contrast, several studies have shown that positive interactions may offset the negative effects of competition when environmental conditions are limiting. We have evaluated the effect of different types of shrubland clearing and planting location on the establishment of Quercus suber seedlings under Mediterranean conditions. Clearing a 2-m spot around planted seedlings had a weak effect on seedling performance. Seedlings planted on highly exposed microsites showed 65% increase in survival as compared to seedlings planted in undisturbed shrubland. Seedling growth showed a similar trend. For example average stem height in seedlings planted in open sites was 39.60 cm as compared to 29.59 cm in seedlings planted on undisturbed shrubland. Increased soil water availability may be responsible for the positive effect of shrubland clearing. Seedling survival was negatively correlated with the abundance of obligate seeders such as Cistus salviifolius, and positively correlated with the abundance of sprouting species such as Erica arborea suggesting that the interaction between Q. suber seedlings and extant vegetation may be species dependent.
    Forest Ecology and Management 03/2008; 255(3-4-255):374-382. DOI:10.1016/j.foreco.2007.09.074 · 2.66 Impact Factor
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