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

DOI: 10.1007/1-4020-3447-4_6


Available from: Jordi Cortina, Jun 11, 2015
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    ABSTRACT: Soil organic carbon (SOC) and total nitrogen (N) stocks in an agroforestry system with water harvesting were analysed in a field experiment and the results compared with those of other crop management systems in the Mediterranean zone of central Chile. Agroforestry with water harvesting showed higher positive effects on N stocks, mainly in the upper soil layer, than the other crop management systems. However, soil analysis revealed a lack of differences between treatments, a fact that might be related mainly to the short study time (12 years) and the high spatial variability in these soil properties at the experimental site. In addition, the Introductory Carbon Balance Model that simulates N processes (ICBM/N) was evaluated for simulating trends in SOC and N stocks in the field experiment. Soil data collected between 1996 and 2008 in the field experiment and primarily literature data sets were used to test ICBM/N and its performance was evaluated by considering uncertainty in model inputs using Generalised Likelihood Uncertainty Estimation (GLUE) methodology. The GLUE estimates (5% and 95%) and measured SOC and N stocks were in satisfactory agreement. The observed SOC and N stocks were bracketed by the uncertainty bands in 70% and 80% of the simulations, respectively. Sensitivity analysis showed the model to be most sensitive to C parameters, such as the humification coefficient (h). The results of this study show that ICBM/N can be an effective tool for estimating SOC and N stocks from agroforestry combined with water harvesting systems in the Mediterranean zone of central Chile over the medium term. However, they also indicate that additional data sets are needed to redefine the parameter distributions in the model and thus to predict trends in SOC and N stocks in the future.
    Agriculture Ecosystems & Environment 01/2011; 140(1-2):123-136. DOI:10.1016/j.agee.2010.11.019 · 3.20 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 04/2014; 7(2). DOI:10.1002/eco.1401 · 2.63 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; DOI:10.1093/jpe/rts022 · 2.28 Impact Factor