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Provides comprehensive coverage of the importance and utilization of halophytes to compensate the demand of food in whole world especially in the dry regionsContains insights from ecological to molecular fields Includes edible halophytes as well as those that enhance food-producing eco-systemsPresents information for improving abiotic stress tolerance in plants
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2 Multi-Temporal Soil Salinity Assessment at a Detailed Scale for Discriminating Halophytes Distribution
Jorge Batlle-Sales, Juan Bautista Peris and María Ferrandis, Department of Vegetal Biology, University of Valencia, Valencia, Spain A multi-temporal survey of soil salinity in a salt lake, recolonized by halophytes, was performed using electromagnetic induction (EMI) providing volume integrated values of soil apparent electrical conductivity (ECa). Inventories of plant communities were recorded according to the Braun-Blanquet method. In each of six areas monospecific with Suaeda vermiculata, Suaeda vera, Sarcocornia fruticosa, or Arthrocnemun macrostachyum, ECa was measured intensively in two seasons. Mean and range of ECa differ for each plant community. Soil was sampled in the six areas and analyzed for ion composition of the soil saturated paste extract. The electrical conductivity of the saturated paste extract (ECe) and soil properties were used for calibrating the EMI signals producing maps of predicted ECe at three incremental depths of 30 cm and maps of prediction error. Halophyte communities have been related to soil salinity in a geographical information system (GIS) as a tool for recommendations for plant restoration of the area. Keywords
Electromagnetic induction; geostatistics; GIS; halophytes zonation; soil salinity gradients 2.1 Introduction
The salt lake of Salinas (Alicante, Spain), zone object of this study, with centroid in N38° 30.196' W0° 53.195', is the bottom part of an endorreic watershed where both runoff waters and subterranean water fluxes accumulate. The lake, with an extension of 2.93 km2, is surrounded by several glacis and its bottom part is constituted by geological materials of the Keuper Germanic facies, with clays and gypsiferous layers dominating (IGME, n.d.), which are the source of chloride, sulfate, sodium, and magnesium ions found in the saline groundwater. Existing historical documents (Arroyo-Ilera, 1976) report that the lake was used for salt extraction since the seventeenth century, with this activity interrupted during the eighteenth century and restarted again in the twentieth century. The semiarid climate of the area, with annual precipitation of 404 mm, average temperature of 15.6°C (Figure 2.1) and very dry summer, allows for water concentration and solute precipitation by evaporation. In 1922 works were started for desiccating the lake and in 1948 regular salt extraction by evaporation of the saline runoff and drainage waters that reached the lake was commenced. Later, the overexploitation of proximal irrigation wells depleted the groundwater level, leading to the desiccation of the lake and hence, in 1952, ceasing the salt extraction activity.
Figure 2.1 Climogram of Salinas. Mean monthly data for precipitation (mm) and temperature (°C). In an aerial photograph from 1956 (Figure 2.2) (IGN, 1956), the existence of a residual salt layer that was later partially collected is evident. The residual soil salinity distribution was investigated by Batlle et al. (1994) and Pepiol et al. (1998), recognizing the composition and mineralogy of salt efflorescence and the distribution of salts at different depths in the soil, producing thematic maps. The soils are classified as gypsic aquisalids (Soil Survey Staff, 2014a), with massive accumulations of halite, gypsum, and calcium carbonate. Several botanical studies were realized in the zone (Rigual, 1972; Serra Laliga, 2007) and carried out in detail by Peris et al. (1999).
Figure 2.2 Aerial photograph from 1956 showing the salt exploitation in the Salinas Lake. 2.2 Objective
This study focused on the recognition of the soil conditions and salinity levels that determine the adaptation of different halophyte species, as a basis for recommendations of plant restoration of the area. The methodology adopted used measurement of soil salinity gradients in the former lake area, performing electromagnetic induction (EMI) surveys, botanical inventories, as well as soil sampling and analysis. 2.3 Methodology
2.3.1 Area of Study
The area selected for study was the south-east (SE) part of the salt lake that has undergone evident change from its appearance in the visual documents of 1956. This change includes the “soil construction” by formation of dunes and accumulation of particles transported by wind and the progressive colonization of the area by halophytes. Figure 2.3 presents the current aspect of the area: the slopes of glacis, with thick crusts of calcium carbonate, are cultivated under irrigation with waters of good quality, in most cases by drip irrigation; the bottom part of the watershed, that constitutes the former salt lake, showing bare saline soil areas colonized progressively by halophytes. In the SE border of the lake the “soil construction” is an active process by formation of dunes by wind transport of soil particles. At the times of salt exploitation, the soil surface was sealed by a salt layer, formed by evaporation of the brine. After ceasing of salt mining, the salt crust was taken as a residual product. The soluble salts at the soil surface started to slowly leach downwards into the soil. The formation of crusts in the surface, by quick evaporation of soil solutions that arrived by capillary ascent, further impedes the arrival of solutions due to capillary disruption, giving “fluffy” micro-relief, with a soft and loose surface layer of several millimeters that is highly erodible by wind. In the study area the soil particles of this layer are transported by the winds of dominant orientation from WNW–ESE. Seeds of the most salinity-tolerant halophytes (mainly Arthrocnemun macrostachyum) enter the soil cracks and, after growth, reduce the wind speed, thereby promoting the deposition of particles transported in suspension after the plant, hence starting the dune formation process visible in Figure 2.4.
Figure 2.3 Photograph of Salinas in May 2014, showing the glacis cultivated and the bottom part of the salt lake, partially colonized by halophytes.
Figure 2.4 Formation of dunes with soil particles transported by wind, in May 2014. This “soil construction” by the frequent windy conditions in the zone gives additional opportunities for colonization to other plant species that are less salt-tolerant. The upper part of the “constructed soil” has high permeability and the soluble salts can be leached more effectively from a layered and compacted soil. It is very important to assess the existing salinity conditions that allow the plants to germinate in order to understand how the colonization process proceeds. 2.3.2 Design of the Soil Survey and Vegetation Inventories
A geographical information system (GIS), based on ETRS89 ellipsoid and UTM projection, was implemented with the following information available for the area: aerial geo-referenced orthophoto from 2012 (30 cm of resolution) (ICV, 2012), Lidar EDM (ICV, 2009), geological maps (IGME, n.d.), and previous information about soils (Batlle et al., 1994; Pepiol et al., 1998) and plants (Peris et al., 1999), as well as our own unpublished information. The software used was Quantum GIS (2011). The photointerpretation of the aerial orthophoto suggested the existence of “vegetation bands” arranged along a topographical gradient, until the center of the lake, with bare soil. A series of survey transects were planned perpendicular to this topographical gradient, from an altitude of 474.5 to 472.7 m (lowest part of the salt lake). Four survey campaigns were completed on October 24, 2013 (first EMI survey), November 5, 2013 (second EMI survey with botanic inventories), May 7, 2014 (intensive EMI survey and soil sampling in six selected areas) and July 24, 2014 (intensive EMI survey in the six selected areas). Points of measurement (dots) and position of soil sampling (PI, PII, PIII, PIV, PV, and PVI) are represented in Figure 2.5.
Figure 2.5 Points of EMI measurement and situation of the six soil profiles (PI–PVI) into the six monospecific areas selected for intensive EMI measurement. 2.3.3 Plants Inventory
During the EMI survey of November 5, 2014, sampling of plants was done and 81 botanical inventories were annotated according to the Braun-Blanquet methodology (Braun-Blanquet, 1964), recording the total area in square meters, percentage of area coverage and the values of ECa provided by the EMI device for two dipoles arrangements (EMv and EMh). Six monospecific botanical inventories were selected for more detailed EMI and soil sampling research: Suaeda vermiculata (one area, PI), Suaeda vera (one area, PII), Sarcocornia fruticosa (two areas, PIII and PVI) and A. macrostachyum (two areas, PIV and PV). 2.3.4 Soil Sampling and Analysis
Composite soil samples were taken by soil augering at depths of 0–30, 30–60, and 60–90 cm, in each of the six selected points of monospecific plant inventories, PI–PII–PIII–PIV–PV–PVI (Figure 2.5). Field tests were performed for soil texture by hand, including presence of solid carbonates (effervescence with 6 M HCl),...
