Pablo J. Bouza

A Characterization of Patagonian Salt Marshes

We combined literature reviews with an analysis of regional cartography, aerial photographs, and satellite images to identify the locations of heretofore-unknown salt marshes along the Patagonian coastline of Argentina. Subsequent ground surveys confirmed the presence of the marshes. While numerous sites still require verification, our surveys confirmed the existence of 27 large coastal salt marshes, which had estimated areas of between 3 and 2400 ha distributed along ∼225 km of coastline. We described the major patterns of landscape physiognomy and community structure at eight of these sites. We classified these marshes as either muddy or rocky marshes, and subdivided them into Spartina and Sarcocornia marshes depending on the dominant vegetation. Muddy marshes were the most common type and showed a clear regional pattern with Spartina-dominated communities in the north (≤ 42°S) and Sarcocornia-dominated systems in the south (≥ 42°S). Plant height and standing crop biomass tended to be lower at higher latitudes, but plant cover showed the opposite trend. Spartina marshes had a more diverse marine macro-invertebrate fauna than Sarcocornia marshes, when the two marsh types occur at similar latitudes. Although the diversity of invertebrates was relatively low along the entire latitudinal range, most marshes supported unique species assemblages.

Micromorphological, physical, and chemical characteristics of soil crust types of the central Patagonia region, Argentina

Abstract The objectives of this work were: (i) to document the micromorphological, physical, and chemical properties of soil crusts types; and (ii) to determine the factors that control crust formation. Soil crusts as Av‐horizons were studied in three different soil classifications: Typic Calciorthid, Typic Haplargid, and Typic Natrargid. The Av‐horizons showed common characteristics such as high silt and low organic matter contents. The high exchangeable sodium percentage (ESP) is considered the main cause of crust formation in the Av‐horizons of the Haplargid and Natrargid. The crusts lying below the desert pavement consist of an upper zone of laminated sands, silts and clays, large vesicles, and a very dense lower zone with few and small vesicles. The size of the vesicles differ greatly among the three studied crusts. The vesicular layers of the Natrargid are more developed than of other soils. The typical shape of vesicles is rough walled on the upper half and smooth at the bottom. The walls of larger...

Trace metal concentrations in Spartina densiflora and associated soil from a Patagonian salt marsh.

The objectives of this study were to (i) assess in situ trace metal concentrations in soil and in Spartina densiflora in a Patagonian salt marsh (Rawson, Chubut, Argentina) and (ii) investigate the relationship between trace metal concentrations in soils and in plants to improve our knowledge regarding the ability of S. densiflora to take up and accumulate trace metals from the soil within its native region. Our results indicate that the soil and S. densiflora exhibit low metal concentrations in the Rawson salt marsh. S. densiflora accumulates Zn in below- and above-ground plant structures and Cr in below-ground parts. These results suggest at the time of this study there is scarce human impact associated with metals in the Rawson salt marsh.

Erosion of subsurface horizons in Northeastern Patagonia, Argentina

Degradation processes and their association with spatial and lithological discontinuities in argillic horizons of nine profiles in northeastern Chubut province were examined. Twelve test pits were used as stratigraphic controls. The reconstruction of the upper limit of the argillic horizons and its position in relation to the soil surface was performed in different topographical positions. Lateral discontinuities may have been due to the erosion of surface and argillic horizons in the intermound area, or to the development of desert pavements and vesicular layers, which may or may not be buried. The lithological discontinuities that were not associated with the erosion processes may be caused by (1) profile development on different parent materials, as a result of lateral facial variations, (2) development of different profiles under different conditions of moisture as related to paleomicrorelief. The observed shapes of the argillic horizons associated with water erosion suggest that the surface peds of t...

Accumulation and distribution of trace metals within soils and the austral cordgrass Spartina densiflora in a Patagonian salt marsh.

Concentrations of Cd, Cu, Fe, Pb, and Zn were determined in soils and in below- and above-ground structures of Spartina densiflora in a Patagonian salt marsh (San Antonio, Río Negro, Argentina). Also, the relationship between trace metal concentrations in soils and plants was investigated to improve our knowledge regarding the ability of this plant species to take up and accumulate trace metals from the soil. Our results indicate that, within the studied salt marsh, soil trace metal concentrations follow a decreasing concentration gradient toward the sea. They show moderate pollution and a potentially negative biological effect in one site of the salt marsh. While below-ground structures reflect the soil metal concentration pattern, this is not so evident in above-ground concentrations. Also, S. densiflora is able to absorb a limited amount of metals present in the soil, the soil bioaccumulation factor being lower in sites where soil metal concentration is higher.

Formation, Distribution, and Physicochemical Properties of Plant Litter in Shrub Patches of Northeastern Patagonia

The objective of this study was to assess the formation, distribution, and physicochemical properties of litter in two types of shrub patches, featured by the dominant species (Atriplex lampa and Prosopis alpataco). These species are important components of the Monte Phytogeographic Province . The surface layers of the shrub-steppe have been classified into four soil condition classes using attributes that are easily observable in the field. These classes provide an estimate of litter spatial patterns and of potential dry matter production. Litter differs greatly in chemical content. The P. alpataco patch presents higher quality in organic matter , based on its elemental composition of carbon , nitrogen , and phosphorus . The patterns of the lignin studied in both patches were different . The sum of phenolic oxida tion species was higher in summer for P. alpataco than in A. lampa, indicating higher contents of lignin components in the former and a slight oxidation in the latter . The strongest peaks in 1 ...

Flooding Effect on the Distribution of Native Austral Cordgrass Spartina densiflora in Patagonian Salt Marshes

ABSTRACT Idaszkin, Y.L.; Bortolus, A., and Bouza, P.J., 2014. Flooding effect on the distribution of native austral cordgrass Spartina densiflora in Patagonian salt marshes. Plant zonation is one of the most conspicuous ecological features of salt marshes worldwide. In Patagonian salt marshes the cordgrass Spartina alterniflora forms dense monospecific stands along the lowest marsh level, while the higher levels are dominated by Spartina densiflora or Sarcocornia perennis. In this study, we coupled field transplants combined with neighbor exclusion treatments and greenhouse experiments to evaluate the effect of submersion and waterlogged anoxic soil in the determination of the lower distribution limit of S. densiflora in Central Patagonian salt marshes within its native range. In the field experiment, no S. densiflora survived the frequent tidal submersion by approximately 2 m of seawater in the low marsh, independent of the S. alterniflora neighbors presence, while in the greenhouse experiment, all plants were able to tolerate strongly reducing soil conditions. Our results suggest that the absence of S. densiflora in the low marsh level is a consequence of the effect of the submersion, independent of the presence of S. alterniflora neighbors and of the strong soil anoxia. Our results contribute to optimize the efforts addressed to control or eradicate this exotic species in salt marshes where it is invading.

Groundwater salinization in arid coastal wetlands: a study case from Playa Fracasso, Patagonia, Argentina

The origin of the high salinity in the groundwater of a coastal wetland in an arid climate was studied in the Playa Fracasso marsh, located on the northwest coast of the extra-Andean Patagonia. Research was carried out by means of the design of a network of soil pits and short piezometers in the marsh and the surrounding landforms. Continuous fluctuations of the water table, in situ physical and chemical properties, major ions (Ca2+, Mg2+, Na+, K+, Cl−, SO42−, HCO3−) and stable isotopes (18O and 2H) in groundwater, as well as soil salinity, were measured. The combined analysis of the hydrodynamics, the ion ratios rCa2+/rCl− and rMg2+/rCa2+ vs. rCl− and the isotopic composition made it possible to recognize an area within the high marsh in which the origin of groundwater is mainly marine and another in which the contributions are of mixed origin. By means of the analysis of rCl− vs. δ18O, a salinization process with no change in isotopic composition was identified. Its interpretation, together with those of the soil salinity profiles and the records of the fluctuations in electrical conductivity associated with extraordinary tides, was used to define a conceptual model of salinization which could be useful to understand other coastal wetlands under similar arid climatic conditions. It consists in a cyclical mechanism of evapotranspiration, precipitation, dissolution and transport of salts during tides.

Comparison of phytoremediation potential capacity of Spartina densiflora and Sarcocornia perennis for metal polluted soils

Phytoremediation is considered the most appropriate technique to restore metal polluted soil, given its low cost, high efficiency and low environmental impact. Spartina densiflora and Sarcocornia perennis are perennial halophytes growing under similar environmental conditions in San Antonio marsh (Patagonia Argentina), therefore it is interesting to compare their phytoremediation potential capacity. To this end, we compared concentrations of Pb, Zn, Cu, and Fe in soils and in below- and above-ground structures of S. perennis and S. densiflora. It was concluded that both species are able to inhabit Pb, Zn, and Cu polluted soils. Although Sarcocornia translocated more metals to the aerial structures than Spartina, both species translocated only when they were growing in soils with low metal concentrations. It seems that the plants translocate only a certain proportion of the metal contained in the soil. These results suggest that both species could be considered candidates to phytostabilize these metals in polluted soils.

Soil–Geomorphology Relationships and Pedogenic Processes in Península Valdés

The soil landscape of the Peninusla Valdes region is review based in soil genesis analysis and soil–geomorphic relationships. The main soil types of the study area are grouped into two Soil Orders: Aridisols and Entisols. The oldest geomorphic surface corresponds to a relict terrace level from the Rodados Patagonicos lithostratigraphic unit, with Xeric Petrocalcids—Xeric Haplocalcids soil complex. Pleistocene landforms as youngest terrace levels, piedmont pediments (endorheic basins and coastal zone), and paleo-beach ridge units, an intricate soil distribution pattern occurs. This soil distribution is registered by a soil complex constituted by Natrargids, Natrigypsids, Calciargids and Haplocalcids, all of them with xeric regime soil moisture. In playa lakes of the endorheic basins, the soils were classified as Calcic Aquisalids. The Entisols are developed on Holocene geomorphic surfaces; Xeric Torripsamments in stabilized aeolian fields, and Typic Torriorthents in bajadas (coalescing alluvial fans associated to piedmont pediments). In salt marshes, geomorphic elements, anoxia degree, and vegetation communities are associated to soil type; Haplic Sulfaquents, Sodic Endoaquents and Sodic Psammaquents, are related to the low salt marsh, while Typic Fluvaquents and Sodic Hydraquents are developed in the high salt marshes. The main pedogenic processes registered in the Peninsula Valdes soils are clay illuviation, calcification, gypsification, and sulfide production—sulfidization. As the calcretization process progresses, a transformation and neoformation of clay minerals occurs in the following sequence: smectite—palygorskite—sepiolite. The isotopic composition of δ13C y δ18O in pedogenic carbonate could be used as paleoecological and plaeoclimate proxy indicators, respectively.