Edaphic Characterization, Water and Salt Translocation in Saline Marsh at Local Scale in Songnein Plain, Northeast China

The degradation of saline marsh in Songnen plain was controlled by many factors. Based on in-situ observation and laboratory analysis, soil properties and matters translocation in Zhalong wetland at local scale as affected by freeze and thaw action was explored. Results show that within the study plot, 1500 m in distance, but varying only 80 cm in altitude, existed four types of soils i.e. Shallow-horizon Alkalic Halosols (SAH), Crust Alkalic Halosols (CAH) and Para-alkalic Dark-Aquic Cambosols (PDC) and Sodic Hapli-Orthic Gleyosols (SHG). High content total porosity with amounts to 62% in surface horizon in marsh would help to water conservation and wetland formation. In contrast, large rate of silt or clay in texture in alkali soil and meadow soil constrain the water content in topsoil, i.e. the saturated water content 0-30 cm horizon of meadow soil and alkali soil were merely 0.83 and 0.7 m3m-3. Residues & roots in surface layer of SHG expand the period of freezing phase as long as 9 months comparing to 7 months in SAH, and maximum freezing fringe in the former was 24 cm deeper than the latter (178 cm versus 154 cm). Seasonal freeze and thaw action has obvious influence on water storage in topsoil in saline marsh, leading different of soil succession therein. Soil moisture content in the surface layer of marsh increased from 2.05 to 2.62 m3m-3(over-saturated), but no obvious change in PDC and Alkali soils. In contrast, electrical conductivity of saturated paste in SAH and CAH increased from 6.5 to above 10 dS m-1. Therefore, it did not accord with the practical situation of Northeast China as that of strong evaporation was the only cause that caused saline marsh alkalinization. Protecting the vegetation or restoring surface coverage by plant in saline land in spring may help land dealkalization in high latitude arid & semiarid regions.

Lake Levels since about 40,000 Years Ago at Lake Chalco, near Mexico City

Diatoms, magnetic susceptibility, organic content, and14C ages of sediments from a 26-m core suggest that Lake Chalco, in the southern part of the basin of Mexico, went through a series of major fluctuations during the late Pleistocene and the Holocene. Before ca. 39,00014C yr B.P. the lake was very deep (about 8–10 m), alkaline, and saline. It then became shallow (<2 m) for most of the time between ca. 39,000 and 22,500 yr B.P. Chalco deepened to about 4–5 m about the time of a major eruption of nearby Popocatepetl volcano ca. 22,000 yr B.P. The lake remained relatively deep and fresh until ca. 18,500 yr B.P., when lower levels and alternating acidic to freshwater conditions were established. After 14,500 yr B.P. lake level rose slightly, but by ca. 10,000 yr B.P. Chalco became very shallow (<2 m), remaining as a low, alkaline saline marsh until ca. 6000 yr B.P. This period corresponds with the Playa cultural phase, during which the earliest human settlements in the basin were established. After ca. 6000 yr B.P. Chalco became a fresh to slightly alkaline shallow lake a few meters deep.

Late Pleistocene and Holocene Paleoenvironments of Chalco Lake, Central Mexico

In order to establish paleoenvironmental conditions during the late Quaternary, four cores from the Basin of Mexico (central Mexico) were drilled in Chalco Lake, located in the southeastern part of the basin. The upper 8 m of two parallel cores were studied, using paleomagnetic, loss-on-ignition, pollen, and diatom analyses. Based on 11 14C ages, the analyzed record spans the last 19,000 14C yr B.P. Volcanic activity has affected microfossil abundances, both directly and indirectly, resulting in absence or reduction of pollen and diatom assemblages. Important volcanic activity took place between 19,000 and 15,000 yr B.P. when the lake was a shallow alkaline marsh and an increase of grassland pollen suggests a dry, cold climate. During this interval, abrupt environmental changes with increasing moisture occurred. From 15,000 until 12,500 yr B.P. the lake level increased and the pollen indicates wetter conditions. The highest lake level is registered from 12,500 to ca. 9000 yr B.P. The end of the Pleistocene is characterized by an increase in humidity. From 9000 until ca. 3000 yr B.P. Chalco Lake was a saline marsh and the pollen record indicates warmer conditions. After 3000 yr B.P. the lake level increased and human disturbance dominates the lacustrine record.

Nitrogenous Compatible Solutes in Native South Australian Plants

Australian native flora was examined with nuclear magnetic resonance (n.m.r.) techniques for its content of nitrogenous compatible solutes. Plants were sampled from four habitats: two arid, one subhumid, and one saline estuarine marsh. Eight and two of the 15 plants in the subhumid area accumulated proline and glycinebetaine, respectively, whereas many of the plants in the two arid habitats accumulated these solutes. With only two exceptions plants in the saline marsh could be described as either proline accumulators (six species) or glycinebetaine accumulators (eight species). Attempts to correlate the glycinebetaine and proline contents with the relative water content (RWC) were not successful. Some plants accumulate compounds other than, or in addition to, proline or glycinebetaine, such as trans- 4-hydroxy-N-methyl-L-proline, which was accumulated in Melaleuca lanceolata. Exocarpos aphyllus accumulated an as yet unidentified compound.