The Impact of Lake Bonneville and Lake Lahontan on the Halophytes of the Great Basin

Abstract

Brazil has over 8000 km of coastline and 1,085,187 km 2 of drought-affected areas where natural processes and land-use changes originated extensive salt fl ats. Brazilian coastal salt fl ats are found as transition zones of mangrove forests or salt marshes and dry upland areas, and they are located above the mean level of the spring tides, either in semiarid or in seasonally dry coasts. The salt fl ats' distributions are irregular, covering 1–24.4 % of the studied intertidal areas. Their sandy soils show salt con-tents near the seawater values and can increase to 150 ppt during the dry season. Dominant plants are widespread species more frequently found in tropical parts of South America. Halophytic forbs and grasses cover the mid-littoral and hypersaline gaps of the mangrove, whereas mixed stands with sedges occur when seasonal superfi cial fresh water drainages allevi-ate soil salinity. Although there are very few records of halophyte utilisa-tion, intertidal crabs are important for the estuarine food web and exploited by indigenous peoples and fi shermen for human consumption. Salt pans and shrimp farming are the most common anthropogenic activities that occur within salt fl at areas. Inland salt fl ats are common in low annual rainfall (500–800 mm) areas of the northeast region of Brazil. The stony soils with sodium character promote natural formation of salt fl ats. Low rainfall, a high water defi cit and careless irrigation management can estab-lish very quickly secondary salinisation in these soils. Surface soil saturate extract of natural and manmade salt fl ats can average 8–40 dS m −1 CE values during the drought season. The dominant cover of inland salt fl ats includes few native halophytic forbs and exotic shrubs and grasses,