Biogenic carbon accumulation across a cold desert dune chronosequence

Arid and semi-arid ecosystems constitute 30-40% of terrestrial biomes.  While productivity in deserts is low, the combination of long-lived shrubs, high root allocation, and low decomposition rates could result in significant stored ecosystem carbon (C).  We inventoried below-ground and above-ground C pools across a chronosequence of shoreline dune complexes at Mono Lake, California.  Spatial variation at the shrub island to interspace scale typical of deserts was incorporated with variation at the landscape scale across the chronosequence (49 to ~3000 years old).  We found soil organic carbon was the largest C pool at all sites ranging from 62-99% of total belowground organic C (TBOC).  TBOC increased over time, the youngest dune complex (5.3 kg C m^-2) stored significantly less than the oldest (17.2 kg C m^-2).  Soil inorganic C (SIC) followed a different pattern, with the 300-year-old complex (1785 kg C m^-2) having significantly higher SIC than the oldest (1108 kg C m^-2).  Landscape scale total organic carbon (TOC; including above- and below-ground C) accumulation rose to an apparent plateau by 300 years.  Concentrations of organic C were much higher in shrub islands but interspaces, because of their large area at the landscape scale, accumulated more TOC.  Large amounts of organic C accumulate in this cold desert ecosystem, however, total C storage decreases through time due to decreased SIC. These data indicate that modeling soil C pool dynamics at the scales represented by the chronosequence would help develop understanding of drivers of C storage and release in cold deserts.