Carbon and nitrogen stocks through time in abandoned croplands of the Comarca Lagunera, Mexico

Croplands in the Comarca Lagunera region of Mexico are undergoing abandonment due to water scarcity. The effects of vegetation succession following cropland abandonment on soil organic carbon (SOC) and total nitrogen (STN) stocks have been poorly studied although such effects have important implications for terrestrial carbon pools and the global carbon cycle. This study sought to determine the organic carbon and total nitrogen content in soil at two depths (0-30 cm and 30-60 cm) and the successional biomass with a chronosequence of 2, 15, 25, and 35 years of restoration after cropland abandonment, as well as uncultivated areas of native micmphyllous desert scrub vegetation used as reference (Ref). Results revealed that the ecological succession 35 years after cropland abandonment resulted in high dominance by the species Prosopis glandulosa. Because of that, the latest stage since cropland abandonment (35 years) contained about three times more carbon and nitrogen (2.64 Mg C ha(-1) and 0.62 Mg N ha(-1), respectively) in aboveground biomass than reference areas (0.94 Mg C ha(-1) and 0.21 Mg N ha(-1), respectively). In contrast, soil carbon tended to decrease as years of abandonment increased. Thus, areas with 35 years of abandonment, although having high aerial carbon content, had the lowest soil carbon accumulation. Soil organic carbon and total nitrogen content showed no significant differences between the sampling depths in the investigated sites during the restoration time. These findings suggest that soil carbon accumulation after cropland abandonment through unmanaged ecological succession is difficult to achieve in this area.

Automated summary

Crop abandonment due to water scarcity in the Comarca Lagunera region of Mexico leads to vegetation succession, which has effects on soil organic carbon and total nitrogen levels. This study found that 35 years after abandonment, there was a high dominance of Prosopis glandulosa species, resulting in three times more carbon and nitrogen in the aboveground biomass compared to reference areas. However, soil carbon tended to decrease with increasing years of abandonment, suggesting that achieving soil carbon accumulation through unmanaged ecological succession is difficult in this area.