Dynamics of soil organic carbon and its fractions after revegetation on sand dunes in the Tengger Desert, Northern China

Abstract:

Revegetation has become increasingly important for desertified land restoration in arid and semiarid regions. Little is known about the dynamics of soil organic carbon (SOC) after the establishment of shrubland on shifting sand dunes; especially the changes in SOC fractions following planting were poorly understood. 0-10 cm soil samples were collected along chronosequence plots were to: (1) quantitatively analyze the changes of SOC and its fractions over time following the establishment of shrublands on shifting sand dunes; (2) precisely assess the relative contribution of different components to total organic carbon at different times. The results showed that revegetation can promote SOC accumulation in desert regions. SOC increased from 0.33±0.11 g kg^-1 in mobile sand dunes to 5.08±0.11 g kg^-1 in 57-year shrublands, while the light fraction of organic C (LF-OC) ranged from 0.05±0.02 g kg^-1 to 2.96±0.24 g kg^-1, the dissolved organic C (DOC) increased from 5.95±0.42 mg kg^-1 to 23.63±2.79 mg kg^-1 and microbial biomass C (MBC) from 6.54±1.64 mg kg^-1 to 135.35±19.49 mg kg^-1. Their dynamics patterns can be divided into three stages, i.e. slow increase, fast increase and slow increase stages; especially, both SOC and its fractions showed no significant changes in the first 14 years, which suggested that soil restoration is a slow process in dry environments, and therefore the maintenance of soil habitat is a crucial for land management.

Our results also demonstrated that revegetation can increase the ratio of labile to stable pools in desert regions. Although, the content of HF-OC significantly increased after afforestation, but its contribution to SOC decreased from 85.15% to 41.52%, implied that more SOC stocks were stabilized in labile pools with the elapse of time, this would give rise to the risk of significant SOC losses caused by potential global warming and human-induced disturbances.