Effect of Soil Salinity on Labile Carbon Pools in a Naturally Saline, Sandy Loam Soil.

Soil salinization is a major threat to agricultural ecosystems. Consequently, an understanding of agro-ecosystem functions affected by increasing levels of soil salinity is critical for land management. The purpose of this study was to examine the effects of soil salinity on microbial-mediated carbon fluxes and labile carbon pools in a naturally saline, sandy loam soil. Soil samples were collected from a depth of 0 to 15 cm, and the salinity of each sample was estimated by the electrical conductivity of a saturated paste extract (EC_e).  Fifty grams of each air-dry, ground soil sample was placed in an incubation chamber and brought to 50% water holding capacity (WHC). Soil respiration was estimated using the GasHound CO₂ analyzer over a period of 45 d. Measurements were taken on day 1, 5, 10, 25, 35, and 45 of the study. Preliminary results indicated that the highest average cumulative CO₂-C fluxes from the soil were at intermediate levels of soil salinity, whereas the lowest fluxes were observed at the highest levels of salinity. Labile C, estimated by CO₂-C fluxes from the soil, was significantly correlated with EC_e at low values of salinity (EC_e < 2.5 dS m^-1). Multiple linear regression analyses indicated that at relatively low EC_e, labile C was significantly influenced by salinity, silt content, and sand content, whereas at relatively high EC_e, labile C pools were influenced by the presence of soil organic matter (SOM) and clay content.