Effects of Large Macropores on Saline Water Evaporation From Marsh Soil

Abstract

AbstractMacropores such as crab burrows are a common feature of salt marsh sediment and are recognized as an important factor influencing pore‐water flow in salt marshes. In this study, we examined the effect of macropores on saline water evaporation and pore‐water salinity based on laboratory experiments and numerical simulations. Soil columns with and without an artificial macropore were packed with clay‐loam and were set with different hydraulic heads fixed at the bottom. The results showed that increase in pore‐water salinity significantly reduced evaporation rates. The preferential flow induced by macropores recharged the soil surrounding macropores and maintained higher evaporation rates in comparison with homogeneous soil without macropores. As macropores induced lateral flow, the pore‐water salinity in shallow soil around the macropores was reduced but that in the area away from the macropores was increased. These impacts were more remarkable on the soil layers with higher hydraulic heads. A sensitivity analysis showed that with a higher initial pore‐water salinity, the macropore's impact on soil evaporation rates was more remarkable for both clay‐loam and silt‐loam. These results revealed the effect of macropores on soil evaporation processes and soil conditions, and also shed light on associated biogeochemical processes in salt marshes.