The variation of soil water regime, oxygen status and rooting pattern with soil type under Sitka spruce

Soil water regime, oxygen status and rooting pattern under Sitka spruce were characterized in five soil types: a waterlogged peaty gley, a peaty gley, a flushed peaty gley, a surface water gley and a brown forest soil during 1982. The waterlogged peaty gley had a high water-table which only dropped below 30 cm depth for 46 d during the summer. Below the water-table the profile was anoxic and rooting was restricted to a depth of 12cm. The peaty gley experienced seasonal waterlogging with a winter water-table around 15cm depth. Roots that grew further down the profile during the summer as the topsoil dried to –100 kPa matric potential were later killed when the water-table rose. The top 30 cm of the flushed peaty gley remained oxygenated even below the water-table. Roots survived below the winter water-table. The top 30 cm of the surface water gley and brown forest soil were freely draining and remained aerated throughout the year. The platinum electrode polarographic method demonstrated that there was a sharp transition to anoxic conditions just above the water-table at the first two sites.