Soil Water Content at Harvard Forest HEM and LPH Towers 1998-2007

Water content of the top 20 cm of soil was measured using 1.5 inch diameter soil cores. Soil water content is of particular interest and importance in explaining patterns of soil respiration (including root respiration) and ecosystem respiration, 60 to 75% of which occurs below the ground surface at Harvard Forest. Soil water content in deciduous forest near the Little Prospect Hill Forest was in general found to be more variable than near the Hemlock tower. One influence contributing to this is the presence of a water table within 1 m of the soil surface near the hemlock tower, compared to a water table at unknown depth in the deeply drained soils in most parts of Little Prospect Hill. Relatively low evapotranspiration at the Hemlock tower site during the period when deciduous trees are foliated also contributes to higher water content in soil there, and a relatively thick surface organic layer. These influences tend to maintain soil respiration at higher levels in the hemlock forest during dry summers, but excessive moisture in the soil at the Hemlock site during very wet summers appears to suppress soil respiration.