Tree Invasion Effects On Soil Organic Carbon of Grasslands: A Gracenet Project.

Four tree densities were established in 1981 on native grass-dominated Houston Black soils near Riesel Texas.  The sites were sampled in 1981 and re-sampled in 2007 after 26 years of tree influence.  Soil organic carbon distribution and root distribution to a depth of 3-m was determined for both sample periods.  The 1981 soil carbon distribution indicated that the sites had been intensively tilled in the past.  Root distribution differences between 1981 and 2007 samples indicated rooting depths were usually shallower in the 2007 sampling period, possibly because of grazing being excluded during the study period.  Comparisons of soil organic carbon distirbution will be discussed.