Soil properties in 35 y old pine and hardwood plantations after conversion from mixed pine-hardwood forest

Past management practices have changed much of the native mixed pine-hardwood forests on upland alluvial terraces of the western Gulf Coastal Plain to either pine monocultures or hardwood (angiosperm) stands. Changes in dominant tree species can alter soil chemical, biological, and physical properties and processes, thereby changing soil attributes, and ultimately, soil functions. Restoring these forests may be slow or difficult if soil function is altered appreciably. We studied the soil properties and processes in pine or hardwood-dominated stands after 35 y since conversion from a mixed pine-hardwood stand. The pine forest floor biomass was about twice as great as that of the oak stands, the oak soils were 2030 wetter than the pine soils throughout the sampling period, the oak soils released more CO2 through respiration and had higher rates of N mineralization in the summer. We observed few differences between pine and oak stands in soil chemistry or microbial biomass. Since the difference in forest floor depth and soil biological activity may confer competitive advantages or disadvantages to some species, this study supports the hypothesis that pine- or hardwood-only stands create functionally different soils on these site types after 35 y.