Pine plantations on reclaimed minelands: Site index, allometry, and carbon sequestration in woody biomass

Strip-mining is a common practice in the Gulf Coastal Plain, with some individual mines spanning over 5,000 hectares. Federal surface mining regulations require land be restored to a productive state capable of supporting pre-existing land-uses. Loblolly pine (Pinus taeda L.) plantations are a widespread reclamation land-use in east Texas; however, the productivity of these plantations compared to those on unmined lands is not well-documented. The first objective of this study was to quantify current site quality of loblolly pine plantations on two mines as compared to stands on unmined soils. The two mines differ in the method of overburden replacement. Substituting mixed overburden for topsoil generally results in no distinction of original soil layers following reclamation (Beckville Mine), while removing and mixing the pre-mining upper, oxidized soil layers for topsoil in the post-mining reclamation areas creates some stratification (Oak Hill Mine). Non-linear modeling of stem analysis data indicated the current site indices are 18.6 and 18.9 m at 25 years for Beckville Mine (mixed overburden) and Oak Hill Mine (mixed oxidized material), respectively. Pre-mining site indices were approximated from soil surveys at 21.3 (Beckville Mine) and 20.1 m (Oak Hill Mine). The current site indices (post-mining) for each mine did not differ statistically from pre-mining site indices, nor was height statistically different between pre-mining and post-mining at any age. The two mine sites did not statistically differ by height at any age, nor were site index model parameters statistically different. Site index calculated from both mines' data was found to be significantly lower (p < 0.05) than east Texas' average site index of 21.6 m at 25 years.