HENDERSON LONG-TERM SITE PRODUCTIVITY STUDY The Henderson Site Productivity Study is internationally recognized as one of the few studies in the world where the effects of plantation management practices have been intensively studied for a whole rotation at one site. The study, located in the Piedmont of North Carolina on International Paper Co. land, was established in 1980. Following detailed pre-harvest assessments in the existing second rotation stand, eight regeneration treatments were imposed including of different levels of harvest utilization, site preparation, and vegetation management. Planted pines have been measured annually for the last 23 years. In addition, many other processes have also been assessed during this 3rd rotation including soil physical and chemical properties, N mineralization, forest floor dynamics, litterfall, non-pine vegetation biomass, and plant community dynamics. Fifteen graduate students have been involved with research at the site and over 30 publications have resulted. Results have described what has happen but more importantly have provided a better understanding of the mechanisms underlying sustainable productivity. Key results to-date: Vegetation control (hardwood and herbaceous) has resulted in a doubling of pine production. Harvest intensity has had no effect on stand productivity. All but one of 24 plots are exhibiting higher site index values this rotation than in the previous rotation. Above-ground production has been greater in the pine plantation than the mixed pine-hardwood stands. Soil N mineralization rates peaked immediately after harvest on all treatments and dropped rapidly and have remained at low levels (<30 lbs/acre/year) since age 5. Organic matter and nutrient displacement associated with piling has had no effect on stand growth and little impact on N-mineralization. Apparently, the beneficial effect of disking on pine survival and hardwood control has more than compensated for any negative effects of nutrient removals associated with piling. Soil physical properties exhibited partial recovery in the surface soil of skid trials at age 12. Intensive site preparation and vegetation control treatments resulted in early differences in the species composition of the plant communities; however, by late in the rotation, these differences were no longer evident. Although, species numbers were not affected, strong differences in stand structure were apparent. Although much has been learned, considerable work is left to wrap-up this 3rd rotation and start the next. Plans are to provide a final characterization of the effects of the 3rd rotation treatments on: biomass, carbon, and nutrient pools in the vegetation (above and below ground), forest floor and mineral soil, carbon and nitrogen fluxes into, out of, and within the forest floor and mineral soil (A and B horizons), soil microbial communities in the forest floor and mineral soil, and soil physical properties.