Influence of variable organic matter retention on nutrient availability in a 10-year-old loblolly pine plantation

Abstract

The effects of varying forest floor and slash retention at time of regeneration were evaluated 10 years after the establishment of a loblolly pine plantation near Millport, Alabama. Treatments included removing, leaving unaltered, or doubling the forest floor and slash material. Forest floor and litterfall mass and nutrient concentrations, available soil N, foliar nutrient concentrations and stand yield were all impacted by the treatments. Forest floor mass and nutrient contents in the doubled treatment were significantly greater than the other two treatments. The doubled treatment accumulated 25, 45 and 350% more forest floor mass and 56, 56, and 310% more N than the control treatment in the Oi, Oe, and Oa layers, respectively. The other nutrients followed similar patterns. Potentially mineralized NO 3 −-N in the mineral soil was also significantly higher in the doubled treatment. The positive effect of doubling the forest floor on soil N availability was reflected in greater foliage production, 30% more litterfall and 25% more stand yield for this treatment. This study shows that increasing the forest floor retention has resulted in increased nutrient availability and improved tree growth.