Whole-tree and forest floor removal from a loblolly pine plantation have no effect on forest floor CO 2 efflux 10 years after harvest

Abstract

Intensive management of southern pine plantations has yielded multifold increases in productivity over the last half century. The process of harvesting merchantable material and preparing a site for planting can lead to a considerable loss of organic matter. Intensively managed stands may experience more frequent disturbance as rotations decrease in length, exposing the stands to conditions that favor decomposition. To better understand the effects of organic matter removal on forest floor CO 2 efflux ( S ff), we measured S ff quarterly in 2001 in a 10-year-old loblolly pine ( Pinus taeda L.) plantation in eastern North Carolina that received different harvest and site preparation treatments. The treatments examined were removal of merchantable bole (OM 0) and whole-tree and forest floor removal (OM 2). The organic matter removal treatments did not affect soil moisture or soil temperature, the major variables that control seasonal fluctuations in S ff. Mean S ff ranged from 2.23 to 6.63 μmol m −2 s −1 and there were no significant differences between the treatments, despite higher lateral root mass in OM 0 (1552 ± 427 g m −2) versus OM 2 (701 ± 86 g m −2). In both treatments, S ff did not correlate to root mass directly beneath each measurement chamber. In OM 0, S ff had a negative relationship with distance from the nearest tree, while OM 2 showed no effect of tree proximity. Whole-tree and forest floor removal during harvest and site preparation did not result in differences in S ff or soil C, 10 years after establishment. Both treatments resulted in a greater quantity of soil C, indicating that the disturbance associated with harvesting enhanced soil C, at least over the short term. We attribute this increase in soil C to rapid decomposition of previous stands root system.