Effect of Thinning on Aboveground Biomass Accumulation and Distribution in Naturally Regenerated Shortleaf Pine

Abstract The accumulation and relative distribution of standing biomass to different aboveground tree components was investigated in 46–53-year-old naturally regenerated shortleaf pine (Pinus echinata Mill.) stands growing in the Ouachita Mountains of southeastern Oklahoma that were thinned to different levels 16 years previously. The thinning levels were 50% full stocking, 70% full stocking, and a 140% full stocking unthinned control. After 16 years, the unthinned controls had more total aboveground biomass, bole wood, bark, and foliage standing biomass per hectare but had less branch standing biomass than the more heavily thinned stands. Foliage biomass as a proportion of total stand biomass was similar among the three treatment levels. Bark biomass proportion was significantly less in thinned to 50% treatment compared with the other treatments. Bole wood biomass proportion in thinned to 50% treatment was significantly less than in the control. The proportion in branches was significantly greater in the thinned treatments compared with the proportion in the unthinned control. These results suggest that thinning increases biomass distribution to branches at the expense of stems, after 16 years of postthinning stand growth.