Soil Solution Phosphorus Dynamics in a Whole-Tree-Harvested Northern Hardwood Forest
Forest harvest drastically alters nutrient cycling, yet stream water and mineral-soil solutions typically show little change in P concentrations after forest disturbance. Changes in P availability and movement are more likely to be detected in forest-floor solutions, since P can be strongly sorbed in soil. Tension-free lysimeters were used to compare forest-floor and mineral-soil solution total-P concentrations in whole-tree-harvested and undisturbed forest sites for 2 yr after harvest in the Hubbard Brook Experimental Forest in New Hampshire. Mean total-P concentrations in solution in the forest floor (Oa horizon) were significantly higher in whole-tree-harvested sites (248 µg P L−1) than in undisturbed forest sites (67 µg P L−1), presumably due to reduced plant uptake of P. Mean P concentrations in mineral-soil solution remained low after whole-tree harvest (32 µg P L−1 in the Bh and 15 µg P L−1 in the Bs), consistent with the high P-sorption capacity of the mineral soil. Phosphorus flux in soil solution from the Oa to the B horizon, calculated from monthly mean P concentrations and monthly water flux simulated by a hydrologic model, was greater in whole-tree-harvested sites (1.0 kg P ha−1 yr−1) than in undisturbed forest sites (0.3 kg P ha−1 yr−1) in the first 2 yr after the disturbance. This redistribution of P from the forest floor to the mineral soil far exceeds stream-water export of dissolved P (0.02 kg P ha−1 yr−1) but is small compared with forest-floor stores (85 kg P ha−1).Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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