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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATED INVASIVE SPECIES CONTROL, REVEGETATION, AND ASSESSMENT OF GREAT BASIN RANGELANDS

Location: Great Basin Rangelands Research

Title: Effects of Thinning, Residue Mastication, and Prescribed Fire on Soil and Nutrient Budgets in a Sierra Nevada Mixed-Conifer Forest

Authors
item Johnson, Dale -
item Walker, Roger -
item Glass, Dallas -
item Stein, Chad -
item Murphy, James -
item Blank, Robert
item Miller, Watkins -

Submitted to: Forest Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 21, 2013
Publication Date: N/A

Interpretive Summary: The effects of thinning followed by residue mastication (THIN), prescribed fire (BURN), and thinning plus residue mastication plus burning (T+B) on nutrient budgets and resin-based (plant root simulator [PRS] probe) measurements of soil nutrient availability in a mixed-conifer forest were measured. Because of site differences, removals of carbon (C) and nutrients by harvesting were greater in the T+B than in the THIN (Mg) treatment. Harvesting caused greater exports of C, phosphorus, potassium (K), calcium (Ca), and magnesium (Mg) than burning, harvesting and burning caused approximately equal exports of nitrogen (N), and burning caused greater exports of sulfur than harvesting. Burning caused greater volatilization losses of C and N from the T+B than from the BURN treatment because the addition of chips from mastication in the T+B treatment caused greater combustion of the native forest floor. The most significant effect of the chips on soil nutrients was the addition of K to the forest floor pools, which was also reflected in resin-based measurements of soil nutrients. Burning caused increases in soil NO3-N, mineral N, Ca2+, and SO42- as measured by PRS probes, which persisted for 2 years after the burn. The more intense burning in the T+B treatment also caused elevated orthophosphate levels 2 years after the burn. Burning effects on K+ and Mg2+ were not significant. Overall, the most ecologically significant effect of treatment was the export of N from the combination of harvesting and burning in the T+B treatment, which totaled 932 kg ha-1 and 13% of the total ecosystem N capital.

Technical Abstract: The effects of thinning followed by residue mastication (THIN), prescribed fire (BURN), and thinning plus residue mastication plus burning (T+B) on nutrient budgets and resin-based (plant root simulator [PRS] probe) measurements of soil nutrient availability in a mixed-conifer forest were measured. Because of site differences, removals of carbon (C) and nutrients by harvesting were greater in the T+B than in the THIN (Mg) treatment. Harvesting caused greater exports of C, phosphorus, potassium (K), calcium (Ca), and magnesium (Mg) than burning, harvesting and burning caused approximately equal exports of nitrogen (N), and burning caused greater exports of sulfur than harvesting. Burning caused greater volatilization losses of C and N from the T+B than from the BURN treatment because the addition of chips from mastication in the T+B treatment caused greater combustion of the native forest floor. The most significant effect of the chips on soil nutrients was the addition of K to the forest floor pools, which was also reflected in resin-based measurements of soil nutrients. Burning caused increases in soil NO3-N, mineral N, Ca2+, and SO42- as measured by PRS probes, which persisted for 2 years after the burn. The more intense burning in the T+B treatment also caused elevated orthophosphate levels 2 years after the burn. Burning effects on K+ and Mg2+ were not significant. Overall, the most ecologically significant effect of treatment was the export of N from the combination of harvesting and burning in the T+B treatment, which totaled 932 kg ha-1 and 13% of the total ecosystem N capital.

Last Modified: 7/30/2014
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