Event Title

Does Mastication Residue Alter Soil Nitrogen Dynamics in Woodlands Of Southwest Colorado?

Event Website

http://www.nafew2009.org/

Start Date

24-6-2009 8:20 AM

End Date

24-6-2009 8:40 AM

Description

Large wildfires were historically uncommon in the woodland ecosystems of southwest Colorado, yet between 1996 and 2003 six large wildfires occurred. The potential for large wildfires in these woodlands has been exacerbated by the fuel buildups related to extended drought and infestation of pinyon ips (Ips confuses) that have killed millions of trees in this region, along with Euro-American settlement impacts that has altered the fire regime. Wildfire mitigation treatments are few, but one promising technique in woodland ecosystems is mastication of both live and dead standing fuels to alter wildfire behavior. Mastication of woody material has raised concerns that a shift in the carbon: nitrogen (C:N) ratio due to the residual plant material left on the soil surface may slow decomposition rates and limit plant available N needed for long-term site productivity. We compared net N mineralization in the upper 15 cm of mineral soil from thinned and burned, masticated, and untreated plots at three sites dispersed over a large area of southwest Colorado. Net N mineralization was measured using plant root simulator probes (WesternAg, Inc.) continuously for over two years following treatment. Preliminary data on microbial biomass and community structure, measured using phospholipid fatty acids, will also be presented. This technique allows us to determine if there has been a structural shift of microbial communities with emphasis on changes to the fungal:bacterial (F:B) ratios in organic and soil horizons. The plant residue additions to the soil surface should increase C:N ratios and total surface biomass following mastication. Does this alteration also influence the mineral soil C:N ratios by reallocating N from the upper mineral soil and immobilizing it in the mastication residue by fungal decomposers, thus decreasing N availability for a plant growth?

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Jun 24th, 8:20 AM Jun 24th, 8:40 AM

Does Mastication Residue Alter Soil Nitrogen Dynamics in Woodlands Of Southwest Colorado?

Large wildfires were historically uncommon in the woodland ecosystems of southwest Colorado, yet between 1996 and 2003 six large wildfires occurred. The potential for large wildfires in these woodlands has been exacerbated by the fuel buildups related to extended drought and infestation of pinyon ips (Ips confuses) that have killed millions of trees in this region, along with Euro-American settlement impacts that has altered the fire regime. Wildfire mitigation treatments are few, but one promising technique in woodland ecosystems is mastication of both live and dead standing fuels to alter wildfire behavior. Mastication of woody material has raised concerns that a shift in the carbon: nitrogen (C:N) ratio due to the residual plant material left on the soil surface may slow decomposition rates and limit plant available N needed for long-term site productivity. We compared net N mineralization in the upper 15 cm of mineral soil from thinned and burned, masticated, and untreated plots at three sites dispersed over a large area of southwest Colorado. Net N mineralization was measured using plant root simulator probes (WesternAg, Inc.) continuously for over two years following treatment. Preliminary data on microbial biomass and community structure, measured using phospholipid fatty acids, will also be presented. This technique allows us to determine if there has been a structural shift of microbial communities with emphasis on changes to the fungal:bacterial (F:B) ratios in organic and soil horizons. The plant residue additions to the soil surface should increase C:N ratios and total surface biomass following mastication. Does this alteration also influence the mineral soil C:N ratios by reallocating N from the upper mineral soil and immobilizing it in the mastication residue by fungal decomposers, thus decreasing N availability for a plant growth?

http://digitalcommons.usu.edu/nafecology/sessions/mastication/3