Authors: M D MacKenzie T H DeLuca
Publish Date: 2006/08/24
Volume: 287, Issue: 1-2, Pages: 257-266
Abstract
Lowelevation ponderosa pine Pinus ponderosa Doug ex laws forests of western Montana are naturally fire maintained ecosystems However 80–140 years of fireexclusion has led to the formation of dense mixed stands of ponderosa pine and Douglasfir Pseudotsuga menzesii Mirbel Franco an understory codominated by graminoids and ericaceous shrubs and low N availability Ericaceous shrubs in particular have been found to influence soil processes in boreal ecosystems and potentially exacerbate N limiting conditions In this set of studies we investigated the influence of graminoid and ericoid litter chemistry on soil processes and evaluated the influence of charcoal as a sorbant of C compounds and depositional product of fire A series of experiments were performed with two common understory plants of this ecosystem elk sedge Carex geyeri Boott and kinnikinnick Arctostaphylos uvaursi L Spreng an ericaceous shrub Charcoal 100 g m−2 and glycine 5 g m−2 were applied in factorial combination to intact litter microcosms of these species Nonionic resin capsules were used to monitor mobile C compounds and ionic resins were used to monitor net N mineralization and nitrification insitu Greenhouse studies revealed that the addition of glycine and charcoal leads to a significant increase in net nitrification in shrub litter microcosms but not sedge litter microcosms as measured by NO 3 − sorption to ionic resin capsules Charcoal and glycine also resulted in a significant increase of anthrone reactive C soluble hexose sugars an index of bioavailable C in shrub litter microcosms Analysis of leaf litter leachate from these two plant communities indicated similar nutrient concentrations but almost 20 times more phenolic compounds in shrub leaf leachates Charcoal was shown to be extremely effective at sorbing phenols removing over 80 of phenolic compounds from solution These results suggest that charcoal deposition after fire may modify a nitrification interference mechanism by sorbing plant secondary metabolites After time charcoal loses its ability to sorb C compounds and ericaceous litter decomposition and subsequent release of phenolics may interfere with nitrification once againThe authors wish to thank Pete Grum and Jennifer MacKenzie for their assistance with this project and three anonymous reviewers for useful comments and suggestions This work was supported in part by the USDA McIntireStennis program at the University of Montana College of Forestry and Conservation and the Forest Experiment Station
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