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Description:
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Seasonal nitrogen and biomass dynamics were documented for a native sand shinnery oak community and areas treated with tebuthiuron three years and six years prior to sampling . Herbicidal treatment resulted in oak death and a change in plant community structure . Biomass , percent nitrogen , and organic carbon were measured for above -ground and below -ground compartments at three dates during the year which represented growth initiation , peak production , and winter dormancy .
Total biomass was not significantly changed by treatment . Above -ground biomass decreased significantly over time from the control to the 3 -year and 6 -year treatments . The absence of above -ground oak material and the significant decrease in litter on the two treated sites accounted for the change . Above -ground herbaceous material , however , increased 6 fold from the control to the two treated sites . Below -ground biomass was similar for all treatments and was only slightly lower on the 6 -year treatment . Oak root biomass was reduced 1 % , three years following oak death and 23 % after six years . Significant (2 - to 3 -fold ) increases in herbaceous roots on the treated sites offset the oak root decrease and stabilized the weights for below -ground biomass .
Available soil nitrogen increased from the control to the 3 -year treatment and to the 6 -year treatment . Soil nitrogen was significantly higher in the surface 15 cm and in the top of the B2t argillic subhorizon than in the two intermediate depths . Differences were primarily related to concentration of soil organic matter which increased as a result of oak root and litter decomposition . |