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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>Dan Binkley</dc:contributor>
  <dc:contributor>Hlynur Oskarsson</dc:contributor>
  <dc:contributor>Robert Stottlemyer</dc:contributor>
  <dc:creator>Charles Rhoades</dc:creator>
  <dc:date>2008</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;Nitrogen enters terrestrial ecosystems through multiple pathways during primary succession. We measured accumulation of total soil nitrogen and changes in inorganic nitrogen (N) pools across a 300-y sequence of river terraces in northwest Alaska and assessed the contribution of the nitrogen-fixing shrub&amp;nbsp;&lt;/span&gt;&lt;i&gt;Shepherdia canadensis&lt;/i&gt;&lt;span&gt;. Our work compared 5 stages of floodplain succession, progressing from a sparsely vegetated silt cap to dense shrubby vegetation, balsam poplar-dominated (&lt;/span&gt;&lt;i&gt;Populus balsamifera&lt;/i&gt;&lt;span&gt;) and white spruce-dominated (&lt;/span&gt;&lt;i&gt;Picea glauca&lt;/i&gt;&lt;span&gt;) mixed forests, and old-growth white spruce forest. Total soil N (0–30 cm depth) increased throughout the age sequence, initially by 2.4 g N·m&lt;/span&gt;&lt;sup&gt;−2&lt;/sup&gt;&lt;span&gt;·y&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;during the first 120 y of terrace development, then by 1.6 g N·m&lt;/span&gt;&lt;sup&gt;−2&lt;/sup&gt;&lt;span&gt;·y&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;during the subsequent 2 centuries. Labile soil N, measured by anaerobic incubation, increased most rapidly during the first 85 y of terrace formation, then remained relatively constant during further terrace development. On recently formed terraces,&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;i&gt;Shepherdia&lt;/i&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;shrubs enriched soil N pools several-fold compared to soil beneath&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;i&gt;Salix&lt;/i&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;spp. shrubs or intercanopy sites. Total and labile soil N accretion was proportional to&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;i&gt;Shepherdia&lt;/i&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;cover during the first century of terrace development, and mineral soil δ&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;N content indicated that newly formed river terraces receive substantial N through N-fixation. About half the 600 g total N·m&lt;/span&gt;&lt;sup&gt;−2&lt;/sup&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;accumulated across the river terrace chronosequence occurred during the 120 y when&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;i&gt;S. canadensis&lt;/i&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;was dominant. Sediment deposited by periodic flooding continued to add N to terrace soils after the decline in&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;i&gt;Shepherdia&lt;/i&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;abundance and may have contributed 25% of the total N found in the floodplain terrace soils.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.2980/15-2-3027</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>BioOne</dc:publisher>
  <dc:title>Soil nitrogen accretion along a floodplain terrace chronosequence in northwest Alaska: Influence of the nitrogen-fixing shrub &lt;i&gt;Shepherdia canadensis&lt;/i&gt;</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>