Subject: Effects of nitrogen additions on soil carbon

From: "Andy Clark, SAN Coordinator" <[email-masked]>
Date: Thu, 31 Oct 2002 13:24:02 -0500

SANET:

An article of interest appeared in Nature.  More information about the
on-line Nature magazine below this abstract.

See the full article by going to 
http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v419/n6910/a
bs/nature01136_fs.html

Andy

Nature 419, 915 - 917 (2002); doi:10.1038/nature01136 

Variable effects of nitrogen additions on the stability and turnover
of soil carbon

JASON C. NEFF*?, ALAN R. TOWNSEND??§, GERD GLEIXNER, SCOTT J. LEHMAN§,
JOCELYN TURNBULL§ &
WILLIAM D. BOWMAN?

* Earth Surface Processes Team, Geologic Division, US Geological Survey, MS
980, Denver Federal Center, Denver, Colorado 80225, USA
? Environmental, Population and Organismic Biology, University of Colorado
at Boulder, Boulder, Colorado 80309, USA
§ Institute for Arctic and Alpine Research, University of Colorado at
Boulder, Boulder, Colorado 80309, USA
  Max Planck Institute for Biogeochemistry, Jena, Germany
? These authors contributed equally to this work

Correspondence and requests for materials should be addressed to J. N.
(e-mail: [email-masked]).

Soils contain the largest near-surface reservoir of terrestrial carbon and
so knowledge of the factors controlling soil
carbon storage and turnover is essential for understanding the changing
global carbon cycle. The influence of climate
on decomposition of soil carbon has been well documented, but there remains
considerable uncertainty in the
potential response of soil carbon dynamics to the rapid global increase in
reactive nitrogen (coming largely from
agricultural fertilizers and fossil fuel combustion). Here, using 14C, 13C
and compound-specific analyses of soil
carbon from long-term nitrogen fertilization plots, we show that nitrogen
additions significantly accelerate
decomposition of light soil carbon fractions (with decadal turnover times)
while further stabilizing soil carbon
compounds in heavier, mineral-associated fractions (with multidecadal to
century lifetimes). Despite these changes
in the dynamics of different soil pools, we observed no significant changes
in bulk soil carbon, highlighting a
limitation inherent to the still widely used single-pool approach to
investigating soil carbon responses to changing
environmental conditions. It remains to be seen if the effects observed
here-caused by relatively high, short-term
fertilizer additions-are similar to those arising from lower, long-term
additions of nitrogen to natural ecosystems
from atmospheric deposition, but our results suggest nonetheless that
current models of terrestrial carbon cycling do
not contain the mechanisms needed to capture the complex relationship
between nitrogen availability and soil
carbon storage.

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Nature Contents: 31 October 2002 Volume 419 No. 6910
(c) 2002 Nature Publishing group 

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