[permaculture] (fwd) Nature Geoscience 2, 37 - 41 (2009) Effects of agricultural land use on the composition of fluvial dissolved organic matter

Lawrence F. London, Jr. lflj at intrex.net
Thu Dec 25 18:44:04 EST 2008


http://lists.ifas.ufl.edu/cgi-bin/wa.exe?A2=ind0812&L=sanet-mg&T=0&O=D&P=77733
SANET-MG Archives -- December 2008 (#113)
Subject:	 Effects of agricultural land use on the composition of fluvial dissolved organic matter
From:	jcummins <[log in to unmask]>
Reply-To:	Sustainable Agriculture Network Discussion Group <[log in to unmask]>, jcummins <[log in to unmask]>
Date:	Thu, 25 Dec 2008 14:41:30 -0500

Nature Geoscience 2, 37 - 41 (2009)
   doi:10.1038/ngeo391
Effects of agricultural land use on the composition of fluvial
dissolved organic matter
Henry F. Wilson & Marguerite A. Xenopoulos
Nearly 40% of the Earth's ice-free surface area is cropland or
pasture1. Agricultural land use can increase the delivery of nutrients
such as nitrogen and phosphorus to fluvial ecosystems2, but the impact
of farming on riverine dissolved organic carbon is still largely
unknown, despite increasing recognition that rivers act as important
modifiers in the global carbon cycle. Here, we examine the character
of riverine dissolved organic matter in  watersheds along a gradient
of agricultural land use. We show that changes in the character of
dissolved organic matter are related to agricultural land use,
nitrogen loading and wetland loss. Specifically, we find that the
structural complexity of dissolved organic matter decreases as the
ratio of continuous croplands to wetlands increases. At the same time,
the amount of microbially derived dissolved organic matter increases
with greater agricultural land use. Furthermore, we find that periods
of soil dryness are associated with a decrease in the structural
complexity of dissolved organic matter. We suggest that these effects
of land use and climate on the character of riverine dissolved organic
matter have important implications for global carbon cycling, owing to
their potential to control rates of microbial carbon processing (for
example, uptake, retention and outgassing) in agricultural systems.



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