Comments on: Front Range Student Ecology Symposium

By: Anthony’s Science Blog » Blog Archive » Ecological Society of America Meeting 2009

Wed, 05 Aug 2009 22:00:55 +0000

[…] I will be presenting a poster, which is the same as the poster I presented earlier this year at the Front Range Student Ecology Symposium. I actually kind of wish that I had an updated version of my poster since I have made a lot of […]

By: Aaron

Aaron — Fri, 27 Feb 2009 23:18:39 +0000

Good information, Anthony. I think that the soil has great potential to give a really good index of the plant response to average environmental conditions, especially in the light fraction. Thanks!

By: Anthony

Anthony — Thu, 26 Feb 2009 21:26:31 +0000

When I measured these samples, I measured two density fractions that varied in average residence time: one lighter fraction with a turnover time of about a decade, and one heavier fraction with a turnover time of decades to centuries. I just took a look at these two fractions and the patterns look basically the same as the total pattern that I posted. In particular, the fact that the light fraction – which is thought to be chemically dominated by plant materials – shows the same correlation with landscape moisture regimes suggests that plant inputs are exerting a fairly strong influence on the soil δ¹³C signature. However, this does not rule out the decomposition effect that you mention. As for the slow enriching effect over time, the data from the two density fractions do suggest that a small amount of this is occurring. The difference in mean δ¹³C between the two fractions is about 0.8‰. It would be great to see how these soil values compare to fresh plant material from these areas and how fresh material from different plant species compare to each other.

By: Aaron

Aaron — Thu, 26 Feb 2009 20:43:19 +0000

Last night I was reading more about this trying to see if anyone has looked at the links between plant and soil C isotopes. In a book called “Mass Spectrometry of Soils” the authors noted that δ¹³C doesn’t change MUCH during the first few years of decomposition, but that there is fractionation as the microbes assimilate the carbon. They suggested that microbes preferentially respire lighter carbon, which causes soil organic carbon to be slightly more enriched (around 1-3‰).

Is it enough to account for the differences that you saw on the landscape, especially with the (generally) slower decomposition in high-elevations? I guess that awaits to be seen.

Another thing I thought about is the turnover time of carbon in the soil. Could there be an additive effect of enriching the soil in the dry sites (from slight enrichment every year) over many years? Do you know any general turnover times for soil carbon?