From 20cm to 1.5m: Is Digging Deeper Necessary?
Abstract
Quantification of belowground carbon (C) currently stored in forest ecosystems is far from complete, especially for deeper soil horizons. Given logistical difficulties of sampling deep soils over large areas, much attention has been given to estimate deep SOC stocks indirectly. It is unknown whether C content in the top 20 cm of the mineral soil is an effective index for deep soil C storage across broad ranges of climate, forest type, and soil characteristics. The US Forest Service has a large record of aboveground and belowground (up to 20 cm depth) C data that could potentially be used to quantify deep SOC stocks if a suitable indirect estimation method can be developed. We followed and extended USDA FS Forest Inventory Analysis protocols to sample forest sites in the Midwest U.S. to determine C content up to 1.5m depth over a range of forest and soil types. Preliminary results show that, at hardwood sites, C percent in the top 20 cm of the mineral soil predicted only 28% of deep soil C in sandy soils and 20% in loamy soils. On a mass basis (mg C/cm3), such relationship was even weaker, suggesting that a number of biophysical variables affect SOC storage along the soil profile. Ongoing analyses will identify whether including additional factors such as forest type and soil chemical-physical characteristics will strengthen this relationship. The use of fractionation techniques and stable and radioactive isotopes will help illustrate SOC stabilization mechanisms.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.B11A0468F
- Keywords:
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- 0414 BIOGEOSCIENCES / Biogeochemical cycles;
- processes;
- and modeling;
- 0428 BIOGEOSCIENCES / Carbon cycling;
- 1615 GLOBAL CHANGE / Biogeochemical cycles;
- processes;
- and modeling