Haddix Michelle L, Paul Eldor A, Cotrufo M Francesca
Natural Resource Ecology Laboratory, Colorado State University, 200 West Lake Street, Fort Collins, CO, 80523-1499, USA.
Department of Soil and Crop Sciences, Colorado State University, 200 West Lake Street, Fort Collins, CO, 80523-1499, USA.
Glob Chang Biol. 2016 Jun;22(6):2301-12. doi: 10.1111/gcb.13237. Epub 2016 Mar 4.
The formation and stabilization of soil organic matter (SOM) are major concerns in the context of global change for carbon sequestration and soil health. It is presently believed that lignin is not selectively preserved in soil and that chemically labile compounds bonding to minerals comprise a large fraction of the SOM. Labile plant inputs have been suggested to be the main precursor of the mineral-bonded SOM. Litter decomposition and SOM formation are expected to have temperature sensitivity varying with the lability of plant inputs. We tested this framework using dual (13) C and (15) N differentially labeled plant material to distinguish the metabolic and structural components within a single plant material. Big Bluestem (Andropogon gerardii) seedlings were grown in an enriched (13) C and (15) N environment and then prior to harvest, removed from the enriched environment and allowed to incorporate natural abundance (13) C-CO2 and (15) N fertilizer into the metabolic plant components. This enabled us to achieve a greater than one atom % difference in (13) C between the metabolic and structural components within the plant litter. This differentially labeled litter was incubated in soil at 15 and 35 °C, for 386 days with CO2 measured throughout the incubation. After 14, 28, 147, and 386 days of incubation, the soil was subsequently fractionated. There was no difference in temperature sensitivity of the metabolic and structural components with regard to how much was respired or in the amount of litter biomass stabilized. Only the metabolic litter component was found in the sand, silt, or clay fraction while the structural component was exclusively found in the light fraction. These results support the stabilization framework that labile plant components are the main precursor of mineral-associated organic matter.
在全球变化背景下，土壤有机质（SOM）的形成与稳定是碳固存和土壤健康方面的主要关注点。目前认为，木质素在土壤中并非被选择性地保存，且与矿物质结合的化学不稳定化合物占土壤有机质的很大一部分。有人提出，不稳定的植物输入物是与矿物质结合的土壤有机质的主要前体。预计凋落物分解和土壤有机质形成的温度敏感性会随植物输入物的不稳定程度而变化。我们使用双（13）C和（15）N差异标记的植物材料来测试这一框架，以区分单一植物材料中的代谢和结构成分。大须芒草（Andropogon gerardii）幼苗在富含（13）C和（15）N的环境中生长，然后在收获前从富含环境中移出，使其将自然丰度的（13）C-CO2和（15）N肥料纳入植物的代谢成分中。这使我们能够在植物凋落物的代谢和结构成分之间实现大于1个原子百分比的（13）C差异。将这种差异标记的凋落物在15和35°C的土壤中培养386天，在整个培养过程中测量CO2。培养14、28、147和386天后，随后对土壤进行分级。就呼吸量或凋落物生物量稳定量而言，代谢和结构成分的温度敏感性没有差异。仅在砂、粉砂或粘粒部分中发现了代谢凋落物成分，而结构成分仅存在于轻组部分中。这些结果支持了不稳定植物成分是与矿物质相关的有机质的主要前体这一稳定框架。
