Respiration, isotope composition, and carbon source partitioning from incubations of soil amended with litter and isotope-labeled lignin

We incubated 10 forest soils (collected from sites across North
America, including the Luquillo LTER/CZO) in the laboratory for over
two years to quantify the decomposition of carbon derived from added
litter and lignin, as well as from extant soil organic matter. Each
soil was subjected to two substrate addition treatments: a) litter
derived from a C4 grass precipitated with 13C-enriched lignin, or the
same C4 grass litter was precipitated with natural-abundance lignin.
The concentrations and delta13C composition of carbon dioxide produced
from each soil were measured periodically over time and partitioned
into sources (soil organic matter, litter, and added lignin) using
isotope mixing models. The methods and results are described in detail
by a manuscript in Ecology (Hall et al., 2020).