Data from: Litter quality controls tradeoffs in soil carbon decomposition and replenishment in a subtropical forest

Species-rich forests can produce litter of varying carbon (C) and nitrogen
(N) composition (i.e., quality), which can affect decomposition and play a
central role in long-term soil organic carbon (SOC) accumulation. However,
how differences in litter quality affect SOC decomposition and formation
remains unclear over the full litter decomposition trajectory. 
We followed the in-situ complete decomposition of added 13C-labelled high-
(low C:N) and low-quality (high C:N) leaf-litter and its effect on
particulate (POM) and mineral-associated (MAOM) organic matter fractions
over two years in a natural subtropical forest. We found that during early
stages of decomposition, low-quality litter inputs decreased SOC via a
positive priming effect (i.e., new C inputs favored decomposition of
native SOC), but these SOC losses were offset by SOC gains observed via a
negative priming effect during decomposition of high-quality litter. In
contrast, this pattern reversed during late stages of decomposition—SOC
losses via a positive priming effect induced by high-quality litter were
offset by SOC gains via a negative priming effect induced by low-quality
litter. Over the full decomposition of litter, both high- and low-quality
litter stimulated microbial breakdown of SOC tied to POM, but also
replenished more persistent SOC that associated with soil minerals (MAOM).
Altogether, we observed that low-quality litter formed twice as much new
SOC as high-quality litter (24% vs. 12% of added litter-C). We extend the
notion of the priming effect from primarily a negative role
promoting losses of native SOC, to a functional role that can replenish
persistent SOC. Synthesis. Our measurements raise the possibility that, in
species-rich forests, high- and low-quality litter decomposition play
opposite but dynamically complementary roles in renewing POM—both by
inducing its decomposition and formation—while exclusively favoring MAOM
formation, which can help explain how differences in litter quality favor
SOC accumulation and persistence. Global change factors that shift plant
community composition may ultimately affect the fate of soil C, as changes
in litter quality may force soil transitions from sinks to sources or
sources to sinks of atmospheric CO2.