Plant Debris and Its Contribution to Ecosystem Carbon Storage in Successional Larix gmelinii Forests in Northeastern China

Plant debris, including woody debris and litter, is an essential but frequently overlooked component of carbon (C) storage in forest ecosystems. Here, we examined the C storage of plant debris and its contribution to total ecosystem C storage in an age sequence of six larch (Larix gmelinii) forest stands (15, 36, 45, 54, 65, and 138 years old) in northeastern China. The plant debris C storage increased from 6.0 ± 0.5 Mg·C·ha−1 in the 15-year-old stand to a maximum of 9.3 ± 1.8 Mg·C·ha−1 in the 138-year-old stand. The C storage of woody debris increased during stand development in a sigmoidal pattern, increasing from 0.7 ± 0.2 Mg·C·ha−1 in the 15-year-old stand to 4.7 ± 1.3 Mg·C·ha−1 in the 138-year-old stand. However, the C storage of litter (4.6−5.4 Mg·C·ha−1) did not vary with stand age in this larch chronosequence. In addition, the ratio of woody debris to live tree biomass C storage was relatively stable across stands (approximately 3.3%). These results highlight the importance of considering successional development and stand characteristics in assessing changes of plant debris and total ecosystem C storage in the larch forest ecosystem.