关帝山林区退化灌木林转变为华北落叶松林对生态系统碳储量的影响

针对我国大量灌木林出现退化而宜林地又日益减少的现状，在适宜种植乔木的地区，将退化灌木林转变为乔木林被认为是一种可行的植被恢复方式。以关帝山林区退化灌木次生林转变而成的不同林龄（10、18、23、27年和35年）华北落叶松（Larix principis-rupprechtii Mayr.）林为研究对象，并以相邻的退化灌木次生林为对照，探究这种转变对生态系统碳储量及其组分的影响，将为我国开展造林/再造林、林业碳汇项目等工作提供科学依据和数据支撑。与灌木林相比，造林初期的生态系统碳储量及其组分均出现不同程度的下降。10年生华北落叶松林的生态系统碳储量相对于灌木林显著下降了32.9%（P < 0.05），但并非所有组分的下降都显著（P < 0.05）。植被碳储量下降34.7%，其植被地上和地下碳储量分别下降5.4%和70.9%，但只有植被地下碳储量是显著减少的（P < 0.05）；凋落物碳储量下降42.8%，但并不显著（P=0.71）；土壤有机碳储量（0-50 cm）显著下降32.6%（P < 0.05），其不同土层（0-10、10-30 cm和30-50 cm）的碳储量也都出现显著减少（P < 0.05）。林龄从10年到35年，华北落叶松林生态系统碳储量增加了1.6倍，植被及其组成（地上和地下）、凋落物、土壤有机碳及其不同土层（0-10、10-30 cm和30-50 cm）等的碳储量也随之不断增加，从而使得生态系统碳储量及其组分逐渐达到并全面超过灌木林。但是，不同组分要达到灌木林的碳储量水平，需要的时间存在较大差异：土壤有机碳库 > 植被地下碳库 > 植被地上碳库，其中深层土壤有机碳 > 表层土壤有机碳（0-10 cm）。

Changes in ecosystem carbon storage following conversion of degraded shrubland to larch (Larix principis-rupprechtii Mayr.) in the Guandi Mountain Forest Region, northern China

For large areas of degraded shrubland and substantially reduced lands for forest, vegetation restoration can be applied to convert degraded shrubland to tree forest (CST) in areas favorable for planting trees. Understanding the effects of CST on ecosystem carbon storage and its components can facilitate afforestation/reforestation efforts and forest carbon sequestration programs in China. In this study, we assessed larch (Larix principis-rupprechtii Mayr., LPR) plantations of different ages (10, 18, 23, 27 and 35-year old), which were previously degraded shrubland, and adjacent degraded shrubland in the Guandi Mountain Forest Region, northern China, to explore the effects of CST on ecosystem carbon storage and its components. Compared with that of the adjacent shrubland, ecosystem carbon storage and its components were lower at the early stages of afforestation. The ecosystem carbon storage of the 10-year-old LPR plantations was significantly lower (32.9%, P < 0.05) than that of the shrubland; however, not all differences between carbon pools were significant (P < 0.05). Total vegetation carbon storage was 34.7% lower in the 10-year-old LPR plantations than in the adjacent shrubland, and above-and belowground carbon pools were 5.4% and 70.9% lower, respectively; however, only the difference in the belowground carbon pool was significant (P < 0.05). The litter carbon storage was 42.8% lower (P=0.71), soil organic carbon storage (0-50 cm) was significantly lower (32.6%), and carbon storage in the different soil layers (0-10, 10-30, and 30-50 cm) was also significantly lower (P < 0.05) in the 10-year-old plantations compared with the adjacent shrubland. The ecosystem carbon storage of LPR was 1.6 times higher in the 35-year-old plantations than in the 10-year-old plantations, and the carbon storages of the vegetation (aboveground, belowground, and whole), litter, and soil organic carbon (soil layers and whole) were also higher in the older plantations. Therefore, the ecosystem carbon storage (and its components) of LPR plantations gradually reached and surpassed that of the degraded shrubland. However, the process to reach the carbon storage levels of shrubland occurred over different time periods:soil organic carbon pool > vegetation belowground pool > vegetation aboveground pool, where deep soil organic carbon > surface soil (0-10 cm).