造林工程已经对生态恢复起到重要作用,并将对全球碳素循环起到积极作用。以内蒙古农牧交错带小叶杨(Populus simonii)人工林为研究对象,并以天然草地为对照,分析了退牧还林对生态系统碳储量和碳循环的影响。结果表明,造林活动使植被碳库迅速增加,凋落物碳库及生态系统碳库基本上随林龄的增加而缓慢增加,土壤碳库则随林龄增加出现先降低再增加的趋势;小叶杨林木平均碳汇速率表现为:幼龄林>中龄林>近熟林>成熟林;以成熟林(30 a)为参照,小叶杨林木固碳潜力为4500 g·m-2,生态系统固碳潜力为5141.79 g·m-2。研究结果表明,内蒙古农牧交错区退牧还林后种植的小叶杨人工林在长时间尺度上是一个可观的碳汇。
Afforestation projects play an important role in ecosystem restoration and will contribute to global carbon cycles. The study target was the Populus simonii man-made forests in the agro-pasture zigzag zone of Inner Mongolia, with natural grasslands as a control. We summarized and analyzed how the"conversion from grazing land into forest"affected the ecosystem carbon stocks and carbon cycles.The afforestation activities led to rapid increase of vegetation carbon stocks, since with the prolonging of forest age, the litter carbon stocks and ecosystem carbon stocks slowly increased, but soil carbon stocks first dropped and then rose. The average carbon sink rates change with forest age as follows: young forest > medium age forest > near-mature forest > mature forest.With mature forest (30 a) as reference, the P. simonii forest carbon sequestration potential (CSP) is 4 500 g·m-2, while the P. simonii ecosystem CSP is 5 141.79 g·m-2. These results indicate that after conversion from grazing land into forest in the study area, the P. simonii ecosystem is a considerable carbon sink in the long term.