Effects Of Afforestation Of Agricultural Land On Carbon Stocks And Allocation Pattern In Semi-arid Sandy Region

Global climate change and its impacts on the earth are one of the most severe problems which human face. The critical issue is the changing pattern of carbon cycle and its reasons. The soil organic carbon pool is the largest carbon storage pool in the terrestrial ecosystem, which plays an important role in accommodating climate and affecting climate. Human activities on the carbon pool of terrestrial ecosystem and changing pattern of the fossil carbon pool are ultimately the causes of the climate change. The land-use change is the main human activity, which affects the global environment and has an influence on the global climate change. To scientifically learn the effects of land-use change on soil organic carbon is the key for us to understand and solve the climate change problem.Afforestation of agricultural land is a long-term and complex ecological project that is in order to recover the vegetation, reduce water loss and soil erosion, protect and control sand, improve ecological environment being on the slide, adjust rural industry structure and increase the income of farmers. Along with the full implementation of afforestation of agricultural land, many relevant theory and technology, especially the ecological effect research on this shift has been the important content in the academic fields.In this paper we investigated the effects of arable land afforestation with poplar on ecosystem C stocks and distribution patterns. The results showed that the biomass C stocks increased gradually with the site age and most of the C was sequestered in the tree stem. Mineral soil C concentration in 0–10 cm, 10–20 cm, 20–40 cm, 40–60 cm depths under 5 year-old poplar plantation (Poplar 1) decreased by 7.65%, 36.66%, 51.94%, 21.4% (P>0.05, P<0.01, P<0.05, P>0.05) compared with the farmland (CK1). However, mineral soil C concentration in 10 year-old poplar plantation (Poplar 2) increased by 69.63%, 62.46%, 17.07% and 66.94% (P<0.05, P<0.05, P<0.05, P<0.05), respectively, compared with the farmland (CK1). The mineral soil C concentration in 0–10 cm, 20–40 cm, 40–60 cm increased by 31.96%, 81.50%, 58.05% (P<0.05, P<0.01, P<0.05), but in 10–20 cm decreased by 13.38% (P>0.05) under 15 year-old poplar plantation (Poplar 3) compared with the farmland (CK2). Mineral soil C stocks up to 60 cm decreased by 31% (P<0.05) for 5 year-old poplar plantation. However, mineral soil C stocks increased by 47% and 41% (P<0.05) in 10 and 15 year-old poplar plantation, respectively. Total C stocks decreased by 10% under 5 year-old poplar plantation (Poplar 1) compared with the farmland (CK1), but total C stocks increased 2 times and 5 times for 10 and 15 year-old poplar plantation compared with the control farmland. Our results implied that the ecosystem C stocks increased significantly following arable land afforestation with poplar, and most of the C was accumulated in the vegetation biomass pool. In the earlier stage of afforestation mineral soil C stocks decreased, then regained with site age increase.