Temporal progress in improving carbon and nitrogen storage by grazing exclosure practice in a degraded land area of China's Horqin Sandy Grassland

Overgrazing is a primary agent to cause and aggravate desertification in the Horqin Sandy Grassland of northern China that has reduced the capacity of carbon (C) and nitrogen (N) storage in the region. Grazing exclosure practice is recommended to control the desertification by vegetation restoration. How the restoration improves the C and N storage needs to be answered to the policy makers for their future land use planning and decisions. This storage in a plant-soil system down to 100 cm inside grazing exclosure after practice terms of 7, 12, and 25 years was measured as compared to active sand dunes referred as exclosure practice term of 0. Organic C storage in the system increased by 341, 822, and 1786 g m(-2), respectively, after 7, 12, and 25 years of grazing exclosure, whereas the corresponding N storage increased by 30, 65, and 139 g m(-2). Soil is the major reservoir in the system to store C and N. Temporally along the exclosure terms of 0, 7, 12, and 25 years, the soil C storage comprised 97, 88, 77, and 84% of total plant-soil system C storage, respectively, whereas the corresponding soil total N storage comprised 99, 97, 94, and 94% of total plant-soil system N storage. Our results provide land use policy makers with rationale how to manage the grazing practice to restore the vegetation for C and N sequestration. (C) 2012 Elsevier B.V. All rights reserved.