Abstract
The Grain to Green Project (GGP) is an unprecedented land restoration action in China. The project converted large areas (ca 10 million ha) of steep-sloped/degraded farmland and barren land into forest and grassland resulting in ecological benefits such as a reduction in severe soil erosion. It may also affect soil microorganisms involved in ammonia oxidization, which is a key step in the global nitrogen cycle. The methods for restoration that are typically adopted in semi-arid regions include abandoning farmland and growing drought tolerant grass (Lolium perenne L.) or shrubs (Caragana korshinskii Kom.). In the present study, the effects of these methods on the abundance and diversity of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) were evaluated via quantitative real-time PCR, terminal restriction fragment length polymorphism and clone library analysis of amoA genes. Comparisons were made between soil samples from three restored lands and the adjacent farmland in Inner Mongolia. Both the abundance and community composition of AOB were significantly different between the restored lands and the adjacent control. Significantly lower nitrification activity was observed for the restored land. Clone library analysis revealed that all AOB amoA gene sequences were affiliated with Nitrosospira. Abundance of the populations that were associated with Nitrosospira sp. Nv6 which had possibly adapted to high concentrations of inorganic nitrogen, decreased on the restored land. Only a slight difference in the AOB communities was observed between the restored land with and without the shrub (Caragana korshinskii Kom.). A minor effect of land restoration on AOA was observed. In summary, land restoration negatively affected the abundance of AOB and soil nitrification activities, suggesting the potential role of GGP in the leaching of nitrates, and in the emission of N2O in related terrestrial ecosystems.
Highlights
China implemented the Grain to Green Program (GGP) in 1897 counties of 25 provinces, including Inner Mongolia, to increase vegetation coverage [1]
The lowest carbon-to-nitrogen ratio and water content were measured in land growing Caragana korshinskii Kom. (Table 1)
We explored the influence of three typical land restoration methods applied in semi-arid regions on the abundance and diversity of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in soils
Summary
China implemented the Grain to Green Program (GGP) in 1897 counties of 25 provinces, including Inner Mongolia, to increase vegetation coverage [1]. By the end of 2012, approximately 9.7 million hectares of cropland had been converted to forest or grassland [2]. This greatly improved soil conditions across China through decreasing soil erosion [3], and increasing soil organic carbon content [4]. There are three typical restoration methods in Inner Mongolia: abandoning farmland, growing grass (Lolium perenne L.), and growing shrubs (Caragana korshinskii Kom.). Both Lolium perenne L. and Caragana korshinskii Kom. are drought-tolerant plants suitable for land restoration in arid or semi-arid regions [5]. The effects of land restoration on the soil nitrogen cycle, as well as on participating microorganisms, remain poorly understood
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
