Acknowledgements
We are grateful for the assistance of the Bawujiu Farm in Heilongjiang Province. The research described in this paper was made possible by the financial support of the National Natural Science Foundation of China (Grant No. 41371018), the Supporting Program of the “Twelfth Five-Year Plan” for Science and Technology Research of China (2012BAD15B05), the GLOCOM Project (grant no. PIRSES-GA-2010-269233), and the Fundamental Research Funds for the Central Universities.