Correzioni

IPCC had made it clear that the globle's climate warming effect was mainly due to greenhouse gases emission, especially from CO2(Bohannon 2007).

The atmospheric carbon dioxide (CO2) concentration has been shown to be increasing at the annual rate of 0.5% due mainly to fossil fuel combustion and land-use changes since the 1850s(Ding, Meng et al. 2007).

Farmland, as an important part of terrestrial ecosystem, occupied a large proportion of greenhouse emission(Petersen, Thomsen et al. 2010).

Due to unreasonable fertilization, irrigation and so on, the content of SOC in the cropland soil had a massive decrease in the world and mainly in the way of CO2 into the atmosphere ( Lal, R et al).

So there were a large number of studies about Soil organic-C sequestration (Manna, Swarup et al. 2007; Studdert, Monterubbianesi et al. 2011; Wang, Chen et al. 2011; Guo, Wu et al. 2012).

It had aroused a growing concern of agronomists and ecologists for how to guarantee the production, increased soil organic matter content(Guo, Liu et al. 2010; Liu, You et al. 2010).

China has a late start but fast pace about the research of soil organic-C sequestration and on the different regions and different types of soil carbon sequestration had an increasingly researches (Yin and Cai 2006; Li, Velde et al. 2011).

However, more of studies lied in a dense region of China's agricultural development, such as the North China Plain, Loess Plateau and South of Paddy Soil(Hao, Fan et al. 2007; Li and Zhang 2007; Huang, Hu et al. 2009; Zhang, Wang et al. 2009; Ma, Yang et al. 2011; Niu, Hao et al. 2011).

China's western region has very few researches especially in northwest oasis farmland about soil carbon sequestration.

As the economic development of China, more and more money invest into the western of China (Agricultural Yearbook, 2000-2008).

The oasis cropland had become the local pillar industries and to be the important exporter of agricultural products in China.

Such as, oasis farmland produced one third amount of cotton in China and 8% in the word and rank first to be the most important commodity cotton base in China (Liu, Wang et al. 2000).

Fruits and vegetables are also very important for the Chinese agricultural market.

Secondly, Oasis farmland climatic conditions have characteristics significantly different from other places, such as drought, huge evaporation, intense mineralization of organic matter, etc.,(Luo, Yang et al. 2006; Sang 2009; Jiang, Hu et al. 2011; Liu, Duan et al. 2011; Yang, Chen et al. 2012).

The yield and soil organic-C sequestration will have a unique feature.

Thirdly, oasis farmland is in a process of development, continuously adjusted, unstable oasis agro-ecosystems due to the arable land expand and the huge fertilization input (Wang, Li et al.2002).

So it is necessary to learn about the dynamics of yield and the inputs and outputs condition of soil organic-C.