Losses in Carbon and Nitrogen Stocks in Soil Particle-Size Fractions along Cultivation Chronosequences in Inner Mongolian Grasslands
- Nianpeng He *ab,
- Yunhai Zhangb,
- Jingzhong Daic,
- Xingguo Hand and
- Guirui Yua
- a Key Lab. of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences (CAS), Beijing 100101, China
b State Key Lab. of Vegetation and Environmental Change, Institute of Botany, CAS, Beijing 100093, China
c College of Ecology and Environmental Science, Inner Mongolia Agricultural Univ., Hohhot, Inner Mongolia 010018, China
d State Key Lab. of Forest and Soil Ecology, Institute of Applied Ecology, CAS, Shenyang, Liaoning 110016, China. Assigned to Associate Editor Pierre Benoit
Cultivation in semiarid grasslands induces large changes in soil organic matter (SOM) stock. To better predict the effects of cultivation on SOM pools, there is a need to identify the soil fractions that are affected and the extent to which they are affected. Using four cultivation chronosequences in Inner Mongolian grasslands of northern China, we investigated the changes in soil organic carbon (SOC) and total nitrogen (N) stocks in soil particle-size fractions to identify the effect of cultivation on SOM dynamics. The results showed that conversion of native grasslands into croplands significantly decreased the SOC stocks (4.34–31.65 Mg C ha−1) and N (0.19–2.54 Mg N ha−1) in the 0- to 100-cm layer after cultivation. Prominent changes were observed in the SOC and N stocks in the 0- to 10-cm layer and were, on average, 6.56 Mg C ha−1 (24.85%) and 0.63 Mg N ha−1 (23.48%), respectively. The effect of cultivation on the SOC and N stocks in soil fractions was in the order sand > silt > clay. The C and N stocks in the 0- to 10-cm soil layer in the sand fraction in croplands decreased, on average, by 4.74 Mg C ha−1 (35.86%) and 0.48 Mg N ha−1 (41.30%), respectively, compared with those in native grasslands. The declines in the silt and clay fractions were small. Thus, sand fraction was a more important contributor to C and N losses in soil after cultivation than silt or clay fraction. Our findings indicate that the preliminary responses of SOC and N to cultivation in a semiarid grassland area and have significant implications for assessing the loss or gain of C and N during grassland conversion.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2012. . Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.