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. 2012;7(11):e50544.
doi: 10.1371/journal.pone.0050544. Epub 2012 Nov 28.

Alfalfa carbon and nitrogen sequestration patterns and effects of temperature and precipitation in three agro-pastoral ecotones of northern China

Shujuan Chang  1 , Nan Liu, Xiaoya Wang, Yingjun Zhang, Yue Xie
Affiliations

Alfalfa carbon and nitrogen sequestration patterns and effects of temperature and precipitation in three agro-pastoral ecotones of northern China

Shujuan Chang et al. PLoS One. 2012.

Abstract

Alfalfa (Medicago sativa L.) is a primary and widely cultivated forage crop in China. As a perennial leguminous grass, continuous planted alfalfa may influence carbon and nitrogen sequestration in soils. We evaluated the effect of alfalfa, planted for different lengths of time, and temperature and precipitation on soil organic carbon (SOC) and total nitrogen (TN) contents, and estimated soil SOC and TN inventories from 0-60 cm in three agro-pastoral ecotones of northern China. Alfalfa SOC and TN storage patterns were significantly different with increasing soil depths between the three regions of northern China. Continuous alfalfa grassland planted had a positive effect on accumulation of both SOC and TN in the Northwest region, whereas SOC storage peaked 6-7 years after planting in the Northeast and North region. Moreover, relatively higher TN storage appeared 7 years after planting in the Northeast and North regions. This study controlled as many factors as possible, but we caution that such temporal inferences could be artifacts of site selection. The regression analysis indicated that SOC and TN accumulation was mainly dependent on temperature (≥10°C of effective total accumulated temperature) in the North region. Precipitation in the growing season was the main limiting factor for SOC storage in the Northwest region and TN accumulation in the North regions. Therefore, the different climate factors affecting SOC and TN sequestration in alfalfa occurred at a regional scale.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Location of the study areas in China.
Figure 2
Figure 2. Annual precipitation (mm) and annual temperature (°C) in the three regions from 1985 to 2010.
The data from China Meteorological Date sharing Service System: http://cdc.cma.gov.cn/.
Figure 3
Figure 3. Mean soil bulk density in different soil layers from the three regions.
The value of standard error (s.e.) for each region was stated in the graph (n = 90 for Northwest, n = 108 for North and Northeast region).
Figure 4
Figure 4. Mean SOC and TN storage in different soil layers from the three regions.
The value of standard error (s.e.) for each region was stated in the graph (n = 150 for Northwest, n = 180 for North and Northeast region).
Figure 5
Figure 5. The relationship of soil organic carbon (SOC) and total nitrogen (TN) storage with years of growing alfalfa in North, Northeast and Northwest region of China.
Figure 6
Figure 6. Relationships between SOC or TN (0–60cm) and ≥10°C of the effective total accumulated temperature (Te) or total precipitation (mm) in the growing reason (Pg) in the North and Northwest region.
See this image and copyright information in PMC

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