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. 2019 Nov 6;9(1):16088.
doi: 10.1038/s41598-019-52631-6.

Deep soil C and N pools in long-term fenced and overgrazed temperate grasslands in northwest China

Jian-Ping Li  1 , Hong-Bin Ma  2 , Ying-Zhong Xie  2 , Kai-Bo Wang  3 , Kai-Yang Qiu  2
Affiliations

Deep soil C and N pools in long-term fenced and overgrazed temperate grasslands in northwest China

Jian-Ping Li et al. Sci Rep. .

Abstract

Fencing for grazing exclusion has been widely found to have an impact on grassland soil organic carbon (SOC) and total nitrogen (TN), but little is known about the impact of fenced grassland on the changes in deep soil carbon (C) and nitrogen (N) stocks in temperate grasslands. We studied the influence of 30 years fencing on vegetation and deep soil characteristics (0-500 cm) in the semi-arid grasslands of northern China. The results showed that fencing significantly increased the aboveground biomass (AGB), litter biomass (LB), total biomass, vegetation coverage and height, and soil water content and the SOC and TN in the deep soil. The belowground biomass (BGB) did not significantly differ between the fenced and grazed grassland. However, fencing significantly decreased the root/shoot ratio, forbs biomass, pH, and soil bulk density. Meanwhile, fencing has significantly increased the C and N stocks in the AGB and LB but not in the BGB. After 30 years of fencing, the C and N stocks significantly increased in the 0-500 cm soil layer. The accumulation of SOC mainly occurred in the deep layers (30-180 cm), and the accumulation of TN occurred in the soil layers of 0 to 60 cm and 160 to 500 cm. Our results indicate that fencing is an effective way to improve deep soil C and N stocks in temperate grassland of northwest China. There were large C and N stocks in the soil layers of 100 to 500 cm in the fenced grasslands, and their dynamics should not be ignored.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
(a) Soil water content (SWC) and (b) soil bulk density (BD) in fenced grassland (FG) and grazed grassland (GG). Note: the values are mean ± SD; difference significant was represented by asterisk (P < 0.05, denoted by *P < 0.01, denoted by **P > 0.05, denoted by NS).
Figure 2
Figure 2
(a) Soil organic carbon (SOC) and (b) soil total nitrogen (TN) in fenced grassland (FG) and grazed grassland (GG). Note: the values are mean ± SD; difference significant was represented by asterisk(P < 0.05, denoted by *P < 0.01, denoted by **P > 0.05, denoted by NS).
Figure 3
Figure 3
(a) C and (b) N stock of AGB, LB, BGB and total vegetation in fenced grassland (FG) and grazed grassland (GG). AGB, LB and BGB represent aboveground biomass, litter biomass and belowground biomass, respectively. Note: the values are mean ± SD; difference significant was represented by asterisk(P < 0.05, denoted by *P < 0.01, denoted by **P < 0.001, denoted by ***P > 0.05, denoted by NS).
Figure 4
Figure 4
(a) C stock and (b) N stock of belowground biomass (BGB) in different soil layers of fenced grassland (FG) and grazed grassland (GG). Note: the values are mean ± SD; difference significant was represented by asterisk (P < 0.05, denoted by *P > 0.05, denoted by NS).
Figure 5
Figure 5
(a) Soil C and (b) N stock in different soil layers of fenced grassland (FG) and grazed grassland (GG). Note: the values are mean ± SD; difference significant was represented by asterisk (P < 0.05, denoted by *P < 0.01, denoted by **P < 0.001, denoted by ***P > 0.05, denoted by NS).
Figure 6
Figure 6
(a) Cumulative soil C storage and (b) cumulative soil N storage in fenced grassland (FG) and grazed grassland (GG). Note: the values are mean ± SD; difference significant was represented by asterisk (P < 0.05, denoted by *P < 0.01, denoted by **P < 0.001, denoted by ***P > 0.05, denoted by NS).
Figure 7
Figure 7
Annual rates of (a) SOC stock and (b) TN sequestration.
Figure 8
Figure 8
(a) Ecosystem carbon (C) and (b) nitrogen (N) pools in different soil layers. Note: values are the mean ± SD; significant differences in the C or N pools between the FG and GG treatments are indicated by asterisk (P < 0.01, denoted by **P < 0.001, denoted by***).
Figure 9
Figure 9
Soil samples in (a) FG and (b) GG from 0 to 500 cm.
Figure 10
Figure 10
Location of the study site on the Loess Plateau.
See this image and copyright information in PMC

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