科研之友
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摘要
In this paper,the carbon and nitrogen stoichiometric amounts of plant-soil system were investigated along with the restoration sequence of degraded vegetation in Horqin Sandy Land, Inner Mongolia, China. This would be helpful to definite the changes of carbon-nitrogen stoichiometric amounts of plant-soil system in the restoration of degraded vegetation and quantify the relationship between carbon-nitrogen stoichiometric amounts and species richness, which provided the theoretical foundation for the sustainable management and utilization of sandy grassland. A total of 24 plots with the size of 20 m × 20 m were set up at four habitats (mobile dune, semi-fixed dune, fixed dune and grassland),each habitat had 6 replicated plots. The distance between each plot was in the range from 0.5 to 8 km. Three quadrats with the size of 1 m × 1 m were selected for plant and soil sampling in each plot in mid-August of 2011,2013 and 2015. Then the C and N contents of plant-soil system were analysed by Costech Elemental Combustion System 4010,Italy. The resluts shown as follows: (1) With the restoration of degraded vegetation,the C and N contents and C/N ratios of aboveground plant, litter and root had a fluctuated change trend, while the C and N content and C/N ratio of soil (0 ~ 10 cm) was increased significantly (P < 0. 05). The N content of aboveground plant in mobile dune was the highest,thus the C/N ratio was much lower than other habitats. On the other hand,the N contents of litter and root in semi-fixed dune were relatively lower than other habitats, which led to the higher C/N ratios of litter and root in semi-fixed dune. (2) From 2011 to 2015,the average C content of above ground plant changed a little,while the N content was significantly increased (P <0. 01). The C and N content and C/N ratio of litter fluctuated smoothly,while there was no significant difference of that for root between years. On the other hand, the C content and C/N ratio of soil changed undulately,but the N content was increased significantly (P <0. 01). (3) The C/N ratio of aboveground plant, litter, soil had positive linear relationship with species richness in the restoration process of degraded vegetation (P <0. 01). In conclusion, the succession of dominant vegetation in the restoration process of degraded vegetation led to the changes of C and N stoichiometric amounts of plant-soil system,the N use efficiency was also increased with the restoration of degraded vegetation. Moreover, the increase of fencing time promotes the accumulation of soil N in sandy land.
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