Effects of increased precipitation and nitrogen addition on community structure and soil C cycling during old-field grassland succession

With the implementation of National “Grain for Green” in China in recent years, the areas of old-field has increased all over the country. When agriculturally degraded lands are abandoned and undergo ecological succession, plant species composition and community dynamics will change over time and consequently affect ecosystem function and service. Soil water and nitrogen (N) availability are primary limitation factors in regulating plant growth, which alters species competition and strongly determines plant community succession. In view of the shifts in global and regional precipitation regimes and widespread nitrogen (N) deposition under global change, it is reasonably expected that changes in precipitation amount and atmospheric N deposition can further can further affect the dynamic change of plant community structure and ecosystem carbon (C) cycling along succession. Therefore, this study was conducted in an old-field grassland in North China Plain to explore successional change of plant community and ecosystem C cycling in response to increased precipitation and N deposition.

 

This experiment was randomly assigned to four treatments, with each treatment having six replicates. The four treatments included: control (C), increased precipitation (P), nitrogen addition (N), and increased precipitation plus nitrogen addition (PN). Twenty-four plots (4 × 6 m²) were arranged into four rows and six columns, with 1-m-wide walkways between plots. In the water addition plots, thirty percent more than ambient precipitation was added after each rainfall event from April to October. The level of N addition rate with 10 g N m^-2 year^-1 at this site was according to the maximum deposition values reported in previous study in northern China. Since 2012, 2g N m^-2 was applied after the first rainfall date of each month as NH₄NO₃ from May to September.