Changes in Plant Nitrogen Resorption During Restoration in Inner Mongolia, China

Area of Science:

• Ecology
• Plant Ecology
• Restoration Ecology

Background:

• Nutrient resorption is vital for plants in nutrient-limited ecosystems.
• Long-term nutrient resorption dynamics in restored grasslands are not well understood.
• Tree and shrub planting is a common restoration strategy for degraded semi-arid grasslands.

Purpose of the Study:

• To investigate nutrient resorption efficiency (NRE) at community and functional group levels in grasslands restored with trees and shrubs over 20 and 40 years.
• To understand how functional group dynamics influence nutrient cycling during grassland restoration.
• To assess the impact of dominant plant functional groups on soil nutrient accumulation.

Main Methods:

• Measured nitrogen resorption efficiency (NRE) in green and senesced leaves.
• Analyzed leaf nitrogen concentrations and aboveground biomass.
• Assessed soil nutrient availability across different restoration sites (shrub-planted and tree-planted) in Inner Mongolia, China.
• Compared NRE and nutrient dynamics between plant functional groups (Poaceae, forbs, Fabaceae).

Main Results:

• Community-level NRE and biomass did not differ significantly across restoration sites.
• Poaceae showed higher NRE and lower senesced leaf nitrogen than forbs and Fabaceae.
• As restoration progressed, Poaceae dominance increased, correlating with higher soil nutrients.
• Poaceae NRE declined with increasing soil nutrients, indicating a shift to direct nutrient uptake.
• Dominant Poaceae species produced low-nitrogen litter, potentially slowing soil nutrient accumulation.

Conclusions:

• Functional group dynamics significantly regulate long-term nutrient resorption and cycling in restored grasslands.
• The shift towards Poaceae dominance and their reduced NRE may impede long-term soil nutrient enrichment.
• Managing Poaceae dominance is crucial for enhancing soil nutrient accumulation and biodiversity in restored semi-arid grasslands.