Effect of mowing management on ecosystem stability response to different forms of nitrogen addition in a saline-alkaline grassland

Background and aims

Nitrogen (N) addition affects plant biodiversity and community structure, subsequently altering the stability of above-ground net primary productivity (ANPP) in grassland ecosystems. However, the effect of adding different nitrogen compounds and their subsequent interactions with mowing on the stability of both below-ground net primary productivity (BNPP) and total net primary productivity (TNPP) are largely unknown.

Methods

This study compared the impact of adding two nitrogen compounds, NH₄NO₃ and urea, on the temporal stability of ANPP, BNPP, and TNPP in mowed and unmowed saline-alkaline grasslands.

Results

We found that the ANPP temporal stability in unmowed grasslands was not affected by NH₄NO₃ addition but increased with urea addition. Conversely, the ANPP temporal stability in mowed grasslands decreased with NH₄NO₃ addition and was not affected by urea addition. Mowing decoupled the ANPP and BNPP temporal stability responses to nitrogen addition. Without mowing, the BNPP temporal stability in response to adding different forms of nitrogen aligned with that of ANPP; however, with mowing, the BNPP temporal stability was not affected by adding NH₄NO₃ or urea, exhibiting an inconsistent trend of change in comparison to the ANPP temporal stability. The ANPP resistance indirectly regulates the response of the BNPP temporal stability to nitrogen addition in unmowed grasslands, whereas the BNPP temporal stability was not affected by plant above-ground indicators in mowed grasslands.

Conclusions

Overall, our study addresses the scarcity of research on ecosystem temporal stability in saline-alkaline grasslands and demonstrates that mowing management can regulate the effects of different forms of nitrogen addition on ecosystem stability.