Status: this discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.
Higher response of terrestrial plant growth to ammonium than nitrate addition
Liming Yan1,2,Xiaoni Xu1,and Jianyang Xia1,2Liming Yan et al.Liming Yan1,2,Xiaoni Xu1,and Jianyang Xia1,2
1Tiantong National Field Observation Station for Forest Ecosystem & Center for Global Change and Ecological Forecasting, School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200062, China
2Institute of Eco-Chongming, Shanghai 200062, China
1Tiantong National Field Observation Station for Forest Ecosystem & Center for Global Change and Ecological Forecasting, School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200062, China
2Institute of Eco-Chongming, Shanghai 200062, China
Received: 13 Mar 2018 – Discussion started: 03 Apr 2018
Abstract. Terrestrial plant growth and ecosystem productivity are strongly limited by availability of nitrogen (N). Atmospheric deposition of wet N as nitrate and ammonium has been rapidly increased since the industrial revolution, associated with a high spatial variation of changes in the ammonium- to nitrate-N ratio (i.e., NH4+-N / NO3−-N). However, whether and how terrestrial plants respond differently to NH4+-N and NO3−-N addition have never been quantitatively synthesized. Here, we first did a literature survey and analysis on the model projections of future changes in NH4+-N / NO3−-N in atmospheric N deposition. Most models predicted an increase in the global average of NH4+-N / NO3−-N ratio, but decreasing trends in western Europe and eastern China. Then, a meta-analysis was applied to compare the different growth responses of 402 plant species to NH4+-N and NO3−-N addition from 217 N fertilization studies. In general, a greater response of plant growth to NH4+-N (+6.3 % g−1 N) than NO3−-N (+1.0 % g−1 N) addition was detected across all species. The larger sensitivity of plant growth to NH4+- than NO3−-N was found in all plant functional types except for grasses. In addition, the NO3−-N addition promoted terrestrial plants to allocate more biomass to above-ground, whereas NH4+-N addition significantly enhanced below- but not above-ground growth. These results imply that the global accelerating N deposition could stimulate plant growth more in regions with increasing (e.g., North America) than decreasing (e.g., eastern China) NH4+-N / NO3−-N ratio. The findings suggest future assessments and predictions on the vegetation response to atmospheric N enrichment could benefit from a better understanding of plant strategies for acquiring different forms of N.
The patterns of the ratio of atmospheric deposited ammonium- to nitrate-N shows an increasing trend with the total N load since the industrial revolution. As a key role of N in plant growth, it is important to know the general response patterns of plant growth to N forms. By the synthesized dataset and meta-analysis, we found a higher response of plant growth to NH4+-N than NO3−-N addition across all species. Our results suggest plant could more positively respond to N deposition in the future.
The patterns of the ratio of atmospheric deposited ammonium- to nitrate-N shows an increasing...