Effects of nitrogen addition and mowing on nitrogen- and water-use efficiency
of Artemisia frigida in a grassland restored from an abandoned cropland
作者：Huajie Diao,Paul Kardol, Kuanhu Dong* and Changhui Wang*
期刊：Journal of Plant Ecology
出版年份：2021
Abstract：
Aims Competition among plants in a community usually depends on their nitrogen (N)-use efficiency (NUE) and water-use efficiency (WUE) in arid and semi-arid regions. Artemisia frigida is an indicator species in heavily degraded grassland, however, how its NUE and WUE respond to N addition in different successional stages is still unclear, especially with mowing, a common management practice in semi-arid grasslands.
Methods Based on a long-term controlled experiment with N addition and mowing in an abandoned cropland from 2006 to 2013, we investigated the NUE and WUE of A. frigida in two patches (i.e. grass and herb patches) in 2013 which represented two potential successional stages from herb to grass communities. The coverage of A. frigida was higher (about 50%) in the herb patch than in the grass patch (about 10%). Stable isotopic C (δ13C) and N (δ15N) as well as C and N pools were measured in plants and soils. NUE was calculated as leaf C/N, and leaf δ13C values were used as a proxy for WUE.
Important Findings N addition did not affect WUE of A. frigida, but significantly decreased NUE by 42.9% and 26.6% in grass and herb patches, respectively. The response of NUE to N addition was related to altering utilization of different N sources (NH4+ vs. NO3−) by A. frigida according to the changed relationship between leaf δ15N/soil δ15N and NUE. Mowing had no effect on NUE regardless of N addition, but significantly increased WUE by 2.3% for A. frigida without N addition in the grass patch. The addition of N reduced the positive effect
of mowing on its WUE in grass patch. Our results suggested that decreased NUE and/or WUE of A. frigida under mowing and N addition could reduce its competition, and further accelerate restoration succession from the abandoned cropland to natural grassland in the semi-arid region.
Conclusions：
N addition had no effect on WUE of A. frigida, but decreased its NUE, which was related to the difference in utilization of N resources (NO3− and NH4+). Mowing had no effect on the NUE of A. frigida regardless of N addition, while it improved WUE without N addition in the grass patch by decreasing SM. Mowing did not alter the effect of N addition on NUE, while the addition of N mediated the positive effect of mowing on WUE in the grass patch due to the unchanged SM in the N addition plus mowing treatment. There was no tradeoff between the NUE and WUE of A. frigida, suggesting that A. frigida could regulate its NUE and WUE to adapt to changes in resources and environment. We highlighted that A. frigida could alter the absorption of N source to adapt to differences in soil N status, and N addition plus mowing treatment (maintained lower NUE and WUE in the grass patch) could accelerate restoration succession from the abandoned cropland to natural grassland. This experiment presented a general pattern of WUE and NUE of A. frigida based on the indicative role of δ13C and δ15N, which provided a scientific basis for studying ecosystem nutrient utilization and community succession under N enrichment and mowing.
全文链接：doi:10.1093/jpe/rtab006.
