Effects of nitrogen addition and precipitation alteration on soil

respiration and its components in a saline-alkaline grassland

作者：Huajie Diao, Xiaopeng Chen, Xiang Zhao, Kuanhu Dong*, Changhui Wang*

期刊：Geoderma

出版年份：2022

Abstract：

The responses of soil total respiration (Rs) and its components (soil autotrophic respiration (Ra) and heterotrophic respiration (Rh)) to nitrogen (N) deposition have been widely evaluated in non-saline-alkaline grasslands. However, their responses to N addition under drought and wet conditions, especially in saline-alkaline grasslands, remain unclear. A two-factorial experiment involving N addition and precipitation changes (decreased or increased 50% precipitation relative to ambient) was conducted in a saline-alkaline grassland of Northern China, while soil respiration was measured in different treatment plots during two growing seasons (2018, 2019). Results showed that the addition of N or changes in precipitation alone had no significant effect on Rs, Ra or Rh in both years because root productivity and soil microbial biomass were not affected. However, N addition with increased precipitation synergistically augmented seasonal mean Rs and Ra by 25.7% and 46.8% in 2018, and by 42.4% and 89.3% in 2019, respectively, owing to the increase in plant productivity. The variation in Ra primarily contributed to variation in Rs, and the effect size of N addition on Rs and Ra were increased with precipitation. In addition, a structural equation model showed that the response of soil respiration to N addition and precipitation changes was regulated by soil salinization, in which the Ra was regulated by soil based cations while Rh was controlled by soil pH values. Our study highlights that N addition with increased precipitation preferentially affects plants rather than microorganisms, and that Rh was not sensitive to N addition and precipitation changes in saline-alkaline grassland.

Conclusions：

Overall, N addition or altered precipitation alone had no significant effect on Rs, Rh, or Ra. However, N addition and 50% increased precipitation had a synergistic effect on Rs primarily through promotion of Ra caused by increased plant productivity. Our results showed that Rh was insensitive to short-term N input and altered precipitation. The effect of N addition on Ra was stronger under wet conditions compared with that under drought conditions, indicating that increases in precipitation will promote the effects of N deposition on Rs by accelerating Ra in the saline-alkaline grassland region of Northern China. In addition, results of the structural equation model suggested that N addition and precipitation increase could alleviate soil salinity, and thus regulated the response of soil respiration. Our study demonstrated that soil microbial characteristics (Rh, MBC) were not affected under high salinization and exhibited insensitivity to short-term N addition and altered precipitation in saline-alkaline grassland.

全文链接：doi.org/10.1016/j.geoderma.2021.115541