Temporal stability of aboveground net primary production in northern Tibet alpine steppe in response to nitrogen addition

Abstract

The mechanism that sustains the temporal stability of aboveground net primary production (ANPP) respond to nitrogen deposition is still controversial. Consequently, we investigated the mechanism of temporal stability of ANPP through the effect of N addition on diversity, species asynchrony and portfolio effects in northern Tibet alpine steppe over a period of three years. Our results showed that the community temporal stability did not significantly correlate with the species richness and Shannon-Wiener diversity. Species asynchrony and stability was also not significantly affected by N addition (p > 0.05). Furthermore, there was no significant relationship between species asynchrony and temporal stability. Although the value of portfolio effects (z) (z = 1.304, 95% confidence intervals: 1.029–1.597) was more than 1, the portfolio effects was not a primary driver of temporal stability due to the biodiversity being unaffected. The above results suggested that the richness, species asynchrony and portfolio effect could not support for mechanism of stability at the alpine steppe. From the results of path analysis, species temporal stability positively supports the community temporal stability in the alpine steppe ecosystem. According to the character of environment and vegetation of alpine steppe at North Tibet, we inferred that dominance species stability is more important than species richness for the community temporal stability.