Responses of plant phenology to nitrogen addition: A meta-analysis
18 April 2019Wang, Chao; Tang, Yujia
Phenology is one of the most sensitive plant processes in response to global change. Anthropogenic activities have considerably increased nitrogen (N) deposition, which significantly affects plant phenology. Although numerous individual studies have been conducted, a comprehensive understanding of how plant phenology responds to external N inputs remains elusive. We therefore conducted a meta-analysis of 117 species responses to N addition to examine effects on phenology in terrestrial ecosystems, and we assessed variations in their responses in relation to ecosystem types, pollination types, functional groups, and environmental conditions. Our results showed that many aspects of plant phenology changed significantly after N addition, as events occurred later and durations were shorter across all biomes, but varied with biome types. The phenology change in cropland was larger than that in grassland after N addition. The response of phenological stages to N addition was consistent in two pollination types except the flowering time, which had no change in wind-pollinated species but was significantly delayed in insect-pollinated species. In addition, the response of phenology to N addition was not consistent among functional groups. The timing of events was advanced (earlier) in sedges, whereas the timing was delayed (later) in grasses, legumes, and forbs. We also found that local environmental factors had minimal effect on the response of plant phenology to N addition, but a significant correlation was found among the response ratio of different phenological stages. Our study suggest that plant phenology was sensitive to N deposition, but the influence of N deposition on plant phenology was not changed easily by local environmental factors, which may need to be incorporated into regional and global models for predicting effects of N addition on plant phenology.