Increased community compositional dissimilarity alleviates species loss following nutrient enrichment at large spatial scales

Aims Anthropogenic activities have drastically increased nutrient availability, resulting in declines in species richness in many plant communities. However, most previous studies have explored only species-loss patterns and mechanisms over small sampling areas, so their results might overestimate species loss at larger spatial scales. The aim of this research was to explore species diversity change patterns and species-loss rates at multiple scales in alpine meadow communities following nutrient enrichment. Specifically, we asked two closely related questions: (i) do changes in species diversity and species-loss patterns differ among spatial scales? and (ii) how does community compositional dissimilarity and species turnover change among spatial scale? Methods This study was implemented in an alpine meadow community, which is regarded as one of the most sensitive and vulnerable terrestrial ecosystems to anthropogenic nutrient enrichment. We conducted a fertilization experiment that involved the addition of nitrogen (N), phosphorus (P) and a mixture of both to a series of quadrats ranging from 1 to 16 m(2) over 5 years to study the variations in the patterns of species diversity in response to nutrient additions at different spatial scales. Important Findings Our results showed that the changes in species diversity and species loss were dependent on the type of fertilization and the spatial scale. After N and NP fertilization, species diversity significantly decreased at the small scale but not at the large scale, and the rate of species loss decreased as the spatial scale increased. In contrast, the differences between the P addition and control communities were negligible at both the small and large spatial scales. N fertilization caused species to be lost from the small sampling scale, but because different species were lost from different samples, there was an increase in compositional dissimilarity at larger spatial scales, which reduced the total number of species lost when measured at larger scales. These findings highlight spatial scale in evaluating the biodiversity loss after fertilization and suggest that the compositional dissimilarity might play an important role in mediating species loss after fertilization. Our study significantly improved our understanding of changes in species diversity and species loss at different spatial scales under nutrient-enrichment scenarios.