Reproductive height, not vegetative height, determines the loss of
clonal grasses with nitrogen enrichment in a temperate grassland
Abstract
Tall clonal grasses commonly display competitive advantages with
nitrogen (N) enrichment. However, it is currently unknown whether their
height is derived from the vegetative or reproductive module. Moreover,
it is unclear whether the height of the vegetative or reproductive
system regulates the probability of extinction and colonization, and
determines species richness (frequency). In this study, the impacts on
clonal grasses were studied in a field experiment employing two
frequencies (twice a year or monthly) crossed with nine N addition rates
in a temperate grassland. We found that the N addition decreased species
frequency and increased extinction probability, but did not change the
species colonization probability. A low frequency of N addition
decreased species frequency and colonization probability, but increased
extinction probability. Species reproductive height is the best index to
predict the extinction probability of clonal grasses in N-enriched
conditions relative to the vegetative height, average height, and
species biomass. No significant relationships were detected between
plant height and species colonization probability. The low frequency of
N addition may overestimate the negative effect from N deposition on
clonal grass diversity, suggesting that a higher frequency of N addition
is more suitable in assessing the ecological effects of N deposition.
Moreover, this study illustrates that reproductive height, not the
vegetative height, was associated with the clonal species extinction
probability under N-enriched environment.