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Divergent trait responses to nitrogen addition in tall and short species

Citation

Cheng, Yikang et al. (2022), Divergent trait responses to nitrogen addition in tall and short species, Dryad, Dataset, https://doi.org/10.5061/dryad.xsj3tx9jj

Abstract

Asymmetrical light competition has been proposed as the main driving force of species richness decline under nitrogen (N) addition. N addition is known to cause a series of correlated changes in functional traits, with functional composition shifting due to increased dominance of tall and resource acquisitive species. However, whether trait changes vary between species and, in particular, how the traits of tall and short species respond to N addition has rarely been studied.

We measured traits on species in a long-term (10 years) N addition experiment. We first measured the height of 44 plant species and photosynthetic active radiation (PAR) at seven community heights in unfertilized plots. We identified a clear stratification of the plant community into tall species (>30cm tall) which experienced high light conditions and short species that grew under the canopy. We then measured four functional traits, including maximum plant height, specific leaf area, leaf dry matter content and leaf thickness, on 35 species that occurred along the N addition gradient. We then tested whether functional trait, species richness and phylogenetic structure responses varied between tall and short species.  

We found different responses of traits and diversity to N addition for the tall and short species. N addition reduced the number of short species but increased the number of tall species, providing more evidence that short species are more likely to be lost following N addition. In addition, specific leaf area increased and leaf dry matter content decreased for short species only, suggesting that they shifted to a more acquisitive light acquisition strategy to cope with lower light levels. In contrast, tall species increased their height further to capture more light at the top of canopy.  

Synthesis. The divergent trait responses observed for tall and short species show that although certain traits like height and resource economics traits show correlated responses at the whole community level, these correlations may not be consistent across all species. Together, our results highlighted that strata-dependent assessments of community structure are needed to fully understand how global change factors influence plant diversity and interaction.

Funding

National Natural Science Foundation of China