Intraspecific Variation in Functional Traits of Medicago sativa Determine the Effect of Plant Diversity and Nitrogen Addition on Flowering Phenology in a One-Year Common Garden Experiment

Abstract

Nitrogen deposition and biodiversity alter plant flowering phenology through abiotic factors and functional traits. However, few studies have considered their combined effects on flowering phenology. A common garden experiment with two nitrogen addition levels (0 and 6 g N m−2 year−1) and five species richness levels (1, 2, 4, 6, and 8) was established. We assessed the effects of nitrogen addition and plant species richness on three flowering phenological events of Medicago sativa L. via changes in functional traits, soil nutrients, and soil moisture and temperature. The first flowering day was delayed, the last flowering day advanced, and the flowering duration shortened after nitrogen addition. Meanwhile, the last flowering day advanced, and flowering duration shortened along plant species richness gradients, with an average of 0.64 and 0.95 days change per plant species increase, respectively. Importantly, it was observed that plant species richness affected flowering phenology mainly through changes in plant nutrient acquisition traits (i.e., leaf nitrogen and carbon/nitrogen ratio). Our findings illustrate the non-negligible effects of intraspecific variation in functional traits on flowering phenology and highlight the importance of including functional traits in phenological models to improve predictions of plant phenology in response to nitrogen deposition and biodiversity loss.

Responses of Intraspecific and Interspecific Trait Variations to Nitrogen Addition in a Tibetan Alpine Meadow

“…The intraspecific variations of plant traits play an important role in determining the functional composition of communities in response to N enrichment [14,[28][29][30]. Li et al [31] showed that nutrient addition increased the CWMs of plant height (H) and SLA in an alpine meadow, with these changes mainly driven by intraspecific variation under high nutrient addition.…”

Periodical Progress in Ecophysiology and Ecology of Grassland

“…In a one-year plot experiment, Ma et al, (2023) [ 11 ] simulated combinations of different species compositions (1, 2, 4, 6 species and 8 species), and monitored the phenology of alfalfa and determined the related functional traits such as light acquisition traits (plant height and relative height, leaf mass and area, leaf length and width, and specific leaf area) and nutrient acquisition traits (leaf carbon content (LCC), leaf nitrogen content (LNC), leaf C/N ratio (LCC/LNC), biomass and abundance, relative biomass and abundance) after N addition. The results showed that the effect of N addition and plant diversity on flowering phenology was driven by the intraspecific variation in functional traits, and such alteration would influence the flower numbers and plant reproductive strategy.…”