title: Plant community responses to precipitation and spatial pattern of nitrogen supply in an experimental grassland ecosystem.
abstract: Recent work suggests that soil nutrient heterogeneity may modulate plant responses to drivers of global change, but interactions between N heterogeneity and changes in rainfall regime remain poorly understood. We used a model grassland system to investigate the interactive effects of N application pattern (homogeneous, heterogeneous) and precipitation-magnitude manipulation during the growing season (control, +50 % rainfall, -50 % rainfall) on aboveground biomass and plant community dominance patterns. Our study resulted in four major findings: patchy N addition increased within-plot variability in plant size structure at the species level, but did not alter total aboveground biomass; patchy N addition increased community dominance and caused a shift in the ranking of subordinate plant species; unlike community-level biomass, plant species differed in their biomass response to the rainfall treatments; and neither aboveground biomass nor community dominance showed significant interactions between N pattern and rainfall manipulation, suggesting that grassland responses to patchy N inputs are insensitive to water addition or rainfall reduction in our temperate study system. Overall, our results indicate that the spatial pattern of N inputs has greater effects on species biomass variability and community dominance than on aboveground production. These short-term changes in plant community structure may have significant implications for longer-term patterns of vegetation dynamics and plant-soil feedbacks. Moreover our results suggest that the magnitude of precipitation during the growing season plays a limited role in grassland responses to heterogeneous organic N inputs, emphasizing the need to consider other components of precipitation change in future heterogeneity studies.
authors.affiliation: Grassland Ecosystem Research Unit, INRA-UREP, 5 Chemin de Beaulieu, 63039, Clermont-Ferrand, France.
authors.forename: Nianxun
authors.initials: N
authors.lastname: Xi
authors.forename: Pascal
authors.initials: P
authors.lastname: Carrère
authors.forename: Juliette M G
authors.initials: JM
authors.lastname: Bloor
mesh_terms: D018533:Biomass; D065948:Grassland; D009584:Nitrogen / Q000378:metabolism*; D018521:Plant Physiological Phenomena; D010944:Plants / Q000378:metabolism; D011891:Rain; D012621:Seasons; D012987:Soil / Q000737:chemistry
chemical_list: D012987:Soil; D009584:Nitrogen