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4599593 
Journal Article 
Nitrogen addition and ecosystem functioning: Both species abundances and traits alter community structure and function 
Tatarko, AR; Knops, JMH 
2018 
0 
Ecosphere
ISSN: 0046-1237 
9 
1 
WOS:000425731000033 
Increased nutrient inputs can cause shifts in plant community composition and plant functional traits, both of which affect ecosystem function. We studied community- and species-level leaf functional trait changes in a full factorial nitrogen (N), phosphorus (P), and potassium (K) fertilization experiment in a semi-arid grassland. Nitrogen was the only nutrient addition to significantly affect leaf functional traits, and N addition increased community-weighted specific leaf area (SLA) by 19%, leaf chlorophyll content by 34%, height by 26%, and leaf dry matter content (LDMC) decreased by 11% while leaf thickness and toughness did not change significantly. At the species level, most species contributed to the community-weighted trait and increased in SLA, chlorophyll, height, and LDMC with N addition. These intraspecific changes in functional traits account for 51-71% of the community-level changes in SLA, chlorophyll, plant height, and LDMC. The remaining change is due to species abundance changes; the two most abundant species (Bouteloua gracilis and Carex filifolia) decreased in abundance with N addition while subdominant species increased in abundance. We also found annual variation in SLA, chlorophyll, plant height, and LDMC to be as important in influencing traits as N addition, likely due to differences in precipitation. Aboveground net primary productivity (ANPP) did not change significantly with N addition. However, N addition caused a 34% increase in leaf area index (LAI) and a 67% increase in canopy chlorophyll density. We demonstrate that nitrogen-induced changes in both functional traits and species abundances magnify ANPP changes in LAI and canopy chlorophyll density. Therefore, ANPP underestimates N addition-induced ecosystem-level changes in the canopy vegetation. 
community structure; community-weighted traits; functional trait; grassland ecology; nutrient addition