Global carbon and nutrient cycles are linked via primary production, yet understanding of the role of plant life history, community diversity, and climate in constraining primary production response to nitrogen deposition remains uncertain. We asked whether across geographic and diversity gradients biomass production and distribution to above and belowground components consistently differs between communities dominated by short-lived and long-lived species. Compared to longer-lived species, short-lived species are generally smaller, have higher photosynthetic capacity, and higher proportion of photosynthetically active tissue per total mass. Accordingly, we predict short-lived dominated communities to have a steeper increase in total biomass, lower total biomass, and higher investment in aboveground biomass than communities dominated by longer-lived species. Resource conditions modify biomass production and distribution among organs, and it is expected that plants should allocate more biomass to the organ acquiring the most limiting resources. However, differences in the dominant life history of communities could contribute to differences in the effect nutrient addition have on biomass production and allocation. Thus, we assess the effect of nutrient addition on biomass allocation patterns of communities dominated by short- and long-lived species. Using experimental data on grasslands spanning a broad geographic range we test these hypotheses.
Results/Conclusions
This experiment replicated in 29 grasslands around the world shows that across diversity and edaphic nutrient gradients total biomass was higher in communities dominated by longer-lived species. In particular, biomass production increased more rapidly in communities dominated by short-lived species. Although, nutrient addition increased total biomass and the rate of biomass production of communities dominated by both long and short-lived species, the biomass production of communities dominated by short-lived species increased more rapidly with nutrient supply than communities dominated by long-lived species. Belowground allocation increased with increasing species richness and with cover of longer-lived species, but decreased among sites as growing season length increased. The aboveground biomass fraction increased with increasing growing season length and with increasing plot-scale annual plant cover. However, the aboveground biomass fraction was reduced with increasing species richness, perhaps reflecting the negative effects of competition for light resources. Experimental nutrient treatments seem to enhance the effect of life histories on biomass allocation to above and belowground components. Overall, patterns of biomass allocation and production between communities dominated by short-lived or long-lived plants differ, suggesting differences in the role of nutrient deposition for carbon inputs from these differing community types.