PARENT SESSION
Contributed Oral Session 142: Biodiversity and Nitrogen
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 521 A, Level 5, Palais des congrès de Montréal

A negative relationship between species richness and productivity response to N addition in a synthesis of N fertilization studies.

Fargione, Joseph^*,1, Pennings, Steven², Clark, Christopher³, Suding, Katherine⁴, Gough, Laura⁵, Grace, James⁶, Cleland, Elsa⁴, Collins, Scott¹, Gross, Katherine⁷, ¹ University of New Mexico, Albuquerque, NM² University of Houston, Houston, TX³ University of Minnesota, St. Paul, MN⁴ University of California, Irvine, CA⁵ University of Texas, Arlington, TX⁶ National Wetlands Research Center, Lafayette, LA⁷ Michigan State University, MI

ABSTRACT- It has previously been found that productivity response to N addition was greatest in species rich assembled communities (Reich et al. 2001). However, the direct effects of diversity observed in experimentally assembled communities are often swamped by extrinsic factors that covary with species richness across natural diversity gradients. For example, the relationship between diversity and productivity in manipulative experiments is commonly positive, but the relationship between diversity and productivity across natural diversity gradients is commonly negative. We are unaware of any studies on the relationship between diversity and N response across natural diversity gradients. Here we present results from a synthesis of N fertilizer addition studies. We show that species rich communities had a smaller biomass response to N additions. Our results do not contradict previous work in manipulative studies, which suggest that loss of diversity from a community may reduce the ability of that community to respond to N addition. Rather, our results suggest that, at the landscape scale, the productivity response of communities to N addition will be negatively correlated with species richness.

Key words: biodiversity, nitrogen, fertilization, synthesis