Document: JUL-3-33-18

The effect of litter quality on neighbor growth is dependent on nitrogen availability: Evidence from a greenhouse experiment with two alpine co-dominants.

LARSON, J.R.*, K.N.SUDING and W.D.BOWMAN

University of Colorado, Boulder, Colorado 80309-0334 USA ¹

Abstract:
Although it is well accepted that differences in plant species litter quality influence soil nitrogen cycling, it is less well understood what effect this has on the growth of neighboring species. We addressed this question by examining the effects of litter of two alpine community co-dominants, Acomastylis rossii and Deschampsia caespitosa. Acomastylis litter has significantly higher C:N ratio and phenolic concentration than Deschampsia litter, which is associated with lower rates of net N mineralization. In addition, we examined whether the effect of litter was dependent on N supply (high, low) by measuring the biomass production of Deschampsia tillers grown with 3 litter treatments (Acomastylis, Deschampsia, and none). We hypothesized that Acomastylis litter would inhibit growth at low N supply, but increasing N supply would overcome the inhibitory effects. Alternatively, the high phenolic concentrations in Acomastylis litter may directly inhibit growth independent of N availability. Acomastylis litter significantly decreased the growth of Deschampsia at low N supply compared to growth either in the absence of litter or in the presence of Deschampsia litter. The influence of Acomastylis litter on biomass production of Deschampsia was significantly less under high N supply. Acomastylis litter also significantly increased biomass turnover. These results suggest that Acomastylis litter inhibits the growth of Deschampsia by restricting N supply, rather than through a direct effect of phenolics.

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This abstract is being presented at: 3:30 PM in session:
Poster Session #15: Nutrient Cycling.