Biomass production, N:P ratio and nutrient limitation in a Caucasian alpine tundra plant community

Abstract

AbstractQuestions:1. To what extent is biomass production of a Caucasian alpine tundra plant community limited by soil nitrogen and/ or phosphorus? 2. Can the foliar N:P ratio predict the nutrient limitation pattern of alpine vascular plant communities?Location:Lichen‐rich tundra on Mt. Malaya Khatipara in the NW Caucasus, Russia (43°27’N, 41°42’E; alt. 2800 m a.s.l.).Methods:We conducted a 4–year fertilization experiment (N, P, N+P, lime additions and irrigation) on the alpine tundra in the northwestern Caucasus, Russia. We determined responses of biomass, tissue nutrient concentrations and nutrient pools of the above‐ground component of the plant community.Results:Total plant community biomass did not respond to fertilization. However, lichen biomass strongly decreased in response to the N‐ and N+P treatments, whereas vascular plant biomass increased in response to the N‐ and even more to the N+P treatment, but not to P or lime addition or irrigation. P‐concentrations in vascular plant species were very low, but their biomass production was not principally P‐limited, suggesting adaptation to low soil P‐availability. The N‐limitation of vascular plant biomass production in the community, which in lowlands usually occurs at N:P ratios below 16, could not be predicted from the mean foliar N:P mass ratio in the control (N:P = 29).Conclusions:This Caucasian alpine plant community is an example of N‐ and P‐co‐limitation of vascular plant biomass production, with N being the principal and P the secondary limiting nutrient. Critical N:P ratios as determined for lowland communities are not applicable here.