On the link between nitrogen productivity and residence time: two opposite nitrigen use strategies?

GOLLUSCIO, R.A.

JOURNAL OF ARID ENVIRONMENTS

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2007 vol. 68 p. 165 - 169

0140-1963

NUE, i.e. the net primary production (NPP) per unit ofnitrogen absorbed, can be calculated as the product between nitrogenproductivity (NP) and residence time of nitrogen in the plant (RT). NP is theratio between NPP and the amount of nitrogen in biomass, and RT is the ratiobetween such amount of N in the biomass and the amount of N absorbed. It hasbeen hypothesized that plants maximize NUE by two different strategies: plantsof nitrogen-rich sites have a high NP, and plants of nitrogen-poor sites have ahigh RT. However, the information about the variation of NP and RT alonggradients of N availability is often conflictive with such hypothesis. We showthat NP is directly correlated with biomass turnover rate (BTR), but RT isinversely correlated with BTR, and that other variables have also influence onboth terms of NUE: plant N concentration (PNC), N resorption efficiency (NRE),and relative N concentration of leaves respect to the entire plant (RLNC). As aconsequence, when comparing species with very different BTR, the RT vs. NP oppositionbecomes evident, as in adaptive comparisons between species of highlycontrasting habitats. Instead, the negative association between NP and RT maydisappear when comparing species of similar BTR, as when studying plasticresponses within a single species, because the differences in PNC, NRE and/orRLNC may overshadow the differences in BTR.