Relationships between plant nitrogen economy and life history in three deciduous-forest herbs

Rothstein, DE Zak, DR

De. Rothstein et Dr. Zak, Relationships between plant nitrogen economy and life history in three deciduous-forest herbs, J ECOLOGY, 89(3), 2001, pp. 385-394

27

INGLESE

Article

Environment/Ecology

JOURNAL OF ECOLOGY

0022-0477 → ACNP

89

3

2001

385 - 394

ISI

0022-0477(200106)89:3<385:RBPNEA>2.0.ZU;2-W

1 We compared nitrogen (N) uptake and whole-plant N dynamics in three decid uous-forest herbs of contrasting life histories: the spring ephemeral Alliu m tricoccum, the summergreen Viola pubescens and the semievergreen Tiarella cordifolia. We predicted that differences in above-ground physiology would translate into differences in N acquisition and partitioning, such that ni trogen-use efficiency (NUE) would increase from Allium to Viola to Tiarella . 2 Patterns of N uptake were generally the opposite of our predictions. Alli um had the lowest N uptake capacity in both laboratory and field experiment s whereas roots of Tiarella had the highest specific N uptake capacity. 3 Viola was the only species in which the specific uptake capacity of roots was related to photosynthetic activity of leaves, both decreasing by a fac tor of two from spring to summer. In contrast, Tiarella consistently had th e lowest photosynthetic capacity and the highest specific uptake capacity w hereas Allium maintained substantial root uptake capacity throughout the su mmer when it had no photosynthetic activity. 4 There were no significant differences between species in overall NUE. How ever, there were differences in the components of NUE: nitrogen productivit y (A) and mean residence time of N in the plant (MRT). Nitrogen productivit y increased, and MRT decreased, from Allium to Viola to Tiarella. 5 In all three species, there was a balance between acquisition of N and bu ilding of biomass over the annual growth cycle, despite dramatic disjunctio ns between the tissue-specific rates of carbon and N acquisition in Allium and Tiarella. The variation in A and MRT we observed among co-occurring spe cies of a single N-rich habitat was comparable with that observed by other researchers studying plants adapted to habitats of widely varying N availab ility.