DOI: 10.5061/dryad.cm922
title: Data from: Drought-adapted plants dramatically downregulate dinitrogen fixation: evidences from Mediterranean legume shrubs

description: 1. The importance of symbiotic dinitrogen (N2) fixation in shaping the
 coupled nitrogen-carbon cycle is now known for most humid terrestrial
 ecosystems. However, whether N2 fixation can play a key role in the
 nitrogen and carbon budget of water-limited and seasonally dry ecosystems
 remains a mystery. 2. The maintenance of metabolically and physiologically
 costly symbiotic fixation in water-limited environments is highly complex.
 These costs are particularly high during the first developmental season,
 when allocation to deep rooting and drought-resistance mechanisms is
 essential for seedling survival of prolonged seasonal drought. 3. We
 therefore evaluated how drought-adapted legume species change their
 allocation to symbiotic nitrogen fixation as a function of soil nitrogen
 availability. We tested this on seedlings of a suite of four common
 Mediterranean legume shrubs with a strong seasonal behavior, which we grew
 under controlled nitrogen and phosphorus availabilities. We asked: (1) Do
 species differ in their investment and regulation of nitrogen fixation?
 (2) Is fixation regulated via plant allocation to nodules, fixation rate,
 or both? and (3) Does phosphorus availability limit symbiotic nitrogen
 fixation? 4. All Mediterranean perennial legumes in the experiment
 established and grew nodulated and fixed nitrogen, even under severe
 nitrogen limitation. The four species reacted similarly to nitrogen
 supply, by strongly downregulating fixation through both decreased
 nodulation and lower rate of fixation. However, we found a significant
 inter-specific difference in fixation (both nodulation and rate), biomass
 production and growth rate. Our experimental species presented a range of
 fixation investment strategies corresponding to life history and resource
 partitioning patterns. Phosphorus limitation had a minor influence on both
 fixation and plant growth. 5. Synthesis: the high physiological cost of
 symbiotic fixation imposes the need to tightly regulate fixation in
 perennial legumes coping with severe water stress and seasonal conditions.
 Control of fixation allows legume species to colonize recently disturbed
 nitrogen-deficient habitats, cope with grazing, survive long seasonal
 droughts and recover nitrogen fixation latter in the wet season, and
 survive over time by reducing nitrogen inputs to the ecosystem.
description: Dovrat et al 2018 JEcol
 - Plant biomass and nitrogen fixation dataThe table contains the
 data for all four species of legumes and three experimental treatments.
 Data includes total plant biomass, root nodule biomass, root mass fraction
 (RMF; Root/Total biomass), and estimated rate of fixation for the entire
 plant (according to acetylene reduction rate).Dovrat et al 2018 JEcol
 nitrogen fixation data.csvDovrat et al 2018 JEcol
 - Plant height growth dataThe table contains the
 data for all four species of legumes and three experimental treatments.
 Data includes the height of each plant measured repetitively along the
 experimental period. First day of height sampling varies by species,
 according to the rate of initial growth.Dovrat et al 2018 JEcol height
 growth data.csv