Differential nitrogen cycling in semiarid sub-shrubs with contrasting leaf habit

• Published in: PloS one 2014-03, Vol.9 (3), p.e93184-e93184
• Main Authors: Palacio, Sara, Maestro, Melchor, Montserrat-Martí, Gabriel
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Arid regions; Biology and Life Sciences; Biomass; Botany; Cycles; Drought; Earth Sciences; Ecology and Environmental Sciences; Ecosystems; Environmental changes; Flowers & plants; Foliage; Labeling; Labelling; Leaves; Lepidium - metabolism; Leptosomatum subulatum; Mineralization; Morphology; Nitrogen; Nitrogen Cycle; Organs; Phenology; Phenotype; Plant growth; Plant Leaves - metabolism; Plant sciences; Plant Shoots - metabolism; Seasons; Senescence; Shrubs; Species; Stems; Studies; Summer; Woody plants
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0093184

Nitrogen (N) is, after water, the most limiting resource in semiarid ecosystems. However, knowledge on the N cycling ability of semiarid woody plants is still very rudimentary. This study analyzed the seasonal change in the N concentrations and pools of the leaves and woody organs of two species of semiarid sub-shrubs with contrasting leaf habit. The ability of both species to uptake, remobilize and recycle N, plus the main storage organ for N during summer drought were evaluated. We combined an observational approach in the field with experimental (15)N labelling of adult individuals grown in sand culture. Seasonal patterns of N concentrations were different between species and organs and foliar N concentrations of the summer deciduous Lepidium subulatum were almost double those of the evergreen Linum suffruticosum. L. subulatum up took ca. 60% more external N than the evergreen and it also had a higher N resorption efficiency and proficiency. Contrastingly, L. suffruticosum relied more on internal N remobilization for shoot growth. Differently to temperate species, the evergreen stored N preferentially in the main stem and old trunks, while the summer deciduous stored it in the foliage and young stems. The higher ability of L. subulatum to uptake external N can be related to its ability to perform opportunistic growth and exploit the sporadic pulses of N typical of semiarid ecosystems. Such ability may also explain its high foliar N concentrations and its preferential storage of N in leaves and young stems. Finally, L. suffruticosum had a lower ability to recycle N during leaf senescence. These strategies contrast with those of evergreen and deciduous species from temperate and boreal areas, highlighting the need of further studies on semiarid and arid plants.