Abstract
Desert shrubs, a dominant component of desert ecosystems, need to maintain sufficient levels of nutrients in their different organs to ensure operation of various physiological functions for the purpose of survival and reproduction. In the present study, we analyzed 10 elements in leaves, stems, and roots of 24 dominant shrub species from 52 sites across a temperate desert ecosystem in northwestern China. We found that concentrations of all 10 elements were higher in leaves than in stems and roots, that non-legumes had higher levels of leaf Na and Mg than did legumes, and that Na was more concentrated in C4 leaves than in C3 leaves. Scaling relationships of elements between the photosynthetic organ (leaf) and non-photosynthetic organs (stem and root) were allometric. Results of principal components analysis (PCA) highlighted the important role of the elements responsible for osmoregulation (K and Na) in water utilization of desert shrubs. Soil properties and taxonomy explained most variation of element concentrations in desert shrubs. Desert shrubs may not be particularly susceptible to future change in climate factors, because most elements (including N, P, K, Ca, Mn, Zn, and Cu) associated with photosynthesis, osmoregulation, enzyme activity, and water use efficiency primarily depend on soil conditions.
Highlights
Nutrient levels among different organs of desert shrubs[11,12], and the mechanism of element status in desert shrubs remains elusive
For Na and Mg, significant interactions were observed between N-fixation types and plant organs: there was no significant concentration differences between legumes and non-legumes in non-photosynthetic organs; but this is not true for leaves, for which concentrations of both elements were significantly higher in non-legumes than in legumes (Fig. 1)
Desert shrubs generally invest a large fraction of biomass to belowground organs for the purpose of acquisition of water and nutrients; the high fraction of biomass in roots inherently indicates that a substantial amount of nutrients were stored in these organs, but when evaluated by concentration, large biomass is a diluting factor that can lead to lower concentrations of elements in these organs
Summary
Nutrient levels among different organs of desert shrubs[11,12], and the mechanism of element status in desert shrubs remains elusive. The goal of the present study was to fill the knowledge gap concerning variations in element concentrations among different organs in desert plants Toward this goal, we conducted an extensive field campaign in which 24 dominant shrub species were sampled from 52 sites across a temperate desert of northwestern China. With the collection of this comprehensive dataset, we aimed to test the following four hypotheses In this water and nutrient co-limited environment, we hypothesize that element concentrations of desert shrubs are higher in leaves than in stems and roots. We hypothesize that the scaling of element concentrations between the photosynthetic organ (leaf) and non-photosynthetic organs (stem and root) are allometric In this regional study with relative narrow geographic scale, we hypothesize that soil and taxonomic factors explain most elemental variation among desert shrubs compared to climatic factors
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