A global trait‐based approach to estimate leaf nitrogen functional allocation from observations

Abstract

Nitrogen is one of the most important nutrients for plant growth and a major constituent of proteins that regulate photosynthetic and respiratory processes. However, a comprehensive global analysis of nitrogen allocation in leaves for major processes with respect to different plant functional types (PFTs) is currently lacking. This study integrated observations from global databases with photosynthesis and respiration models to determine plant-functional-type-specific allocation patterns of leaf nitrogen for photosynthesis (Rubisco, electron transport, light absorption) and respiration (growth and maintenance), and by difference from observed total leaf nitrogen, an unexplained "residual" nitrogen pool. Based on our analysis, crops partition the largest fraction of nitrogen to photosynthesis (57%) and respiration (5%) followed by herbaceous plants (44% and 4%). Tropical broadleaf evergreen trees partition the least to photosynthesis (25%) and respiration (2%) followed by needle-leaved evergreen trees (28% and 3%). In trees (especially needle-leaved evergreen and tropical broadleaf evergreen trees) a large fraction (70% and 73%, respectively) of nitrogen was not explained by photosynthetic or respiratory functions. Compared to crops and herbaceous plants, this large residual pool is hypothesized to emerge from larger investments in cell wall proteins, lipids, amino acids, nucleic acid, CO fixation proteins (other than Rubisco), secondary compounds, and other proteins. Our estimates are different from previous studies due to differences in methodology and assumptions used in deriving nitrogen allocation estimates. Unlike previous studies, we integrate and infer nitrogen allocation estimates across multiple PFTs, and report substantial differences in nitrogen allocation across different PFTs. The resulting pattern of nitrogen allocation provides insights on mechanisms that operate at a cellular scale within leaves, and can be integrated with ecosystem models to derive emergent properties of ecosystem productivity at local, regional, and global scales.

Global patterns of intraspecific leaf trait responses to elevation

“…The N area , N mass and P mass are traits representing the amount of proteins and nucleic acids stored in the leaf that can be invested for photosynthesis and growth (Ghimire et al., ; Onoda et al., ). In concordance with the previous meta‐analysis of Read et al.…”

Improving Estimates of Gross Primary Productivity by Assimilating Solar‐Induced Fluorescence Satellite Retrievals in a Terrestrial Biosphere Model Using a Process‐Based SIF Model

“…This should enable to better represent the covariations of V cmax and leaf chlorophyll content, and hence the impact of C ab on the SIF signal. Indeed, leaf chlorophyll content is related to leaf nitrogen content (Gholizadeh et al, ; Yoder & Pettigrew‐Crosby, ) with a dependence that may however vary depending on the season, species, and allocation of nitrogen for different plant processes (Croft et al, ; Ghimire et al, ; Kalacska et al, ). In parallel, a more direct relationship between C ab and V cmax shall be implemented to represent the dynamic of leaf chlorophyll content (Croft et al, ; Houborg et al, ; Migliavacca et al, ).…”

Global leaf nitrogen and phosphorus stoichiometry and their scaling exponent

“…In contrast, the numerically smaller N-P scaling exponents observed for coniferous species relative to broad-leaved woody species might reflect leaf morphological and anatomical characteristics in addition to P-related growth rate. The specific leaf area of conifers is generally smaller than that of broad-leaved species [43,44], which may result in relatively lower nutrient demands, especially for N (Table 1) [6]. In addition, coniferous species are mostly distributed in cold habitats that may require the storage of lipid P in thick and narrow leaves for cold resistance [45].…”

“…Nitrogen (N) and phosphorus (P), especially the N in Rubisco that drives photosynthesis and the P in ribosomal RNA that drives the generation and maintenance of proteins, are essential nutrients [3][4][5][6] that are consequently tightly linked and important parameters in stoichiometric growth models [7][8][9]. Therefore, the leaf N and P stoichiometric patterns including N and P concentrations and N:P ratios are largely explored both at regional and global levels [10][11][12][13], which are important bridges linking elemental compositions or allocations with organismal metabolic processes, and even energy flow in the whole ecosystem [9].…”