According to an Ecosystems study published by SpringerLink, researchers measuring a 4.1-million-year chronosequence of tropical montane soils found that canopy nutrient pools and fluxes correlate with fine root mass. The work revealed an inverse trade-off between light-use efficiency and nutrient-use efficiency across varying nitrogen and phosphorus availability.
Plants adjust to changing nutrient availability by altering carbon allocation patterns and nutrient-use efficiency, though they face a distinct physiological trade-off. According to a study published by SpringerLink, researchers investigated how montane Metrosideros polymorpha
forests respond across a 4.1 x 106-year space-for-time substitution chronosequence where available soil nitrogen and phosphorus pools shift with site age.
Soil Chronosequence and Net Primary Production in Tropical Montane Forests
The study measured net primary production, nutrient-use efficiency, and light-use efficiency across sites with broad ranges of nitrogen and phosphorus availability. Despite these wide variations in nutrient supplies, SpringerLink reported little difference in net primary production between the sites.
Researchers also found no consistent relationships in how production was allocated to leaves, fine roots, or wood, running contrary to traditional theories of carbon allocation relative to limiting resources. However, canopy nutrient pools and fluxes tracked closely with the mass of fine roots per unit soil volume, alongside a weak but positive correlation between net primary production and leaf area index.
Contrasting Patterns of Light-Use and Nutrient-Use Efficiency
Patterns of light-use efficiency and nutrient-use efficiency across the soil developmental sequence moved in opposite directions, according to the SpringerLink findings. Light-use efficiency increased as nutrient availability and nutrient turnover accelerated.
Conversely, nutrient-use efficiency decreased in response to those same environmental influences. Nutrient-use efficiency reached its peak values at sites where either nitrogen or phosphorus availability—and the turnover of both elements—remained low.
Evidence for Physiological Trade-Offs in Metrosideros polymorpha Canopies
The data demonstrated a negative correlation between light-use efficiency and nutrient-use efficiency. SpringerLink noted that this inverse relationship supports the hypothesis that a direct trade-off exists between light-use efficiency and the specific leaf characteristics that govern nutrient-use efficiency in these tropical montane ecosystems.
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