Experiment Title: Effect of nutrient availability on plant scale carbon costs to acquire nitrogen as it relates to carbon gain and water loss. Institutions responsible:

Utrecht University (Jan Lankhorst)
Experiment Description: This experiment tests the effect of nutrient availability on plant scale carbon costs to acquire nitrogen in relation to the optimal tradeoff between carbon gain and water loss at leaf level. Both in a controlled setting with nutrients added to sand, and in natural soils with known quantities of available nitrogen and phosphorus. An additional sterilization of natural soils has been performed to disentangle the microbial influences from the (direct) nutrient availability.
Variables being tested: Experimental Details (factorial design, replication, lab/field/ controls, vegetation type): Data availability: Study limitations:
  • Whole plant carbon & nitrogen acquisition (roots, shoots, stems, dry weight & measured concentration)
  • Leaf level photosynthetic capacity (Vcmax, Jmax) and χ (δ13C).

Additional measures:

  • Natural soil bulk NH4+ NO3– soluble PO4–
  • Pilot for SOC measured from pore-water.
 Greenhouse experiment, with 2 species of plants endemic to the Netherlands (1 grass, 1 forb) .

Nutrients in sand:

17 pots per treatment per species

3 nutrient treatments based on the availability in natural soils (Low= 0.7x N available, Med = 1x N available, High = 2x N available

Natural soils:

10 pots per soiltype per treatment per species

1 soiltype equated to Med N treatment

1 soiltype to 2 x N available

Treatment = gamma ray sterilized, or non-sterilized. 

Data available for all measurements.

CSV/xlsx files.

Not published yet so on request

 Pot size was limited to 3 litres.

Plants were grown in low-light availability.

In absolute values the N availability is low compared to other N addition experiments.

Soil sterilization changed more than only microbiome, organic N became inorganic N, leading to more available N for direct uptake and clouding the microbiome effect.