Plant density

It is most easily interpreted in the case of monospecific stands, where all plants belong to the same species and have germinated at the same time.

Due to competition for light, nutrients and water, individual plants will not be able to take up all resources that are required for optimal growth.

A key factor in agronomy and forestry is plant population density, which provides an experimental approach for better understanding plant-plant competition.

This is what has been dubbed 'constant final yield',[5] and refers to the total plant biomass per unit ground area.

At such high densities, these plants will start to compete soon after germination, and eventually a large number of those individuals (up to 95%) will die.

The higher the Leaf Area Index, the higher the fraction of intercepted sunlight will be, but the gain in light interception and photosynthesis will not match the increase in LAI, and this is the reason that total biomass per ground area saturates at high plant densities.

Leaves of high-density plants are thinner (higher SLA – leaf area per unit mass), especially lower in the vegetation, with a similar concentration of nitrogen per unit mass, but a lower nitrogen content per area.

Effect of plant density on (a) total shoot mass and (b) seed mass per unit ground area. Schematised figure, inspired a.o. by experiments with maize by Li et al. (2015).
Effect of a low (L), intermediate (I) and high (H) plant density on Maize.
Leaf size of the largest full-grown leaf of Maize plants grown at a low (L), intermediate (I), and high (H) plant density.