Plastic changes of leaf mass per area and leaf nitrogen content in response to canopy openings in saplings of eight deciduous broad‐leaved tree species

Leaf nitrogen content per area (N area ) is a good indicator of assimilative capacity of leaves of deciduous broad‐leaved trees. This study examined the degrees of increase in N area in response to canopy openings as leaf mass per area (LMA) and leaf nitrogen content per mass (N mass ) in saplings of eight deciduous broad‐leaved tree species in Hokkaido, northern Japan. Five of the species were well‐branched species with a large number of small leaves (lateral‐growth type), and the other three species were less‐branched species with a small number of large leaves (vertical‐growth type). The degrees of increase in N area were compared between the two crown types. In closed‐canopy conditions, leaves of the vertical‐growth species tended to have a lower LMA and higher N mass than those of the lateral‐growth species, which resulted in similar N area for both. LMA increased in canopy openings in the eight species, and the degrees of increase were not largely different between the lateral‐ and vertical‐growth species. On the contrary, N mass was unchanged in canopy openings in the eight species. As a result, N area of each species increased in canopy openings in proportion to the increase in LMA, and the degrees of increase in N area were similar in the lateral‐ and vertical‐growth species. Therefore, this study showed that the degrees of increase in N area were not correlated with the crown architecture (i.e., the lateral‐ and vertical‐growth types).