14:30 〜 14:45
[AGE27-04] Nitrogen Cycle: From tree to forests, Combining fieldwork and UAV images to assess forest Nitrogen dynamics
★Invited Papers
The Nitrogen cycle at the tree level in different types of forests in Yamagata Prefecture offer a base for understanding the pattern of movement of N, depending on the tree species, soil type, forest structure, environment and topographical conditions. Studies of N cycle are usually done at tree level because of constraints in sampling and analyzing capacity and in many cases because of the difficult access to some areas. N in forests is usually evaluated by the analysis of N content and stable N isotope (d15N) of plant tissues (foliage, stem and roots). The results of using this methodology, at the ‘plot’ level are usually scaled up to forest level but usually the forest that is being scaled up is not well known. This could lead to wrong interpretations of N dynamics in forest or regional level. Nitrogen, together with Phosphorus, is an incredibly dynamic nutrient with large variability during the tree's growing season. This variability is usually measured in terms of Nitrogen Resorption Efficiency (NRE) or in terms of isotope fractionation, representing the quantity and quality of the N being translocated from one tissue to another or being released as litter back into the soil. This is a new approach that is not properly tested and can probably be useful for a better interpretation of the usually highly meticulous tissue level measurements.