Patterns of nitrogen resorption efficiency among different functional groups of trees in a subtropical forest of Meghalaya

Abstract

Nutrient resorption (NR) from senescing leaves plays an important role in the conservation of nutrients in plants. The nutrient resorption efficiency depends on several factors including availability of soil nutrients, species type and leaf nutrient quality. Although several researchers have worked on the pattern of NR in deciduous and evergreen plants, it varied widely. Since the variations are species-specific and many functional groups prevailing in tropical and subtropical forests have not been studied, the understanding of NR pattern in varied functional groups remained incomplete. In this study, Nitrogen resorption efficiency (NRE) of four tree species belonging to different functional groups viz., Alnus nepalensis (non-leguminous nitrogen-fixing and deciduous), Lithocarpus dealbatus (broadleaved and evergreen), Pinus kesiya (coniferous and evergreen) and Schima wallichii (broadleaved semi-evergreen) were studied. NRE was greatest in Alnus nepalensis and Schima wallichii immediately before the maximum leaf fall and it decreased in the subsequent months. However, NRE in Lithocarpus dealbatus exhibited identical values across all the months in a year. In Pinus kesiya, the NRE was the lowest and it varied through six months. The nitrogen concentration in the leaves and NRE varied significantly among the species and across the months. The trees belonging to certain functional groups did not differ in their NREs in different months of a year due to the availability of alternate strategies to acquire nitrogen or being semi-/ evergreen in nature to cope up with their nutrient loss.