Canopy Development and Leaf Nitrogen Distribution in a Stand of Carex Acutiformis

Abstract

Seasonal changes in leaf nitrogen distribution were examined in the canopy of a Carex acutiformis stand in a wet meadow area. Although there was a tendency for leaf nitrogen concentration to decrease with increasing leafage in any one layer of the canopy, nitrogen concentration increased significantly with plant height despite increasing age of leaf portions higher in the canopy. This suggests a predominant effect of the light climate on the nitrogen distribution within the canopy. During the growing period, standing crop dry mass increased significantly, while the increase in the standing crop of nitrogen was marginal. The amount of nitrogen decreased in the lower layers and increased in the upper layers, and a strongly decreasing gradient of nitrogen concentration developed from the top to the bottom of the canopy. It is suggested that this gradient resulted mainly from leaf tips with high nitrogen concentrations being lifted to higher positions because of growth at the base, with some retranslocation of nitrogen downwards from senescing tips to active par!s. The distribution of nitrogen concentration became less uniform during the growing penod, thus supporting the prediction that nitrogen concentration should become less uniformly distributed with development of the canopy ..

Relating tree growth to rainfall in Bolivian rain forests: a test for six species using tree ring analysis

“…Later in the rainy season ring growth is much less (Worbes 1999). This may be due to decreasing photosynthetic capacities of older leaves (Mooney et al 1981;Hirose et al 1989;Ackerly and Bazzaz 1995;Miyaji et al 1997) or to a shift from growth to storage (Iwasa and Cohen 1989). These factors, or a combination of these factors, most probably explain why early rainfall is so important for tree growth that year.…”

Development of the Monsi-Saeki Theory on Canopy Structure and Function

“…As new leaves are produced at top of the plant, which is exposed to full irradiance, and as young leaves are usually high in protein content, leaf age was suggested to control the allocation program (Field, 1983;Field and Mooney, 1983), although the effect of ageing was different in extent between species native to closed habitats and those native to open canopy habitats (Mooney et al, 1981). Hirose et al (1989) studied nitrogen distribution in a stand of a monocotyledonous species, Carex acutiformis. As this species is a rosette plant having a meristem at the base of the plant, the youngest portion of a leaf blade is always subject to the lowest irradiance within the canopy.…”

Shoot structure, light interception, and distribution of nitrogen in an Abies amabilis canopy

“…Given this, it can be shown that resource use is optimized when the distribution of nitrogen within the canopy is directly proportional to the distribution of intercepted PAR, when both are expressed on an area basis (e.g., Farquhar 1989). Many plant canopies have now been studied from this perspective (Field 1983, Hirose et al 1989, Hollinger 1989, Ellsworth and Reich 1993, Evans 1993, Kull and Niinemets 1993, and in nearly all cases, it has been found that nitrogen per unit leaf area varies in parallel with light availability, although it rarely decreases sharply enough to remain proportional to light at lower levels of the canopy. However, these theories do not specify the physiological or morphological mechanism by which an optimal distribution is obtained, and structural variations above the level of the leaf have rarely been considered.…”