Shoot structure, canopy openness, and light interception in Norway spruce

Abstract

We analysed changes in shoot structure with canopy openness in control (C) and irrigated–fertilized (IL) Picea abies trees. Canopy openness, which was used to characterize light availability, varied between 0·23 and 0·90 for C shoots and 0·07 to 0·75 for IL shoots. Needle width and thickness increased with canopy openness, but were similar for C and IL needles. The ratio of needle thickness to width remained fairly close to one throughout the canopy. This resulted in large values (3·0–4·0) of the ratio of total to projected needle area. The ratio of total to projected needle area did not correlate with canopy openness. Shoot silhouette to total needle area ratio (STAR) and specific needle area decreased with canopy openness. As a result, shoot silhouette area per unit needle mass was up to three times larger in shade shoots than in sun shoots. STAR and specific needle area were similar for C and IL shoots and needles. Needle nitrogen concentration varied between 0·7 and 1·1% (C), and between 1·0 and 1·6% (IL). On both plots, nitrogen content was linearly related to estimated relative light interceptance (RLI) (both expressed per needle area), but the ratio of nitrogen content to RLI increased with decreasing canopy openness.

Influence of light and competition on crown and shoot morphological parameters of Norway spruce and silver fir saplings

“…These results, while confirming previous observations on the same species [6,24,25,31], indicate no major difference in the plasticity of response to light -at the crown, shoot and needle level -between Norway spruce and silver fir saplings.…”

“…However, the relationships between light and growth or morphological parameters are far to be fully understood. Other than to be species-specific, for a certain species these relationships may vary among climatic regions [34] and may be greatly affected by the interaction with other factors 270 G. Grassi, R. Giannini such nutrient availability, sapling size and competition [8,10,16,25,[31][32][33]. This complexity becomes especially relevant in uneven-aged managed forests, where the high structural fragmentation of the canopy and the clustering pattern of natural regeneration [15] lead to a high spatial variability of light in the understory and of competition between saplings.…”

A method to account for shoot scale clumping in coniferous canopy reflectance models

“…3). The observed tight relationship between p sh and STAR is convenient because data on STAR are available for many coniferous species (Cescatti & Zorer, 2003;Palmroth, Stenberg, Smolander, Voipio, & Smolander, 2002;Stenberg, Kangas, Smolander, & Linder, 1999;Stenberg et al, 2001;Stenberg, Smolander, Sprugel, & Smolander, 1998). The within-shoot hot spot effect was visible as a peak in the backscattering direction in the shoot scattering phase function (Fig.…”

Does the azimuth orientation of Norway spruce (Picea abies/L./Karst.) branches within sunlit crown part influence the heterogeneity of biochemical, structural and spectral characteristics of needles?

“…Greater clumping of needles (number of needles per unit shoot length) was observed by Niinemets and Kull (1995) with increasing irradiance and height of Norway spruce crowns. Sunlit shoots of Norway spruce typically have higher needle area per unit shoot length than shaded shoots, and the orientation of needles around the shoot axis is more uniform in contrast to shaded shoots where needles are arranged in a laminar fashion (Stenberg et al, 1999). In addition to needle differentiation caused by vertical irradiance gradient in the tree crown, in coniferous species with greater needle retention, increasing age of needles is another important factor which influences foliar properties (e.g.…”