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

Abstract

-The effects of a natural gradient of light and competition on crown, shoot and needle morphology of naturally regenerated Norway spruce (Picea abies) and silver fir (Abies alba) saplings, 0.8-0.2 m tall, were analyzed in a uneven-aged, managed stand in Comelico (eastern Italian Alps). The results indicate that: (i) both crown, shoot and needle morphology are strongly affected by light, but in the examined conditions (relative irradiance ranging from 2 to 32%) no significant effect of competition was observed, (ii) the ecological differences between Norway spruce and silver fir saplings cannot be mainly attributable to differences in crown morphological traits, and (iii) the apical dominance ratio (i.e., the length of the apical leader divided by the mean length of the lateral shoots at the last node) is a relatively good and simple indicator of the light conditions in which saplings are growing. These informations may be useful in order to promote and assure effectively natural regeneration. . Les résultats obtenus montrent que : (i) couronne, pousse et morphologie des aiguilles sont fortement affectées par la lumière, mais dans les conditions étudiées (éclairement relatif variant de 2 à 32 %) il n'a pas été observé d'effet significatif de la compétition ; (ii) les différences écologiques entre les plants d'épicéa et de sapin pectiné ne peuvent pas être attribuées principalement à des différences dans les caractéristiques morphologiques de la couronne ; (iii) le ratio de dominance apicale (i.e., longueur de la pousse terminale de la flèche divisée par la longueur moyenne des pousses latérales du dernier verticille) est relativement un bon et simple index des conditions de lumière dans lesquelles poussent les plans. Cette information peut être utile pour promouvoir et assurer efficacement une régénération naturelle. lumière / compétition / croissance / morphologie de la couronne / morphologie de la pousse

Successful under-planting of red oak and black cherry in early-successional deciduous shelterwoods of North America

“…Others found similar results, namely the predominant effect of competition produced by the overstory canopy on that of the lower vegetation layer [1,11,15,48]. Grassi and Giannini [19] found strong growth and morphological relations with available light (canopy induced), but none with competing sapling's density. For Brandeis et al [8] and Spetich et al [49], growth increased with a decrease in the density of the shelterwood stand and of the understory competition.…”

Shoot development and dieback in progenies of Nothofagus obliqua

“…Trees may respond to different environmental conditions through morphological and/or physiological mechanisms [5,12]. The knowledge of genetic components involved in these responses is useful especially in the case of valuable forestry tree species.…”

Apical dominance ratio as an indicator of the growth conditions favouring Abies alba natural regeneration under Mediterranean environment

“…In literature, some studies report a strong correlation between the apical dominance ratio (ADR, ratio between apical shoot length and length of first whorl lateral twigs) and relative irradiance in naturally recruited silver fir seedlings (Bagnaresi et al 1989;Nolè et al 2003;Robakowski et al 2004;Grassi and Giannini 2005). Apical dominance, in fact, is the control exerted by the apical portions of the shoot over the outgrowth of the lateral buds (Cline 1991).…”