Growth and morphology of three forest understorey species (Calluna vulgaris, Molinia caerulea and Pteridium aquilinum) according to light availability

Noémie Gaudio (1) , Philippe Balandier (1) , Yann Dumas (1) , Christian Ginisty (1)

1 UR EFNO - Écosystèmes forestiers

Calluna vulgaris, Molinia caerulea and Pteridium aquilinum are three forest understorey species that compete with tree seedlings for environmental resources. Forest managers therefore seek to control their growth, which is driven in part by the light available in the forest understorey. An experiment was set up in a nursery in which the three understorey species C. vulgaris, M. caerulea and P. aquilinum were planted at six light levels (6, 11, 22, 36, 48 and 100% of full sunlight) replicated in three blocks. The different light levels other than 100% were obtained using neutral shading nets. The response of the three species to light availability was estimated after two growing seasons by their cover and height, their morphology, assessed by the foliar tuft height-to-width ratio for C. vulgaris and M. caerulea and by the frond height-to-length ratio for P. aquilinum, and their functional acclimation, assessed by a leaf trait (leaf mass on an area basis, LMA). Vegetation cover changed with light availability following a bell-shaped curve. By contrast, vegetation height remained approximately the same, irrespective of the light treatment, except for P. aquilinum, which grew higher than the other two species at medium and high light levels. As a consequence, vegetation individuals were more spindly in a dark environment. From the lowest light treatment, P. aquilinum cover was high (75%) and intercepted a larger proportion of the light than the other two species. This species thus proved the most competitive for light. All three species showed a notable acclimation to light availability by their LMA, though in different ways. The LMA of C. vulgaris decreased in shaded conditions by an increase in leaf area, whereas decrease in LMA for P. aquilinum was due to a decrease in leaf mass. For M. caerulea, the LMA remained stable whatever the light conditions by a simultaneous increase in both leaf mass and leaf area in shaded conditions. Consequently, the in-forest development of C. vulgaris and M. caerulea could be managed through small adult canopy thinnings, as both species grew well from light levels above 20%. Conversely, it seems unrealistic to manage P. aquilinum in this way as its development was almost maximal even at very low light levels.

Mots clés: PTERIDIUM AQUILINUM; CALLUNA VULGARIS; MOLINIA CAERULEA; COMPETITION BIOLOGIQUE; CONCURRENCE VEGETALE; FORET; PEUPLEMENT FORESTIER; STADE DE DEVELOPPEMENT VEGETAL; DYNAMIQUE DE VEGETATION; VEGETATION; SOUS BOIS; LUMIERE; DISPONIBILITE EN LUMIERE; RAYONNEMENT LUMINEUX; SYLVICULTURE; OUVERTURE DU PAYSAGE; MORPHOLOGIE; COUVERT FORESTIER; CROISSANCE EN HAUTEUR; REGENERATION NATURELLE; TROUEE; ARBRE; CROISSANCE; CALLUNE; FOUGERE; MOLINIE; COUVERTURE

Domaines: Sciences de l'environnement; Ecologie, Environnement

Noémie Gaudio, Philippe Balandier, Yann Dumas, Christian Ginisty. Growth and morphology of three forest understorey species (Calluna vulgaris, Molinia caerulea and Pteridium aquilinum) according to light availability. Forest Ecology and Management, 2011, 261 (3), p. 489 - p. 498. ⟨10.1016/j.foreco.2010.10.034⟩. ⟨hal-00590768⟩