Mercedes Casal

Influence of heat and smoke treatments on the germination of six leguminous shrubby species

The effect of high temperatures and smoke on germination was tested on the shrubland Leguminosae species, Adenocarpus lainzii, Cytisus scoparius, Cytisus striatus, Genista berberidea, Genista triacanthos, and Pterospartum tridentatum, which are abundant and widely distributed throughout the north-western Iberian Peninsula. Light thermal shocks (80°C, 5 min and 80°C, 10 min) and medium thermal shocks (110°C, 5 min and 110°C, 10 min) stimulated seed germination in C. striatus, A. lainzii, and P. tridentatum. The treatments 80°C, 10 min and 110°C, 5 min stimulated germination in C. scoparius but only 110°C, 5 min did so in G. berberidea and G. triacanthos. The intense thermal shocks (150°C, 5 min and 150°C, 10 min) inhibited germination in all of the species studied but the inhibition effect was already detectable at 110°C, 10 min in G. berberidea. From the results, it was impossible to relate the different levels of smoke used to the variations in the germination response of the species studied. The increase in the germination level after fire was more important in C. scoparius, C. striatus, A. lainzii, and G. triacanthos, which are non-resprouters.

Resprouting Ability of Six Atlantic Shrub Species

Resprouting from subterranean structures is a principal method of vegetative regeneration that many shrub species show after a disturbance. This study, therefore, aims to determine the resprouting capacity and intensity of six dominant species in an Atlantic shrubland area located in the NW of the Iberian Peninsula and compare their resprouting and germinating strategies. Resprouting intensity is measured using three variables: individual probability of resprouting, number of resprouts and length of these sprouts in three plant-age classes. The intensity for each species was calculated using a simple index (IRI) that included the three measured variables. All studied species, excepting Erica umbellata, could resprout. According to the IRI values, there are three groups of species: strong resprouters (Ulex europaeus, Ulex minor and Pterospartum tridentatum), weak resprouters (Ulex micranthus and Genista triacanthos) and non-resprouters (E. umbellata). The germination of strong resprouters is highly stimulated by fire. Frequent disturbances remove the non- and weak resprouter populations and promote the strong resprouter ones.

Conservation of Erica ciliaris and Erica tetralix Communities: The Role of Land Management and Physical Environment on the Composition, Species Richness and Presence of Endemic Taxa

In spite of their great ecological, economic and social importance, wetlands of all the continents present common problems of insularity, increased by fragmentation due to human action. Between the types of wetlands, some of the more widespread are the wet heathlands that, in the case of Europe, are dominated by Erica ciliaris and Erica tetralix. In this paper, we analysed the species composition of Erica ciliaris and Erica tetralix communities and their relationship to the patch area, as well as the effect of different environmental factors and management. We obtained data of altitude, water-logging degree, area and perimeter, and management type of 30 different sites. Species distribution and species abundance were calculated and the endemic and protected species were identified. We found that the species richness of these communities is related to the distance to the nearest patch and not related to its total area or shape and neither were the number and abundance of the specialist and generalist species, which could be due to the “extinction debt”. We also found that the species composition is influenced by both the degree of water-logging and the management of the site, as cutting prevents these communities from advancing to the woodland stage. These two parameters are therefore of great importance for the conservation of wet heathlands.

Understanding biological characteristics of Acacia melanoxylon in relation to fire to implement control measurements

Key messageAcacia melanoxylonproduces abundant seeds leading to large seed banks in the soil. These seeds display a large viability and their germination is stimulated by heat. To control the populations, it is necessary to remove adults and young individuals, and to prevent seedling establishment after fire occupying the space with rapid growth and high competitive native species.ContextAcacia melanoxylon displays a widespread distribution in South West Europe, and an improved knowledge of its reproductive characteristics is required in order to control its expansion.AimsThis experiment was designed to provide useful indicators for an efficient management of A. melanoxylon populations based on its biological cycle in relation to fire.MethodsWe explored the reproductive biology of A. melanoxylon, from seed dissemination—–quantifying seed rain over a year, their germination with and without fire—the seedling and sapling banks and the structure of the adult population. We analysed the effects of fire, seed maturation and scarification on the viability of seeds and the stimulation of seed germination in the aerial seed bank and in the different strata of the soil seed bank.ResultsOur results indicate that A. melanoxylon produced millions of seeds per ha and per year, half of which germinated and the other half went to the soil seed bank, maintaining the viability many years. The germination was the most critical step in the population dynamics of this species, and fire stimulates germination up to 90%.ConclusionA. melanoxylon adults and seedlings removal, followed by colonization of rapid growth and high competitive native species that cover the ground very quickly would be a good control action.

Can the mother plant age of Acacia melanoxylon (Leguminosae) modulate the germinative response to fire

Acacia melanoxylon R.Br. (Leguminosae) is one of the most widely distributed tree species in the world. It has significant commercial use but can be a danger to natural ecosystems as an invader species. For these reasons it is necessary to have a deep knowledge about its germinative response to fire and the role the mother plant age plays in that response. In this work we assessed the effects of the interaction of the mother plant age with the main fire agents (smoke, charcoal, ash and heat) on the germinative response of A. melanoxylon. To reach this aim, germination tests were conducted with seeds from young, intermediate and mature mother plants, with 20 treatments each applied. Results show that fire can act as a great stimulator of the germination of A. melanoxylon but it can also strongly inhibit it. The mother plant age does not modify the final germination values, but it influences the time in which the first germinations occur after fire. This trait can be more important than the final germination percentage when looking at the success of post-fire regeneration. These results have important implications for A. melanoxylon management, for both species control and ecological restoration purposes.