Juan Bautista Gallego Fernández

Vegetation dynamics of Mediterranean shrublands in former cultural landscape at Grazalema Mountains, South Spain

Plant community dynamics in Mediterranean basin ecosystems are mainly driven by an alternation of episodes of human intervention and land abandonment. As a result, a mosaic of plant communities has evolved following different stages of degradation and regeneration. Some authors has relate secondary succession to abandoned culture lands and regeneration to natural systems with abandonment of livestock or forestry exploitation. In this paper, the dynamics of shrublands in mid-mountain areas in the South of Spain after disturbance and land abandonment has been studied. The plant cover and 13 environmental variables of 137 selected sites on the Grazalema mountains was analysed to determine the vegetation pattern in relation to environmental factors and the succession types, either regenerative or secondary succession. The results show that today the Grazalema mountains have a heterogeneous vegetation pattern. Besides physical factors such as altitude or soil , human disturbance has modulated current vegetation patterns and dynamics. Two main types of vegetation dynamics can be distinguished in the study area. In areas affected by cutting, regeneration results in rich and dense shrub land, with resprouters as dominant species. In areas affected by recurrent wildfires or agriculture, secondary succession became dominant, resulting in less diverse shrubland, due to the dominance of seeders and decrease in resprouter species richness and cover.Plant community dynamics in Mediterranean basin ecosystems are mainly driven by an alternation of episodes of human intervention and land abandonment. As a result, a mosaic of plant communities has evolved following different stages of degradation and regeneration. Some authors has relate secondary succession to abandoned culture lands and regeneration to natural systems with abandonment of livestock or forestry exploitation. In this paper, the dynamics of shrublands in mid-mountain areas in the South of Spain after disturbance and land abandonment has been studied. The plant cover and 13 environmental variables of 137 selected sites on the Grazalema mountains was analysed to determine the vegetation pattern in relation to environmental factors and the succession types, either regenerative or secondary succession. The results show that today the Grazalema mountains have a heterogeneous vegetation pattern. Besides physical factors such as altitude or soil , human disturbance has modulated current vegetation patterns and dynamics. Two main types of vegetation dynamics can be distinguished in the study area. In areas affected by cutting, regeneration results in rich and dense shrub land, with resprouters as dominant species. In areas affected by recurrent wildfires or agriculture, secondary succession became dominant, resulting in less diverse shrubland, due to the dominance of seeders and decrease in resprouter species richness and cover.

Effects on soil, microclimate and vegetation of the native-invasive Retama monosperma (L.) in coastal dunes

The aim of this study was to analyse and quantify the effects of the canopy of the native-invasive N-fixer woody shrub Retama monosperma in the dune ecosystem, affecting the structure and function of the dune environment as well as plant community, in the context of the facilitation mechanism. Air temperature and relative humidity; soil pH, electric conductivity, organic matter (OM) and nutrient content; above and below-ground vegetation biomass, litter mass, species richness and Shannon diversity were determined and compared from sampling plots below the R. monosperma canopy and in canopy gaps within a coastal dune system in SW Spain. The relationships between soil OM and nutrient contents and above and below-ground vegetation biomass, litter mass, species richness and Shannon diversity were also assessed. A predominance of positive interactions was confirmed. The canopy of R. monosperma ameliorated temperature extremes beneath, and soil OM and nutrient concentrations were increased by 188–466%, compared to those found in gaps. Plant biomass increased by 442% beneath the canopy and was composed almost exclusively of herbaceous annuals. Plant diversity was not affected. Plant communities were clearly structured as fertility islands, distributed in an environmentally stressful dune matrix characterized by scarce vegetation cover and low biomass.

Rabbits (Oryctolagus cuniculus) as dispersers of Retama monosperma seeds in a coastal dune system

Abstract The role of wild rabbit in Retama monosperma seed dispersal was studied in a sand dune spit in coastal Lepe County, Huelva, Spain. Of 8301 randomly collected rabbit pellets, 2.4% contained R. monosperma seeds. The percentage of pellets containing seeds was significantly higher in summer and autumn. Germination of seeds from pellets (24%) was significantly higher than that of seeds extracted from fruits (13%). The R. monosperma seed shadow extended to all dune ridges surveyed in the active colonization zone; rabbit pellets with R. monosperma seeds were found in dune ridges not yet colonized by R. monosperma shrubs. Rabbit dispersal activities are one of the main causes of R. monosperma spread along El Rompido spit.

Dune Vulnerability in Relation to Tourism Pressure in Central Gulf of Cádiz (SW Spain), a Case study

Abstract The severe modification and progressive loss of coastal dunes in the last decades has resulted in calls from conservationists to assess the conservation status and condition of these systems, and thus several vunerability indices have been developed. The vulnerability status of two protected coastal dune systems in the central Gulf of Cádiz (SW Iberian Peninsula) was assessed at local scale and results compared with a previous assessment to regional scale. A vulnerability index (VI) based on variables that desribed geomorphological condition, marine influence, aeolian influence, vegetation condition, and human effects was calculated to previously defined 17 homogeneous coastal segments, and the main factors affecting them were identified. Higher vulnerability was related to two differentiated situations: segments with low or negative sedimentary budget and segments subjected to considerable human pressure. Vulnerability status of the studied stretches was also analyzed in relation to tourism pressure and level of accessibility. Vulnerability was directly related to some characteristics of the accesses as well as to visitor pressure, showing higher vulnerability those segments with increased accessibility and influx of visitors. Obtained results were more detailed in comparison with previous assessment to regional scale, and were easily translated to specific management actions. These actions should be mainly focused on controlling and limiting human (tourism) influence, particularly in those segments affected by these factors.

The Biological Flora of Coastal Dunes and Wetlands: Retama monosperma (L.) Boiss.

ABSTRACT Muñoz Vallés, S.; Gallego Fernández, J.B., and Cambrollé, J. 2013. The biological flora of coastal dunes and wetlands: Retama monosperma (L.) Boiss. Retama monosperma (L.) Boiss. (white bridal broom) is a legume shrub that establishes mainly on coastal sands and dunes in zones under a Mediterranean climate. The species is able to tolerate salt spray, high temperatures of substrate and air, and low levels of soil nutrients and humidity. It is important in middle stages of dune succession, functioning as a key species in structuring the plant community, and it can play an important role in geomorphology. Retama monosperma enriches soil with N and other nutrients, ameliorates the typical harsh environmental conditions in dunes for other plants, and provides refuge and food for wildlife and forage for livestock. Leaves fall rapidly after emergence, and gas exchange is carried out in photosynthetic stems (cladodes), thereby reducing salt-induced stress. Some compounds isolated from the species show potential in pharmacological applications. It has high fruit production and effective associated seed dispersers. Recently, it has been reported that R. monosperma displays invasive behaviour in coastal areas in different parts of the world, including within its natural range, showing potential to negatively affect singular and protected coastal dune flora. Here we present a summary of the biology of R. monosperma. RESUMEN Retama monosperma (L.) Boiss. (Retama blanca, retama de olor) es un arbusto leguminoso que se establece principalmente en arenales y dunas costeras en zonas con clima mediterráneo. Está adaptada a las condiciones estresantes típicas de este medio, tales como la incidencia de espray salino, elevadas temperaturas del aire y el suelo y escasez de agua y nutrientes. La especie es importante en estadíos intermedios de sucesión en dunas costeras, donde funciona como especie clave en la estructura de la comunidad vegetal, y cumple un importante papel en la geomorfología dunar. Retama monosperma es capaz de enriquecer el suelo con N y otros nutrientes y atenuar las duras condiciones ambientales, facilitando la supervivencia de otras plantas bajo su dosel, así como proporciona refugio y alimento para cierta fauna silvestre y para el ganado doméstico. Pierde las hojas rápidamente tras la emergencia y la fotosíntesis se lleva a cabo en tallos fotosintéticos, lo que reduce el estrés inducido por la deposición de sal. Algunos compuestos aislados de sus tejidos muestran propiedades con aplicación farmacológica. Posee una elevada producción de frutos y dispersores efectivos asociados. Recientemente se ha puesto de manifiesto el comportamiento invasivo que muestra la especie en áreas costeras en diferentes partes del globo, incluyendo su área de distribución natural, afectando en ocasiones a especies singulares y protegidas de la flora dunar costera de forma negativa. En el presente trabajo presentamos un resumen de la biología de R. monosperma.