Fernando Ojeda

Resprouting as a key functional trait: how buds, protection and resources drive persistence after fire

Resprouting as a response to disturbance is now widely recognized as a key functional trait among woody plants and as the basis for the persistence niche. However, the underlying mechanisms that define resprouting responses to disturbance are poorly conceptualized. Resprouting ability is constrained by the interaction of the disturbance regime that depletes the buds and resources needed to fund resprouting, and the environment that drives growth and resource allocation. We develop a buds-protection-resources (BPR) framework for understanding resprouting in fire-prone ecosystems, based on bud bank location, bud protection, and how buds are resourced. Using this framework we go beyond earlier emphases on basal resprouting and highlight the importance of apical, epicormic and below-ground resprouting to the persistence niche. The BPR framework provides insights into: resprouting typologies that include both fire resisters (i.e. survive fire but do not resprout) and fire resprouters; the methods by which buds escape fire effects, such as thick bark; and the predictability of community assembly of resprouting types in relation to site productivity, disturbance regime and competition. Furthermore, predicting the consequences of global change is enhanced by the BPR framework because it potentially forecasts the retention or loss of above-ground biomass.

Fire‐related traits for plant species of the Mediterranean Basin

Plant trait information is essential for understanding plant evolution, vegetation dynamics, and vegetation responses to disturbance and management. Furthermore, in Mediterranean ecosystems, changes in fire regime may be more relevant than direct changes in climatic conditions, making the knowledge of fire-related traits especially important. Thus the purpose of this data set was to compile the most updated and comprehensive information on fire-related traits for vascular plant species of the Mediterranean Basin, that is, traits related to plant persistence and regeneration after fire. Data were collected from an extensive literature review and from field and experimental observations. The data source is documented for each value. Since life history traits may vary spatially or with environmental conditions, we did not aggregate them by species; i.e., traits and species are repeated in different records if they were observed by different researchers and/or in different locations. Life history traits inclu...

Plant diversity patterns in the Aljibe Mountains (S. Spain): a comprehensive account

The Aljibe Mountains are located in the southern tip of the Iberian Peninsula and have a remarkable biogeographical interest. The complete plant species list (trees, climbers, shrubs, perennial and annual herbs, ferns, lichens, bryophytes and macroscopic algae) was recorded in four 0.1 ha plots from each of the most representative community types (Quercus suber woodland, Q. canariensis forest, open heathland and Q. coccifera shrubland). Up to 119 plant species were found in total in the Q. suber woodland plot. The diversity of woody plants was analysed from 44 samples of cover (100 m line), and the herbaceous layer was explored in 200 quadrats (of 0.5 × 0.5 m). Three biodiversity components (species richness, endemism, and taxonomic singularity) were evaluated in both shrub and herbaceous layers. Open heathlands showed the highest richness of endemic species, both woody and herbaceous. The highest number of woody species was found in the evergreen Q. suber woodland, and of herbaceous species in the semi-deciduous Q. canariensis woodland. Taxonomic singularity was higher in Q. canariensis woodlands and Q. coccifera shrublands for woody species, but there were no significant differences in the herbaceous layer. Local species diversity of heathlands in this region resembles that of South African heathlands (fynbos), despite the obvious geographic and floristic distance, and contrasts with the low diversity of biogeographically closer, European temperate heathlands. The Aljibe Mountains show high diversity values for different life forms (from trees to mosses) and spatial scales (from community to region), and are rich in endemic species. Thus, this area should be recognised as a relevant unit within the Mediterranean plant diversity hot spots.

Root starch storage and allocation patterns in seeder and resprouter seedlings of two Cape Erica (Ericaceae) species

Post-fire sprouting of dormant buds in resprouter plants is facilitated by stored carbohydrate reserves, with starch being the critical reserve. Starch is mainly stored in xylem parenchyma ray tissue of woody underground organs, such as burls, lignotubers, and roots. We carried out a comparative analysis of the pattern of starch storage and the proportion of parenchymatic ray tissue in the upper root or cotyledonary region of seedlings from seeder and resprouter forms within two Cape Erica (Ericaceae) species: E. coccinea L. and E. calycina L., which were raised in the greenhouse under controlled irrigation. We also explored the root-to-shoot allocation patterns of seeder and resprouter seedlings in these two species. Resprouter seedlings of both species showed higher relative amounts of upper-root starch and upper-root storage tissue as well as a higher root-to-shoot allocation than their seeder counterparts. Pronounced swelling of the upper root region suggests ontogenetic development of a lignotuber in the resprouter forms of the two Erica species. The distinct allocation of starch in roots seems to be genetically determined and would account for the apparent differences in the root-to-shoot allocation patterns between both regeneration forms from the early seedling stage.

Postfire regeneration of a mediterranean heathland in southern Spain

Fire is a recurrent disturbance in the vegetation of Mediterranean climate regions. Most of the woody species (16 out of 19) in a Mediterranean heathland community, in the Strait of Gibraltar region of southern Spain, sprouted from subterranean vegetative organs after a wild-fire. Dominant sprouters were the prostrated oak Quercus lusitanica, three gorses, Genista tridens, G. tridentata and Stauracanthus boivinii, and a heath, Erica scoparia. About 100 seedlings m-2 of 14 woody species were censused in the first three years after fire. The highest density of seedlings was recorded for heather (Calluna vulgaris), a rockrose (Cistus populifolius subsp. major) and a gorse (Genista triacanthos). Woody vegetation covered up to 85% of the soil surface in the third year after fire. At this stager the community was co-dominated by the sprouters Quercus lusitanica (21%), Genista tridentata (21%) and Stauracanthus boivinii (20%), and the seeder Cistus populifolius subsp. major (20%). A total of 52 herbaceous species, many of them (35) perennials, was recorded, showing a temporal change in species composition. The role of fire influencing community diversity and the consequences for the conservation of heathlands in the Strait of Gibraltar region, are discussed.

Biodiversity components and conservation of mediterranean healthlands in Southern Spain

Abstract Biodiversity is a complex issue which has frequently been extremely simplified both by equating it with species richness, and by addressing it at the level of regional floras or faunas. In this paper we carry out a detailed assessment of biodiversity for conservation of Mediterranean heathlands and related woodland understoreys on acidic ‘islands’ in the Gibraltar Strait region which are remarkable for their high species richness, high endemism and low ratio of species per genus. The relationship between the cover of woody plant species and environmental variables was studied by multivariate (DCCA) analysis of 30 samples. Species richness shows a unimodal relationship along the main environmental gradient primarily determined by physiological tolerance to low pH and ecological competition. Quercus suber woodland understoreys under intermediate environmental conditions are highest in species richness. Woody plant species are assigned to one of seven types of geographic ranges, and distributional spectra of community samples are represented. Open heathlands on nutrient-poor soils on mountain ridges are highest in endemism. Species distinctness was estimated as the inverse of the average number of species per genus (‘taxonomic singularity’) within the Mediterranean Basin, Ibero-North African and Southwestern Spain ranges. Quercus canariensis woodland understoreys on more fertile soils on valley bottoms present the highest taxonomic singularity. The analysis at the community level of the three proposed biodiversity components (species richness, endemism richness and taxonomic singularity) is interpreted with the aim of formulating sound conservation strategies of the communities examined. Although we use communities in the Gibraltar Strait area as a particular case study, we suggest that this methodology would help conservation efforts in other areas.

Biodiversity of woody species in oak woodlands of southern Spain and northern Morocco

Abstract Three biodiversity parameters – species richness, endemic species richness and taxonomic singularity – have been evaluated for the woody understorey of oak woodlands on sandstone-derived substrates, on both sides of the Strait of Gibraltar. There is a similarity in floristic composition and ecological distribution of woody plant communities across the Strait. Nevertheless, we have detected significant differences. These include a general reduction in species richness, number of endemic species and taxonomic singularity (at the community level), and a greater abundance of widespread, generalist species, on the southern side (Moroccan) communities, as compared to the north (Spanish ones). We interpret these differences as partly caused by the contrasting management of woodlands, with higher slashing and browsing pressure in Morocco.

Patterns of ecological, chorological and taxonomic diversity at both sides of the Strait of Gibraltar

Diversity relations in Mediterranean heathlands and the understorey of oak woodlands on sandstone-derived substrates were studied at both sides of the Strait of Gibraltar. Trends in species composition and cover were analysed by Detrended Correspondence Analysis; the first axis, assumed to reflect a main environmental gradient, was used to analyse the patterns of three aspects of community diversity. Species richness, i.e. number of species along a 100-m transect, shows a humpbacked trend along the gradient, with the highest values in the understorey of evergreen Quercus suber wood- lands, associated with soils of intermediate fertility and mois- ture status. The number of endemic species is highest in open heathlands, associated with more extreme conditions of acid, infertile soils on exposed ridges. The taxonomic singularity, as measured by the inverse of the average number of species per genus at each site, is highest at the most fertile and moist sites occupied by semideciduous Q. canariensis woodlands. A comparison between northern (Spanish) and southern (Moroccan) sides of the Strait of Gibraltar shows a general concordance of the trends of woody plant communities along the main environmental gradient. However, significant differ- ences of the southern samples are: (1) lack of some differen- tial, habitat-specific species and greater abundance of wide- spread generalists; and (2) a general reduction in species diversity, number of endemics and taxonomic singularity. We interpret these differences as affected partly by the smaller extent and fragmentation of sandstone areas in the south, and partly by the higher impact of slashing and grazing there.

Effects of afforestation with pines on woody plant diversity of Mediterranean heathlands in southern Spain

Open heathlands of the Strait of Gibraltar region constitute a singularvegetation type within the Mediterranean Basin owing to their high biodiversitylevels and distinct features in the biological aspects of endemism. However,they have been traditionally depicted as low profitable, tree-less, barrenlandsand have been either overlooked in conservation policies or included inextensive pine-tree afforestation programmes. Nowadays, most of the existingpine plantations are no longer exploited and have become dense pine woodlands.Here we present the results of a comparative analysis aimed to ascertain theeffects of pine stands on the structure and diversity of the woody component ofthese mediterranean heathlands. Ten sampling sites were located within thestudyarea, each consisting of two adjacent subsamples: an open heathland and aneighbouring heathland under pine-tree cover. Woody species richness andoverallshrub cover was much lower in pine-tree heath understoreys. This drop in coverwas more marked for short-lived species (seeders and withering resprouters),implying a decrease of the life-history diversity and also having noticeableconsequences in homogenizing the floristic composition of heath patches underpine trees. Heathland narrow endemics dropped significantly in pine stands,showing greater sensitivity to afforestation than nonendemics. We suggest thatthe open heathlands of the Strait of Gibraltar should be given furtherattentionin EU and IUCN conservation policies. Programmes should be implemented toprogressively eliminate abandoned pine plantations so as to restore andpreservethese highly diverse mediterranean heathlands.

Soil shapes community structure through fire.

Recurrent wildfires constitute a major selecting force in shaping the structure of plant communities. At the regional scale, fire favours phenotypic and phylogenetic clustering in Mediterranean woody plant communities. Nevertheless, the incidence of fire within a fire-prone region may present strong variations at the local, landscape scale. This study tests the prediction that woody communities on acid, nutrient-poor soils should exhibit more pronounced phenotypic and phylogenetic clustering patterns than woody communities on fertile soils, as a consequence of their higher flammability and, hence, presumably higher propensity to recurrent fire. Results confirm the predictions and show that habitat filtering driven by fire may be detected even in local communities from an already fire-filtered regional flora. They also provide a new perspective from which to consider a preponderant role of fire as a key evolutionary force in acid, infertile Mediterranean heathlands.