Erica Australis Research Articles

Plant stored reserves do not drive resprouting of the lignotuberous shrub Erica australis.

• Lignotuberous plants store carbohydrates and mineral nutrients within the lignotuber. Resprouting vigour may depend on stored reserves, as well as on the availability of soil mineral nutrients and water. • Here the role played by plant reserves and soil resources on the resprouting response of Erica australis was analysed after clipping plants in 13 different stands, varying in soil resource availability and in plant reserves. • There were significant among-site differences for resprout biomass and maximum length, but not for resprout number, 1 yr after clipping. Plant reserves at the time of clipping were not significantly correlated with resprout number, length or biomass. However, resprouting variables were significantly correlated with soil nitrogen or extractable cations, or plant water potentials. Resprout biomass and maximum length were negatively correlated with lignotuber size. • These findings indicate that the assumption that resprouting vigor in lignotuberous plants is primarily dependent on the amount of reserves stored in the lignotuber must be revised, as well as the overall role of lignotubers in resprouting.

Variability in seed germination at the interpopulation, intrapopulation and intraindividual levels of the shrub Erica australis in response to fire-related cues

In Mediterranean ecosystems, as well as in other fire prone ones, seedling establishment by some species is particularly favorable right after fire. It has been well established that many plants from these ecosystems have enhanced germination after exposing their seeds to heat or to chemicals related to the passage of fire. Less known it is how variable is this germination response among seeds from different sources (populations, individuals within a population, or parts of the plant within an individual) and whether such differences persist after exposing the seeds to germination-triggering, fire-related cues. In this work we studied the germination response to several fire-related factors of the Mediterranean, lignotuberous shrub Erica australis. This species produces a very combustible fuel, and resprouts vigorously after fire, but conditions for seedling establishment are poorly known. The objective of this study was to evaluate how variable was the germination response of this species among seeds from different sources, and whether this variability changed after exposing the seeds to fire-related factors. Seeds from three different sites, from different individuals at each site, and from different branches within each individual were set to germinate under control conditions or after exposing them to heat or to additions of nitrogenous compounds. Germination was highly variable among populations, individuals within populations or branches within individuals. Exposure to moderate heat promoted germination, but high temperatures were lethal. Differences at the various provenance levels were, however, also observed after heat exposure. Germination of seeds exposed to nitrogenous compounds increased, but differences among populations were always significant. These results indicate that the germination of Erica australis may be linked to disturbances, but it does not seem to be particularly related to passage of fire. On the contrary, this type of response appears more common in plants from heterogeneously disturbed environments.

Secondary succession after perturbations in a shrubland community

Shrubland responses to experimental burning, cutting and ploughing treatments were studied over 15 years in two shrubland communities dominated by Erica australis . The treatments represent the most frequent forms of anthropogenic disturbances experienced by these communities throughout their history. The response to burning and cutting treatments is similar, and the succession process is characterised as autosuccession. The highest values for herbaceous annuals and perennials were observed in the third and fourth years. Generally, herbaceous species remain present throughout the study period, while woody taxa ones increase their cover values over time. The quantity of herbaceous species present is in inverse proportion to the quantity of woody taxa. The woody species that appear immediately after treatments are sprouting species, namely Erica australis and Arctostaphylos uva-ursi . The response to ploughing is slower, reflecting the recovery mechanism (seedlings). However, after 15 years, there are no significant differences in regeneration between treatments. The first stages of this post-ploughing succession are dominated by annual species until the fourth or fifth years, after which woody species begin to dominate and herbaceous taxa decrease considerably. Woody species with high germination values are Halimium alyssoides and Halimium umbellatum . These shrubland communities have a very high resilience to such perturbations and start regenerating rapidly, reaching the original state in about 9 years. The appearance of the climax arboreal species of the area, Quercus pyrenaica , when it comes from germination, occurs 15 years after the perturbations.

Resprouting in the Mediterranean‐type shrub Erica australis afffected by soil resource availability

Abstract. Soil resource availability may affect plant regeneration by resprouting in disturbed environments directly, by affecting plant growth rates, or indirectly by determining allocation to storage in the resprouting organs. Allocation to storage may be higher in stressful, low resource‐supply soils, but under such conditions plant growth rates may be lower. These factors could act in opposite directions leading to poorly known effects on resprouting. This paper analyses the role played by soil resources in the production and growth of resprouts after removal of above‐ground plant tissues in the Mediterranean shrub Erica australis. At 13 sites, differing in substrate, we cut the base of the stems of six plants of E. australis and allowed them to resprout and grow for two years. Soils were chemically analysed and plant water potential measured during the summer at all sites to characterize soil resource availability. We used stepwise regression analysis to determine the relationships between the resprouting response [mean site values of the number of resprouts (RN), maximum length (RML) and biomass (RB)] and soil nutrient content and plant water potential at each site. During the first two years of resprouting there were statistically significant differences among sites in the variables characterizing the resprouting response. RML was always different among sites and had little relationship with lignotuber area. RN was less different among sites and was always positively correlated with lignotuber area. RB was different among sites after the two years of growth. During the first months of resprouting, RN and RML were highly and positively related to the water status of the plant during summer. At later dates soil fertility variables came into play, explaining significant amounts of variance of the resprouting variables. Soil extractable cations content was the main variable accounting for RML and RB. Our results indicate that resprout growth of E. australis is positively affected by high water availability at the beginning of the resprouting response and negatively so by high soil extractable cation content at later periods. Some of these factors had previously shown to be related, with an opposite sign, to the development of a relatively larger lignotuber. Indeed, RML and RB measured in the second year of resprouting were significantly and negatively correlated with some indices of biomass allocation to the lignotuber at each site. This indicates that sites favouring allocation to the resprouting organ may not favour resprout growth.

The dynamics of mediterranean shrubs species over 12 years following perturbations

The response of woody species to experimental burning, cutting andploughing was studied for a period of twelve years in a shrub community in NWSpain. The treatments represent the perturbations most frequently imposed bymanon these shrub communities throughout history. The response to burning is muchfaster than the response to cutting. The response to ploughing is slower due tothe regeneration mechanism that species use: germination. In general, thedominant species, Erica australis, influences theregeneration patterns of the rest of the species, which make up the community.There is a significant increase in the cover of woody species until the fourthyear, and of herbaceous species until the third year. Subsequently,Erica australis attains dominance, returning to itsoriginal spatial occupancy and cover values, removing the herbaceous speciesandnegatively influencing the growth of woody ones like Halimiumumbellatum, Halimium alyssoides and Quercuspyrenaica. Both Erica australis andChamaespartium tridentatum regenerated by sprouting in theburnt and cut plots, and by germination in the ploughed plot.Arctostaphylos uva-ursi only recovers after burning andploughing. Halimium alyssoides, Halimium umbellatum, Ericaumbellata and Calluna vulgaris regenerate bygermination in the three plots. Differences in cover values and spatialoccupancy during the first years of succession tend to be eliminated twelveyears after treatment and most of the species tend to recover their initialcover values. These shrubland communities have a high degree of resilience dueto the strong sprouting potential of the component species.

The effects of thermal scarification and seed storage on germination of four heathland species

The germination responses of 4 shrubs, Erica arborea, E. australis and Daboecia cantabrica (Ericaceae) and Genistella tridentata (Papilloneaceae) in relation to variable light and temperature regimes was determined for freshly harvested and 1 year-old seeds. Temperature treatments consisted of 5 levels of heat from 60 °C to 140 °C and two levels of exposure time, 2 and 4 min. We also examined the effects of stratification on germination of Erica arborea and E. australis. The seeds of Erica arborea were the first to begin germinating and the freshly collected ones reached the highest level of germination with light. The seed viability of E. arborea was affected by storage, decreasing germinative capacity, while mean germination in Erica australis ssp. aragonensis was lowest. However, the stored E. australis seeds germinated better than the fresh ones. Germination response to ageing varies in Daboecia cantabrica depending on heat pretreatment. A significantly positive effect of high temperature and exposure time on germination was shown in Daboecia cantabrica and Genistella tridentata. Cold pre-treatment of seeds did not enhance germination.

Resprouting in the Mediterranean-type shrub Erica australis afffected by soil resource availability

Abstract Soil resource availability may affect plant regeneration by resprouting in disturbed environments directly, by affecting plant growth rates, or indirectly by determining allocation to storage in the resprouting organs. Allocation to storage may be higher in stressful, low resource-supply soils, but under such conditions plant growth rates may be lower. These factors could act in opposite directions leading to poorly known effects on resprouting. This paper analyses the role played by soil resources in the production and growth of resprouts after removal of above-ground plant tissues in the Mediterranean shrub Erica australis. At 13 sites, differing in substrate, we cut the base of the stems of six plants of E. australis and allowed them to resprout and grow for two years. Soils were chemically analysed and plant water potential measured during the summer at all sites to characterize soil resource availability. We used stepwise regression analysis to determine the relationships between the resprou...

Seasonal course of total non-structural carbohydrates in the lignotuberous Mediterranean-type shrub Erica australis

Lignotuberous plants are frequently dominant in Mediterranean-type shrublands, and total non-structural carbohydrates (TNC) stored in the lignotuber are assumed to play an important role in resprouting after fire. However, seasonal variations in TNC in this organ and other plant parts have not been properly evaluated, particularly in relation to periods of fire risk, during which lignotuber TNC concentrations should be highest. We document the seasonal course of TNC concentrations in the stems, lignotubers and roots of 13 populations of the Mediterranean-type, lignotuberous, resprouter shrub Erica australis from central Spain. Plant water potentials were measured in parallel to correlate seasonal variations in water availability with fluctuations in TNC concentrations. Mean TNC concentrations in stems, lignotubers and roots throughout the year were 55, 73 and 120mg g(-1) dry weight, respectively. Roots contained highest TNC concentrations, which were maximal in late spring. Starch concentrations decreased in all plant parts during spring, when plants were actively growing and reproducing. Lignotuber TNC concentrations were lowest in early summer, and remained relatively low during the period of maximum fire risk. Monosaccharide concentrations increased significantly in all plant parts during the summer, coinciding with a reduction in plant water potential. We conclude that seasonal fluctuations of TNC in E. australis are related to periods of plant growth and reproduction, and also occur in response to stressful conditions. No evidence was obtained supporting the idea that seasonal fluctuations of TNC may be a response to ensure highest TNC content in the lignotuber during periods with maximum fire risk.

The seed bank in <i>Pinus</i> stand regeneration in NW Spain after wildfire

Abstract. In the Cantabrian area (northwest Spain) Pinus stands occupy many of the original shrub communities that have been considered unproductive. These Pinus stands represent the vegetation which is most affected by fire. Regeneration after fire may occur in different ways: by resprouting or by germination or both. Germination was the only regeneration mechanism in Pinus species that appeared in these areas. The aim of this study is to determine the role of the soil seed bank in regeneration in this type of ecosystem. In order to carry out the study, three communities dominated by Pinus sylvestris which had suffered wildfires were chosen. In each of the three experimental sites of Pinus sylvestris stands the seed bank composition and above-ground vegetation were studied. The results allowed three species groups in the seed bank to be differentiated: those favoured by fire, amongst which some hardseeds, mainly belonging to Cistaceae and Leguminosae, were found; another group formed by outsider or opportunist species from outside the community and which used anemochory as their main dispersion mechanism; and the third group formed by those negatively affected, amongst which were species using vegetative resprout as the main regeneration mechanism. The species of greatest quantitative importance in the seed bank was Erica australis. In general, anemochorous species were predominant in the soil seed bank. During the first stages of succession chamaephytes were dominant and in the two years after fire therophytes were. No great similarity was observed between the bank composition and field vegetation from a qualitative viewpoint, due to differences in the presence of seeds of outsider plants in the bank and to the significance of the resprouting species in the field.

No allocation trade-offs between flowering and sproutingin the lignotuberous, Mediterranean shrub

Trade-offs between allocation to sexual or vegetative regeneration capacity are well established as a driving force in the life history patterns of plants in fire-prone environments. However, it is not known whether such trade-offs exist in plants which after aboveground removing disturbances, such as fire, may regenerate by sexual (seeding) or asexual (sprouting) mechanisms. We evaluated whether in the fire-recruiting resprouter Erica australis, which after fire can regenerate by seedling establishment or resprouting, a larger investment in flowers and seeds prior to being disturbed by clipping its aboveground parts would decrease subsequent sprouting, that is, its vegetative regeneration capacity. We analysed the relationships between flower and seed production and the ensuing production and growth of sprouts of six plants from thirteen different sites in central-western Spain. We found no significant relationships between measures of sexual reproductive effort and resprout production and growth 6 months after clipping the aboveground parts of the plants. No evidence of trade-offs between sexual and asexual efforts was found. Furthermore, no significant relationship was found between lignotuber total non-structural carbohydrates and sexual reproductive effort. In addition, 2 years after the disturbance, resprout biomass was positively and significantly correlated with sexual reproductive effort prior to the disturbance. This indicates that growth of resprouts was higher at the sites where plants made a greater reproductive effort. The sites that were more favourable to producing flowers and seeds could also be more favourable to resprouting.

Lignotuber size of Erica australis and its relationship with soil resources

Abstract. It has been proposed that resprouting after a disturbance would be favoured under conditions of low soil resource availability. In lignotuberous plants of Mediterranean‐type areas, successful resprouting after disturbances such as fire depends on the size of the lignotuber, but little is known about the role of soil resources in determining the relative size of this organ. In this work we tested whether the relative size of the lignotuber in the resprouting shrub Erica australis is related to the availability of soil resources. At each of 13 different sites in Spain, 10 plants were chosen and the sizes of their various parts (above‐ and below‐ground) measured. Additionally, at each site we evaluated soil fertility, foliar N and P concentrations and plant water potential in the middle of the summer. The relationships between lignotuber dimensions and the various plant parts were assessed. In all cases, significant differences between sites were found indicating consistent differences in lignotuber size across the range of plant sizes. This was particularly the case when lignotuber dimensions were expressed as a function of foliar biomass. Lignotuber dimensions relative to foliar biomass were positively correlated with soil pH and negatively with plant water potentials in midsummer. There were, however, no clear relationships between lignotuber relative dimensions and soil N and P contents or other measures of site productivity. In summary, lignotubers were not smaller at more productive sites, in fact they were relatively larger at sites where soils were less acidic, but where plant water conditions were less favourable. These findings contradict predictions made based on current theory on the role of soil fertility allocation to resprouting.

Quince años de sucesión después de corta experimental en brezales de <i>Erica australis</i> L. en la provincia de León (España)

The response of the woody species to experimental cutting was studied for a period of fifteen years in a shrub community of NW Spain. This treatment represents the disturbance most frequently imposed by humans on these shrub communities throughout history. The dominant species, Erica australis , influences the regeneration patterns of the rest of the species which make up the community. There is a significant increase in the cover values of the woody species until the fourth year and of the herbaceous ones until the third year. Since then Erica australis attains the spatial occupancy and cover values it originally had, removing the herbaceous species and negatively influencing the growth of some woody ones like Halimium umbellatum and H. alyssoides . Both Erica australis and Genistella tridentata sprout after cutting. Arctostaphylos uva-ursi does not recover. Halimium alyssoides, H. umbellatum. Erica umbellata and Calluna vulgaris regenerate by germination. These shrubland communities have a high degree of resilience due to the strong sprouting potential of the component species.

Seed banks of Erica australis and Calluna vulgaris in a heathland subjected to experimental fire

Abstract. Soil samples were collected before and after an experimental fire on a heathland in the province of León (Spain). The seed banks were assessed by counting the numbers of seedlings appearing of Erica australis and Calluna vulgaris. A total of 2285 germinable seeds/m2 before burning and 1177 germinable seeds/m2 after the fire were estimated for Erica australis, and 90 and 690 germinable seeds/m2, respectively, for Calluna vulgaris. After the fire the number of germinable seeds/m2 of Erica australis had decreased, whilst there was a considerable increase in the number of germinable seeds/m2 of Calluna vulgaris. Neither seedlings nor sprouts of Calluna vulgaris had appeared in the field plots 10 months after the fire. Erica australis did recover mainly by sprouting after fire.

Ecological distribution of four co‐occurring Mediterranean heath species

Erica australis, E. scoparia, E. arborea and Calluna vulgaris are the most abundant heath species on acid, sandstone‐derived soils of the Strait of Gibraltar region (southern Spain and northern Morocco). Despite their apparently similar ecological requirements, these four species are somewhat ecologically segregated. Erica australis is abundant only on poor, shallow soils, with a high content in soluble aluminium, generally on mountain ridges and summits. Erica scoparia becomes dominant on deeper sandstone soils with lower aluminium. Calluna vulgaris coexists with these Erica species in communities under low or no tree cover. In the Spanish side of the Strait (Algeciras), Erica arborea tends to be relegated to communities under moderate to dense tree cover, whereas this species is more abundant and widespread in the Moroccan side (Tangier). Tolerance to extreme physical conditions ‐ high aluminium and dense tree cover ‐ and interspecific competition seem to explain the ecological distribution of these four heath species in the Strait of Gibraltar region. The more fragmented pattern of sandstone patches and higher disturbance levels in Tangier might account for the differences in the patterns of ecological distribution of these four heath species between both sides of the Strait of Gibraltar.

Species cover and composition of mesomediterranean siliceous soils shrubs, in which bulldocer scalping plus full subsoiling reforestation preparatory practices has been done in «el Andévalo», Huelva province, Spain

Has been studied the influence of the laboured, bulldocer scalping plus full subsoiling, in the presence of characteristic species of the mesomediterranean siliceous soils shrubs of “the Andévalo” in Huelva. The study is set in the Council “Cabezas Rubias”, province of Huelva, on a Pinus pinea reforestation, eight years after the bulldocer scalping and subsoiling previous plantation labours, were done, the total shrub cover has been estimated and compared as the addiction of its specific covers in the situations: 1) Grown shrubs after the considered preparatory treatment; 2) Shrubs presence in close areas without reforestation, therefore without any preparatory practice for reforestation. From the statistical analysis, no relation was obtained in the total cover variable with the applied treatment, it can be concluded that the only species which reduces its presence (in a 65.56%) is Cistus ladanifer. The specific cover average representation increases in Erica australis (33.90%), Erica umbellata (84.01%) and in all the flora components from the “Other species” group, composed by Halimium ocymoides, Genista triacanthos and Lavandula stoechas. In this group, Genista triacanthos and Lavandula stoechas didn’t appeared in the testigo shrub, appearing with low representation after the reforestation labours studied.

Assessment of browsing biomass, nutritive value and carrying capacity of shrublands for red deer (Cervus elaphus L.) management in Monfragüe Natural Park (SW Spain)

Relationships between shrub browsing biomass (BB) and the morphological variables maximum height (H), relative height (RH), maximum diameter (D1) and minimum diameter (D2) were determined using stepwise multiple logarithmic regressions in shrublands composed of three dominant species, black heather (Erica australis L.), wild olive tree (Olea sylvestris Miller) and phillyrea (Phillyrea angustifolia L.), from the Monfragüe Natural Park in south-western Spain. Significant statistical analyses indicate that these models can be used for the determination of BB for the three dominant species. Analysis of the leaves of the three species were undertaken to determine the following nutritional parameters: minerals, ashes, neutral detergent fibre, acid detergent fibre, crude protein, crude fat and metabolizable energy. Results of BB together with the nutritional analysis, the acceptability of each species and the demand of metabolizable energy of deer were used in the determination of carrying capacity for three periods: maintenance (1·28 deer ha−1), lactation (0·78 deer ha−1) and gestation (0·99 deer ha−1). These results are only applicable to 22% of the Monfragüe Natural Park (south-western Spain) where these shrublands occur.

Space-time distribution patterns of shape Erica australis L. subsp. shape aragonensis (Willk) after experimental burning, cutting, and ploughing

The response of Erica australis to experimental burning, cutting and ploughing treatments was studied in two heathland communities where it was dominant. The treatments represent those most frequently originated by humans on these heathland communities throughout history. The response of this species in a community where it is dominant and there is no strong interspecific competition was also compared to that produced by it in a community where there is competition. It can be observed that the response to burning and cutting treatments is very similar with very fast spatial occupation in the first few years. From the point of view of time cover values increased in a pronounced manner during the first few years and this increase was stabilized from the fourth year. However, from this moment on a greater increase in this species' maximum height is evident. The response to ploughing is slower according to recovery mechanism (seedlings). Recovery is comparatively less in the area where there is no strong competition than in that where it exists between species. Resume Dans deux communautes de bruyere dominees par Erica australis on a etudie la reponse de cette espece aux traitements experimentaux de brulage, coupe et labour. Ces traitements representent les actions les plus frequentes que l'homme a exerce sur ces communautes de bruyere tout au long de l'histoire. De la meme facon, on a fait la comparaison de la reponse de cette espece quand elle se trouve dans une communaute dominee principalement par elle, ou elle n'y a pas une forte competition entre les especes, avec la reponse quand elle se situe dans une communaute ou plusieurs especes coexistent. On observe que la reponse aux traitements de brulage et coupe est tres semblable, en presentant une occupation spatiale tres rapide pendant les premieres annees. Du point de vue temporel, leurs valeurs de couverture augmentent de facon plus prononcee pendant les premieres annees, et c'est a partir de la quatrieme annee que ce developpement se stabilise. Cependant, c'est a partir de ce moment la qu'on remarque une augmentation plus grande en ce qui concerne la hauteur maximale de cette espece. La reponse au traitement de labour est plus lente en relation avec la regeneration par semences. L'effet de la competition se traduit par une recuperation qui suit un mode d'augmentation oppose a la situation originaire. Dans la surface ou il n'existe pas une forte competition, la recuperation est comparativement plus faible que dans la station ou il y existait une competition entre les especes. Mots cles: Maquis, Mecanismes reproductives, Perturbations experimentales, Regeneration, Rejets

Relaciones suelo-planta-herbívoro en un sistema pastoral de montaña

The soil characteristics of six communities with pastoral interest in Leon mountain (Spain) and the Ca, Cu, Fe, Mg, N, K and Na contents of soils and vegetation were analysed in relation with the nutritional characteristics of herbivores' diet. The communities were named after the most representative species: Nardus stricta, Bromus erectus. Genista florida. Erica australis. Genista occidentalis and Calluna vulgaris . Soils showed in general good conditions for vegetal growth. There were no relationships between soil and plants mineral contents. Ca and Cu were deficient in some moments during the stay of the animals in the mountain. Mineral concentrations in vegetation communities varied seasonally due to maturity processes and physiological changes in plants, depending on the kind of plant and the microenvironment where they grew.

First Phases of Regeneration of Cistus Laurifolius and Cistus Ladanifer After Burning and Cutting in Experimental Plots

The first phases of regeneration of two Cistus species (Cistus laurifolius and Cistus ladanfer) are compared in experimental plots that were subjected to different treatments: cutting and burning. In both treatments the parameters used were: seedling number, height and cover. Differences between their rowth are discussed and compared with that of Erica australis subsp. aragonensis, that can resprout vegetatively.

Heather‐feeding psyllids of the genus Strophingia (Homoptera)

AbstractMultivariate analysis of morphological characters suggests that the genus Strophingia comprises eight distinct species, namely ericae (Curtis) [the type‐species], australis sp.n., fallax Log., cinereae Hod., proxima sp.n., hispanica Hod. & Hollis, harteni sp.n., and arborea Log. Each species is fully characterized and an identification key is provided. A tentative phylogeny of the groups is proposed. Among the newly described species, australis (host plant: Erica australis) occurs in Portugal, proxima (host plant: Erica arborea and possibly Calluna vulgaris) is found throughout the Iberian peninsula, while harteni (host plant: Erica azorica) is found on the Azores.