Brachypodium Retusum Research Articles

Potential vegetation markers – analytical pyrolysis of modern plant species representative of Neolithic SE Spain

A selection of plant species that may have been relevant for the Neolithic in the SW Mediterranean have been characterised with pyrolysis gas chromatography mass spectrometry (pyrolysis–GC/MS) in search for molecular vegetation markers. Roots and aerial parts were analysed separately for the following species: Anthyllis cytisoides, Asphodelus cerasiferus, Brachypodium retusum, Cistus albidus, Cistus clusii, Dorycnium pentaphyllum, Ephedra fragilis, Juniperus oxycedrus, Juniperus phoenicea, Olea europaea, Phillyrea angustifolia, Pinus halepensis, Pistacia lentiscus, Quercus coccifera, Rhamnus lycioides, Rosmarinus officinalis, Smilax aspera and Stipa tenacissima; furthermore domesticated plants were analysed, including wheat (Triticum aestivum, Triticum dicoccum, Triticum monococcum, Triticum timopheevi and Triticum turgidum), barley (Hordeum vulgare and H. vulgare Hulled) and legumes (Lathyrus cicera, Lathyrus sativus, Lens culinaris, Pisum sativa, Vicia ervilia, Vicia faba and Vicia sativa). This resulted in 290 potential markers. In addition, the organic matter of surface soils under different vegetation cover has been analysed to test the presence of the potential markers in the soil. Forty-six of the potential markers were detected in the soil organic matter, of which part have not been reported before. The results may be useful for interpretation of the organic matter composition of soils and plant remains, which can be valuable in archaeology.

Caracterización de la ingestión por observación directa en rebaños ovinos del Sureste de Francia

When ruminants graze on heterogeneous vegetation, direct observation of bites is one of the most fitted method to estimate intake. Nevertheless its implementation in herds of more than 500 individuals has been scarce. In our study, this method was implemented to characterize the intake and know the feeding value offered by steppe vegetation. We observed two ovine flocks of 1100 and 1200 animals guided by shepherds in farm conditions. The animals used were Merinos dArles a breed with marked gregariousness. They constitute transhumant flocks that every spring graze the steppe vegetation of the Nature Reserve Coussouls de Crau located in Southeast France. The period of adaptation was brief lasting from 7 to 22 days. In this environment composed of a unique herbaceous layer, the intake rate was 5.9 ± 2.4 g DM/min, which is similar to levels reported in woody or shrubby rangelands. We found that in this steppe vegetation sheep are capable of flows up to 13 g DM/min. In previous studies the Brachypodium retusum has been considered of low nutritional value and little appreciated by the sheep. In our case it was found that the sheep eat a wide variety of plants. But when Brachypodium retusum contributes to the majority of dry matter intake, intake rate is significantly greater (6.8 g DM/min) than when this is contributed by forbs (4.4 g DM/min) or by the other grasses (5.8 g DM/min). This plant is revalued, our results showed that it allows sheep to make bites of mass higher than forbs and other grasses which explains its improved efficiency of collection. Direct observation allowed us to characterize the intake of sheep in Crau steppe and we consider this type of vegetation as a food source similar to woody or shrubby rangelands.

Host preferences of arbuscular mycorrhizal fungi colonizing annual herbaceous plant species in semiarid Mediterranean prairies.

In this study, we have analyzed and compared the diversities of the arbuscular mycorrhizal fungi (AMF) colonizing the roots of five annual herbaceous species (Hieracium vulgare, Stipa capensis, Anagallis arvensis, Carduus tenuiflorus, and Avena barbata) and a perennial herbaceous species (Brachypodium retusum). Our goal was to determine the differences in the communities of the AMF among these six plant species belonging to different families, using B. retusum as a reference. The AMF small-subunit rRNA genes (SSU) were subjected to nested PCR, cloning, sequencing, and phylogenetic analysis. Thirty-six AMF phylotypes, belonging to Glomus group A, Glomus group B, Diversispora, Paraglomus, and Ambispora, were identified. Five sequence groups identified in this study clustered to known glomalean species or isolates: group Glomus G27 to Glomus intraradices, group Glomus G19 to Glomus iranicum, group Glomus G10 to Glomus mosseae, group Glomus G1 to Glomus lamellosum/etunicatum/luteum, and group Ambispora 1 to Ambispora fennica. The six plant species studied hosted different AMF communities. A certain trend of AMF specificity was observed when grouping plant species by taxonomic families, highlighting the importance of protecting and even promoting the native annual vegetation in order to maintain the biodiversity and productivity of these extreme ecosystems.

Are old Mediterranean grasslands resilient to human disturbances?

Many dry herbaceous ecosystems suffer damage and are characterized by low resilience after disturbance. Among these forms of disturbance, soil excavation due to the construction of underground pipelines affects vegetation at plant community and landscape scales. Synchronic studies are the best approach for more rapid study of plant succession on ecosystems with low resilience. In order to better understand plant succession in a Mediterranean dry grassland, we compared the effect of a recent disturbance caused by the digging of a pipeline in 2006 with that of a pipeline created in 1972 in the same area. Surveys of floristic composition and richness were carried out along both pipelines in order to understand the succession after this single disturbance, one that does not drastically change soil chemical properties unlike former agricultural practices. Nevertheless, this type of disturbance still changes the floristic composition in the long term (>30 years). The first stage begins just after disturbance with the occurrence of many weed species. Another level between the first and the mature stage was characterized in our study, 30 years after the disturbance, by an assemblage of annual and perennial species but still lacking species typical of the reference steppe. The reference steppe is described as the mature level of the succession with an assemblage of typical grasses, forbs and a few small chamaephytes and, in particular, by the presence of Brachypodium retusum. This community corresponds to a very old Mediterranean grassland that has evolved under the Mediterranean climate and traditional sheep grazing management systems since the Neolithic Age. This study confirms the low resilience of this steppe community and shows the importance of pursuing research on this steppe and in particular on the biotic and abiotic processes involved in community assembly.

Hydrological heterogeneity in Mediterranean reclaimed slopes: runoff and sediment yield at the patch and slope scales along a gradient of overland flow

Abstract. Hydrological heterogeneity is recognized as a fundamental ecosystem attribute in drylands controlling the flux of water and energy through landscapes. Therefore, mosaics of runoff and sediment source patches and sinks are frequently identified in these dry environments. There is a remarkable scarcity of studies about hydrological spatial heterogeneity in restored slopes, where ecological succession and overland flow are interacting. We conducted field research to study the hydrological role of patches and slopes along an "overland flow gradient" (gradient of overland flow routing through the slopes caused by different amounts of run-on coming from upslope) in three reclaimed mining slopes of Mediterranean-continental climate. We found that runoff generation and routing in non-rilled slopes showed a pattern of source and sink areas of runoff. Such hydrological microenvironments were associated with seven vegetation patches (characterized by plant community types and cover). Two types of sink patches were identified: shrub Genista scorpius patches could be considered as "deep sinks", while patches where the graminoids Brachypodium retusum and Lolium perenne dominate were classified as "surface sinks" or "runoff splays". A variety of source patches were also identified spanning from "extreme sources" (Medicago sativa patches; equivalent to bare soil) to "poor sources" (areas scattered by dwarf-shrubs of Thymus vulgaris or herbaceous tussocks of Dactylis glomerata). Finally, we identified the volume of overland flow routing along the slope as a major controlling factor of "hydrological diversity" (heterogeneity of hydrological behaviours quantified as Shannon diversity index): when overland flow increases at the slope scale hydrological diversity diminishes.

Using a two‐phase sowing approach in restoration: sowing foundation species to restore, and subordinate species to evaluate restoration success

AbstractQuestionsIs it possible to restore a target herbaceous plant community on ex‐arable land by sowing foundation species? What is the impact of sheep grazing on the restoration of this ecosystem? How can we rapidly evaluate the success of restoration methods?LocationNature reserve of the plain of La Crau, southeast France (43° 31′ N, 4° 50′ E)MethodsIn an ex‐arable field, we sowed an indigenous species mix in 2007. This was composed of two perennial species dominant in the reference grassland ecosystem (Brachypodium retusum, Thymus vulgaris) and one annual species (Trifolium subterraneum) also found on the reference grassland and which is well‐known for its ability to quickly cover bare soil. These three species are called foundation species as they play an essential role in structuring the restored ecosystem community. To investigate the significances of the foundation species on community dynamics, four subordinate species were sown 1 yr later: Taeniatherum caput‐medusae, Linum strictum, Evax pygmaea and Asphodelus ayardii. The subordinate species are typical plants of the reference grassland which describe well this vegetation type.ResultsSowing foundation species was an effective means of reintroducing them. Their presence in the ex‐arable field very rapidly promoted establishment of grassland species and impeded establishment of weeds. When grazing was excluded, the foundation species covered the ground, particularly with Trifolium subterraneum, which reached 54% ground cover. Subordinate species established better on the foundation species sown treatment and on the grazed treatment.ConclusionIn the short term, sowing indigenous foundation species and maintaining grazing seems to be a good method to restore grassland plant communities that have a poor ability to re‐establish spontaneously. This study also demonstrates that sowing and monitoring of subordinate species is an effective method to rapidly test whether a particular restoration protocol will have a positive effect on community assembly and development.

Differences in the AMF diversity in soil and roots between two annual and perennial gramineous plants co-occurring in a Mediterranean, semiarid degraded area

Aims In the present study, we analysed the diversity of indigenous arbuscular mycorrhizal fungi (AMF) colonising both the roots and rhizosphere soil of an annual herbaceous species, Bromus rubens, and a perennial herbaceous species, Brachypodium retusum, co-occurring in the same Mediterranean, semiarid degraded area. The intention was to study whether these two species promoted the diversity of AM fungi in their rhizospheres differently and to ascertain whether the AMF community harboured by an annual plant species differed from that harboured by a perennial species when both grew in the same place.

Do endemic species always have a low competitive ability? A test for two Mediterranean plant species under controlled conditions

Aims Many observations concerning biological and ecological differentiation between narrow endemic and widespread congeneric plant species suggest that narrow endemic species are constrained to colonize marginal habitats because of a low tolerance to competition. Despite this topic being an important issue both for understanding evolutionary processes leading to endemism and for conservation purposes, few studies have been performed to compare competitive abilities between endemic and widespread species. Here, we present two independent experiments performed under controlled conditions using two different pairs of endemic and widespread congeneric species: Centaurea corymbosa/Centaurea maculosa and Arenaria provincialis/Arenaria serpyllifolia, both endemic species occurring in rocky calcareous habitats. Methods Mature seeds of C. corymbosa and C. maculosa were sown in pots containing ramets of the common grass, Brachypodium retusum. Pots were sorted in three treatments according to grass cover (low, intermediate and high). A control treatment (without competition) was also used. Germination, seedling survival and rosette growth were followed. For the comparisons between A. provincialis and A. serpyllifolia, seeds from natural populations were first sown without a competitor. One week after germination, healthy seedlings were transplanted in pots without Brachypodium seedling (control) or containing two Brachypodium seedlings (low competition) or four seedlings (high competition). We checked the number of capsules per individual, and we harvested the biomass after capsule maturation. Important Findings Despite differences in the protocol design, results are congruent, and in both cases, endemic species are highly affected by the presence of a competitor, as are the widespread species, although we did not detect any differences between species for response to competition. The results are discussed in relation to processes leading to endemism, suggesting that the specialist model is more likely for both the study species. The present study also contributes to guidelines for the conservation of rare species in relation to landscape modification in the Mediterranean area.

A resprouter herb reduces negative density-dependent effects among neighboring seeders after fire

Plant communities are often composed of species belonging to different functional groups, but relatively few studies to date have explicitly linked their spatial structure to the outcome of the interaction among them. We investigated if mortality of seeder species during their establishment after fire is influenced by the proximity of the resprouter herb Brachypodium retusum. The study was conducted in a Mediterranean shrubland (00°39′ W; 38°43′ N), 40 km northwest of Alicante (Spain) with Ulex parviflorus, Cistus albidus, Helianthemum marifolium, and Ononis fruticosa as dominant obligate seeder species and a herbaceous layer is dominated by the resprouter B. retusum. We followed the fate of mapped seedlings and the biomass of B. retusum one, two, three and nine years after an experimental fire. We used point pattern analyses to evaluate the spatial pattern of mortality of seeder species at these years in relation to the biomass of B. retusum. We hypothesize that B. retusum may initially have a positive impact on seeder survival. We implemented this hypothesis as a point process model that maintains the overall number of dead seeder plants, but seeder survival varied proportionally to the biomass of B. retusum in its neighborhood. We then contrasted this hypothesis with a previous analysis based on a random mortality hypothesis. Our data were consistent with the hypothesis that proximity of B. retusum reduced the mortality of seeder plants at their establishment phase (i.e., 2 yrs after fire). However, we found no evidence that B. retusum influenced seeder mortality when plants grow to maturity. We also found that, under the more stressful conditions (fire + erosion scenario), B. retusum had a lower impact on the performance of seeder species. Our results suggest that B. retusum may reduce negative density-dependent effects among neighboring seeder plants during the first years after fire.

Using a fire propagation model to assess the efficiency of prescribed burning in reducing the fire hazard

We examined how fire hazard was affected by prescribed burning and fuel recovery over the first six years following treatment. Eight common Mediterranean fuel complexes managed by means of prescribed burning in limestone Provence (South-Eastern France) were studied, illustrating forest and woodland, garrigue and grassland situations. The coupled atmosphere-wildfire behaviour model FIRETEC was used to simulate fire behaviour (ROS, intensity) in these complex vegetations. The temporal threshold related to the effectiveness of prescribed burning in reducing the fire hazard was assessed from derivated fuel dynamics after treatment. The study showed that prescribed burning treatment was effective for the first two years in most of the Mediterranean plant communities analysed. Thereafter, all forests and shrublands were highly combustible with a fire line intensity of more than 5000 kW/m except for pine stands with or without oak (medium intensity of 2000 kW m −1 3 years after treatment). Low fire line intensity (900 kW m −1) was obtained for grassland which was entirely treatment-independent since the resprouter hemicryptophyte, Brachypodium retusum, is highly resilient to fire. Fire behaviour was greatly affected by fuel load accumulation of Quercus ilex in woodland, and by standing necromass of Rosmarinus officinalis in treated garrigue. Pure pine stands with shrub strata similar to garrigue showed a lower fire intensity due to wind speed decrease at ground level under tree canopy, underlining the advantage of maintaining a proportion of canopy cover in strategic fuel-break zones.

Restoration of a Mediterranean Postfire Shrubland: Plant Functional Responses to Organic Soil Amendment

We investigated the potential of plant functional responses to speed up restoration in a postfire ecosystem. The patterns of change in plant nutrient uptake and water potential after compost amendment were monitored for 2 years in a 7‐year‐old postfire shrubland in southeastern France. We studied four different stress‐tolerant species with contrasting life traits: three shrub species and a perennial herb. Three treatments were applied: control, 50 and 100 Mg/ha of fresh cocomposted sewage sludge and green waste. In both compost treatments, concentrations of all the macronutrients increased. The amendment improved N and cation nutrition, but the positive effect of compost on plant nutrient status was most apparent on leaf P concentrations, indicating that P was a limiting nutrient in this shrubland. Compost had no significant short‐term effect on trace metal concentrations in plants. The plant nutrition response of different species to the compost varied; the nutritional status of Brachypodium retusum and Cistus albidus improved the most, whereas that of Quercus coccifera and Ulex parviflorus improved the least. Woody species exhibited no increase in N stocks. Phosphorus accumulation was also about three times higher in plots amended at 50 Mg/ha than in control plots for B. retusum and C. albidus. The severe summer drought of 2003 altered the compost effect. Contrary to our expectations, plants on amended plots did not exhibit a better water status in summer: the effect of the summer drought had a greater effect on water status than did the compost treatment.

Diversification of Pinus halepensis forests by sowing Quercus ilex and Quercus pubescens acorns: testing the effects of different vegetation and soil treatments

The goal of this study was to develop management strategies favouring establishment and survival of holm oak (Quercus ilex L.) and downy oak (Quercus pubescens Willd.)—two species co-occurring in Southern France—in mature Allepo pine forests (Pinus halepensis Mill subsp. halepensis). An experimental design was assessed in a partially cut mature stand of Aleppo pine in which five soil and vegetation treatments—chopping, chopping followed by scarification in one or two directions, prescribed burning, control—and two slash treatments (presence/absence) were applied. A total of 1,600 sowing points, each composed of 3 Q. ilex or Q. pubescens acorns, were installed in the different treatments in November of two consecutive years at 6 and 18 months, after the end of treatments. Survival was monitored 3 and 2 years after sowing, soil surface at the sowing points was characterized at different dates, and predawn leaf water potentials were measured during the dry season. High mortality occurred after the first summer, but survival after 1 year was 2.3–5.2 higher in Q. ilex than in Q. pubescens, confirming that Q. ilex was better adapted to the drier parts of the Mediterranean area. Survival was significantly influenced by the treatments, but there was a variable response between the two sowing years under most of the treatments. Only intense fire proved the most beneficial treatment for seedling survival in both years. The micro-local soil cover conditions induced by the treatments played a major role in explaining oak survival. In particular, grass cover (mainly Brachypodium retusum) proved to be largely unfavourable to seedling survival and growth, and this detrimental effect was also confirmed by lower predawn leaf water potential values with increasing grass cover. Acorn introduction designed to diversify mature Aleppo pine forest after soil and vegetation treatments therefore has to be considered for treatments that most efficiently impair the pre-existing competing grass cover such as prescribed high-intensity fire treatment.

Do vegetation patch spatial patterns disrupt the spatial organization of plant species?

The mechanisms that structure plant diversity and generate long-range correlated spatial patterns have important implications for the conservation of fragmented landscapes. The ability to disperse and persist influences a plant species’ capacity for spatial organization, which can play a critical role in structuring plant diversity in metacommunities. This study examined the spatial patterns of species diversity within a network of patches in Cabo de Gata Natural Park, southeastern Spain. The objectives were to understand how the spatial heterogeneity of species composition (beta diversity) varies in a structured landscape, and how the long-range spatial autocorrelation of plant species is affected by the spatial configuration of patches. The mechanisms underlying the spatial distribution of plants acted at two scales. Between patches, spatial variation in species distributions was greater than that expected based on spatial randomization, which indicated that movement among patches was restricted. Within patches, diffusion processes reduced spatial variability in species distributions, and the effect was more prominent in large patches. Small patch size negatively influenced the long-range spatial autocorrelation of characteristic species, whereas inter-patch distance had a stronger effect on species frequency than it had on the disruption of spatial organized patterns. The long-range spatial autocorrelation was evaluated based on the dispersal abilities of the species. Among the 106 species evaluated, 39% of the woody species, 17% of the forbs, and 12% of the grasses exhibited disrupted long-range spatial autocorrelation where patches were small. The species that are more vulnerable to the effects of fragmentation tended to be those that have restricted dispersal, such as those that have short-range dispersal (atelechoric), e.g., Phlomis purpurea, Cistus albidus, Teucrium pseudochamaepytis, Brachypodium retusum, and the ballistic species, Genista spartioides. Helianthemum almeriense is another vulnerable species that has actively restricted dispersal (antitelechory), which is common in arid regions. Wind dispersers such as Launaea lanifera were less vulnerable to the effects of fragmentation. Long-distance dispersers whose persistence depends on facilitative interactions with other individuals, e.g., allogamous species such as Thymus hyemalis, Ballota hirsuta, and Anthyllis cytisoides, exhibit disrupted long-range spatial autocorrelation when patch size is reduced.

Effects of fire frequency on species composition in a Mediterranean shrubland

The effect of high fire frequency on the species composition of Mediterranean-type plant communities is reported on the basis of shrubland stands located in Catalonia (Spain) that have experienced from 1 to 5 fires over the last 31 years. We focused on changes in the abundance of species, grouped according to post-fire regenerative traits (resprouting and seed germination) and life form (shrubs, herbaceous graminoids, and herbaceous non-graminoids). High fire frequency was related to a low abundance of obligate resprouter and obligate seeder shrubs. In the latter group, Cistus sp. disappeared in stands with high fire frequency and showed a maximum abundance in stands with low fire frequency. The abundance of facultative resprouter shrubs did not change with fire frequency. This group thus became dominant in the shrub layer at high fire frequency due to the low abundance of obligate resprouter and obligate seeder shrubs. These changes in the abundance of shrub species involve changes in the patterns of relative dominance of regenerative syndromes, in line with fire frequency. An examination of life forms revealed that the abundance of herbaceous non-graminoids and herbaceous graminoids was higher in stands with high fire frequency and the graminoid Brachypodium retusum was dominant at all fire frequencies. These results suggest a loss in the resilience of shrubs after frequent fires, leading to a simplification of vegetation structure, with a shift from shrubland to grassland-type communities, thereby probably enhancing a potential positive herb-fire feedback.

Effect of grass litter on seedling recruitment of the critically endangered Cistus heterophyllus in Spain

Cistus heterophyllus Desf. is an Iberian-north African endemic plant species with only one wild population left in Spain. A sowing experiment under controlled conditions was designed to assess both the seedling emergence rate and the growth fitness of C. heterophyllus on a litter layer of Brachypodium retusum (Pers.) Beau., which forms dense carpets around the remnant population of C. heterophyllus. In order to test the physical effects of B. retusum litter on Cistus seedling recruitment, six sowing treatments in pots were compared that combined three doses of litter (0, 0.6 and 1.1 kg m −2) and different physical locations of the seeds (above, below the litter layer or within a litter–peat mixture). B. retusum litter interfered with the seedling recruitment of C. heterophyllus, negatively affecting both seedling emergence and their early growth. Such an effect was more severe when the seeds were located above a 0.6 kg m −2 litter layer, although seedlings from seeds sown under the litter showed a growth reduction ranging from 58% to 100% compared to the no-litter treatment. A significant negative effect of the litter–peat mixture on the number of leaves, leaf size and number of branches of seedlings was also inferred. These data provide experimental evidence on the serious threat that B. retusum litter represents for the conservation and regeneration of the last population of C. heterophyllus in Spain.

Root tensile strength and root distribution of typical Mediterranean plant species and their contribution to soil shear strength

In Mediterranean environments, gully erosion is responsible for large soil losses. It has since long been recognized that slopes under vegetation are much more resistant to soil erosion processes compared to bare soils and improve slope stability. Planting or preserving vegetation in areas vulnerable to erosion is therefore considered to be a very effective soil erosion control measure. Re-vegetation strategies for erosion control rely in most cases on the effects of the above-ground biomass in reducing water erosion rates, whereas the role of the below-ground biomass is often neglected or underestimated. While the above-ground biomass can temporally disappear in semi-arid environments, roots may still be present underground and play an important role in protecting the topsoil from being eroded. In order to evaluate the potential of plant species growing in Mediterranean environments to prevent shallow mass movements on gully or terrace walls, the root reinforcement effect of 25 typical Mediterranean matorral species (i.e. shrubs, grasses herbs, small trees) was assessed, using the simple perpendicular model of Wu et al. (Can Geotech J 16:19–33, 1979). As little information is available on Mediterranean plant root characteristics, root distribution data were collected in SE-Spain and root tensile strength tests were conducted in the laboratory. The power root tensile strength–root diameter relationships depend on plant species. The results show that the shrubs Salsola genistoides Juss. Ex Poir. and Atriplex halimus L. have the strongest roots, followed by the grass Brachypodium retusum (Pers.) Beauv. The shrubs Nerium oleander L. and the grass Avenula bromoides (Gouan) H. Scholz have the weakest roots in tension. Root area ratio for the 0–0.1 m topsoil ranges from 0.08% for the grass Piptatherum miliaceum (L.) Coss to 0.8% for the tree Tamarix canariensis Willd. The rush Juncus acutus L. provides the maximum soil reinforcement to the topsoil by its roots (i.e. 304 kPa). Grasses also increase soil shear strength significantly (up to 244 kPa in the 0–0.1 m topsoil for Brachypodium retusum (Pers.) Beauv.). The shrubs Retama sphaerocarpa (L.) Boiss. and Anthyllis cytisoides L. are increasing soil shear strength to a large extent as well (up to 134 and 160 kPa respectively in the 0–0.10 m topsoil). Whereas grasses and the rush Juncus acutus L. increase soil shear strength in the topsoil (0–0.10 m) to a large extent, the shrubs Anthyllis cytisoides (L.), Retama sphaerocarpa (L.) Boiss., Salsola genistoides Juss. Ex Poir. and Atriplex halimus L. strongly reinforce the soil to a greater depth (0–0.5 m). As other studies reported that Wu’s model overestimates root cohesion values, reported root cohesion values in this study are maximum values. Nevertheless, the calculated cohesion values are used to rank species according to their potential to reinforce the soil.

Vegetation recovery after fuel management in Mediterranean shrublands

Question: What is the effect of fuel management practices in the recovery capacity of seeder‐dominated shrublands?Location: Ulex parviflorus shrubland localities in Mediterranean regions of eastern Spain.Methods: We applied prescribed burning and brush‐chipping as fuel management techniques in three young and three mature shrublands, and evaluated the effects in the following four years.Results: Canopy opening by the treatments allowed increasing species richness through the four years of secondary succession. The treatments produced a change in community structure and dominant species, from the woody seeder Ulex parviflorus to the resprouter grass Brachypodium retusum. Vegetation response was conditioned by both shrubland developmental stage and treatment applied. Burning resulted in more severe modification of the ecosystem, increasing bare soil cover. Four years after fuel management in different aged Mediterranean gorse shrublands, vegetation response followed a similar pattern with the exception of the young, brush‐chipped shrublands. The treatments applied for controlling Ulex parviflorus were seen to be very effective, with the exception of brush‐chipping in young shrublands.Conclusions: Selective brush‐chipping in middle‐aged or mature gorse shrublands would combine a drastic reduction in fire hazard with ecosystem conservation and regeneration.

Factors controlling the water repellency induced by fire in calcareous Mediterranean forest soils

SummaryWater repellency (WR) is a property affected by fire and of crucial importance in the hydrological behaviour of soils after burning. In dry Mediterranean areas knowledge of the factors that control the development of water repellency by fire is of particular interest. We examined such factors in two calcareous soils, a Regosol and a Luvisol, representative of forest areas of southeast Spain. Heating temperature (200–500°C), vegetation type (Rosmarinus officinalis, Pinus halepensis and Brachypodium retusum), quantity of vegetation litter (control, low and high) and type of soil were selected as factors for assessing the WR induced by fire. The two soils exhibited markedly different WR responses after heating, the Regosol being much more susceptible than the Luvisol. Characteristics such as organic matter and clay content seem to determine the different WR responses to heating. We found that the type and quantity of vegetation litter also control the persistence of induced WR. In general, the order of increasing WR was Brachypodium < Pinus < Rosmarinus, and larger amounts of litter induced more WR. Maximum values of WR, most of them classified as severe (901−3600 s), were found in the range of 300−350°C, whereas beyond this temperature WR was destroyed. These results show that water repellency induced by combustion could be limited by environmental factors such as vegetation type and availability of litter, and that soil type and its characteristics also play a decisive role.

Root characteristics of representative Mediterranean plant species and their erosion-reducing potential during concentrated runoff

Gully erosion is an important soil degradation process in Mediterranean environments. Revegetation strategies for erosion control rely in most cases on the effects of the above-ground biomass on reducing water erosion rates, whereas the role of the below-ground biomass is often neglected. In a Mediterranean context, the above-ground biomass can temporally disappear because of fire or overgrazing and when concentrated flow erosion occurs, roots can play an important role in controlling soil erosion rates. Unfortunately, information on root characteristics of Mediterranean plants, growing on semi-natural lands, and their effects on the topsoil resistance to concentrated flow erosion is lacking. Therefore, typical Mediterranean grass, herb, reed, shrub and tree root systems of plants growing in habitats that are prone to concentrated flow erosion (i.e. in ephemeral channels, abandoned fields and steep badland slopes) are examined and their erosion-reducing potential was evaluated. Root density (RD), root length density (RLD) and root diameters are measured for 26 typical Mediterranean plant species. RD values and root diameter distribution within the upper 0.10–0.90 m of the soil profile are then transformed into relative soil detachment rates using an empirical relationship in order to predict the erosion-reducing effect of root systems during concentrated runoff. Comparing the erosion-reducing potential of different plant species allows ranking them according to their effectiveness in preventing or reducing soil erosion rates by concentrated flow. RD in the 0.10 m thick topsoil ranges between 0.13 kg m−3 for Bromus rubens (L.) and 19.77 kg m−3 for Lygeum spartum (L.), whereas RLD ranges between 0.01 km m−3 for Nerium oleander (L.) and 120.43 km m−3 for Avenula bromoides ((Gouan) H. Scholz.) Relative soil detachment rates, compared to bare soils, range between 0.3 × 10-12 and 0.7 for the 0.10 m thick topsoil. The results show that grasses such as Helictotrichon filifolium ((Lag.) Henrard), Piptatherum miliaceum ((L.) Coss.), Juncus acutus (L.), Avenula bromoides ((Gouan) H. Scholz), Lygeum spartum (L.) and Brachypodium retusum ((Pers.) Beauv.) have the highest potential to reduce soil erosion rates by concentrated flow in the 0–0.1 m topsoil. But also shrubs such as Anthyllis cytisoides (L.) and Tamarix canariensis (Willd.), having high root densities in the topsoil, can reduce erosion rates drastically. Among the species growing in channels, Juncus acutus (L.) has the highest erosion reducing potential, whereas Phragmites australis (Cav.) is the least effective. On abandoned fields, Avenula bromoides ((Gouan) H. Scholz) and Plantago albicans (L.) are the most effective species in reducing concentrated flow erosion rates, while Thymelaea hirsuta (L. (Endl.)) and Bromus rubens (L.) perform the worst. On steep badland slopes, Helictotrichon filifolium ((Lag.) Henrard) and Anthyllis cytisoides (L.) perform the best in the analysis of erosion reducing potential, while Ononis tridentata (L.) is the least effective species. These findings have implications for ecological restoration and management of erosion-prone slopes.

Effects of repeated burning on Mediterranean communities of the northeastern Iberian Peninsula

AbstractQuestion:In relation to a single fire, do repeated wildfires in Mediterranean type ecosystems (1) reduce plant species richness or diversity; (2) modify patterns of abundance or dominance of plant species or (3) alter plant composition?Location:Pinus halepensisdominated communities of Catalonia, northeastern Iberian Peninsula, western Mediterranean Basin.Methods:Regional, paired design with 14 study sites, each consisting of a once burnt area (1994) and a twice burnt area (1975–1993 and 1994). Ten years after the last fire, we recorded all vascular plant species present in nested plots and quantified their relative abundances on transects. We compared species richness, diversity, dominance and relative abundance and species‐area correlations between paired once and twice burnt areas and assessed their floristic composition similarity.Results:No statistically significant differences were found in species richness or diversity. Slopes of species‐area correlations were higher in once burnt areas. In twice burnt areas, dominance by one or two species was higher.P. halepensisshowed lower relative abundance and nanophanerophytes showed higher relative abundance. No differences were found for resprouter, seeder or resprouter‐seeder species. Floristic composition similarity between paired areas tended to be higher in less productive sites.Conclusions:Fire recurrence had contrasting effects on species richness at different spatial scales. Repeated burning reduced the relative abundance of the dominant tree species, which resulted in a higher relative abundance of shrubs. It also promoted the dominance of herbs, particularlyBrachypodium retusum.However, it did not change the relative abundance of regenerative groups. Paired areas were more similar as they were more Mediterranean in terms of climatic conditions.