Effects of fire and water availability on the emergence and recruitment of grasses,forbs and woody species in a semiarid Chaco savanna

In the semiarid Chaco savannas, the balance between herbaceous and woody species affects landscape configuration and ecosystem services such as forage production. Therefore, understanding the factors that control this balance is crucial for management. In a factorial experiment, we assessed the effects of fire and water availability on the emergence and recruitment of grasses, forbs and woody species. The results showed that the effects of fire and water availability on early regeneration stages differed among the three functional groups. For grasses, fire and water addition enhanced emergence when acted solely, but only the positive effects of fire were translated into a greater recruitment, irrespective of the water availability. For forbs, only water addition, when acted solely, promoted the emergence, although this effect was not translated into a greater recruitment. Lastly, in the case of woody species, both fire and water addition reduced emergence and recruitment. Our results support the notion that both fire and greater water availability would contribute to the maintenance and recovery of a grass‐dominated state of vegetation through a positive effect of fire on grasses recruitment and a general negative effect of fire and water on woody species emergence and recruitment.     

Post-fire recovery of Mediterranean ground ant communities follows vegetation and dryness gradients

Aim In the Mediterranean Basin, the main forest communities vary in their ability to recover after fire. In this study we analyse the effects of fire on ant communities occurring in various vegetation types distributed along a geographical gradient in the western Mediterranean region. Location The study was carried out in burned and unburned habitats of 22 sites corresponding to eight vegetation types distributed along a gradient of dryness throughout Catalonia (north‐east Spain). Methods We placed five pairs of plots (one plot located in the burned area and the second one placed in the unburned margin) per site. We compared ant communities in these unburned and burned plot types 8 years after fire using pitfall traps. Traps were set out in mid‐May and mid‐July. We analysed the structure and composition of ant communities in the burned and unburned areas of these vegetation types using anova tests, correspondence analysis (CA) and linear regression. Results The resilience of ant communities varies with vegetation type. Ant communities in forests with high resilience also recover rapidly after fire, while those in forests that do not recover after fire show the lowest resilience. Species richness does not depend on burning or vegetation type. The resilience of these Mediterranean ant communities to fire is related to the environmental characteristics of the region where they live. Accordingly, differences between burned and unburned habitats are smaller for ant communities in areas with higher water deficit in summer than for those in moister ones. Main conclusions The structure and composition of ant communities after fire depends on the level of direct mortality caused by the fire. It affects ant species differently, as determined by the habitats used for nesting and foraging. The reestablishment of vegetation cover depends on forest composition before the fire. As vegetation cover determines resource and microhabitat availability and competitive relationships among species, forest composition before the fire also affects post‐fire recovery of ant communities to the medium‐term. Finally, ant communities living in drier areas recover more quickly after fire than those living in moister ones. This pattern might be because in areas with higher water deficit there are more species characteristic of open environments, which are habitats similar to those generated after fire.     

Woody species tolerance to expansion of the perennial tussock grass Ampelodesmos mauritanica after fire

Abstract. In Mediterranean shrublands, post‐fire accumulation of above‐ground biomass of resprouters is faster than that of seeders. This suggests that resprouters may have a competitive advantage. To test this hypothesis, we used a removal experiment to study the effect of the presence of the dominant tussock‐grass Ampelodesmos mauritanica on the resprouting shrubs Erica multiflora and Globularia alypum and on the seeders Rosmarinus officinalis and Pinus halepensis three and four years after a wildfire. Water potential of target plants was also measured to see if Ampelodesmos removal increased water availability. Ampelodesmos marginally reduced growth of all target species but did not influence survival or water potential of any target species. Our results suggest that the effect of climatically influenced water stress was stronger than the effect of Ampelodesmos neighbours. Plant‐plant interactions in this Mediterranean community are weak after fire and the magnitude of the Ampelodesmos effect does not differ between seeders and resprouters.     

Post-fire Aleppo pine growth,C and N isotope composition depend on site dryness

Key message

The post-fire growth responses and changes in wood C and N isotope composition depend on site water availability and fire severity in Mediterranean Aleppo pine forests.

Abstract

Mediterranean forests are subjected to recurrent wildfires and summer droughts. Under warmer and drier conditions, it is required to determine how Mediterranean pines recover after wildfires, and how this translates into changes in tree radial growth and function (e.g. intrinsic water-use efficiency—iWUE). We analysed four Aleppo pine areas located in SE Spain affected by 1994 wildfires and subjected to different water availability, ranging from mesic to semi-arid conditions. We combined dendrochronological analyses with δ¹³C and δ¹⁵N wood isotopes to quantify the changes in radial growth (expressed as Basal Area Increment—BAI) and functional responses (iWUE and N cycling) to three fire severities (unburned sites, low and medium severities). We expected that the post-fire release in nutrients and a reduction in competition for water would enhance radial growth. We found that fire did not significantly alter growth patterns at the driest sites, but increased BAI at the wettest sites. δ¹³C was significantly (P ≤ 0.01) more negative only in burned stands located at the wettest site indicating a decreased iWUE and thus improved water availability. However, the δ¹⁵N was higher in severely burned than in unburned plots from all sites but the wettest site, indicating a potential fertilization effect of fire in sites subjected to mild drought severity. Site water availability determined how fire affected subsequent modifications in growth and tree functioning of Aleppo pine forests, that is, changes in iWUE and N cycling. Therefore, site dryness should be explicitly considered to forecast the growth and functioning responses of Mediterranean pine forests to the predicted increasing recurrence of fire events due to global warming.

     

Effects of water and a nutrient pulse supply on Rosmarinus officinalis growth,nutrient content and flowering in the field

Rosmarinus officinalis is a dominant shrub species of calcareous Mediterranean communities that has increased its presence in wide areas due to fire frequency increase and field abandonment. We aimed to study the capacity of adult shrubs to respond to nutrient pulses such as those produced by fires and human driven eutrophycation. In a 5 years old post-fire Mediterranean shrubland we conducted an experiment to investigate the effects of irrigation and N and P fertilisation on the growth, nutrient status and flowering effort of adult plants of the dominant shrub R. officinalis in a post-fire shrubland. The responses were monitored during the immediate 3 years after fertilisation. P fertilisation increased plant growth, produced a great increase in P aerial mineralomass and P concentration in leaf and stems and had a slight positive effect on flowering effort. Irrigation increased plant growth, but did not have significant effects on nutrient contents and flowering. The results show that adult individuals of the Mediterranean shrub R. officinalis have a notable capacity to positively respond in growth and in nutritional status to a sudden increase of the limiting nutrient, in this case P, and in a lesser extent, to an increase of water supply. These capacities may be important under the more unpredictable nutrient and water availability conditions expected for the near future; they will allow to take advantage of the pulses of higher nutrient and water availability in the middle of dry periods, thus increasing the community capacity to improve the nutrient retention in the ecosystem.     

Root morphology and water transport of Pistacia lentiscus seedlings under contrasting water supply: A test of the pipe stem theory

Restoration of degraded Mediterranean areas often requires the reintroduction of key-stone woody species but the establishment of seedlings of native species is frequently poor. This is partly due to insufficient knowledge of the ecology of these species at the seedling stage. Fast rooting and efficient water supply under water limiting conditions may be crucial to withstand summer drought and ensure establishment. However, knowledge of the relationship between root morphology and the water transport capacity of Mediterranean woody species in response to drought is still scarce. We evaluated the effect of low water availability on biomass allocation, root morphology and transpiration of a common Mediterranean shrub species, Pistacia lentiscus L. Seedlings of this species were grown in pots filled with soil under glasshouse conditions for 6 months, and irrigated either weekly (W+) or monthly (W?). Low water availability strongly reduced all fractions of biomass, and decreased relative biomass allocation belowground. Average diameter of fine roots colonising the soil was higher in W+ plants, but this resulted in only marginal effects on specific root length. Water limitation did not affect the topology of secondary roots colonising the soil. Surprisingly, the ratio of leaf area to coloniser roots surface area was higher in W? seedlings. Sapwood area was strongly correlated with leaf area, secondary roots cross-sectional area, and surface area of fine roots colonising the soil when all seedlings were pooled. In agreement with the pipe stem theory, the ratio of sapwood area to leaf area was not affected by watering regime. Plant water loss when soils were taken to field capacity was significantly correlated with leaf area, sapwood area, secondary roots cross-section area and coloniser roots surface area. Water loss at high water availability was greatly reduced in W? plants, as leaf area decreased and transpiration rates on a leaf area basis were similar in W+ and W? seedlings. P. lentiscus showed limited capacity to acclimate to low water availability by modifying biomass allocation and root morphology. Thus, parallel to what has been observed aboveground, this species can benefit from periods of high water availability by showing relatively high root growth rates, but may respond poorly to water scarcity.     

Feeding activity and dietary composition of roe deer at the southern edge of their range

We studied feeding activity and dietary components of hand-reared European roe deer (Capreolus capreolus) in Israel. Our ultimate goal was to assess habitat suitability for future reintroduction of the species, which has been locally extinct for nearly a century. Activity patterns, diet composition, and body mass of four does were monitored in two (fenced) typical east Mediterranean habitats: mature forest and scrubland recovering from fire. Food supplements were provided between trials. Throughout the year, the deer exhibited diurnal and nocturnal activity, mostly at dawn and dusk. Diet composition varied considerably between seasons and habitats, demonstrating the opportunistic flexibility of the deer. In both habitats, the deer fed on over 85% of the plant species but preferred a particular plant species or parts. In summer and early autumn, fruits and seeds became the dominant portion of their diet. In our semi-natural experimental setup, deer maintained body mass through the winter and spring. Weight loss occurred as the dry season advanced, but the animals rapidly regained mass when annuals and grasses became available following the first rains. In the east Mediterranean habitats, water availability seems more problematic for deer survival than food availability.     

The effect of mean and variance in resource supply on survival of annuals from Mediterranean and desert environments

Resource availability is often characterized by mean annual amounts, while ignoring the spatial variation within habitats and the temporal variation within a year. Yet, temporal and spatial variation may be especially important for identifying the source of stress in low productivity environments such as deserts where resources are often pulsed and resource renewal events are separated by long periods of low resource availability. Therefore, the degree of stress will be determined in part by the length of time between recharge events. Here, we investigated the effect of timing and total amount of water application on two congeneric pairs, each with a population from a low (desert) and a high (Mediterranean) productivity habitat. As expected, highest survival and greatest growth were found at low or intermediate recharge intervals, and the magnitude of response to increases in total seasonal amounts was greater for Mediterranean species than desert species. The species that had greater survival switched in the hierarchy under high total water depending on interval length. These results demonstrate that temporal variation in resource availability can be as important as annual total amounts for plant performance and that response to temporal dynamics can vary between species. This has implications for community-level processes, as competitive hierarchies may switch based on resource dynamics rather than only total availability.     

Vegetative and seedling regeneration after fire in planted Sardinian pinewood compared with that in other areas of Mediterranean-type climate

Aim Fire is a key disturbance in Mediterranean‐type climates. It has effects on plant community structure and composition and on the evolution of different groups of the flora. This study aimed to quantify changes in demography and vegetative regeneration caused by fire in key species in Mediterranean vegetation and to examine the hypothesis of convergence in characteristics of species in relation to fire by comparing the occurrence of bioecological groups of plants in the Mediterranean basin with groups of plants in other areas of Mediterranean‐type climate. Methods Changes in the demography and species composition after fire were studied in a plant community developed from a pinewood (Pinus halapensis Miller plantation) in north‐western Sardinia. The demography of the three main species dominating the community after fire, Cistus monspeliensis L., Pistacia lentiscus L. and Chamaerops humilis L., was quantified by quadrat measurements in areas of the plantation which had never been burnt and in different parts 1 and 8 years after fire. Vegetative regeneration of resprouting species was also quantified. From the results of the survey and examination of published material, comparison was made between bioecological groups of species in different regions with Mediterranean‐type climate to assess the similarities and differences in the biogeographic distribution of what can be broadly considered fire‐related functional groups of plants. Results Seeder and sprouter species showed contrasting population responses to fire in an area planted to pines over 50 years ago but subsequently in part subjected to fire. Mean species richness at a 25 m² scale decreased by c. 28% over 8 years after fire. C. monspeliensis in the unburnt pinewood was sparse and sporadic but recruitment after fire was prolific and produced plant densities similar to those of similar seeder species in other Mediterranean Basin areas and in Californian chaparral. However density was very variable between burnt areas of different ages. In particular, seedling recruitment was much lower under the canopies of P. lentiscus than away from the canopy. Sprouter species (P. lentiscus and C. humilis) had recruited into the pinewood over time since planting of the pines but did not recruit after fire. Above‐ground parts of plants were killed by fire and resprout stem density per plant increased initially but later decreased slightly due to self thinning of stems on each plant. Main conclusions Plant demographic and floristic changes after fire in the Sardinian pinewood were similar to those reported for other Mediterranean plant communities. Resprouting species only recovered by vegetative means and, in contrast to seeder species, underwent thinning of stems within, rather than between, plants, so plant density did not change after fire in resprouting species. The Tertiary relic, strongly resprouting, animal‐dispersed group of species in the Mediterranean Basin has a homologous group in the North American mediterraneoid flora but not in the Southern Hemisphere. In contrast, the general group of resprouting species which recruit after and/or between fires in the Southern Hemisphere mediterraneoid areas corresponds to only a small group of taxa in the Mediterranean basin. The bioecological group of seeder species, which are killed by and establish prolifically after fire, are represented in both Northern and Southern Hemisphere Mediterranean‐type heathlands but are much more species rich in the south.     

Light and nitrate effects on seed germination of Mediterranean plant species of several functional groups

Post-fire conditions are characterized by enhanced light and the availability of nitrogenous compounds in the soil. It is not known, however, to what extent light or nitrogenous compounds control the germination response of species growing in burned areas and, in particular, whether functional groups of plants differ in their response. The germination response to light and nitrate was tested for 53 species representative of the flora of a Mediterranean recently burned area in Central-Eastern Spain. Differences in germination among species, with and without taking into account their phylogeny, were studied by classifying them according to their life-form (chamaephytes, hemicryptophytes), regeneration strategy (non-sprouters, sprouters) and geographical distribution range (Iberian Peninsula endemics, Mediterranean, widely distributed species). The overall germination mean was not affected by any of the two treatments. There were statistically significant interactions between species and the two treatments. That is, not all species were equally affected, and about 30% of the species were significantly affected by light (half of them positively and the other half negatively) and 25% by nitrate (most of them positively). Species response was related to functional groups. Light response (stimulation vs. non-stimulation) was associated to life-form, regeneration strategy and distribution range. Hemicryptophytes, sprouters and widely distributed species were positively affected by light. No evidence of such an association for nitrate was found. No statistically significant effects of light and nitrate on the mean germination of the various groups (life-form, regeneration strategy, distribution range) were found. Moreover, significant interactions emerged between light and nitrate for all three groups. In summary, the studied set of plants appears to be non-dependent on factors that may change with fire, such as increased light and soil nitrate, for germination. Nonetheless, some species and groups will be affected by such changes. That means that fire will modify the relative balance of germination among species and functional groups. Due to the particular sensitivity of Iberian Peninsula endemics to light, a factor that significantly changes with fire, these species may be at risk under the current fire regime.     

Influence of fire prevention management strategies on the diversity of butterfly fauna in the eastern Pyrenees

Fire prevention management is becoming a necessity in many Mediterranean locations to regulate fire of natural or human origin. However, very few studies have determined the real effects of the strategies adopted on local fauna. Butterflies are sensitive to local changes and they can thus serve as indicators of environmental changes. Three different types of fire prevention management approaches in three different localities in the Eastern Pyrenees (France) were performed and the butterfly community composition was investigated. We show that of the 80 species of butterflies observed, 36 % can be considered as biological markers. An original objective treatment of data using hierarchical distance analysis combined with a neural network analysis (Self-Organizing Maps) was applied in this study. Our conclusions are that the overall number of species is maintained independently of the fire prevention type but that some important changes are observed among butterfly communities, with a clear reduction of the numbers of endemic/specialized species in favour of generalist ones for the two most drastic fire prevention management approaches studied here. The influence of such approaches is discussed on the basis of the conservation of Mediterranean species of Lepidoptera.     

Plant functional strategies and environmental constraints in Mediterranean high mountain grasslands in central Spain

Background: The relationship between plant traits and environmental factors will be of value in understanding of functional strategies that plants have developed to cope with the environmental constraints on plant life in Mediterranean high mountain ecosystems.

Aims: The aims of this study were (1) to explore the variation in plant traits in relation to environmental variability; (2) to analyse the functional strategies of species; and (3) to assess the habitat constraints for the species in the study area.

Methods: We sampled the floristic composition of 76 1 m?×?1 m plots on five summits over 2,100 m above sea level in the mountains of the Sistema Central, Spain. Soil properties and temperature and grazing disturbance parameters were recorded. Eight plant traits were assessed in 21 species. Environmental variability and the co-variation of functional traits were analysed by RDA and PCA, respectively. Plant traits and environmental variability were related using fourth-corner analysis.

Results: Traits related to resource acquisition, such as leaf size and N concentration, varied with soil temperature and estimated summer water availability. Leaf dry matter content was found to be related to estimated water availability and soil pH. Seed mass was a factor of snow cover duration and water availability, and clonality to the duration of the vegetative period and estimated water availability. Grazing disturbance was related to the mean plant height of the species.

Conclusions: The results suggest that low temperatures, rather than water shortage, may be the principal limiting factor for resource acquisition in plants. Nevertheless species establishment is limited by water shortage during summer in these Mediterranean high mountain communities.     

Arboreal and prostrate conifers coexisting in Mediterranean high mountains differ in their climatic responses

In contrast to most high elevation areas, plant growth at Mediterranean mountains is exposed to a summer drought period, which represents an additional climatic constraint to low temperatures. Although arboreal and shrubby conifers coexist at high altitudes, most dendroecological studies have focused on climatic responses of tree species, whereas those of shrubby species remain mostly unexplored. We built tree-ring width chronologies for two conifer species, a shrub (Juniperus sabina) and a tree (Pinus sylvestris), coexisting at three high-altitude localities of the Iberian System mountains, eastern Spain. We analyzed their climate–growth relationships for the period 1950–2009 using correlation analyses and multiple regressions. Coexisting species responded to year-to-year climatic variability in different ways. Radial growth in junipers and pines responded positively to April and May temperatures, respectively. Summer drought constrained growth in both cases, although its impact was stronger on junipers than on pines. Our findings suggest that junipers respond earlier than pines to spring temperatures due to their prostrate morphology which may enhance a fast warming of their cambial meristems after snowmelt. The higher dependence of J. sabina on summer rainfall as compared with co-occurring pines confirms that drought stress negatively impacts secondary growth in Mediterranean mountains. This sensitivity to water availability may be caused by the juniper shallow root systems, which mainly use superficial soil water. The climatic signal registered in J. sabina allows studying the response of other similar shrubby woody species growing in Mediterranean alpine areas to the ongoing climate warming, which could also reduce water availability.     

Functional traits predict drought performance and distribution of Mediterranean woody species

Water availability is one of the key environmental factors that affect plant establishment and distribution. In many regions water availability will decline with climate change, exposing small seedlings to a greater likelihood of drought. In this study, 17 leaves, stem, root, and whole-plant traits of ten woody Mediterranean species were measured under favourable growing conditions and seedling drought survival was evaluated during a simulated dry-down episode. The aims of this study were: i) to assess drought survival of different species, ii) to analyse which functional traits predict drought survival time, and iii) to explain species distribution in the field, based on species drought survival and drought strategies. Drought survival time varied ten-fold across species, from 19 to 192 days. Across species, drought survival was positively related to the rooting depth per leaf area, i.e., the ability to acquire water from deeper soil layers while reducing transpiring leaf area. Drought survival time was negatively related to species ability to grow quickly, as indicated by high relative growth and net assimilation rates. Drought survival also explained species distribution in the field. It was found that species were sorted along a continuum, ranging between two contrasting species functional extremes based on functional traits and drought performance. One extreme consisted of acquisitive fast-growing deciduous species, with thin, soft metabolically active leaves, with high resource use and vulnerability to drought. The opposite extreme consisted of conservative slow-growing evergreen species with sclerophyllous leaves, deep roots, a low transpiring area, and low water use, resulting in high drought survival and drought tolerance. The results show that these drought strategies shape species distribution in this Mediterranean area.     

Vegetation Management for Promoting Ecosystem Resilience in Fire-Prone Mediterranean Shrublands

Dense shrublands constitute highly hazardous fuels in Mediterranean countries. The combination of agricultural land abandonment and fire occurrence in many Mediterranean areas has led to a landscape dominated by shrublands where resprouter species are scarce or absent. Major goals in the management of these areas are to reduce both the fuel loads and their continuity and increase the resilience of the ecosystems by introducing resprouter species. We investigated the performance of one-year-old seedlings of native resprouters, that is, Pistacia lentiscus , Quercus ilex , and Rhamnus alaternus , in a combination of vegetation clearing and mulching with brush chipping in three sites with high amount of fuel load. The planting holes inside the shrublands showed lower radiation and soil surface temperature than those in the cleared areas, whereas soil water content was higher in the mulched holes than in the unmulched ones, especially when water availability was lowest. Seedling survival of Q. ilex and R. alaternus significantly increased within the shrubland; P. lentiscus showed the opposite effect, but its survival was enhanced by the mulching treatment. The three species grew faster in the cleared plots although, unexpectedly, mulching showed a negative effect on Q. ilex relative growth rate in diameter. Our results suggest that the combination of fuel control and reforestation as techniques for shrubland management is an appropriate option, at least in the short term, to redirect vegetation dynamics toward later successional stages, improving ecosystem resilience by the introduction of woody resprouter species.     

Fire regenerative syndromes of forest woody species across fire and climatic gradients

Community resilience after fire is determined by species’ ability to regenerate through two main mechanisms growth of new sprouts (resprouter species) and germination from surviving seed banks or from seeds arriving from neighbouring populations (seeder species). Both the mechanisms are present in Mediterranean communities. The occurrence of both the types in a community depends on fire history and the bio-geographical history determining the available species pool. Regenerative traits also covary with other functional attributes associated with resource acquisition and stress tolerance. As post-fire regenerative responses can be related to various ecological factors other than fire, we tested the hypothesis of a different proportional representation of post-fire regenerative syndromes in forest woody species along a climatic gradient in Catalonia (NE Spain) ranging from Mediterranean to temperate-boreal climates. Specifically, we expected seeder species to become less common with colder and moister conditions while resprouters would not be so influenced by the climatic gradient. We also tested the hypothesis of change in the relative abundance of regenerative syndromes in relation to recent fire history. We analysed a large database obtained from extensive forestry surveys and remote sensing fire records. After correction for spatial autocorrelation, we found an increase in the proportion of seeder species under more Mediterranean conditions and a decrease in fire-sensitive species (with no efficient mechanisms of post-fire recovery) in moister conditions. Resprouter species were similarly present across the whole gradient. A similar pattern was observed after excluding recently burnt plots. Therefore, post-fire regenerative syndromes segregate along the climatic gradient. Recent fires reduced the occurrence of fire-sensitive species and increased the proportion of seeder species. No significant effect was observed on resprouter species. Fire has a sorting effect, shaping the occurrence of species with different regenerative traits. Overall, fire seems to explain better the variability of the proportion of fire-sensitive species and climate the variability of seeder species. In addition, other factors (forestry practices and the covariation between regenerative and functional attributes) are likely to contribute to the regional pattern of regenerative syndromes.     

Broad‐scale patterns in smoke‐responsive germination from the south‐eastern Australian flora

Questions

Fire is a crucial component of many ecosystems. Plants whose seeds germinate in response to smoke may benefit from resource availability in the post‐fire environment. Smoke can influence germination timing and success, as well as seedling vigour, resulting in burgeoning research interest in smoke‐responsive germination. Research in this field has largely focused on four key ‘Mediterranean‐type’ fire‐prone ecosystems: the Mediterranean Basin, South African fynbos, Californian chaparral and Western Australia. There are far fewer studies from south‐eastern Australia, a fire‐prone but not “Mediterranean‐type” region. How does smoke‐responsive germination in this region vary according to ecological, phylogenetic, and methodological variables?

Location

South‐eastern Australia.

Methods

We investigated patterns of smoke‐promoted germination in south‐eastern Australian plants across habitat types, growth forms, fire response strategies, phylogeny, taxonomic levels and smoke application methods. We compiled and interrogated data comprising 303 entries on germination responses to smoke in 233 south‐eastern Australian plant species, from 33 different sources.

Results

Smoke‐responsive germination occurs at a lower rate (~41% of tested species) in south‐eastern Australian flora than it does in fynbos and Western Australian floras, and there is clear patterning within these data. Obligate‐seeding species were more likely to respond, Leguminosae and Rubiaceae were less likely to respond (although we question the generality of these results), while Poaceae were more likely to respond to smoke. Finally, studies using aerosol smoke and studies conducted in situ were most likely to find smoke‐promoted germination.

Conclusions

Obligate seeders and Poaceae may be selected for in habitats with higher fire frequencies, consistent with literature suggesting that short inter‐fire intervals favour grasslands over forests. These findings may be particular to south‐eastern Australia, or more widely applicable; more broad‐scale comparative research will reveal the answer. By synthesizing the south‐eastern Australian smoke germination literature we broaden our understanding beyond the better‐studied Mediterranean‐type floras.

     

Response of ant functional composition to fire

Little is known about the impact of disturbances on functional diversity and the long‐term provisioning of ecosystem services, especially in animals. In this work we analyze the effect of wildfire on the functional composition of Mediterranean ant communities. In particular, we asked whether a) fire changes functional composition (mean and dissimilarity of trait values) at the community level; and b) such fire‐induced functional modification is driven by changes in the relative abundance‐dominance of species or by a replacement of species with different traits. We sampled ant communities in burned and unburned plots along 22 sites in a western Mediterranean region, and we computed two complementary functional trait composition indices (‘trait average’ and ‘trait dissimilarity’) for 12 functional traits (related to resource exploitation, social structure and reproduction) and with two different datasets varying in the way species abundance is considered (i.e. abundance and occurrence data). Our results suggest a set of functional responses that seem to be related to direct mortality by fire as well as to indirect fire‐induced modifications in environmental conditions relevant for ants. Trait average of colony size, worker size, worker polymorphism and the ratio between queen and worker size, as well as the trait dissimilarity of the proportion of behaviorally dominant species and of liquid food consumption, and overall functional diversity, were higher in burned than in unburned areas. Interestingly, different patterns arise when comparing results from abundance and occurrence data. While the response to fire in trait averages is quite similar, in the case of trait dissimilarity, the higher values in response to fire are much more marked when considering occurrence rather than abundance data. Our results suggest that changes in trait average are driven at the same time by replacement of species with different traits and by changes in the relative abundance‐dominance of species, while fire promotes a higher diversity of functions that is primarily driven by rare species that are functionally unique. Overall, we observed major fire‐induced changes in functional composition in Mediterranean ant communities that might have relevant consequences for ecosystem processes and services.     

Soil seed bank,fire season,and temporal patterns of germination in a seeder-dominated Mediterranean shrubland

Soil seed banks play a major role in the post-fire regeneration of Mediterranean shrublands. They vary throughout the year in species composition, abundance, and readiness to germinate. After fire, germination occurs mainly during the following fall to spring. Time of germination can determine recruitment success. It is unclear what factors control post-fire germination and its timing. We tested the effects of season and fire on the readily germinable soil seed bank of a seeder-dominated shrubland. Plots were burned early and late in the summer season (ES, LS). Soil samples were collected before and after fire, and germinated in a chamber simulating successively autumn, winter, and spring conditions. Samples were kept moistened at all times. Fire intensity was similar between ES and LS. Several species of Cistus and herbs, mostly annuals, were dominant. Most germination occurred during the simulated-autumn period, with little subsequent germination during the following two periods. Germination speed (T ₅₀) during simulated-autumn was similar for shrubs and herbs, and independent of season or fire. Germination was lower for two shrubs (Rosmarinus officinalis, Cistus salvifolius) and higher for herbaceous dicots in LS than in ES soils. Fire reduced monocots and enhanced Cistus. Germination period significantly interacted with fire and season in some groups or species, altering the simulated-autumn germination peak. We demonstrate that the seed bank can germinate swiftly under simulated-autumn conditions. Hence, water availability is the main controlling factor of germination. Fire season differentially affected some species or groups, and could affect the post-fire regeneration.     

Role of nesting resources in organising diverse bee communities in a Mediterranean landscape

Abstract.  1. The habitat components determining the structure of bee communities are well known when considering foraging resources; however, there is little data with respect to the role of nesting resources.
2. As a model system this study uses 21 diverse bee communities in a Mediterranean landscape comprising a variety of habitats regenerating after fire. The findings clearly demonstrate that a variety of nesting substrates and nest building materials have key roles in organising the composition of bee communities.
3. The availability of bare ground and potential nesting cavities were the two primary factors influencing the structure of the entire bee community, the composition of guilds, and also the relative abundance of the dominant species. Other nesting resources shown to be important include availability of steep and sloping ground, abundance of plant species providing pithy stems, and the occurrence of pre-existing burrows.
4. Nesting resource availability and guild structure varied markedly across habitats in different stages of post-fire regeneration; however, in all cases, nest sites and nesting resources were important determinants of bee community structure.