Short-term effects of different fire severities on soil properties and Pinus halepensis regeneration

Considering that diverse fire severities can affect soil properties differently,the aim of this study was to examine to what extent changes in soil properties caused by fire could condition seedling establishment.This new approach is for identifying a new fire cause-effect chain to qualify the impacts of fire on soils with the purpose of using fire as a tool in forest management to favour Pinus halepensis Mill.regeneration.The study area was a reforested P.halepensis area which had been crossed by fire for78.8 ha,causing various degrees of damage.The forest was subdivided into three large areas according to the gravity of crown scorch,[low(LS),medium(MS)and high(HS)severity],on the basis of needle yellowing which usually occurs after exposure to direct flames.Results showed significant differences in soil properties with respect to fire severity.In the HS area,total nitrogen and carbon were considerably reduced while ash and phosphorus contents significantly increased.The changes in soil properties,in particular to nutrient levels,affected P.halepensis regeneration,mainly the first year after the fire.Greater regeneration occurred in areas affected by moderate fire severity in which the temperatures reached increased the mineralization of soil organic matter with the consequent release of nutrients available for seedling growth.Additionally,moderate fire severity suppressed the regeneration of grasses,reducing the interspecific competition.Heights of seedlings were inversely proportional to the density of grasses.Where the number was abundant(LS),the height was modest;conversely,where the number was low(HS),the greater hypsometric differentiation of pine seedlings was observed.These results suggest that moderate fire severity represents an environmental stress(hormesis)altering microscale conditions to increase pine germination and establishment.The exposure of P.halpensis to a moderate environmental factor that is damaging at higher intensities,induces an adaptive beneficial effect on seedling regeneration.This data can re-evaluate the assertion that coniferous burned areas,if left unmanaged,would remain unproductive for an indefinite period.

Antibacterial potential of essential oils of the needles of Pinus halepensis against Staphylococcus aureus and Escherichia coli

Objective:To examine the in vitro antimicrobial activities of essential oil of the needles of Pinus halepensis(P.halepensis).Methods:The antibacterial activity of essential oil of the needles of P.halepensis was determined using the agar well diffusion technique and disc diffusion method against Staphylococcus aureus ATCC 25923,and Escherichia coli ATCC 25922.Results:The diameter of zones of inhibition exhibited by the essential oil was between 6 and 17 mm.The essential oils was compared favorably with gentamycin used as a standard control.The minimum inhibitory concentration determined by the agar well diffusion method was 0.52 mg/mL for Staphylococcus aureus and 2.15 mg/mL for Escherichia coli.The minimum bactericidal concentration of the oils against the two microorganisms was 4.17 mg/mL.Conclusions:The results obtained from this study reveal that P.halepensis essential oils possess antibacterial activities and can be used as antimicrobial agents in the search for new drugs.

Projecting the distribution and abundance of Mediterranean tree species under climate change:a demographic approach

Distribution and abundance patterns of species arise from the spatiotemporal dynamics of demographic processes.Population rates of birth,death,growth and patterns of dispersal are,in turn,influenced by environmental conditions and biotic interactions.However,current approaches for modelling large-scale geographical patterns often bypass these simple premises.centred in the mainland territory of Spain and using Pinus halepensis as a case study,our goal was to gain insight into the main driv-ers affecting local demographic processes,and how large-scale distribution and abundance patterns are shaped by these local variations in vital rates.Methods We applied the integral projection methodology to develop a spa-tially explicit demographic model of tree species in mainland Spain,using individual-level data from a national forest inventory.In our integral projection model,environmental conditions and competi-tive interactions influence the survival,growth and reproduction of trees,and we model explicitly the dynamic colonization of new patches.With this framework,the projected distribution and abun-dance patterns of P.halepensis up to 2090 were evaluated under two different climate scenarios.Important Findings When environmental conditions were kept constant,popula-tions tended to decrease in net number of adults and to increase in net basal area,thus consisting in fewer and bigger individuals.Accounting for climate change in our simulations exacerbated the trend in mortality,causing widespread losses in number of trees,and few locations maintained populations of>100 adult individu-als per hectare.the expected increase in mortality under climate change,on the other hand,prompted a higher degree of regeneration via the release of niche space,although not enough to maintain current abundance levels.colonization spatial patterns did not vary significantly with climatic conditions,but the species was able to increase its distribution under climate change more than in a constant climate scenario.Our approach yields relevant information at different spatial scales,from plot-level processes to large-scale abundance patterns.With it,we clearly indicate the strong role that climate change could have in shaping future forest communities through its differential influence on demographic processes.