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1.
Climatic anomalies may produce, or accelerate, geographic range expansions of species limited by temperature or other climatic variables. Most such expansions are only temporary, before the prevailing climatic conditions drive the founder populations extinct. In contrast, here, we report a recent rapid shift of the range limit during the record hot summer of 2003 in southern Europe that has the potential to be both permanent, and to have important implications on species range dynamics in general. The winter pine processionary moth (Thaumetopoea pityocampa), an important pine defoliator whose larvae feed in colonies during the winter, is limited in its distribution by winter temperatures. In the last three decades, warmer winters have led to a gradual but substantial expansion of its range both latitudinally and altitudinally. In the summer of 2003, T. pityocampa underwent an extraordinary expansion to high elevation pine stands in the Italian Alps; its altitudinal range limit increased by one third of the total altitudinal expansion over the previous three decades. In an experiment, we found flight activity of newly emerged females to increase with temperature. By determining a threshold temperature for flight take‐offs under controlled conditions, we calculated that the nights above the threshold temperature were over five times more frequent, and considerably warmer, at the range limit in 2003 than in an average year. We therefore attribute the colonization of extreme, high‐elevation sites to increased nocturnal dispersal of females during the unusually warm night temperatures in June – August 2003. Importantly, the colonies established at extreme sites survived the winter and produced offspring in 2004, although the range did not expand further because of low night temperatures that year. We discuss several life‐history characteristics of T. pityocampa that maximize the likelihood of population persistence at the new range limit. As global warming continues and climatic anomalies are predicted to become more frequent, our results draw attention to the importance of extreme climatic events in the range formation of phytophagous insects.  相似文献   

2.
Growth models can be used to assess forest vulnerability to climate warming. If global warming amplifies water deficit in drought‐prone areas, tree populations located at the driest and southernmost distribution limits (rear‐edges) should be particularly threatened. Here, we address these statements by analyzing and projecting growth responses to climate of three major tree species (silver fir, Abies alba; Scots pine, Pinus sylvestris; and mountain pine, Pinus uncinata) in mountainous areas of NE Spain. This region is subjected to Mediterranean continental conditions, it encompasses wide climatic, topographic and environmental gradients, and, more importantly, it includes rear‐edges of the continuous distributions of these tree species. We used tree‐ring width data from a network of 110 forests in combination with the process‐based Vaganov–Shashkin‐Lite growth model and climate–growth analyses to forecast changes in tree growth during the 21st century. Climatic projections were based on four ensembles CO2 emission scenarios. Warm and dry conditions during the growing season constrain silver fir and Scots pine growth, particularly at the species rear‐edge. By contrast, growth of high‐elevation mountain pine forests is enhanced by climate warming. The emission scenario (RCP 8.5) corresponding to the most pronounced warming (+1.4 to 4.8 °C) forecasted mean growth reductions of ?10.7% and ?16.4% in silver fir and Scots pine, respectively, after 2050. This indicates that rising temperatures could amplify drought stress and thus constrain the growth of silver fir and Scots pine rear‐edge populations growing at xeric sites. Contrastingly, mountain pine growth is expected to increase by +12.5% due to a longer and warmer growing season. The projections of growth reduction in silver fir and Scots pine portend dieback and a contraction of their species distribution areas through potential local extinctions of the most vulnerable driest rear‐edge stands. Our modeling approach provides accessible tools to evaluate forest vulnerability to warmer conditions.  相似文献   

3.
Climatic changes and weather extremes are causing shifts in distribution of tree species, affecting productivity of forests. With the northwards advance of deciduous species in Northern Europe, Scots pine (Pinus sylvestris L.) is predicted to decrease survival and productivity. Nevertheless, Scots pine have adapted to diverse environments, hence selection among its populations could be applied to sustain productivity of stands under changing climate. In this study, sensitivity of tree-ring width of Eastern European provenances of Scots pine differing by field performance (Dippoldiswalde, Eibenstock, Rytel, Gustrow, and Kalsnava) to weather extremes in three trials in Latvia (hemiboreal zone) was assessed via pointer year and tolerance analyses. The studied provenances were sensitive to winter temperature regime; the effects of water deficit and vegetation period’s length were also observed, likely due to warming. The sensitivity of tree-ring width to weather extremes, which differed among the provenances indicating plasticity of growth, correlated with field performance. Although transferred north, the top-performing provenances (Gustrow and Rytel) were able to promptly recover after cold spells as well as dry summers and were able to benefit from warm winters and precipitation-rich summers. The bottom-performing provenances (Dippoldiswalde and Eibenstock) were sensitive to cold spells and summer water deficit, yet were unable to benefit from warm winters, nor moist summers. Considering sensitivity and resilience of growth, the studied top-performing provenances, particularly Rytel, showed commercial potential in the hemiboreal region under warming climate.  相似文献   

4.
This study analyses the consequences of previous defoliation on the survival of the larvae of the pine processionary moth Thaumetopoea pityocampa (Denis and Schiffermüller) feeding on relict Scots pine Pinus sylvestris (L.) ssp. nevadensis Christ in the Sierra Nevada mountains (SE Spain). Egg batches of the pine processionary moth were placed on four groups of Scots pines that underwent different periods of herbivory. The larval survival was related to the nitrogen content, fibre, phenolics and terpenes in the needles. Larval survival was higher in undefoliated pines, lower in pines defoliated two consecutive years, and intermediate in pines defoliated only one year, suggesting a direct relationship between previous defoliation and larval survival. In contrast, none of the characteristics of the needles showed a clear relationship with larval survival. The resulting reduction in larval number also affects the capacity of the larvae to develop during winter, because it hampered nest warming. Thus, previous defoliation limits, although it does not impede, the possibility of repeated defoliation on Scots pine.  相似文献   

5.
Aim Forest ecosystems dominated by fire‐sensitive species could suffer shifts in composition under altered crown fire regimes mediated by climate change. The aims of this study were to: (1) study the spatio‐temporal patterns and the climatic distribution of fires in Scots pine (Pinus sylvestris) forests during the last 31 years in north‐eastern Spain, (2) evaluate the climatic vulnerability to fire of these forests in Spain, (3) analyse the regeneration of Scots pine after fire, and (4) predict the mid‐term maintenance or replacement of Scots pine in burned areas. Location Catalonia (north‐eastern Spain): the southern distribution limit of Scots pine. Methods We characterized the spatio‐temporal and the climatic distribution of fires that occurred in Catalonia between 1979 and 2009. We used a generalized linear model to characterize the climatic vulnerability to fire of Scots pine in the whole of Spain. We assessed the regeneration of the species after crown fires in nine burned areas in Catalonia. The resulting data were integrated into a stochastic matrix model to predict the mid‐term maintenance or replacement of Scots pine in burned areas. Results During the last three decades, Scots pine forests distributed in dry sites were most affected by fire. Our assessment of the vulnerability to fire of Scots pine forests in Spain as a whole, based on climatic and topographical variables, showed that 32% of these forests are vulnerable to fire, and that this proportion could increase to 66% under a conservative climate change scenario. Field data showed almost no regeneration of Scots pine after crown fires, and a limited capacity to recolonize from unburned edges, even in relatively old fires, with 90% of recruits located in the first 25 m from the edge. This process could be delayed by the elapsed time for new recruits to achieve reproductive maturity, which we estimated to be c. 15 years. Finally, our matrix model predicted the replacement of burned Scots pine forests by oak (Quercus sp.) forests, shrublands or mixed resprouter forests. Main conclusions Increased vulnerability to fire of Scots pine forests under future, warmer conditions may result in vegetation shifts at the southern edge of the distribution of the species.  相似文献   

6.
  • 1 The disruption of host‐finding cues has been proposed as a key mechanism underlying the lower damage caused by phytophagous insects in mixed forests. We tested this hypothesis by investigating the distribution of pine processionary moth Thaumetopoea pityocampa (Denis & Schiffer‐Müller) (Lepidoptera) infestation at the edges of pure stands of Pinus pinaster (AÏton) at some distance from nonhost trees (Experiment 1) or bordered in part by a broadleaved hedgerow (Experiment 2).
  • 2 An ‘edge effect' was demonstrated, with trees at the edge of the stand being more heavily infested than those at the interior of the stand.
  • 3 The presence of a nonhost broadleaved hedgerow in front of the edge of the pine stand resulted in lower T. pityocampa infestation. There were significantly fewer T. pityocampa nests behind the hedgerow than on the exposed part of the edge. The presence of the hedgerow did not dilute or repel T. pityocampa infestation further into the pine stand, although it decreased the infestation of T. pityocampa throughout the pine stand. The decrease in T. pityocampa infestation behind the hedgerow was greater when the broadleaved hedgerow was taller than the pine trees.
  • 4 These results highlight the benefits of using nonhost tree species on the edge of monospecific forest stands to reduce insect damage. This approach could be promoted as an innovative forest pest management method.
  相似文献   

7.
Aim This work investigates the population genetic effects of periodic altitudinal migrations and interstadial fragmentation episodes in long‐term Scots pine (Pinus sylvestris L.) populations at a regional scale. Location The study focuses on Scots pine populations in the northern Meseta and peripheral mountain chains, central and north‐western Iberian Peninsula. The ample macrofossil record in the area shows that this 60,000‐km2 region represent a glacial refugium for Scots pine. The species occupied large areas on the Meseta plains during glacial cold stages, but it has periodically sheltered at high elevation in the surrounding mountain chains during warm episodes, conforming to a fragmented pattern similar to its present‐day distribution. Methods We perform a fine‐scale chloroplast microsatellite (cpSSR) survey to assess the genetic structure of 13 montane Scots pine isolates in the northern Meseta (total N = 322 individuals). Using a hierarchical analysis of molecular variance (amova ), we test the hypothesis of genetic isolation among disjunct mountain areas. We use a standard coalescence model to estimate genealogical relationship among populations, investigating the potential role of the regional relief as a factor influencing historic gene exchange among Scots pine populations. Results Population haplotypic diversity was high among Scots pine populations (He = 0.978), greater than values reported for other more thermophilic pine species in the Iberian Peninsula. The amova revealed low (but significant) differentiation among populations (ΦST = 0.031, P = 0.010), showed that the disjoint montane distribution could not account for the genetic divergence among areas (ΦCT = 0.012, P = 0.253), and that there was non‐trivial subdivision among populations within the same mountain region (ΦSC = 0.021, P = 0.012). The genealogical relationships among populations showed that Scots pine isolates growing on disjoint mountain blocks, but on slopes flowing to the same basin, were genetically closer than populations growing on different slopes of the same mountain chain, flowing to different basins. Main conclusions The observed genetic structure for Scots pine is consistent with its population history, inferred from the palaeobotanical record, with vertical migrations throughout climatic pulses and with the drainage basins and large long‐term population sizes connecting different mountain blocks during the cooler glacial periods. Overall, the results suggest that, despite periodic interstadial fragmentation episodes, Scots pine biology provides for the long‐term maintenance of high within‐population and low among‐population genetic diversity at neutral genetic markers.  相似文献   

8.
The relationships between climatic variables and Scots pine (Pinus sylvestris L.) growth and needle dynamics were studied in three stands in Estonia and in four stands located near the northern timberline in Lapland. The trees sampled in Estonia had low correlations with the analysed climatic variables (air temperature, precipitation and indices of atmospheric circulation). Moreover, the weak cross-correlation of the time-series of the Estonian sample trees indicated that Scots pine is affected mainly by local factors in that region. In Lapland, however, height increment and needle production correlated strongly among trees within a stand (mean r=0.45 and 0.46, respectively) and between stands (r=0.32 and 0.37). Radial increment also showed a high inter-correlation among the trees within a stand in Lapland (r=0.45). Both height increment and needle production were strongly influenced by the temperature regime of the previous summer in Lapland (mean r=0.64 and 0.64, respectively). Radial increment was correlated with the mean July temperature of the current year (mean r=0.29). The correlations between the indices of atmospheric circulation and tree attributes were weak, while the strongest correlation was between the Ponta Delgada NAO index (PD–NAO) and height increment and needle production in Lapland. Height increment, needle production and radial increment have increased since the 1990s in the trees growing in Lapland. This may indicate a positive effect of climate warming on tree growth in Lapland. In Estonia, where climatic conditions do not limit tree growth, the climate warming seems not to directly influence the growth and needle dynamics of Scots pine.  相似文献   

9.
  1. Bush crickets (Orthoptera, Tettigoniidae) are known predators of egg batches of the pine processionary moth (Thaumetopoea pityocampa Denis and Schiffermüller, Lepidoptera: Notodontidae), a severe pest in Mediterranean pine woodlands. Bush crickets have been proposed as biological control agents of T. pityocampa populations, although their characteristics as generalist predators suggest that this would be possible only during the low‐density phases of the processionary population cycle.
  2. We combined observational and experimental approaches aiming to determine the role played by the bush cricket Steropleurus andalusius as a regulator of T. pityocampa.
  3. The synchrony of the phenology of T. pityocampa egg batches and the activity of bush crickets was poor, with the activity of bush crickets being longer than the period during which egg batches were available.
  4. The predation rate of bush crickets reached 23%, varied in time and space, and was independent of T. pityocampa egg‐batch density. There was no relationship between the egg‐batch densities and bush cricket abundance, and no response to experimental variations in egg‐batch density.
  5. Analysis of microhabitat selection suggests that T. pityocampa egg‐batch predation is a by‐product of the substrate selected by bush crickets for mating, and does not correspond with active searching of egg batches as food.
  6. These findings do not rule out the possibilty of bush crickets being natural regulators of T. pityocampa populations, although they impose limits with respect to their future use in biological control.
  相似文献   

10.
Predicting the potential geographical distribution of a species is particularly important for pests with strong invasive abilities. Tetranychus evansi Baker & Pritchard, possibly native to South America, is a spider mite pest of solanaceous crops. This mite is considered an invasive species in Africa and Europe. A CLIMEX model was developed to predict its global distribution. The model results fitted the known records of T. evansi except for some records in dry locations. Dryness as well as excess moisture stresses play important roles in limiting the spread of the mite in the tropics. In North America and Eurasia its potential distribution appears to be essentially limited by cold stress. Detailed potential distribution maps are provided for T. evansi in the Mediterranean Basin and in Japan. These two regions correspond to climatic borders for the species. Mite establishment in these areas can be explained by their relatively mild winters. The Mediterranean region is also the main area where tomato is grown in open fields in Europe and where the pest represents a threat. According to the model, the whole Mediterranean region has the potential to be extensively colonized by the mite. Wide expansion of the mite to new areas in Africa is also predicted. Agricultural issues highlighted by the modelled distribution of the pest are discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

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