Castellví Xaus, Judit

Universitat Autònoma de Barcelona. Facultat de Biociències

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Materials & methodsIntroductionWildres are an important factor in many ecosystems throught the world (Moretti et al., 2002) and have an eect on the fauna in those habitats. EFFECT OF WILDFIRE ON SPIDER COMMUNITIES IN THE WORLD’S FORESTSCASTELLVÍ XAUS, Judit.  Biologia Ambiental degree. Universitat Autònoma de Barcelona. June 2015Results & discussionConclusionsSpiders are diverse and ubiquitous predatory group, individual species distributions are tightly linked to the structural attributes of the habitat, both hunting and web-buildig spiders are sensitive to changes with litter depth and nutrient content and they are a key element of the detritus-based  (Langlands 2011).  Hence, they are a potentially ecological indicators, ideal  for examining post-re responses (Larrive et al., 2005). The aim of the present study is to make a review about the eect of wildres on spiders communities in the world forests. How great are any dierences among post-re ages in abundance or species richness? Are the functional traits dierent between burned and unburned zones?An extensive research in online article databases  have provided the information to make the review. Some databases used are:  Web of Science,  CSIC, Tesis en Xarxa, Research Gate and Scopus.Key words taped in order to nd information were: wildre, spiders, araneae, arthropods, eects of perurtbation. Dierent forests reviewed: mediterranean (Greece), chestnuts forest (Switzerland), conife-rous  forest (Orgeon), boreal forest (Canada),  Pinus sylvestris (Finland) and anarid  meadow (Australia).Reasons for the apparently contradictory eects of re on invertebrates include the varying re regimes, die-ring ecological pre- and post-re conditions,  the die-rence in the taxonomic groups in focus, as well as the season. Fire is an important factor to spiders, controllating the communities and its diversity.  Whereas re can reduce the number of individuals, it does not necessarily have a nega-tive eect on species richness., it can even be positive. This depends on the severity of the re and how it propa-gates during the event (Moretti et al 2002). Arnan, X., Rodrigo, A., Retana, J. (2006). “Post re recovery of Mediterranean ground ant communities follows vegetation and dryness gradients”. Journal of Biogeography, 33: 1246-1258  / Brotons, Ll., Pons, P., Herrando, S. (2005). “Colonization of dynamic Mediterranean landscapes: where do birds come from after re?”. Journal of Biogeography, 32: 789-798. // Cardoso, P., Henriques, S.S., Gaspar, C., Crespo, L.C., Carvalho, R., Schmidt, J.B., Szüts, T. (2009) “Spe-cies richness and composition assessment of spiders in a Mediterranean scrubland”. Journal of Insect Conservation, 13(1): 45-55. // Koponen, S. (2005) “Early succession of a boreal spider community after forest re”. The journal of Arachnology, 33: 230-235. // Langlands, P. R., Brennan, K. E., Framenau, V. W., Main, B. Y. (2011). “Predicting the post‐re responses of animal assemblages: testing a trait‐based approach using spiders.” Journal of Animal Ecology, 80(3): 558-568. -Langlands, P. R., Brennan, K. E., & Ward, B. (2012). “Is the reassembly of an arid spider assemblage following re deterministic?” Austral Ecology, 37(4): 429-439. // Larrivé, M., Fahrig, L., Drapeau, P. (2005) “Eects of a recent wildre and clearcuts on ground-dwelling boreal forest spider assemblages” Canaian Journal of Forest Research”, 35(11): 2575-2588. / Moretti, M., Conedera, M., Duelli, P., Edward, P. J. (2002) “The eects of wildre on ground-active spiders in deciduous forests on the Swiss southern slope of the Alps”  Journal of Applied Ecology , 39: 321-336. -Moretti, M., Obrist, M. K., Duelli, Peter. (2004) “ Arthropod biodiversity after forest res: winners and losers in the winter re regime of the southern Alps”. Ecography 27: 173-186. // Moretti, M., Duelli, P., Obrist, M.K. (2006) “Biodiversity and resilience of arthropod communities after re disturbance in temperate forests”. Oecologia 149: 312–327. // Niwa, C., Peck, R. W.  (2002) “Inuence of Prescribed Fire on Carabid Beetle (Carabidae) and Spider (Araneae).Assemblages in Forest Litter in Southwestern Oregon”. Forestry Sciences Laboratory. 31(5):785-796.// Radea, C., Kazanis, D., Arianoutsou, M. (2010) "Eects of re history upon soil macroarthropod communities in Pinus halepensis stands in Attica, Greece." Israel Journal of Ecology & Evolution 56(2): 165-179.Wikars, L., Schimmel, J.(2001) “Immediate eects of re-severity on soil invertebrates in cut and uncut pine forestsTemperature at 2-5 cm under the soil: 35ºCAt the surface: 700ºC When there is a re...In the burned area hunting species increase signicantly compared to the control (g1). Uetz 1975 describe hunting spiders as oppor-tunistic spiders that hunt on open forest oors and rapidly colonize recently disturbed habi-tats (Buddle et al.,  2000).They can also move deeper into the soil during the re, consequently they could be  insulated from lethal soil temperatures (Moretti et al., 2002).Figure 1: Catch rates of spiders obtained from pitfall traps per week according the area and the hunting strategy in a Boreal forest (Quebec). The study was carried on two years after the re. There is signicant dierence between treatments. Source: Larrivée et al., 2005. 0123456789CONTROL BURNEDNº of individuals per trap per weekHuntersWeb buildersIndividuals/ trap according the area and the hunting strategy If the pre burned area is homogeneous the re will increase the spiders richness creating new microhabi-tats. However, If there  are microhabitats previously established, the re could destroy it and cause a loss of diversity. Hypothesis  1Species with resitant structures (heavy sclerotisation of the cephalotorax,  hunting or burrowing  strategies or species of open forest) will be tipical of recently burned habitats.2The more recurrent  is a re , the less severity it will have. Consequently it will have less impact on spider assemblages, even a posittive eect on richness.  3Species richness will be reduced immediately after the re, then it will recover until the initial richness.4 Functional traits per site  Open forest species increase signicantly after repeated res (Table 1). That is due to the lack of big canopies of trees in the burned forests. The unburned patches of ground and the varying severity of burning across the landscape, would enhance the structural complexity of the forest oor after a wildre (Moretti et al., 2002).That leads to a more variable species composition of spider assemblages.The species richness evolution after the re With 17 years between res there is the major density of spiders (Fig 3).The forest needs a periodof time to recuperate thestructure leading the establishmement of dierent species (Fig 6).Mean density of spiders per site and sampling seasonSome authors underline that optimal habitat for re intolerant species, or  late successional species, would never develop under a regime of frequent res  while other authors point out the importance of re for in-vertebrates in creating a habitat mosaic of dierent successional stages (Buddle et al., 2000).Fire has a more severe impact on species richness at times when animals are active near the surface (s-pring and summer)  than when they are inactive (Riechert & Reeder, 1972).Richness seems to react dierently depending on the re turn over intervals In boreal forests, richness species decrea-ses during at least 7-15 years after the re (Koponen 1995).It has been conrmed that hypotheses 2, 3 and 4 are true, however, hypothesis  1 was impossible to check due to the lack of information about pre re condictions in each zone.It would be interesting to do more studies about the eect of re in dierent forests, with the same pattern leading to a better comparasition for each forest and weather.For a better knowledge of the eect of re more specic taxa should be included in future analyses, promising a better understanding of the complex ecological interactions, and minimising the risk of generalising statements, based on studies with low level of identication.051015202530Unburned Single re Freqüent resSpecies richnessSpecies richness pooled with regard to re frequencyFigura 4: species richness pooled with regard to re frequency. The control  site had never suered from re in the last 35 yr. Chestnut forest (Switzerland). Source: Moretti et al., 2004. Hunter species preferring open and warm areas (Buddleet al. 2000).Linyphiidae GnaphosidaeBurnedUnburnedFigure 2: Number of species per family depending on the area (burned or not) in a Pinus sylvestris forest  (Finland). Source:  Koponen 2005. Others051015202530Nº of species per family per areaLycosidaeGnaphosidae TheridiidaeOften caught in high numbersat burned localities (Fig 1).Nº of speciesLycosidae TheridiiadaeHow aect the recurrency of re in richness species and density?0510152025301 2 3 4Species richnessInformation from diﬀerent articlesSpecies richness per site pooled with regard to information from diﬀerent articles UnburnedBurnedFigure  5: species richness per site pooled with regard to information from dierent articles.  Article 1: Moretti et al., 2002. Article 2: Niwa i Peck, 2002. Article 3: Larrivé et al., 2005. Article 4: Moretti et al.,2004Hypothesis nº 2 conrmed.Density and richness increase with frequent res (Fig 3, Fig 4).Hypothesis nº 3 conrmed. Fire severity not checked.Frequent res benet species richness if the forest has the enough time between res to regenerate.Species richness decreases immediatly after the wilfdire until the third year.The richness increases more than the initial after the third year the initial (g 6).Hypothesis nº 4 not conrmed. Richness species depends on the type forest and the time elapsed since the last re.shoot Spring Summer Fall00,10,20,30,40,50,60,70,8Densitysite burned 50 years before 1995site re-burned 17 years before 1995site re-burned 8 years before 1995Figura  3: mean density of spiders per site and sampling season in a Pinus halepen-sis forest (Greece).  Source:  Radea et al., 2010.Interior forest speciesOpen forest species Edge forest speciesSpecies richness signiﬁcantly by increasing of ﬁre frequency (P<0,05)signiﬁcantly by increasing of ﬁre frequency (P<0,01)signiﬁcantly by increasing of ﬁre frequency (P<0,001)Number of individualssigniﬁcantly by increasing of ﬁre frequency (P<0,01)signiﬁcantly by increasing of ﬁre frequency (P<0,01)signiﬁcantly by increasing of ﬁre frequency (P<0,01)The post-re forests conditions (Table 2) benets open forest species (Table 1).Table 1:   Eects of re frequency on species richness in European chestnut forests (Switzerland). Source:  Moretti et al.,2004 Environmental variables  Unburnt  (n=6) Single ﬁre (n=8) Repeated ﬁres (n=8) Tree cover (%) 90 ± 5,5 85 ± 29,7 80 ± 33,5 Bush cover (%) 5 ± 6,1 10 ± 5,9 20 ± 7,9 Grass cover (%)  8 ±13,6 14 ±22,7 33 ± 20,2 DBH of dominant trees (cm) 30 ± 0,3 25 ± 0,9 10 ± 0,5 9 ± 2,6 17 ± 23, 2 25 ± 19,8  Table 2: Environmental variables (mean ± SD) sampled at sites with dierent re frequency: Unburnt sites which did not burn in the last 30 yr; Single re: sites where re occurred once in 30 yr; Repeated res: sites where re occurred 3 - 4 times in the last 30 yr. DBH: Diameter at breast height.. Source: Moretti et al., 2004.Signicant traits in burned areas:  - Esclerotised cephalothorax (Langlands et al., 2011)- Open forest species -  Hunting speciesFigure 6:  species richness  with post re age in an arid zone (Australia). Source: Langlands et al., 201220222426283032343638400 3 5 10 20Species richness-Species richness with post-ﬁre age in years Post re age (years)

Effect of wildfire on spider communities in the world's forests

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Effect of wildfire on spider communities in the world's forests

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