Arthropod biodiversity after forest fires: winners and losers in the

ECOGRAPHY 27: 173 /186, 2004

Arthropod biodiversity after forest fires: winners and losers in the winter fire regime of the southern Alps Marco Moretti, Martin K. Obrist and Peter Duelli

Moretti, M., Obrist, M. K. and Duelli, P. 2004. Arthropod biodiversity after forest fires: winners and losers in the winter fire regime of the southern Alps. / Ecography 27: 173 /186. Since prehistoric times, natural and man made fires have been important factors of natural disturbance in many forest ecosystems, like those on the southern slopes of the Alps. Their effect on scarce, endangered or stenotopic species and on the diversity of invertebrate species assemblages which depend on a mosaic of successional habitat stages, is controversially discussed. In southern Switzerland, in a region affected by regular winter fires, we investigated the effect of the fire frequency on a large spectrum of taxonomic groups. We focussed on total biodiversity, taxonomic groups specific to certain habitat types, and on scarce and endangered species. Overall species richness was significantly higher in plots with repeated fires than in the unburnt control sites. Plots with only one fire in the last 30 yr harboured intermediate species numbers. Fire frequency had a significantly positive effect on species richness of the guilds of interior forest species and forest edge specialists. Species of open landscape, open forests and interior forests were not influenced by fire frequency. A positive effect of fire on species richness was observed for ground beetles (Carabidae), hoverflies (Syrphidae), bees and wasps (Hymenoptera aculeata, without Formicidae), and spiders (Araneae). True bugs (Heteroptera), lacewings (Neuroptera) and the saproxylic beetle families Cerambycidae, Buprestidae and Lucanidae showed positive trends, but no statistically significant effects of fire on species numbers or/and abundances. Negative effects of fire on species numbers or/and abundances were found only for isopods and weevils (Curculionidae). A compromise for forest management is suggested, which considers the risk of damage by fire to people and goods, while avoiding the risk of damage to biodiversity by imitating the effects of sporadic fires and providing a mosaic forest with open gaps of different successional stages. M. Moretti ([email protected]), WSL Swiss Federal Research Inst., Sottostazione Sud delle Alpi, P.O. Box 57, CH-6504 Bellinzona, Switzerland. / M. K. Obrist and P. Duelli, WSL Swiss Federal Research Inst., CH-8903 Birmensdorf/ZH, Switzerland.

In many forest ecosystems of the world, wildfires represent one of the most important factors of natural disturbance (Pyne et al. 1996). This is also the case on the southern slope of the Alps (from south-east France to north-east Italy), where fires have contributed to changes in species composition of the forest vegetation since prehistoric times (Delarze et al. 1992, Hofmann et al. 1998, Tinner et al. 1999). Some authors underline that optimal habitat for fire intolerant species, or midand late successional species, would never develop under

a regime of frequent fires (e.g. Yanovsky and Kiselev 1996, Økland et al. 1996, York 2000), while other authors point out the importance of fire for invertebrates in creating a habitat mosaic of different successional stages (Buddle et al. 2000, Gandhi et al. 2001). Concerning biodiversity, some studies emphasise the positive role of fire as an important evolutionary force maintaining species richness according to the intermediate disturbance hypothesis, reducing exclusive competition and even favouring threatened species of invertebrates

Accepted 30 September 2003 Copyright # ECOGRAPHY 2004 ISSN 0906-7590 ECOGRAPHY 27:2 (2004)

173

(Bengtsson et al. 2000, Simila¨ et al. 2002, Sippola et al. 2002), while others consider fire as a negative factor which can endanger endemic and stenotopic species, and those with low dispersal capacity (e.g. Yanovsky and Kiselev 1996, Økland et al. 1996, Dajoz 2000). Reasons for the apparently contradictory effects of fire on invertebrates include the varying fire regimes, differing ecological pre- and post-fire conditions in the study regions, as well as the difference in the taxonomic groups in focus. More taxa should be concurrently included in future analyses, promising a better understanding of the complex ecological interactions, and minimising the risk of generalising statements, based on studies of only a limited number of taxonomic groups (Prodon et al. 1987). Moreover, the current knowledge on the effects of fire on invertebrates emanates from studies carried out in Mediterranean regions, or in fire-climax ecosystems such as savanna, chapparal, and boreal forests where fires occur in summer time (see Castri et al. 1981, Viegas and Andersen 1996, Andersen et al. 1998, DeBano et al. 1998, Trabaud 2000 for a review). Much less is known about the role of fire in temperate forests where winter fires predominate. The aim of this study is to investigate the response of a large spectrum of taxonomic groups to fire frequency in a temperate deciduous forest with a winter fire regime. The main questions are: 1) How is overall biodiversity affected by the fire frequency? 2) Which groups suffer and which profit from fire? 3) Does the abundance of ‘‘species of the forest interior’’ decrease after single or repeated fires? 4) Are scarce and endangered species threatened or furthered by fire? This research is part of a multi-disciplinary study on the effects of sporadic and regular wildfires on European chestnut forests (Castanea sativa Mill. ) in southern Switzerland (e.g. Delarze et al. 1992, Conedera et al. 1996, 2002, Tinner et al. 1999, Marxer 2002, Moretti et al. 2002a,b).

Materials and methods Study area and study sites The study area is situated in the hilly and mountainous belt of the southern Swiss Alps. The study sites were

chosen on a south-facing slope (450 /850 m a.s.l.) of 11 /15 km near Locarno (08844?E, 46809?N). The area was selected based on the presence of a sufficient number of burnt and unburnt surfaces to allow replication of sites. The study area has a moist, warm temperate climate, which differs from the more southern regions with a Mediterranean climate. Rainfall is higher in summer (June-September: ca 800 mm) than in winter (November-February: ca 400 mm). Thus the area is prone to fast-spreading surface fires during the period of vegetation dormancy (December /April). More details about the study area are given in (Moretti et al. 2002a).The forest cover at all sites is represented by former coppice stands of sweet chestnut Castanea sativa Miller. Chestnut was introduced in the region during Roman times and does not therefore represent the climax vegetation. Study sites were selected after consultation of the Wildfire Database of southern Switzerland, which contains data from 1968 to 1997 (Conedera et al. 1996). The sites were classified in three categories according to the number of fires (fire frequency) occurring in the last 30 yr, verified by dendrochronological methods. A total of 22 study sites were selected: 8 sites had burnt only once (single fire sites), 8 sites had burnt 3 /4 times (repeated fires sites) and 6 sites had never suffered from fire in the last 35 yr (control sites) (Table 1). The distribution of the time elapsed since the last fire amongst the two categories of fire frequency were equal, ranging from 0 yr (freshly burnt) to 24 yr (old fires) (Moretti et al. 2002a). Burnt and unburnt (defined as no fires during at least the last 35 yr) sites contrast strongly with respect to tree and grass cover, as well as to forest structure. Forest canopies were more open and the grass more luxuriant at burnt sites (especially at recently burnt sites) than at unburnt sites. Because of the resprouting of stools and the high shoot mortality following each fire, repeatedly burnt sites appeared more densely forested (average of 25 shoots per stool; 55% of shoots were dead) than unburnt and single fire sites (average of 9 shoot per stool; 22% of them dead). The dominant trees at repeatedly burnt sites were smaller (diameter at breast height, DBH 10 cm) than those of unburnt and single fire (DBH 30 cm). Table 2 summarises the most evident site characteristics.

Table 1. Study sites grouped in three classes of fire frequency (C/unburnt as control, i.e. sites which did not burn in the last 30 yr; S /single fire, i.e. 1 fire in the last 30 yr; R/repeated fires, i.e. 3 /4 fires in the last 30 yr) and 4 classes of time since last fire ( B/ 1, 1 /3, 6 /14, 17 /24 yr). Fire frequency

Unburnt (control) [C] Single fire [S] Repeated fires [R] Total trap sites

174

Unburnt

Time since last fire

Total

B/ 1 yr

1 /3 yr

6 /14 yr

17 /24 yr

1 1 2

2 2 4

2 4 6

3 1 4

6 6

6 8 8 22

ECOGRAPHY 27:2 (2004)

Table 2. Environmental variables (mean9/SD) sampled at sites with different fire frequency: [C] unburnt, control: sites which did not burn in the last 30 yr; [S] single fire: sites where fire occurred once in 30 yr; [R] repeated fires: sites where fire occurred 3 /4 times in the last 30 yr (n/number of study sites); DBH/diameter at breast height. Environmental variables

Tree cover (%) Bush cover (%) Grass cover (%) DBH of dominant trees (cm) Number of shoots per stool per Dead stools per shoot

Classes of fire frequency Unburnt [C] n /6

Single fire [S] n/8

Repeated fires [R] n/8

909/5.5 59/6.1 89/13.6 309/0.3 99/2.6 29/1.2

859/29.7 109/5.9 149/22.7 259/0.9 179/23.2 99/5.4

809/33.5 209/7.9 339/20.2 109/0.5 259/19.8 159/5.7

Sampling methods In order to obtain reproducible data, we used standardised collecting methods (Duelli et al. 1999). Litter dwelling species (e.g. isopods, spiders, carabids, other epigaeic beetles) were sampled using pitfall traps and surface eclectors. Pitfall traps consisted of plastic funnels recessed into the soil (opening diameter of 15 cm) and mounted on top of a plastic bottle containing 2% formaldehyde solution. A transparent roof 10 cm above the traps provided protection from the rain. For details and limitation of the method, see Obrist and Duelli (1996), Duelli et al. (1999) and Moretti et al. (2002a). Surface eclectors (emergence traps), developed by Brunhes (1981), consisted of a pyramid-like construction (50 /50 cm at the base) fixed on the ground and covered with a fine net (mesh widthB/0.5 mm) in order to preserve the microclimatic conditions. Emerging insects were trapped in collection vials on top of the dark pyramid, when they tried to escape to the light. Flying and flower visiting species were sampled using window traps in combination with a yellow water pan (Duelli et al. 1999) placed at a height of 1.5 m above ground. Window interception traps are widely used to study Coleoptera in forest ecosystems (e.g. Kaila et al. 1997, Schiegg 2001). According to Økland (1996) and Martikainen et al. (2000) they are suitable for comparing different forest environments and their ecological conditions over wide areas. The probability of an animal being caught by pitfall and window traps is a function both of the number of individuals present and their activity. This is not the case for surface eclectors, where the probability is not influenced by the animal’s activity. Thus the expression ‘‘number of individuals’’, includes both abundance and activity. Three sets of three traps (1 pitfall trap, 1 window trap, 1 eclector) were installed at each of the 22 study sites, making a total of 66 trap sites. The minimum distance between trap sites within each study site was at least 10 m, while the distance between the sample sites was ca 0.25 km. The traps were emptied weekly from the beginning of March to the end of September 1997, ECOGRAPHY 27:2 (2004)

resulting in a total of 28 sampling periods, which covered the main activity season for the different taxa.

Grouping the species Most of the invertebrates caught were identified to species level and grouped based on different criteria. Taxonomic groups / species were pooled in eleven systematic groups represented by one or more families of seven different orders (Table 3): Isopoda, Araneae, Coleoptera, Hymenoptera, Diptera, Neuroptera and Hemiptera. Habitat guilds / species were placed in four main groups depending on their habitat requirements: interior forest species (closed forest stands) (IF); open forest species (clearings, light forests, clear cuts) (OF); forest edge species (FE); open land species (fields, prairies) (OL). Ubiquist species, or species for which ecological knowledge is vague, were not classified. This grouping was mainly based on information obtained from published data (e.g. Stichel 1962, Kutter 1977, Hellrigl 1978, Aspo¨k et al. 1980, Koch 1989, Ro¨der 1990, Marggi 1992, Bense 1995, Ha¨nggi et al. 1995, Seifert 1996, Westrich 1989, Blo¨sch 2000, Duelli et al. 2002a) and from oral communications of those experts, who had identified the specimens (Table 4). Exclusive species / species that were sampled exclusively in one of the three categories of fire frequency (unburnt, single fire, repeated fires). Scarce species / due to the lack of published data on the relative abundance and rarity of the different species in Southern Switzerland, scarce species were defined for the study areas as those species sampled with less than five individuals. Threatened species / IUCN Red lists (Hilton-Taylor 2000) and analogous lists for Switzerland, Germany and Austria were used to define the prime species of conservation concern (Collins and Wells 1987, Speight 1989, Duelli 1994, Gepp 1994, Binot et al. 1998). Pyrophilous species / species that are known to be fostered by fire events. We considered the list reported by Wikars (1997). 175

Table 3. List of the taxonomic orders and groups considered. For each group a short description of the ecological niche and sampling methods is given. Order

Taxonomic group

Ecological niche

Sampling methods* PF

Isopoda Araneae Coleoptera

Isopoda (isopods) Araneae (spiders) Carabidae (ground beetles) Cerambycidae, Buprestidae, Lucanidae (long horn-, jewel- and stag beetles) Curculionidae (weevils)

remaining coleopteran families** Hymenoptera Formicidae (ants) Aculeata without Formicidae (bees, wasps) Diptera Syrphidae (hoverflies) Neuroptera Neuroptera (lacewings) Hemiptera Heteroptera (bugs)

WT

Saprophagous, epigaeic Zoophagous, epigaeic Mainly zoophagous, epigaeic Xylophagous at larval stage

x x x x

x x

Phytophagous, flying insects, epigaeic or on vegetation Flying or epigaeic insects, polyphagous Polyphagous, epigaeic Flying insects, predators and pollinophagous Flying insects, pollinophagous Flying insects, aphidophagous Flying insects and epigaeic, polyphagous

x

x

x x

x

x

SE x

x x x x

x x

x x x x

*PF /pitfall trap, WT/window trap, SE/surface eclector **Aderidae, Alleculidae, Anobiidae, Anthicidae, Anthribidae, Attelabidae, Bostrychidae, Byrrhidae, Byturidae, Cantharidae, Choleridae, Chrysomelidae, Ciidae, Cisidae, Cleridae, Coccinellidae, Colonidae, Colydiidae, Cryptophagidae, Cucujidae, Dasytidae, Dermestidae, Derodontidae, Drilidae, Elateridae, Endomychidae, Erotylidae, Eucnemidae, Lagriidae, Lampyridae, Lathridiidae, Leiodidae, Lymexylonidae, Melandryidae, Meloidae, Mordellidae, Mycetophagidae, Nitidulidae, Oedemeridae, Orthoperidae, Pselaphidae, Ptiliidae, Ptinidae, Rhipiphoridae, Rhizophagidae, Salpingidae, Scaphidiidae, Scarabaeidae, Scydmaenidae, Silphidae, Sphindidae, Tenebrionidae, Throscidae, Trogositidae.

Data analysis At a distance of 15 /40 m between traps, we do not expect any depletion of insects due to the traps. Therefore the number of specimens caught in the various trap sites were assumed to be independent of each other (Obrist and Duelli 1996) and were used as the sample units in the analysis. Using these data, the mean value (9/SD) of species richness and number of individuals

were calculated for each class of fire frequency. Analyses were performed on the overall data set and separately on the 12 different taxonomic groups representing different ecological niches and trophic levels. We analysed the mean number of species and of individuals (9/SD) per trap site with regard to the three classes of fire frequency (control, single and repeated fires) using ANOVA with subsequent Scheffe´ post-hoc tests. When the homogeneity of variances was not

Table 4. Total number of species (spp) and individuals (ind) of the 11 taxonomic groups analysed (Table 3), grouped into the four habitat guilds. Only the species with specific and well known environmental requirements were classified (IF/interior forest species, OF /open forest species, FE/forest edge species, OL/open land species). Taxonomic group

Total

Habitat guild IF

Isopoda Araneae Carabidae Curculionidae Cerambycidae, Buprestidae, Lucanidae remaining coleopteran families Formicidae Aculeata without Formicidae Syrphidae Neuroptera Heteroptera Total species Total individuals

176

spp ind spp ind spp ind spp ind spp ind spp ind spp ind spp ind spp ind spp ind spp ind

OF

Total IF-OF-FE-OL FE

OL

12 0 1 4 0 5 1.113 0 310 86 0 396 131 8 50 56 3 117 8.061 670 5.453 24 459 6.606 37 12 5 10 4 31 8.256 5.592 1.482 104 18 7.196 77 12 34 12 15 73 8.834 725 4.891 174 57 5.847 53 3 39 10 1 53 810 35 508 267 0 810 199 21 106 48 8 183 10.912 274 4.280 1.758 209 6.521 42 1 10 12 16 39 19.614 5.066 2.258 3.007 6.388 16.719 284 2 20 154 12 188 44.553 14 4.342 27.370 103 31.829 80 3 33 19 4 59 2.754 3 988 765 11 1.767 46 0 31 9 0 40 2.406 0 843 679 0 1.522 124 4 0 2 8 14 3.179 11 0 6 70 87 1085 66 329 336 71 802 110 482 12 390 25 355 34 240 7 315 79 300


achieved even after log-transformation of the data (Lilliefors test, Systat SPSS) non-parametric KruskalWallis ANOVA by ranks and Mann-Whitney U-test with Bonferroni correction between two groups was applied (Zar 1984). All analyses were performed using Systat 6.0 (Systat, SPSS). The influence of the fire frequency on species composition was tested by canonical correspondence analysis (ter Braak 1986) using the program CANOCO 4.0 (ter Braak and Smilauer 1998). ‘‘Geographical coordinates’’ were allocated as co-variables, in order to control for the geographical location of the sites (Legendre and Legendre 1998). Most variables related to forest structures shown in Table 2 were highly correlated with the fire frequency and were therefore excluded from the analysis to avoid redundancy. For this analysis, we considered only those species for which at least five individuals were sampled. The number of individuals was log(x/1)-transformed, in order to reduce the weight of very abundant species.

(Kruskal-Wallis test, n/66, p/ 0.039), but did not differ significantly from the control (no fire) after repeated fires. ‘‘Open forest species’’ and ‘‘open land species’’ did not show any significant effects after single or repeated fires. On the other hand, ‘‘forest edge species’’ increased with increasing fire frequency (Kruskal-Wallis test, n/66, pB/ 0.001) (Table 5). The same was true for ‘‘forest edge species’’ with regard to abundance: relative to the control, their numbers of individuals was increased due to the influence of fires (Kruskal-Wallis test, n/66, p/ 0.002) (Table 5). However, the overall number of individuals of both ‘‘interior forest species’’ and ‘‘open forest species’’ decreased significantly after the fire (Kruskal-Wallis test, n/66, pB/ 0.001 and p /0.008 respectively). This change in species composition was confirmed also by canonical correspondence analysis, which indicated that the overall change in species assemblage was highly correlated with the fire frequency (cor. coef. 0.941) which explained 11.5% of the overall species variance (p /0.005, Monte Carlo test) (Table 6).

Results Overall biodiversity after the fire A total of 1085 species were identified, reaching a total of 110 482 individuals (Table 4); 510 species (47%) were sampled with 4 or less individuals, while 284 species (26%) were observed exclusively at one sample site. The mean number of species per trap site was higher at repeatedly burnt sites, insignificantly lower at single burnt sites and significantly smaller at unburnt sites (Fig. 1). The overall number of individuals tended to decrease with the increase of the fire frequency, but the difference was not significant. Most of the species identified (802 of the 1085) could be attributed to four habitat types: the pooled samples included 66 (8.2%) interior forest species, 329 (41.0%) open forest species, 336 (41.9%) forest edge species, and 71 (8.9%) open land species. ‘‘Interior forest species’’ were affected negatively only at sites burnt once

Effects of fire on different taxonomic groups Species richness and number of individuals Figures 2a /d show that fire frequency affected distinct taxonomic groups differently. The species richness of 4 groups of the 11 investigated in this study increased at sites burnt repeatedly, similarly to the results of the overall biodiversity (Carabidae, Araneae, Syrphidae and Aculeata without Formicidae). On the other hand, species richness decreases in Curculionidae, Isopoda and Formicidae, the latter only at sites which had experienced a single fire. No significant differences were observed in several coleopteran families, Neuroptera, Heteroptera, and the complex of CerambycidaeBuprestidae-Lucanidae. With regard to the number of individuals, three taxonomic groups were negatively affected by fire (Formicidae, Isopoda, diverse coleopteran families),

Fig. 1. Overall biodiversity (species richness [N spp] and number of individuals [N ind]; mean per trap site [t.s.]9/SE) of the 11 different taxonomic groups pooled with regard to fire frequency (C/ unburnt, control; S/single fire sites; R/repeated fires sites). Bars with different letters are significantly different (p B/0.05; ANOVA with subsequent Scheffe´ post-hoc test).


177

Table 5. Effects of fire frequency on species richness (spp) and number of individuals (ind) (mean value per trap site/SD) of 4 habitat guilds of 11 taxonomic groups pooled for a total of 1085 species and 110 482 individuals. Differences among the three categories of fire frequency (horizontally) were tested using Kruskal-Wallis test. Pairwise comparisons were performed using MannWhitney U test by applying Bonferroni correction; values with different letters are significantly different in this test. Habitat guilds

Kruskal-Wallis test p

Categories of fire frequency Unburnt [C]

Interior forest species Open forest species Forest edge species Open land species

spp ind spp ind spp ind spp ind

0.039 B/0.001 n.s. 0.008 B/0.001 0.002 n.s. n.s.

while higher numbers of individuals were observed in Araneae at sites repeatedly burnt and in Syrphidae at sites burnt once. Numbers of individuals did not change significantly in any of the other groups. Species composition Canonical correspondence analysis showed that species composition of a majority of taxonomic groups (9 of 11) changed significantly after the fire (Table 6): Carabidae, Araneae, Aculeata, Formicidae, Isopoda, Cerambycidae-Buprestidae-Lucanidae, Neuroptera, Heteroptera and other Coleoptera families; only Curculionidae and Syrphidae did not change significantly. The correlation coefficients between ‘‘species assemblage’’ and ‘‘fire frequency’’ varied from 0.660 (Isopoda) to 0.953 (other Coleoptera), while the variance of the species assemblage explained by the fire frequency varied from 7.9% (Curculionidae; not significant) to 15.1% (Formicidae) (Table 6). The number of individuals of 29 species of which at least 50 individuals were sampled varied by at least a factor of 10 after the fire (Table 7). Three species were negatively affected by fire, while 26 species were favoured, 6 of which were sampled only at burnt sites. The effect of fire frequency on the species richness and on the number of individuals of different taxa grouped into the four habitat guilds was mostly similar to that of the overall biodiversity, except for ‘‘open forest species’’ of some groups (Table 8): the number of the ‘‘open forest species’’ of Araneae and Aculeata without Formicidae increased with the increase of fire frequency (KruskalWallis test, n/66, p/ 0.002 and p/ 0.005 respectively), while those of Formicidae decreased (KruskalWallis test, n/66, p / 0.003); the number of individuals

159/0.9 2799/45.3 579/1.7 6519/58.1 519/1.9 4499/35.4 69/0.5 809/29.8

Single fire [S] a 139/0.5 a 1229/25.7 a 609/1.8 a 4369/30.3 a 619/2.1 a 5549/58.5 a 79/0.8 a 559/47.9

Repeated fires [R] b b a b b b a a

149/0.6 1109/18.5 629/2.0 5259/51.9 649/3.8 5449/108.8 79/0.9 659/18.5

ab b a b c b a a

of the ‘‘open forest species’’ of ‘‘diverse Coleoptera families’’ decreased significantly after the fire (KruskallWallis test, n/66, pB/ 0.001 respectively).

Effects of fire on scarce, exclusive and/or threatened (red-listed) species The number of threatened species was higher at repeatedly burnt sites than in unburnt sites (Kruskal-Wallis test; n/66; 3.09/1.7 vs 5.09/4.4 species, p/ 0.041); the number of exclusive species was also higher at repeatedly burnt sites than at unburnt sites (Kruskal-Wallis test; n/66; 20.09/5.0 vs 25.09/5.8 species, p/ 0.043). The overall numbers of individuals did not change in these groups. The difference in numbers of scarce species after single and repeated fires was not significant. Concerning the group of species considered to be threatened in central Europe, 12.3 and 21.4% were sampled exclusively at singly and repeatedly burnt sites, respectively, while 10.8% were collected only at unburnt sites. We sampled 30 threatened species with /10 individuals, with a variation of at least a factor of 2 between unburnt and burnt sites (Table 9): 3 species were negatively affected by fire, 3 other species only by repeated fires, while the abundance of 24 species increased after fire (of these, 33% were open forest species; 42% forest edge species; 25% open land species). In addition to the above mentioned species, two pyrophilous species (Wikars 1997) were sampled exclusively at freshly burnt sites: 6 individuals of Aradus lugubris Falleń 1807 (Heteroptera) and 2 individuals of Sericoda quadripunctata (De Geer 1774) (Coleoptera: Carabidae).

Fig. 2. (a /d). Species richness and number (N spp) of individuals (N ind) (mean per trap site [t.s.]9/SE) of the 11 different taxonomic groups pooled with regard to fire frequency (C /unburnt, control; S/single fire sites; R/repeated fires sites). ANOVA with subsequent Scheffe´ post-hoc test). ANOVA with post-hoc Scheffe´ test was used when the homogeneity of variances achieved even log-transformation; in the other cases non-parametric Kruskal-Wallis ANOVA by ranks and Mann-Whitney U-test between two groups was applied. Bars with different letters are significantly different.

178



179

Table 6. Variance of the species composition explained by the ‘‘fire frequency’’ as environmental variable and by ‘‘geographical coordinates’’ as covariables. (‘‘Spp-Fire frequency’’ correlation/correlation between species assemblage and fire frequency; % var/percent of the variance of the species assemblage explained by the number of fires; p /probability of the Monte Carlo test implemented in the canonical correspondence analysis; */see Table 2). Taxonomic group

‘‘Spp-Fire frequency’’ correlation

% var

p

All taxonomic groups Carabidae Araneae Syrphidae Aculeata whithout Formicidae Curculionidae Isopoda Formicidae Cerambycidae, Buprestidae, Lucanidae Neuroptera Heteroptera remaining coleopteran families*

0.941 0.801 0.909 0.867 0.928 0.864 0.660 0.751 0.850 0.807 0.893 0.953

11.5 9.1 10.8 8.0 12.2 7.9 11.6 15.1 13.9 13.8 12.5 10.8

0.005 0.045 0.005 n.s. 0.005 n.s. 0.015 0.005 0.005 0.005 0.005 0.005

Discussion Overall biodiversity after the fire Many studies from boreal and tropical forests suggest that species richness, species composition and number of individuals of invertebrates change after fire (e.g. Sgardelis and Margaris 1993, Yanovsky and Kiselev 1996, Orgeas and Andersen 2001, Simila¨ et al. 2002), and that the direct impact of fire depends principally on the fire intensity (e.g. York 2000, Wikars 2001). According to several authors (e.g. Muona and Rutanen 1994, Buddle et al. 2000) most of the faunistic groups recover within a short time in fire-adapted ecosystems, where the number of species and individuals tends to be higher during the first few years after the fire compared to unburnt areas. This was confirmed by our studies of fast-spreading surface fires in winter time on the southern slope of the Swiss Alps, where repeated fires in particular seem to favour the overall species richness without significant influence on the number of individuals. Nevertheless, after repeated fires the shift of dominant numbers of individuals of ‘‘interior forest species’’ (/53.7%) to ‘‘forest edge species’’ (/29.5%) suggests that the current distribution and abundance of species, such as those of the forest interior, could have been historically limited first by fire, and later, up to the middle of the last century, by intensive forest management (Focarile 1987). The present species composition of invertebrates in the forests of the southern Alps seems to be the result of adaptation to disturbance.

Effects of fire on different taxonomic groups Fire affects the different layers (litter, herbs, shrubs and canopy) and taxonomic groups of the forest differentially (Prodon et al. 1987, Nunes et al. 2000 for a review). Our data show that fast spreading winter fires on the southern slope of the Alps affect litter-dwelling groups (Isopoda, Curculionidae, Formicidae, some families of 180

the Coleoptera) negatively. This was also observed by other authors in different forest ecosystems, such as boreal forests in Scandinavian or dry Eucalyptus forests in Australia (e.g. Sgardelis and Margaris 1993, York 1999, Nunes et al. 2000), and is probably due to the loss of litter and the lethal surface temperatures during the fire (up to 7008C; Marxer 2002). Ananthakrishnan (1996) suggested that structure, composition and the chemical and physical properties of the litter are important for the species assemblage of litter dwelling communities, which agrees with the low resilience of these communities observed by other authors (e.g. Huhta 1979, Prodon et al. 1987, York 1999, Nunes et al. 2000 for a review). Therefore, in the case of short intervals between fires (7 /10 yr in our study at sites repeatedly burnt), the litter hardly recovers, and conditions remain unstable. On the other hand, we observed a positive effect on epigaeic and mobile groups, in particular with Araneae and Carabidae. Many authors suggest that these groups, after having been reduced during the fire, increase quickly by profiting from abundant food in the postfire mosaic of ground habitats (Reed 1997, Dajoz 1998, Buddle et al. 2000, Moretti et al. 2002a). The post-fire conditions of herbs, shrubs and trees seem to favour heliophilous and floricol insects (e.g. Aculeata and Syrphidae). They profit from the reduced tree cover and the higher number of flowering plants, which resprout vigorously after the fire season (Moretti et al. 2002b). This is in contrast to Ne’eman et al. (2000) and Potts et al. (2001), who observed a negative effect of fire on flower-visiting insects in Israel, where fires occur in summer time when vegetation and insects are already active. Our results show that repeated fires influence the species composition of flying insects (e.g. Neuroptera, Heteroptera, Cerambycidae, Lucanidae and Buprestidae) favouring the mobile heliophilous and thermophilous species, but without affecting the number of species and individuals. This is partially in accordance with studies on similar phytophagous and wood-eating ECOGRAPHY 27:2 (2004)


181

b) Species favoured by fire

a) Species negatively affected by single and repeated fires

Species favoured by single and repeated fires

/ single fires

Species favoured by: / repeated fires

Exclusive species at burnt sites

Formicidae Heteroptera Coleoptera div. Formicidae Coleoptera div. Heteroptera Formicidae Cer-Bub-Luc Cer-Bub-Luc Formicidae Coleoptera div. Formicidae Aculeata Cer-Bub-Luc Formicidae Aculeata Araneae Aculeata Coleoptera div. Araneae Aculeata Cer-Bub-Luc Araneae Aculeata Heteroptera Aculeata Coleoptera div. Syrphidae Syrphidae

Kleidocerys resedae Enicmus minutus Formica pratensis Sciodrepoides watsoni Orius horvathi Formica sanguinea Chlorophorus figuratus Stenopterus rufus Myrmica ruginodis Oedemera flavipes Lasius psammophilus Hylaeus gibbus Leptura maculata Myrmica sabuleti Trypoxylon minus Micaria fulgens Pemphredon inornata Hoplia farinosa Zora spinimana Arachnospila spissa Agrilus angustulus Diplostyla concolor Lasioglossum rufitarse Dicyphus errans Hylaeus communis Corticaria ferruginea Xylota segnis Sphaerophoria scripta

Group

Leptothorax nylanderi

Species

13 12 4

5 10 4 5 3 3 6 1 1 4 2 2 5 3 1 9

4

565 69

3709

unburnt sites C (n/6)

274 233 51

36 49 52 35 17 16 15 16 4 6 3 15 110 68 59 586

70 2 5 18 76

68 7

1200

single fire S (n/8)

Fire frequency

292 148 48

396 183 127 102 104 98 81 58 52 46 48 33 10 21 10 894

46 5 68 56 109 154 75 61 1139

157

repeated fires R (n/8)

OF OF FE

OL OL FE OF FE FE OF FE FE OF ? OF FE OF ? FE

? U OL U ? FE FE FE OF

IF

Habitat guild

Table 7. Species more than 10 times as abundant a) in unburnt sites (C) as in single burnt sites (S) or in repeated burnt sites (R); b) in S or in R as in C. The table considers only the species for which at least 50 individuals were sampled. Habitat guilds: IF /interior forest species, OF /open forest species, FE/forest edge species, OL /open land species, U/ ubiquist, ?/unknown.

Table 8. Effects of fire frequency on species richness (spp) and number of individuals (ind) of 11 faunistic groups and of all taxonomic groups (Table 2) (Effect ‘‘/’’: the number of species or individuals increases significantly by increasing of fire frequency; ‘‘B/’’: the number decreases significantly; ‘‘ /’’: the variation is negligible). Significance of the effect of the fire frequency by Kruskal /Wallis test: * p B/0.05, ** pB/0.01, *** pB/0.001, n.s. not significant. Isopoda and Heteroptera do not appear, because the data set was too small. Taxonomic group

All groups Carabidae Araneae Syrphidae Aculeata without Formicidae Curculionidae Formicidae Remaining coleopteran families Neuroptera Cerambycidae, Buprestidae, Lucanidae

spp ind spp ind spp ind spp ind spp ind spp ind spp ind spp ind spp ind spp ind

Interior forest species

Open forest species

Forest edge species

Open land species

Effect

p

Effect

p

Effect

p

Effect

p

B/ B/ B/ / B/ B/ / / / / B/ B/ / B/ / / / / / /

* *** * n.s. * ** n.s. n.s. n.s. n.s. * *** n.s. *** n.s. n.s. n.s. n.s. n.s. n.s.

/ / / / / / / / / / / / B/ / / B/ / / / /

n.s. ** *** n.s. ** ** n.s. ** * n.s. n.s. n.s. ** n.s. n.s. *** n.s. n.s. n.s. n.s.

/ / / / / / / n.s. / / / / / / / / / / / /

** ** n.s. * *** ** ** n.s. ** ** n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. * *

/ / / / / / / / / / / / / / / / / / / /

n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s.

groups after disturbance (Barbalat and Ge´taz 1999, Golden and Crist 1999, Di Giulio Mu¨ller 2000).

Exclusive, scarce and threatened species Many authors (e.g. Goldammer et al. 1997, Bengtsson et al. 2000, Simila¨ et al. 2002) suggested that fire favours the biodiversity, not only by increasing the species richness, but also by favouring scarce and threatened species. Our data confirm that burnt and particularly repeatedly burnt sites host more scarce and endangered species than unburnt sites. Only Aphaenogaster subterranea (Latreille 1798) (a red-listed species in Switzerland) might be locally threatened by repeated fires, being a species that avoids open land and xeric conditions. This contrasts to the results of other authors (Springett 1976, Økland 1994, Yanovsky and Kiselev 1996, York 1998), which argue that fire can seriously threaten endangered, endemic, and other scarce species. From the list of threatened species found in our study it is clear that fire tends to favour species of forest edge habitats and of open land, which are nowadays endangered by forests closing in, and the intensive management and urbanisation of the open land close to the forest (Collins and Wells 1987, Speight 1989, Duelli 1994, Gepp 1994, Binot et al. 1998). The old-growth species and those intolerant to disturbance might already have disappeared from the southern slopes of the Alps a long time ago, as observed 182

in many forests in Europe (e.g. Speight 1989, Økland 1994, Schiegg 2001, Grove 2002). In our study sites, the presence of only 8 individuals of two pyrophilous species, both red list species in Switzerland, has to be considered as poor if compared to postfire data published from boreal forests (Wikars 1997, Dajoz 2000 for a review). Nevertheless, Wikars (1997) suggests that knowledge about pyrophilous species of southern Europe is very scarce. It is also likely that pyrophilous species related to winter fires differ from those of regions where fires occur in summer time. Better knowledge of the Mediterranean pyrophilous species and those related to winter fire regimes is therefore needed.

Implications for management and conservation Recently, the role of natural hazards such as windthrow, fire, landslides, as well as that of management such as clearing, logging, and thinning have been reinterpreted from the viewpoint of disturbance ecology, biodiversity, and species conservation (e.g. Wermelinger et al. 1995, Granstro¨m 1996, Goldammer et al. 1997, Barbalat 1998, Kirby and Watkins 1998, Duelli and Obrist 1999, Trabaud 2000, Bengtsson et al. 2000, Floren and Linsenmair 2001, White and Jentsch 2001, Wohlgemuth et al. 2002). The authors highlight the conservation value of the first stage of natural succession with large amounts of dead wood, even old growth forests, because this stage maintains a different species composition ECOGRAPHY 27:2 (2004)


183

c) Species favoured by fire

b) Species negatively affected by repeated fires

a) Species negatively affected by single and repeated fires

/ single fires Species favoured by fire

Species favoured by: / repeated fires

Exclusive species at burnt sites

Pediacus dermestoides Caenocara affinis Sympherobius klapaleki Aphaenogaster subterranea Andrena combinata Scotina celans Formica pratensis Calathus rubripes Tapinoma ambiguum Silpha carinata Formica sanguinea Chlorophorus figuratus Callimus angulatus Zelotes erebeus Xantochroa carniolica Dolichoderus quadripunctatus Enicmus atriceps Myrmica lonae Andrena curvungula Aradus lugubris* Ponera coarctata Sericoda quadripunctata* Lasioglossum pygmaeum Halictus subauratus Hylaeus difformis Callilepis nocturna Conopalpus testaceus Anthaxia funerula Diodesma subterranea Deilus fugax Lasioglossum minutulum Lasius meridionalis

Species

2 5 4 1 7 6 6 4 5 3 17 2 31 1 6 5 6 3 3 15 864 9

16 11 7 724 18 8

241 13 12 12 19 9 6 1 628 9

5 2 2 3 1 1 68 47 18 15 154 75 15 14 8 8 4 6 5 3 2

unburnt single repeated sites fire fires C (n/6) S (n/8) R (n/8)

Fire frequency

Coleoptera div. 42 Coleoptera div. 22 Neuroptera 15 Formicidae 744 Aculeata 14 Araneae 11 Formicidae Carabidae Formicidae Coleoptera div. Formicidae Cer-Bub-Luc Cer-Bub-Luc Araneae Coleoptera div. Formicidae Coleoptera div. Formicidae Aculeata Heteroptera Formicidae Carabidae Aculeata 41 Aculeata 1 Aculeata 1 Araneae 1 Coleoptera div. 3 Cer-Bub-Luc 1 Coleoptera div. 1 Cer-Bub-Luc 1 Aculeata 45 Formicidae 1

Group

OF OF OF FE FE FE OL OF OL FE FE FE OF FE OF OF OF FE FE ? OF ? OL OL FE OF OF OL OF FE FE OL

Habitat guild

Table 9. Threatened species in central Europe (red-listed in at least one of the following countries: Germany, Austria, Switzerland) more than twice as abundant a) in unburnt sites (C) as in single burnt sites (S) and in repeatedly burnt sites (R); b) in C and S as in R; c) in S and/or R as in C. The table considers only the species for which at least 10 individuals were sampled. Habitat guilds: IF/interior forest species, OF /open forest species, FE/forest edge species, OL/open land species, ?/unknown; */pyrophilous species (Wikars 1997).

compared to closed forests (Duelli et al. 2002b), including many threatened species of both early and late successional stages (Simila¨ et al. 2002, Sippola et al. 2002). The forests in fire-prone regions on the southern slope of the Alps consist of a mosaic of small burnt sites in different successional stages, alternating with large areas of intact forest. In fact, in the past 30 yr, only 10% of the gaps impacted by fires were /1.8 ha in southern Switzerland (Conedera et al. 1996). Similar conditions seem to be ideal for both saproxylic and non-saproxylic species, which profit from a large gradient of environmental and trophic conditions (Moretti et al. 2002a,b). Nowadays, fires in southern Switzerland are seen as a major threat to the natural succession of the chestnut forest towards mixed stands, to protection against erosion and, very importantly from a psychological and financial standpoint, to the life and property of local residents and tourists. Therefore, intensive and expensive measures are taken to prevent and fight fires under all circumstances. On the other hand, the long fire history of the deciduous forests on the southern slope of the Alps has led to an evolutionary process where natural and human-induced disturbances interacted for a long period if time. The result today is an adapted fauna with a varied spectrum of species which, to different extents, are negatively or positively influenced by sporadic or regular fires. Any attempt to prevent all fires would require a form of management in which dead wood is strictly removed, as in earlier times when harvesting chestnut timber was still profitable. Apart from creating enormous costs, such a procedure would threaten many fire adapted species, which depend on dead wood and favour open, sunny habitats (Simila¨ et al. 2002). Similarly, logging or clear-cutting of large areas, where all the wood is removed, has a negative impact on biodiversity and should be avoided (Speight 1989, Økland 1994, Grove 2002). Prescribed burns a measure to prevent fire cannot be proposed due to the high risk of erosion and landslide in the densely inhabited areas of the hilly region south of the Alps (Marxer et al. 1998, Providoli et al. 2002). After all, what can be done to minimize both, the damage to people created by fire and the damage to biodiversity created by preventing fires? We suggest a forest management which attempts to mimic frequent disturbance of low intensity in fire-prone locations, with short clear-cut rotations on small areas where part of the cut and dead wood is left. At the same time, old forest stands should be preserved, which provide optimal habitat for the less mobile and stenotopic species of the mid- and last successional stages (Gandhi et al. 2001). 184

A mosaic forest with temporary, small gaps of different successional stages can sustain a high biodiversity and at the same time allows for selective management in areas of high risk of fire. This asks for a supraregional coordination of forest management plans in the southern part of Switzerland. Acknowledgements / We would like to thank M. Zanini for helping in data analysis and M. Conedera for his comments on the manuscript. Many thanks are due to the various persons who helped in the fieldwork (P. Ho¨rdegen, P. Wirz, F. Fibbioli, K. Sigrist) and who identified or checked the species (F. Amiet, S. Barbalat, R. Ba¨rfuss, C. Besuchet, C. Germann, I. Giacalone, A. Ha¨nggi, X. Heer, P. Ho¨rdegen, O. Monga, P. Stucky, D. Wyniger, P. Zahradnik).

References Ananthakrishnan, T. N. 1996. Forest litter insect communities. / Science Publishers, Lebanon. Andersen, A. N. et al. 1998. Fire research for conservation management in tropical savannas: introducing the Kapalga fire experiment. / Aust. J. Ecol. 23: 95 /110. Aspo¨k, H., Aspo¨k, U. and Ho¨lzel, H. 1980. Die Neuropteren Europas. / Goeke and Evers. Barbalat, S. 1998. Importance of forest structures on four beetle families (Col.: Buprestidae, Cerambycidae, Lucanidae and phytophagous Scarabaeides) in the Areuse Gorges (Neuchaˆtel, Switzerland). / Rev. Suisse Zool. 105: 569 /580. Barbalat, S. and Ge´taz, D. 1999. Influence de la remise en exploitation de taillis-sous-futaie sur la faune entomologique. Schweizerische. / Z. fu¨r Forstwesen 150: 429 /436. Bengtsson, J. et al. 2000. Biodiversity, disturbance, ecosystem function and management of European forests. / For. Ecol. Manage. 132: 39 /50. Bense, U. 1995. Longhorn beetles. Illustrated key to the Cerambycidae and Vesperidae of Europe. / Margraf, Weikersheim. Binot, M. et al. 1998. Rote Liste gefa¨hrdeter Tiere Deutschlands. / Bundesamt fu¨r Naturschutz. Blo¨sch, M. 2000. Die Grabwespen Deutschlands: Lebenweise, Verhalten, Verbreitung. / Goecke and Evers. Brunhes, J. 1981. Caracte´ristiques et performances d’un pie`ges a` e´mergence destine´ a` l’e´tude des Insectes a` larves e´daphiques ou aquatiques. / L’Entomologiste 37: 126 /131. Buddle, C. M., Spence, J. R. and Langor, D. W. 2000. Succession of boreal forest spider assemblages following wildfire and harvesting. / Ecography 23: 424 /436. Castri, F. D., Godall, D. W. and Specht, R. L. 1981. Mediterranean type shrublands. / Elsevier. Collins, N. M. and Wells, S. M. 1987. Invertebrates in need of special protection in Europe. / Council of Europe of Strasburg. Conedera, M. et al. 1996. Incendi boschivi al Sud delle Alpi: passato, presente e possibili sviluppi futuri. Rapporto di lavoro PNR 31. / Hochschulverlag AG ETH of Zurich. Conedera, M., Moretti, M. and Tinner, W. 2002. Storia ed ecologia degli incendi boschivi al Sud delle Alpi della Svizzera. / In: Anfodillo, T. and Carraro, V. (eds), Atti del XXXIX corso di cultura in ecologia: Il fuoco in foresta: ecologia e controllo. Universita` degli studi di Padova, pp. 15 /30. Dajoz, R. 1998. Le feu et son influence sur les insectes forestiers. Mise au point bibliographique et pre´sentation de trois cas observe´s dans l’ouest des E´tas-Unis. / Bull. Soc. Entomol. France 103: 299 /312. Dajoz, R. 2000. Insects and forests. / Intercept Lavoisier Publishing. ECOGRAPHY 27:2 (2004)

DeBano, L. F., Neary, D. G. and Ffolliott, P. F. 1998. Fire’s effects on ecosystems. / Wiley. Delarze, R., Caldelari, D. and Hainnard, P. 1992. Effects of fire on forest dynamics in southern Switzerland. / J. Veg. Sci. 3: 55 /60. Di Giulio Mu¨ller, M. 2000. Insect diversity in agricultural grasslands: the effects of management and landscape structure. / Ph.D. thesis, Swiss federal institute of technology of Zurich. Duelli, P. 1994. Lista Rossa degli animali minacciati in Svizzera. / Ufficio federale per l’ambiente, la neve e il paesaggio a Berna. Duelli, P. and Obrist, M. K. 1999. Raümen oder belassen? Die Entwicklung der faunistischen Biodiversita¨t auf Windwurffla¨chen im schweizerischen Alpenraum. / Verhandlungen der Gesellschaft fu¨r Oekologie 29: 193 /200. Duelli, P., Obrist, M. K. and Schmatz, D. R. 1999. Biodiversity evaluation in agricultural landscapes: above-ground insects. / Agricult. Ecosyst. Environ. 74: 33 /64. Duelli, P., Obrist, M. K. and Fluckiger, P. F. 2002a. Forest edges are biodiversity hotspots /also for Neuroptera. / Acta Zool. Acad. Sci. Hungaricae 48: 75 /87. Duelli, P., Obrist, M. K. and Wermelinger, B. 2002b. Windthrow induces changes of faunistic biodiversity in alpine spruce forests. / For. Snow Landscape Res. 77: 117 /131. Floren, A. and Linsenmair, K. E. 2001. The influence of anthropogenic disturbances on the structure of arboreal arthropod communities. / Plant Ecol. 153: 153 /167. Focarile, A. 1987. I coleotteri del Ticino. / Memorie della Societa` ticinese di scienze naturali, Lugano. Gandhi, K. J. K. et al. 2001. Fire residuals as habitat reserves for epigaeic beetles (Coleoptera: Carabidae and Staphylinidae). / Biol. Conserv. 102: 131 /141. ¨ sterreichs. / Gepp, J. 1994. Rote Listen gefa¨hrdeter Tiere O Styria Medienservice. Goldammer, J. G., Page, H. and Pru¨ter, J. 1997. Feuereinsatz im Naturschutz in Mitteleuropa-Ein Positionspapier. / NNABerichte 10: 1 /11. Golden, D. M. and Crist, T. O. 1999. Experimental effects of habitat fragmentation on old-field canopy insects: community, guild and species responses. / Oecologia 118: 371 /380. Granstro¨m, A. 1996. Fire ecology in Sweden and future use of fire for maintaining biodiversity. / In: Goldammer, J. G. and Furyaev, V. V. (eds), Fire in ecosystems of boreal Eurasia. Kluwer, pp. 445 /452. Grove, S. J. 2002. The influence of forest management history on the integrity of the saproxylic beetle fauna in an Australian lowland tropical rainforest. / Biol. Conserv. 104: 149 /171. Ha¨nggi, A., Sto¨ckli, E. and Nentwig, W. 1995. Habitats of central European spiders. / Centre suisse de cartographie de la faune Neuchaˆtel. ¨ kologie und Brutpflanzen europaïscher Hellrigl, K. G. 1978. O Prachtka¨fer (Col., Buprestidae). / J. Appl. Entomol. 85: 167 /191. Hilton-Taylor, C. 2000. 2000 IUCN Red list of threatened species. / IUCN. Hofmann, C. et al. 1998. Effets des incendies de foreˆt sur la ve´ge´tation au Sud des Alpes suisses. / Mitteilungen der Eidgeno¨ssischen Forschungsanstalt fu¨r Wald, Schnee und Landschaft 73: 1 /90. Huhta, V. 1979. Evaluation of different similarity indices as measures of succession in arthropods communities of the forest floor after clear-cutting. / Oecologia 41: 11 /23. Kaila, L., Martikainen, P. and Punttila, P. 1997. Dead trees left in clear-cuts benefit saproxylic Coleoptera adapted to natural disturbances in boreal forest. / Biodiv. Conserv. 6: 1 /18. Kirby, K. J. and Watkins, C. 1998. The ecological history of european forests. / CAB International. ¨ kologie. / Goecke Koch, K. 1989. Die Ka¨fer Mitteleuropas-O and Evers. Kutter, H. 1977. Hymenoptera: Formicidae. / Schweizerischen Entomologischen Gesellschaft, Lausanne. ECOGRAPHY 27:2 (2004)

Legendre, P. and Legendre, L. 1998. Numerical ecology. / Elsevier. Marggi, W. A. 1992. Faunistik der Sandlaufka¨fer der Schweiz: (Cincindelidae and Carabidae.), Coleoptera, unter besonderer Beru¨cksichtigung der Roten Liste. / Centre suisse de cartographie de la fauna Neuchaˆtel. Martikainen, P. et al. 2000. Species richness of Coleoptera in mature managed and old-growth boreal forests in southern Finland. / Biol. Conserv. 94: 199 /209. Marxer, P. 2002. Einfluss von Waldbra¨nden auf Oberfla¨chenabfluss und Bodenerosion am Beispiel des Kastanienwaldgu¨rtels der schweizerischen Alpensu¨dseite. / Ph.D. thesis, Univ. of Basel, Basel. Marxer, P., Conedera, M. and Schaub, D. 1998. Postfire runoff and soil erosion in the sweet chestnut forests in south Switzerland. / In: Viegas, D. X. (ed.), III International Conference on Forest Fire Research and 14th Conference on Fire and Forest Meteorology. Vol. 2. ADAI Univ. of Coimbra, pp. 1317 /1331. Moretti, M. et al. 2002a. The effects of wildfire on groundactive spiders (Arthropoda: Araneae) in deciduous forests on the southern slope of the Alps. / J. Appl. Ecol. 39: 321 / 336. Moretti, M., Zanini, M. and Conedera, M. 2002b. Faunistic and floristic post-fire succession in southern Switzerland: an integrated analysis with regard to fire frequency and time since the last fire. / In: Wiegas, D. X. (ed.), Forest Fire Research and Wildland Fire Safety. Millpress, Rotterdam, CD-Rom. Muona, J. and Rutanen, I. 1994. The short-term impact of fire on the beetle fauna in boreal coniferous forest. / Ann. Zool. Fenn. 31: 109 /121. Ne’eman, G., Dafni, A. and Potts, S. G. 2000. The effect of fire on flower visitation rate and fruit set in four core-species in east Mediterranean scrubland. / Plant Ecol. 146: 97 /104. Nunes, L. F., Leather, S. R. and Rego, F. C. 2000. Effects of fire on insects and other invertebrates. A review with particular reference to fire indicator species. / Silva Lusitana 8: 15 /32. Obrist, M. K. and Duelli, P. 1996. Trapping efficiency of funneland cup-traps for epigeal arthropods. / Mitteilungen der Schweizerischen Entomol. Gesellschaft 69: 367 /369. Økland, B. 1994. Mycetophilidae (Diptera), an insect group vulnerable to forestry? A comparison of clearcut, managed and semi-natural spruce forests in southern Norway. / Biodiv. Conserv. 3: 68 /85. Økland, B. 1996. A comparison of three methods of trapping saproxylic beetles. / Eur. J. Entomol. 93: 195 /209. Økland, B. et al. 1996. What factors influence the diversity of saprolxylic beetles? A multiscaled study from a spruce forest in southern Norway. / Biodiv. Conserv. 5: 75 /100. Orgeas, J. and Andersen, A. N. 2001. Fire and biodiversity: responses of grass-layer beetles to experimental fire regimes in an Australian tropical savanna. / J. Appl. Ecol. 38: 49 / 62. Potts, S. G., Dafni, A. and Ne’eman, G. 2001. Pollination of a core flowering shrub species in Mediterranean phrygana: variation in pollinator diversity, abundance and effectiveness in response to fire. / Oikos 92: 71 /80. Prodon, R., Fons, R. and Athias-Binche, F. 1987. The impact of fire on animal communities in Mediterranean area. / In: Trabaud, L. (ed.), The role of fire in ecological systems. SPB Academic Publishing, pp. 121 /157. Providoli, I., Elsenbeer, H. and Conedera, M. 2002. Post-fire management and splash erosion in a chestnut coppice in southern Switzerland. / For. Ecol. Manage. 162: 219 /229. Pyne, S. J., Andrews, P. L. and Laven, R. D. 1996. Introduction to wildland fire. / Wiley. Reed, C. C. 1997. Response of prairie insects and other arthropods to prescription burns. / Nat. Areas J. 17: 380 / 385. Ro¨der, G. 1990. Biologie der Schwebfliegen Deutschlands (Diptera: Syrphidae). / Bauer, Keltern-Weiler.

185

Schiegg, K. 2001. Saproxylic insect diversity of beech: limbs are richer than trunks. / For. Ecol. Manage. 149: 295 /304. Seifert, B. 1996. Ameisen: beobachten, bestimmen. / Naturbuch. Sgardelis, S. P. and Margaris, N. S. 1993. Effects of fire on soil microarthropods of a phryganic ecosystem. / Pedobiologia 37: 83 /94. Simila¨, M. et al. 2002. Conservation of beetles in boreal pine forests: the effects of forest age and naturalness on species assemblages. / Biol. Conserv. 106: 19 /27. Sippola, A. L., Siitonen, J. and Punttila, P. 2002. Beetle diversity in timberline forests: a comparison between old-growth and regeneration areas in Finnish Lapland. / Ann. Zool. Fenn. 39: 69 /86. Speight, M. C. D. 1989. Saproxylic invertebrates and their conservation. / Council of Europe of Strasbourg. Springett, J. A. 1976. The effect of prescribed burning on the soil fauna and on litter decomposition in western Australian forests. / Aust. J. Ecol. 1: 77 /82. Stichel, W. 1962. Illustrierte Bestimmungstabellen der Wanzen. / Stichel. ter Braak, C. J. F. 1986. Canonical Correspondance analysis: a new eigenvector technique for multivariate direct gradient analysis. / Ecology 67: 1167 /1179. ter Braak, C. J. F. and Smilauer, P. 1998. Canoco 4. Reference manual and user’s guide to Canoco for Windows: software for Canonical Community Ordination (ver. 4). / Centre for Biometry of Wageningen. Tinner, W. et al. 1999. Long-term forest-fire ecology and dynamics in southern Switzerland. / J. Ecol. 87: 273 /289. Trabaud, L. 2000. Life and environment in the Mediterranean. / WIT Press. Viegas, D. X. and Andersen, A. N. 1996.. Fire ecology and management. - In: Finlayson, C. M. and Oertzen, V.I. (eds), Landscape and vegetation ecology of the Kakadu region. northern Australia. Kluwer, pp. 179 /195.

186

Wermelinger, B. et al. 1995. Die Entwicklung der Fauna auf Windwurffla¨chen mit und ohne Holzraümung. / Schweizerische Zeitschrift fu¨r Forstwesen 146: 913 /928. Westrich, P. 1989. Die Wildbienen Baden-Wu¨rttembergs. / Ulmer. White, P. S. and Jentsch, A. 2001. The search for generality in studies of disturbance and ecosystem dynamics. / In: Esser, K. et al. (eds), Progress in Botany. Vol. 62. Springer, pp. 399 /449. Wikars, L.-O. 1997. Effects of forest fire and the ecology of fireadapted insects. / Ph.D. thesis, Univ. of Uppsala. Wikars, L.-O. 2001. Immediate effects of fire-severity on soil invertebrates in cut and uncut pine forests. / For. Ecol. Manage. 141: 189 /200. Wohlgemuth, T. et al. 2002. Dominance reduction of species through disturbance /a proposed management principle for central Europe forests. / For. Ecol. Manage. 166: 1 /15. Yanovsky, V. M. and Kiselev, V. V. 1996. Response of the endemic insect fauna to fire damage. / In: Goldammer, J. G. (ed.), Fire in ecosystems of boreal Eurasia. Kluwer, pp. 409 / 413. York, A. 1998. Managing for biodiversity: what are the longterm implications of frequent fuel-reduction burning for the conservation of forest invertebrates? / In: Wiegas, D. X. (ed.), III International Conference on Forest Fire Research. ADAI Univ. of Coimbra, pp. 1435 /1445. York, A. 1999. Long-term effects of frequent low-intensity burning on the abundance of litter-dwelling invertebrates in coastal blackbutt forests of southeastern Australia. / J. Insect Conserv. 3: 191 /199. York, A. 2000. Long-term effects of frequent low-intensity burning on ant communities in coastal blackbutt forests of southeastern Australia. / Aust. J. 25: 83 /98. Zar, J. H. 1984. Biostatistical analysis.. / Prentice-Hall.
