Two similar types of trap stations were used for sampling Neuroptera, Raphidioptera, and Mecoptera. In the windthrow project in Alpine spruce forests each trap station consisted of a window trap and a yellow bucket trap (Fig. 1). The window trap intercepted flying insects with a vertical glass screen (80 cm × 50 cm) mounted 150 cm above ground with two lateral water troughs 80 cm long (Duelli et al. 1999). Some detergent was added to the water to make the insects drown quickly, and 2% Rocima GT (Acima, Buchs, Switzerland) was also added to prevent mold. The yellow bucket traps, 20 cm in diameter, attracted flower-visiting insects. They were also filled with water containing some traces of detergent and Rocima. For the three other projects a newer type of combined trap (further as combi-trap, Fig. 2) was used (Duelli et al. 1999). The combi-traps consisted of two sheets of Plexiglas (50 cm × 43 cm) crossed at right angles to provide independence of wind direction. To collect the insects, a yellow plastic funnel (43 cm diameter) was mounted below the screens, again at a height of 150 cm and filled with water and the same additives as above. A comparison between the performance of one window trap plus one yellow bucket vs. one combi-trap showed no statistically significant differences in species composition, richness and abundance (Gygax 1999).

Figure 1. 

Window interception trap and yellow bucket trap in an uncleared windthrow plot (Windthrow I) above Schwanden after storm Vivian. Photo: WSL.

Figure 2. 

Combi trap (a combination of a flight interception trap and a yellow funnel trap) in an uncleared windthrow plot (Windthrow II) near Habsburg after storm Lothar. Photo: WSL.

Trap numbers and sampling periods varied between projects, but were always identical among the three treatments within one project (see below). The traps were emptied weekly. The sampled material was stored in vials with 70% EtOH and sorted to taxonomic groups. The specimens of Neuropterida and Mecoptera were identified by the first author using the nomenclature of the lacewing digital library (Oswald 2017) and for Mecoptera Klausnitzer (2002).

Two projects investigated the impact of windthrow on the insect fauna: in the Northern Pre-Alps (Windthrow I), and on the Swiss Plateau (Windthrow II). Two other projects analyzed the impact of forest fire: one encompassed multiple fire on the southern slope of the Alps in Ticino (Forest Fire I), the other was a large wildfire in the inner-Alpine valley Valais (Forest Fire II). Table 1 shows the location of the different projects and trap sites.

Each of the four projects included three different treatments. Intact, undisturbed forests (FO) served as controls, heavily disturbed (HD) plots were plots with maximum disturbance, and intermediately disturbed (ID) plots were less severely disturbed. More detailed descriptions of the treatments are given below.

In early 1990 storm Vivian devastated mainly subalpine spruce forests in the Swiss Alps (Fig. 3). Near the village Schwanden at elevations around 1000 m three forest plots were used for a long-term investigation of different disturbance effects on biodiversity between cleared and uncleared windthrows. Like the disturbed plots, the control forest plot (FO) consisted of intact spruce forest with some scattered deciduous trees. The HD and ID plots had been equally affected by the storm but HD was cleared of all stems, suffering a double disturbance: windthrow and timber harvest (Fig. 4). In the ID plot the fallen trees remained untouched by harvest (Fig. 1). In the disturbed plots of 1–2 ha the vegetation cover developed slowly because of the high elevation. While in the cleared plot (HD) flowering herbs attracted pollinators and pollen feeders, the uncleared plot (ID) developed a brush vegetation of deciduous plants and young trees. The plots were sampled in 1992 (two years after the storm), 1993, 1994, 1996, 2000 and 2009. Three window traps and five yellow bucket traps were placed in each of the three plots (FO, ID, HD) at distances of at least 30 m between trap stations. The sampling periods lasted from mid May to end of September.

Figure 3. 

Large windthrow of storm Vivian in spruce forest in the Canton Glarus. Photo: WSL.

Figure 4. 

Cleared windthrow plot above Schwanden three years after storm Vivian (Windthrow I). Photo: WSL.

Ten years after storm Vivian, storm Lothar (late 1999) devastated even larger forest areas all over Europe. This time mainly deciduous forests in the Swiss Central Plateau were affected. Three areas, each with the three types of treatments (intact forest FO, cleared HD, and unsalvaged ID) were secured for long-term investigation. The plots in the region of Sarmenstorf (Fig. 2) represented beech forest (Fagus sylvatica L.), those at Messen were spruce forests (Picea abies (L.)), and those at Habsburg were mixed forest with half coniferous (mainly spruce) and half broad-leaved trees (Fig. 5). Within a region, the three treatments were located at distances from 100 m to three km apart to keep site conditions similar. In each of the nine plots three combi-traps were placed at distances of about 100 m from each other. A total of 27 combi-traps were operated between mid March to end of September in the years 2001, 2004, and 2010.

Figure 5. 

Cleared windthrow plot in mixed forest near Messen, two years after storm Lothar (Windthrow II). Photo: WSL.

The study area stretched over 15 km along a south-facing slope of the Swiss Alps at elevations between 450 m and 850 m a.s.l. in the region of Locarno. The former coppice stands of chestnut forest (Castanea sativa L.) on acidic soil is prone to forest fire, mainly fast spreading surface fires in late winter. Detailed records of the incidence of fires in that region (Conedera et al. 1996) allowed for a sampling design based on “space for time substitution” (Pickett 1989). Instead of sampling in different years after a fire, plots with different fire histories were sampled within one year (Moretti et al. 2006). In six sectors, 18 trap sites were chosen, each with a plot of only one fire for the previous 40 years (intermediately disturbed; ID), another with two to four fires in the previous 40 years (heavily disturbed; HD), and the third with no fire in at least 40 years (undisturbed forest; FO). All plots had similar site conditions. The same combi-traps (Fig. 6) as in windthrow project II (Lothar) were used (Moretti et al. 2006). Three traps were placed in each of the 54 plots. The minimum distance between traps at each site was ten m, while the average distance between the sites was around 300 m. The traps were emptied weekly from March to September 1997.

Figure 6. 

Combi trap in an intensely disturbed forest plot in Ticino (Forest fire I) after several forest fires within the previous 40 years. In spring the chestnut regrowth (here without old trees) is still without leaves. Photo: WSL.

On 13 August 2003, 300 ha of south-exposed forest at Leuk in the dry Central Alpine valley of the Valais fell victim to a large forest fire caused by intentional arson (Wohlgemuth et al. 2005). The burned area consisted of different forest types at elevations from 800m to 2100 m a.s.l. Three horizontal transects of six combi-traps were installed at elevations of 1200 m (mainly Pinus sylvestris L.), 1450 m (mixed forest with Picea abies and Pinus sylvestris), and 1700 m (mixed forest with Larix decidua Miller and Picea abies), ranging on both sides of the burned area from intact forest (FO) into the center of the burned area (HD, Fig. 7). The traps in the intermediately disturbed areas (ID) were installed on burned ground, but close (20–50 m) to the remaining forest edges. The 18 combi-traps (six at three altitudes) were emptied weekly from April to early September, starting in 2004 (first year after the fire) and continuing in 2005, 2006, 2008, and 2013. Details on regrowth of the vegetation at different locations and altitudes (Fig. 8) are given in Moser and Wohlgemuth (2006).

Figure 7. 

Combi trap in the center of the large burned area above Leuk, a few months after the fire (Forest fire II). Photo: WSL.

Figure 8. 

Two years after the massive fire above Leuk the whole area was covered with a carpet of colorful vegetation. Photo: WSL.

Natural impacts such as wildfires or windthrows cannot be planned or organized in space and time, because they happen sporadically and accidentally. Scientific investigations are therefore case studies rather than experiments with true replicates for statistical treatment. Replicates of either windthrow or forest fires take place in different years, show different coverage, or even occupy different regions. Since the projects were located at different elevations and in different regions of Switzerland, several species occurred only in a subsample of the projects. This heterogeneity prevented us from averaging numbers of specimens per treatment and from calculating variance. Also, the abundance of species changed with time after the impact, which cannot be considered as a variable in the present analysis because of the low numbers of specimens collected for most species. Furthermore, spatial autocorrelation of the trap sites (or plots) is a critical issue in unique events, but in the case of repeated space for time substitution (fire in Ticino) we accounted for it and minimized its effect by avoiding spatially structured sampling design (Moretti et al. 2010).

For each of the four projects, species lists were established. For each species the numbers of specimens collected per treatment (FO, ID, HD) were combined for all years. A species had to be caught at least five times in all four projects to be included in the analyses. Species collected in smaller numbers are listed in Appendix 1 for faunistic considerations only.

To quantify the positive or negative impact of disturbance on a species, the numbers were combined separately for the three treatments FO, ID, and HD for all four projects. The number of trap sites per treatment was balanced. As an indicator for the effect of disturbance in general, the following formula was used for each species: mean (HD+ID) / (mean (HD+ID) +FO). Species with more than 66% are considered winners, those with less than 33% losers.

Species rating in between are considered indifferent to the midterm effects of storms or fires.

Among the six top winners with 100% in disturbed plots were five green lacewing species. Two of these, Chrysopa formosa and C. pallens, are known to live in open habitats, on herbs or bushes (Aspöck et al. 1980). The three others, Nineta flava, Pseudomallada prasinus and P. ventralis, like almost all other winners among the Chrysopidae, are well-known forest edge species (Duelli et al. 2002a) or ubiquists (exemplified by Chrysoperla lucasina or C. carnea). Hypochrysa elegans, a pollen feeder in the adult stage, requires flowering plants for egg production. The arboreal Chrysoperla pallida and Nothochrysa fulviceps showed no clear preferences for disturbed habitats. Clear losers among the Chrysopidae were Peyerimhoffina gracilis, restricted to shady conifer forests, and Chrysotropia ciliata, mainly found in the Windthrow I project Lothar, which is known to live in moist forest habitats.

It was a surprise to see so many hemerobiid species ranking high up as winners after disturbances, because hemerobiids are known among neuropterologists to live mainly in the forest interior. However, Wesmaelius malladai, Micromus paganus, Megalomus hirtus and M. tortricoides, as well as the abundant Wesmaelius subnebulosus, can also be found in open habitats (Aspöck et al. 1980), and Micromus variegatus is even common in crop fields (McEwen et al. 2001). In forest edges, the Micromus species were labeled “herbaceous fringe” species (Duelli et al. 2002a), which is the lowest layer between forest edge and open habitat. Hemerobius lutescens and Drepanepteryx phalaenoides were considered “mantle-species.” Among the losers, the genus Sympherobius, represented by three small species, was dominant. A clear loser also was Hemerobius pini, again a specialist on conifers (Aspöck et al. 1980). More than half of the species of Hemerobiidae were not abundant enough to be treated here (see Appendix 1).

These tiny insects fly only within a small range when disturbed, but sometimes can swarm and move to other habitats in the morning. Parasemidalis fuscipennis, Coniopteryx esbenpeterseni, C. borealis, and C. tineiformis were found mostly in disturbed plots. The rather rare C. haematica and C. drammonti (both only Ticino), as well as the abundant Semidalis aleyrodiformis, showed no clear preferences for disturbed habitats. Losers were C. pygmaea, and especially Conwentzia psociformis.

Only two species of antlions were collected in sufficient numbers to be treated here, and both were favored by the effects of fire. Distoleon tetragrammicus, recorded only in the forest fire project II above Leuk, clearly favored ID plots. The species is known to develop in detritus between tree roots in warm forests (Aspöck et al. 1980). Myrmeleon formicarius, the most common antlion in Switzerland, was also collected only at Leuk, with nine specimens in the ID plots and three in the FO plots.

The two most abundant snake fly species were winners. The most positive impact of disturbance was shown in Phaeostigma notata, a “mantle species” in forest edges (Duelli et al 2002a). The larvae live under bark, where they feed on other arthropods, such as the larvae of bark beetles (Kenis et al. 2004). The larvae are most frequent under loose bark of dead tree trunks, thus favored by both types of disturbance. In the Lothar windthrow II and Leuk forest fire II projects they were most abundant in ID plots, and in the Vivian windthrow I they were most abundant in the cleared (HD) plot. Dichrostigma flavipes was caught only in the Leuk project, but in large numbers, mainly in the ID plots. The species develops in the soil in coniferous as well as deciduous forests (Aspöck et al. 1980). Puncha ratzeburgi, also a “mantle species” in forest edges (Duelli et al. 2002a), develops under bark of conifers and was collected in all three disturbance conditions of the Vivian and Leuk projects.

All four Panorpa species had more specimens in the disturbed plots, but only two were winners with more than 66%. Panorpa cognata, almost exclusively found in the Forest fire I project in Ticino, was about equally frequent in ID (24) and HD (22) plots, with only 2 specimens collected in the intact forest. Like all Panorpa species, P. cognata develops in the soil (Willmann 1989). Panorpa alpina was collected in surprisingly large numbers in the Lothar (Windthrow II) project, far from “alpine” regions. While most frequent in ID and HD plots in the Windthrow II project, the species was most frequent in the intact forest (FO) in the Windthrow I project. Panorpa communis, the most abundant species in this study, preferred ID plots after fire, whereas the numbers in the windthrow projects were highest in the HD plots. Panorpa germanica, not recorded in Ticino, benefitted least in overall numbers from the disturbances among the Mecoptera, but was consistently most abundant in the ID plots.