DIGITALNA ARHIVA ŠUMARSKOG LISTA
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| ŠUMARSKI LIST 9-10/2010 str. 45 <-- 45 --> PDF |
L. Šerić Jelaska,A. Ješovnik, S. D. Jelaska,A. Pirnat, M. Kučinić, P. Durbešić: VARIATIONS OF CARABID ... Šumarski list br. 9–10, CXXXIV (2010), 475-486 DISCUSSION– Rasprava The relationship between habitat features and diversity of ants and carabid beetles was analyzed.We recorded great differences in carabid species composition and abundance among plots, where carabid abundance, but not the richness, was significantly higher in habitats with higher complexity scores.Brose (2003a) showed that an experimental reduction of vegetation complexity reduced the activity-abundance of large carabid species. Our results supports “enemy-free space hypothesis” (Lawton,1983) that prey species have more chances of escaping from natural enemies in dense vegetations. We found that large carabids prefer dense vegetation plots covered with leaf litter as enemy-free space. Furthermore, carabid species richness was negatively correlated with ant species richness.The results of ant richness analyses differ from those of Lassau and Hochuli (2004), but not those analyzing functional groups where they also found the largest abundance of opportunist species in low complexity sites. Stephens and Wagner (2006) have found that species richness, diversity, and dominance were a less satisfactory measure of various forest management impacts on ants than functional group analysis. The highest number of ant species (14) and abundance (1126 specimens) was recorded on plot 1, and the lowest number of the species and their abundance on plots 4 and 5. This result was in accordance with their habitat preferences.Ants in general, with excep tion of a few cold-temperate species, are thermophilic animals, and function poorly below 20 oC and not at all below 10 oC (Hölldobler and Wilson, 1994). Greater abundance and species number in lower altitudes can be explained, in addition to temperature, with precipitations, thickness and volume of leaf litter and available food resources (Brühl etal. 1999). The highest Shannon-Wiener index for carabid diversity (Table 5) was recorded on plot 5, situated in the Chrysanthemo macrophylli–Aceretum pseudoplatani forest, with high concentration of soil organic matter as a consequence of the longer persistence of snow-cover and hence higher soil humidity and a shorter micro-organism activity period.The herbaceous layer of this forest is characterized by nitrophilous plant species e.g. Lunaria rediviva L., Urtica dioicaL., Corydalis solida (L.) Swartz, etc.The impact of leaf litter origin on carabids has also been reported byNiemeläetal. (1992), Koivula etal. (1999) andMagura etal. (2005), in which the latter two authors observed significant impact of leaf litter on certain species e.g. Pterostichus oblongopunctatus and C. caraboides. In this study, both above mentioned species were found only on plots 4 and 5, which had the highest soil organic matter content. Soils in cooler climates commonly have more organic matter because of slower decomposition rate (BotandBenites2005). Table 5 Shannon-Wiener (H’) indices, numbers of equally common species (N) and Smith & Wilson evenness (S&W) for investigated plots Tablica 5.Shannon-Wiener (H’) indeksi raznolikosti, broj zajedničkih vrsta (N) te Smith & Wilson jednolikost (S&W) trčaka (carab.) i mrava (ants) na istraživanim plohama Plots / Indices 1 carab. ants 2 carab. ants 3 carab. ants 4 carab. ants 5 carab. ants 6 carab. ants H’ 3.049 2.262 2.724 2.585 2.951 2.074 3.201 0.366 3.711 0.977 3.625 1.936 N 8.27 4.80 6.61 6 7.73 4.21 9.19 1.29 13.10 1.97 12.34 3.83 S&W 0.138 0.26 0.153 0.39 0.128 0.322 0.291 0.22 0.182 0.293 0.218 0.295 On plots 1, 2 and 3, smaller number of species was recorded, while plots 4, 5 and 6 had a higher number of species with a low abundance, indicating less structured arthropods communities without dominant species. Also, cluster analyses of species composition on six plots divided carabids based on aspect and ants species based on elevation of investigated plots. Ant and carabid diversity and species body size distribution highly correlate with altitude and aspect (expressed as northness). On warmer, more south exposed plots (plots 1, 2 and 3) smaller number of carabid species was recorded. On the contrary, plots on northern slopes (plots 4, 5 and 6) had a higher number of species with a smaller number of specimens. Salgado et al. (1997) reported similar findings in their research of deciduous oak forests, where 10 of 42 species represented 90% of the total catch on five plots. They recorded a smaller number of species on plots with higher abundance of specimens and those with smaller abundance and larger number of species, the latter having unstable climatic conditions. In this study, plot 1, with recorded capture of 47.11% of the total catch, is situated at the lowest altitude with southern exposure, thereby ensuring more stable and warmer climate conditions that enable formation of ground beetle communities with the dominant and co-dominant species present (e.g. A. bombarda, A. parallelus, A. parallelepipedus, C. ullrichi, C. nemoralis, C. convexusandC. intricatus; Table 3). The highest number of carabid species, but the lowest abundance was recorded at the highest altitude (plot 4) with the lowest habitat complexity score. Flightless forest specialist such as C. caraboides that preferred higher |