POLISH JOURNAL OF ECOLOGY (Pol. J. Ecol.)
61
3
545–560
2013
Regular research paper
Piotr SKUBAŁA*, Anna MARZEC Department of Ecology, University of Silesia, 40-007 Katowice, Bankowa 9, Poland *e-mail:
[email protected] (corresponding author)
IMPORTANCE OF DIFFERENT TYPES OF BEECH DEAD WOOD FOR SOIL MICROARTHROPOD FAUNA
ABSTRACT: Dead wood is an integral part of a forest ecosystem, numerously settled by soil microarthropods (Acari and Collembola), but these animals are rarely studied and often absent from publications dealing with this habitat. Five microarthropod groups in four different types of dead wood (log, stump, snag and tree hollow) and a forest floor were analysed. A core question was to determine the differences in the microarthropod communities, especially oribatid mites, between different types of beech dead wood. The study was carried out in the lowland acidophilus beech forest Luzulo pilosae-Fagetum association. Different types of beech dead wood prove to be a more favourable microhabitat for mites and collembolans than forest soil and litter. Oribatid mites of different dead wood microhabitats represent diverse and partly distinct sub-communities of mites in a forest ecosystem. Oribatid communities of beech dead wood were over 50% distinct. Most oribatid species appeared to be largely restricted to a certain type of beech dead wood. KEY WORDS: beech, dead wood, microar-
thropods, Oribatida
1. INTRODUCTION It is amazing that forest managers did not realize that dead wood was a critical habitat component for vertebrate and invertebrate
wildlife and for the forest itself (Thomas 2002). Today foresters are moving away from a “blanket” removal of all woody detritus to retaining and even enhancing the amounts of dead wood in forests. Dead wood has become an important focus of many scientific questions in the last decade (Har mon 2001). Nevertheless, in unmanaged European broadleaf forest, dead wood constitutes from 40 to 200 cubic meters per hectare and 5–30% of the total volume (D ud le y and Va l l aur i 2004), whereas only a low amount of dead wood – 1 to 3 m3 ha–1 is present in conventional forest managed systems in Central Europe (Jabin et al. 2004). Forest regulation in Poland requires at least 5 logs per hectare, but this regulation is non-obligatory requirements. As regards obligatory requirements, it is allowed to have 0.5 m3 of dead wood per hectare in spruce forests, 1 m3 ha–1 in other coniferous forests and 2 m3 ha–1 in deciduous forests (Manu a l of Forest Prote c t ion 2004). For European boreal and temperate forests, between 20–30 m3 ha–1 of dead wood or 3 to 8% of the total volume of wood could be suggested as a reasonable amount, divided between standing dead trees and down logs (D ud le y and Va l l aur i 2004). The habitat value of decaying wood has been recognized for many groups of animal
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species, including birds, small mammals, herpetofauna, insects and other invertebrates (Mas er and Trapp e 1984, Har mon et al. 1986, Samuelss on et al. 1994, Siitone n 2001). Many authors underlined that different types of standing and fallen wood in woodland are necessary to unsure wood decay communities (But ler et al. 2002). The habitat value of forest floor logs (Coarse Woody Debris – CWD) in particular has been recognized for many groups of animals (E lton 1966, Mas er et al. 1979, Har mon et al. 1986, Samuelss on et al. 1994, McMi n n and Crossle y 1996, Bu l l et al. 1997). As regards Acari and Collembola, the main groups of microarthropods, biodiversity and their functional role in a forest sub-system – different types of dead wood – are not sufficiently recognized. Mites (Acari) and springtails (Collembola) are numerously found in decomposing wood, but rarely studied and often absent from publications dealing with this habitat. Most abundant representatives of microarthropods are oribatid mites, which contribute greatly to organic decomposition, the synthesis of humus, the restitution of biogenic elements, and the stimulation of fungal and bacterial metabolism (Rus ek 1975, Cro ssl e y 1977, L ebr un 1979, Nor ton 1986). Most oribatid species ingest a wide range of food materials including spores of various fungal species, living and dead plant material, moss, lichens, conifer pollen and carrion (BehanPel let ier and Hi l l 1983). A few species feed directly on wood itself (Luxton 1972, Joh nston and Crossle y 1993). Information on microarthropods in CWD is scarce and ambiguous (Fage r 1968, S e aste dt et al. 1989, Johnston and Crossle y 1993, S et ä l ä and Marsha l l 1994, Skub ała and S okołowska 2006, Si i ra - Pi et i k äinen et al. 2008, Skub a ł a 2008, Skub ała and D uras 2008, Skub a ł a and Maśl a k 2009, D é chêne and Bu d d l e 2010). For long time decaying wood was recognized as a relatively poor substrate for microarthropods, especially in comparison with forest soil and litter. The fauna of decaying wood was considered a subset of the forest floor fauna with low number of mite species specific to this habitat (Fager 1968, S e aste dt et al. 1989, Johnston and C ro ss-
l e y 1993, Tr avé 2003). But recently several articles were published in which the picture of microarthropods (mainly oribatids) in dead wood changed. Higher abundance and species richness of oribatid mites in fallen logs than forest floor was observed (Skub a ł a and S okoł owska 2006, Skub ał a and D u r as 2008, Skub a ł a and Maśl a k 2009). Furthermore, some authors underlined that the proportion of unique oribatid species for decaying logs is high, even some dominant species appeared to be obligate members of decaying logs (Pe ntt i ne n et al. 2008, Si i ra- Pi et i käi nen et al. 2008, Skub a ł a and D u r as 2008, Skub a ł a and Maśl a k 2009, D é chê ne and Bu d d l e 2010). But all these papers deal with a certain type of dead wood, mainly decaying logs. In this paper, we compared the abundance of five microarthropod groups in four different types of dead wood and the forest floor of a beech forest. The species composition as well as the abundance of oribatid fauna was studied. More specifically we addressed the following hypotheses: (1) The abundance of Acari and Collembola and species richness differ significantly between different types of dead wood; (2) Dead wood is characterized by higher abundance of microarthropods and higher species richness than forest soil/litter; (3) The oribatid fauna in dead wood of Fagus sylvatica represents at least a partly distinct community when compared to that of the forest floor habitat; The practical implications of the results are assessed and discussed in the context of sustainable forestry. 2. MATERIAL AND METHODS 2.1. Study site The study site was located in the 159 ha „Parkowe” nature reserve in Złoty Potok that is situated in the north part of the Jura Krakowsko-Częstochowska (Silesian province, south Poland; 50°41’N, 19°25’E). The reserve was formally established in 1957, but cutting of trees had been halted and access restricted prior to the 2nd World War. The precipitation is moderately high (average 700 mm year–1) and average temperature is about 7.5oC. Elevation ranges from 230 to 423 m a.s.l. A beech forest of natural origin is
Microarthropod fauna in different types of beech dead wood
protected in the Reserve. Four different associations are dominant in the reserve: Dentario-enneaphyllidis-Fagetum, Carici-Fagetum, Luzulo pilosae-Fagetum and Melico-Fagetum. In general 13 plant associations are recognized in the reserve (C ab ała et al. 1999). The flora in the reserve is very rich with 387 vascular plants (20 protected species), 175 mosses (100 of which are endangered) and 385 fungi (of which 4 species are protected) (Here źni a k 2002). The investigation was carried out in the lowland acidophilus beech forest Luzulo pilosae-Fagetum association. The experimental site was 100 m2, facing north at 320 m elevation. Its woodland vegetation is dominated by beech (Fagus sylvatica) (about 150 years old) and fewer oak (Quercus petraea) trees. Maianthemum bifolium, Luzula pilosa, Oxalis acetosella and some mosses dominated in the field layer and ground layer. 2.2. Sample collection and sampling design Four different types of beech dead wood: fallen log, stump, snag (standing dead tree) and a tree hollow, were examined for woodinhabiting microarthropods. Different types of CWD (coarse wood debris) is characterized by the progression from undecayed state to a highly decayed state, which is not uniform (P y le and Brow n 1999). For example, a snag of a given decay class includes parts in a different classes of decay. We selected types of CWD, which represent the fifth class of decay (>85% of powdery wood) on P y l e and Brow n’s (1999) scale. Five samples of decaying wood (10–20 g of dry matter each) were taken randomly from each microhabitat at four seasons (2nd September 2005, 14th November 2005, 22nd February 2006 and 8th May 2006). Samples were taken each season from the same source. Dead wood samples were taken by pushing a metal soil corer (diameter 4.8 cm) to a depth of 5 cm into the dead wood. With regard to a tree hollow, dead wood material was sampled by hand. Five soil and litter samples were additionally collected from the homogenous site in the nearest surroundings of each of the dead wood types at each sampling date. Soil samples were taken using a corer of 4.8 cm diameter to a depth of 10 cm. Litter, humus and other organic layers
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formed at average 8.5–9 cm of the sampled layer. The number of dead wood and soil/litter samples were uneven, however, the total dry weight of the dead wood samples (1250 grams) and the soil/litter samples (1300 grams) were similar. The dead wood and soil were oven dried at 105oC for 24 h to calculate the dry weight. Abundance data of microarthropod groups was standardized by number of individuals per 100 grams dry weight (dwt). 2.3. Specimen identification and data analyses Mites and springtails were separated from wood, litter and soil using the Tullgren method. Samples were placed on an extractor for 6 days or until the wood was thoroughly dried. Extracted microarthropods were sorted into the following taxonomic groups: mites (Acari) and springtails (Collembola). Mites were related to four groups, namely order Mesostigmata, suborder Oribatida, suborder Prostigmata and cohort Astigmata (Kr ant z and Wa lte r 2009). Oribatid mites from all samples were separated into adults and juveniles (nymphs plus larvae). Because of difficulties in associating juvenile and adult oribatids, juveniles were counted but were not assigned to species. The classification proposed by Subi as (2004) was followed. The distribution of the oribatid species and the number of individuals collected in the different types of dead wood and the forest floor are listed in APPENDIX. Five univariate measures were used to assess community structure: abundance, species richness i.e. total number of species, species richness per sample, Shannon index of diversity (H’) and evenness (J). We tested for significant effects of a microhabitat type, and seasons on abundances of Oribatida, three other representatives of mites, Collembola and microarthropods in general by means of repeated-measures multiple analysis of variance (MANOVA) using Wilk’s lambda test statistic. Data were tested for homogeneity of variance by using the Levene’s test and log transformation was employed when the data did not meet the assumptions of normality. Microhabitat type was a main factor, the fauna groups were the multiple dependent variables
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and the season was taken as repeated measure. When the MANOVA was significant (P
