ACTA BIOLOGICA SLOVENICA LJUBLJANA 2003 Vol. 46, Št. 1 : 9 - 16 Sprejeto (accepted): 2003-10-30 Mycorrhizal potential of two forest research plots with respect to reduction of the emissions from the Thermal Power Plant Šoštanj Mikorizni potencial dveh gozdnih raziskovalnih ploskev po zmanjšanju emisij iz Termoelektrarne Šoštanj Samar AL SAYEGH PETKOVŠEK & 'Rojka KRAIGHER ERICo Velenje, Koroška 58, 3320 Velenje, Slovenia; E-mail: samar.petkovsek@erico.si 'Slovenian Forestry Institute, Večna pot 2, 1000 Ljubljana; Slovenia; E-mail: hojka.kraigher@gozdis.si Abstract. The mycorrhizal potential of two differently polluted forest research plots was determined in the emission area of the Thermal Power Plant Šoštanj. Zavodnje is the polluted, while Mislinja is the less polluted plot. Mycorrhizal potential of the soils from the two sites was estimated in a pot experiment. Types of ectomycorrhizae were identified in the soil cores and on short roots of N orway spruce seedlings. The fresh weight of needles and stems, number of short roots and the percentage of mycorrhizal short roots on seedlings from Zavodnje were significantly lower in comparison with Mislinja. The results indicate that the mycorrhizal potential of the more polluted site is lower. Mycorrhizal potential is discussed with respect to the results from our earlier studies. Key words: ectomycorrhizae, mycorrhizal potential, Norway spruce seedlings, forest research plots Izvleček. Določili smo mikorizni potencial dveh različno onesnaženih gozdnih ploskev v imisijskem območju Termoelektrarne Šoštanj. Zavodnje predstavlja onesnaženo, Mislinja pa manj onesnaženo raziskovalno ploskev. Mikorizni potencial obeh območij smo določili z lončnim poskusom. Tipe ektomikorize smo identificirali v talnih vzorcih raziskovalnih ploskev in na kratkih koreninah semenk smreke. Sveže teže iglic in stebel semenk (nadzemni del), število kratkih korenin in število nemikoriznih kratkih korenin semenk, ki so rastle na substratu iz Zavodenj, je statistično značilno manjše v primerjavi Mislinjo. Rezultati kažejo, da je mikorizni potencial bolj onesnaženega območja nižji. Mikorizni potencial smo primerjali z rezultati naših prejšnjih raziskav. Ključne besede: ektomikoriza, mikorizni potencial, semenke smreke, gozdna raziskovalna ploskev 10 Acta Biologica Slovenica, 46 (1), 2003 Introduction Ectomycorrhiza is the site of exchange of nutrients between the plant and the fungus. Fungal hyphae exploit the soil for mobilisation and absorption of water and nutrients (BRUNNER 2001). They are integral, functional parts of plant roots, in which the fungi involved provide a direct link between the soil and the roots (LEYVAL & al. 1997). Furthermore the mycelia of ectomycorrhizal fungi act as temporal and spatial connections between different species of trees in the forest ecosystem (AMARANTHUS & PERRY 1994). In the last decades damages of forest trees and ecosystems have been monitored in North America and Europe. These can be connected with the disturbances in the ectomycorrhizal symbiosis. The deposition of pollutants into the forest ecosystems leads to the acidification and/or eutrophication of the forest soil and can consequently affect the health and vitality of forest trees (BRUNNER 2001). The impact of pollution on forest soils can be estimated by determination of mycorrhizal potential of forest soil of differently polluted areas. Pollution can influence the below - ground diversity of ectomycorrhizal fungi since some types can better survive different stress factors than others (GIANINAZZI-PEARSON 1984, VODNIK & al. 1995, TAYLOR 1995). In Slovenia the mycobioindication method for determination of pollution stress has been used (KRAIGHER & al. 1996) and in spruce forest the reduction of biodiversity of types of ectomycorrhizae due to pollution was established (KRAIGHER 1999). On the other hand biodiversity indexes were high in all beech forest research plots, therefore the impacts of pollution on beech ectomycorrhizae was not stated (AL SA YEGH PETKOVŠEK & KRAIGHER 2000). In studies of oak decline KOVACS reported that the ectomycorrhizal diversity decreased slowly but significantly in two oak stands in the north-east of Austria and the presence of some morphotypes were highly correlated with the crown-status of the trees (KOVACS & al. 2000). The objectives of the present study were to determine mycorrhizal potential of two differently polluted forest research plots and to identify the types of ectomycorrhizae on short roots of mature trees and seedlings according to the concept of mycorrhizal succession (DIGHTON & MASON 1985, LAST & al. 1987) and biodiversity studies (KRAIGHER 1999, KOVACS & al. 2000, FERRIS & al. 2000). Material And Methods The mycorrhizal potential of forest soil is defined as the capability of propagules of naturally occurring fungi in forest soils to colonize roots of spruce seedlings. It is expressed as the percentage of mycorrhizal short roots of the total number of short roots in the sample (KROPAČEK & al. 1989). A modified method of a pot experiment for determination of the mycorrhizal potential was used (AL SAYEGH PETKOVŠEK 1997). Differently polluted research plots are situated in the emission area of the Thermal Power Plant Šoštanj (TPP) where the negative impact of pollution is well demonstrated in all parts of environment (SVETINA 1999, POKORNY 2000, KUGONIČ & STROPNIK 2001, RIBARIČ LASNIK & al. 2001, POKORNY & RIBARIČ LASNIK 2002). The two plots (850 m a.s.l., distric cambisol, Luzulo-Fagetum, predominant tree species Picea abies), were as similar regarding site characteristics as it was possible to select, but polluted differently by the emissions from the TPP, as indicated by the lichenological studies (BATIČ & KRALJ 1990) and by the total S% and Pb content in soil (Tab. 1, sampling done in August 2001). Soils from both plots were dug from the upper 20 cm, sieved (2 mm sieve) and used as planting substrates. At the same tirne types of ectomycorrhizae were identified in soil cores (275 ml volume, O - 18 cm deep) from both research plots. 5 seedlings (at 3 weeks of age) per pot and 5 pots per soil source were grown for six months in the gerrnination cabinet, where the growth conditions were the same for ali seedlings. After six months the seedlings were weighed, short roots were counted and the percentage of S. Al Sayegb Petkovšek, H. Kraiger: Mycorrbizal potential of two forest researcb plots ... 11 mycorrhizal short roots and the types of ectomycorrhizae were determined. The determination of types of ectomycorrhizae followed the procedure from the "Colour Atlas of Ectomycorrhizae" (AGERER 1987-1999) and other primary sources of identification. Data from the study in 1993 and 2002 were compared. The difference was in the reduction of the emissions from TPP: the reduction of the emissions from the Thermal Power Plant Šoštanj was from 86.147 t SO 2 in the year 1993 to 22.871 t in the year 2002. Statisticafor Windows 5.5 has been used for statistical analyses. The results represented in Graph 1 are the average values for seedlings from two different locations, the significance of the difference was evaluated by non-parametric statistical analyses (Man-Whitney U test). Table 1: Sieved soil analysis