DIGITALNA ARHIVA ŠUMARSKOG LISTA
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|ŠUMARSKI LIST 7-8/2015 str. 36 <-- 36 --> PDF|
Mycorrhizal macrofungi play an important role in plant physiological condition and help protecting their hosts from biotic and abiotic stress and pathogens. At the research area in Istria, western Croatia, pathogenic fungus Sphaeropsis sapinea (Fr.) Dyko et Sutton has caused substantial damage in Austrian pine (Pinus nigra J. F. Arnold) plantations through the last 25 years. During the previous research activities on predisposition to S. sapinea infections, site and stress conditions are determined as key factors. Back then, existing differences in fungal communities at disturbed and healthy Austrian pine plantations were observed. We hypothesized that Austrian pine plantations with higher ratio of ECM species and their sporocarps (minimum 40% of ECM species) are less susceptible to S. sapinea infection. It is the first research on linkage between ECM species and S. sapinea infection rate on Austrian pine needles.
Fungal samples were collected on three different permanent research plots of 400 m2 each, for three consecutive years (2011–2013) from week 36 to week 50, every fortnight. All samples were recorded with digital camera. Each fungal species and all its sporocarps on the plot represented one sample. They were collected in a wax paper bags, assigned and processed in laboratory on the same day. Sporocarps were counted and dried for 48 hours at 35–40 °C. Afterwards, they were packed in plastic bags and deposited to Croatian National Fungarium (CNF) for further identification. For all plots we analyzed soil samples and recorded soil profiles. Symptomatic branches and needles were taken from one tree per plot to analyze S. sapinea presence and number of pycnidia. Plantations were assigned, according to ECM fungi share, to different degrees of disturbance (latent, acute or lethal).
Soil analyses defined three different soil types: Tera Rossa (plot Mali Golji), Calcocambisol (plot Trstenik) and Eutric Cambisol on flysch (plot Previž) (Table 1.). In total, 2814 sporocarps (2288 ECM) and 88 species (47 ECM) were recorded, belonging to 37 genera. The maximum species richness was found at plot Trstenik (44 species) (Figure 1.), while the highest sporocarp richness was recorded at plot Previž (Figure 2.). Kruskal-Wallis test showed statistically significant difference between plot Previž and two other plots based on sporocarp number (H = 9,38, df = 2, p = 0,0092). Share of ECM species at plot Previž was 64,10% and 96,42% of sporocarps, respectively. Plot Mali Golji had the least share of ECM species (43,33%) and sporocarps (23,49%) (Figure 3.). S. sapinea pycnidia were not found at plot Previž, while at plot Mali Golji an average of 17,73 pycnidia per needle were recorded. On analyzed needles, together with S. sapinea, we found present Truncatella hartigii (Tubeuf) Steyaert. Kruskal-Wallis test showed statistically significant differences between all plots in term of pycnidia presence on pine needles (H = 121,5206, df = 2, p = 0,0000). Shares of ECM species and sporocarps were strongly related to an average number of S. sapinea pycnidia on a single needle. Regression trend indicate that in case when number of pycnidia on needles reaches 34 and more, we could expect an absence of ECM community (Figure 4.). An opposite scenario indicates that in case when share of ECM species reaches 74% or more, we could expect complete absence of pycnidia from needles. Similar trends were observed for sporocarps-pycnidia dependence (Figure 5.). Nevertheless, regression trends were not statistically significant (p<0,05). Correlations between average pycnidia number, share of ECM species and sporocarps in relation to potassium, nitrogen, carbon, C : N ratio and humus in organic soil layer are shown in Table 3.
Several ECM species with assumed mycobioindication value were recorded at plot Previž only, e. g. Tricholoma caligatum (Viv.) Ricken (Figure 6.), Suillus mediterraneensis Jacquet. & J. Blum) Redeuilh (Figure 7.), Hydnum albidum Peck, Hydnellum ferrugineum (Fr.) P. Karst., Phellodon niger (Fr.) P. Karst. (Figure 8.) and Cantharellus lutescens (Pers.) Fr. (Figure 9.) Characteristic ECM species at plot Trstenik were Clavulina cinerea (Bull.) J. Schröt., C. coralloides (L.) J. Schröt., C. rugosa (Bull.) J. Schröt., Inocybe bongardii (Weinm.) Quél., I. geophylla (Sowerby) P. Kumm., Ramaria gracilis (Pers.) Quél. and Russula chloroides (Krombh.) Bres. At plot Mali Golji, characteristic ECM species were Chroogomphus rutilus (Schaeff.) O.K. Mill., Lactarius atlanticus Bon, L. aurantiacus (Pers.) Gray and Russula delica Fr.
Acording to obtained results, plots Previž and Trstenik were characterized as not disturbed, while plot Mali Golji was at latent stage of disturbance. Considering a very low share of ECM sporocarps at plot Mali Golji, we predict a possible scenario of its transition to a more severe (acute) stage of disturbance. This research continues on previous research at the same Austrian pine plots on predisposition to S. sapinea infections, where site and stress conditions are determined as key factors. Our results confirm the assumption that stands with higher S. sapinea infection rate have impoverished mycorrhizal community and reveal potential indicator species of more resistant and healthy habitats. Since this research was focused on correlation between only two factors (share of ECM species and number of S. sapinea pycnidia on needles), we must interpret obtained results with precaution. To gain more reliable and precise results, further research based on higher number of plots and more detailed analysis of habitat factors is needed.
KEY WORDS: ectomycorrhiza, macrofungi, bioindicators, mycocoenosis, Austrian pine plantation