Authors:K. Virágh, A. Horváth, S. Bartha, and I. Somodi
Conservation treatments often take place at the scale of vegetation stands and affect within-stand heterogeneity and coexistence patterns of species first. Therefore, it is important to capture changes in these characteristics of vegetation to assess response to treatments early. We propose a method based on Juhász-Nagy’s information theory models, which is capable of describing fine-scale spatial structure of plant communities and characterizes temporal processes as a function of spatial pattern. The proposed multiscale approach handles structural complexity and its dependence on spatial scales with the help of a few coenological descriptors and helps to reveal how fine-scale vegetation pattern affects dynamics. The information statistical functions used in our study (species combination diversity,
) characterize the scale-dependent variability of multispecies coexistence (structural complexity) and multispecies spatial dependence (the degree of spatial organization). The maxima of these functions and the related characteristic areas (plot sizes) can be used to construct an abstract coenostate space, where spatiotemporal processes (degradation, regeneration) can be followed. We demonstrate the usefulness of the proposed methods for detecting degradation and monitoring vegetation changes in different stands (18 seminatural and 13 slightly degraded stands) of
dominated wooded steppe meadows in Hungary. The information theory measures captured changes of fine-scale vegetation patterns that remained unexplored by species richness and Shannon diversity. The maximum values of information statistical measures and the related characteristic areas detected differences between seminatural and slightly degraded stands. In the coenostate space, seminatural stands appeared to be less variable compared to degraded ones. Seminatural stands from various geographic locations were less dispersed in this space, i.e., less heterogeneous than degraded ones. The two regions of the coenostate-space defined by the set of seminatural and degraded stands were significantly different. Furthermore, we conclude that the region containing seminatural stands can be regarded as a reference region in this abstract space. Temporal variation of seminatural and degraded stands was also clearly different. Therefore, we recommend the approach for exploring the actual dynamic states of vegetation stands to be treated and for following consequences of treatments in order to determine effectiveness of the conservation action.
Authors:S. Bartha, G. Campetella, E. Ruprecht, A. Kun, J. Házi, A. Horváth, K. Virágh, and Zs. Molnár
Decreasing diversity and plant cover, as well as increasing variability of these characteristics with increasing aridity are expected in grasslands due to climate change. These predictions were tested in perennial sand grasslands in Hungary. Two sites were chosen in different positions on an aridity gradient and two stands in each site were monitored for 9 years. Presence of plant species were recorded along 52 m long circular belt transects of 1040 units of 5 cm × 5 cm contiguous microquadrats. This sampling procedure — a version of line-intercept methods — enabled us to monitor diversity and total abundance in a sensitive, precise and non-destructive way. We found no trend but fluctuation in most community level attributes and in species composition. Contrary to fluctuations, between-site differences in diversity did not change and diversity remained lower in the more arid site during our 9-year-study. Compositional diversity performed better than species diversity because allowed us to detect vegetation changes that would have remained hidden if monitoring would be based only on the species richness. Comparing the magnitudes of fluctuations, five times higher relative interannual variability (CV%) was found for compositional diversity at the more arid site, while the relative temporal variability of total abundance and species richness did not show consistent patterns. We conclude that a 9 year-long study was too short to identify trends caused by the changing climate. However, the larger temporal variability of species combinations found in the more arid site suggests larger vulnerability and highlights the importance of non-linear dynamics during climate changes.
Authors:K. Halász, A. Geösel, J. Szarvas, N. Virágh, Cs. Hajdú, and N. Lukács
Mycoviruses are known to infect fungi of different habitats and life style. Some of them, like the Mushroom Virus X (MVX) complex, cause abnormal development of fruiting bodies and severe yield losses in mushroom cultivation. Most mycoviruses have a double-stranded RNA (dsRNA) genome, therefore dsRNA-detection is frequently used as a first step to identify virus infection. In relation with MVX 23 dsRNAs species have been described, occurring in variable number and combination in diseased mushrooms. The aim of our experiments was to find out whether dsRNA-immunoblotting can be used to detect dsRNA in small samples of cultivated A. bisporus varieties and of wild growing Agaricus species. We found that by immunoblotting, the same dsRNA species were detected in apparently healthy cultivated champignon fruiting bodies and in MVX-infected reference samples, respectively, as by conventional CF11 chromatography, but for immunoblotting a much smaller sample size was needed. In two out of three deformed fruit bodies of cultivated A. bisporus from Hungary we detected a 4.1 kbp dsRNA species which was also present in the MVX infected reference samples. Diverse and variable dsRNA patterns were observed in apparently healthy samples of 12 wild growing Agaricus species, indicating that extreme care should be taken when non-cultivated Agaricus is used for breeding new varieties. Non-sterile cultures and environmental mushroom specimens are fairly often mixed with parasitic and endofungal organisms, therefore, we also tested fungi isolated from mushroom cultures. Here again, 1–7 dsRNA species were found in extracts of Trichoderma and Dactylium isolates and of Mycogone-infected sporophores. Our results demonstrate clearly that dsRNAs from very different origins can be present in cultivated champignon and support the view that the MVX symptom-associated dsRNAs are probably of polyphyletic origin and do not represent one defined virus.