Soil seed banks, plant diversity and grazing in deciduous oak forests of Greece

The role of grazing as a management practice, which could favor the conservation of high biodiversity levels in forest ecosystems, but also the regeneration of the herb layer, has not been studied in detail. Within the present doctoral thesis the following questions where investigated: • The composition of the above-ground vegetation under different grazing regimes • The composition and the abundance of the soil seed bank. • Comparison of the soil seed bank with the above-ground vegetation. • Assessment of the usefulness of the soil seed bank in restoration. • Monitoring of the above-ground vegetation changes, in time, focusing on the herb layer of the overgrazed forests. The study area is covered by extensive sub-Mediterranean mixed deciduous oak forests near Konitsa (Epirus), which undergo long-term overgrazing. The forests cover flysch and belong to the South Balkan association Verbasco glabrati-Quercetum frainetto. The soil seed bank of the study area is persistent and the seeds density reaches the levels of 2000 seeds/m². The long-term overgrazing and especially the wild boar grazing caused the qualitative and quantitative degradation of the soil seed bank. In the persistent soil seed bank 28 taxa were recorded, from which the dominant woody taxa and many typical forest taxa of the above-ground vegetation were absent. The long-term overgrazing reduced: a) the species richness (a-diversity) and b-diversity of the soil seed bank and of the above-ground vegetation, b) the similarity between the above-ground vegetation and the soil seed bank and c) the species richness and the seed density of the non-ruderal species, and especially the typical forest herbs, as well as of the animal-dispersed species. Monitoring the changes in the above-ground vegetation revealed that the continuously overgrazed forests are poorer in species while the sites under succession and the undisturbed sites are richer. The temporal turnover of species did not differ significantly between the successional and the sporadically grazed plots and was low in the overgrazed plots. The disturbance caused by overgrazing reduced plant diversity in time. By comparing of the spatial turnover with the temporal turnover of species the space for time substitution was found to be applicable in the studied ecosystem. The dissimilarity in species composition increases as the distance between two observations increases similarly to the case of distance decay. The studied forests have an 'ecological memory' which reflects grazing history. The relation between the above-ground vegetation and the soil seed bank is poor and the potential for restoration of the soil seed bank is limited. The persistent herb seed bank would be insufficient to restore the overgrazed forests after cessation of grazing; consequently, it should be used combined with other methods. The sporadically grazed forests maintain their structure, good regenerative ability and high plant diversity.Ο ρόλος της βόσκησης ως διαχειριστική πρακτική, που μπορεί να ευνοεί τη διατήρηση υψηλών επιπέδων βιοποικιλότητας σε δασικά οικοσυστήματα, αλλά και την αναγέννηση του ποώδους ορόφου δεν έχει μελετηθεί διεξοδικά. Στην παρούσα διδακτορική διατριβή ερευνήθηκαν τα ακόλουθα: • Η σύνθεση της υπέργειας βλάστησης υπό διαφορετικά καθεστώτα βόσκησης. • Η σύνθεση και η αφθονία της εδαφικής τράπεζας σπερμάτων. • Σύγκριση της εδαφικής τράπεζας σπερμάτων με την υπέργεια βλάστηση. • Αξιολόγηση της χρησιμότητας της εδαφικής τράπεζας σπερμάτων στην αποκατάσταση. • Παρακολούθηση των μεταβολών της υπέργειας βλάστησης, στο χρόνο, που υπόκεινται σε μεταβαλλόμενο καθεστώς υπερβόσκησης, δίνοντας βάρος στον ποώδη όροφο. Η περιοχή μελέτης αποτελείται από εκτεταμένα υπο-Μεσογειακά μικτά δάση φυλλοβόλων δρυών κοντά στην Κόνιτσα (Ήπειρος), που υφίστανται μακροχρόνια υπερβόσκηση. Τα δάση εδράζονται σε φλύσχη και εντάσσονται στη φυτοκοινωνική ένωση των Νότιων Βαλκανίων Verbasco glabrati-Quercetum frainetto. Η εδαφική τράπεζα των δασών της περιοχής μελέτης είναι μόνιμη και η πυκνότητα των σπερμάτων είναι της τάξης των 2000 σπερμάτων/m² . Η μακροχρόνια υπερβόσκηση και ειδικά η βόσκηση από αγριόχοιρους επέφερε την ποιοτική και ποσοτική υποβάθμιση της εδαφικής τράπεζας σπερμάτων. Στη μόνιμη εδαφική τράπεζα σπερμάτων καταγράφτηκαν 28 taxa, από τα οποία απουσιάζουν τα κυρίαρχα ξυλώδη taxa και πολλά δασικά είδη της υπέργειας βλάστησης. Με την επίδραση της μακροχρόνιας υπερβόσκησης μειώνεται: α) ο πλούτος ειδών (α-ποικιλότητα) και η β-ποικιλότητα της τράπεζας σπερμάτων και της υπέργειας βλάστησης, β) η ομοιότητα μεταξύ υπέργειας βλάστησης και εδαφικής τράπεζας σπερμάτων και γ) ο πλούτος ειδών και η πυκνότητα σπερμάτων των μη διαταραχόφιλων ειδών και ειδικά των τυπικών δασικών ποών, καθώς και των ζωόχωρων ειδών. Από την παρακολούθηση των μεταβολών της υπέργειας βλάστησης προέκυψε ότι, οι διαρκώς υπερβοσκημένες περιοχές είναι οι φτωχότερες σε είδη, ενώ οι περιοχές υπό διαδοχή και οι μη διαταραγμένες περιοχές είναι οι πλουσιότερες. Η χρονική μεταβολή των ειδών δε διέφερε σημαντικά μεταξύ των περιοχών της διαδοχής και των μη διαταραγμένων περιοχών και στις υπερβοσκημένες επιφάνειες ήταν μικρή. Η υπερβόσκηση ως διαταραχή μείωσε τη φυτική ποικιλότητα και διαχρονικά. Από τη σύγκριση της χωρικής με τη χρονική μεταβολή των ειδών προέκυψε ότι στο συγκεκριμένο οικοσύστημα εφαρμόζεται η υποκατάστατη του χώρου από το χρόνο. Η ανομοιότητα στη σύνθεση των ειδών αυξάνεται όσο αυξάνεται η απόσταση μεταξύ δύο παρατηρήσεων, όπως και στην περίπτωση της μείωσης της ομοιότητας με την απόσταση. Τα ερευνούμενα δάση διαθέτουν «οικολογική μνήμη» που αντανακλά το ιστορικό βόσκησης. Η σχέση της εδαφικής τράπεζας σπερμάτων με την υπέργεια βλάστηση είναι φτωχή και η δυναμική της τράπεζας σπερμάτων για αποκατάσταση είναι περιορισμένη. Μετά τη διακοπή της βόσκησης, η μόνιμη ποώδης τράπεζα σπερμάτων δε θα είναι επαρκής για αποκατάσταση του ποώδους ορόφου, επομένως πρέπει να χρησιμοποιηθούν και άλλες μέθοδοι συμπληρωματικά. Τα σποραδικά βοσκημένα δάση διατηρούν καλή κατάσταση στη δομή τους, καλή αναγεννητική ικανότητα και υψηλή φυτική ποικιλότητα

Topsoil Seed Bank as Feeding Ground for Farmland Birds: A Comparative Assessment in Agricultural Habitats

The topsoil seed bank was studied in four types of agricultural bird habitats: fields with cereals, maize, clover and tilled fields of a Mediterranean plain to determine the potentially richest habitat based on food supply for the wintering farmland birds. The diversity and abundance of topsoil seeds differed between seasons but did not differ significantly between habitats. The cereal habitat was the richest in food supply for the overwintering of farmland birds. The topsoil seed bank was dominated by Chenopodium album, Polygonum aviculare and Amaranthus retroflexus. The findings of this study provide insight for low-intensity management of higher-elevation mount agricultural areas of southern Mediterranean by preserving seed-rich habitats for farmland avifauna

Spatial analysis of orchids diversity unveils hot-spots: The case of Zante Island, Greece

The current study aims to analyze the ecological niche and mapping the distribution of species belonging to Orchidaceae family, in Zante Island and to determine hotspots at sites of high species richness. 967 observations were recorded into 110 tracks in 2015 and 120 tracks in 2016, where 47orchid species were identified belonging to 9 genera. Using Maxent, the ecological niche of each species was analyzed and habitat suitability map was created using 12 environmental parameters. The suitability maps were transformed into a binary format according to the threshold “10th percentile training presence” and the transformed maps used to compute hot-spot regions by applying the SMD toolbox using the software ArcGIS.Zante Island is characterized by remarkably high orchid species richness since the synthetic model indicates presence of at least 10 species for the 53.2% of the island area. Topography, geology and landscape openness are determining factors for orchids’ diversity conservation. Altitude is the determining factor of differentiation in species distribution. Hydro-lithology was the following most significant interpreting parameter. The mapping analysis of species abundance units revealed that 12.5% of the island surface could be characterized as hotspots of high value for the conservation of orchid diversity

Temporal shifts in floristic and avian diversity in Mediterranean pine forest ecosystems under different fire pressure: The island of Zakynthos as a case study

We evaluated how fire impacts the ecological coherence of Aleppo pine forests and their biodiversity over a 40-year period. The study area forms part of an insular ecosystem of Zakynthos Island (Zante) in western Greece, which forms part of the Ionian Islands. Post-fire effects were studied for both plant and bird diversity at 20 sampling plots, using stratified random sampling, during the summer of 2012. The plots were selected based on the frequency of burning since the 1970s. Sites were categorized as: 1) no burning for >40 years, 2) burnt once in the 1970s, 3) burnt twice, first in the 1970s and again in 2000–2010, 4) burnt three times, first in the 1970s, and twice more in 2000–2010, and 5) burnt four times, first in the1970s, twice more in 2000–2010, and again in 2011. A total of 79 plant species and 26 bird species were recorded at the studied sites. One-way ANOVA analysis showed that fire intensity has a significant impact on alpha floristic diversity. Average plant species richness at sites that burned in 2011 was significantly higher than in those that burned in the 1970s. Detected differences in bird species richness were not significant; however, more species were documented in the forested habitats (unburnt for >40 years, and burnt in the 1970s). The highest Jaccard similarity index was observed between the sites that had not burned for more than 40 years and the sites that burned in the 1970s. The lowest floristic similarity to non-burnt sites was observed between the recently burnt sites in 2011 and the sites that burned in the 1970s. The lowest bird similarity was detected between recently burnt sites in 2011 and sites that had not burned for more than 40 years. DCA ordination showed the presence of a clear fire gradient, from intensively burnt open sites to non-burnt forest sites. We suggest that fire is essential to maintain biodiversity in Aleppo pine forests, but only at intermediate frequency