Research on conversion of coppice OAK forests in the region of Karditsa

Greece, as is the case with all European Mediterranean countries, is a predominantly oak forest country. The majority of these oak forests are coppice managed, resulting in their continuous deterioration. The importance of conversion of oak forests in Greece is immeasurable and is intertwined with the future role they will play in the economic and environmental sector, especially in the improvement and restoration of ecological stability, improving biodiversity, landscape aesthetics, soil protection, regulation and protection of water quality and quantity.The aim of this research is to investigate the conversion capability of degraded coppice oak forests in the region of Karditsa into high forests. The specific objectives are: the meticulous analysis of the current status of oak stands in the region, the identification of their degradation, structure and formation, based on qualitative and quantitative characteristics, the evaluation of their role and their rank in the process of conversion, so that they are converted into valuable ecological, multifunctional forests and finally, the identification of the silvicultural purpose, which combined with the evaluation of the current situation and their ecological capabilities, will lead to the proposal of an appropriate model of conversion from coppice forest into high forests.To investigate the structure of the oak stands 43 sample plots were installed, of an area of 500 m2, in the municipal forests of Kerasia, Morfovouni, Mesenikolas, Katafygio and in the state possessed forests of Lambero and St. Georgios, around Lake Plastira. In each plot, the altitude, slope and aspect were recorded and the breast height diameter (in cm), the height (in m) and the crown base height (CBH) (in m) of all the oak trees were measured, and each individual oak tree was classified under the IUFRO ranking system according to their vitality, stem quality and developmental tendency. To create the profiles and views of the oak stands, the coordinates of each oak tree x, y where 0 ≤ x ≤ 50 and 0 ≤ y ≤ 10 and the perpendicular diameters of their crown (dx, dy) to display the vertical projection of the crown to the ground, were measured additionally, in 8 sample plots. The sampling focused on clusters with the Hugarian Oak (Quercus conferta) as the dominant species. The site quality was evaluated with the use of polymorphic site index curves, based on the age and the maximum average height (average height of the 10 tallest trees/ha) of the stands and the use of the “toposequence” method. To estimate the biomass and the concentration of carbon and carbon dioxide, allometric equations were used. The distinction of the main forest functions and the definition of their respective criteria led to the mapping of the major forest types, by region, with the use of GIS.The coppice managed oak stands were classified in four site qualities (I,II,II,IV). The number of logs per hectare, of the 20 years old age group, of the coppice oak stands ranged from 2.420 - 3.993 depending on site quality. The average basal area of the coppice oak stands, of the 20 years old age group, ranged from 6,0-16,0 m2/ha depending on site quality. The vitality and developmental tendency were good in the site qualities Ι,ΙΙ,ΙΙΙ, and decreased by the worsening of the site quality. The trunk quality ranged from average to good even in the site qualities Ι,ΙΙ and ΙΙΙ.The distribution of the coppice stands’ diameters of the 20 years old age group, in all site qualities, was found to be in transition from the exponential (very young age, uneven structure) to the bell curve (normal distribution). The average diameter of the trunk of the 20 years old age group in the site quality I, was found to be 6,9 cm with a small percentage of oak trees displaying a diameter greater than 14 cm. The average breast height diameter (DBH) of the 20 years old age group in the site quality II, is 6,5 cm. In the same site quality, the average DBH of the 30 years old age group, was 7,9 cm, with many stems having thicker diameters up to 18 cm. The average DBH of the 20 years old age group in the site quality III, was found to be 6 cm, while in contrast to the site qualities I and II, only a few stems have a diameter thicker than 10 cm. The average DBH of the 20 years old age group in the site quality IV is 5,4 cm, with a maximum DBH of 10 cm. In the same site quality, the average DBH of the 50 years old age group is 9 cm, with a maximum at 18 cm.The average DBH of the 35 and 40 years old age group, was found to be equal to 12 cm and 12,5 cm respectively, with a significant number of stems having a diameter of 16 to 20 cm. The average DBH of the converted stands of the 45 years old age group, was found to reach 13,5 cm, with a significant number of stems belonging in classes of diameter of 16 to 26 cm. The distribution of heights of coppice stands, aged 20 years, suggests that the stands are evenaged, with only a few varied height classes. The average height of the coppice stands, aged 20 years, ranged from 5,6-7,3 m depending on site quality. The distribution of heights of converted stands, of the 35 and 40 years old age group showed that they consist of more height classes than the coppice stands. The average height of the converted stands, aged 30 and 45 years, ranged from 11,2-14m, and was double compared to that of the coppice stands.The representation of the profiles and views of the oak stands showed that the canopy cover is dense, leading the branches of the crown of a tree to enter into the crowns of neighboring trees, resulting to their mutual disfigurement. A result of a compact canopy closure is not enough light reaching the forest floor for the development of distinct shrub floor and ground layer vegetation.Based on the allometric models the average concentration of carbon per hectare of living woody biomass of the converted stands (mean age = 35 years) (59 t/ha) was estimated to be almost double compared to that of the coppice stands (31 t/ha). The respective concentration per log of the converted stands (41 kg/log) was found to be multiple compared to that of the coppice stands (7 kg/log).The aboveground woody biomass for the entirety of the sample plots showed no significant variation between the three allometric models that were used.The strongest statistical models generated by the simple regression, were those with the aboveground woody biomass as the dependent variable and the volume and basal area as the independent variables (R2=0,90, p<0.01 and R2=0,97, p<0.01 respectively).The spatial representation and analysis of forest functions can constitute the base of forest planning. An effort of mapping the basic forest types according to their appointed primary function was made using GIS. Thus, coppice oak stands were classified as protective (forests of general protective role, forests that protect infrastructure, riparian forests with hydronomic function), aesthetic and productive. The forests of general protective role were estimated to occupy an area of approximately 675 ha, which equates to 26,52% of the total area of coppice oak forests, in all of the surveyed areas. The forests that protect infrastructure (primary road network and settlements) occupy an area of approximately 24 ha (1,33%) and the riparian forests with hydronomic function occupy an area of 352 ha (13,83%). The total area of protective forests were estimated at approximately 942 ha which equates to 37% of the total area covered by coppice oak forests in all of the surveyed areas. The aesthetic forests were estimated to occupy an area of approximately 1417 ha (56%) and the productive forests 693 ha (27,3%).The current state of the stands and the forest categories, according to their primary function, constituted the basis for the creation of management scenarios and the final definition of management models and silvicultural planning. Thus, three management scenarios arose. Scenario A1 (optimistic) involves the conversion of the total area of the coppice oak forest and dense evergreen-sclerophyllous shrubs that occur in an altitude higher than 500m (2.682,48 ha), taking into account that the growing stoke will mount to 300 m3/ha. According to this scenario, the concentration of carbon for the entire area that will be reduced will reach approximately 385.000 tons, which corresponds to the capture of carbon dioxide equal to approximately 1.412.000 tons. Scenario Α2 (moderate) involves the conversion of the total area of aesthetic forests of all the surveyed areas (1.417,16 ha), assuming that the growing stoke will reach 200 m3/ha. According to this scenario the concentration of carbon will reach approximately 141.000 tons (517.541 tons carbon dioxide). Scenario Α3 (pessimistic) involves only the conversion of protective forests of the total surveyed area (942,38 ha), considering that the average growing stock will reach 100 m3/ha. According to this scenario, the total concentration of carbon will reach approximately 50.228 tons (184.171 tons of carbon dioxide).The mapping of forest types did not lead to completely different management models, since the general framework of conversion is proposed in each category, but in some limited degree modification of individual actions, depending on each appointed primary function. The general framework of the proposed conversion is the extension of the rotation length to 120 years, with the prerequisite of lifting deterioration factors, such as illegal logging and grazing. The conversion is proposed to be implemented primarily in stands of good site qualities (Ι,ΙΙ,ΙΙΙ). In good site qualities conversion is proposed to be implemented with tending by positive selection cutting, to favor the prospective individual logs by removing their most acute competitor. The conversion is proposed to start at age 10 or earlier or at age 20 at the latest. The thinning is proposed to be applied up to 20% in good site qualities and up to 15% in bad. The favoring of the Fir, and deciduous shrubs occurring in the area, constitutes a factor of particular importance. In the IV site quality, the natural method of restoration is proposed. In steep slopes of the IV site qualities, where soil erosion occurs, the artificial method of conversion can be implemented with the introduction of the Hybridogenous Fir (Abies borisii-regis) up to 20-40%, at the higher altitudes where Fir occurs naturally.Regarding the silvicultural treatments of protective forests, particular attention should be given in the reduction of disruptions and soil compaction, and in the handling of logging residues, by placing them alongside the contours to prevent erosion. In the treatment of aesthetic forests, particular attention should be given in potential artificial introduction of Fir (Abies), which in this particular case is proposed to be of a very limited scope, to avoid disturbance of the ecological niches, which would cause unpredictable consequences in the biodiversity, in the non-removal of logging residues, which contribute to the increase of complexity and in creating and maintaining clearances. In productive forests, in addition to the vitality, the quality of the trunk and the crown of the prospective log should be taken into consideration. Furthermore, in this particular case, the carrying out of negative selection is required, but in a limited degree and always within the framework of the conversion, for the removal of silviculturaly undesirable trees. In the evergreen-sclerophyllous shrublands (Maquis), the natural recovery process is proposed, letting those ecosystems in their natural evolution, with the necessary prerequisite of grazing management and the removal of all degrading factors.Σκοπό της παρούσας έρευνας αποτελεί η διερεύνηση της δυνατότητας αναγωγής των υποβαθμισμένων δρυοδασών, πρεμνοφυούς μορφής, της περιοχής Ν. Καρδίτσας, σε υψηλά σπερμοφυή. Οι επιμέρους στόχοι είναι η σχολαστική ανάλυση της υφιστάμενης κατάστασης των συστάδων Δρυός της περιοχής, ο προσδιορισμός της υποβάθμισης, της δομής και της διάρθρωσής τους, βάσει ποιοτικών και ποσοτικών χαρακτηριστικών, η αξιολόγηση του ρόλου τους και η ιεράρχησή τους στην αναγωγική διαδικασία, έτσι ώστε να αναχθούν σε, πολύτιμα οικολογικά, πολυλειτουργικά δάση και τέλος ο προσδιορισμός του δασοκομικού σκοπού, που σε συνδυασμό με την αξιολόγηση της υφιστάμενης κατάστασης, αλλά και των οικολογικών δυνατοτήτων, θα οδηγήσει στην πρόταση του κατάλληλου μοντέλου αναγωγής τους από την πρεμνοφυή στην υψηλή σπερμοφυή μορφή. Για τη διερεύνηση της δομής λήφθηκαν 43 δειγματοληπτικές επιφάνειες, εμβαδού 0,5 στρ. στα δημοτικά δάση Κερασιάς, Μορφοβουνίου, Μεσενικόλα, Καταφυγίου και στα διακατεχόμενα δάση Λαμπερού και Αγίου Γεωργίου, περιμετρικά της λίμνης Ν. Πλαστήρα. Σε κάθε επιφάνεια πραγματοποιήθηκε μέτρηση στηθιαίας διαμέτρου κορμού (σε cm) κάθε ατόμου Δρυός, μέτρηση του ύψους (σε m), μέτρηση του ύψους έναρξης κόμης (σε m) κατάταξη των ατόμων, βάσει του συστήματος κατάταξης ΙUFRO, σε τάξεις ζωτικότητας, ποιότητας κορμού και κοινωνικής εξέλιξης, καταγραφή υψομέτρου, κλίσης εδάφους και έκθεσης. Για τη δημιουργία των προφίλ και των όψεων συστάδων, σε 8 δειγματοληπτικές επιφάνειες μετρήθηκαν επιπλέον oι συντεταγμένες θέσης του κάθε ατόμου x,y όπου 0≤x≤50 και 0≤y≤10 και δύο κάθετες μεταξύ τους διαμέτροι κόμης (dx,dy), για την απεικόνιση της κάθετης προβολής της κόμης στο έδαφος. Η δειγματοληψία επικεντρώθηκε σε συστάδες με κυρίαρχο είδος την πλατύφυλλη Δρυ (Quercus conferta). Η διάκριση των ποιοτήτων τόπου πραγματοποιήθηκε με τη χρήση σταθμοδεικτικών καμπυλών, βάσει της ηλικίας των συστάδων και του μέσου ανώτερου ύψους αυτών (μέσο ύψος των 10 υψηλότερων ατόμων/στρ.) και με τη μέθοδο της «τοποδιαδοχής». Για την εκτίμηση της βιομάζας, της συγκέντρωσης του άνθρακα και του διοξειδίου του άνθρακα χρησιμοποιήθηκαν αλλομετρικές εξισώσεις. Η διάκριση των κύριων δασικών λειτουργιών και ο καθορισμός των αντίστοιχων κριτηρίων οδήγησε στη χαρτογράφηση των κύριων δασικών κατηγοριών, ανά περιοχή, βάσει των γεωγραφικών συστημάτων πληροφοριών. Από τα αποτελέσματα φαίνεται ότι στις συστάδες Δρυός που διαχειρίζεται πρεμνοφυώς, διακρίθηκαν τέσσερις ποιότητες τόπου (I,II,II,IV). Η κατανομή των διαμέτρων των πρεμνοφυών συστάδων, σε όλες τις ποιότητες τόπου και στην κλάση ηλικίας των 20 ετών, βρέθηκε ότι είναι στο μεταβατικό στάδιο από την εκθετική (πολύ νεαρή ηλικία, ανομοιόμορφη δομή) στην κωδωνοειδή καμπύλη (κανονική κατανομή). Η κατανομή των υψών των πρεμνοφυών συστάδων, ηλικίας 20 ετών, υποδηλώνει ότι οι συστάδες είναι μονόροφες, με ελάχιστες κλάσεις ύψους. Από την απεικόνιση του προφίλ και της κάτοψης των πρεμνοφυών συστάδων προέκυψε ότι η συγκόμωση είναι σύμπυκνη, δηλαδή τα κλαδιά της κόμης του ενός ατόμου να εισέρχονται στις κόμες των γειτονικών ατόμων, με αποτέλεσμα την αμοιβαία παραμόρφωση τους. Αποτέλεσμα της σύμπυκνης συγκόμωσης είναι να μην φθάνει στο έδαφος αρκετό φως για την ανάπτυξη σαφή ορόφου θάμνων και παρεδαφιαίας βλάστησης. Βάσει των αλλομετρικών μοντέλων υπολογίστηκε ότι η μέση συγκέντρωση άνθρακα στο εκτάριο της ζωντανής ξυλώδους βιομάζας των υπό αναγωγή συστάδων (μέσης ηλικίας 35 ετών) (59 t/ha) είναι σχεδόν διπλάσια συγκριτικά με αυτή των πρεμνοφυών(31 t/ha). Η αντίστοιχη συγκέντρωση ανά άτομο των υπό αναγωγή συστάδων (41 kg/άτομο) βρέθηκε πολλαπλάσια σε σχέση με των πρεμνοφυών (7 kg/άτομο). Η υπέργεια ξυλώδης βιομάζα για το σύνολο των δειγματοληπτικών επιφανειών δεν εμφάνισε σημαντικές αποκλίσεις μεταξύ των τριών αλλομετρικών μοντέλων που χρησιμοποιήθηκαν. Τα ισχυρότερα στατιστικά μοντέλα που προέκυψαν βάσει της απλής παλινδρόμησης ήταν αυτά με εξαρτημένη μεταβλητή την υπέργεια ξυλώδη βιομάζα και ανεξάρτητες μεταβλητές τον όγκο και την κυκλική επιφάνεια (R2=0,90, p<0.01 και R2=0,97, p