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ŠUMARSKI LIST 3-4/2013 str. 44     <-- 44 -->        PDF

height where the living foliage appears is 50–60 cm above the ground and in areas where the LF of trees appears at ground level is not observed (p>0.05) either in sparse and dense formations (Table 4). However, as it is expected, in all the structural types mentioned above there is no difference between the two site types and the two categories of the living foliage appearance, regarding the density of G seedlings (p>0.05) (Table 2, 4).
The depth of the ground organic layer under a single tree or a group of J. excelsa trees is not the crucial factor that led to the establishment of a greater number of seedlings under facilitation (F) in (more or less) productive sites (site type A) compared to that of less productive sites (site type B) (Table 5). In site type B, there is a greater depth of ground organic layer under single trees or groups of J. excelsa trees where the LF appears in 50–60 cm above the ground compared to that under single trees or groups of J. excelsa trees where the LF appears at ground level. This is not associated with a difference between densities of F seedlings (p>0.05) in the corresponding structural types (STBDD and STBDDGR as well as STBDS and STBDSGR) where these two categories (regarding living foliage appearance) of single trees or groups are found (Table 4).
The establishment of a greater number of F seedlings in site type A compared to that of site type B is probably the result of greater amount of available growing space (see Oliver and Larson 1996) that exist under and near nurse plants in site type A. This is referred mainly to higher water availability (as a result of a deeper soil) (see Papalexandris and Milios 2010). This greater amount of available growth space gave the F plants the ability to confront better the competition of nurse plants. According to Papalexandris and Milios (2010) the higher soil water content of productive sites (as a result of greater soil depth), compared to that of medium productivity sites probably permit the establishment and survival of beech seedlings in low elevation beech stands in the central part of the Evros region in northeastern Greece. Furthermore Milios and Papalexandris (2008) for the same stands mention that the higher soil water content probably permit the survival of beech seedlings under heavy shade. According to Pugnaire and Lugue (2001) the importance of facilitation, among different plant species, increases in more stressful environments (regarding abiotic conditions) while, in the same time, there was an increase in below-ground competition. Even when positive interactions (facilitation) among plants predominate, competition for water may exist (Maestre et al. 2003).
Juniperus excelsa formations in Prespa National Park exhibit lower density of J. excelsa seedlings compared to that of the mixed formation of the species in the central part of Nestos valley in Greece (see Milios et al. 2007). On the other hand in some site types in Cyprus J. excelsa groups and small stands have greater density of seedlings than the formations of the species is the present study (see Milios et al. 2011).
The results of this research support the conclusions of previous studies regarding the growth behaviour of the species that is characterized as one that can be established and grow either in light or under shade (Milios et al. 2007, 2009, 2011) since seedlings growing in diverse growth conditions (full light, shade) were found.
Taking into account the characteristics of J. excelsa, it can be a very interesting candidate species for restoration of degraded lands.
Moreover, if we consider that, in Cyprus, in harsh environmental conditions, facilitation influences positively the successful establishment of Pinus brutia (Petrou and Milios 2012) which is a light demanding, pioneer species that can survive in severe environments (Quezel 2000; Boydak 2004), then in the context of climate change in many areas the regeneration of many species will be problematic as a result o harsh climatic conditions. New species that can adapt in the new ecological condition must be introduced. Juniperus excelsa can be one of these species.
Facilitation does not dominate in the regeneration process of J. excelsa in Prespa National Park. On the other hand, this does not mean that regeneration in gaps predominates, since only in one (of the three) sparse structural types, the J. excelsa seedlings in gaps are the dominant form of regeneration. It seems that the process of grazing through trampling and animal tread determines the regeneration process of the species that can be established and grow either in light or under shade. Juniperus excelsa can be a very interesting candidate species for restoration of degraded lands.
We would like to thank the Bodossaki Foundation for providing financial support to Mr. Stampoulidis.
Ahmed, M., I. Ahmed, PI. Anjum, 1989: A study of natural regeneration of Juniperus excelsa M.Bieb in Balouchistan. Pak. J. Bot. 21(1): 118–127.
Ahmed, M., SS. Shaukat, AH. Buzdar, 1990: Population structure and dynamics of Juniperus excelsa in Balouchistan, Pakistan. J. Veg. Sci. 1: 271–276.
Athanasiadis, N, 1986: Forest botany, Part II, in (Greek) Yahoudi-Yapouli, 309 p., Thessaloniki.