LONG-TERM POLLEN MONITORING EXPERIMENTS FOR THE PERIOD 1994-2008 IN THE RILA MOUNTAINS, BULGARIA

Eurasscience Journals Eurasian Journal of Forest Science (2016) 4(1): 1-16 LONG-TERM POLLEN MONITORING EXPERIMENTS FOR THE PERIOD 1994-2008 IN THE RILA MOUNTAINS, BULGARIA Spassimir Tonkov1*, Elissaveta Bozilova1, Dolja Pavlova1, Ivan Raev2 1Department of Botany, Faculty of Biology, Sofia University “St. Kliment Ohridski”, 1164 Sofia, Bulgaria, * Corresponding author, , 2Forest Research Institute, Bulgarian Academy of Sciences, 1756 Sofia, Bulgaria, Abstract The annual pollen influx in the altitudinal zone 1800-2050 m a.s.l. produced by plant communities in the coniferous and subalpine vegetation belts of the northwestern Rila Mts. was analyzed for the period 1994-2008. The results from the five pollen traps placed on south and north slopes of a ridge revealed the dominance of Pinus diploxylon-type (Pinus mugo, Pinus sylvestris) and relatively constant presence of Picea abies and Pinus peuce pollen, with the exception in years of abundant flowering (1997, 1999, 2003 and partly 2005). The species Fagus sylvatica which grows at lower altitudes showed very good capabilities of pollen dispersal upslope. The trapping results indicated a cyclicity in the flowering of beech, with maximal pollen influx values in years 1994, 1999, 2005 and 2007, most probably dependent on the local climatic conditions. Pollen of deciduous trees such as Quercus, Carpinus betulus, Corylus, Alnus, Betula, although in less quantities, was also recorded in the traps. The herb component constituted only a small part of the total annual pollen influx. The results from long-term pollen trapping experiments could be applied to monitor the future trends in forest development in relation to climate change and local disturbances. Key words: pollen monitoring, pollen traps, pollen influx, trees, Rila Mts., Bulgaria Özet Rila Dağı 1800-2050 m yükseltileri arasındaki zirve altı kuşaktaki bitki toplumlarının ve iğne yapraklı ormanların 1994-2008 yılları arasındaki polen dağılımları incelenmiştir. Sırtların kuzey ve güney bakılarından toplanan toplam 5 adet polen kapanlarından elde edilen bulgulara göre en hâkim türlerin Pinus diploxylon-tipi (Pinus mugo, Pinus sylvestris) ve yoğun çiçeklenme yılları olan (1997, 1999, 2003 ve 2005 yılları hariç) nispeten Picea abies ve Pinus peuce polenlerinin sürekli olarak varlık gösterdiği tespit edilmiştir. Alt yükseltilerde yayılış gösteren Fagus sylvatica’nın yamaç yukarı yönde yoğun bir polen saçımı potansiyeli gösterdiği gözlemlenmiştir. Polen kapanlarıyla elde edilen bulgulara göre, kayın polenlerinin dağılımlarında, büyük ihtimalle mikro iklime bağlı olarak, bilhassa azami çiçeklenmenin gerçekleştiği 1994, 1999, 2005 ve 2007 yıllarında döngüselliğin meydana geldiği görülmüştür. Quercus, Carpinus betulus, Corylus, Alnus, Betula gibi yapraklı türlerin polenlerine de az miktarda da olsa rastlanmıştır. Otsu türlerin polenlerine yıllık toplam polen miktarları arasında çok düşük bir oranda rastlanmıştır. Uzun dönemli polen izleme çalışmaları ile iklim değişikliği ve yerel orman zararlarından ormanlarda doğacak değişikliklerin izlenmesi mümkün olabilecektir. Anahtar Kelimeler: Polen izleme, Polen kapanı, Polen saçımı, Ağaçlar, Rila Dağı, Bulgaristan. INTRODUCTION Pollen monitoring experiments provide information on the recent state of plant ecosystems as the pollen rain produced is dependent on different ecological factors. The relationship modern vegetation/pollen is determined by the pollen production of the individual species and their ecophysiological characteristics, which in turn are linked with temperature and humidity for the corresponding period of observation (Hicks 2001). The use of pollen traps enables to calculate annual pollen deposition of individual taxa with 1 Eurasian Journal of Forest Science 2016 (4)1:1-16 confidence (pollen accumulation rates or pollen influx) and to relate the inter-annual variation in pollen deposition to seasonal meteorological changes (Hicks 1996, van der Knaap et al. 2010). The main advantage of pollen traps over surface moss samples is that the former provide an independent pollen record for each taxon, unaffected by changes in abundance of other taxa (Seppa and Hicks 2006). In forest ecosystems particular focus is placed on the tree-lines as those are regarded as one of the most climate-sensitive ecotone zones in the landscape to changes in environmental conditions. Pollen monitoring investigations are of basic relevance for a better understanding of the long-term ecological processes driving the spread, establishment and persistence of individual tree populations. Apart from their scientific interest, the results are indispensable for modern forest management based on scientifically built scenarios of future environmental change (Birks 1996). The Pollen Monitoring Programme in Europe was launched in 1996 (Giesecke et al. 2010) and within short period of time the first observations based on results from the network of standardized pollen traps were published (Hicks et al. 2001). The Bulgarian palynologists were among the first who joined this programme and until now pollen monitoring experiments for different periods of observation were conducted in the Rila (Tonkov et al. 2001, 2004, 2009), the Western Rhodopes (Lazarova et al. 2006), the Central Stara Planina (Atanassova 2007) and the Strandzha (Filipova-Marinova et al. 2007) mountains, and in the lowlands of northeast Bulgaria (Bozilova et al. 2012). Moreover, data from the analyses of pollen traps and surface moss samples were included in several review papers dealing with specific problems of pollen monitoring on a European scale (Filipova-Marinova et al. 2010, Pardoe et al. 2010, Pidek et al. 2010). The Pollen Monitoring Programme has also expanded in other Balkan countries including research activities in Greece (Gerasimidis et al. 2006) and in the European part of Turkey (Karlioglu et al. 2014, 2015). The present paper is an attempt to summarize and discuss the results from long-term pollen trapping studies in the coniferous forests of the Rila Mts. in the altitudinal zone 1840-2050 m a.s.l. in relation to the modern vegetation and climatic factors (temperature and precipitation). Such a valuable information can also serve as a basis for interpreting fossil pollen assemblages obtained from mountainous areas (Hicks et al. 2001). MATERIAL AND METHODS The study area and field collection The first pollen traps in the Rila Mts. were placed in the autumn of 1993 (Tonkov et al. 2001). Until 2005 eleven pollen traps were placed in the northwestern part of the mountain in different locations following the EPMP guidelines (Hicks et al. 1996). The location of the traps was selected so that pollen deposition would reflect the local picture of the modern vegetation and provide information about pollen production, dispersal and deposition within different vegetation belts and plant communities. Unfortunately, several traps disappeared and the subsequent efforts to restore (...truncated)