Growth of Scots Pine and Silver Birch Seedlings on Different Nursery Container Media

Peat has been the most common growing medium in tree nurseries, either alone or as a component of growing media mixes. However, as a result of increasing costs and decreasing amount of peat, seedling-growers are seeking more local growing medium components. In this study, container seedlings of Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth) were grown in pure peat and peat mixtures containing perlite and zeolite. Physical parameters (height, shoot diameter, root dry weight, shoot dry weight, total dry weight) were measured along with several morphological parameters (sturdiness quotient, height/diameter, shoot/root ratio). The zeolite additive in peat changed some media properties, and significant relation was established between some morphological attributes of seedlings and some medium properties in both species. On average, the seedlings grew best in pure peat, but zeolite additions to peat did not affect some morphological parameters negatively. The results suggest that zeolite has potential to be used as a component of peat based growing medium mixtures, and addition of zeolite to peat container medium in proportions of 10% by volume in Scots pine and up to 20% in silver birch was shown to be a feasible material for growing Scots pine and silver birch seedlings.


Introduction
Competing vegetation, transplant shock, low seedling quality or lack of site preparation can reduce outplanting success (Ward et al., 2000;Apholo and Rikala, 2003;Jacobs et al., 2004 and2012;Wilson and Jacobs, 2006;Pinto et al., 2011;Tsakaldimi et al., 2013).Thus, field establishment may be improved through nursery treatments that ensure high quality seedlings and promote the development of a well structured root system (Tsakaldimi et al., 2009).Determination of the morphological and physiological attributes of seedlings that can be quantitatively correlated with improved field performance of planted seedlings and thus, can be successfully used for predicting the early plantation success, should be of high priority in forest practice (Duryea, 1985;Mattsson, 1997;Wilson and Jacobs, 2006;Aytas and Tilki, 2007;Tsakaldimi et al., 2013).
Container media is an important determinant of seedling quality, and peat has been the most common growing medium for growing seedlings (Langerud and Sandvik, 1987;Bunt, 1988;Landis et al., 1990;Schmilewski, 1992).However, as a result of increasing costs, decreasing amount of peat, and the social pressure to reuse the waste resulting from human or industrial activities, local growing medium components (sewage sludge, pine bark, sawmill residues, perlite and numerous other substitutes in different proportions) were studied in using growing experiments in many countries and also in Turkey (Landis et al., 1990;Chong and Lumis, 2002;Aldrete and Mexal, 2005;Ayan and Tilki, 2007;Manas et al., 2009;Heiskanen, 2013).The properties of peat-based media can influence water and air availability and plant growth (Langerud and Sandvik, 1987;Heiskanen, 1993Heiskanen, , 1997)).
Zeolites, a naturally occurring mineral group consisting about of 50 mineral types, draw attention as a good medium.The proportions of the components hand-mixed into the peat were determined by volume (Tab.1).
Daily watering was done with sprinklers.During the growing season in the nursery the seedlings were fertigated (fertilized with the irrigation water) with Superex after analyzing soil for EC and pH regularly (Tabs.2, 3) (Richard and McDonald, 1979).
growing medium substrate for a long period due to its good physical and chemical characteristics (Markovich et al., 1995).They have a rigid three-dimensional crystal structure with voids and channels of molecular size and high cation exchange capacity (CEC) arising from substitution of Al for Si in the silicon oxide tetrahedral units that constitute the mineral structure (Ayan, 2002;Pickering et al., 2002).Zeolite has many good features that make it very attractive for nursery use as a growing medium compared to other growing media types such as perlite, pumice and river sand (Koksaldi, 1999).Although Turkey has very rich zeolite potential, there is a lack of information on the possibility of commercial use of zeolite as a growing media in seedling production.
The aim of the present study was to determine how different growing media based on peat with zeolite affect seedling survival and attributes in nursery.For this purpose, Scots pine and silver birch, important tree species in Eastern Turkey due to their ecological and economic value, have been selected.

Seedling production
One-year-old Scots pine and silver birch seedlings were grown in containers following normal practice for Turkish nurseries at the nursery of the East Anatolia Forest Research Institute at Erzurum (1750 m asl), Turkey.Seeds of Scots pine from Kars-Sarikamis origin were sown to plastic enso container trays (Enso-Finland Model Type) (9 x 5 cells of 220 cm 3 each) on April 21, 2008, and seeds of silver birch from Erzurum origin were sown to plastic enso container trays on June 14, 2008 in greenhouse.The laboratory germination capacity of the Scots pine and silver birch seed lots was 97% and 90% at 21 days, respectively.
Seedlings were kept in greenhouse for two months after sowing.Later, they transferred into a shaded area for one month for acclimatization before letting them outdoor conditions.Seedlings were kept in outdoor conditions until they got ready for planting.Mixtures of Finland peat (FP), zeolite (Z) and perlite (P) were used as growing media in the trays.Finland peat was used as main additive material in pots and was classified as H1-H3 quality class peat according to Von Post scale, particle size was less than 2 mm.Balıkesir-Bigadic (Turkey) originated clinoptilolite natural zeolite, clinodor-agro, particle size was 1-3 mm was also used as a growing medium.Six different volume combinations of these three different potting media with and without zeolite were established and used as a growing 566

Physical and chemical characteristics of the media
During growing season soil pH and EC were measured.Before seed sowing, growing media samples were analysed for their physical and chemical properties such as bulk density, water holding capacity, specific gravity, porosity and air capacity.
Organic matter content was determined by the Walkley-Black method (Nelson and Sommers, 1996), pH was measured with a combination glass-electrode in H2O (soil-solution ratio 1:2.5), and cation exchange capacity was calculated by the sum of cations determined by the NH4OAc method (Kalra and Maynard, 1991).
Phosphorus was determined according to Brayl (Dilute acid-fluoride) procedure (Kalra and Maynard, 1991).Exchangeable cations and micronutrient cations were determined by atomic absorption spectrophotometry according to Kacar (1996).Electrical conductivity was determined following the procedure described by Kalra and Maynard (1991).The total nitrogen was analysed by the micro Kjeldahl technique (Kalra and Maynard, 1991).
The bulk density (Db) was determined by the core method (Grossman and Reinch, 2002) and the particle density (Dp) was determined by the pycnometer method.The total porosity (TP) was estimated as (Dp-Db) Dp -1 , where Db is the bulk density (Heiskanen, 1993), obtained by using the following equation: St=[1-(bulk density/particle density] (Flint and Flint, 2002).Air content was estimated based on the formula: Air content (%) = Porosity (%)-Water holding capacity (%).

Seedling measurements
In each species, 45 seedlings per treatment were sampled at random.Shoots height, root collar diameter, and dry weight of shoots and roots were measured at the end of first vegetation period.
Dry weight was measured after drying for 24 h at 105 °C.

567
Experimental design and data analysis Experiment was arranged in a completely randomized block design with three replications for each treatment.Totals of 6 treatments were randomly assigned into each block.45 seedlings per treatment in each species were sampled in each sampling time.To test the significance of differences the data of seedling attributes were analysed with ANOVA in a randomized block design (SPSS software, SPSS Inc).Variables were tested for normality and homogeneity of variances and transformations were made when necessary to meet the underlying statistical assumptions of ANOVA.Duncan's New Multiple Range Test procedure was used to compare mean values (for p<0.05).`

Results and discussions
The pH increased while EC was relatively uniform during growing season in Scots pine growing media.These two parameters were uniform in silver birch growing media during growing season (Tabs. 4,5).
The main soil characteristics of the growing mixtures studied were shown in Tab. 6. Organic matter content decreased with the zeolit of the mix.The water holding capacity of the mixes and total porosity decreased slightly with the zeolit content.The chemical properties varied among the mixes.The pH was 5.07-5.27and was high (at 5.27) in pure peat, as was electrical conductivity (0,42 mS cm -1 ) and CEC (127.6 mg/100 g).Na, Mg, Al, B, Cu, Ca and Fe increased with the zeolit content of the mixes.
The germination capacity of the Scots pine and the silver birch seed lots was 95% and 85% at 60 days from sowing, respectively.Scots pine and silver birch had very low mortality.Seedling emergence in seedling production is affected by many factors, and growing media is one of them (Aldrete and Mexal, 2005;Manas et al., 2009).In this study there were no differences in mortality among media in each species although some chemical properties of growing media with zeolite changed.Although the zeolite and/or perlit additive in peat changed the some properties of the medium, the lower Ec, water holding capacity, organic matter, Fe, Mn, Pb, S, and the higher Mg, Al, Ca in zeolite additive growing media had no distinctive effect on seedling emergence and survival.
There were no significant differences between the growing media in the diameter growth of Scots pine.But the other parameters were significantly affected by the growth medium (p<0.05)(Tab.7).Additions of zeolite and/or perlite to peat medium were found to affect other seedling morphological parameters.

568
The tallest Scots pine seedlings were grown in peat, and the seedlings grown in peat, reached a stem length of 13.52 cm.No treatment differences in seedling height were obtained for those grown in pure peat, FP70P20Z10 and FP90Z10.The lowest height growth (11.86 cm) was obtained in FP80Z20.The highest seedling root dry weight values were recorded in pure peat and the lowest in FP70P20Z10 and FP70P10Z20.Althought shoot dry weight was the highest in pure peat, it did not differ significantly between the seedlings grown in P100, FP70P20Z10, FP80P10Z10, FP90Z10.Seedling grown in media containing 20% perlite had the highest S/R.The growing media containing Z20 decreased the shoot dry weight and SQ.In all the substrates, the lowest DQI was recorded in FP70P20Z10, and no treatment differences in DQI were obtained for those grown in other mediums.
All morphological parameters of silver birch measured in the study except diameter growth were significantly affected by the growth media (Tab.8).The highest seedling height value was recorded in FP70P10Z20 (20.73 cm), and no treatment differences in seedling height were obtained for those grown in pure peat and FP90Z10.Diameter did not differ significantly with growing media types.
In all the substrates, the lowest root dry weight, shoot dry weight and the DQI were recorded in growth media made of peat (80%), perlit (10%) and zeolite (10%), and no treatment differences in DQI were obtained for those grown in other media.SQ was the highest in P100, FP70P10Z20 and FP90Z10.The silver birch seedlings growth in pure peat or in medium of FP70P10Z20 and FP90Z10 have similar seedling morphological parameters.
Although in some plants there was no significant correlation between shoot height and seedling outplanting performance (del Campo et al., 2010;Tsakaldimi et al., 2013), other studies found better survival in some species the field.Ayan and Tufekcioglu (1996) found that zeolite as a growing media had no positive effects on morphology of Scots pine seedlings.Seedlings grown in the peat-based media with 10% zeolite or without zeolite did not differ significantly in oriental spruce seedlings (Ayan and Tilki, 2007).Total seedling dry weight and Dickson's quality index was found to be very important in predicting second-year field survival for Pinus halepensis and Pistacia lentiscus (Tsakaldimi et al., 2013).DQI indicates plant potential for field survival and growth with performance increasing as DQI values rise in previous studies (Oliet, 2000;Bayala et al., 2009;Manas et al., 2009).In the present study, in general, DQI of Scots pine and silver birch seedlings was high in peat and peat mixtures containing zeolit.
The height/diameter index can serve as a simple index to predict outplanting survival and it could accurately predict seedling outplanting survival in some tree species (Thompson, 1985;Villar-Salvador et al., 2004;Manas et al., 2009;Tsakaldimi et al., 2013).In the present study SQ was the highest in pure media in Scots pine, and it did not differ significantly with the growing media of peat, FP70P10Z20 and FP90Z10 in silver birch.
Addition of perlite and fine quartz sand to peat medium did not affect seedling growth negatively but affected rooting slightly in Scots pine and silver birch (Heiskanen and Rikala, 1998).Rooting of Norway spruce and silver birch was greater in pure peat medium than peat mixtures containing perlite and/or fine sand.No clear benefit for seedling rooting and establishment after planting was found by incorporating fine or coarse constituents in proportions below 50% into peat container medium (Heiskanen and Rikala, 2000).
with taller seedlings (Villar-Salvador et al., 2004;Tsakaldimi et al., 2013).As with height, diameter is not always correlated to field survival but is related to subsequent growth (Thompson, 1985).Nonetheless, root collar diameter is a good indicator of growth potential after planting for some forestry species such as Cedrus libani (Semerci, 2005).
Root-collar diameter has been recognized as an important initial attribute of nursery seedlings to promote field survival, particularly under drought conditions in previous studies (South et al., 1993 and2001).Root collar diameter was found to be the best predictor of second-year outplanting survival in five Mediterranean species (Quercus ilex, Q. coccifera, Ceratonia siliqua, Pinus halepensis and Pistacia lentiscus) (Tsakaldimi et al., 2013).In general, larger seedlings had better field survival, and diameter was the common variable that accurately predicted survival for many species.Large diameter seedlings are likely to have more stored nutrients and carbohydrates (Tsakaldimi et al., 2013).
The present study showed that, for two studied species, seedling diameter growth did not differ significantly among the growing media.
There were no significant differences between the growing media in the diameter growth of Scots pine and silver birch seedlings.Although the tallest Scots pine seedlings were grown in peat, no treatment differences were obtained for those grown in peat, FP70P20Z10 and FP90Z10.The highest shoot height of silver birch was recorded in FP70P10Z20, the the seedling growth in pure growing media or in the media of FP70P10Z20 and FP90Z10 have similar seedling morphological parameters.This suggests a good potential for seedling performance in In the present study, growing media properties affected some seedling attributes (Tab.9).Height of Scots pine seedlings had a significant positive correlation with pH, Ec, water holding capacity, total porosity, organic matter, CEC, S and Mn.Seedling diameter was significantly affected by Ec, water holding capacity, Na, Ca and Fe of the growing media.Increasing in K content in the growing media with 20% zeolite decreased height growth of Scots pine.These results concur with those of Ayan and Tufekcioglu (2006) that there is a negative correlation between seedling height of Scots pine and K content of growing medium (peat, tea residue compost, perlite, fine pumice, coarse pumice, river sand, and zeolite).
Root dry weight, shoot dry weight, H/D, DQI and S/R were also significantly affected by the growing media.Most growing media properties (EC, water holding capacity, total porosity, CEC, OM, P, N, Zn, Fe, Mn, S) affected stem dry weight, and positive correlation with total porosity could be an indication of poor aeration in the growing medium due to irrigation during summer in seedling nursery.
Seedling height of silver birch negatively correlated with Na of growing media but positively correlated with water holding capacity (Tab.10).Seedling diameter was negatively correlated with C/N and Mg but positively correlated with Mn, and DQI was negatively affected by C/N and Mg of the growing media.