LITHUANIAN UNIVERSITY OF AGRICULTURE Julius Ba č kaitis THE ENVIRONMENTAL FACTORS INFLUENCE ON SCOTS PINE ( Pinus sylvestris L.) NATURAL REGENERATION Summary of doctoral dissertation Biomedical sciences, Forestry (14B) Kaunas, 2005
The doctoral dissertation has been accomplished during the period of 1999-2005 at the Lithuanian University of Agriculture The dissertation is being externally defended Science consultant: prof. habil. dr. Edvardas Riepas (Lithuanian University of Agriculture, Biomedical sciences, Forestry - 14B) The doctoral dissertation will be defended at the Lithuanian University of Agriculture at the Board of Scientific Trend in Forestry: Chairman: prof. habil. dr. Remigijus Ozolin č ius (Lithuanian Forest Research Institute, Biomedical sciences, Forestry -14B) Members: ass. prof. dr. Edmundas Bartkevi č ius (Lithuanian University of Agriculture, Biomedical sciences, Forestry -14B) prof. habil. dr. Romualdas Juknys (Vytautas Magnus University, Biomedical sciences, Forestry - 14B) dr. Juozas Labokas (Institute of Botany, Biomedical sciences, Botany - 04B) dr. Vytautas Suchockas (Lithuanian Forest Research Institute, Biomedical sciences, Forestry - 14B) Opponents: prof. habil. dr. Antanas Juodvalkis (Lithuanian University of Agriculture, Biomedical sciences, Forestry - 14B) prof. habil. dr. Vida Stravinskien ė (Vytautas Magnus University, Biomedical sciences, Ecology and Environmental Sciences - 03B) The dissertation is intended for public examination by the degree at the Assembly Hall of Forest Management department, Lithuanian University of Agriculture at 11 o'clock on June 28, 2005. Address: Department of forest Management, Lithuanian University of Agriculture, Studentu 12. LT-53361 Akademija Kaunas district, Lithuania. Ph.: + 370 37 75 25 44 Summary of doctoral dissertation was distributed on May 28, 2005. A copy of the summary of doctoral dissertation is available at the libraries of the Lithuanian University of Agriculture and Lithuanian Forest Research Institute.
LIETUVOS EM Ė S Ū KIO UNIVERSITETAS
Julius Ba č kaitis
PAPRASTOSIOS PUIES ( Pinus sylvestris L.) Ė LIMUI Į TAK Ą DARANTYS APLINKOS VEIKSNIAI
Daktaro disertacijos santrauka Biomedicinos mokslai, Mikotyra (B 14) Kaunas, 2005
Disertacija rengta 1999-2005 metais Lietuvos em ė s ū kio universitete Disertacija ginama eksternu Mokslinis konsultantas: prof.habil.dr. Edvardas Riepas (Lietuvos em ė s ū kio universitetas, biomedicinos mokslai, mikotyra 14B) Disertacija ginama Lietuvos em ė s ū kio universitete Mikotyros mokslo krypties taryboje: Pirmininkas: prof.habil.dr. Remigijus Ozolin č ius (Lietuvos mik ų institutas, biomedicinos mokslai, mikotyra 14B) Nariai: doc.dr. Edmundas Bartkevi č ius (Lietuvos em ė s ū kio universitetas, biomedicinos mokslai, mikotyra 14B) prof.habil.dr. Romualdas Juknys (Vytauto Didiojo universitetas, biomedicinos mokslai, mikotyra 14B) dr. Juozas Labokas (Botanikos institutas, biomedicinos mokslai, botanika 04B) dr. Vytautas Suchockas (Lietuvos mik ų institutas, biomedicinos mokslai, mikotyra 14B) Oponentai: prof.habil.dr. Antanas Juodvalkis (Lietuvos em ė s ū kio universitetas, biomedicinos mokslai, mikotyra 14B) prof.habil.dr. Vida Stravinskien ė (Vytauto Didiojo universitetas, biomedicinos mokslai, ekologija ir aplinkotyra 03B) Disertacija bus ginama vieame Mikotyros mokslo krypties tarybos pos ė dyje, kuris vyks 2005 m. birelio m ė n. 28 d. 11 val. Lietuvos em ė s ū kio universitete, Mikotvarkos katedros pos ė di ų sal ė je. Adresas: Mikotvarkos katedra, Lietuvos em ė s ū kio universitetas, Student ų 12, LT-53361, Akademijos mstl., Kauno r., Lietuva Tel. 370 37 752 544 + Disertacijos santrauka isiuntin ė ta 2005 m. gegu ė s 28 d. Disertacij ą galima peri ū r ė ti Lietuvos em ė s ū kio universiteto ir Lietuvos mik ų instituto bibliotekose.
TABLE OF CONTENTS 1. GENERAL STUDY DESCRIPTION .......................................................................................................6 2. THE REVIEW OF THE LITERATURE ..................................................................................................7 3. THE OBJECTS OF STUDY AND METHODS .......................................................................................8 4. ECOLOGICAL FACTORS INFLUENCE ON PINE REGENERATION IN THE CLEAR-CUTS .......9 Fig. 1. The influence of distance from forest edge to amount of 2-3 years pine seedlings in 3 years old clear-cutting areas. ......................................................................................9 Fig. 2. The influence of distance from forest edge to amount of 2-4 years pine seedlings in 4 years old clear-cutting areas. ....................................................................................10 Fig. 3. The relation between the density of self regenerated pines and the distance from edge of old pine stand and their exposition in 1-4 yrs old clear-cuts. .............................11 Fig. 4. The amount of pine seedling in 1-4 yrs old clear-cuts on the subject to the distance from the forest edge and soil scarification.........................................................12 5. ECOLOGICAL FACTORS DETERMINING SELF-REGENERATION OF SCOTS PINE IN CLEAR-CUTS WITH PRESERVED SEED- AND SHELTER-TREES..................................................................13 Fig. 5. The density of pine seedlings in various rage clear-cut areas in dependence on the number of seed trees and shelter trees. ............................................................................14 Table 1. The dependence between amount of 1-3 years pine seedlings from clear-cut age and the number per ha of seed trees and shelter trees......................................................14 Fig. 6. Density of pine seedlings in 1-4 years clear-cuts in respect to ground scarification and seeds trees, shelter wood trees left. ...........................................................................15 6. CONCLUSIONS AND SUGGESTIONS ...............................................................................................16 REZIUME....................................................................................................................................................17 PUBLICATIONS OF DISSERTATION.....................................................................................................18
1. GENERAL STUDY DESCRIPTION
The study relevance. One of the present forestry challenges is to combine forest use with protection functions, to ensure the natural survival of ecosystem components and elements (the flora, fauna and other organisms), their vitality of populations. Applying step-wise cuttings and by other ways trying to promote natural regeneration is conserved near to natural environment, survive adopted to local conditions floras genotypes, is ensured the contiguous ecosystem appearance as well as habitats for birds and other biodiversity forms left stable or marginally change. There is 66% self regenerated pinewood in Lithuania. The rest part compounds the cultural pine forest (Lietuvos mik ų , 2004). After the Second World War it was believed that isnt possible naturally regenerate pinewoods and moreover it isnt needed. On the strength of this idea there were no any project naturally regenerate the pine forests. Despite S. iniausko (1935), A. Vilkai č io (1966), B.Labanausko, K. Narbuto (1969) and other scientists given facts, that in many cases, when opening had the suitable conditions, the pinewood reforest well, it was still believed that reforestation in artificial way is more reliable, simpler and cheaper. This question is not well analysed in other European countries. Despite of plenty pine natural regeneration investigations at the beginning and mid of the last century (Brown, 1906; Hoffman, 1917; Sarvas, 1949; Hagner, 1962; Lehto, 1969 and others), the studies were intensively renovated in the last decade (Cameron, 1995; 1999; Westerberg and Hofsten, 1996; Zhou, 1997; Karlsson and Örlander, 2000, and oth.), because in many countries forest policy more and more orientated to natural processes in forest ecosystems and forestry. Naturally regenerated forests are more viable and more resistant than planted. Besides, naturally regenerated forest provides more reliable preservation of biodiversity, there is no needed to worry about seedlings and shoots and we save the resources for the artificial forest planting. At the moment it is very important in Lithuania, because very often are planted pine monocultures aiming on pure pinewood stands. The aim and task. The aim of this study is to investigate the possibilities of pine natural regeneration in different nature regions in the clear-cuts with main site types. The tasks of this work are: 1. to estimate a potential possibilities of pinewood natural regeneration; 2. to find out the ecological factors, that have a great influence on pine sprouts on the Na (dry not fertile), Nb (dry less than average fertile) and Lb (with excess water and less than average fertile) site types and to set their critical borders; 3. to find out the main economical factors, that promotes pine regeneration (site preparation, seed trees, shelter wood); 4. to prepare the recommendations to promote the pinewood natural regeneration. Recency and originality. This is the first investigations were made in complexly including the most common sites in Lithuania for pinewood (Na, Nb and Lb site types) in the three native regions covering largest part of Lithuania. This enables to make prognoses of pinewood regeneration in those regions on the mentioned site index. For the first time there were defined the sufficiency of the shelter-seed trees for regeneration and their distribution in a clear and step wise cutted areas to ensure the natural regeneration of pine. There were found that 2-3 point yield of pine seeds (under Capper) and on the time and in right way implemented encouragements, ensure natural pine regeneration after clear or step wise cuttings. Following the results, it was suggested to advance the second (last) step of step wise cuttings (or to cut the seed trees in a clear cuts), which should be done not at 5-10 years after the first cuttings as it was recommended before, but at the 3-4 years. The scientific and practical importance. It is the great source of knowledge about relations between forest ecosystems elements and environmental issues. There were clarified major environmental issues, that determinative pine regeneration in a clear-cuts and non-clear-cuts, defined their impact borders and possibilities to control the regeneration with the stimulating economical implements. With reference to the results there is given the suggestions how to implement the natural pine regeneration. Mostly important presented states. After the first step of step wise cuttings in Nb and Lb soil types with final stand 0,3-0,4 stocking level and scarified >20% soil of managed area all cutted areas regenerate well. In the pinewoods that are cutted by clear cutting that is enough to leave 35-60 seed trees per ha (dependent on the potential aggressiveness of herb layer, neighboring stands, width of clear-cut). Approbation. There are two scientific papers on refereed journals and one issue in scientific popular magazine. The work structure and size. The dissertation compounds introduction, review of the literature, work methodology, the results of the research, the findings and discussion, literature list and appendixes. The results of the dissertation are presented in a two sections. There are analyzed 243 literature sources. The total size of the dissertation is 93 pages, 24 tables and 17 pictures.
2. THE REVIEW OF THE LITERATURE
Never the less of the prediction that a regenerate pine stand artificially is more reliable, more simply and even cheaper, that cultural stands produce more wood ( Прокопьев , 1981; Au č ina and Danusevi č ius, 1997; Mikys, 1999 and others), naturally regenerated stands are more vital and more resistant than cultural stands (Leibundgut, 1981; Тихонов , 1982). There are better conditions for biodiversity in natural regenerated stands, and stands with a recreational purpose has better esthetic value ( Данюлайтис , 1974; Репшас , 1994). There are a lot of environmental factors that influence the pine natural regeneration. They influence pine yield, spread and germination of the seeds and survival of seedlings. The seeds productivity of trees and stands depends on many factors: the age ( Побединский , 1979 b, Мелехов , 1980, Booth, 1984), the trees location in a stand ( Тимофеев , 1939; Разумов , 1940; T юрин , 1952; Boot, 1984), crop periodicity (Labanauskas and Narbutas, 1969; Ramanauskas, 1977; Бузун , Турко , 1996; Danusevi č ius et al., 1999), the composition of the soil (Sarvas, 1962; Heitmüler, 1964 ; Labanauskas, Narbutas, 1969; Schmidt-Vogt, 1991), climatic conditions (the air temperature and moisture, beneficial distribution of precipitation during the vegetation etc.) (Braun, 1992) and other factors. Only 40% of matured seeds reach the soil. The lost of the seeds comes out because of the untimely fall immature cones, some of the seeds stay in the cones, and some are damaged by disease and pests. Besides the empty seeds, which range from 10 to 40% in various years (Leibundgut, 1981), the soil reach also a part of not completely mature seeds (Schmidt-Vogt, 1991). Generall erminate not more than 50% roductive seeds Каппе , 1954; Schmidt-Vo t, 1991 . The s read distance of seeds from the seed tree de ends on wind, tree hei ht also seeds wei ht Kohlermann, 1950 . Re uted, that about 90% of ine seeds s reads u to 50 meters, that is over double distance com arin with the tree hei ht, and, when the weather is calm, seeds s read onl u to 35 meters A лексеев and Молчанов , 1938; Booth, 1984; Wiersum, 1984; Gorzelak, 1999; Suchockas, 2002 a ). There are three groups of environment factors, that influence the seeds germination and the survival of the plants: abiotic factors (climate, edaphic, orografic), biotic factors (photogenic, zoogenic) and anthropogenic factors (the pollution of air and soil, the damage of the soil (recreation, cuttings), tapping). The stimulation of pine regeneration should be set separately protection of the undergrowth ( Писаренко , 1977; Побединский , 1979 b ), cuttings of the underbrush ( Санников , 1961), the cuttings of optimal width clear-cutting areas ( Юркевич , 1939 b ; Тимофеев , 1951; Тюрин , 1952; Ткаченко , 1955; Писаренко , 1977; Калиниченко et al., 1991; Jakas and Juodvalkis, 1992), the leaving of seed trees or shelter trees ( Тимофеев , 1943; Labanauskas and Narbutas, 1969; Писаренко , 1977; Booth, 1984; Sundkvist, 1993; Zhou, 1999; Karlsson, 2000), soil preparation (Labanauskas and Narbutas, 1969; Побединский , 1979 b ; Dunlop, 1983; Booth, 1984; Low, 1988; Калиниченко et al., 1991; Gong et al, 1991; Skoklefald, 1995; Karlsson and Ő rlander, 2000; Suchockas, 2001, etc.), reduction of grass cover and litter in the forest (Ca нников , 1961; Labanauskas and Narbutas, 1969; Побединский , 1979 b ), the drainage (Jakas et al., 1994), fencing (Tapa н and C пиридонов , 1977), the reduction of cuttings garbage ( Побединский , 1973), forest regeneration stimulating fire (A лексеев and Молчанов , 1940;L Т at ю el рин , 1952n; d Wmegner,a t1te9n5t7i;o n А i6 e н n, 1o9n8 c9,o nSscehrivmatmioenl, o1f9 9b3i)o dainvde rostithye.r . The priority y more a ore is given to naturally regenerated forest together with stimulating implementation. Summarizing the whole Lithuanian and European countries scientists remarks about pine regeneration obviously seems that important questions in Lithuania were analyzed only episodically. Both, natural regeneration supporters and opposition refer to separate projects, individual investigations, which were made in different part of Lithuania, Europe or even Siberia, never the less since this century it was predicated, that in different geographical environments pine regeneration is influenced by different factors. The first study of pine regeneration in Lithuania was made 4 decades ago by B. Labanauskas, while in Scandinavia as well as in the rest of Europe such kind of researches is done permanently. The accumulation of such information often variance and even occur controversial. The natural pine regeneration is very relevant also to Lithuanian foresters that make this topic essential. There should be prepared the information about potential possibilities to regenerate pine in cutting areas on a different soil type also in different natural regions of Lithuania, to prepare the information about soil preparation and the efficiency of shelter trees. My investigation was provided in three mostly abundant pinewood soil types in a three native regions. There were determined optimum numbers of seed-shelter trees, their distribution in clear and step wise cuttings to ensure efficient natural regeneration of pinewoods. All areas on the most cases regenerate well if would be left more than 30 trees per ha trees and scarified >20% soil of managed area after cutting in early spring.
3. THE OBJECTS OF STUDY AND METHODS
The study of pine regeneration were made: 1. In a clear cuts with a different distance from the old forest edge, depending on their exposition. 2. In clear cuts leaving the seed trees (20-60 units per ha) and after step wise cuttings, leaving 0,3-0,4 stocking level stands (61-120 shelter trees per ha). The research of pine regeneration in clear cuts with a different distance from the forest was made in 1996-2000 clear-cutting areas, after it was cut 0,6-0,9 stocking level pine stands in akiai, Kazl ų R ū da, Jurbarkas, Druskininkai, Anyk č iai and Nemen č in ė forest enterprises. The measurements were made in systematically set square shape 2×2 meters size areas according to A. Pobedinskis ( Побединский , 1966), A. Martynovas ( Мартынов , 1992) recommendations and reference to,,Estimation of afforested stands methodic (Miko atk ū rimas, 2005). If the size of clear-cut area was up to 1 ha, there were plotted 20 study plots, if 1,1-3 ha 30 and over 30 40 plots. Totally there were evaluated 4093 temporary plots in 71 clear-cut areas totally around 194 ha size. The field work was made in October and March on 1999-2002, to prevent grass domination. In each research plot there were estimated: ¾ Plants growth position in the scarified microsag, in the microrise or in unmanaged soil. ¾ Amount of alive and dead 1-4 year plants and their age according to,,Estimation of afforested stands methodology (Miko atk ū rimas, 2005); ¾ underbrush composition and amount in a plot; ¾ The impact of grass on regeneration according to methodology of S. Karazija et al. (1997); ¾ Forest litter thickness on untouched ground with 0,5 cm exactness; ¾ Typology group of the soil; ¾ The distance from the forest edge till the center of plots, also forest edge orientation to coordinal points (N, E, S or W exposition); ¾ Other trees species density (Spruce, Birch, Aspen). The number of pine and other species seedling in the plot were recalculated into the density in 1 ha. The pine seedlings rate was estimated by formula ( Побединский , 1966): P ≡ n *100 h e N, w er P rate; n the number of plots were pine seedling were found; N total number of seedlings in the clear-cut. In all clear-cuts were planted 5,5-6,5 thou. of seedlings per ha before field investigation. In 1997-2000 there were made the study on pine regeneration in clear-cuts, where was (0,5) 0,6-0,9 stocking level pines stands before, with left seed trees and shelter trees in the akiai, Vilnius, Panev ė ys and ilut ė forest enterprises. The age of the seed trees and shelter trees was 105-160 year, the productivity class I-III. The research was made following the same methodology as it was used searching pine regeneration in clear cuts. The plots were separated by more than 40 meters belt from the productive pine stand edge to avoid the stand influence on the research plot. Generally, the study were made in 2140 temporary plots in 31 plot with 100 ha area in October and March of 2000-2003. In each research plot there were estimated and determinate the same variables as it was used in pine regeneration in a clear-cuts depending on a distance from the closest forest edge. Just one difference instead of a distance from the forest edge till the center of plots and the points pf the compass, there were estimated seed trees and shelter trees (also using Relascop). The meteorology conditions during the researching period were estimating according the meteorological statement (Agrometeorologinis biuletenis, 1998, 1999, 2000; Meteorologinis biuletenis, 2001, 2002, 2003). Further more MS EXCEL and statistical packages were used to work out with the received results. The primary statistical indicators and the relation between correlation margins were counted using ordinary methods. The data were analyzed by regression and dispersion analyses. The influence of factors were analyzed with dispersal analysis (ANOVA) F parameter (Sakalauskas, 1998). This parameter analyses if indicator groups averages differs credibly. If the differences are reliable, there is an assumption that analyzed factors have a positive influence. There were analyzed also the impact of two factors (Factorial ANOVA) as well as some factors (Nested design ANOVA) influence on index. When p<0,05 (95%), then the differences of means are reliable.
4. ECOLOGICAL FACTORS INFLUENCE ON PINE REGENERATION IN THE CLEAR-CUTS After the analysis was completed, the results showed that the greatest impact on the beginning of pine regeneration in the clear-cuts has the distance to the forest edge (productive pine stand). The average resilience of reverse correlation connection (r from -0,28 to -0,441) between the distance from the forest and the density of sprouts in 1-4 years old cutting areas were determinate. On the results we see that the distance from the forest has greater influence. The area in clear-cut which is closer to the forest stand every year gets a huge amount of new seeds from it, while the plot which is located in a greater distance get less seeds. With the increasing distance from the forest edge, the average density of new stand decreases in any age of the clear-cutting areas. The total new stand density in 1-4 years old clear-cutting area (the site index were not took into consideration), when it is 20 meters away from the forest is about 1,5-1,7 times less then in a 5 meters distance; when it is 40 meters away from the forest 2,3-3,1 times less then in a 5 meters distance; when it is 60 meters away from the forest 4,0-5,3 times less then in a 5 meters distance. The amount differences between seedlings that grows in 5 meters and in higher distance are always reliable (p<0, 05). The density of new stand in 20 meters from the forest is noticeably higher than in 40 meters (1,5-1,8 times) and in 60 meters distance (2,4-3,1 times). When the distance form the forest is 40-60 meters, the density of new stands in 1-4 years old clear-cutting area differs 1,4-1,8 times, but such differences are not reliable. This might be because of greater new stands mosaic distribution and measured areas are 4-5 times smaller than in closer areas to the forest. Summarizing we should emphasize that receding from the forest edge, the average new stands density in 1-4 years old clear-cutting area every 20 meters decrease 1,6 times. This allows making such an assumption that if there are known the density of new stand close to the forest age, could be predicted tentatively the density of regenerating stand in areas, which are more apart from the forest. There were no mentioned any other consistent pattern of other researches. Never the less there were 0-9,75 pine seedlings per m 2 in a different age areas, the little pines situated rather gradually. When there were 5 meters distance form the forest edge, in 57,4% areas the amount of pine seedlings didnt overpass 1 unit per m 2 , when there is 20 meters distance from the forest in 74,7% of areas, 40 meters 89,8%, and 60 meters 96,3%. Receding from the forest edge, the density of pine regenerated stands was decreasing and there were less pine regenerated stands that you can find. In the 1-4 years old clear-cutting area the minimum (57-65%) number of pine seedlings were in areas that are 60 meters from forest edge, the maximum (81-93%) was in areas that were 5 meters away from the forest edge. The age of the clear-cutting area had a week influence on pine seedlings appearance in the area. In the areas, which were closer, to the forest edge at about 5-20 meters distance (clear-cutting area getting old), there were noticeable more pine seedlings. The rate of pine seedlings was not always inversely proportional to the distance from the forest edge. In some cases the higher observing was settled in the territories more distant from the forest edge. It confirms the fact settled by other researches that the observing of pine seedlings might be higher in the territories that were more distant from the forest edge then in the closer ones ( Шиманюк , 1955; Low, 1988; Suchockas, 2001). Evaluating the regeneration of the clear cutting areas using ,,The methodology of forest regeneration accounting and evaluation (2005) only the pine seedlings of 2 years and older were taken into account. The explored clear cutting areas of 3 4 years old in the Na site type till 15-20 m and in the Nb and Lb site types till 30-35 m from the forest edge could be evaluated as well regenerated according to the total amount of 2-4 years old pine seedlings and their level of observing. The more distant territories of 3-4 years old clear cutting areas regenerate satisfactorily and from 30-35 m (Na) and 60-65 (Nb and Lb) only poorly (Fig. 1 and 2).
Nb = -4424,1 Ln(x) + 21819 Lb = -5198,8 Ln(x) + 25026 20000 Na =R 2 - 4=3 01,71,54 4 L nn(=x3) 1+0 17295R 2 = 0,135 n=1044 R 2 = 0,173 n=218 18000 Na site type 16000 Nb site type t 14000 NLbo rsimteativyep eof well regenerated clear-cutting areas Norma bad e 12000 tive of reg nerated clear-cutting areas 10000 8000 6000 4000 2000 0 0 5 10 15 20 25 30 35 40 45 50 55 60 Distance from forest edge, m
Fig. 1. The influence of distance from forest edge to amount of 2-3 years pine seedlings in 3 years old clear-cutting areas.
The worst pine regeneration in the Na site types was probably determined by much smaller amount of seeds that got there and germinated. According to V.Ramanauskas (1981), in the Lateeris pine population, where our research of the Na site type was actually made, the absolute pine seeds germination is only about 24,4%, the germination energy about 20,8%, while the average of the country is about 2,4 times bigger. Therewith, there were much less constantly cropper trees and much more never cropper trees in Marcinkoniai pinewoods then the average of Lithuania (Ramanauskas, 1977). The score (point) of cone yield was also one of the smallest in Lithuania (Ramanauskas, 1977). 20000 Na = -5046,1 Ln(x) + 20672 Nb = -4093,8 Ln(x) + 19926 Lb = -3052,6 Ln(x) + 16469 R 2 = 0,236 n=138 R 2 = 0,195 n=349 R 2 = 0,176 n=101 18000 16000 it t t e 14000 NLNbob r ssmiittaeetivyyepp of well reenerated clea-cuttin areas t e 12000 Normative of bad regenerated clear-cutting areas 10000 8000 6000 4000 2000 0 0 5 10 15 20 25 30 35 40 45 50 55 60 Distance from forest edge, m
Fig. 2. The influence of distance from forest edge to amount of 2-4 years pine seedlings in 4 years old clear-cutting areas. The number of one year seedlings was quickly decreased when the clear cut is getting older. Comparing the number of one year old seedlings in the 1 year old clear cut to 100 percent, we can see that there were about 9,8-14,6% of the 1 year old seedlings in the 3 years old clear cuts and only about 3,6-7,4% of the seedlings number that appeared in the 1 year old clear cut in the 4 years old clear cuts. The seedlings of one year old makes only about 6,7-10,7 % average in the 3 years old clear cuts and only 3,6-6,4 % from the total number of seedlings in the 4 years old clear cuts. It is evident that the main sowing of the clear cuttings from the forest edge occurs (copper pinewood) during the first two years after the felling and scarification and in the year four this process is insignificant. The results let to conclude that it was not expedient to wait for the sowing of the clear cutting from the forest edge longer then 3 years. Significantly higher density of pine seedlings 5 m from the forest edge in the 1-4 years old clear cuttings was registered in the areas where the cropper pinewood was from the west side and the smallest density in the areas where the crepper pinewood was on the east (F=12,28 p<0,001) (Fig. 3). The significant difference was also registered between the density of seedlings near the western and northern forest edge. The difference on seedlings densities near the western and eastern forest edges was also significant at 20 m distant from the forest edge in the 1-4 years old clear cuttings (F=8,03 p<0,001) (Fig. 3).
Northern forest edge exposition Eastern forest edge exposition Southern forest edge exposition Western forest edge exposition
20000 18000 16000 14000 12000 10000 8000 6000 4000 2000 0 5 20 40 60 Distance from forest edge, m Fig. 3. The relation between the density of self regenerated pines and the distance from edge of old pine stand and their exposition in 1-4 yrs old clear-cuts. In the areas 40-60 m distant from the forest edge the differences in the seedling density was not significant and it didnt depend on the exposition of the forest edge. The average of seedlings density 5-20 m from the western forest edge were about 1,4-1,5 times higher then at the eastern forest edge (Fig. 3). As it was already mentioned in the methodology the research was made in the three site types with the quit different humidity regimes that determined the different thickness of litter. In the Na site types the litter thickness varied from 0 till 5 cm, in the Nb site types respectively 0-7 cm and Lb 6-15 cm. The results of the factorial regression analysis showed that the smallest seedlings density was in the Na site types. The seedling density in Na site types differs from the one in the Nb-Lb site types from 1,3-1,5 times (5 m distance from the forest edge) till 3,5-3,7 times (40 m from the forest edge) (F=7,83-38,11; p<0,001). Even if the seedling density in the Lb site types were usually a little bit lager then in the Nb site types those differences were insignificant. Under the analysis of the interdependence between litter thickness and the density of viable pine seedlings in the 1-4 years old clear cuttings in the Na, Nb and Lb site types with unmanaged soil the positive as well as the negative influence of litter was stated. A thin (1,5-4 cm) litter in Na site type had a positive influence to pine regeneration in the non scarified soil (protects the soil from desiccation, forms a favourable microclimate for the seeds germination), but when the litter thickness was more than 4 cm the noticeable decrease of the seedlings density was observed in the Na and Nb site types. No noticeable differences between seedlings density have been registered in the Lb site types on non scarified soil with the litter of 6-15 cm. Those results partly controverts the findings of some other researchers ( Алексеев and Молчанов , 1940 ; Кищенко et al., 1969; Urbaitis, 1998) that no viable seedlings were being observed with the litter thickness more than 4-6 cm. In our case from 1,9 to 3,7 thousands of pine seedlings in a hectare were found near the forest edge (even excluding the seedlings of 1 year old) with the litter thickness of 6-15 cm. The green soil cover has a negative influence to the density of viable seedlings. While the competition of grass cover increased, the density of viable seedlings in the 1-4 years old clear cuts decreased (even though salutatory). It is more noticeable in the older clear cuts (3-4 years old) on 5-20 m distant from the forest edge. The grass cover influence amount and survival of 1-2 years seedlings the most in 3-4 years old clear-cut. While grass cover aggressiveness in 3 and more scores, pine seedlings were hardly detected. Three and particularly four year old seedlings are much less influenced by grass cover aggressiveness because of they parameters. They easier share neighborhood with grass, but were less frequent detected just in dense spice ( Calamagrostis Adans. particularly) and broadleaved grass groups. The varietal consist analysis of the underbrush showed that in the clear cuts of Pinetum vaccinio-myrtillosum and Pinetum myrtillosum dominates the Frangula alnus Mill., Sorbus aucuparia L., Juniperus communis L. and Salix L. were found more rarely. In he clear-cuts of Pinetum vacciniosum - Juniperus communis L. and Frangula alnus Mill. were observed. Though in separate accounting areas underground amount reached even up to 1,5 units per m 2 , and soft deciduous up to -5,5 units per m 2 , but in the 1-3 years old clear cuts they did not have any noticeable negative impact to the pine seedlings (because of the comparatively small amount and parameters). A soil preparation was one of the crucial factors that determines the density of self-regeneration, although its importance may vary in different forest site types. In general, in 1-4-years-old clear-cut sites, the density of self-regenerated pines in microsags were 2,63,6 times greater than in unmanaged soil and 5,47,2 times greater than in microsags, accordingly to a distance from the forest edge (Fig. 4).