INTRODUCTION
European forests cover about 215.106 ha of territory and over the past 25 years, they continue to expand (FOREST EUROPE, 2015). This makes Europe one of the richest forest areas in the world. Forests in Bulgaria are a part of the European and global forest wealth. Bulgarian forests provide about 85% of the water flow in the country or around 3.6.109 m3 resource of clean drinking water. They have a significant role in reducing greenhouse gas emissions by accumulating carbon in biomass and actually absorbtion some of the CO2. Lands and forests from the forest fund of Bulgaria retained over 80% of protected plants and over 60% of endangered species in the country. Forests are an important factor in erosion control, recreation and economic resource. In recent years, the total area of forest areas is constantly increasing and by the end of 2013 it amounted to 4,180,121 ha, or 37.7% of the country. Forest areas included in the European ecological network Natura 2000, is about 58 % of the total forest area. From 1990 to 2013 the total area of forest areas has increased by 407 628 ha or 10.8%. The average age is 51 y. The areas with deciduous forests dominate – by 69.8%, while the coniferous occupy 30.2% of the forest area (Executive Forest Agency, 2014).
Comparative analyzes of eustress using a wide range of climatic and dendrohronological data with data descriptions, meta-data types were published for: P. sylvestris L. — 1007 chronologies of 28 locations; P. nigra Arn. — 682 chronologies of 29 locations; F. sylvatica L.- 325 chronologies of 10 locations; Quercus rubra L. and Q. robur L. — 428 chronologies of 14 locations; Quercus petraea (Matt.) Liebl. — 255 chronologies of 13 locations; Quercus frainetto Ten., Q. cerris L. and Q. dalechampii Ten. — 136 chronologies from 6 locations in the region of Sofia and reserve «Sokolata»; Quercus frainetto Ten. and Q. cerris L. — 108 chronologies in 5 locations of SCI «Western Stara Planina» (Lyubenova, 2014abc; Lyubenova et al., 2014abc; 2015b). According to the laboratory for research on forest tree resources (LERFoB) over the past five years have been published studies related to the effects of drought in the stands of oak and pine (Toigo et al., 2015) and the sensitivity of Q. petraea forests to climate change in northern France (Merian et al., 2014) etc.
Durmast oak (Quercus dalechampii) and sessile oak (Quercus petraea) are taxonomically and ecologically similar trees. According to Delipavlov et al. (2011), there are well defined taxonomic differences between two oaks. Durmast oak is lower compared to the sessile oak with a height of 30 m, the leaves are smaller (up to 15 cm long and 5 cm wide), and the widest in the middle, seldom above the middle, rarely extended to top, evenly distributed in the branches and the lamina is chopped. Another researchers as Di Pietro et al. (2012) concluded that Quercus dalechampii was being comprised of specimens belonging both to the Q. pubescens and Q. petraea species complexes. According to the lectotype designated herein, which they established, the name Q. dalechampii was being properly applied to a species in the
- pubescens complex. Also all records of Q. dalechampii defined it as a species taxonomically close to Q. petraea. Di Pietro et al. (2012) reported that from various southeastern European countries had confusion and incomprehension with Q. petraea, which is step back for the dendroecology.
Acording to Euro-Med Plant base ) Q. dalechampii is a native to southeastern Europe: Italy, Greece, the Balkan Peninsula, Austria, Hungary, Slovakia, and the Czech Republic. Also Q. petraea is a native to the most of Europe, Anatolia and Iran. The natural area of durmast is limited by the range of sessile oak. It occurs in Europe without most northern, the southern and the eastern parts. In southern Europe, reaching up to 1800 m asl.
Oak forests in Bulgaria occupys an area of 917.103 ha, which represents 24% of the total forest area in the country. By Jordanov (1966) Quercus dalechampii is wide spread in Bulgarian mountains up to 1500 m a.s.l. and covers large areas (450 000 ha) in Rhodopes, Stara Planina, Sredna Gora, Osogovska Planina, Vlahina, Maleshevska Planina and Ograzhden. The participation of Quercus petraeae in communities increases mainly on northern exposed weter terrains and with the increase of altitude and on different inclinations. The forests of Quercus dalechampii are a part of mesophytous microtermal broadleaf native forest vegetation in Bulgaria. They form the hornbeam-durmast forest belt that sometimes enters in the beech belt (Bondev, 1991 Filipova & Asenov, 2016). The durmast wood is core and physico-mechanical properties depend of site conditions and the age of the trees. The wood of durmast and sessile oak has the same application. The forests of durmast and sessile oak are important for the structure of the forest fund in Bulgaria and occupy a worthy place in the forestry sector. Of course, besides the economic benefits, it is important to note also the contribution to the formation of specific habitats, for the conservation of biological and landscape biodiversity, ecosystem services, etc. However, all information relating to the inventory of forest areas of sessile and durmast oaks and monitoring in Bulgaria is attributed only to sessile oak.
The purpose of this study is the identification and evaluation of eustress periods, comparative analysis of forests in the studied locations and on the role of climatic type and climatic pattern for the eustress manifestation.
OBJECT AND METHODS
The total number of included in the analysis series is 286 from 14 European locations: 255 of Quercus petraea (Mattuschka) Liebl. from the International Tree Ring Data base (ITR, table 1) and 31 of Quercus dslechsmpii Ten. from Bulgarian location — village of Dolni Pasarel, DGS Sofia after exploring the Forest Management Plan (FMP, 2009) (Tabl. 2, Fig. 1).
Table 1. Characteristics of sampled locations and studied series
Table 2. Characteristics of durmast oak’s sampled location
| № | Division | Lat.* | Long. | Alt., m | Exp. | Soil | Tree** layer | Under growth | Origin | Age | Bonitos |
| 1 | 597- л | 42°31′ | 23°32′ | 800 | N | Dystric Cambisols | Cb 5
Qd 3 Fs 2 |
Qd 8
Qc 1 Qf 1 |
Cop. | 60 | 2
3 1 |
| 2 | 597- т | 42°31′ | 23°32′ | 900 | N | Dystric Cambisols | Qc 4
Qd 2 Ps 2 Pn 1 Cb 1 |
Qc 4
Qd 3 Qf 2 Pn 1 |
Cop.- Plant. | 60
50
60 |
3 |
| 3 | 597- х | 42°31′ | 23°32′ | 850 | W | Dystric Cambisols | Qc 5
Qd 3 Qf 1 Ps 1 |
Qc 5
Qd 3 Qf 2 |
Cop.- Plant. | 50 | 2 |
| 4 | 601- щ | 42°31′ | 23°30′ | 800 | NE | Dystric Cambisols | Qc 7
Qd 3 |
Qc 8
Qd 2 |
Cop. | 60 | 3 |
| 5 | 598- м1 | 42°33′ | 23°31′ | 900 | N | Humic Cambisols | Qc 7
Qd 3 |
Qc 7
Qd 3 |
Cop. | 60 | 3 |
* BGS 2005 – abbreviation for the Bulgarian Geodetic System, 2005 г.
** Cb — Carpinus betulus, Fs – Fagus sylvatica, Ps – Pinus sylvestris, Pn – Pinus nigra, Qd –nQuercus dalechampii, Qf – Quercus frainetto, Qc – Quercus cerris.
Fig. 1. Durmast oak’s sampling areas on topographic map
According to the climatic zoning (Velev, 2002), the place of sampling falls within the temperate region, climatic region of Ihtiman and Sredna Gora. Tav is between 7.6 and 10.6 0C, Tmax — 29.7 and 38.5 0C, Tmin — from 21.3 to 31.8 0C; Pav — 650-800 mm, with maximums in May-June and minimums in January-March; days with snow cover are from 48 to 82 in number. The vegetation period is 156-186 days. According to soil-geographical zoning of Bulgaria (Ninov, 2002), sampled plots falls in the Mediterranean region, Mediterranean-Balkan subregion, Sofia, Kraishte province. The soil in the sampling points is mostly brown transition (597 devision), and brown dark (601 devision). Both soil types belong to class Cambisols (Metamorphic) occupying mainly middle belt of all Bulgarian mountains with altitude of 700 — 800 and 1600 — 1800 m. The brown soil in transitional object of study is with homogeneous characteristics: low power humus horizon, well stocked with humic substances; a weakly acidic to neutral; sandy clay; medium stony; loose; medium deep and fresh. It is formed on sandstone and on it are formed medium rich habitat type C-2/30 /. Dark brown soil in 601devision is sandy loam, slightly stony, loose, deep and fresh to moist. It is formed on conglomerates and well supplied with humic substances, nitrogen and phosphorus oxides favor the formation of a medium rich in a rich habitat type SD — 2.3 / 29 / — Table 2.
According to floristic zoning (Flora of the R. of Bulgaria, 1963) the place, where the durmast samples were taken, falls in Vitosha region, with mesophytic and xeromesophytic vegetation type (Velchev 1997). According to the «forest vegetation zoning in Bulgaria» (Zahariev et al., 1979) the place of sampling falls in Moesian forestry district, sub-Kraishte Ihtimanska region. The communities belongs to the Middle Belt mountain forests of beech and pine (600-1800 m alt.) and in subbelt of foothill forests of durmast, beech and fir (600-1000 m alt.).
The disks were cut from the stems of first Kraft’s class trees on the height in the range of 1.0 to 1.50 m. The tree rings width was measured by LINTAB ™ 5 and program TSAP- Win™ with precision 0.0001. After cross-dating (to eliminate possible false measurement of rings and a gap in the formatiing years), received 31 sequences were included in the analyse. Anticipate further analyzes were performed with the application SPPAM 2.0 (Lyubenova et al., 2014) and include: 1) Identification and analysis of eustres years in trees – years of proven statistically reduced stem growth; 2) Statistical analysis of eustress years through indicators: Cov, Card, K and Ct. «K» – coefficient was calculated as the ratio between the number of included years in analysis (period) and the number of eustress years (SY). Cardinality (Card) is the number of series with established eustress for the same year. «Ct» — coefficient was calculated as the ratio between Card and the total number of studied series from one location (n), and the coverage (Cov) — as the ratio between Card and the number of investigated series that have the same periods; 3) Analysis of the quality of eustress for locations and species. The quality of eustress was assessed by duration (D), frequency for100 years (F), and depth of eustress (A) by creating a 5-graded scale. The duration of eustress (D) is a number of adjacent eustress years in the series. The frequency of eustress (F) is the number of stress years for 100 years. The depth of eustresa (A) was calculated by the formula:
where It are indices of growth, in which is established eustress; 4) Indentification of climatic types (CT) for the years from the period (determined by age of the forest); 5) Analysis of adverse climatic types and corresponding years (eustress years), AY.
The climatic of year (CTY) describes the deviation of the mean annual temperature (Tav) of climatic norms for the temperature (dT) and the deviation of the average annual precipitations (Pav) from climatic norms for precipitation (dP). Climatic norms of temperatures are calculated as Tav ± μti for 30-year periods. Climatic norms for precipitation are calculated as Pav ± μpi for 30 periods, μ = 1.96 σ / (√ N), where σ is the standard deviation of the mean values of T and P; μti and μpi are calculated by level of significance, α = 0.05. The set of CT are: hot (H) — dT> μti; cold (C) — dT <-μti; wet (W) — dP> μpi; dry (D) — dP <-μ pi and with normal (N) average annual temperatures, when -μti ≤ dT ≤ μti, or normal average annual precipitation, when -μpi ≤ dP ≤ μpi. Analysis of climatic patterns (models) representing sequential alternation of CTY for three-year periods (climatic type of the year in which is established eustress and climatics of two years before it). This analysis is necessitated by the fact that biological systems, incl. trees, react with a delay, ie relevant for their reaction are the weather at least two years before the year, in which it is observed eustress.
As a source of data on temperature and precipitation was used climatic database CRU — TS ), which relate to the period from 1901 to 2009. For this period, an analysis of the impact of climate change on stems growth was examined.
In Bulgaria, durmast oak takes part in the formation of four types of habitats listed in Annex I of 92/43 / EEC Directive on the conservation of natural habitats and of wild fauna and flora: 9170. Oak — hornbeam forests such Galio-Carpinetum, 91M0. Balkan — Pannonian-sessile oak forests, 91G0.* Pannonian woods with Quercus petraea and Carpinus betulus and 91I0.* Euro — Siberian forests with Quercus spp. (Kavrakova et al., 2009; https://natura2000.moew.government.bg/Home/Reports?reportType=Habitats). Studied durmast oak communities relay to 91M0 and 9170 (for subdivision 597- л) habitats.
RESULTS AND DISCUSSION
The resulting models, describing growth patterns in the locations, are polynomials of 6 and 7 degree, and with high level of approximation, R2 is between 0.85 and closed to 1. The analysed 31 sries of durmast oak are with EPS> 0.85%. The cross dating and standardized durmast serries were added to the database and further analysis was made with data for sessile oak from other European locations, because we don’t have other dendrohronological data. After performing correlation analysis of the estimated serries of indexes by locations, the weak to moderate correlation and autocorrelation of 0.50 to 0.67 was obtained. The presence of correlation between the series of indices indicates the presence of analogue environmental signals in sequences. The averaging of indices for each year of series by locations, the model serries of indices were received that characterize the influence mainly of environmental factors (not age) on the radial growth of stems — Fig. 2.
A.
B.
Fig. 2. Dynamics of average growth index (It) of sessile oak, 1895-2009 (A) and durmast oak (B) by locations
During the growth period 1895 — 2009, the index of average model sequences of sessile oak in European locations (Table. 4) shows uneven progress. In five periods it was clearly above
1: from 1902 to 1907; 1913 — 1922; 1931 — 1939; 1949 — 1955; from 1959 – 1974. After 2000 year, a gradual improvement of growth was also realized. Three negative growth periods, where the growth index fell under 1.0 exsisted: from 1908 to 1912; 1940 – 1945 and 1956 — 1959 (Fig. 2). The established adverse periods were published for other tree species and locations (Lyubenova, 2012). The average model index sequences of durmast oak showed growth index variation relatively without major deviations for the period 1955 – 2009. The estimated average parameters for the comparative characterization of average (model) index chronologies in locations are presented on Table 3.
Table 3. Characteristics of the series of indices sessile oak in locations
| Location
№ |
Period (P), y | It av | ± µav | SY, n | Card | Cov | Ct=Card/N | K=P/SY |
| 1 | 161 | 1.012 | 0.045 | 39 | 5.9 | 0.7 | 0.5 | 4.1 |
| 2 | 154 | 1.005 | 0.045 | 45 | 6.8 | 0.8 | 0.5 | 3.4 |
| 3 | 237 | 0.984 | 0.035 | 57 | 4.2 | 0.7 | 0.3 | 4.2 |
| 4 | 229 | 1.000 | 0.046 | 43 | 2.6 | 0.9 | 0.2 | 5.3 |
| 5 | 69 | 1.002 | 0.066 | 11 | 13.8 | 0.9 | 0.6 | 6.3 |
| 6 | 158 | 1.001 | 0.054 | 40 | 10.1 | 0.7 | 0.6 | 4.0 |
| 7 | 157 | 1.002 | 0.048 | 48 | 5.6 | 0.8 | 0.4 | 3.3 |
| 8 | 193 | 1.006 | 0.039 | 45 | 6.5 | 0.7 | 0.5 | 4.3 |
| 9 | 147 | 1.016 | 0.053 | 47 | 2.4 | 0.8 | 0.2 | 3.1 |
| 10 | 193 | 1.003 | 0.036 | 37 | 16.1 | 0.8 | 0.4 | 5.2 |
| 11 | 199 | 1.060 | 0.067 | 47 | 5.5 | 0.7 | 0.4 | 4.2 |
| 12 | 152 | 0.997 | 0.042 | 45 | 5.2 | 0.7 | 0.4 | 3.4 |
| 13 | 61 | 1.107 | 0.157 | 13 | 9.7 | 0.6 | 0.3 | 4.7 |
| 14 | 401 | 1.002 | 0.046 | 45 | 18.4 | 0.7 | 0.3 | 8.9 |
The calculated values of tree ring width almost completely relate to the measured values. The average growth index (It) ranged from 1.012 to 1.002. For locations of durmast oak (№ 13) it is 1.107, but with the greatest confidence interval (± 0.157) in comparison with studied sessile oak serries. The number of statistically proven periods of low growth (SY, eustres periods) for different locations ranged from 11 to 57, and for durmast oak location it was 13, ie eustress periods tend to lower limit than those in sessile oak. Cardinality (Card) of eustress periods in sessile oak ranged from 2.4 to 18.4 for samples from different locations and for durmast oak, it was 9.7. The measurements of durmast oak come close to the mean measured values of sessile oak. Coverage (Cov) for sessile oak series ranges from 0.7 to 0.9, and for durmast oak is 0.6, ie without the obtained interval for studied locations of sessile oak. The Ct — coefficient for sessile oak series ranges from 0.2 to 0.6, and for durmast oak series is 0.3, ie within the obtain interval for studied locations of sessile oak. K — coefficient ranges from 3.1 to 8.9 for studied serries, and for durmast oak it is 4.7, ie it is close to the average values. The used coefficients make it possible to compare different in length series and series that cove different periods. The lower obtained values are probably due not only to the peculiarities of the series, but may be to a smaller number in the sample of location.
The average depth of eustress (A) ranged from 0.199 to 0.370, as for surveyed location of durmast is 0.240. The maximum values for the depth were observed in different years for communities in different locations. For location of durmast oak the maximum is 0.327 and is observed in 1967. The average duration of eustress periods (D) is from 2 to 3 years for the relevant locations and maximum values range from 4 to 9 years and the similar periods were observed by locations. For the location of durmast oak Dmax was four years and is established for the period 1995-1998. Average frequency of occurrence of eustres for 100 years (F) varied from 11 to 30 years, while their number for durmast was 21 — Table 4.
Table 4. Eustress characteristics for studied series and locations
| Location/ Eustress characteristic |
Aav |
Amax |
Y, Amax |
Dav |
Dmax |
Y, Dmax |
Fav, 100 y |
PFT |
| 1 | 0.201 | 0.361 | 1923 | 3 | 8 | 1949 — 1956 | 23 | F3D3A1 |
| 2 | 0.244 | 0.489 | 1996 | 3 | 6 | 1937 — 1942 | 29 | F4D3A3 |
| 3 | 0.206 | 0.422 | 1923 | 3 | 9 | 1936 — 1944 | 24 | F3D3A1 |
| 4 | 0.237 | 0.533 | 1959 | 2 | 7 | 1937 — 1943 | 18 | F1D3A3 |
| 5 | 0.370 | 0.584 | 1940 | 3 | 4 | 1939 — 1942 | 15 | F1D4A5 |
| 6 | 0.314 | 0.561 | 1959 | 2 | 8 | 1956 — 1963 | 25 | F3D2A5 |
| 7 | 0.212 | 0.465 | 1909 | 2 | 7 | 1917 — 1923 | 30 | F4D2A2 |
| 8 | 0.210 | 0.407 | 1948 | 2 | 7 | 1906 — 1912 | 23 | F3D2A2 |
| 9 | 0.275 | 0.599 | 1909 | 3 | 9 | 1907 — 1915 | 31 | F4D5A5 |
|
10 |
0.199 |
0.355 |
1981 |
2 |
4 |
1915 — 1918
1945 — 1948 |
19 |
F1D1A1 |
|
11 |
0.265 |
0.561 |
1942 |
3 |
6 |
1925 — 1930
1954 — 1959 1985 — 1990 |
23 |
F3D3A4 |
|
12 |
0.219 |
0.494 |
1942 |
3 |
6 |
1925 — 1930
1956 — 1961 |
29 |
F4D3A2 |
| 13 | 0.240 | 0.327 | 1967 | 3 | 4 | 1995 — 1998 | 21 | F2D3A3 |
| 14 | 0.221 | 0.352 | 1984 | 2 | 8 | 1943 — 1950 | 11 | F1D1A2 |
Fig. 3. Variation of eustress characteristics by locations
After statistical processing of data available for all locations of sessile oak, the scale for assessing the eustress periods in frequency, duration and depth was established — Table 5.
Table 5. Five-graded scale for assessment of eustress characteristics
| Frequency (F) | Duration (D) | Depth (A) | ||||||
| Group | Name | Value | Group | Name | Value | Group | Name | Value |
| 1 | Very rarely | ≤19.1 | 1 | Very short | ≤2.1 | 1 | Very small depth | ≤0.207 |
| 2 | Rarely | >19.1 —
≤22.1 |
2 | Short | >2.2 —
≤2.3 |
2 | Small depth | >0.207 —
≤0.223 |
| 3 | Normal | >22.1 —
≤28.1 |
3 | Normal | >2.3 —
≤2.7 |
3 | Normal depth | >0.223 —
≤0.254 |
| 4 | Offen | >28.1 —
≤31.2 |
4 | Long | >2.7 —
≤2.9 |
4 | Deep | >0.254 —
≤0.270 |
| 5 | Very Offen | >31.2 | 5 | Very Long | >2.9 | 5 | Very Deep | >0.270 |
The scaled frequency, duration and depth of eustress of durmast oak in studied location and period showed that it can be attributed to functional type (PFT) F2D3A3, ie with rarely occurring eustres that are with normal duration and depth — Table. 4. For the period of study, there is no risk for the communities of tree species.
The sessile oak in studied locations can be attributed to the functional types presented in table 4. In 5 of the surveyed locations of sessile oak (4, 5, 6, 7 and 8) there is a risk of degradation of the communities that must be considered in their management. These are the reactive types: F1D4A5 (4) – the eustress periods were long and very deep, although with very rarely appearence; F3D2A5 (5) – the eustress periods were with normal appearance and short, but very deep; F4D2A2 (6) – offen appeared, short and with small depth eustress periods and F4D5A5 (7) – offen appeared very long and very deep eustress periods.
In the climate, determining the growth of sessile oak in most of its locations studied (7) for the period 1901-2009, the hot and dry years were with the greatest participation (HD): 3 (19.64%) 4 (18.60%) 7 (16.67%) 9 (21.28%) 14 (27.27%), partly at location 11 (14.89%). Dry,
but with temperatures in climatic norms (ND) prevailed in location 1. For 4 locations prevailed cold and wet climatic types (CW) — location: 5 (27.27%) 8 (20.00%), 11 (14.89%) or humid with temperatures in the climatic norms (NW) — location 2 (20.45%). The cold and dry climatic (CD) had the highest participation in two locations (6, 10), respectively 22.50% and 18.92%, and the hot and humid type (HW) — only for location 12 (22.22%). For the durmast oak location, The CN, CW, HD and HW climatic types are with equal participation of 15.38% — Fig. 4, Table 6.
Table 6. Climatic types of years for the location of durmast oak
| Clymatic type | Years | |||||||
| CD | 1965 | 1985 | 1992 | 1993 | ||||
| CN | 1959 | 1964 | 1973 | 1982 | 1984 | 1996 | 1997 | |
| CW | 1969 | 1976 | 1978 | 1980 | 1991 | 1995 | 1998 | 2005 |
| ND | 1967 | 1983 | 1986 | |||||
| NN | 1962 | 1972 | 1974 | 1981 | 1987 | 2001 | 2003 | 2006 |
| NW | 1963 | 1971 | 1975 | 1999 | 2004 | |||
| HD | 1977 | 1989 | 1990 | 1994 | 2000 | |||
| HN | 1968 | 1970 | 2002 | 2008 | 2009 | |||
| HW | 1960 | 1961 | 1966 | 1979 | 1988 | 2007 | ||
| CD | CN | CW | ND | NN | NW | HD | HN | HW | |
| CTY/N | 8,00 | 12,00 | 16,00 | 6,00 | 16,00 | 10,00 | 10,00 | 10,00 | 12,00 |
| ACTY/SY | 9,09 | 18,18 | 18,18 | 9,09 | 9,09 | 9,09 | 9,09 | 9,09 | 9,09 |
| ACTY/CTY | 50,00 | 57,14 | 33,33 | 80,00 | 66,67 | 20,00 | 83,33 | 50,00 | 50,00 |
Fig. 4. The relative importance of climatic types for the presence of durmast oak eustress (%): a) CTY / N — the number of years of climatic type to the total number of years included in the analysis; b) ACTY / SY — the number of years of climatic type, which is set to eustress, to the total eustress years of different climatic types; c) ACTY / CTY — the number of years of climatic type, which is set eustress, to the total number of years of relevant climatic.
The ratio ACTY / SY showed that both climatic types CN (cold unfavorable years with rainfall in the climate norm) and CW (cold and wet unfavorable years) have had the highest significance for the durmast eustress of location (by 18.18% each, Fig. 4). When considering the ratio ACTY / CTY, the relatively most adverse years in the total number of years from relevant climatic type were of climatic types HD (warm and dry years) — 83.33% and ND (dry years with temperatures in the climatic norm) — 80.00%. The least adverse years in the total number of years from relevant climatic type were of climatic types — CW (cold and wet years) — 33.33% and NW (wet years with temperatures in the climate norm) — 20.00%.
Because biological systems show the postpone response to the impact and the impact accumulation, the analysis of climatic types influence two years before the eustress year were performed — Table. 7. The percentage contribution of each of climatic patern was of the range of 9.1%. For the occurrence of identified 11 eustress periods, the regimes in two previous years were of great importance. In 82% of the pattern cases, the eustress was observed in previous years — in both two previous years (37%), in the previous year (27%) or in the year befor the previous year (18%). In 73% of the patern cases, the eustress is associated with the maintenance of one or both regimes outside the climatic norms in three or two of the consecutive years of the climatic pattern. A change in one of two regimes — cold to warm (C to H) or vice versa; dry to wet (D to W), and back in one or three of the previous years provoked eustres in 55% of the cases.
Table 7. Climatic patterns: ASY – eustress year; SY-1 – CT for a year before ASY; SY-2 – CT for a year before SY-1
*”e” – eustress existence in previous year
CONCLUSION
The number of statistically proven eustress periods for sessile oak in different locations varied from 11 to 57 and for durmast they were 13. The established average depth (A) of eustress periods was 0.240. Тhis value was middle compared to the highest or lowest obtained values for the sessile oak in European locations. For other studied species and their locations it ranges from 0.2 — 0.5 (spruce and American oak) to 0.6 — 0.8 (fir, Black pine, Portuguese oak, Scots pine, Austrian oak, Hungarian oak and beech) (Lyubenova, 2012). For durmast оак location most adversely influenced climatic types CN (cold years with rainfall in the climatic norms) and CW (cold and wet years). For the location of durmast oak, the CN years were: 1959, 1964, 1973, 1982, 1984, 1996 and 1997, and CW years were: 1969, 1976, 1978, 1980, 1991, 1995,
1998, 2005. Pattern analysis showed that for the occurrence of obtained 11 eustress periods, the regimes in two previous years were of great importance. In 82% of the cases of eustress available in previous years it must also seen eustress. In 73% of pattern cases, the eustress was associated with maintenance of one or both of regimes outside the climatic norms in three or two consecutive years of the climatic pattern. The changes in one or two regimes in previous years also provoked eustress in 55% of the pattern cases.
The survey about the growth index and its characteristics to assess the tree species and their communities’ state is a reliable approach, because It values are effected from species specificity, characteristics of habitats and regional climate. The evaluation scales, in which e the characteristics of the growth index are used, are static and depend on the studied periods as well as on the used quantity of data. The much more promising indicator for assessment are statistically proven periods of redused radial growth (eustress periods). The innovation of conducted research includes: (1) processing of dendroecological data of Quercus dalechampii Ten. from Bulgaria; (2) The usage of SPPAM program for dendrochronological analysis and original statistical analysis on eustress and climatic influence on radial growth; (3) The development of five-graded scale for eustress characteristics evaluation; (4) The expression of reactive functional types of trees and (5) The investigation of climatic types and climatic patterns influence.
REFERENCES
Bondev I. Vegetation of Bulgaria. Map in 1: 600 000 scale with explanatory text. University press “Kliment Ohridski, Sofia, 1991. — 183 p. (in Bulgarian)
Delipavlov D., Cheshmedjiev I. Oredelitel plant in Bulgaria. Acad. Publ. House, Agronomy University, Plovdiv, 2011. — 60-62.
Di Pietro R., Visconi V., Peruzzi L., Fortini P. A review of the application of the name Quercus dalechampii. TAXON 61 (6), 2012. — 1311 – 1316.
Filipova E., Asenov А. Review on Quercus dalechampii Ten. and Quercus petraea (Mattuschka) Liebl. in the vegetation of Bulgaria. ANNUAL OF SOFIA UNIVERSITY “ST. KLIMENT OHRIDSKI” FACULTY OF BIOLOGY , BOOK 2 – BOTANY, Volume 100, 2016. — 105 – 112.
FOREST EUROPE Extraordinary Ministerial Conference. Мadrid, 21 October, 2015. Jordanov D. Flora of the People’s Republic of Bulgaria, vol. 1, 1963 — 508 p.
Jordanov D. Florae Republicae Popularis Bulgaricae, vol. 3, BAS Publishing house, Sofia, 1966. — 116-120 (in Bulgarian).
Lyubenova M., Chikalanov A. Software implementation for stress period studies applied to dendrocronological analyses of g. Quercus L. Comptes rendus de l’Academie bulgare des Sciences, Biologie, ecologie, t. 63, № 3, 2010. — 409-418.
Lyubenova M. Plant trees functional types (PFTs) in the particular circumstances of the periods of low growth (eustress periods). Publishing house «PablishSaySet-Eco», Sofia, 2012. – 276 p.
Lyubenova M. Comparative Assessment of European Black Pine Tree Ring Width Series for Eustress and Risk Identification in Different Locations. Indian Journal of Applied Research, Vol.4, Issue 9, 2014a. — 253-258.
Lyubenova M. Survey about Climatic Type of Years and European Black Pine Eustress. Indian Journal of Applied Research, v. 4, iss. 11, 2014b. — 43-46.
Lyubenova M. Holistic Analysis on Eustress of Quercus rubra L. and Quercus robur L. Journal of Balkan Ecology, vol. 17, № 4, 2014c. — 391-401.
Lyubenova M. Chikalanov A., Lyubenova V. An example of holistic approach for analysis of periods with low stems growths and their application. Comptes rendus de l’Acadеmie Bulgare des Sciences, Biologie, ecologie, t. 67, No 4, 2014a. — 541-550.
Lyubenova M., Georgieva N., Lyubenova V. Assessment of Oak Dendrochronological Series in Protected Zone (Bulgaria) for Eustress Identification in Forest Stands. International Journal of Agriculture Innovations and Research, vol.3, iss. 1, 2014b. — 116- 124.
Lyubenova M., Chikalanov A., Lyubenova V. Holistic Ecological Assessment of Dendrochronological Series as Source of Information for Tree Eustress (Example with Beech), International Journal of Environmental Monitoring and Protection, vol. 1, No. 1, 2014c. — 24-39.
Lyubenova M., Chikalanov A., Lyubenova V., Vatov St. SPPAM 2.0 – Scientific description and Use. Journal of Environmental Science, Computer Science and Engineering & Technology, Sec. B, vol. 4, №1, 2015а. — 37-51.
Lyubenova M., Peteva S. Eustress assessment of Quercus petraea (Matt.)Liebl. Dendrochronological Series. Journal of Balkan Ecology, vol 18, № 2, 171-181.
Mérian, P., Bergès, L., Lebourgeois, F. 2014. Variabilité spatiale de la réponse au climat du Chêne sessile dans la moitié nord de la France. — Revue Forestière Française, vol. 56, n° 2, 2014, 2015b. — 107-123.
Mérian P., Lebourgeois, F. Le statut social d’un arbre influence-t-il sa réponse au climat ? Etude dendroécologique sur le Sapin, l’Epicéa, le Pin sylvestre, le Hêtre et le Chêne sessile. Revue Forestière Française, 65, 1, 2013. — 7-19.
Ninov N. Soil geographical rayonirane- Geography of Bulgaria. ForKom, Sofia, 2002. 300- 303.
Ninov N. Taxonomic list of soils in Bulgaria, according to the FAO World magazine. Teaching Geography, iss. 5, 2005.
Strategic Plan for Forest Development 2014 — 2023 g. Executive Forest Agency – MAF, 2014.
Trouve R., Bontemps J.D., Collet C., Seynave I., Lebourgeois F. Growth partitioning in forest stands is affected by stand density and summer drought in sessile oak and Douglas- fir, Forest Ecology and Management, 334, 2014. — 358-368.
Toigo M., Vallet P., Tuilleras V., Lebourgeois F., Rozenberg P., Perret P., Perot T. Forest Ecology and Management, 345, 2015. — 73 — 82.
Velchev V. Types of vegetation. Geography of Bulgaria, Acad. Publ., 1997. — 269-283.
Velev St. Climatic zoning-In: Geography of Bulgaria. Physical geography. ForKom, Sofia, 2002. — 155-157.
Zahariev B., Donov C., Petrunov K., Masarov S. Forestry vegetable division of the Republic of Bulgaria. Zemizdat , 1979. – 197 p.
Table 1. Characteristics of studied locations and serries
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[schema type=»book» name=»Dendroecological Investigation of Sessile and Durmast Oaks from European Locations» description=»The investigation deals with dendrochronological analysis of serries (31) from Quercus dalechampii Ten. The tree rings were measured by LINTAB ™ 5 and TSAP- Win ™ program. Sessile oak serries (255) from 13 locations in Europe were included to create a scale for evaluation of frequency, duration and depth of eustress. The describing growth models are polynomials of 6 and 7 degree and R2 is up to 0.85. Calculated EPS is above 0.85%. The cross dating and standardized serries of durmast were processes together with the serries of sessile oak. The number of obtained eustress periods of sessile oak varies from 11 to 57 and for durmast they are 13. The average depth was established to 0.240. This value is middle compared to the highest or lowest values for the sessile oak in European locations. The prevaling climatic types in adverse years are CN (cold with normal precipitations) and CW (cold and wet) for durmas oak. The years: 1959, 1964, 1973, 1982, 1984, 1996 and 1997 was established as cold, while the years: 1969, 1976, 1978, 1980, 1991, 1995, 1998, 2005 — as cold and wet. The climatic patterns analyse (climatic type of eustress year and two years before it) showed that in 82% of the cases, the eustress existed in previous years. The mentaince of temperature or/and precipitations out of the corresponding climatic norms or the changes in types at least in one of the patterns years certainly provoke eustress.» author=»MARIYANA LYUBENOVA, SIMONA PETEVA, ALEXANDER MIHAILOV» publisher=»Басаранович Екатерина» pubdate=»2016-12-15″ edition=»euroasia-science_6(27)_23.06.2016″ ebook=»yes» ]