J. Danusevicius and R. Gabrilavicius

Lithuanian Forest Research Institute, Girionys, LT-4312 Kauno, Lithuania

Summary

Lithuanian forests cover an area of 1.86 million hectares. The total wooded area of the country is 30.1%. Coniferous forests comprise 61.6%, and spruce stands 24.2%. Native spruce stands make up more than two-thirds of their total area. Middle-aged and older stands are divided into three selection groups. The best (1st selection groups) spruce stands cover 41 000 ha. Genetic resources of spruce stands are conserved in situ and ex situ. Permanent inventory and assessment of genetic objects are carried out. Studies on phenotypic and genotypic structures of populations are conducted; adaptation, stability and selection effect of provenances and families, as well as changeability of traits, peculiarities of reproductive biology and hybridization are determined. Standards for conservation and utilization of genetic resources are being prepared.

Introduction

The Lithuanian forests are situated throughout the territory and cover an area of 1.86 million hectares. The total wooded area of Lithuania is 30.1%, in which coniferous forests comprise 61.6%, and spruce stands 24.2% (Table 1). During the last two decades, intensive reforestation has had a tendency to increase the area of spruce stands. Mature spruce groves are the most productive (285 m³/ha) of all stands growing in Lithuania while they suffer the most from negative natural and anthropogenic factors such as storms, droughts, insect pests, fungus disease, frosts, animal damage and, finally, industrial pollution.

In Lithuania, spruce stands are situated mostly in the western, northern and central parts of the Republic. Scots pine forests take up a large area but there are no clear big spruce forests. The forests of Rietavas-Taurage and Birzai are somewhat larger. The characteristics of spruce groves are presented in Table 2. The spruce groves of Piceetum myrtillosum and Piceetum oxalidosum forest types prevail in Lithuania. Mostly, mixed spruce stands with pine, birch and aspen are noted. Mixed spruce stands with birch and aspen produce about 650 m³/ha of timber at the cutting age. They distinguish themselves in better stability and resistance to storms.

The area of spruce stands in Lithuania has been decreasing continually (Fig. 1). True, it began to increase during the last two decades because of young stands. At present, young stands until 10 years of age make up 15.4% of the total area of spruce stands. It is known how many disasters the spruce groves suffer during their ontogenesis. Continually recurring storms (in 1967, 1982 and 1993) destroyed most spruce stands. Usually a big invasion of spruce bark beetles, which destroy what is left after windfalls in spruce groves, follows the storms. The latter process was particularly severe after the storm in 1992. One of the main measures at present being used in Lithuania for cleaning defaced and damaged spruce stands is to cut the damaged stands and remove the stem together with spruce bark beetles. It is impossible to determine the losses which we will suffer.

Another significant factor destroying the spruce stands is industrial air pollutants. According to the data of our specialists who are carrying out ecological monitoring activities (Ozolincius 1994), defoliation of spruce groves continually increases. For instance, in 1989 the spruce stands damage class was 0.7 while in 1994 it was 1.1. General spruce stand defoliation level at present comes to 21.7%.

At present the spruce stands of natural origin in Lithuania make up more than two-thirds of total spruce forest area. Annual spruce cutting woodlots consist of 2000 ha on average and the stands of natural origin are cut. Therefore, the situation of the natural spruce grove genofund will change owing to the artificial reforestation. The necessity arose to conserve the valuable natural genofund of spruce as well as of other tree species.

Main Norway spruce populations and their status

Six natural forest regions are selected in Lithuania in which different populations of separate tree species, among them Norway spruce, have formed. The main object of forest tree selection is natural populations, because populations are a primary link of genetic information. Valuable genotypes which are adapted to the local conditions are best and genotype conglomeration forms in natural stands, while the crossing of separate individuals acts as natural selection under certain environmental conditions.

Elucidation of population bounds is a long and intricate process but it is possible to choose and evaluate the populations most distant from each other and separate due to the climatic differences and origins of specific structural traits.

Diversity of genofund decreases because the area of stands of artificial origin increases, reforestation does not always use the seed of the best trees and sometimes there are separate genotypes of low value. All potential elements of a genofund participate in reproduction of new generations in naturally formed autochthonic stands.

At present there are no big spruce forests in Lithuania. They are situated in the western, central and northern parts of the Republics and divided by larger or smaller deciduous stands. Larger spruce groves remain in four parts of the country and make up the following spruce accumulations: southwestern Zemaitija, northeastern Zemaitija, forest of Birzai and central southern part. However, these spruce stands are cut by woodlots and damaged by windfalls. There are some spruce stands in other parts of Lithuania as well but they do not form big forests. Mostly, they are mixed with big forests of other tree species. Therefore, it is necessary to conserve the genofund or remaining spruce groves and to utilize them rationally in reforestation (Gabrilavi…ius and Pliura 1993).

At present, the following best Norway spruce populations are selected in Lithuania: Survilai (1st forest natural region); Rokiskis (2nd forest natural region); Ignalina (3rd forest natural region); Mociskis (4th forest natural region); Sakiai, Kazlu Ruda, Punia (5th forest natural region); Trakai (6th forest natural region). Investigated populations differ significantly in most structural traits. Height differences of separate populations make up 21.4%, and ones of crown width comprise 35.8%.

It is important to ascertain the limits of population transfer, using them to establish new spruce stands. The influence of environmental conditions on trait variability must be studied, and the progenies transferred into new ecological conditions; other studies include determining the influence of genetic characteristics (Gabrilavi…ius 1992).

Ecological adaptability of populations is the genetic result of different reactions of each population to site fertility, humidity and micro- and macroclimatic conditions so it is possible to get additional selection effect by selecting specifically adapted populations.

Studies have evaluated reliable growth and adaptability differences between some Lithuanian Norway spruce populations (Danusevi…ius 1993; Gabrilavi…ius 1992). Adequate populations (their progenies) are being recommended for reforestation in every forest natural region.

In the winter of 1993 the storm turned a significant part of the spruce stands upside down. A dry summer followed and also in 1994 was an unforeseen drought. For this reason, the spruces became significantly weaker and the pest Ips typographus has spread. At present, there are 60 000-70 000 ha of spruce stands being damaged by the abovementioned pest; this area makes up 32-38% of middle-aged and older stands. It is planned to clear-cut an area of 35 000-40 000 ha of the damaged spruce stands, which represents more than a 2-year cutting rate.

Methods to conserve genetic resources

Primary evaluation of forest genetic resources is carried out during forest inventory, when middle-aged and older stands are divided into three selection groups: Group ICstands of Ia and I bonitet, high productivity and quality, healthy, normal thickness; Group IICstands of II-III bonitet, average productivity and quality; Group IIICstands of IV and lower bonitets, low productivity and quality. At the present moment, Lithuanian middle-aged, premature and mature spruce stands are of good selection value (Tables 3 and 4). Stands of the Group I cover 41 000 ha, or 22% of the area of middle-aged and older spruce stands (Kenstavi…ius and Brukas 1993). They make up the most valuable genofund of Lithuanian spruce stands, and therefore more attention is paid to their conservation and regeneration. In Lithuania two methods of genetic resources conservation are applied:

C genetic reserves, when highly valuable stands are singled out and conserved up to natural maturity, allowing the removal of dying or damaged trees, to fight against pests and to protect the main species from overtopping by others; natural regeneration is used,

C plus (elite) individual trees, when individual trees are supervised and kept until their death, while progenies are transferred into archives or plantations,

C seed orchards, when the stand is left until maturity, and the seed crop is gathered from standing trees. Regeneration is natural.

 

C clone archives, when 15 ramets from each clone are grown in special sites,

C seed clone orchards,

C test plantations from plus (elite) tree seeds or genetic reserves and seed sites.

Data presented in Table 5 are from work carried out in the field of genetic resources conservation. In agreement with the Law of Lithuanian Forests, genetic reservations in the future will acquire the status of genetic reserves, because in the first case man's interference is prohibited. Genetic reserves comprise 0.5% of the total area of middle-aged and older spruce stands (Baliuckas et al. 1994).

This year additional selection is still foreseen, while damaged ones will be reassessed. Additional seed reserves also will be singled out. At present, standards for selection, management and utilization of the abovementioned conservation objects of genetic resources are being specified and therefore an international experience here would be of great help.

Some plus trees are dead or damaged, and therefore in the near future their additional selection and evaluation will be carried out. Clones of most of dead plus trees are concentrated in archives, so that their genotypes are not lost.

At present, studies on genetic resource are conducted by the Lithuanian Forestry Research Institute. Owing to long-term isolation from West European countries and inadequate financing, investigations were carried out on a small scale and slowly. The works that have been and are being carried out can be divided into two groups: fundamental and applied (Table 6).

More detailed studies were performed concerning phenotypic and genotypic structure of populations, selection efficiency of provenances and families in situ and ex situ, including adaptability and stability indices; investigations of genotype by environmental interaction and geographical changeability, as well as peculiarities of reproductive biology in seed orchards and interspecific as well as intraspecific hybridization.

In the field of applied sciences, recommendations and standards for stand selective evaluation, for selection of plus trees, genetic and seed reserves, as well as for establishing seed orchards and clonal archives, and for increasing seed crop productivity, have been prepared.

It is foreseen to continue the inventory of forest genetic resources, studies and compiling of catalogues, work on tree assessment and genotype identification, as well as to work out criteria for the selection of plants under conservation.

The quality and extent of these works depends considerably upon international collaboration which is carried out by the International Plant Genetic Resources Institute, and upon our united efforts in the EUFORGEN programme, as well as on financial support.

Baliuckas V. et al. 1994. Forest genetics and breeding in Lithuania. Information publication, Girionys, 30 p.

Danusevi…ius J. 1993. Growth peculiarities of Norway spruce provenances and families in Lithuania. Pp. 38-43 in Proceedings of IUFRO (S 2.2-11) Symposium, Latvia, 1993.

Gabrilavi…ius R. 1992. Adaptation of spruce populations and effectiveness of selection. Exp. Biol. 3-4 (Vilnius "Academia"):35-36.

Gabrilavi…ius R. and A. Pliura. 1993. Breeding of Norway spruce in Lithuania. Pp. 189-192 in Proceedings of IUFRO (S 2.2-11) Symposium, Latvia, 1993.

Kenstavi…ius J. and A. Brukas. 1993. Lietuvos misku pakartotinio tvarkymo augimvieciu pagrindu rezultatas ir naudojimo perspektyvos [Results of rests on basis of sites and perspectives of their usage]. Kaunas, 527 p. [In Lithuanian].

Ozolincius, R. 1994. Forest condition assessment in regional network of forest monitoring. Annual report of Lithuanian Forest Research Institute, Kaunas-Girionys.

Contact EUFORGEN Secretariat about this page