0716-B1

Monitoring of Forest Stand Condition and Its Development in the Czech Republic

Petr Fabianek, Vladimir Henzlik and Karel Vancura^[1]

Abstract

In 1986, the United Nations Economic Commission for Europe established the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) to respond the growing concern about forest damage caused since the beginning of the 1980s by air pollution load. The Pan-European grid of the ICP Forests monitoring plots represents one of the most important systems of forest ecosystem assessment and checking.

Unfortunately, this problem is well known in the Czech Republic so the country joined ICP Forests at the very beginning.

This paper presents general information on Czech forest stand condition gathered through various methods in the past, as well as in the framework of ICP Forests.

Participation in the ICP Forests represents a contribution of the EU candidate country to the fulfillment of the EEC Reg. No. 3528/86. Although it seems that the effects and importance of air pollution are decreasing, a lot of new stress situations exist and the programme needs to be continued.

Introduction

Forests in the Central European region have been considerably damaged during the industrial development history. Effects of air pollution and forest decline symptoms were described already in mid of the 19^th century. But only 100 years later really serious damages begun in the neighborhood of pollution sources. Czech Republic has regions of this type in the northwest of Bohemia and northern Moravia. Both of those localities have been industrialized together with the long lasting coal mining. The area of Krusne hory Mts. /Ore Mts./ belongs to the "black triangle". In this specific region the forest decline triggered by air pollution is considered to be one of the most important threats the forest ecosystems have been facing. Energy production via burning of low quality brown coal and chemical industry were the worst emission sources in the area. Enormous concentrations of pollutants, originally mostly SO₂ and NO_x, caused the loss of about 50,000 ha of forests in the mountain ridges. Interactions between air pollution and other stresses, having mostly synergistic effects, occurred also in other regions. A combination with other abiotic (frost, wind) and, usually secondary, biotic factors (insects, fungi) resulted particularly in fragile mountain ecosystems in a ecological catastrophe. Dynamic disintegration of forest, decreases in its production functions, failure of its ecological functions and tree species genetic resources disappearance have immense ecological and social consequences.

During the long-term pressure of pollutants, a nutrient leaching process from forest soils continued, resulting to the soil degradation and site productivity decrease. Thus a stability of forests declined and forestry problems continued in contrary to the fact, that total forested area has continuously increased already since the beginning of 20^th century. In the end of 80´s more than 60 % of total forested area has been damaged at some level. 2% of the Czech forest have been cut down because of the damage. These areas were reforested by the so called provisory forest stands composed of tree species (birch, mountain ash, introduced spruces and pines) which are able to fulfill the other forest functions (mainly soil and water protection), not the production one. Air pollution became an important political topic and some of the forestry research results could not be published in that time. Nevertheless, research results from this "lab" were interesting and broadly accepted by research community and several international meetings took place in Czechia. Particularly IUFRO conferences in 1974 and 1984 should be mentioned. The IUFRO cooperation was important and many field trials have been set up in the border area of former Czechoslovakia, East Germany and Poland.

In this milieu it is quite understandable that Czechia has been involved in the monitoring of forest stands condition.

As mentioned above, mostly mountain forests have been exposed to air pollution. There are areas where the shortening of spruce stands survival shows a relatively similar trend under the influence of air pollutants, climatic, site conditions and genetic characteristics of forest stands.

Forest threat zones have been delimited on whole area of the CR. These are a classification of the forest stands damage dynamics, fastness of forest stands decline. There are 4 zones as follows. In the zone A, the life expectancy of a mature Norway spruce stand is maximally 20 years since the beginning of a significant air pollution affect (life expectancy of younger stands in the same zone is longer - about twice for stands of 35 years). A survival in the zone B is 40 years, 60 years in the zone C, etc.

Zone A ranges to 1,1% of the Czech forest, zone B 5,0%, zone C 19,8%, and zone D 74,1%. Normally, without pollution pressure, Norway spruce has an average rotation period of about 110 years.

Damaged mountain forests were frequently situated in rock fields exposed to intro-skeletal erosion (removal of organic and inorganic soil into deeper layers of the mantle rock). Accompanying phenomena are drying and withering of original ground vegetation, its decomposition, and faster mineralization of forest litter and subsequently surface stoniness.

Construction and forest road network use, regeneration method, logging and skidding technology, and soil preparation technology for reforestation influenced the production capacity of sites and water quality in streams through erosion in the conditions of air-pollution disaster. Fear of floods increased because mountain regions are crucial areas for their origin. Also great changes in the groundwater level and water regime of soils occurred.

Impacts of global climate changes on the stability of mountain forests ecosystems represent still an open question. The inputs of particular factors and harmful agents into the ecosystems and their synergistic relations and dynamics of their development are not precisely known up to data.

Nevertheless, it is supposed that mixed autochthonous stands composed of local tree species ecotypes (beech, silver fir, spruce, sycamore, mountain ash, birch, etc.) should adapt themselves much better than allochthonous spruce monocultures. A long-term priority is to increase the proportion of broadleaved, particularly of European beech and sycamore.

Monitoring of forest condition

Investigation of forest status was provided, except of forestry research, in long term perspective by Forestry Management Institute on so called "permanent sample plots". This activity on assessment of forests health development began in fifties, when the first sample plots was created mostly for monitoring of SO₂ effect on forest stands. Some of these plots were later used for the creation of the supranational grid of ICP Forests. In consecutive years another stresses and damages agents has been shown, unfortunately mostly in the interactive synergy. The identification of the extent and priority causes of these stress factors was not easy and thus, it was, and is, not possible to divide the immission effect from other stresses affecting forests. There it was necessary to monitor the entire changes in forest ecosystems. Kveton Cermak, director of Forestry Research Institute introduced this idea of very first endeavour for the ecosystem approach in the beginning of 50ties.

A monitoring of the forest stands damage level covered the whole country in the beginning of 80ties. Except of investigation of forest stand state, also soil conditions, forest stands nourishment, growth characteristics and air quality have been assessed.

Czech Republic joined the Programme since very beginning - in 1986 there were together 61 monitoring plots in the grid 16 x 16 km.

In 1991, a denser grid of 8 x 8 km with another 334 plots was created and except of it so called regional studies in the grid of 1x1 km in the natural forest regions Sumava, Brdy a Krkonose. Later the similar study was realized in the Beskydy Mts. Results from these plots brought mainly detailed and representative information on forest condition in particular regions and compare health condition of forest stands with their nourishment.

Currently the assessment of 291 sample plots with 14,432 trees is provided in the regular 16 x 16 km transnational grid according methods corresponding to those of the ICP Forests Manual and the relevant EU / EC Regulations. It represents 24 forest tree species in elevations from 150 to 1300 meters above sea level. In a long-term trend the main indicator - defoliation - has an increasing tendency, in particular by older coniferous trees. Nevertheless, a dynamics of this development was considerably decreased in 90ties. Also latest development of the decrease of the total emission is mentioned, particularly of sulfur oxides, description of influence of other pollutants and effect of weather conditions.

Regular national investigation in Level I, is provided also on selected 8 x 8 km network. Both the networks comprise 300 plots regularly distributed according to the forest percentage over the whole territory of the Czech Republic. Plots are situated into the forest stands so that they could well characterise the defined site and stand conditions.

So called Coordinating Centre East existed in the beginning of 90ties in the Forestry and Game Management Research Institute at Jiloviste-Strnady aimed to the extension of the ICP-Forests to the Eastern European countries in transition (CEEC/CIT). There were organised coordination meetings, inter-calibration training courses and short study visits of foreign participants in the FGMRI with the financial support of the UN ECE. Also Task Force meetings of ICP Forests were organised twice in the Czech Republic.

At the same time closer collaboration with CEECs has been also supported when EC "claimed" the programme through the financial support and creation of respective legislation.

The Czech Republic signed the Strasbourg Resolution No. 1 and obligations of the Programme fulfilled the decision confirming that ICP Forests will represent follow-up of this resolution.

From the viewpoint of the long-term development the defoliation, as a main sign used, has an increasing trend. This is typical mostly in the case of old coniferous trees even though the dynamics of this trend has been significantly declined in beginning of the 90ties. Defoliation development of broadleaved has been slightly different. There was decline in 1998 but in following years the consecutive worsening has been recorded.

Decrease of total emission has occurred in the last years (particularly of SO₂ and solid particles), the emission of other pollutants has remained approximately at the same level since 1995. Of course, reviewing of development is possible after some time, as forest stands usually reacted on site change and changes of emission situation with certain delay.

Since 1995 also the monitoring on so called "Level II plots" has been performed. Investigation of some of those plots is carried out in the frame of the projects solved by the Ministry of Environment. This intensive evaluation of health state is currently carried out on 14 plots, eight of them are in Norway spruce stands, two are in mixed stands and four are representing broadleaved. All together 918 trees of 14 species were assessed according the common methodology. Crown condition - defoliation, increment, number of needle year classes, phytocenological observations, foliage, soil and tree ring analyses, deposition, both bulk and throughfall, were observed and measured and also meteorological parameters are continuously assessed at several plots.

Quality, quantity and time dynamics of air-pollution stress have been monitored to describe the type and extent of damage to forest ecosystems that have crucial consequences for the choice of tree species composition in regeneration targets and setting up the fundamental principles of tending and regeneration. Again, fragile mountain forest ecosystems have been a subject of special interest.

Average annual SO₂ concentrations at selected mountain forests stations (1973-2001).

Maximum 30-minute SO₂ peak concentration in the air amounted to about 2 500 ìg.m^-3 in the Ore Mts in 1997. The air pollution load is relatively lowest in Sumava, Novohradske and Jeseniky Mts. and the trend shows a decrease of pollution load.

The winter season of 1995 to 1996 brought enormous problems to the Ore Mts. Acute injury occurred caused by long-term extreme inversions, high concentrations of SO₂ and unfavourable climatic conditions. A combination of high concentrations of phytotoxic substances and persistent rime presence was on behind and resulted to the loss of about 3,000 ha of mostly young stands.

Recently, damage to forest stands caused by ozone has increased in mountain regions (particularly in Sumava, Slavkovsky Forest, Ore, Jizerske hory and Krkonose Mts.).

In the last decade when SO₂ and NO_x concentrations significantly decreased, acid atmospheric deposition started to be a serious health hazard for mountain forests in the Czech Republic. It is monitored i. a. in mountain forest watersheds under BIOGEOMON project.

Also remote sensing using the Landsat satellite images is considered as very important. The Forestry and Game Management Research Institute collaborates with the company Stoklasa Tech., involved in this defoliation and mortality assessment method already since 1994. Forest damage maps for the CR are elaborated annually. Information evaluated from satellite images can be verified on the basis of terrestrial investigation - and ICP Forests having plots throughout the whole country represents a good source for such verification.

Average damage and mortality degree is observed and their trend is assessed with the aim to forecast the future development. A terrestrial defoliation assessment is burdened by certain error due to the observer's subjectivity during the whole observation period. The statistical counterbalancing of such assessment based on two alternative models (ICP1 and ICP2) represents an attempt to eliminate this subjective influence. Such adjustment is practiced on all monitoring plots (in the picture below presented in a chosen plot No. G240 representing spruce stand of highlands). The visual observation (ICP) and its balancing models are compared with results of remote sensing observation of defoliation using the Landsat TM (LTM) images.

It seems that currently the situation is stabilised and without some synergistic damaging agents (e. g. extreme weather conditions) a worsening of forest condition is not expected.

Correlation of forest health condition of forest stands and temperature rainfall factor is performed because of the last year's extremes of weather conditions.

Relation to criteria and indicators of sustainable forest management

Monitoring of forest condition is also important as internationally accepted tool for investigation and assessment of criteria and indicators of sustainable forest management. The Czech Republic has adopted the complete set of Helsinki Criteria and Indicators and also because of problems mentioned, another complementary national indicators have been added (share of salvage fellings, share of broadleaved in reforestation and in total forest area). Regularly are monitored for example:

Total amount and change in depositions of air pollutants (assessed in permanent plots)

Changes in nutrient balance and acidity (pH and CEC); level of saturation of CEC on plots of the European network or of an equivalent national network.

Assessment of ICP Forests Plots

O - organic horizon
M01 - mineral horizon enriched by humus ca 0-10 cm
M12 - mineral horizon ca 10-20 cm
CEC - cation exchangeable capacity
Max. frequency = variable or span of variables with maximal frequency

Conclusions

Since the beginning of the 90´s, changes occurred in the composition of pollution and their total amount was downsized also due to the lower industrial production in the beginning of transition stage.

The ICP-Forests Programme represents only one activity that covers the whole territory of the country and offers information in the harmony with the precise European methodology. It has, of course, great importance from the point of view of the long-term character of investigated problem and its Pan-European extent. ICP methodology became a unifying element of the whole scale of monitoring systems and its manual is broadly used in national level. If we understand that the cross-sectoral approach to forestry issues is needed, this programme and its system provide a multifunctional monitoring approach.

Unfortunately, the knowledge of different ecosystems responses to progressive civilization pressures is still poor. Changes in ecological conditions will likely bring changes in ecosystems structure, in their function and production. Conditions of particular forest vegetation zones will certainly change to some extent, but no greater shift is expected, as forest ecosystems are relatively conservative objects. Particularly changes in the soil are very slow, especially in comparison with climate changes.

Trend of defoliation of all species in the last decade gives the general overview on situation in the Czech Republic (ICP defoliation classes 2 - 4).

Forest inventory programme (2001-2004) supposes various measurements re. biodiversity. The same methodology should be used in ICP-Forests plots. Ground vegetation diversity assessment should continue e. g. in nuclear power plants surroundings (interrupted in 1990). ICP plots with broadly distributed species should serve also to investigate possible global change. Because of climatic extremes there is a need to compare the health status of forest stands with meteorological figures, e. g. Lang´s rain factor. Meteodata are considered as important.

A project of forest ecosystems complex monitoring is currently performed. Aim of the project is to sort out existing activities carried out at the sector level in monitoring of forest health and its causes, to unify methods, and to reach unique interpretation of results at both, national and regional levels. The another target is to include possible new projects into the system, to avoid duplicity, and to offer synoptical data and well-arranged materials for the next evaluation of data available. The optimization of current network is very important, as the lack of communication among various subjects dealing with monitoring activities, e. g. on the regional level still exists. Also the harmonization of sampling, analyses of foliage and soil samples, registration and record keeping unification of samples, as well as accessibility of results and unification of laboratory methods are pursued.

Under the current trends of sustainable forest management, based on good knowledge of forest condition, forest typology and forest ecosystem ecology, and continuous improvement of environment it seems, that the prosperous future of our forests, heavily afflicted by an air pollution environmental disaster in the past, will be globally ensured.