Age and Inventory Structure of the Forests 1990

Introduction

The Berlin forests and woodlands are exposed to heavy use pressure because of their multiple functions. The primary function of the forest is recreational, but it also serves as protection and equalization for the water, soil and climate, and as a habitat for animals and plants. In Berlin, the forest now plays only a subordinate role in terms of its economic significance. Almost 20 % of the Berlin urban area is covered with forest. Thus, Berlin has a very high share of forest in comparison with Hamburg or Munich, which have 5.7 and 5.1 %, respectively.

A natural forest is a complex system. Depending on the prevailing soil and climatic conditions, a herbaceous layer, a richly structured shrub and tree layer, and the corresponding fauna will have formed. A wooded area, by contrast, is defined by its principal economically useful main tree layer. The type of tillering in a wooded area is oriented primarily toward profitability, with the soil only an optimization factor. For easier care and harvest, age-class forests prevail, in which only one age and/or height level is to be found on a given area. Moreover, monocultural plantation is frequent. These woodlands are considered non-natural.

In Berlin, there are today no longer any natural forests. The areas are characterized by more than a century of forestry management and by the functions which near-urban forests fulfill today. However, some near-natural forest associations do exist. The natural forest associations occurring under the present local conditions can be seen on Map 05.02 – “Vegetation.” The present Map, “Age and Inventory Structure,” on the other hand, shows the actual situation of the main tree layer.

With passage of the State Forest Law (LWaldG) in 1979, the entire wooded area of then-West Berlin was proclaimed as protected and recreational forest land, in which recreation receives precedence over wood production. This natural forestry operation provided for sustainable management. In East Berlin, economic use of the forest had priority up until the political transformation. Since consolidation of the two forestry administrations in 1990, the State Forestry Law has applied to the entire city. The goal of near-natural and site-appropriate forestry was concretized in the new Forestry Guidelines of 1992. Today, the goal is to gradually develop the Berlin forest into a florally appropriate and near-natural forest.

The state of health of the Berlin forests must be classified as poor, even though a slight improvement in its condition could be recorded in recent years. According to the 1995 Survey of Forest Conditions (Waldzustandserhebung), 18 % of the forests are significantly damaged in Berlin, and 14 % in Brandenburg (cf. SenStadtUm 1995b and Brandenburg State Ministry for Food, Agriculture and Forestry, 1995). These proportions of the Berlin and Brandenburg forests and woodlands fall into Damage Levels 2 to 4, which means that over a 25 % loss of needles or leaves appears on the trees (cf. Tab. 1). In 1993, with 51 % clear damage, a high damage level was found for oaks. The cause was the dry weather in 1992. Due to the relatively precipitation-rich springs of 1993 to 1995, the oaks were able to recover. The proportion at Damage Levels 2 to 4 was 22 % in 1995, and thus approximately at the damage level of 1992. The health of pines, too, has improved (cf. Tab. 1). In 1995, the best condition of the crowns since 1983 was attained.

Tab. 1: Forest Damage, 1991 to 1995 in Berlin (in %)

Evolution of the Berlin Forests

Before the colonization in the 12^th century, the area of today’s Berlin was largely c
overed with forest. Oak and hornbeam forests were the prevailing forest types on the clayey soils of the plateaus (the Teltow, Barnim and Nauen plateaus), and pine and oak forests on the valley and plateau sands of the glacial valley and the Grunewald forest. In locations remote from groundwater, the pine-oak forest occurred in the form of durmast oak-pine forests, in locations near groundwater, in the form of English oak-beech forests or English oak-birch forests with a proportion of pines. This proportion was generally below 50 % in the original pine-oak forests, however, so that deciduous trees prevailed. In the river valleys and the flood areas, elm riparian forests and oak-hornbeam forests grew. The woodland was interrupted only by some bogs in the Grunewald and Spandau forests. Before the colonization, the oak-hornbeam and the pine-oak forests each accounted for approx. 45 % of the wooded area, of which only 9 % consisted of pure pine stands. The forests of moist to wet locations thus accounted for only 10 % of the wooded area.

The earliest extensive use of the forest was forest pasturing. The cattle were driven into the forest and fed on foliage, bark and fruit as well as seedlings of the young trees. This caused a thinning of the forest, i.e. fewer young trees grew to maturity. The consequence was a changed species composition and the formation of stands of the same age. The colonization and cultivation of the countryside and, with it, the clearing of the forest began on the most fertile soils, which were transformed into farmland. Thus, the oak-hornbeam forests were displaced on the clayey soils first. The heavy settlement development beginning in the 19^th century also led to the build-up of fertile areas of arable land. Additional wooded areas were cleared, so that the forest survived only on the poorest soils, the pine and oak sites, strengthening the dominance of pines and oaks.

Not only direct soil utilization caused a constant retreat of the forest. With the rising population, the need also arose for wood as a raw material and energy source. Mismanagement soon resulted in a wood supply shortage, so that as early as around 1700, the first legal regulations was imposed. The oak receded in the Berlin forests more and more in favor of the pine, since the latter grew better on the soil considerably damaged through forest pasturing, and since the oak was no longer favored for feed. Since the beginning of the 19th century, the primary cause for the growing loss of wooded areas has been real estate speculation. Thus, the Berlin Council determined in 1823, despite furious citizens’ protests, to clear-cut the Cöllnish Heath. By 1875, the city of Berlin had no more public forest property in its possession. In 1890, the Grunewald Forest consisted almost completely of pine monoculture. At the turn of the century, the State Forestry Administration began to sell large wooded areas of the Grunewald Forest to real-estate speculators (by 1909, some 1,800 ha had been sold) (cf. SenStadtUm 1991).

As part of the property acquisition for the extensive establishment of sewage farms, the city acquired the districts of Buch (1898) and Gorin (1909). In order to guarantee the drinking-water supply for the growing population, the Wuhlheide Heath was added in 1910-’11. In 1911, Berlin and the surrounding communities combined to form the Administrative Association of Greater Berlin. One essential purpose was the acquisition and conservation of large areas which were to be kept free of development. In 1915, the “Permanent Forest Purchase Agreement” was concluded between the Royal Prussian State and the Administrative Association of Greater Berlin. The Administrative Association acquired large parts of the forest districts of Grunewald, Tegel, Köpenick, Grünau and Potsdam (approx. 10,000 ha) from the State of Prussia, and obligated itself not to build upon or to resell the acquired wooded areas, but to preserve them permanently for the citizens as near-urban recreational areas. In order to provide the inhabitants of the populous industrial borough of Wedding with recreational possibilities to the north, the city bought the Lanke forest area as well. With the establishment of Greater Berlin in 1920, the municipal forests of Spandau and Köpenick as well as the woodlands of Wansdorf, Carolinenhöhe and Tasdorf belonging to sewage farm properties, became the property of the city. Only after the inflation could Berlin acquire further small forest areas in 1928 (e.g. the Düppel Manor and Neu-Kladow). The last large purchase occurred in 1937, with the acquisition of the Stolpe Forest, bordering Tegel. The forest land of the City of Berlin covered 25,480 ha before the beginning of the Second World War. This lay both within and outside the city limits (cf. Fig. 1).

Fig. 1: Survey of the City Forests in the Area Surrounding Berlin in 1945

In the course of the Second World War, the Berlin forests were greatly damaged. Between 1937 and 1944, twice as much wood was cut “to strengthen raw material supply” in Berlin, as would have been sensible from the point of view of forestry planning – 150,000 solid cubic meters per year (fm/a) instead of 71,000 fm/a. At the same time, the planting of new trees was neglected, and thus the principle of sustainability abandoned (cf. SenStadtUm 1995a). This systematic depletion increased still more during the last two years of the war: For the defense against the advancing Allies, a large number of trees was indiscriminately felled by the Wehrmacht, leaving behind extensive desolation. But also large-scale theft of firewood, both by the Wehrmacht and by the population, did great damage to the forest (570,000 fm during 1945-‘46).

With the end of the Second World War, a period of different development of the forests began in the eastern and western parts of the city, as well as in the districts located outside the city.

In West Berlin, after the war’s end and the ensuing blockade (1948-‘49), approx. 45 % of the original wooded areas had been cleared and/or greatly thinned. For lack of other plant material, mainly pines were used for the extensive reafforestation of the barren areas. This is reason today for the relatively high proportion of approx. 45-year-old pine monocultures.

Since the beginning of the 50s, the West Berlin forestry institutions have been promoting the transformation of the forest by deciduous underwood seeding and planting in clearings in stands of clear, old trees, as a step in direction of a mixed forest. The goal has been forestry on the basis of a selection forest, and the development of a permanent forest. At the same time, however, such florally foreign tree species as larch, Douglas fir, Weymouth pine and red oak were also introduced by hurst and cluster into the stock. The 1979 State Forest Law and the 1982 Basic Forestry Plan for the Berlin Forests were oriented toward a naturally compatible operation of the Berlin forests. The most important goals of these operational guidelines were:

• an increase in the deciduous share from 40 % to 60 %;
• the development of a richly-structured mixed forest;
• the improvement of the conservation and landscape care;
• a 1-ha limit on clear-cutting;
• the adoption of natural regeneration; and
• to dispense with the use of herbicides and improvement measures.

The forest lands in East Berlin developed differently. The destruction of the old growth had not been as extensive as in the western part of the city. Those trees which, by the end of the war, had surpassed pole-timber age, but not yet reached felling maturity, were not subjected to harvesting during the ‘50s to the same extent as in West Berlin. This affects many areas in the districts south of the Müggelsee Lake. Thus, the old-growth proportion (stocks over 80 years old) was able to grow to 53 % by 1975. In addition, the rotation age has been raised for pines from 100 to 120 since 1975. The result was a deficit in wood production, which was tolerated out of consideration for the recreational function of the Berlin forests. Due to the staged clear-cutting of the pines, wooded areas were characterized predominantly by the structures typical of an age-class forest. Thus, the Berlin forests assumed a special place in East Germany. They received a recreational function, in addition to the primary role of raw material production.

Forestry in East Germany was greatly centralized. This was further intensified during the ’70s. The goals were maximum increase in domestic wood production and the transition to industrial production methods. In the Berlin forests, the following measures were to be carried out:

• removal of all low-production stocks;
• no toleration of afforestation delays;
• fertilization and melioration measures; and
• restoration of a normal age structure (i.e., removal of the high old-growth proportion).

Because of the goal of multiple use of the Berlin forests, these guidelines could be somewhat diluted. The forest was broken down into classes of recreational functions. Maximum allowable clear-cut areas were established. For instance clear-cutting was forbidden at recreational centers. In recreational park forests, clear-cutting up to 3 ha was allowed; in normal economic-use forests, clear-cutting was allowed up to 10 ha. In the areas of the former city forests outside the city limits, economic management was, however, carried out according to the guidelines of optimal economic use.

As early as the ’60s, smoke-damage investigations were carried out in the East Berlin forests, and damage to the trees was ascertained. As a result, a smoke-damage area amounting to 36 % of the total area was certified in 1974 (by 1975, it was already 43 %). For “revitalization,” damaged pine forests were fertilized with nitrates. Between 1977 and the cessation of fertilization in 1985, 100 to 800 kg of nitrogen/ha were spread in the Fahlenberg and Müggelheim Districts.

A major problem in the East Berlin forest is the wide dissemination of chee-reed grass (Calamagrostis epigeios), which complicates natural regeneration. Its center of dissemination is found particularly in the relatively clear, single-layer pine stands which are free of a shrub layer and of medium age. The spread was furthered through the former practice the clear-cutting and complete replowing, and the fertilization of the forests.

In the Northeast of the city, large former sewage-farm areas were transferred to the Berlin Forestry Operation in 1985 and afforested on the occasion of the 750-year anniversary festival of the founding of Berlin. This was carried out under heavy deadline pressure and without sufficient preliminary examinations, with the goal of the creation a recreational forest. After grading, the sewage farms were planted predominantly mechanically with over 50 different tree and shrub species, such as poplar, mountain ash, birch, alder, European beech, pine and spruce. The site problems, including heavy-metal pollution, the disturbed soil surface and ground-water conditions, and a mistaken selection of tree species (including decorative trees and shrubs) resulted in unsatisfactory growth results and poor stock vitality (cf. SenStadtUm 1995a).

The abundant dissemination the durmast oak, which was introduced about 100 years ago from North America, presents a considerable Berlin-wide problem, since it suppresses natural regeneration of florally-appropriate tree species, and the development of a herbaceous layer. In the former West Berlin, it has been increasingly cleared since 1985. Its removal from the stock is one of the essential tasks in the Berlin forest.

In 1992, the Berlin Forests published the Forestry Guidelines for Greater Berlin, which brings together the interests of forestry, conservation, recreational use and landscape esthetics to form a uniform concept for action. The orientation is toward careful, sustainable and naturally appropriate forestry. To preserve the climatic, hydrological, hydrochemical and public-health effects of forest areas, extensive measures for the protection and development of near-natural forest structures with rich animal and plant life are carried out in the entire wooded area.

Wood production, otherwise a main task of forestry, will over the long term take a back seat to regional-cultural and social functions. The forests emerging in the future should contain a web of all stages of development, from the regeneration through the aged phase. Important structural elements, like standing deadwood or glades, should exist in sufficient quantity and quality and be distributed throughout the entire wooded area, and/or should emerge anew. The essential criteria for a natural management of the Berlin forest are:

• Gradual reduction of the florally foreign tree species;
• Planting of site-appropriate and florally appropriate tree species;
• Stock renewal through advancement of natural regeneration;
• Promotion of mixed stands with rich structural and species diversity;
• Renunciation on firm rotation times; felling is to be carried out after trees reach their target size;
• Selective, tree-by-tree wood harvesting;
• Abandonment of clear-cutting;
• Protection of hollows and nest-trees;
• An increase in the proportion of deadwood;
• No complete replowing of areas; and
• Renunciation of fertilizer and pesticides (cf. SenStadtUm 1992).

The Berlin Forests in 1990 applied to the Trust Agency for the restoration of approx. 10,750 ha of former Berlin city forest land in Brandenburg. Up to now 9,179 ha of these areas have been restored to the Berlin Forests (as of October 1995). Map 4 shows the new districts Gorin, Stolpe and Wansdorf as well as the Parforce Heath, which is attached to the Dreilinden District.