Germany; Long-Term Vegetation Research on Two Extensive Green Roofs in Berlin - University of Applied Sciences Neubrandenburg

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Germany; Long-Term Vegetation Research on Two Extensive Green Roofs in Berlin - University of Applied Sciences Neubrandenburg
  URBAN HABITATS, VOLUME 4, NUMBER 1 ISSN 1541-7115 Long-Term Vegetation Research on Two Extensive Green Roofs in Berlin  Long-Term Vegetation Research on TwoExtensive Green Roofs in Berlin by Manfred Köhler University of Applied Sciences Neubrandenburg, Brodaer Str. 2, 17041Neubrandenburg, Germany Abstract In this paper, I evaluated the long-termvegetation dynamics of two extensive green roof (EGR) installations in Berlin. The first, installedon two inner-city residential buildings in 1985,consisted of 10 sections ( sub-roofs ) with acombined area of 650 square meters. The 10 sub-roofs differed in exposure and slope. Ten plantspecies were initially sown on the sub-roofs.Observations were made twice yearly (with afew exceptions) from 1985 to 2005. Altogether,110 species were observed over the 20-year time period; however, only about 10 to 15 of thesewere dominant over the long term and could beconsidered typical EGR flora in Berlin.  Alliumschoenoprasum was the dominant plant speciesover the entire time period on all sub-roofs. Festuca ovina , Poa compressa , and  Bromustectorum were also typically present over thecourse of the study. Statistical tests revealed thatweather-related factors such as temperature andrainfall distribution were the most importantfactors affecting floral diversity. The size, slope,and age of the sub-roofs had no significantstatistical influence on plant species richness.This EGR installation was virtually free of technical problems after 20 years. The success of this low-maintenance green roof is a goodargument for greater extension of green roof technology in urban areas. The EGR of thesecond study was installed in 1986, butinvestigation of the flora only began in 1992.Observations were again made twice yearly until2005. The six roofs studied were on top of acultural center located in a park area in the Berlinsuburbs, and they were irrigated during the firstfew years to support plant establishment. TheseEGRs had a higher degree of species richnessthan the inner-city ones. These early German projects in urban ecology demonstrate thatrelatively diverse EGRs are possible on city buildings. They also show that species richnesscan be increased with a minimal amount of irrigation and maintenance. And they suggestthat enhanced initial plantings, the creation of microclimates (shaded and sunny areas), and the presence of surrounding vegetation also increase plant diversity. Key words: extensive green roofs; Germany; plant community dynamics; urban ecology;vegetation science- 3 -  URBAN HABITATS, VOLUME 4, NUMBER 1 ISSN 1541-7115 Long-Term Vegetation Research on Two Extensive Green Roofs in Berlin  Introduction There are two types of green roof. The first, the intensive green roof, or roof garden, generallyfeatures trees and other large plants and requiresdeep soils, intensive labor, and high maintenance,and its purpose is usually ornamental. Roof gardens can be designed in nearly every gardenstyle; many examples from around the world are presented in Theodore Osmundson's book   Roof Gardens (1999). The second type of green roof is the extensive green roof (EGR), as defined by the FLL (2002). It is characterized bydrought-tolerant vegetation grown on a thin layer of growing medium, and it requires littlemaintenance and usually no irrigation. MostEGRs are constructed on flat roofs with slopes of about two degrees for drainage. Pitched EGRsare in the minority. In the long-term experimentreported here, roofs with pitches of up to 47degrees were tested along with flat roofs (seeTable 1).In Germany, the first boom in green roof construction came at the end of the 19th century,when numerous apartments were built as low-cost rental housing for the families of industrialworkers. A layer of gravel and sand with somesod was added to the roofs for protection againstfire (Rueber, 1860). This type of green roof wasinstalled all over Germany on less than 1% of  buildings.The vegetation dynamics of some of theseearly EGRs were described by Kreh (1945),Bornkamm (1961), and Darius and Drepper (1984). These studies showed that a vegetationtype called Poetum compressae (mainlyfeaturing the grass Poa compressa plus a lot of moss and annual plant species) dominates theroofs. Grasses are dominant on growing media10 to 20 centimeters in depth; on media less than10 centimeters in depth, the genus Sedum andmosses are most successful.After 1980, many green roofs wereconstructed with the idea of bringing vegetation back into urban areas. Divided Berlin was afocus for EGR installation in Germany. Thehistory of green roof development in Berlin isdocumented in Koehler and Keeley (2005).Beginning in the 1980s, there was a changein urban planning in Germany. Neighborhoodswith apartment buildings from the era of earlyindustrialization were renovated. Citizens preferred to live in more mature neighborhoodsin the center of town rather than in newlyconstructed multistory buildings in the suburbs.More apartments were integrated into existingurban properties. Additional apartments werealso added to rooftops of existing buildings, sothat typical four-story apartment buildings in theinner city got a fifth level with roof windows andterraces. At first these new apartments wereuncomfortable due to insufficient insulation.However, as the decade progressed and theinfluence of urban ecologists increased, planners began to reconsider using green roof technology.A new building code was developed thatrequired extensive green roofs to be constructedover roof apartments in central parts of the city.In addition, incentive programs were introducedto reduce the additional costs of installation. The program, which lasted from 1983 until 1996,- 4 -  URBAN HABITATS, VOLUME 4, NUMBER 1 ISSN 1541-7115 Long-Term Vegetation Research on Two Extensive Green Roofs in Berlin  supported the installation of about 63,500 squaremeters of green roofs (Köhler & Schmidt, 1997).It was terminated after German reunification.Currently, green roofs are legally required by thefederal government for buildings on largeconstruction projects, such as the recent ones inPotsdamer Platz (for a case study, see EarthPledge, 2005). The Research Sites 1. Paul-Lincke-Ufer (PLU) Green Roofs The Paul-Lincke-Ufer (PLU) project in theneighborhood of Kreuzberg was the first inner-city residential eco-project in Berlin, and one of the first in Germany. The project was conceivedduring studies carried out in the early 1980s toexamine the potential of inner-city greening.Funding to execute the project was provided in1984 by the federal government and the Berlinsenate. A number of conservation ideas wereincorporated into PLU buildings, including wasterecycling and decentralized heating. The projectwas the first of its kind in the city to include amonitoring program evaluating the success of itsdifferent components. I was responsible for vegetation research and for measuring the urbanclimate. The official survey lasted 12 years, anda final report was published almost a decade ago(Köhler & Schmidt, 1997). Since then, I havecontinued the research without governmentfunding.For this paper, I observed the long-termvegetation dynamics of 10 EGRs (referred tohere as sub-roofs 1–10 ) on two buildings at thePLU site (see Figures 1a, 1b). Installed inautumn 1985, the green roofs are 24 metersabove the ground and have a range of differentexposures and slopes (Table 1). Their combinedarea is 650 square meters. Initially, erosion barriers were installed in the growing medium of the pitched roofs. The 10-centimeter-deepgrowing medium (consisting of a mixture of expanded clay, sand, and humus) had an averagewater-storage capacity (and water availability to plants) of 16.5 liters per square meter (author'smeasurement)—a relatively low capacitycompared with other green roofs in Berlin(Köhler & Schmidt, 1997). To speed plantcoverage on the roofs, precultivated vegetationmats were used. These mats included some popular EGR plant species (see Table 2, under column titled seed ). Plants were selected onthe grounds that they would not requireadditional maintenance or irrigation after installation. The mats were prototypes and werein and of themselves an experiment in green roof  production, transport, and installation. In thefollowing years, this technology came intowidespread use for extensive roof greening. Methods (PLU Site) The study ran from 1986 to 2005. Data wascollected twice a year, in May and in September,with a few exceptions. There are no data for 1988 and 1990 and only one observation per year for 1987 and 1989. Measurements included thenumber of vascular plants, percent coverage of each plant species, plant heights, and the percentage of standing dead (living plants withdead leaves and stems). Data analysis was- 5 -  URBAN HABITATS, VOLUME 4, NUMBER 1 ISSN 1541-7115 Long-Term Vegetation Research on Two Extensive Green Roofs in Berlin  conducted for the following categories: quantityof seeded species, life form of the plant species,and type of plant (i.e., annual or perennial). For more on the method of data collection used, seeKreeb (1983). Table 2 is an example of thereduced srcinal data set for sub-roof 1.Multivariate analysis of variance (MANOVA)was performed on the data using the SPSSstatistical package (SPSS Version 11; see Diehl& Staufenbiel, 2002). 2. Ufa-Fabrik (Ufa) Green Roofs The second green roof site was the Ufa-Fabrik (Ufa) cultural center, located in a park area insuburban Berlin, in the Templehof neighborhood.The center is famous for its association with thegolden age of German cinema in the 1920s and1930s. Copies of Ufa films were stored here.These films were highly flammable, so thestorehouse was built with a special vegetatedcovering to protect it against fire. After WorldWar II, Berlin lost its status within the filmindustry, and the Ufa complex was abandoned.However, in the 1980s, a group of grassroots andcultural environmentalists occupied the area andstarted renovation work. The environmentalistswere inspired by the storehouse (or Filmbunker,as it became known) to cover all the other  buildings in the complex with extensive greencover.The Ufa EGRs were built virtually at thesame time as those of the PLU project, the maindifference being that the Ufa activists conductedtheir work without the support of academicresearchers. Between 1986 and 1990, duringseveral green roof workshops, three EGRs wereinstalled, with a total area of about 2,000 squaremeters. Various other green roofs were added inthe following years. Today, every Ufa buildingfeatures an EGR (see Figures 2a, 2b, and someof the roofs are augmented with photovoltaic(PV) panels. Indeed, one of the largest PV power  plants in Berlin was erected on a green roof atthe Ufa complex (Köhler, Schmidt, Laar,Wachsmann & Krauter, 2002).The EGRs were planted with floweringmeadow species seed-collected from the Alps.The 10-centimeter substrate consisted of sandygarden soil with about 10% expanded clay.During the first years, the green-roof meadowswere irrigated by volunteers, and plant speciesrichness was high. Since the mid-1990s, however,the water system for the Ufa buildings haschanged, and irrigation of the EGRs on the Ufaroofs has stopped. Methods (Ufa Site) Beginning in 1992, the EGRs of the Ufacomplex were studied in the same manner as thePLU roofs. At the Ufa complex, six roofs arecurrently in the research program. Table 5 details plant community succession on the roof of theUfa concert hall. Results 1. PLU Site The vegetation of one EGR in the green roof complex (sub-roof 1) was examined and may beconsidered representative of the vegetationdynamics of the other EGRs studied. Further - 6 -
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