Recent Advances in Energy, Environment and Geology The Degradation of the Asphalt Alleys by Rhizomes of Herbaceous Plant Species of Couch Grass FILIPOV Feodor*1, ROBU Teodor**2 1* Soil sciences Department, Faculty of Agriculture 3, Ion Ionescu de la Brad" University of Agricultural Sciences and Veterinary Medicine of Iasi, Mihail Sadoveanu Alley, 700490, Iasi, Romania, +40232407450, [email protected] **2Crop science department, Ion Ionescu de la Brad" University of Agricultural Sciences and Veterinary Medicine of Iasi, Mihail Sadoveanu Alley, 700490, Iasi, Romania, +40232407450, teorobu@uaiasi Abstract: - The soil cover of urban areas consists of several soil taxonomic units with significantly altered properties and functions. Soils covered by asphalt or another compact materials (such as concrete materials), also known under the name of or ekranic Technosols [1, 2], have strongly modified properties and perform only part of the specific functions that allow only low biological activity and root growth of some plants species. Soil under asphalted alleys have water retention capacity and allows expansion of the roots of woody plants and grasses. The soil horizons under asphalt pavers can be developed only a small number of plant species that are tolerant of deficient aeration. It is well known that the concentration of oxygen decrease considerable and the concentration of carbon dioxide increase significantly (>10% or even 20%) in the compacted soil layers or in the soil layers under asphalt [3, 4]. Some physical soil properties of such as bulk density, compaction degree, air porosity, total soil porosity are substantially modified. Frequentlly, the values of physical properties of soils covered with asphalt indicate that soils are a strong compacted. Under these circumstances the soil covered with asphalt can be explored by a smaller number of plant species. Case studies conducted in several locations of urban area from Romania showed that soils under asphalted paths or alleys keeps some undisturbed soil properties such as particle size, mineralogical composition. Some plants roots may continue to grow after pavement is placed over an existing roots system. Some plants species such as Tillia tomentosa, Populus nigra, Populus alba that grow in the vicinity of asphalted paths lead unevenness, cracking and perforation of asphalt path. Even if it seems impossible, the asphalt path can be traversed by plant roots or runners that develop from buds on roots or rhizomes of herbaceous plant species. One of herbaceous plant species able to penetrate asphalt is Cynodon dactylon known under the name of Couch grass, Bermuda grass, Quickgrass, Twitch grass [5, 6,]. Investigations conducted by us in the field have shown that Cynodon dactylon (perennial grasses) is able to cross paths asphalted by runners that develop from buds on the rhizome. The runners of this plant which grow in soil horizon located under asphalt are able to penetrate the asphalt pavers during the hot summer. In some cases, the first runners cross the pavement in the parallel direction to the surface, at a distance of a few centimeters, after that reach the surface. The developed cracks on the asphalt allow growth of other plant species such as Taraxacum officinale (dandelion), Polygonum aviculare (birdweed, pigweed and lowgrass), Hordeum murinum (wall barley or false barley), Lepidium ruderale (narrow-leaf pepperwort, roadside pepperweed or peppergrass), Poa pratensis (Kentucky Bluegrass, Smooth Meadow-grass, or Common Meadow-grass), Cardaria draba (whitetop or hoary cress). Among the main conclusions drawn from the studies mentioned: (i) Some species of herbaceous perennials such as Cynodon dactylon are able to perforate asphalt. Resistance to penetration asphalted alleys shrinks considerably in hot summer days. (ii) High power crossed the thick rhizomes of couch grass is frequently underestimated and not taken measures to prevent degradation of asphalted alleys. (iii) We believe that highlighting the progressive stages of degradation of asphalt paths and knowledge of biological characteristics of herbaceous plant species able to perforate asphalt are important in the establishment and implementation of preventive measures. Key-Words: - couch grass, asphalt penetration, ekranic Technosols, flowchart preventing measures. ISBN: 978-960-474-338-4 136 Recent Advances in Energy, Environment and Geology 1 Introduction typically impermeable urban soil layers into more permeable zones have the potential to increase Asphalt is a constituent of petroleum. All asphalt stormwater infiltration rates [14]. used in the United States is produced by modern oil Our investigation noticed that some plants refineries and is called petroleum asphalt. Petroleum species such as Tillia tomentosa, Populus nigra, asphalt for use in pavements is usually called paving Populus alba, Cerasus avium that grow in the asphalt or asphalt cement to distinguish it from vicinity of asphalted paths lead unevenness, asphalt made for non-paving uses [7]. cracking and perforation of asphalt path (fig 1.1). Asphalt concrete is a composite material commonly used in construction projects such as road surfaces, parking lots, and airports. Asphalt concrete consists of asphalt (used as a binder) mixed with mineral aggregate and then laid down in layers and compacted. The terms "asphalt (or asphaltic) concrete", "bituminous asphalt concrete", and "bituminous mixture" are typically used only in engineering and construction documents and literature. Asphalt concrete pavements are often called just "asphalt" by laypersons who tend to associate the term "concrete" with Portland cement concrete only. The engineering definition of concrete is any composite material composed of mineral aggregate glued together with a binder, whether that binder is Portland cement, asphalt or Fig. 1 Degradation of asphalt path by deformation even epoxy [8]. cracks and perforation under influence of rooting Factors that cause asphalt concrete to deteriorate system of Tillia tomentosa (Foto: F.Filipov, 2007) over time mostly fall into one of three categories: construction quality, environmental factors and traffic loads [7, 8]. Often, damage results from combinations of factors in two or all three categories. Degradation of asphalt pathways in urban areas is noticed by several categories of defects such as deformation cracks, surface texture deficiencies, edge defects, potholes, patches [9]. Environmental factors that cause degradation of asphalted paths are represented by climate, vegetation (various woody and herbaceous plant species), soil properties etc. Numerous studies have revealed that degradation of asphalted paths is amplified by global climate changes were observed the late twentieth century Fig. 2 Degradation of asphalt path by perforation and the beginning of millennium [10, 11,12, 13]. after emergence of Cerasus avium (Foto: F. Filipov, Increase solar radiation, enlargement of temperature 2007) and heat waves, increasing the frequency of increased freeze-thaw cycles (mild winters) Even if it seems impossible, the asphalt path can contribute to degradation of asphalted paths [10]. be traversed by plant roots or runners that develop It well known and recognized that the trees from from buds on roots or rhizomes of herbaceous plant urban spaces greatly improve quality of life for species. One of herbaceous plant species able to human and wildlife by decreasing air temperature in penetrate asphalt is Cynodon dactylon known under the shaded area, by removing carbon dioxide and the name of Couch grass, Bermuda grass, particulates from the air, by interception of rainfall Quickgrass or Twitch grass. direct precipitation into the ground through trunk In this paper is presented progressive stages flow, and take up stormwater through their roots. In of degradation of asphalt paths and biological addition, urban tree roots penetrating through characteristics of herbaceous plant species Cynodon ISBN: 978-960-474-338-4 137 Recent Advances in Energy, Environment and Geology dactylon which is able to perforate asphalt. soil covered by asphalt were estimated based on the Establishment and implementation of preventive properties of soil from around studied area. measures is possible only taking into account the Biological and ecological characterization of the biology of plants species Cynodon dactylon was done with obtained data from scientifically publications available in the 2 Problem Formulation library and from the internet. The obtained data, concerning the couch grass, Investigations were conducted in urban areas of from the literature were supplemented with obtained some cities from Romania and another country information in conducted studies in urban spaces. from European Community (fig. 3). Most of the Following the centralization and processing of studies were conducted in urban area of Iasi, located obtained data were elaborated synthetic diagram in the central eastern part of Romania. with ecological requirements and with biological characteristics of couch grass. Data obtained from the literature and from our own studies allowed the development of methods to prevent and limit soil degradation and asphalt alleys. a In developing methods of fighting were taken into b account the biological characteristics of plant requirements to environmental factors and factors that cause degradation of aspalt pavers during the year. Because we did not obtain information on available literature degradation by perforation asphalt walkways through