Report on the natural environment around the Anastasian Wall

Franziska Zemmer

Location

Two spots in the surroundings of Gumuspinar Koyu (Catalca) were visited. The first is in direction towards Altinpinar 3,5 km ESE Gumuspinar Koyu (Catalca) to the NE of the crossroad on the highway 20 and the second is ca. 0,2 km to the SW of the same crossroads ca. 4 km before Gumuspinar Koyu coming from Catalca on the highway 020.

Altitude: ca. 150 m

Geological aspects

Our site lies in the Thrace basin formed during the Tertiary. The oldest geological formations are Paleozoic crystallines (granite, gneiss, micaschist, slate). Upon this basement follow sequences of conglomerates, sandstone, limestone, another layer of sandstone, clay and gravel each of respectively younger age (Gultekin, 1997). Depending on which stratigrafic unit (rock type) forms the partent material, the soil on top might be deeper or more shallow, acidic or basidic. As a result, plant communities growing on it are each adapted to one or the other condition. The forest soil of our study area is dark brown rich in humus, whereas on non afforested areas with human intervention in the surface, such as forest roads, the soil is reddish and rich in clay.

Climatic aspects

The area surveyed is located on the Catalca peninsula in the southern outskirts of the Istranca Mountains. Abundant rainfalls and mild winters account for “humid mesothermal climate with moderate water deficit in summer”. These are Yaltirik`s (1978) words to describe the Belgrad Forest`s climate, which seem to the point for the Gumuspinar area, too. Climate together with soil properties, elevation and topography is determining for the occurrence of certain plant communities.

Phytogeographical and floristic aspects

What immediately catches the eye of the observer is an extended area of broad-leaved deciduous oak dominated coppice woods. Startling is the prevalence of species occurring also in Middle Europe. Most of the plants, in fact, belong to the Euro-Siberian floristic region, spanning, as the name implies, over Europe and Asia. This region comprises a strip along the coast and the mountain ranges in the north of Turkey. Our study area more precisely belongs to the Euxine subregion (Atalay, 1994), located around the western and central Black Sea region. The origin of the denomination Euxine lies simply in the Latin name for the Black Sea, which is Pontus Euxinus (www.thracian.info). In terms of species composition the pattern follows that of oak mixed stands on the Istranca mountain slopes towards the Black Sea as descibed in Kayacik et al. (1978) and Atalay (1994).

Does the wall alter the vegetation pattern of the area?

Before answering the question we have to look at the horizontal cross section of a random piece of the wall. Originally it was 3-5 meters high and 3,3 meters thick, flanked by a ditch and an outer work to the front (the NW side) and a patrol road behind the main structure (the SE side) as reported in Freely (1998) quoting James Craw. Materials used in the wall comprise pinkish mortar with bricks in the centre and tight fitted blocks of limestone on the outside; The ruins of such a construction give origin to particular microhabitats:

i) a ditch filled with organic matter and debris providing favourable conditions for growth in terms of nutriments and moisture.

ii) a platform on the top with less favourable growth conditions and

iii) slopes consisting of eroded construction material and organic matter.

No clear delineations of the micro-habitats described above can be made since time, vegetation and forestry have eroded the wall significantly. The forests along and on the wall are cut in regular cycles of usually 20 years (DHKD 1999). In the view of all this we can start to look for plant aggregations that could be particular to the wall. The English domination of the species follows Akalin (1952).

i) Oaks prevailing (supposingly Quercus dschorochensis, Q. frainetto, Q. pedunculiflora, Q. infectoria since these species were reported for the Belgrad forest by Yaltirik et al. 1978) with narrow crown closure and almost impenetrable undergrowth of prickly ivy or salsaparilla (Smilax excelsa) and Clematis ssp..

ii) Open crown closure of species mainly other than oaks, such as hazel (Corylus avellana) the European hornbeam (Carpinus betulus), the manna ash (Fraxinus ornus), common maple (Acer campestre), juniper (Juniperus ssp.) and oriental beech (Fagus orientalis). Often covered with ivy (Hedera helix).

iii) Mixed hornbeam (Carpinus betulus, C. orientalis), oriental beech (Fagus orientalis), oak (Quercus cf. petrea, Quercus cf. frainetto), linden (Tilia ssp.) and ash (Fraxinus ssp.). Among the shrubs haw thorn or black thorn (Crataegus ssp.), dogwood (Cornus sanguinea), medlar (Mespilus germanica) were recorded. In the undergrowth ivy, knee holly (Ruscus aculeatus and R. hypoglossum) and rarely holly (Ilex cf. aquifolium). Between rocks sometimes ferns (Polypodium ssp., Asplenium cf. onopteris).

In order to draw more accurate and comparative conclusions, the flora of the woods in the vicinity of the wall, but not pertaining to the wall section was investigated. The total control area is 2 x 50 m x 50 m.

Control area 1:

Culled (clean) coppice forest with dominant oak. Unlike the woods along the wall, enough light falls on ground to allow growth of grass.

Tree layer (ca. 7 m high): almost pure stands of oaks (Quercus ssp.), sporadic medlar (Mespilus germanica), Hornbeam (Carpinus orientalis) and ash (Fraxinus ssp.); shrub layer (higher than 1 m) missing; ground layer: Brachypodium sylvaticum, cock`s foot (Dactylis ssp.), sedge (Carex ssp.), Clematis ssp., knee holly (Ruscus aculeatus), oak (Quercus ssp.), haw thorn or balck thorn (Crataegus ssp.), ivy (Hedera helix), prickly ivy or salsaparilla (Smilax excelsa), wild service tree or chequer`s tree (Sorbus torminalis), and heath (Erica ssp.) only on open spots.

Control area 2:

Culled coppice forest with dominant oak; this growth is older than the one in area 1.

Tree layer (ca. 8 m high): almost pure stands of oaks (Quercus ssp.), sporadic with ash (Fraxinus ssp.); shrub layer (higher than 1 m): haw thorn or black thorn (Crataegus ssp.), dogwood (Cornus sanguinea), medlar (Mespilus germanica), wild service tree (Sorbus torminalis) oak (Quercus ssp.), ash (Fraxinus ssp.); ground layer: Brachypodium sylvaticum, salsaparilla (Smilax excelsa), Clematis ssp., ivy, and knee holly (Ruscus aculeatus)

Discussion

At the present state the wall structures are difficult to access due to thick growth on and around it. Hence, defining the location of the ditch had to be done through intuition. Traces of the outer work of the wall were not seen at all. It seems as if the vegetation on the wall had been coppiced at an earlier point of time than the surrounding wood parcels as slow growing trees and shrubs appear on it, which are missing in the control areas. The coppice type of wood management is considered sustainable since it does not contribute to the degradation of the near-natural oak woods occurring in the area. Only the stems of the oldest trees are taken, whereas the stocks stay in the ground. The timber is mainly used as fire wood or for charcoal production. We find ourselves in probably the largest and oldest remaining areas in Europe where this type of forest management is still practiced (DHKD, 1999). Stumps produce new stems and also seedlings or younger trees contribute to the successive closure of the woods again, so that soil is not being eroded. Keeping the ground covered protects the habitat from the invasion of non native wood species, such as the false acacia or the tree of heaven. But now back to the wall. Does the growth on it differ from the surrounding woods?

Ad i) The growth on the site where the ditch might have lain is similar to the surrounding woods. The oak bush is growing thick here.

Ad ii) No oaks have been recorded on the top of the wall, but rather species adapted to grow on thin stony soil or able to cope with dryer conditions such as juniper and manna ash. Vegetation is thin spread; yet, due to the nearby trees, light-incidence is often inhibited. Thus, herbaceous plants or grasses are missing. On the top of the wall, there are also some of the more `demanding` species, that are mainly found on the slopes of the wall.

Ad iii) The slopes are a habitat for species that like deep grounded rather fresh soils such as the oriental hornbeam, the linden tree, the common ash and last but not least the oriental beech and the holly. Also ferns that like fresh and dark corners grow in the wall’s humus rich-debris.

As we discussed, the growth around the wall is indeed slightly different from the adjoining woods, that don’t have much of hornbeam, linden or beech and have no ferns in the ground layer. The immediate wall surrounding seems to offer better water supply, perhaps coming from the deep grounded soil accumulated in the ditch. Trees on the top of the wall can still access the moisture through their root system widening the gaps in the wall and creating new ones. The wall is richer in species than the control areas. Slow growing trees and the ones that need dark conditions to germinate, such as the oriental beech has a chance here, because cuts seem less frequent. On a large scale, however, we cannot claim the growth on the wall outstands the leading vegetation patterns, since we only talk about a manmade niche that resembles natural conditions likely occurring elsewhere on the hilly outskirts of the Istranca Mountains.

Some further points to discuss

· Basically, similar vegetation could be found on rocky grounds under bluffs as it occurs after rock falls, as seen in Incegiz.

· What will happen to the wall in 50, 100,1000 years?

· Afforestation with non native umbrella pine (Pinus pinea) in Altinpinar

· Conservation: get rid or not to get rid of the vegetation?

-woods helped to preserve it over centuries

-woods are contributing to its destruction. Roots penetrate the structure, release chemicals speeding up its erosion

· propagate knowledge about the wall among citizens or not?

-people might vandalize the site or use it for low quality commercial activities

-illegal building

-negative example Incegiz

References

to be added soon