0844-B1

Spatial Functions Expected from the City Groves of Istanbul Metropolis

Ünal Asan^[1] and Ýbrahim Özdemir

Abstract

With its population of approximately 12 million, Istanbul is the largest city in Turkey. Although its natural vegetation cover was severely damaged during the past, it still has some urban forests in the form of city groves and parks. These woody lands in the city play a very important role in the social, cultural and spiritual life of the people. They also fulfil the functions of carbon sequestration, erosion control and dust filtration. Wood and non-wood forest products have no importance in these parks and groves.

Although these urban forests have invaluable beneficial functions for the people of the city, they were not being managed according to serious plans foreseeing the biological and technical needs of sustainable forest management rules until now.

Twelve management plans focusing on silvicultural treatment for the 12 urban forests were constructed as a case study by the staff of the Forest Management Planning Department at the Faculty of Forestry of Istanbul University.

The study consists of two main phases. In the first phase, the capacities of carbon storage, oxygen production and dust filtration of the planning units were calculated. In the second phase, digital elevation models (DEMs) were constructed for each of the groves and slope and aspect maps were derived from these. Three-dimensional (3D) draped terrain models (DTMs), with ortho-photos and the vegetation cover maps were obtained and spatial functional areas were determined on the DTMs.

Investigations showed that the city groves themselves should be protected against the various hazards coming from outside on the one hand, and that they should be used as a protective shield for some human needs on the other hand.

The paper’s main conclusions included the following points:

• Protection of biological sustainability is the prime principle in the management planning of city groves.
• The multiple-use planning concept should be applied during planning activities for the groves.
• Although the aesthetic function might seem the prime function of urban forests, erosion control and soil protection may be more important on the steep slopes.

Introduction

Istanbul, which is the largest city of Turkey, has 80 km length from east to west and 40 km width from north to south approximately. It is divided two parts by the Phosphorus called as Asian and European sides. Natural vegetation cover of Istanbul was destructed highly during the historical eras, but it still has some amount of urban forests in a form of city groves and parks nevertheless. Since it was the Capital City of Ottoman Imperial along 500 hundred years approximately, many palaces and pavilions constructed in the city having large groves and gardens by the members of imperial family and the other executive officers. Because of the peculiarities of the olden usage of these areas, there are many kind of exotic and ornamental tree species beside the native trees and brushes in these groves. Some of the exotic species were planted 150-200 years ago, and they obtained living chance by adapting to the local ecological conditions current around. Although they can be seen all the sides of province they are very sensitive against the abnormal situation caused by air pollution and rapid urbanisation like all the urban forests (Grey 1986). Thus, they should be accepted fragile species compare to the domestic ones. Therefore, the principle of protection has the priority among the fours (sustainability, multiple-use, amenity and protection) from the standpoint of forest management planning practice (Asan et al. 2002) and (Bhuju et al. 1999).

These gardens, parks and groves in the city play very important roles on various human needs such as recreational usage, and common health as well as visual effect and nature protections like erosion control, water yield, visual effect, and the carbon sequestration for climate change. Forest functions such as wood and non-wood forest production, avalanche control, and wildlife development for hunting have no importance in these parklands and groves. The management goals and the silvicultural treatment techniques that should be applied in these woody areas are different compare to the normal forest enterprises from the standpoint of conduct and control planning.

Although these urban forests have invaluable beneficial functions for the twelve millions population living in the city, they were not managed according to the serious plans foreseeing the biological and technical needs of the sustainable forest management rules until now.

12 management plans focusing on silvicultural treatment for the 12 urban forests were constructed as a case study by the staff of Forest Management Planning Department at the Faculty of Forestry of Istanbul University. The items; i) determination of the functional values expected from the planning units on the whole and partial basis, ii) separation of existing vegetation types, and varying forest structures on the ground, iii) finding the silvicultural treatment units as individual trees (having 70 cm or more dbh), heaps, patches, groups, and stands basing on the plant species, mixture ratios, and physical measurements, iv) definition of the optimal unit structures basing on expected forest functions and the unit peculiarities, v) Decision making on the forms and grades of silvicultural treatments that should be applied to the units were chosen as the main aims of the study:

Investigation results realised in the 12 city groves presented that, the city groves themselves should be protected against the various hazards coming from outside on the one hand, and they should be used as a protective shield for some human needs supplied from the groves on the other hand. The following functional values have to be expected from these urban forests existing on the hills and slopes of the Phosphorus in Istanbul;

• Improvement the aesthetic values of the silhouette on the hills, and visual quality of the coloured mosaics on the slopes,

• Facility supply for various sportive activities and recreational usage,

• Assimilation traffic noise, and wind speed decreasing,

• Oxygen production, and polluted air filtration,

• Rain flow regulations and flooding prevention,

• Erosion control and earth sledge protection on the steep terrain conditions,

• Carbon sequestration, and global warming delay by means of CO2 consumption,

• Nature conscience creation in the mind of mankind by means of their colourful plant variety and the monumental trees having insides,

• Inspiration giving to the artisan who are interested in the fine arts such as painting, poetry, and music.

• Protection the historical palaces, pavilions and the other cultural heritages against the destructive effects of nature

• Becoming an open natural laboratory for the scientists for their own research on exotic and domestic plant species.

Management goals of these city groves existing on the hills and slopes of Phosphorus were determined basing on expected spatial functions in the forests. The general algorithm of the study consists of two main phases. The functions and benefits fulfilled by the whole forested areas existing in the planning units such as the carbon sequestration, oxygen production and polluted air filtration, and the functions and benefits appearing spatially on some parts of the planning units such as erosion control, recreation facilities, and the visual effect were grouped separately as the first step in the study. The first phase is completed after calculation the amounts of carbon storage, oxygen production and dust filtration capacity of the planning units (Asan et al. 1998).

The procedure applied in the second phase will be introduced in this paper. Following items were explained for this purpose: i) construction of digital elevation models (DEM) for each one of the groves, and derivation of the slope and aspect maps from DEM, ii) obtaining of the three dimensional (3D) draped terrain models (DTM), with ortho-photos and the vegetation cover maps. iii) Determining the spatial functional areas on the DTM’s.

Material And Method

The material concerning study was collected from various resources such as topographic maps, cadastral maps, ortho-photos, and terrestrial measurements realised either in the whole inventory units or sample plots in order to see the rich diversities of the units (Moll et al. 1993). Small inventory units (individual trees, heaps, patches) were measured completely while the large units were sampling. Dendrometric peculiarities such as number of individual, average dbh and height, plant species, mixture forms and ratios, health situation, and the silvicultural treatment requirements that should be applied in the units were all determined for all the units by terrain works (Yesil et al. 2002). Local positions of 12 city groves are shown in Fig.1

Fig.1: Geographical positions of 12 groves

Following procedure was applied in the construction of spatial forest functions maps for each one of the groves:

1-Boundaries of the planning units taken from the cadastral maps were transferred onto the topographic, and the ortho-photo maps respectively and study areas were isolated on these two maps both. The DEM’s for each one of the planning units were obtained by using the elevation curves with 5 meters intervals in the study areas. ER Mapper Gridding Wizard was used for this purpose (Fig.2).

Fig. 2: Digitising the contour lines

Fig. 2: Obtaining DTM

(from Hacıosman Grove)

2-Compartments in the planning units were separated by means of roads, ridges, and streams on the ortho-photo maps. Sub-compartments (inventory units) were made use of the tree species, mixture forms and ratios, average dbh and heights of the inventory units. Pre-segmentations of inventory units were done on the ortho-photos, and the explicit boundaries of the sub-compartments were defined after checking them on the ground. The spatial distribution maps of varying plant community unite types were constructed by overlapping these two maps (Fig.3/a).

Fig.3: Compartments and sub-compartments,

Fig.3: Draped terrain models in a planning unit

(from Hacıosman Grove)

3-The ortho-photos and plant communities unite maps were merged on DEM’s respectively, and the DTM’s were obtained (fig.3/b). Spatial forest functions expected from the groves were determined by means of these DTM’s for each one of the planning units. Following process applied for this purpose:

a) Erosion risk groups maps construction: Because of the intensive vegetation covers on the ground no obvious erosion evidence was observed on terrain. Thus, erosion risk groups were separated basing on the terrain slopes and the soil properties determined on the ground (Fig.4). The groups accepted in classification is shown below:

Fig.4: Slope map draped on DTM

Fig.4: Erosion risk groups map

(from Hacıosman Grove)

b) Hydrological function maps construction: the spatial areas having hydrologic function were determined basing on the watershed of dams and pools in the planning units.

c) Mosaic effect maps construction: the visual aspects of ridges and hills, and the mixture form and ratios of vegetation covers existing on terrain were based on determination the spatial areas having mosaic effects. Two groups classified in the study. The units consisting of one tree species or species groups (coniferous or deciduous) were included into the second classes, while the units covering coniferous and deciduous trees in the form of heaps or patch mixed were including into the first classes. Invisible slopes and ridges did not evaluated for this purpose (Fig.5).

Fig.5: Top view of mosaic function map, red colour shows invisible areas,

Fig.5: A view from Phosphorus

(from Emirgan Grove)

d) Silhouette effect maps construction: the topographic forms of terrains (hills and ridge) those are seen from the boats sailing on the see, or main roads and high-ways on the land were taken into account in determining the spatial areas having silhouette effect. The dendrometric magnitudes such as dbh and heights of the plant communities existing on a belt having 30 meters width on these areas were considered for this purpose. Two classes were considered during the segmentation of silhouette effects. The parts having the trees with 30 cm or more dbh, and 15 m or more height occupying on the belts classified as the first classes, while the smaller parts were evaluating as second classes (Fig.6).

Fig.6: Determination the silhouette effect areas in planning unit. - top view

Fig.6: Determination the silhouette effect areas in planning unit. - north-east view

Fig.6: Determination the silhouette effect areas in planning unit. - north view

Fig.6: Determination the silhouette effect areas in planning unit. - north-west view

(Varying sight from Hidiv Grove)

e) Recreational usage maps construction: the areas used for recreational purposes separated basing on the actual land use situation, alternative facilities obtainable on the places where the possible topographic feasibility, and the vegetation types. Present and alternative areas suitable for recreational usage were all segmented on the DTM’s of the city groves (Fig.7). Hiking and jogging paths and the belts allocated for walking particularly were also defined as recreational areas.

Fig.7: Present and alternative areas suitable for recreational usage (green),

Fig.7: Present recreational area (yellow), and, jogging and walking paths (blue) in a planning unit.

(from Hidiv Grove)

4- All the functions were considered separately at the beginning and they stored on different layers. After completing the same process for each one of the forest function, all the layers were overlapped onto each other in order to obtain the final map. Each function was shown in different colour on the forest functions map (Fig.8).

Fig.8: Spatial functions map of Hidiv Grove

Conclusion and Proposals

According to the forestry principles accepted by the UNCED in 1992 in Rio, forest resources and forest lands should be sustainable managed to meet the social, economic, ecological, cultural and spiritual human needs of present and future generations on the wood and non-wood forest products, and various forest services (Asan et al. 1998).

These 12 urban forests play very important roles on various human needs such as common health, aesthetic and nature protection beside the cultural and spiritual. Since they are open to all kinds of hazards, biological sustainability of these city groves is the most important gap from the standpoint of management planning. Following conclusions were attained with this case study:

• Protection of biological sustainability is the primer principle in the management planning of city groves,
• Multiple-use planning concept should also be applied during the groves planning activities,
• Although the aesthetic visuality seems the primer function for the urban forests, erosion control and soil protection may be more important on the steep slopes.
• DTM derived from 3D DEM is an effective approach in determination spatial forest functions. Its vast capasity in that course should be used in the forest management planning activities for standard forest enterprices too.

Literature Cited

Asan, Ü., A. Yeþil, S. Destan, 1998. Multi Benefical Forest Use And Functional Planning. Bulgarian Forest Science, No ½, pp. 121-130.

Asan, Ü., S. Destan and U,Y. Özkan, 2002, Estimation of Carbon Sequestration, Oxigen Production and Dust Filtration Capacity in the City Groves of Istanbul, Proceedings of the National Symposium on New Concepts and Targets in Forest Managenet Planning, Istanbul pp.194-202.(Original in Turkish)

Bhuju, D.R., M. Ohsawa, 1999. Species dynamics and colonization patterns in an abandoned forest in an urban landscape, Ecological Research, 14, pp 139-153.

Grey G.W., F. J. Deneke, 1986. Urban Forestry. John Wiley & Sons, 299 p.

Moll, G., C. Kollin, 1993. A new way to see our city forests, American Forests, Vol. 99, Issue 9/10, pp 29-32.

Yesil A., Ü. Asan, U. Y. Özkan and I. Özdemir 2002. Two Phases Forest Inventory Applications In The Urban Groves Of Istanbul Municipality, Proceedings of the National Symposium on New Concepts and Targets in Forest Managenet Planning, Istanbul, pp.158-165. (Original in Turkish)