The Effect of Urban Plantation on Absorption of Greenhouse Gases: A Case Study Report of Pardisan Eco-Park, Tehran

0271-B2

Changiz Ashraghi^[1]

Abstract

CO₂ emissions have increased in recent years in the cities of developing countries, due to heavy traffic and low quality fuel. In order to test if a significant proportion of carbon could be absorbed by urban trees, a study was carried out in the Pardisan Nature Park in Tehran, which covers 175 ha. All trees were inventoried and the annual biomass production of three principal species was measured.

It was found that, including carbon stored in the soil, about 3.7 tonnes of C/ha/year were absorbed, equivalent to just over 2 000 litres of gasoline. It was thus concluded that the CO₂ produced by the traffic could not be absorbed by the plantation and that other solutions should be sought.

Introduction:

After the industrial revolution in 1780, due to the dense production and increasing the consumption of energy resources specially coal, air pollution phenomenon and enhancement of greenhouse emerged. Finally in 1905, the first conference on air pollution was established in London, and attention was drawn to the consequences of air pollution.

Until 1960, coal was accounted as the main resource of industrial fuel. After that, using the oil product in supplying energy in industry, the rapid development of industry, population growth of the world and high consumption of industrial goods led to increasing the fuel consumption either in production units for heating and equilibrating the temperature, cars consumption fuel and also rapid tree cutting of the forests as well as the destruction of ranges and finally increasing the concentration of greenhouse gases in the atmosphere. The rise of atmospheric concentrations of greenhouse gases creates the increase in global temperature.

In fact, energy consumption results in increasing the greenhouse gases production. It means that by expansion of industry in the countries, the emission of greenhouse gases is ever increasing and release the various gases will be created the greenhouse phenomenon, population growth in developing countries, and will generally, therefore, bring about the destruction of forests and ranges. This causes the disappearance of absorbing resources of Co2 and finally burning of these resources cause increases in production of greenhouse gases.

Due to the optimum consumption of energy in industrial and developing countries, the rate of productivity is very high. On the other hand, lack of population growth in these countries controls their role in the production of greenhouse gases.

In 1990, six (6) billion tons carbon equivalent to Co2 has entered to the atmosphere. An average of 1 to 2 P.P.M of atmospheric concentration of Co2 has been increased per year, so that this rate will be reached to 400 P.P.M by 2020. This is to explain that before the industrial revolution in 1994, atmospheric concentration of Co2 has been estimated 28 P.P.M and 356 P.P.M respectively.

The main producer of Co2 in industrial countries is America and China, that America alone enters 1.5 billion tons to atmosphere.

The functional results of the above mentioned gases increase the warming global through returning the high heat wave of the sun to the earth and enter to atmosphere. Since 1980, according to the existing statistic, an average of 0.3 - 0.6 have been increased annually.

On the basis of Rio conference, the countries by signing the climate change's Convention committed themselves to returning Co2 emission to 1990's levels by the year 2000. But some of the countries have done activity in this field successfully including:

- Czech Republic
- The Netherlands
- Switzerland
- Denmark
- England

Chosen index in the field of production of greenhouse gases for each person and/or for each production unit is (G.D.P).

To reduce the greenhouse gases to 1990's level, the following ones should be done:

1- Controlling the emission resources.
2- Increasing the absorption and storation resources.

Forests and seas are considered as the best absorbent of Co2. There are numerous statistic and figures on absorption of the greenhouse gases by plantations. This study has been conducted to quantify and mention the actual figures on absorption of Co2 by plantations.

In this study, to determine the volume and weight of the stored Co2 by trees, the annual produced biomass was measured. Measuring the stored carbon in the soil of this region and comparison with sample regions without trees, the carbon dioxide equivalent to stored Co2 in the soil was calculated. Thus, it is possible to calculate the absorbed Co2 by urban plantation.

I believe that trees have capabilities to absorb and store the carbon dioxide, in long-term. Other green spaces can do this but after short-term, large portion of the stored Co2 return to the Nature cycle. Moreover, using the high animal fertilizer consumption, regarding to CH4 and N2O emission, lead to increase the greenhouse gases production.

The existing figures in the declared statistic show that an average of 76% of the surface parks of Tehran city is covered by green areas and 30% of which is covered by tree planted surface. An area of 67% of Local Park is green space and 50% of which is covered by tree planted surface.

Therefore, to control the greenhouse gases cannot be rely on the existing area statistic of parks and green spaces? With rely on the studies done and identify the product resources of Co2 and estimate the capabilities of absorption of it by green spaces and plantations, can be found the solution to problems. It is impossible to control the greenhouse gases through absorb it but will be led to compile a planning in order to limit the rate of production and its resources.

Materials and Methods

1- Summary of geographical characteristic of the site:

Pardisan Nature Park is situated in the Northwest of Tehran in Farahzad region. It is located between 35. 44' North latitude and 51.23' East longitudes. It's height from level of sea is 1360 m. This region with an area of 270 hectares is located between central desert of Iran and Alborz foot of mountain. In view of geomorphology, Pardisan Nature Park has many Northern and Southern valleys that the most important of them is Farahzad one.

Since 1973, this region has been considered for constructing the Pardisan Nature Park. Its soil consists of the transferred alluvial articles from Alborz chain of mountains as follows:

1- Sandy
2- Clay silt
3- Clay red
4- Gravel

According to existing meteorological statistic of 10 years in Mehrabad station, the average annual precipitation is 250.7 mm/year. The average frost day is 42.8 days. In November, the maximum range of precipitation is 17.6 mm per day. The potential transpiration and evaporation is 1771.9 mm. with a maximum of 272.49 mm.

Its climate type using Dumarton method (L=P/1+10=8.87) is considered as arid climate and using Amberje method (Q2=2000P/M2-m2=22.57) is accounted as arid climate with cold winter. Used resources for irrigating the various subterranean canals, is Farahzad River.

2- Vegetation Cover of the site:

There is no significant difference in Macroclimate of the region, so plant species depend on the Microclimate and soil type, direction, gradient and the available water. So far, 138 plant species in this region has been identified. The species type comprises:

- Shrub species
- Annual species
- Perennial species

3- The existing vegetation Cover:

Tree planting in the park began in 1974. At present an area of 175 hectares of this park is covered by tree planting. The main aim has not been used in selecting the species. For this reason in planning of biomasses, the main part of planted trees will be substituted.

Table 1: The percent and area (Hectare) of the planted areas

4- Selecting the species to inventory and calculating the increment

On the basis of the mentioned table and in order to measure the volume of biomass production, three species including Robinia sp., Cupressus arizonica and pinus eldarica was chosen which 79.6% equivalent to 139 hectares of the planted area is covered by the mentioned three species.

5- Inventory Method:

The randomized block design was used in this method. The plots were chosen according to the species type and age. The site which is covered by the mentioned species was divided equally into 17 plots as follows:

8 plots of Cuperssus arzonica
2 plots of Pinus eldarica
7 plots of Robinia pseudo acacia

The volume of the crown and root with intensity of 5 percent was measured.

6- Calculation method of produced biomass rate:

6.1. Diameter: Using the calliper, diameter at breast height and diameter at collar of trees was measured and then was recorded in the relevant tables.

6.2. Height: The main factors to calculate the tree volume is height. In inventory, the total height was used. In other words, we can say: Tree height from the ground on the top of the crown. In order to measurement, the following methods were done:

a) Using the experimental or estimated method to the short height tree
b) Using the clinometers to the tall height of tree.

6.3. Measurement: of the increment volume and the biomass production: In addition to diameter height at two methods, also inventory volume table was measured.

Trunk shape of the tree with the coefficient of 50% was considered to calculate the volume.

By cutting and measuring the weight of some of the trees, the branches as compared with the main trunk of Robinia pseudo acacia were accounted 19%, in Cupressus arizonica 26% and in Pinus eldarica 25%. The roots weights were also measured on volume basis which as compared with the main trunk of Robinia pseudo acacia were accounted 15%, Cupressus arizonica 10% and Pinus eldarica 17%. In this connection, the increment volume was measured considering the age of the trees and annual biomass production. In order to compare resulted percentages with the standards, the reference book of Society of American Foresters were used which the standards of different species are ranged from 17% to 23%. As compared with root volume to the main trunk and 15% to 25% in crown canopy volume and subsidiary branches to the main trunk. Therefore, the calculated figures were within the stated ranges.

7- Measuring the stored Co2 in the soil:

To measure the carbon weight equivalent to the stored CO₂ in the soil which were caused as a result of irrigation and microclimate of the trees through humus, the soil of the blocks in depth of 0 to 30 cm. were sampled which due to soil relative evenness, a composed sample of the blocks soil under cultivation of Robinia pseudo acacia, a composed sample of the blocks soil under cultivation of Cupressus arizonica and a composed sample of 13 sample soil of the areas with no vegetation cover were selected and tested in the laboratory in order to disintegrate them so to compare their organic matters and organic carbon.

Results:

1- The annual produced biomass by various tree species per year/hectares:

After measuring the inventories and produced biomass of the plantations the annual increment volume rate of biomass of different species per ha. were measured as follows

Table 2- Annual increment of various parts of trees depending on species:

As shown in the table, the volume of produced biomass per ha/year by Robinia pseudo acacia were more than the other species. Of course, the above statistics cannot demonstrate definitely the species increment in comparison with each other, because the trees age is different and to compare the species increment volume, it should be done under even age.

2- The annual absorbed Co2 rate by the plantation of Pardisan Nature Park:

By generalizing the annual production to the area under cultivation in Pardisan Nature Park averagely 175 hectares produce 292 m3 biomass annually which is equivalent to 1.66 m3 per hectare. Considering the Co2 absorption as compared with carbon, the annual increment per ton, is stored 260 kg. Carbon equivalent to Co2. By calculating the special weight of the mentioned trees (0.7) 302.12 kg. Carbon equivalent to Co2 is absorbed and stored per hectare annually.

Regarding the plantation area in Pardisan Nature Park, the annual average produced biomass is 53141 kg. Carbon equivalent to Co2 which is absorbed and stored.

3- The stored carbon rate in the plantation soil:

The results of sampling soil disintegration shows that the organic carbon rate in the soil without vegetation cover is 0.59% in the soil under Robinia pseudo acacia 1.22%

It shows that there is an obvious difference between organic carbon percentage of the soils being planted by trees and the soils without trees. Therefore, we conclude that regarding the plantations age and percentage difference of organic carbon of the lands without trees, the annual absorption of organic carbon in comparison with the lands without trees is more than (0.026%) by accounting soil volume in 0 to 30 depth and the specific gravity of soil, the carbon rate equivalent to Co2 which is absorbed by the soil in a year amounts to 606060 kg. which is considerable in comparison with carbon equivalent to Co2 absorbed by the produced biomass. Of course, this variation is acceptable and rational because the carbon rate equivalent to the stored Co2 in the forest lands is at least 6 times more than Co2 rates absorbed and controlled by the forests.

4- The plantations role in Co2 absorption:

Considering the above figures and Co2 rate absorbed by the soil, the vegetation cover of plantations in Pardisan Nature Park is 3766.88 kg. Carbon equivalent Co2 per hectare which stores and absorbs from the atmosphere and emits from Co2 cycle.

Discussion and Conclusion

According to evaluation made we would reach a number that plantation per hectare of Tehran and Pardisan areas can absorb 3766.88 kg. Co2 annually. Now let us know how much is the capacity of green areas and planted areas for absorbing of Co2 and or whether the problem of greenhouse gases production and their controlling can be removed?

On the basis of issued statistics by Ministry of Oil in 1999, daily gasoline consumption in Tehran amounts to 8012000 litres. This amount is equivalent to 20.5% of the total amount of the country gasoline consumption per day, which in comparison with the consumption of other fuels in the country contains 23% of total daily fuel consumption. This number of course does not include consumption in urban gas networks of the country. Now to be enabling to obtain the capacity of Tehran green spaces for absorbing Co2 and its producing, we need to calculate Co2 produced through gasoline consumption.

According to calculation done, each mega Joule energy depends on the fuel type produces great amount of Co2, some of which is as follows:

Coal release 93 of Co2 in exchange for production of one mega Joule energy.
Oil release 77gr. Co2 in exchange for production of one mega Joule energy.
Natural gas release 53 gr. Co2 in exchange for production of one mega Joule energy.
Hydropower energy release 28 gr. Co2 in exchange for production of one mega Joule energy.

On the basis of the calculations, each ton of the following fuels releases the energy as follows:

One kg. Of liquid gas produces 45 mega Joule energy.
One kg. Charcoal produces 30 mega Joule energy.
One kg. Oil produces 43 mega Joule energy.
One kg. Dry wood produces 15 mega Joule energy.
So, considering the above figures each ton of oil produces 43000 mega Joule energy and each mega Joule energy releases 77 gr. Co2.

Therefore, one ton oil releases 3311000 gr. Co2 which considering oil special weight and volume, each litre of oil releases 2648 gr. Co2. Now we do this calculation about gasoline.

On the basis of the daily consumption of 8012000 litres of gasoline and about 2,924,380,000 litres consumption yearly in Tehran, the amount of annual Co2 would be 7743768 tons.

Considering the absorbing capacity per hectare which is 3767 kg. Yearly, required planted area for absorbing Co2 and controlling greenhouse gases will be equal to 2.555.683 hectares. As we see, the figure is very huge and is equal about 70 to 75 of Tehran green spaces.

These figures are only a presentation for a part of 22% of Tehran energy consumption and the imagination that plantation and green area would be able to control Co2 production and other fuel pollutants which is not considered in this calculation, is inaccessible. However, the following recommendations is suggested for controlling all pollutants and greenhouse gases which would partially resolve the Tehran air pollution issue along with policy making the government and public training:

1- Developing green areas through possible methods specially a forestation and tree planting.

2- Optimum preserving and improving of green areas specially trees and forestations and investigating on fast-growing and adapted species.

3- Converting assembly line of manufacturing of cars with high rate of consumption to reach international standards.

4- Improving public transporting network.

5- Preventing unnecessary transportation, honesty answering of the governmental organizations towards people by telephone and developing of mail and Email.

6- Establishing of bicycle riding lines and encouraging the people to walk rather than in a vehicle.

7- Monitoring of cars speed to optimize fuel consumption.

8- Substituting clean energies for fossil fuels.

9- Encouraging people and training them for using less energy especially through insolating and optimizing buildings

10- Developing of green architecture for optimum productivity of sun light, the direction of buildings and establishing green area to reduce energy consumption for heating and chilling.

References:

1- Ashraghi, Ch., 1990, The Global Climate Change and the Effect of Plantation and Green areas on Mitigating it's Effect, Forest and Range Organization of Iran.

2- Ashraghi, Ch., 1992, Role of Forests and Ranges of the Country in Supplying Energy, Forest and Range Organization of Iran.

3- Parsa Pajoh, 1991, Wood Technology, Tehran University.

4- Friz, F. Translated by Dr. Hosseinzadeh, 1986, the Preliminary Methods of Statistic in Forestry, Forests and Ranges Research Institute of I.R. of IRAN

5- FAO Unasylva, vol. 41, 1990.

6- Karl F. Wengen, 1986, Forestry Hand book, Society of American Foresters.

7- Sharma, 1996. N.P. Managing the World Forest, World Bank.

8- The Finnish Environment Institute 1996, the Future of the Finnish Environment, Helsinki.