Arboretum as Carbon Stock and Carbon dioxide Uptake to Support the Realization of Green Campus at Riau University

The University of Riau Arboretum is one of the natural environments contained within the campus, having various types of vegetation that can be utilized to support the realization of a green campus. This study aims to determine the benefits of arboretum as carbon reserves and CO2 uptake to support the realization of Riau University's green campus. Research using survey methods by observing in the arboretum. Determination of sampling locations by purposive random sampling by considering the condition of vegetation and topography. Research parameters are: (1) vegetation analysis; (2) carbon stocks and (3) CO2 uptake. The University of Riau Arboretum has a vegetation composition in all strata, namely seedlings, saplings, poles and trees. The number of individual seedlings is higher than other strata, namely 349 individuals. Diversity index in all strata classified as high criteria ranged from 3.22 to 3.42. The total carbon stock of 1.12 tons / ha and CO2 absorption of 4.11 tons / ha, with the arboretum of Riau University (± 10 ha), the CO2 absorption that occurs is 41.1 tons. Thus the existence of arboretum can be used to further optimize its function as carbon reserves and CO2 absorption in realizing the green campus program of the University of Riau. Keyword: Arboretum, carbon stock, CO2 uptake Received 15 November 2019 | Revised 29 December2019 | Accepted 29 January2020


Introduction
The University of Riau's Binawidya campus has a large area with interesting topographical and landscape conditions. The Tri Dharma of Higher Education is expected to be able to support government policy by implementing sustainable development. Campus activities are carried out by integrating the environmental (ecological), economic and socio-cultural components of the community in Riau Province. To achieve this we need a green campus management strategy.
The Green Campus Program aims to make the campus environment a comfortable, clean, green, beautiful and healthy place. Understanding green campus in the context of environmental preservation is not just a campus environment filled with green plants, but a deeper meaning that is the extent to which campus residents can utilize existing resources within the campus environment effectively and efficiently.
Environmental problems are joint problems that require synergy of all elements of society, including the academic community. The academic community has great potential in building integrated, comprehensive and sustainable environmental management, because it is necessary to develop a concept that can unite all elements in an environmental management system.
One of the resources available at the University of Riau is the arboretum. The term arboretum describes a Green Open Space (RTH) which is planted with various types of vegetation which have the main function as an integrated educational facility with various other important roles.
The existence of the arboretum is very important in realizing the green campus program.
The University of Riau Arboretum has an area of ± 10 ha that has experienced succession and is used as a place to facilitate the learning process, practicum and research. Based on observations is one type of lowland forest that is quite good and has a variety of flora, but so far no research has been conducted to obtain information on the carbon stock content stored in living plants in the area. The presence of arboretum with the vegetation in it is expected to increase oxygen production and filter out polluted particles in the air thereby increasing environmental quality.
The structure of forest vegetation in tree strata has the ability to absorb pollutant gases such as In addition to acting as a carbon storage store, arboretum is one of the Green Open Space (RTH) that produces oxygen and can indirectly reduce air pollution at the University of Riau.
According to Simpson and McPherson [2], the absorption of carbon dioxide by green open space with 10,000 trees aged 16-20 years can reduce carbon dioxide by 800 tons / year. Planting trees results in the absorption of carbon dioxide from the air which is then stored as carbon reserves in the form of biomass until the carbon is released again because the vegetation is rotten or burned. IPPC [3] states that this is due to the green space that is managed and planted will cause carbon sequestration from the atmosphere, then a small portion of the biomass is harvested and / or logged in a ripe or decayed condition. Therefore, the presence of arboretum is important for the University of Riau to maintain the beauty of the environment and create conditions conducive to the learning process on campus. Based on these problems, it is necessary to conduct research on "Arboretum as Carbon Reserves and CO2 Uptake in Creating Green Campus of Riau University".

Materials and Methods
This research was conducted at the University of Riau Arboretum with a purposive random sampling method by considering the condition of vegetation, environment, and topography. The tools and materials used in this study were digital camera, stationery, rope, fabric meter, wood

Result and Discussion
Based on research that has been carried out in the arboretum area of Riau University campus, it is found the composition of families, types and number of individuals in each stratum, which can be seen in Table 1 below.  Table 2, it can be seen that the diversity index of seedlings, saplings, poles and trees has a range that is not too much different, namely between 3.22-3.42 with a high category.
According to Shannon Wienner [9], if the diversity index value is less than 1, it means that species diversity is low, if between 1-3 means moderate species diversity, if greater than 3 means high species diversity. Pole species diversity is higher than other strata, this condition will affect the level of diversity of stakes and seedlings, because the stratum strata that have a tight canopy so that species that cannot stand with low light intensity are unable to survive.
Carbon reserves are determined by calculation of tree biomass. Carbon stock represents 50% of the calculated tree biomass. Whereas CO2 absorption is determined by calculations using carbon stock data. The results of the calculation of biomass, carbon stocks and CO2 uptake in tree strata at each of the University of Riau arboretum locations can be seen in Table 3. Arboretum based on the results of the study has a value of 11.2 tons and is included in the low category.
Arboretum has great potential as a carbon sink and CO2 absorber. Forest sustainability will be maintained naturally because it has high species diversity and is dominated by small diameter trees (<20 cm). These small diameter trees will make a major contribution to increasing carbon stocks and CO2 absorption in the future. Increasing carbon stocks and sequestering CO2 can be done through the addition of tree reserves in existing forests. Tree planting and maintenance activities are the easiest way to increase carbon and CO2 reserves because trees are able to absorb carbon and store it as biomass in the trunk. A good management of the University of Riau Arboretum will have the potential to increase the ability of vegetation to absorb and store carbon that is useful to support the green campus program.

Conclusion
The University of Riau Arboretum has a vegetation composition in all strata, namely seedlings, saplings, poles and trees. The number of individual seedlings is higher than other strata, namely