Situated on a relatively stable geological terrain and spread across seven hills, Dharwad is a gateway between the plains in the eastern and Western Ghats. Dharwad is one of the largest districts situated in the western sector of the northern half of Karnataka State. The district encompasses an area of 13,738 sq km. lying between the latitudinal parallels of 14°17′ North and 15°50′ North and the longitudinal meridians of 74° 43′ East and 76° East [12]. Karnatak University is a public state university in the Dharwad district of Karnataka state, India, and is spread across 888 acres. The Karnatak University Botanic Garden was established in 1963. It is the only Botanic Garden in the northern part of Karnataka state. It spreads over an area of over 40 acres and is located at an elevation of 830 meters [18]. Floristic diversity refers to the variety of plants and their variation. It is a well-organized complex association having a typical composition (floristic aspect) and structure (morphological aspect), which results from the interaction through time. It can be measured in different levels, from just a number of species in a given area to a complex association with the prevailing ecosystem [17]. The tree biomass is generally determined based on forest inventory data and allometric equations [7].

2.1 Study area: Karnatak University is a public state university in Dharwad district of Karnataka state, India, and is spread across 888 acres. The Bombay legislature of the erstwhile Bombay Presidency established Karnatak University through the Karnatak University Act 1949. It became a statutory University on 1st March 1950. The jurisdiction of the University covers Dharwad. Gadag, Haveri and Uttar Kannada districts. There are 51 PG Departments, 154 teachers, and 4500 students (PG, M.Phil., Ph.D.). Efforts have been put to maintain the beautiful greenery in the campus. Good gardens, Parks and a children’s park are maintained by university garden department and add to the aesthetic beauty of the campus environment. The Karnatak University Botanic Garden was established in 1963. It is the only Botanic Garden in the northern part of Karnataka state. It spreads in an area of over 40 acres and is located at an elevation of 830 meters. The flowering plants represent 170 families and more than 1300 species. have been maintained. This garden also has a small nursery where medicinal plants, rare and ornamental plants are maintained. It is a member of BGCI and IBGN. The Garden is well planned with different sections like 1. Oil-yielding plant, 2. Economic plants, 3. Garcinia section, 4. Coconut Garden, 5. Citrus Garden, 6. Systematic section and 7. Gymnosperms and local flora section. The Garden has both indigenous and exotic sps. from different places [18].

The Garden is a centre of study for students of M.Sc. Botany and various other departments like Zoology and Chemistry. This garden is a centre of attraction for the public, nature lovers and students of different Colleges, including Ayurvedic and Homeopathy Colleges and other Universities for the study [18].

            The average rainfall is 691.1 mm occurring between June to September. April is generally the hottest month with the mean daily maximum temperature at 37.3 ⁰C and the mean daily minimum at 22.5 ⁰C.

2.2 Sampling technique: Tree population was calculated using the Quadrat method. The following parameters were tabulated for the enumeration of total biomass and carbon sequestered. The phytosociological data such as frequency, [3] relative frequency, relative density, relative dominance [13], and Importance Value Index (IVI) [2] were calculated.

2.3 Frequency: Frequency denotes the homogeneity of distribution of various species ecosystem.

2.4 Basal area and Relative basal area: They are studied by measuring the girth at breast height of all the individuals which in turn helps in studying dominance and biomass.

2.5 Importance Value Index (IVI): This index is used to assess the overall importance of a species in the given area. It is obtained by the sum of relative density, relative dominance and relative frequency for each species taken.

2.6 Raunkiaer Frequency Classes: Raunkiaer (1934) summarized frequency data from different studies in diverse areas of Europe [15]. He found that if the total number of frequency distributions was divided into five percentage frequency classes, the distribution frequency was as follows:

2.7 Diameter at Breast Height (DBH): The diameter of the tree trunk can be calculated by measuring the Girth at Breast Height (GBH), approximately 1.3 m from the ground level using a measuring tape. Dividing the GBH by pi (3.14) gives the Diameter at Breast Height of the tree. Only tree poles with a diameter more than 10 cm were considered. The values were tabulated.

2.8 Tree biovolume: The volume of the tree stem can be calculated using the following formula:

2.9 Above-Ground Biomass (AGB): It includes all the living biomass above the soil. Biomass studies were done by non – destructive method using allometric equations. It was calculated by multiplying tree biovolume and wood density. The wood density of the trees were obtained from World Agroforestry Database. The standard average value of 0.6 g/cm³ is taken for the tree species whose wood density values are not available.  It is calculated using the following formula:

2.10 Below Ground Biomass (BGB): It includes all the living biomass below the soil excluding roots having diameter less than 2mm. The below ground biomass was calculated by using the following formula:

2.11 Total Biomass (TB):It includes the complete biomass of the standing tree species. It is the sum of the above and below ground biomass.

2.12 Carbon storage: 50% of the total biomass of a species is its carbon sequestration value. It can be calculated as follows:

3. RESULTS AND DISCUSSION

            The survey was conducted in Karnatak University Campus in 2021 – 2022 for documenting tree diversity and assessing the carbon sequestration capacity. A total of 223 tree species belonging to 56 families and 158 genera were recorded in 80 quadrats. Among which Fabaceae has the highest number of species (41), followed by Malvaceae (16), Bignoniaceae (14), Moraceae (11), Apocynaceae, Meliaceae, and Rubiaceae (8) respectively. Total basal area of all the tree species in the campus is 70.704 m² (Figure 3). Among the listed species majority of the species belong to Raunkiaer’s Frequency class ‘A’, followed by ‘B’, ‘D’, ‘C’ and only two species showing the highest frequency class ‘E’ (Figure 4). About 50,353 individuals were measured for calculating above-ground biomass, below ground biomass, total biomass, and carbon storage capacity. Importance Value Index was calculated using relative frequency, relative dominance, and relative density of all the tree species (Figure 5). Total biomass of the campus is 12.92 tons with Eucalyptus globulus having the highest biomass of 7.59 g/m², followed by Sapindus mukorossi with 7.20 g/m², and Swietenia mahagoni with 6.33 g/m². Total above-ground biomass of the campus is 210.76 g/m² with Eucalyptus globulus having the highest above-ground biomass of 6.02 g/m², followed by Sapindus mukorossi with 5.71 g/m², and Swietenia mahagoni with 5.02 g/m². Total carbon sequestered by all the tree species in the campus is about 3400.53 tons, of which Eucalyptus globulus sequestered highest 32.1 tons of carbon, followed by Tamarindus indica sequestered 3.31 tons of carbon, followed by Mangifera indica sequestered 2.77 tons of carbon, followed by Delonix regia sequestered 2.22 tons of carbon, which is followed by Azadirachta indica sequestered 1.77 tons of carbon being the top five tree species with highest carbon storage capacities (Figure 6).

4. CONCLUSION

            The Karnatak University campus harbors a wide variety of tree species and a considerable number of individuals making the campus green and clean. The trees are largely grown and are home to other living beings such as birds, insects, and other small animals. The carbon storage capacity of the region increases with an increase in standing biomass. The tree species in Karnatak University campus are for the purpose of ornamentation, shade giving, and timber is auctioned officially every now and then, depending on the availability. These trees are sequestering good amount of carbon, hence keeping the campus less polluted and more cleaner air quality. Thus trees such as Eucalyptus globulus, Delonix regia, Mangifera indica, Tamarindus indica, Azadirachta indica, Acacia auriculiformis, Senna siamea, and Swietenia mahagoni, with high carbon sequestering capacities as well as commercial usage, need to be grown in more number.

5. ACKNOWLEDGEMENTS

            The authors are grateful to the authorities of Karnatak University, Dharwad for supporting the work in the campus and also thankful to the authorities of Karnatak Science College, Dharwad, for cooperating with the research work.

ACKNOWLEDGMENT: The authors are thankful to the authorities of Karnatak University, Dharwad and Karnatak Science College, Dharwad for providing support and cooperation to conduct the study.

CONFLICT OF INTEREST: Authors do not have any conflicts of interest and declare the work carried out is original and true to knowledge.

ETHICAL ISSUES: None

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