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Gunung Leuser National Park (Gunung Leuser NP) is a conservation region in Indonesia with a relatively high diversity of flora and fauna. One of the potential species found in Gunung Leuser NP is Keruing. Keruing or Dipterocarpus spp. known as potential of wood and non wood producers with a high economical value and is often a target for exploitation. Habitat destruction and regeneration problems also threatened the species, including associated species with the keruing. The objective of this study were to determine woody species stand structure and regeneration status in Tangkahan forest, Gunung Leuser NP. This research was conducted by purposive sampling method which the plot located based on the presence of keruing. A total of 110 plots were employed for this purpose. Based on the results, the stands in Tangkahan forest formed an inverted J pattern, which is a common structure in natural forests. Individuals with a diameter of 10 cm dominated stands, whereas trees with a diameter lower that 60 cm were the least frequent. The dominance of individual trees in the medium to low diameter class indicates that the forest is still in the early stages of development The vertical structure of the trees at the research location shows that they are mostly from stratum C with 171 individuals, that indicated forest condition is in good condition. The status of woody species regeneration status in the research location is quite variable, with 23 species (34.84 %) in good status, four species (6.06%) in fair status, ten species (15.15%) with poor status, 21 species (31.81 %) in none status, and eight species (12.12%) in new regeneration status. The population structure and regeneration patterns show significant forest degradation due to anthropogenic disturbances. Therefore, conservation efforts are still needed especially for high value species. [ABSTRACT FROM AUTHOR]

The rhizosphere defined as zone surrounds the root that it physical, chemical, and biological character directly influenced by root activities. The rhizosphere is characterized by high microbiological activities compared to bulk soil and affected the plant performance. The objectives of this research were to determine soil respiration and total population of soil microbes, including fungi and bacteria, phosphate solubilizing microbes, and organic matter decomposer microbes. Soil samples were collected from rhizosphere zone (0-20 cm) of kemenyan bunga, kemenyan durame, kemenyan batak and kemenyan minyak in Pardomuan village, Sitellu Urang Julu-Pakpak Bharat, North Sumatera. Microbial population was calculated using plate count method and soil respiration measured using jar methods. The result showed that the highest fungi and bacterial population were found under kemenyan durame rhizosphere those were 13.4 x 107 and 15.7 x107 CFU mL-1. The highest phosphate solubilizing microbes population (96.8 x104 CFU mL-1) was also found in kemenyan jurame rhizosphere. The highest organic matter decomposer microbe found in kemenyan minyak rhizosphere those were 25.1 x104 (fungi) and 73.2 x 104 CFU mL-1 (bacteria). The highest respiration (3.23 mg CO2 100 g-1 day-1) was also found in kemenyan jurame rhizosphere. [ABSTRACT FROM AUTHOR]

Pasak bumi (Eurycoma longifolia Jack) is a shrubs growing wildly in the forests of Southeast Asia and widely used throughout the region because of its medicinal properties. Uncontrolled harvesting of wild-grown trees has led to rapid decrease of it natural populations, as well as causing a potential decrease in genetic diversity. Information about population genetic of pasak bumi still not determined yet, including the optimal DNA isolation and it reference marker. Therefore, our research was conducted to get information about optimal DNA isolation using CTAB methods and reference marker for population genetic study. DNA isolation was conducted through CTAB (Cetyl Trimetyl Ammonium Bromide) method. The yield DNA was PCR amplified using four barcoding standard marker those were ITS, matK, rbcL and trnL-trnF. The result showed that CTAB method was able to yield good quality DNA and 30% dilution produced the best band. The trnL-trnF primer was able to amplified DNA of pasak bumi with 50°C annealing temperature, rbcL with 55°C annealing temperature and ITS with 50°C annealing temperature. While the matK primer failed to amplified. [ABSTRACT FROM AUTHOR]

Soil fertility is the ability of the soil to provide nutrients needed by plants to support their growth and reproduction. The aimed of this research was to analyze of soil acid (pH), carbon organic, and cation exchange capacity (CEC) on rubber agroforestry and rubber monoculture land in Simalungun Regency, North Sumatra, Indonesia. Soil sampling is done by making 10 points of soil sample holes in a composite manner. Soil samples were taken with a depth of 0 – 10 cm and 10 – 20 cm. Differences of soil fertility between rubber agroforestry and rubber monoculture was analyzed using the independent T-test. The characteristics above indicate that there are differences in land use systems in the rubber agroforestry land is mixed with seasonal crops such as cocoa, while in the rubber monoculture land system, only one main type of crop is planted. The level of the content of pH, C-organic, and cation exchange capacity (CEC) found in monoculture land and rubber agroforestry has the same criteria, namely low. This research shows that there is no significant difference in each soil chemical parameters. [ABSTRACT FROM AUTHOR]