Medan is the capital city of North Sumatra Province. It is one of the biggest cities on Sumatra Island. Big cities in Indonesia generally have problems with environmental degradation. One of the efforts to preserve the environment in urban areas is to provide public green spaces. Ahmad Yani Park is a green space dominated by trees that grow compactly and tightly in 1.3 ha of area. The research has been conducted at Ahmad Yani Park, one of the favorite places for people to gather and enjoy the freshness of clean air. Research on tree diversity in several public green spaces is needed to conduct as one of the efforts to provide biodiversity data and information in urban. This research is aimed to analyze the tree structure, composition, and diversity in Ahmad Yani Park to support sustainable development goals, especially in an urban area. The parameters of vegetation collecting by using census methods. The condition of vegetation and environment were assessed by using relative density, Shannon Wienner Diversity Index, and Evenness Index. The Ahmad Yani Park contained 240 individuals of 32 species It dominated by 62 individuals of Mahogany (S. macrophylla). The dominant vegetation is in 20 - 150 cm diameter class (59%). It is a mature phase of tree. While the juvenile and seedling stage have 26% and 15%. The Ahmad Yani Park has 2.75 score of Shannon Wiener Diversity index. It means this park is moderate diverse with a fairly stable environment.

Medan is the capital city of North Sumatra Province and the biggest city on the island of Sumatra. Big cities in Indonesia generally have problems with environmental degradation. One of the efforts to preserve the environment in urban areas is to provide public green spaces dominated by trees. In the process of its life, the tree experiences many disturbances and interventions from the surrounding environment. It can make it grow abnormally or become sick. One of the negative impacts of this is when extreme weather occurs and causes trees to break easily, fall, and fall on whatever is underneath. It can cause various material losses and even fatalities. The research has conducted at Beringin Park in Medan. It is one of the favorite places for people to gather and enjoy the freshness of clean air. Research on tree health surveys and inventories in public green spaces is important to do as one of the efforts to mitigate the occurrence of fallen tree disasters. This research is aimed to take an inventory of tree health in Beringin Park as an mitigation effort of the fallen tree disaster in Medan. Vegetation parameters were collected by using the census method at the pole and tree stage. The Shannon – Wienner diversity index has used to assess the biodiversity level of the research location. Then damage level index was analyzed by using Forest Health Monitoring Method. The results showed that the tree vegetation in Beringin Park was in the healthy category based on the Tree Damage Index Value which ranged from 1.20 to 4.10.