The low diversity of vegetation seedling and sapling threatening the tree existence at the university green space of Universitas Sumatera Utara, Indonesia

Abstract

University of Sumatera Utara (USU) located in the densely populated urban area and committed to maintain the vegetations of green space which are fundamental to the key indicator in green campus ranking. Green open spaces are a vital element in urban areas providing the comfortable-healthy spaces for urban communities and numerous of environmental services. Specifically, the quality of environmental services depends on the extensive of green spaces, climate characteristic, and existing vegetation as the natural element at the area. Vegetation analysis is the method to study the composition, structure, and form of plant communities that is a prerequisite for describing diverse ecological processes and dynamics of species community in a forest. This study aims to analyze the important value, diversity, evenness, and richness index of USU green space vegetation based on the growth levels from seedlings to trees. The sampling plot was quantified using 2% sampling intensity and positioned with a simple random method. Species name, individual and species number, diameter at breast height (DBH), and stand height were recorded in the designated plots and subplots for each life stage. This research documented 21 species belonging to 12 families at USU green space. Swietenia mahagoni was the dominant species at all growth level with the IVI of 141.07 % (trees), 144.21 % (poles), 133.33 % (saplings), and 135.37 % (seedlings). The species diversity of trees and poles was moderate (H’= 1.6 – 1.7), whereas of saplings and seedlings was low (H’= 0.6 – 0.7). Vegetation evenness at all growth levels was high (E= 0.6 – 1.0). The species richness of trees was identified as moderate (R= 3.5) and of seedlings, saplings, and poles was low (R= 0.2 – 2.5). The seedlings and saplings were inadequate indicating the poor regeneration threatening the tree existence at USU green space.