The Vegetation Composition and Carbon Stock of Old Shrub Typology to Support the Rehabilitation Program in Sumatra and Kalimantan Islands, Indonesia

The typology of certain old shrubs assists with the selection of suitable plant species for rehabilitation. The carbon stock dynamic in old shrubs is fundamental due to their high uptake during the growth process phase. A plot of 100 m × 100 m (1 hectare) was created in each location, referring to the work of Mueller-Dombois and Ellenberg. The plot was further divided into subsquares measuring 20 m × 20 m; in each plot, there were 25 subplots. Research results showed that the diversity index of old shrubs at the tree, pole, and seedling stage is 2.50–2.66, 1.23–1.50, and 0.67–1.11, respectively. For Kalimantan, the diversity index is lower than that on Sumatra Island, which is 1.64–1.80, 1.00–1.02, and 0.52–0.81, respectively. The carbon stock of the old shrub forest in Sumatra has an average of 36.61 Mg C per ha (standard deviation 14.54 Mg C per ha) to 72.50 Mg C per ha (standard deviation 25.61 Mg C per ha), while Kalimantan has an average of 47.94 Mg C per ha (standard deviation 13.30 Mg C per ha) to 144.07 Mg C per ha (standard deviation 54.64 Mg C per ha). The dynamics of the vegetation composition and carbon stock in each old shrub’s typology are considered when choosing a suitable model, including high carbon stock content, to provide optimal results for rehabilitation activities.