Assessment of carbon sequestration potential of tropical tree species for urban forestry in India

Abstract

Urban, peri urban and patch forests play a critical role in climate change mitigation through increased carbon storage and for that, it is imperative to assess the species response in an eco-region to recommend a potentially higher carbon sequestering species. In urban settings, green spaces, in particular, trees play a vital role in preserving biodiversity, reducing the impact of urban heat islands, enhancing the hydrological cycle, as well as sequestering carbon. When introduced in urban greening projects, native species provide better ecosystem services, conserve and maintain biodiversity more sustainably than exotic species. However, fewer efforts are being made to evaluate the carbon sequestration potential of native tropical tree species in urban greening initiatives. The present study aims to assess the biomass production and carboxylation efficiency of three native tropical tree species to identify the high carbon sequestering species, which will enhance the carbon stocks under urban green spaces. Above ground biomass, carbon stock and physiological performance of three native tropical tree species (Tectona grandis, Mallotus nudiflorus and Syzygium cumini) were measured in Botanical Garden of CSIR-National Botanical Research Institute, Lucknow for eight years old tree stands. Above ground biomass (AGB, Mg/ha) was measured using a non-destructive method by applying allometric equations. Tree height, diameter at breast height (DBH) and leaf area index (LAI) was maximum in T. grandis stand (10.43 m, 29.21 cm, 1.95, respectively). Maximum AGB (71.94 Mg/ha) and carbon stock (25.54 Mg/ha) was observed in T. grandis plantations among the three tree stands. T. grandis stand also had maximum litter fall (5.82 Mg/ha). Highest diurnal photosynthesis rate, water use efficiency and stomatal conductance were also observed in T. grandis stand. However, maximum photosynthetic rate was observed in Mallotus nudiflorus. One way ANOVA revealed significant differences (p < 0.001) in AGB, carbon stock and physiological parameters among the three species. Pearson's Correlation matrix established the positive relationship between growth performance and physiological traits of species with their capacity to sequester carbon. T. grandis can be promoted for urban greening projects for achieving carbon sequestration targets with short time span, however plantation of mixed native species will provide better delivery of all ecosystem services in sustainable mode. Results from the present study shed light on the patterns of carbon sequestration by these species, which in turn will help in the decision-making process for sustainable urban greening. Further, more tropical species can be assessed for their biomass and carbon capture capacities to determine the best species matrix for plantations to enhance carbon storage and develop climate resilient greenbelt under urban landscape forestry programs.