Ecosystem carbon stocks in different aged tea agroforestry systems: implications for regional ecosystem management

Abstract

Tea (Camellia sinensis) is often grown under a canopy of trees forming a distinctive agroforestry system covering an estimated area of 3.94 million ha of land globally. Although, tea is a major commercial crop in many countries in tropical and sub-tropical regions, including China, India and Sri Lanka, tea agroforestry systems (TAFS) have remained little studied for their role in carbon management and climate change adaptation/mitigation actions. We, therefore, undertook a detailed study on the storage of organic carbon in above- and below-ground vegetation and soil under age chronosequence of TAFS in North East India. The specific aim of this study was to quantify variations in soil physical and chemical properties, carbon storage in shade trees and tea bushes, and ecosystem carbon stocks under the chronosequence of TAFS. This study has established significant variations in soil properties and carbon storage in different aged TAFS. One of the salient findings is the decrease in soil bulk density and increase in water holding capacity with the age of TAFS in the 0–50 cm depth. The total vegetation C stock (shade trees + tea bushes + litter biomass) increased with increase in the age of TAFS, and the increase was as high as 25% in > 20 years compared to younger (< 10 years old) TAFS. The ecosystem C stock estimated at 162–187 Mg ha−1 was higher than many temperate and tropical agroforestry systems suggesting TAFS may effectively contribute to Clean Development Mechanisms CDM/REDD+ mechanisms of the United Nations Framework Convention on Climate Change (UNFCCC) once standard guidelines for market mechanisms are in place.