Carbon cycling and balance in a traditional cardamom based agroforestry system of Sikkim Himalayas

Abstract

The pattern of carbon cycling dynamics in a 20 year old traditional cardamom agroforestry system located at Sikkim Himalaya was studied for two years to understand the dynamics of different carbon pools and carbon emission patterns in the system. Total biomass (aboveground + belowground) and carbon in trees were 81.91 ± 9.04 Mg ha−1 and 38.47 ± 4.25 Mg C ha−1, respectively and contributed 27% of the total ecosystem carbon. Herbs and detritus carbon were 2.34 ± 0.24 Mg C ha−1 and 3.64 ± 0.20 Mg C ha−1 respectively while cumulative soil organic carbon (SOC) stock ranged from 89.90 ± 2.16 (January) to 117.91 ± 3.12 Mg C ha−1(August) in the 0–45 cm soil layer. Seasonal microbial biomass carbon (MBC) stock varied from 501.34 to 857.77 µg g−1 while annual CO2 emission (SR) ranged from 112.11–219.29 mg CO2 m−2 h−1. SOC, MBC and SR exhibited strong seasonality with a peak value in rainy and least in the winter season. Carbon density of trees exhibited a positive and significant relation with tree density (P < 0.05), basal area (P < 0.01) and aboveground biomass (P < 0.01). All the abiotic variables with the exception of bulk density and soil pH showed strong positive and significant relationship with SOC, MBC and SR. Total carbon sequestration of 11.91 Mg C ha−1 year−1 and release of 3.46 Mg C ha−1year−1 resulting to a net ecosystem carbon balance of 8.45 Mg C ha−1 year−1 by a traditional agroforestry system suggests that besides provision of livelihood opportunities it can be used as an adaptation strategy in agricultural systems for mitigation of climate change.