Estimating biomass production and carbon sequestration of poplar-based agroforestry systems in India

This study was conducted on 79 harvested poplar trees of eight-years-old planted at five spacing geometries (5 x 4 m, 10 x 2 m, 18 x 2 x 2 m, North-South and East-West boundary) to construct component-wise dry biomass (above + below ground) equations for estimating biomass & carbon sequestered. The complete data were randomly divided into two mutually exclusive and independent sets viz estimation-set (80%) to fit the model and validation-set (20%) to ascertain accuracy of the fitted model. DBH was found to be the most appropriate independent variate to construct best-fit biomass equations with growth attributes. Among various attempted functions (linear, allometric, logistic, Gompertz, Chapman and exponential), allometric function i.e., Total Biomass = 0.2575*DBH(2.191) (R-Adj(2) = 0.97, RMS = 925.71 and AIC = 427.87) was found to be the best-fit. The total dry biomass production of poplar varied from 69.90 to 207.98 Mg ha(-1) in aboveground and 13.46 to 36.69 Mg ha(-1) in belowground in five planting geometries. Total carbon storage (above + below ground) under various spacings viz 5 x 4 m, 10 x 2 m, 18 x 2 x 2 m, North-South and East-West boundary poplar were 112.48, 101.80, 84.87, 77.28 and 38.84 Mg C ha(-1), respectively. The carbon sequestration rate was observed to be higher in 5 x 4 m (14.09 Mg C ha(-1) yr(-1)) closely followed by 10 x 2 m (12.61 Mg C ha(-1) yr(-1)), 18 x 2 x 2 m (10.50 Mg C ha(-1) yr(-1)),E-West (9.56 Mg C ha(-1) yr(-1)) and North-South plantation (4.80 Mg C ha(-1) yr(-1)). Keeping in view, regionally derived allometric equations contribute to limiting the uncertainty in the estimation of biomass and carbon sequestration, which may be helpful to monitoring, reporting and verification (MRV) needs in carbon management policies.

Automated summary

This study investigated poplar trees planted at different spacing geometries and constructed component-wise dry biomass equations to estimate biomass and carbon sequestration. The results showed that diameter at breast height (DBH) was the most suitable independent variable for constructing the best-fit biomass equations. The total dry biomass and carbon storage varied among different planting geometries, with the highest carbon sequestration rate observed in the 5 x 4 m spacing.