The Carbon Footprint of Cherry and Apple Orchards in Michigan: An Allometric Study to Support Early Development of a Carbon Sequestration Model

Currently the apple and cherry industries have been approached by the Delta Institute (http://delta-institute.org) to consider if these commodities might be interested in trading carbon credits on the CCX®. However, carbon sequestration figures do not exist for Michigan orchards, and would be at best estimates. A realistic estimate for these parameters is needed. Although the carbon footprint in an orchard accounts for alleys, weeds and soil management and fuel consumptions we are currently focusing on defining the carbon budget for apple and cherry trees. The model for apple carbon balance developed by Lakso et al. (2001) was adapted to Michigan climatic conditions to estimate the yearly carbon sequestration in standing biomass of apple orchards. The model component regarding assimilation rates was also modified to predict the seasonal photosynthesis and dry matter production for cherry. To validate the predictions for cherry, a dry matter study was conducted during the fall 2009. We measured the total biomass in the perennial structures of cherry trees excavated from two differently aged orchards (9 and 20 years). Trunk diameter was measured for each tree. Fresh weight of roots, trunks and branches was recorded in the field after the excavation. Subsamples were collected, weighted and dried to constant weight at 60 °C. In the 20 years old cherry trees study, several branches per tree were also subdivided according to the year of growth (2009, ‘08, ‘07 and older) and wood was weighted separately. The dry matter percentage in the wood of different years was not significantly different (mean = 62%). A regression analysis was performed on the data collected, correlating trunk circumference to root, trunk and branches dry weights. Slopes of the regressions from the two groups of trees used were not significantly different. The total aboveground biomass followed the regression equation (R²=0.92): y = 2.07x - 51.33 where x= trunk circumference (cm) and y= aboveground dry biomass (kg). According to this study cherry orchards are able to sequester 0.48 tons of carbon per acre (considering 55% of carbon in dry wood). The model predicted 0.62 tons/acre for cherry and 0.59 tons/acre for apple. We are currently validating the percentage of carbon in dry wood. Although both the approaches support a positive carbon balance for apple and cherry production, we are planning to conduct a dry matter study in apple, and we are currently working on the further improvement of the cherry carbon model.