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Using satellite image data to estimate aboveground shelterbelt carbon stocks across an agricultural landscape
- Czerepowicz, L., Case, B.S., Doscher, C.
- Agriculture, ecosystems & environment 2012 v.156 pp. 142-150
- aboveground biomass, agroforestry, carbon, carbon sequestration, carbon sinks, computer software, conifers, ecosystem services, equations, grasslands, image analysis, landscapes, models, regression analysis, satellites, shelterbelts, trees, variance, New Zealand
- Shelterbelts are prominent features of agroforestry systems that provide a range of ecosystem services, including the sequestration of carbon (C). However, shelterbelts are not easily characterized in a spatially explicit manner, and carbon accounting methods for shelterbelts are lacking. A study was conducted for a 48kmÂ² agricultural area on the Canterbury Plains, New Zealand, to investigate an approach that uses remotely sensed data to provide a good first-approximation of aboveground biomass (AGB) and C quantities in coniferous shelterbelts on an area basis. First, shelterbelts were delineated for a pan-sharpened QuickBird II image (0.6m resolution) using Feature Analyst, a feature extraction software. This method correctly extracted 73% of conifer shelterbelt area across the image, and estimated that these shelterbelts comprised 2.5% of the study area. Second, AGB was estimated for trees in 96 field-sampled conifer shelterbelts using a published allometric equation and then scaled up to obtain total shelterbelt AGB estimates. Third, a regression model was developed for predicting shelterbelt AGB based on spatial and spectral attributes extracted for field-sampled shelterbelts. This model explained 71% of the variance in shelterbelt AGB based on two significant predictors: shelterbelt area and red band mean. Lastly, this model was then applied to shelterbelts identified with Feature Analyst to produce a map of estimated shelterbelt C density across the study area. Results suggest that conifer shelterbelts represent a small, yet significant carbon reservoir on the Canterbury Plains, sequestering on average 237Â±77tChaâ»Â¹ of shelterbelt. As such, conifer shelterbelts contribute up to an additional 6tChaâ»Â¹ to the âgrassland with woody biomassâ carbon pool in New Zealand, which is currently estimated at 29thaâ»Â¹. With improvements, these methods have the potential to be used to quantify shelterbelt carbon across New Zealand and other countries with significant shelterbelt resources.