Short-rotation willow (Salix sp.) is a compelling candidate for a second-generation biofuel in New York State. This crop can be grown on marginal agricultural lands and has been shown to have a low net energy ratio (the energy output divided by the fossil fuel inputs). Due to these low carbon dioxide emissions, there has been considerable interest in willow as not only an economic option for marginal cropland, but as a tool for climate mitigation. However, studies of willow must take into account not only inputs and outputs of greenhouse gases, but also the biogeophysical impacts of land use change. Small differences in surface reflectance, or albedo, across different crops and covers can scale up to significant impacts on the global energy budget. Here, we present the first data on willow albedo from three years of research across seasons and stand ages with the objective of identifying the climate impact of cropped willow biofuels in New York State.
Results/Conclusions
Summer albedo was found to be 0.20 ± SE 0.030. In comparison, summer albedo of a deciduous forest, had an albedo of 0.16 ± 0.011. Meadow, which reflects the status of many mowed or hayed marginal land in New York State, had an albedo of 0.19 ± 0.0024. Other candidate biofuels, Panicum and Miscanthus, had higher summer albedo at 0.24 ± 0.0035 and 0.23 ± 0.0027 respectively. Winter albedo for willow was 0.32 ± 0.11 with snow on the ground and 0.14 ± 0.022 without it. Overall winter albedo (at latitude 43) was 0.22 ± 0.06. Snow vs snow-free albedo was not available for the other cover types, but overall winter albedo was 0.24 ± 0.015 for a deciduous forest (latitude 54), 0.33 ± 0.033 for meadow (latitude 52), 0.31 ± 0.017 for Panicum (latitude 39), and 0.30 ± 0.015 for Miscanthus (latitude 39). Our results show that over the course of the year, willow is more reflective than might have been expected based on deciduous forests. Transition from marginal croplands currently hayed or mowed will not lead to a major impact on albedo climate forcing. However, willow is less reflective than other candidate second-generation biofuels, such as Panicum and Miscanthus. Continuing work quantifies this effect for willow suitable habitat within New York State.