Shelterbelt species composition and age determine structure: consequences for ecosystem services

Shelterbelts are a popular form of agroforestry, providing a wide range of ecosystem services (e.g. wind speed reduction and wood production) which deliver farm-scale benefits. Variation in species composition and planting density drives structural differences in shelterbelts which directly influence the provision of ecosystem services and consequently the range of benefits received by farmers. Although specific structural characteristics of shelterbelts that determine provision of these services have been identified, little is known about how these characteristics vary with shelterbelt species composition and age, and how such variation may affect provision of a range of key services and benefits. This study explores the effects of shelterbelt composition and age on structural characteristics that determine ecosystem service provision. Structural characteristics (including vegetation height and porosity) were measured and compared across shelterbelts with three common species compositions (Eucalyptus nitens, Pinus radiata, mixed native) and three age classes (2–5 years, 6–14 years, 15–30 years) in the Midlands region of Tasmania, Australia. Species composition and age were key determinants of structural characteristics. For example, height, carbon sequestration, and stand basal area increased and porosity decreased with shelterbelt age, with rates of increase/decrease varying significantly between species compositions. We outlined how these structural characteristics affect provision of ecosystem services and showed that fine scale benefits are likely to be highly dependent on the species composition of the shelterbelt. These findings can assist agroforestry practitioners in designing shelterbelts that maximise benefits to their enterprise. There is value in expanding the approach used in this study to develop decision-making tools for practitioners, and to facilitate more meaningful application of natural capital accounting to agroforestry at the farm scale.