Field-based research on the impact poplar trees have on understorey pasture production has predominately been conducted around young and undeveloped material up to 8 years or mature trees greater than 25 years old. Tree stocking rates with regards to pasture production have also been predominately based around agroforestry blocks and stands in which stocking rates far exceed that employed in poplar plantings for erosion control e.g. 250 stems per hectare (sph) c.f. 25-50 sph. This lack of information is a major hindrance to farmers adopting tree planting programmes when considering sustainable land management options, although it has been widely argued the costs and benefits to integrating and managing space planted poplars favours having conservation trees.
The main objective of this dissertation is to provide the farming community with reliable and applicable information on the effects on pasture production surrounding poplar-pasture systems within a hill country setting. The experiment reported in this dissertation was to determine the impact space-planted poplars of different ages have on the understorey pasture growth compared with open pasture. Possible causes for the change in pasture production levels could be the proportion of light transmission through the canopy cover as well as soil moisture and the physical and chemical characteristics of the soil as the poplar trees increase in age. The leading study research question is an investigation of space-planted Populus×euramericana ’Veronese’ trees for predicting influences of tree size and shading on understorey pasture production.