Depth distribution of cherry (Prunus avium L.) tree roots as influenced bygrass root competition

We investigated the effect of competition from grass roots (as controlled b y herbicide application) on the depth distribution of white roots in cherry trees, grown with varying rates and frequency of application of N in an ag roforestry system. Statistical summaries of distribution, namely mean and s kewness, produced a concise and interpretable analysis of the data. There was a large increase in tree root numbers in the surface horizons aft er the herbicide had reduced grass root competition. Where the surrounding grass had not been reduced by herbicide, the average depth of tree roots in creased with time, contrasting with a marked shift in the mode of distribut ion of root numbers to shallow depths when grass competition was removed. T hese findings are important in the understanding of plant root competition and for prescribing best practise for tree establishment in agroforestry sy stems.