Richard Murray, DC-area arborist and author of “Tree Biology Notebook,” points out the problems humans cause for tree species, such as White Oak (Quercus alba), that are dependent on mycorrhizae (composite organs of fungi and nonwoody roots). Mycorrhizae, which aid the tree in absorbing water and mineral nutrients, are concentrated in the upper soil layers and tend to spread outward and form thick mats. They are sensitive and easily disturbed, causing potentially serious problems for the tree. The tree depends on the decomposition of annually shed leaves and the diversity of living, dying, and dead organic matter in the soil. Cultural practices such as the removal of fallen leaves, planting of grass, and fertilizing and irrigating reduce mycorrhizae and the biological diversity of the soil.
Thanks Drew. That's why we were careful not to rake away leaves from around the buildings and beds when we were cleaning up. We did pick up lots of sticks and garden "rubbish." I think our managed landscape here at St. Bartholomew's is meant to serve a number of purposes - complement our buildings, be pleasing to the eye, and serve the local ecology. Balance is everything in a managed landscape.
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