Death of Root Tissues in Standing [Live] and Felled Loblolly Pines
Recycling tree root components is important in sustaining the productivity of southern pine forests. Death of outer cortical tissues and mortality of short roots is ubiquitous in conifers. Affected tissues lose their starch grains and accumulate secondary products, such as tannins. In this study, 10-year-old loblolly pine trees were cut at the soil surface and sequential samples of roots were collected, fixed, embedded, and sectioned for light microscopy at monthly intervals. Observations showed roots of felled trees were similar to those of standing controls for approximately 5 months. Indicators of cell and tissue death were the disappearance of starch grains, increased tannin accumulation, and decreased staining of nuclei. This pattern of changes was remarkably similar to that of dying cortical cells. The long period (5 months) after felling and before the roots die probably has a significant effect on root microflora and the distribution of nutrients from the decomposition of surface woody debris and root systems.