Pervious and impervious pavement reduce production and decrease lifespan of fine roots of mature Sweetgum trees

Root zones of mature Sweetgum paved with either pervious or impervious concrete after 15–18 years of tree growth exhibited much reduced standing fine root length compared to unpaved plots 3 years after pavement installation. The objective of this paper was to determine whether these observed reductions in standing root length were due to reduced root production rates or due to enhanced root mortality rates in response to the presence of either pavement. We measured both fine root production and root death over a 15-month period using biweekly nondestructive observations of the root zones at four depths. In addition, we used proportional hazards analysis to determine how the presence of pavement affected chances of root mortality. We found that new root production was more negatively affected by the presence of either pavement than root mortality while chances of root mortality were increased by the presence of pavement, leading to much reduced standing net root length in paved plots at any given time. Surprisingly, even though root production and mortality were strongly altered by pavement, there was no significant effect on tree diameter growth. These results suggest that while Sweetgum root dynamics are negatively affected by pavement, there is enough plasticity within this species to adapt to altered root zone dynamics without affecting aboveground growth.