Impacts of heartwood decay on radial growth of Abies georgei var. smithii in Sygera Mountains, China.

Tree heart rot is widespread in forests, which could affect forest health and bring uncertainties in the estimation of forest carbon sequestration. However, the impacts of heart rot on radial growth of trees are not well understood. Tree-ring data from heart-rotted and healthy trees of Abies georgei var. smithii at altitudes of 3700 m (low-altitude), 4000 m (mid-altitude), and 4300 m (high-altitude) in the Sygera Mountain region of southeastern Xizang were used to compare radial growth and its relationship with climatic factors. The results showed that the positive effect of rapid warming on the radial growth of heart-rotted A. georgei var. smithii in mid- and high-altitude regions was lower than that of healthy trees, while the negative effect on the growth of low-altitude heart-rotted trees was higher than that on healthy trees. In both periods before and after warming, the radial growth rates of heart-rotted trees at all three altitudes were significantly lower than those of healthy ones. With the occurrence of heart rot, the effect of temperature on the radial growth of low-altitude A. georgei var. smithii shifted from promotion to some degree of inhibition. The sensitivity of heart-rotted trees in mid-altitude regions to temperature factors during the previous year's growing season was lower than that of healthy trees, while the sensitivity of heart-rotted trees in the treeline area to temperature was only slightly different from that of healthy trees. Under the background of future climate warming, warming would promote the radial growth of A. georgei var. smithii in the region, and exacerbate the differences in growth rates between heart-rotted and healthy trees.