Overstory mortality and canopy disturbances in longleaf pine ecosystems
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Can. J. For. Res. Vol. 26 no. 1.:p. 2035-2047. (1996)
We studied longleaf pine (Pinus palustris Mill.) ecosystems to determine causes and rates of overstory mortality, size of canopy disturbances, and the effects of disturbance on canopy structure. Further, we used redundancy analysis to relate variation in characteristics of mortality across a landscape to site and stand variables. We analyzed mortality that occurred from 1990 to 1994 in 70 second-growth plots that spanned a range of site conditions and stand structures, and in five large disturbances that occurred outside the random sample of plots. Half of pine mortality over 5 years in the 70 plots was from unknown causes. Lightning was the primary identifiable cause of mortality, followed by suppression and wind. Lightning mortality was most frequent on xeric sites, while windthrow was common on wet-mesic sites. Suppression mortality was frequent on wet-mesic sites and in higher density stands. Five-year mortality rates averaged 2.3 trees/ha, or 1.9% of original density. Most mortality consisted of single trees. Large disturbances (mostly from lightning) of 15-30 trees were rare, occurring once per 1000 ha in 5 years. Variation in amount of mortality and size of disturbance were unrelated to soil or stand structural characteristics. Low mortality rates from small-scale disturbances result in slow canopy turnover. These results indicate that large openings sufficient for natural regeneration of longleaf pine develop slowly in the absence of hurricanes. Silvicultural options for longleaf pine can be designed to mimic the canopy structure that results from natural canopy disturbances, which leave many live trees standing. Such options may be desirable if a goal of silviculture is to increase structural complexity in stands managed for timber.
Keywordsmortality; canopy disturbances; longleaf pine; ecosystems; Lightning
Palik, Brian J.; Pederson, Neil. 1996. Overstory mortality and canopy disturbances in longleaf pine ecosystems. Can. J. For. Res. Vol. 26 no. 1.:p. 2035-2047. (1996)