The longevity of large pine snags in eastern Texas

Abstract

Habitat for cavity-nesting wildlife is closely tied to the availability of standing dead trees (snags). Large snags (>40 cm dbh) are particularly important because they provide cavity-excavation substrate for both large and small cavity excavators. Historically in the southern United States, common belief has been that the utility of pine (Pinus spp.) snags for cavity nesters occurs for only a short period of time after tree death because pine snags quickly decay and fall to the ground. We studied the deterioration rate and ultimate falling of large pine snags in eastern Texas over a 20-year period (1983–2003). Coinciding with our annual checks of red-cockaded woodpecker (Picoides borealis) cavity-tree clusters, we checked the status and height of all red-cockaded woodpecker cavity trees that died. We determined the cause of death and tree species of 136 cavity tree snags (=25.4 m at death) and monitored their height annually until they were <1 m in height. Five years after tree death, 92 snags (67.6%) were still standing and averaged 13.9 m in height. Ten years after tree death, 21 snags (15.4%) were still standing and averaged 10.0 m in height. After 15 years 4 snags (2.9%) averaging 5.3 m in height still remained standing. Two snags (1.5%), averaging 2.7 m in height, survived through 19 years but had fallen by the end of the twentieth year. Pines dying from wind snap at mid-bole survived longer as snags (=9.7 years) than pines killed by bark-beetles (Dendroctonus spp.) (=5.9 years). Longleaf pine (Pinus palustris) snags remained standing longer (=8.0 years) than loblolly pine (P. taeda) snags (=6.0 years) (P < 0.05), but not longer (P>0.05) than shortleaf pine (P. echinata) snags (=6.6 years).