Dendroecological investigation of red-cockaded woodpecker cavity tree selection in endangered longleaf pine forests

Abstract

Old-growth longleaf pine (Pinus palustris) is a keystone/foundation species for 29 threatened or endangered species in the Coastal Plain of the southeastern United States. The endangered red-cockaded woodpecker (Dryobates borealis; RCW) and endangered longleaf pine have an established ecological association. Here, we explore differences in climate/growth response and radial growth disturbance events in trees with RCW cavities compared to non-cavity trees in the Sandhills Gameland Reserve in North Carolina, USA. Using standard dendrochronological techniques, we collected and analyzed core samples from trees selected by RCW for their cavities (RCWC) and adjacent control trees (RCWCo) that had no visible cavity. We developed RCWC and RCWCo tree-ring chronologies that allowed us to examine if climate vulnerability is a component of the RCW selection process for their nests. Specifically, we investigated climate/growth responses, radial growth suppressions, and physical characteristics of both tree types through a comparison of tree age, latewood radial growth measurements, and number of resin ducts. For long-term climate response (1910-2018), we found no significant differences between RCWC and RCWCo trees. However, we identified temporal differences in climate/growth relationships between RCWC and RCWCo as well as significant differences in the number of suppression events and spatially-grouped suppression events. For tree physiology, we found more resin ducts during 1950-2018 in RCWC trees. Our dendroecological-based investigation examines multiple factors in addressing the question of why RCWs select specific longleaf pine trees for cavities, which may help improve conservation efforts for RCW and longleaf pine.

The University of West Florida Campus Ecosystem Study: age-diameter and growth relationships of longleaf pine using hurricane-induced windthrows

“…Using tree-ring data from sites in North and South Carolina, Patterson and Knapp (2016) found that masting was related both to radial growth and, in unthinned stands, PDSI. Kaiser et al (2020) applied tree core/climate relationships toward understanding the selection of longleaf stems as cavity trees by the endangered red-cockaded woodpecker (Dryobates borealis Vieillot), endemic to longleaf pine ecosystems. Differentiating between types of radial growth (i.e., earlywood, latewood), Soulé et al (2021) sampled longleaf stands in the Coastal Plain of the Carolinas and concluded that radial growth is primarily driven by late summer moisture availability.…”

The Longleaf Tree-Ring Network: Reviewing and expanding the utility ofPinus palustrisMill. Dendrochronological data

“…Scores of federally protected species inhabit longleaf pine ecosystems (Walker, 1993; Zion et al, 2019). Notably, certain longleaf pine habitats—based on, for example, tree density, size, age, structure, and ground cover—act as optimal niche gestalts by allowing the endangered Red-cockaded Woodpecker ( Picoides borealis Vieillot) to not only persist, but to thrive (Jackson, 1994; Engstrom and Sanders, 1997; Conner et al, 2001; James et al, 2001; Shaw and Long, 2007; Kaiser et al, 2020).…”