NITROGEN CAN LIMIT OVERSTORY TREE GROWTH FOLLOWING EXTREME STAND DENSITY INCREASE IN A PONDEROSA PINE FOREST
AffiliationUniv Arizona, Sch Nat Resources & Environm
Univ Arizona, Lab Tree Ring Res
stable carbon isotopes
MetadataShow full item record
CitationL.A. Marshall, Donald A. Falk, and Nate G. Mcdowell "NITROGEN CAN LIMIT OVERSTORY TREE GROWTH FOLLOWING EXTREME STAND DENSITY INCREASE IN A PONDEROSA PINE FOREST," Tree-Ring Research 75(1), 49-60, (1 March 2019). https://doi.org/10.3959/1536-1098-75.1.49
JournalTREE RING RESEARCH
RightsCopyright © 2019 by the Tree-Ring Society
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at email@example.com.
AbstractExtreme stand density increases have occurred in ponderosa pine forests throughout the western U.S. since the early 20th Century, with adverse implications for growth, physiological functioning, and mortality risk. Identifying primary stressors on large, old overstory trees in dense forests can informmanagement decisions to promote resilience and survival. We tested the impact of stand density increase on overstory tree-ring growth, and the relative influence of water and nitrogen, in an old-growth ponderosa pine forest in northern New Mexico subject to variable density increase. We measured annual tree-ring growth and carbon discrimination in trees before stand density increased, in a climatically-similar period post-density increase, and in recent transition to drought. We expected density-driven water stress to drive reduced tree-ring growth in overstory trees in dense stands. We found reduced growth and higher mortality in dense stands, but nitrogen rather than water constrained growth, as determined by carbon isotope discrimination in tree rings, leaf nitrogen concentration, and soil nitrogen supply. In dense stands, less available nitrogen limited photosynthetic rate, leading to reduced assimilation of intracellular C-13 and higher discrimination with low tree-ring growth and a reduced relationship with climate. This unexpected result illustrates that a variety of limiting factors can influence forest dynamics, as density-driven nitrogen limitation interacts with water stress to influence tree growth and physiological functioning.
VersionFinal accepted manuscript
SponsorsUS Forest Service, Collaborative Forest Restoration Program (CFRP); US Forest Service, Rocky Mountain Research Station [02-DG-11031000-001, 00-JV-11221615]; Joint Fire Science Program [99-1-3-08]; New Mexico Forest and Woodlands Restoration Institute; US Department of Energy Global Change Education Program; Department of Energy-Office of Biological and Environmental Research