Intraspecific Dominance Determines Subseasonal Pinus ponderosa Growth Response to Warm-Season Precipitation Amid Drought in Southern Nevada, USA

Abstract

Pinus ponderosa is a widespread conifer species across western North America, yet its intraspecific variability in drought response remains understudied, particularly at subseasonal time scales. We investigated how intraspecific tree dominance influences physiological and anatomical growth responses to warm-season precipitation pulses in a semi-arid montane forest in southern Nevada, USA. Using high-resolution dendrochronology, quantitative wood anatomy and dual-isotope (δ¹⁸O, δ¹³C) analysis of tree-ring cellulose, we compared dominant (old-growth) and codominant (mature) trees during two growing seasons: one impacted by a remnant tropical storm that provided an uncharacteristic pulse of precipitation to southern Nevada during the monsoon season (2015) and one with drier conditions with little monsoonal precipitation (2016). Codominant trees exhibited stronger and more immediate growth responses to warm-season precipitation, characterized by increased tracheid production and cellulose δ¹⁸O values that matched those of warm-season precipitation δ¹⁸O values, indicating shallow soil water use. In contrast, dominant trees relied more on deeper soil moisture and showed more conservative growth strategies. These divergent strategies suggest that intraspecific dominance mediates access to water and controls the sensitivity of growth to seasonal precipitation variability, highlighting the importance of intraspecific variation in shaping forest resilience and climate adaptation strategies under increasing drought and climate extremes.