Competition Effects on Growth and Crown Dimensions of Shortleaf and Loblolly Pine in Mature, Natural-Origin, Pine–Hardwood Mixtures of the Upper West Gulf Coastal Plain of Arkansas, USA: A Neighborhood Analysis

The need for a comprehensive and mechanistic understanding of competition has never been more important as plants adapt to changing environment forest management evolves focus on maintaining enhancing complexity. With the recent decline in shortleaf pine (Pinus echinata Mill.) land area, it is critical determine effects its performance against loblolly taeda L.), preferred planted replacement. We evaluate differences 10 year mean basal area increment (BAI) crown dimensions across gradient neighborhoods. Linear mixed-effects regression models were developed using BAI several metrics responses crowding, competitor species abundance identity, initial size identity focal tree predictors. Crowding trees negatively impacted (p < 0.001, respectively). Although had three times higher compared within similar neighborhoods, was variable, crowding effect did not differ between ranged from 0.51–0.99). Competitive impacts by 0.07–0.70). Distance-independent indices better explained variation horizontal metrics, while distance-dependent ratios effective at evaluating vertical metrics. These findings highlight competitive potential mature, natural-origin stands provide support restoration pine–hardwood hardwood–pine stratified mixtures well long rotations.