Succession, climate and neighbourhood dynamics influence tree growth over time: an 87‐year record of change in a Pinus resinosa ‐dominated forest, Minnesota, USA

Resource availability and its influence on tree-to-tree interactions are expected to change over the course of forest stand development, but the rarity of long-term datasets has limited examinations of neighborhood crowding over extended time periods. How do a history of neighborhood interactions and population-level dynamics, including demographic transition, impact long-term tree growth? Methods. Using a spatially explicit dataset of repeated diameter measurements recorded over an 87-year period, we modeled the influence of tree-to-tree interactions on growth as it varied over time. We also applied maximum likelihood estimation and simulated annealing to examine how inter- and intra- specific competition and the relative importance of neighbor size and distance varied over time and with different climatic conditions. Results. Crowding had a consistent, negative influence on growth, but crowding intensity and importance were dynamic over time and differed between trees that survived the entire study period compared to those that ultimately died. The scaling of neighbor diameter, neighbor distance, and neighbor species (inter- vs. intra-specific competition) also varied as demographic transition occurred and longer-lived species assumed greater dominance. Conclusions. Given observed relationships with moisture stress (based on precipitation: potential evapotranspiration) and maximum temperature, crowding intensity and importance may increase if temperatures rise in the future and water becomes more limiting. Long-term datasets, such as the record examined in this study, have immense value for testing assumptions about stand dynamics, particularly as forests respond to projected shifts in climate and disturbance regimes.