108 years of change in spatial pattern following selective harvest of a Pinus ponderosa stand in northern Arizona

Questions: How did an initial tree harvest in 1894 influence the spatial and temporal patterns of Pinus ponderosa recruitment? How do these patterns compare to our understanding of P. ponderosa stand dynamics prior to Euro-American settlement? How might spatial pattern information, particularly with respect to patch characteristics, inform current restoration and management practices? Location: A 2.59-ha permanent sample plot in the Fort Valley Experimental Forest, Flagstaff, Arizona. The plot was selectively harvested in 1894 and measured in 1909 and 2002. Methods: We used historical stem-map and ledger data, contemporary data, and dendrochronological techniques to reconstruct stand structure (tree size, age, location) in three scenarios: (1) unharvested (1909), (2) harvested (1909), and (3) contemporary (2002). We used Clark and Evans' R, Ripley's K(t) univariate analysis, and correlogram analysis to assess the spatial pattern in each scenario. We also used Ripley's K12(O bivariate analysis and tree age data to examine spatial and temporal recruitment patterns as observed in the contemporary scenario. Results and Conclusions: The unharvested stand was aggregated at scales up to 28 m. The selective harvest accentuated the spatial patchiness of the stand in 1909 and changed spatial patterns by homogenizing tree size within patches. By 2002, the stand was a single patch dominated by small trees. Postharvest recruitment patterns were not spatially random; Pinus seedlings initially established in natural grass openings and then proceeded to fill-in stump patches created by harvesting. Knowledge of spatial pattern should be explicitly incorporated into restoration activities in these forests.