Site Index for Plantations of Two Species of <i>Pinus</i> in Michoacán, Mexico

In silvicultural management, it is essential to classify forest plantations (FPs) according to productivity. The objectives were to fit models of dominant height growth ( Dh ) with mixed effects and to construct curves with different site index (SI) classes for plantations of Pinus pseudostrobus and Pinus montezumae in Nuevo San Juan Parangaricutiro, Michoacán, Mexico. In this context, 34 FPs of Pinus pseudostrobus (7–37 years) and 16 FPs of Pinus montezumae (7–32 years) were evaluated through systematic sampling (206 quadrangular sites of 400 m 2 ) and selection of the six top trees in Dh . The age (A) of each plantation was defined and the altitude (Alt), aspect (Asp), and slope (Slop) were recorded. The modified Hossfeld I model showed polymorphic growth trends in Dh at SI of 9, 14, 18, 23, and 28 m for Pinus pseudostrobus at a base age ( A 0 ) of 20 years, and anamorphic for Pinus montezumae at SI of 10, 14, 18, 22, and 26 m with A 0 of 25 years. The Alt‐Slop and Alt‐Asp combined, explains better the Dh . On average, a technical shift in height and age of maximum current increment was observed for Pinus pseudostrobus of 13 years and 6 years, respectively, whereas, for Pinus montezumae , it is 6 years and 3 years. The fitting using mixed‐effects modeling (MEM) eliminates the random variability in Dh caused by site conditions and reduces the estimation deviations by improving the statistical fitting. This research is partof the first author′s doctoral thesis (Hernandez‐Ramos, 2023).