Early Survival and Growth of Polylepis racemosa Ruiz & Pav. Under Contrasting Island-Guano Doses in a High-Andean Grassland

High-Andean environments impose severe limitations on tree establishment, making early survival and growth decisive for restoration success. This study evaluated differences associated with four island-guano doses—0, 150, 300, and 450 g plant−1—applied in separate treatment strips to Polylepis racemosa established in a grassland at 4239 m a.s.l. A monitored cohort of 148 plants, with 37 individuals per treatment strip, was assessed at establishment and after 4, 8, and 12 months. Survival, interval mortality, total height, basal diameter, cumulative increments, and relative growth rates were analyzed using longitudinal mixed models. All plants survived during the first four months, but survival declined afterward. At 12 months, survival reached 29.7% in the control strip and 45.9%, 43.2%, and 37.8% in the strips receiving 150, 300, and 450 g plant−1, respectively. The strongest height and basal-diameter responses occurred in the 300 and 450 g plant−1 strips. The highest-dose strip showed the greatest final height, basal diameter, and cumulative growth increments, whereas the highest relative growth rates under the larger doses occurred mainly during the first four months. The 150 g plant−1 strip showed slower structural development but the highest final survival. These results indicate a non-linear pattern associated with island-guano dose, as the strip showing the greatest growth did not show the highest persistence. Considering final survival together with structural growth, the 300 g plant−1 strip showed the most balanced pattern within the evaluated plantation. This interpretation does not identify a generally optimal dose, and replicated, longer-term trials are required before broader recommendations can be made.